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|
- /* GNU/Linux native-dependent code common to multiple platforms.
- Copyright (C) 2001-2022 Free Software Foundation, Inc.
- This file is part of GDB.
- This program is free software; you can redistribute it and/or modify
- it under the terms of the GNU General Public License as published by
- the Free Software Foundation; either version 3 of the License, or
- (at your option) any later version.
- This program is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- GNU General Public License for more details.
- You should have received a copy of the GNU General Public License
- along with this program. If not, see <http://www.gnu.org/licenses/>. */
- #include "defs.h"
- #include "inferior.h"
- #include "infrun.h"
- #include "target.h"
- #include "nat/linux-nat.h"
- #include "nat/linux-waitpid.h"
- #include "gdbsupport/gdb_wait.h"
- #include <unistd.h>
- #include <sys/syscall.h>
- #include "nat/gdb_ptrace.h"
- #include "linux-nat.h"
- #include "nat/linux-ptrace.h"
- #include "nat/linux-procfs.h"
- #include "nat/linux-personality.h"
- #include "linux-fork.h"
- #include "gdbthread.h"
- #include "gdbcmd.h"
- #include "regcache.h"
- #include "regset.h"
- #include "inf-child.h"
- #include "inf-ptrace.h"
- #include "auxv.h"
- #include <sys/procfs.h> /* for elf_gregset etc. */
- #include "elf-bfd.h" /* for elfcore_write_* */
- #include "gregset.h" /* for gregset */
- #include "gdbcore.h" /* for get_exec_file */
- #include <ctype.h> /* for isdigit */
- #include <sys/stat.h> /* for struct stat */
- #include <fcntl.h> /* for O_RDONLY */
- #include "inf-loop.h"
- #include "gdbsupport/event-loop.h"
- #include "event-top.h"
- #include <pwd.h>
- #include <sys/types.h>
- #include <dirent.h>
- #include "xml-support.h"
- #include <sys/vfs.h>
- #include "solib.h"
- #include "nat/linux-osdata.h"
- #include "linux-tdep.h"
- #include "symfile.h"
- #include "gdbsupport/agent.h"
- #include "tracepoint.h"
- #include "gdbsupport/buffer.h"
- #include "target-descriptions.h"
- #include "gdbsupport/filestuff.h"
- #include "objfiles.h"
- #include "nat/linux-namespaces.h"
- #include "gdbsupport/block-signals.h"
- #include "gdbsupport/fileio.h"
- #include "gdbsupport/scope-exit.h"
- #include "gdbsupport/gdb-sigmask.h"
- #include "gdbsupport/common-debug.h"
- #include <unordered_map>
- /* This comment documents high-level logic of this file.
- Waiting for events in sync mode
- ===============================
- When waiting for an event in a specific thread, we just use waitpid,
- passing the specific pid, and not passing WNOHANG.
- When waiting for an event in all threads, waitpid is not quite good:
- - If the thread group leader exits while other threads in the thread
- group still exist, waitpid(TGID, ...) hangs. That waitpid won't
- return an exit status until the other threads in the group are
- reaped.
- - When a non-leader thread execs, that thread just vanishes without
- reporting an exit (so we'd hang if we waited for it explicitly in
- that case). The exec event is instead reported to the TGID pid.
- The solution is to always use -1 and WNOHANG, together with
- sigsuspend.
- First, we use non-blocking waitpid to check for events. If nothing is
- found, we use sigsuspend to wait for SIGCHLD. When SIGCHLD arrives,
- it means something happened to a child process. As soon as we know
- there's an event, we get back to calling nonblocking waitpid.
- Note that SIGCHLD should be blocked between waitpid and sigsuspend
- calls, so that we don't miss a signal. If SIGCHLD arrives in between,
- when it's blocked, the signal becomes pending and sigsuspend
- immediately notices it and returns.
- Waiting for events in async mode (TARGET_WNOHANG)
- =================================================
- In async mode, GDB should always be ready to handle both user input
- and target events, so neither blocking waitpid nor sigsuspend are
- viable options. Instead, we should asynchronously notify the GDB main
- event loop whenever there's an unprocessed event from the target. We
- detect asynchronous target events by handling SIGCHLD signals. To
- notify the event loop about target events, an event pipe is used
- --- the pipe is registered as waitable event source in the event loop,
- the event loop select/poll's on the read end of this pipe (as well on
- other event sources, e.g., stdin), and the SIGCHLD handler marks the
- event pipe to raise an event. This is more portable than relying on
- pselect/ppoll, since on kernels that lack those syscalls, libc
- emulates them with select/poll+sigprocmask, and that is racy
- (a.k.a. plain broken).
- Obviously, if we fail to notify the event loop if there's a target
- event, it's bad. OTOH, if we notify the event loop when there's no
- event from the target, linux_nat_wait will detect that there's no real
- event to report, and return event of type TARGET_WAITKIND_IGNORE.
- This is mostly harmless, but it will waste time and is better avoided.
- The main design point is that every time GDB is outside linux-nat.c,
- we have a SIGCHLD handler installed that is called when something
- happens to the target and notifies the GDB event loop. Whenever GDB
- core decides to handle the event, and calls into linux-nat.c, we
- process things as in sync mode, except that the we never block in
- sigsuspend.
- While processing an event, we may end up momentarily blocked in
- waitpid calls. Those waitpid calls, while blocking, are guarantied to
- return quickly. E.g., in all-stop mode, before reporting to the core
- that an LWP hit a breakpoint, all LWPs are stopped by sending them
- SIGSTOP, and synchronously waiting for the SIGSTOP to be reported.
- Note that this is different from blocking indefinitely waiting for the
- next event --- here, we're already handling an event.
- Use of signals
- ==============
- We stop threads by sending a SIGSTOP. The use of SIGSTOP instead of another
- signal is not entirely significant; we just need for a signal to be delivered,
- so that we can intercept it. SIGSTOP's advantage is that it can not be
- blocked. A disadvantage is that it is not a real-time signal, so it can only
- be queued once; we do not keep track of other sources of SIGSTOP.
- Two other signals that can't be blocked are SIGCONT and SIGKILL. But we can't
- use them, because they have special behavior when the signal is generated -
- not when it is delivered. SIGCONT resumes the entire thread group and SIGKILL
- kills the entire thread group.
- A delivered SIGSTOP would stop the entire thread group, not just the thread we
- tkill'd. But we never let the SIGSTOP be delivered; we always intercept and
- cancel it (by PTRACE_CONT without passing SIGSTOP).
- We could use a real-time signal instead. This would solve those problems; we
- could use PTRACE_GETSIGINFO to locate the specific stop signals sent by GDB.
- But we would still have to have some support for SIGSTOP, since PTRACE_ATTACH
- generates it, and there are races with trying to find a signal that is not
- blocked.
- Exec events
- ===========
- The case of a thread group (process) with 3 or more threads, and a
- thread other than the leader execs is worth detailing:
- On an exec, the Linux kernel destroys all threads except the execing
- one in the thread group, and resets the execing thread's tid to the
- tgid. No exit notification is sent for the execing thread -- from the
- ptracer's perspective, it appears as though the execing thread just
- vanishes. Until we reap all other threads except the leader and the
- execing thread, the leader will be zombie, and the execing thread will
- be in `D (disc sleep)' state. As soon as all other threads are
- reaped, the execing thread changes its tid to the tgid, and the
- previous (zombie) leader vanishes, giving place to the "new"
- leader. */
- #ifndef O_LARGEFILE
- #define O_LARGEFILE 0
- #endif
- struct linux_nat_target *linux_target;
- /* Does the current host support PTRACE_GETREGSET? */
- enum tribool have_ptrace_getregset = TRIBOOL_UNKNOWN;
- /* When true, print debug messages relating to the linux native target. */
- static bool debug_linux_nat;
- /* Implement 'show debug linux-nat'. */
- static void
- show_debug_linux_nat (struct ui_file *file, int from_tty,
- struct cmd_list_element *c, const char *value)
- {
- gdb_printf (file, _("Debugging of GNU/Linux native targets is %s.\n"),
- value);
- }
- /* Print a linux-nat debug statement. */
- #define linux_nat_debug_printf(fmt, ...) \
- debug_prefixed_printf_cond (debug_linux_nat, "linux-nat", fmt, ##__VA_ARGS__)
- /* Print "linux-nat" enter/exit debug statements. */
- #define LINUX_NAT_SCOPED_DEBUG_ENTER_EXIT \
- scoped_debug_enter_exit (debug_linux_nat, "linux-nat")
- struct simple_pid_list
- {
- int pid;
- int status;
- struct simple_pid_list *next;
- };
- static struct simple_pid_list *stopped_pids;
- /* Whether target_thread_events is in effect. */
- static int report_thread_events;
- static int kill_lwp (int lwpid, int signo);
- static int stop_callback (struct lwp_info *lp);
- static void block_child_signals (sigset_t *prev_mask);
- static void restore_child_signals_mask (sigset_t *prev_mask);
- struct lwp_info;
- static struct lwp_info *add_lwp (ptid_t ptid);
- static void purge_lwp_list (int pid);
- static void delete_lwp (ptid_t ptid);
- static struct lwp_info *find_lwp_pid (ptid_t ptid);
- static int lwp_status_pending_p (struct lwp_info *lp);
- static void save_stop_reason (struct lwp_info *lp);
- static void close_proc_mem_file (pid_t pid);
- static void open_proc_mem_file (ptid_t ptid);
- /* Return TRUE if LWP is the leader thread of the process. */
- static bool
- is_leader (lwp_info *lp)
- {
- return lp->ptid.pid () == lp->ptid.lwp ();
- }
- /* LWP accessors. */
- /* See nat/linux-nat.h. */
- ptid_t
- ptid_of_lwp (struct lwp_info *lwp)
- {
- return lwp->ptid;
- }
- /* See nat/linux-nat.h. */
- void
- lwp_set_arch_private_info (struct lwp_info *lwp,
- struct arch_lwp_info *info)
- {
- lwp->arch_private = info;
- }
- /* See nat/linux-nat.h. */
- struct arch_lwp_info *
- lwp_arch_private_info (struct lwp_info *lwp)
- {
- return lwp->arch_private;
- }
- /* See nat/linux-nat.h. */
- int
- lwp_is_stopped (struct lwp_info *lwp)
- {
- return lwp->stopped;
- }
- /* See nat/linux-nat.h. */
- enum target_stop_reason
- lwp_stop_reason (struct lwp_info *lwp)
- {
- return lwp->stop_reason;
- }
- /* See nat/linux-nat.h. */
- int
- lwp_is_stepping (struct lwp_info *lwp)
- {
- return lwp->step;
- }
- /* Trivial list manipulation functions to keep track of a list of
- new stopped processes. */
- static void
- add_to_pid_list (struct simple_pid_list **listp, int pid, int status)
- {
- struct simple_pid_list *new_pid = XNEW (struct simple_pid_list);
- new_pid->pid = pid;
- new_pid->status = status;
- new_pid->next = *listp;
- *listp = new_pid;
- }
- static int
- pull_pid_from_list (struct simple_pid_list **listp, int pid, int *statusp)
- {
- struct simple_pid_list **p;
- for (p = listp; *p != NULL; p = &(*p)->next)
- if ((*p)->pid == pid)
- {
- struct simple_pid_list *next = (*p)->next;
- *statusp = (*p)->status;
- xfree (*p);
- *p = next;
- return 1;
- }
- return 0;
- }
- /* Return the ptrace options that we want to try to enable. */
- static int
- linux_nat_ptrace_options (int attached)
- {
- int options = 0;
- if (!attached)
- options |= PTRACE_O_EXITKILL;
- options |= (PTRACE_O_TRACESYSGOOD
- | PTRACE_O_TRACEVFORKDONE
- | PTRACE_O_TRACEVFORK
- | PTRACE_O_TRACEFORK
- | PTRACE_O_TRACEEXEC);
- return options;
- }
- /* Initialize ptrace and procfs warnings and check for supported
- ptrace features given PID.
- ATTACHED should be nonzero iff we attached to the inferior. */
- static void
- linux_init_ptrace_procfs (pid_t pid, int attached)
- {
- int options = linux_nat_ptrace_options (attached);
- linux_enable_event_reporting (pid, options);
- linux_ptrace_init_warnings ();
- linux_proc_init_warnings ();
- }
- linux_nat_target::~linux_nat_target ()
- {}
- void
- linux_nat_target::post_attach (int pid)
- {
- linux_init_ptrace_procfs (pid, 1);
- }
- /* Implement the virtual inf_ptrace_target::post_startup_inferior method. */
- void
- linux_nat_target::post_startup_inferior (ptid_t ptid)
- {
- linux_init_ptrace_procfs (ptid.pid (), 0);
- }
- /* Return the number of known LWPs in the tgid given by PID. */
- static int
- num_lwps (int pid)
- {
- int count = 0;
- for (const lwp_info *lp ATTRIBUTE_UNUSED : all_lwps ())
- if (lp->ptid.pid () == pid)
- count++;
- return count;
- }
- /* Deleter for lwp_info unique_ptr specialisation. */
- struct lwp_deleter
- {
- void operator() (struct lwp_info *lwp) const
- {
- delete_lwp (lwp->ptid);
- }
- };
- /* A unique_ptr specialisation for lwp_info. */
- typedef std::unique_ptr<struct lwp_info, lwp_deleter> lwp_info_up;
- /* Target hook for follow_fork. */
- void
- linux_nat_target::follow_fork (inferior *child_inf, ptid_t child_ptid,
- target_waitkind fork_kind, bool follow_child,
- bool detach_fork)
- {
- inf_ptrace_target::follow_fork (child_inf, child_ptid, fork_kind,
- follow_child, detach_fork);
- if (!follow_child)
- {
- bool has_vforked = fork_kind == TARGET_WAITKIND_VFORKED;
- ptid_t parent_ptid = inferior_ptid;
- int parent_pid = parent_ptid.lwp ();
- int child_pid = child_ptid.lwp ();
- /* We're already attached to the parent, by default. */
- lwp_info *child_lp = add_lwp (child_ptid);
- child_lp->stopped = 1;
- child_lp->last_resume_kind = resume_stop;
- /* Detach new forked process? */
- if (detach_fork)
- {
- int child_stop_signal = 0;
- bool detach_child = true;
- /* Move CHILD_LP into a unique_ptr and clear the source pointer
- to prevent us doing anything stupid with it. */
- lwp_info_up child_lp_ptr (child_lp);
- child_lp = nullptr;
- linux_target->low_prepare_to_resume (child_lp_ptr.get ());
- /* When debugging an inferior in an architecture that supports
- hardware single stepping on a kernel without commit
- 6580807da14c423f0d0a708108e6df6ebc8bc83d, the vfork child
- process starts with the TIF_SINGLESTEP/X86_EFLAGS_TF bits
- set if the parent process had them set.
- To work around this, single step the child process
- once before detaching to clear the flags. */
- /* Note that we consult the parent's architecture instead of
- the child's because there's no inferior for the child at
- this point. */
- if (!gdbarch_software_single_step_p (target_thread_architecture
- (parent_ptid)))
- {
- int status;
- linux_disable_event_reporting (child_pid);
- if (ptrace (PTRACE_SINGLESTEP, child_pid, 0, 0) < 0)
- perror_with_name (_("Couldn't do single step"));
- if (my_waitpid (child_pid, &status, 0) < 0)
- perror_with_name (_("Couldn't wait vfork process"));
- else
- {
- detach_child = WIFSTOPPED (status);
- child_stop_signal = WSTOPSIG (status);
- }
- }
- if (detach_child)
- {
- int signo = child_stop_signal;
- if (signo != 0
- && !signal_pass_state (gdb_signal_from_host (signo)))
- signo = 0;
- ptrace (PTRACE_DETACH, child_pid, 0, signo);
- close_proc_mem_file (child_pid);
- }
- }
- if (has_vforked)
- {
- lwp_info *parent_lp = find_lwp_pid (parent_ptid);
- linux_nat_debug_printf ("waiting for VFORK_DONE on %d", parent_pid);
- parent_lp->stopped = 1;
- /* We'll handle the VFORK_DONE event like any other
- event, in target_wait. */
- }
- }
- else
- {
- struct lwp_info *child_lp;
- child_lp = add_lwp (child_ptid);
- child_lp->stopped = 1;
- child_lp->last_resume_kind = resume_stop;
- }
- }
- int
- linux_nat_target::insert_fork_catchpoint (int pid)
- {
- return 0;
- }
- int
- linux_nat_target::remove_fork_catchpoint (int pid)
- {
- return 0;
- }
- int
- linux_nat_target::insert_vfork_catchpoint (int pid)
- {
- return 0;
- }
- int
- linux_nat_target::remove_vfork_catchpoint (int pid)
- {
- return 0;
- }
- int
- linux_nat_target::insert_exec_catchpoint (int pid)
- {
- return 0;
- }
- int
- linux_nat_target::remove_exec_catchpoint (int pid)
- {
- return 0;
- }
- int
- linux_nat_target::set_syscall_catchpoint (int pid, bool needed, int any_count,
- gdb::array_view<const int> syscall_counts)
- {
- /* On GNU/Linux, we ignore the arguments. It means that we only
- enable the syscall catchpoints, but do not disable them.
- Also, we do not use the `syscall_counts' information because we do not
- filter system calls here. We let GDB do the logic for us. */
- return 0;
- }
- /* List of known LWPs, keyed by LWP PID. This speeds up the common
- case of mapping a PID returned from the kernel to our corresponding
- lwp_info data structure. */
- static htab_t lwp_lwpid_htab;
- /* Calculate a hash from a lwp_info's LWP PID. */
- static hashval_t
- lwp_info_hash (const void *ap)
- {
- const struct lwp_info *lp = (struct lwp_info *) ap;
- pid_t pid = lp->ptid.lwp ();
- return iterative_hash_object (pid, 0);
- }
- /* Equality function for the lwp_info hash table. Compares the LWP's
- PID. */
- static int
- lwp_lwpid_htab_eq (const void *a, const void *b)
- {
- const struct lwp_info *entry = (const struct lwp_info *) a;
- const struct lwp_info *element = (const struct lwp_info *) b;
- return entry->ptid.lwp () == element->ptid.lwp ();
- }
- /* Create the lwp_lwpid_htab hash table. */
- static void
- lwp_lwpid_htab_create (void)
- {
- lwp_lwpid_htab = htab_create (100, lwp_info_hash, lwp_lwpid_htab_eq, NULL);
- }
- /* Add LP to the hash table. */
- static void
- lwp_lwpid_htab_add_lwp (struct lwp_info *lp)
- {
- void **slot;
- slot = htab_find_slot (lwp_lwpid_htab, lp, INSERT);
- gdb_assert (slot != NULL && *slot == NULL);
- *slot = lp;
- }
- /* Head of doubly-linked list of known LWPs. Sorted by reverse
- creation order. This order is assumed in some cases. E.g.,
- reaping status after killing alls lwps of a process: the leader LWP
- must be reaped last. */
- static intrusive_list<lwp_info> lwp_list;
- /* See linux-nat.h. */
- lwp_info_range
- all_lwps ()
- {
- return lwp_info_range (lwp_list.begin ());
- }
- /* See linux-nat.h. */
- lwp_info_safe_range
- all_lwps_safe ()
- {
- return lwp_info_safe_range (lwp_list.begin ());
- }
- /* Add LP to sorted-by-reverse-creation-order doubly-linked list. */
- static void
- lwp_list_add (struct lwp_info *lp)
- {
- lwp_list.push_front (*lp);
- }
- /* Remove LP from sorted-by-reverse-creation-order doubly-linked
- list. */
- static void
- lwp_list_remove (struct lwp_info *lp)
- {
- /* Remove from sorted-by-creation-order list. */
- lwp_list.erase (lwp_list.iterator_to (*lp));
- }
- /* Signal mask for use with sigsuspend in linux_nat_wait, initialized in
- _initialize_linux_nat. */
- static sigset_t suspend_mask;
- /* Signals to block to make that sigsuspend work. */
- static sigset_t blocked_mask;
- /* SIGCHLD action. */
- static struct sigaction sigchld_action;
- /* Block child signals (SIGCHLD and linux threads signals), and store
- the previous mask in PREV_MASK. */
- static void
- block_child_signals (sigset_t *prev_mask)
- {
- /* Make sure SIGCHLD is blocked. */
- if (!sigismember (&blocked_mask, SIGCHLD))
- sigaddset (&blocked_mask, SIGCHLD);
- gdb_sigmask (SIG_BLOCK, &blocked_mask, prev_mask);
- }
- /* Restore child signals mask, previously returned by
- block_child_signals. */
- static void
- restore_child_signals_mask (sigset_t *prev_mask)
- {
- gdb_sigmask (SIG_SETMASK, prev_mask, NULL);
- }
- /* Mask of signals to pass directly to the inferior. */
- static sigset_t pass_mask;
- /* Update signals to pass to the inferior. */
- void
- linux_nat_target::pass_signals
- (gdb::array_view<const unsigned char> pass_signals)
- {
- int signo;
- sigemptyset (&pass_mask);
- for (signo = 1; signo < NSIG; signo++)
- {
- int target_signo = gdb_signal_from_host (signo);
- if (target_signo < pass_signals.size () && pass_signals[target_signo])
- sigaddset (&pass_mask, signo);
- }
- }
- /* Prototypes for local functions. */
- static int stop_wait_callback (struct lwp_info *lp);
- static int resume_stopped_resumed_lwps (struct lwp_info *lp, const ptid_t wait_ptid);
- static int check_ptrace_stopped_lwp_gone (struct lwp_info *lp);
- /* Destroy and free LP. */
- lwp_info::~lwp_info ()
- {
- /* Let the arch specific bits release arch_lwp_info. */
- linux_target->low_delete_thread (this->arch_private);
- }
- /* Traversal function for purge_lwp_list. */
- static int
- lwp_lwpid_htab_remove_pid (void **slot, void *info)
- {
- struct lwp_info *lp = (struct lwp_info *) *slot;
- int pid = *(int *) info;
- if (lp->ptid.pid () == pid)
- {
- htab_clear_slot (lwp_lwpid_htab, slot);
- lwp_list_remove (lp);
- delete lp;
- }
- return 1;
- }
- /* Remove all LWPs belong to PID from the lwp list. */
- static void
- purge_lwp_list (int pid)
- {
- htab_traverse_noresize (lwp_lwpid_htab, lwp_lwpid_htab_remove_pid, &pid);
- }
- /* Add the LWP specified by PTID to the list. PTID is the first LWP
- in the process. Return a pointer to the structure describing the
- new LWP.
- This differs from add_lwp in that we don't let the arch specific
- bits know about this new thread. Current clients of this callback
- take the opportunity to install watchpoints in the new thread, and
- we shouldn't do that for the first thread. If we're spawning a
- child ("run"), the thread executes the shell wrapper first, and we
- shouldn't touch it until it execs the program we want to debug.
- For "attach", it'd be okay to call the callback, but it's not
- necessary, because watchpoints can't yet have been inserted into
- the inferior. */
- static struct lwp_info *
- add_initial_lwp (ptid_t ptid)
- {
- gdb_assert (ptid.lwp_p ());
- lwp_info *lp = new lwp_info (ptid);
- /* Add to sorted-by-reverse-creation-order list. */
- lwp_list_add (lp);
- /* Add to keyed-by-pid htab. */
- lwp_lwpid_htab_add_lwp (lp);
- return lp;
- }
- /* Add the LWP specified by PID to the list. Return a pointer to the
- structure describing the new LWP. The LWP should already be
- stopped. */
- static struct lwp_info *
- add_lwp (ptid_t ptid)
- {
- struct lwp_info *lp;
- lp = add_initial_lwp (ptid);
- /* Let the arch specific bits know about this new thread. Current
- clients of this callback take the opportunity to install
- watchpoints in the new thread. We don't do this for the first
- thread though. See add_initial_lwp. */
- linux_target->low_new_thread (lp);
- return lp;
- }
- /* Remove the LWP specified by PID from the list. */
- static void
- delete_lwp (ptid_t ptid)
- {
- lwp_info dummy (ptid);
- void **slot = htab_find_slot (lwp_lwpid_htab, &dummy, NO_INSERT);
- if (slot == NULL)
- return;
- lwp_info *lp = *(struct lwp_info **) slot;
- gdb_assert (lp != NULL);
- htab_clear_slot (lwp_lwpid_htab, slot);
- /* Remove from sorted-by-creation-order list. */
- lwp_list_remove (lp);
- /* Release. */
- delete lp;
- }
- /* Return a pointer to the structure describing the LWP corresponding
- to PID. If no corresponding LWP could be found, return NULL. */
- static struct lwp_info *
- find_lwp_pid (ptid_t ptid)
- {
- int lwp;
- if (ptid.lwp_p ())
- lwp = ptid.lwp ();
- else
- lwp = ptid.pid ();
- lwp_info dummy (ptid_t (0, lwp));
- return (struct lwp_info *) htab_find (lwp_lwpid_htab, &dummy);
- }
- /* See nat/linux-nat.h. */
- struct lwp_info *
- iterate_over_lwps (ptid_t filter,
- gdb::function_view<iterate_over_lwps_ftype> callback)
- {
- for (lwp_info *lp : all_lwps_safe ())
- {
- if (lp->ptid.matches (filter))
- {
- if (callback (lp) != 0)
- return lp;
- }
- }
- return NULL;
- }
- /* Update our internal state when changing from one checkpoint to
- another indicated by NEW_PTID. We can only switch single-threaded
- applications, so we only create one new LWP, and the previous list
- is discarded. */
- void
- linux_nat_switch_fork (ptid_t new_ptid)
- {
- struct lwp_info *lp;
- purge_lwp_list (inferior_ptid.pid ());
- lp = add_lwp (new_ptid);
- lp->stopped = 1;
- /* This changes the thread's ptid while preserving the gdb thread
- num. Also changes the inferior pid, while preserving the
- inferior num. */
- thread_change_ptid (linux_target, inferior_ptid, new_ptid);
- /* We've just told GDB core that the thread changed target id, but,
- in fact, it really is a different thread, with different register
- contents. */
- registers_changed ();
- }
- /* Handle the exit of a single thread LP. */
- static void
- exit_lwp (struct lwp_info *lp)
- {
- struct thread_info *th = find_thread_ptid (linux_target, lp->ptid);
- if (th)
- {
- if (print_thread_events)
- gdb_printf (_("[%s exited]\n"),
- target_pid_to_str (lp->ptid).c_str ());
- delete_thread (th);
- }
- delete_lwp (lp->ptid);
- }
- /* Wait for the LWP specified by LP, which we have just attached to.
- Returns a wait status for that LWP, to cache. */
- static int
- linux_nat_post_attach_wait (ptid_t ptid, int *signalled)
- {
- pid_t new_pid, pid = ptid.lwp ();
- int status;
- if (linux_proc_pid_is_stopped (pid))
- {
- linux_nat_debug_printf ("Attaching to a stopped process");
- /* The process is definitely stopped. It is in a job control
- stop, unless the kernel predates the TASK_STOPPED /
- TASK_TRACED distinction, in which case it might be in a
- ptrace stop. Make sure it is in a ptrace stop; from there we
- can kill it, signal it, et cetera.
- First make sure there is a pending SIGSTOP. Since we are
- already attached, the process can not transition from stopped
- to running without a PTRACE_CONT; so we know this signal will
- go into the queue. The SIGSTOP generated by PTRACE_ATTACH is
- probably already in the queue (unless this kernel is old
- enough to use TASK_STOPPED for ptrace stops); but since SIGSTOP
- is not an RT signal, it can only be queued once. */
- kill_lwp (pid, SIGSTOP);
- /* Finally, resume the stopped process. This will deliver the SIGSTOP
- (or a higher priority signal, just like normal PTRACE_ATTACH). */
- ptrace (PTRACE_CONT, pid, 0, 0);
- }
- /* Make sure the initial process is stopped. The user-level threads
- layer might want to poke around in the inferior, and that won't
- work if things haven't stabilized yet. */
- new_pid = my_waitpid (pid, &status, __WALL);
- gdb_assert (pid == new_pid);
- if (!WIFSTOPPED (status))
- {
- /* The pid we tried to attach has apparently just exited. */
- linux_nat_debug_printf ("Failed to stop %d: %s", pid,
- status_to_str (status).c_str ());
- return status;
- }
- if (WSTOPSIG (status) != SIGSTOP)
- {
- *signalled = 1;
- linux_nat_debug_printf ("Received %s after attaching",
- status_to_str (status).c_str ());
- }
- return status;
- }
- void
- linux_nat_target::create_inferior (const char *exec_file,
- const std::string &allargs,
- char **env, int from_tty)
- {
- maybe_disable_address_space_randomization restore_personality
- (disable_randomization);
- /* The fork_child mechanism is synchronous and calls target_wait, so
- we have to mask the async mode. */
- /* Make sure we report all signals during startup. */
- pass_signals ({});
- inf_ptrace_target::create_inferior (exec_file, allargs, env, from_tty);
- open_proc_mem_file (inferior_ptid);
- }
- /* Callback for linux_proc_attach_tgid_threads. Attach to PTID if not
- already attached. Returns true if a new LWP is found, false
- otherwise. */
- static int
- attach_proc_task_lwp_callback (ptid_t ptid)
- {
- struct lwp_info *lp;
- /* Ignore LWPs we're already attached to. */
- lp = find_lwp_pid (ptid);
- if (lp == NULL)
- {
- int lwpid = ptid.lwp ();
- if (ptrace (PTRACE_ATTACH, lwpid, 0, 0) < 0)
- {
- int err = errno;
- /* Be quiet if we simply raced with the thread exiting.
- EPERM is returned if the thread's task still exists, and
- is marked as exited or zombie, as well as other
- conditions, so in that case, confirm the status in
- /proc/PID/status. */
- if (err == ESRCH
- || (err == EPERM && linux_proc_pid_is_gone (lwpid)))
- {
- linux_nat_debug_printf
- ("Cannot attach to lwp %d: thread is gone (%d: %s)",
- lwpid, err, safe_strerror (err));
- }
- else
- {
- std::string reason
- = linux_ptrace_attach_fail_reason_string (ptid, err);
- warning (_("Cannot attach to lwp %d: %s"),
- lwpid, reason.c_str ());
- }
- }
- else
- {
- linux_nat_debug_printf ("PTRACE_ATTACH %s, 0, 0 (OK)",
- ptid.to_string ().c_str ());
- lp = add_lwp (ptid);
- /* The next time we wait for this LWP we'll see a SIGSTOP as
- PTRACE_ATTACH brings it to a halt. */
- lp->signalled = 1;
- /* We need to wait for a stop before being able to make the
- next ptrace call on this LWP. */
- lp->must_set_ptrace_flags = 1;
- /* So that wait collects the SIGSTOP. */
- lp->resumed = 1;
- /* Also add the LWP to gdb's thread list, in case a
- matching libthread_db is not found (or the process uses
- raw clone). */
- add_thread (linux_target, lp->ptid);
- set_running (linux_target, lp->ptid, true);
- set_executing (linux_target, lp->ptid, true);
- }
- return 1;
- }
- return 0;
- }
- void
- linux_nat_target::attach (const char *args, int from_tty)
- {
- struct lwp_info *lp;
- int status;
- ptid_t ptid;
- /* Make sure we report all signals during attach. */
- pass_signals ({});
- try
- {
- inf_ptrace_target::attach (args, from_tty);
- }
- catch (const gdb_exception_error &ex)
- {
- pid_t pid = parse_pid_to_attach (args);
- std::string reason = linux_ptrace_attach_fail_reason (pid);
- if (!reason.empty ())
- throw_error (ex.error, "warning: %s\n%s", reason.c_str (),
- ex.what ());
- else
- throw_error (ex.error, "%s", ex.what ());
- }
- /* The ptrace base target adds the main thread with (pid,0,0)
- format. Decorate it with lwp info. */
- ptid = ptid_t (inferior_ptid.pid (),
- inferior_ptid.pid ());
- thread_change_ptid (linux_target, inferior_ptid, ptid);
- /* Add the initial process as the first LWP to the list. */
- lp = add_initial_lwp (ptid);
- status = linux_nat_post_attach_wait (lp->ptid, &lp->signalled);
- if (!WIFSTOPPED (status))
- {
- if (WIFEXITED (status))
- {
- int exit_code = WEXITSTATUS (status);
- target_terminal::ours ();
- target_mourn_inferior (inferior_ptid);
- if (exit_code == 0)
- error (_("Unable to attach: program exited normally."));
- else
- error (_("Unable to attach: program exited with code %d."),
- exit_code);
- }
- else if (WIFSIGNALED (status))
- {
- enum gdb_signal signo;
- target_terminal::ours ();
- target_mourn_inferior (inferior_ptid);
- signo = gdb_signal_from_host (WTERMSIG (status));
- error (_("Unable to attach: program terminated with signal "
- "%s, %s."),
- gdb_signal_to_name (signo),
- gdb_signal_to_string (signo));
- }
- internal_error (__FILE__, __LINE__,
- _("unexpected status %d for PID %ld"),
- status, (long) ptid.lwp ());
- }
- lp->stopped = 1;
- open_proc_mem_file (lp->ptid);
- /* Save the wait status to report later. */
- lp->resumed = 1;
- linux_nat_debug_printf ("waitpid %ld, saving status %s",
- (long) lp->ptid.pid (),
- status_to_str (status).c_str ());
- lp->status = status;
- /* We must attach to every LWP. If /proc is mounted, use that to
- find them now. The inferior may be using raw clone instead of
- using pthreads. But even if it is using pthreads, thread_db
- walks structures in the inferior's address space to find the list
- of threads/LWPs, and those structures may well be corrupted.
- Note that once thread_db is loaded, we'll still use it to list
- threads and associate pthread info with each LWP. */
- linux_proc_attach_tgid_threads (lp->ptid.pid (),
- attach_proc_task_lwp_callback);
- }
- /* Ptrace-detach the thread with pid PID. */
- static void
- detach_one_pid (int pid, int signo)
- {
- if (ptrace (PTRACE_DETACH, pid, 0, signo) < 0)
- {
- int save_errno = errno;
- /* We know the thread exists, so ESRCH must mean the lwp is
- zombie. This can happen if one of the already-detached
- threads exits the whole thread group. In that case we're
- still attached, and must reap the lwp. */
- if (save_errno == ESRCH)
- {
- int ret, status;
- ret = my_waitpid (pid, &status, __WALL);
- if (ret == -1)
- {
- warning (_("Couldn't reap LWP %d while detaching: %s"),
- pid, safe_strerror (errno));
- }
- else if (!WIFEXITED (status) && !WIFSIGNALED (status))
- {
- warning (_("Reaping LWP %d while detaching "
- "returned unexpected status 0x%x"),
- pid, status);
- }
- }
- else
- error (_("Can't detach %d: %s"),
- pid, safe_strerror (save_errno));
- }
- else
- linux_nat_debug_printf ("PTRACE_DETACH (%d, %s, 0) (OK)",
- pid, strsignal (signo));
- }
- /* Get pending signal of THREAD as a host signal number, for detaching
- purposes. This is the signal the thread last stopped for, which we
- need to deliver to the thread when detaching, otherwise, it'd be
- suppressed/lost. */
- static int
- get_detach_signal (struct lwp_info *lp)
- {
- enum gdb_signal signo = GDB_SIGNAL_0;
- /* If we paused threads momentarily, we may have stored pending
- events in lp->status or lp->waitstatus (see stop_wait_callback),
- and GDB core hasn't seen any signal for those threads.
- Otherwise, the last signal reported to the core is found in the
- thread object's stop_signal.
- There's a corner case that isn't handled here at present. Only
- if the thread stopped with a TARGET_WAITKIND_STOPPED does
- stop_signal make sense as a real signal to pass to the inferior.
- Some catchpoint related events, like
- TARGET_WAITKIND_(V)FORK|EXEC|SYSCALL, have their stop_signal set
- to GDB_SIGNAL_SIGTRAP when the catchpoint triggers. But,
- those traps are debug API (ptrace in our case) related and
- induced; the inferior wouldn't see them if it wasn't being
- traced. Hence, we should never pass them to the inferior, even
- when set to pass state. Since this corner case isn't handled by
- infrun.c when proceeding with a signal, for consistency, neither
- do we handle it here (or elsewhere in the file we check for
- signal pass state). Normally SIGTRAP isn't set to pass state, so
- this is really a corner case. */
- if (lp->waitstatus.kind () != TARGET_WAITKIND_IGNORE)
- signo = GDB_SIGNAL_0; /* a pending ptrace event, not a real signal. */
- else if (lp->status)
- signo = gdb_signal_from_host (WSTOPSIG (lp->status));
- else
- {
- struct thread_info *tp = find_thread_ptid (linux_target, lp->ptid);
- if (target_is_non_stop_p () && !tp->executing ())
- {
- if (tp->has_pending_waitstatus ())
- {
- /* If the thread has a pending event, and it was stopped with a
- signal, use that signal to resume it. If it has a pending
- event of another kind, it was not stopped with a signal, so
- resume it without a signal. */
- if (tp->pending_waitstatus ().kind () == TARGET_WAITKIND_STOPPED)
- signo = tp->pending_waitstatus ().sig ();
- else
- signo = GDB_SIGNAL_0;
- }
- else
- signo = tp->stop_signal ();
- }
- else if (!target_is_non_stop_p ())
- {
- ptid_t last_ptid;
- process_stratum_target *last_target;
- get_last_target_status (&last_target, &last_ptid, nullptr);
- if (last_target == linux_target
- && lp->ptid.lwp () == last_ptid.lwp ())
- signo = tp->stop_signal ();
- }
- }
- if (signo == GDB_SIGNAL_0)
- {
- linux_nat_debug_printf ("lwp %s has no pending signal",
- lp->ptid.to_string ().c_str ());
- }
- else if (!signal_pass_state (signo))
- {
- linux_nat_debug_printf
- ("lwp %s had signal %s but it is in no pass state",
- lp->ptid.to_string ().c_str (), gdb_signal_to_string (signo));
- }
- else
- {
- linux_nat_debug_printf ("lwp %s has pending signal %s",
- lp->ptid.to_string ().c_str (),
- gdb_signal_to_string (signo));
- return gdb_signal_to_host (signo);
- }
- return 0;
- }
- /* Detach from LP. If SIGNO_P is non-NULL, then it points to the
- signal number that should be passed to the LWP when detaching.
- Otherwise pass any pending signal the LWP may have, if any. */
- static void
- detach_one_lwp (struct lwp_info *lp, int *signo_p)
- {
- int lwpid = lp->ptid.lwp ();
- int signo;
- gdb_assert (lp->status == 0 || WIFSTOPPED (lp->status));
- /* If the lwp/thread we are about to detach has a pending fork event,
- there is a process GDB is attached to that the core of GDB doesn't know
- about. Detach from it. */
- /* Check in lwp_info::status. */
- if (WIFSTOPPED (lp->status) && linux_is_extended_waitstatus (lp->status))
- {
- int event = linux_ptrace_get_extended_event (lp->status);
- if (event == PTRACE_EVENT_FORK || event == PTRACE_EVENT_VFORK)
- {
- unsigned long child_pid;
- int ret = ptrace (PTRACE_GETEVENTMSG, lp->ptid.lwp (), 0, &child_pid);
- if (ret == 0)
- detach_one_pid (child_pid, 0);
- else
- perror_warning_with_name (_("Failed to detach fork child"));
- }
- }
- /* Check in lwp_info::waitstatus. */
- if (lp->waitstatus.kind () == TARGET_WAITKIND_VFORKED
- || lp->waitstatus.kind () == TARGET_WAITKIND_FORKED)
- detach_one_pid (lp->waitstatus.child_ptid ().pid (), 0);
- /* Check in thread_info::pending_waitstatus. */
- thread_info *tp = find_thread_ptid (linux_target, lp->ptid);
- if (tp->has_pending_waitstatus ())
- {
- const target_waitstatus &ws = tp->pending_waitstatus ();
- if (ws.kind () == TARGET_WAITKIND_VFORKED
- || ws.kind () == TARGET_WAITKIND_FORKED)
- detach_one_pid (ws.child_ptid ().pid (), 0);
- }
- /* Check in thread_info::pending_follow. */
- if (tp->pending_follow.kind () == TARGET_WAITKIND_VFORKED
- || tp->pending_follow.kind () == TARGET_WAITKIND_FORKED)
- detach_one_pid (tp->pending_follow.child_ptid ().pid (), 0);
- if (lp->status != 0)
- linux_nat_debug_printf ("Pending %s for %s on detach.",
- strsignal (WSTOPSIG (lp->status)),
- lp->ptid.to_string ().c_str ());
- /* If there is a pending SIGSTOP, get rid of it. */
- if (lp->signalled)
- {
- linux_nat_debug_printf ("Sending SIGCONT to %s",
- lp->ptid.to_string ().c_str ());
- kill_lwp (lwpid, SIGCONT);
- lp->signalled = 0;
- }
- if (signo_p == NULL)
- {
- /* Pass on any pending signal for this LWP. */
- signo = get_detach_signal (lp);
- }
- else
- signo = *signo_p;
- /* Preparing to resume may try to write registers, and fail if the
- lwp is zombie. If that happens, ignore the error. We'll handle
- it below, when detach fails with ESRCH. */
- try
- {
- linux_target->low_prepare_to_resume (lp);
- }
- catch (const gdb_exception_error &ex)
- {
- if (!check_ptrace_stopped_lwp_gone (lp))
- throw;
- }
- detach_one_pid (lwpid, signo);
- delete_lwp (lp->ptid);
- }
- static int
- detach_callback (struct lwp_info *lp)
- {
- /* We don't actually detach from the thread group leader just yet.
- If the thread group exits, we must reap the zombie clone lwps
- before we're able to reap the leader. */
- if (lp->ptid.lwp () != lp->ptid.pid ())
- detach_one_lwp (lp, NULL);
- return 0;
- }
- void
- linux_nat_target::detach (inferior *inf, int from_tty)
- {
- struct lwp_info *main_lwp;
- int pid = inf->pid;
- /* Don't unregister from the event loop, as there may be other
- inferiors running. */
- /* Stop all threads before detaching. ptrace requires that the
- thread is stopped to successfully detach. */
- iterate_over_lwps (ptid_t (pid), stop_callback);
- /* ... and wait until all of them have reported back that
- they're no longer running. */
- iterate_over_lwps (ptid_t (pid), stop_wait_callback);
- /* We can now safely remove breakpoints. We don't this in earlier
- in common code because this target doesn't currently support
- writing memory while the inferior is running. */
- remove_breakpoints_inf (current_inferior ());
- iterate_over_lwps (ptid_t (pid), detach_callback);
- /* Only the initial process should be left right now. */
- gdb_assert (num_lwps (pid) == 1);
- main_lwp = find_lwp_pid (ptid_t (pid));
- if (forks_exist_p ())
- {
- /* Multi-fork case. The current inferior_ptid is being detached
- from, but there are other viable forks to debug. Detach from
- the current fork, and context-switch to the first
- available. */
- linux_fork_detach (from_tty);
- }
- else
- {
- target_announce_detach (from_tty);
- /* Pass on any pending signal for the last LWP. */
- int signo = get_detach_signal (main_lwp);
- detach_one_lwp (main_lwp, &signo);
- detach_success (inf);
- }
- close_proc_mem_file (pid);
- }
- /* Resume execution of the inferior process. If STEP is nonzero,
- single-step it. If SIGNAL is nonzero, give it that signal. */
- static void
- linux_resume_one_lwp_throw (struct lwp_info *lp, int step,
- enum gdb_signal signo)
- {
- lp->step = step;
- /* stop_pc doubles as the PC the LWP had when it was last resumed.
- We only presently need that if the LWP is stepped though (to
- handle the case of stepping a breakpoint instruction). */
- if (step)
- {
- struct regcache *regcache = get_thread_regcache (linux_target, lp->ptid);
- lp->stop_pc = regcache_read_pc (regcache);
- }
- else
- lp->stop_pc = 0;
- linux_target->low_prepare_to_resume (lp);
- linux_target->low_resume (lp->ptid, step, signo);
- /* Successfully resumed. Clear state that no longer makes sense,
- and mark the LWP as running. Must not do this before resuming
- otherwise if that fails other code will be confused. E.g., we'd
- later try to stop the LWP and hang forever waiting for a stop
- status. Note that we must not throw after this is cleared,
- otherwise handle_zombie_lwp_error would get confused. */
- lp->stopped = 0;
- lp->core = -1;
- lp->stop_reason = TARGET_STOPPED_BY_NO_REASON;
- registers_changed_ptid (linux_target, lp->ptid);
- }
- /* Called when we try to resume a stopped LWP and that errors out. If
- the LWP is no longer in ptrace-stopped state (meaning it's zombie,
- or about to become), discard the error, clear any pending status
- the LWP may have, and return true (we'll collect the exit status
- soon enough). Otherwise, return false. */
- static int
- check_ptrace_stopped_lwp_gone (struct lwp_info *lp)
- {
- /* If we get an error after resuming the LWP successfully, we'd
- confuse !T state for the LWP being gone. */
- gdb_assert (lp->stopped);
- /* We can't just check whether the LWP is in 'Z (Zombie)' state,
- because even if ptrace failed with ESRCH, the tracee may be "not
- yet fully dead", but already refusing ptrace requests. In that
- case the tracee has 'R (Running)' state for a little bit
- (observed in Linux 3.18). See also the note on ESRCH in the
- ptrace(2) man page. Instead, check whether the LWP has any state
- other than ptrace-stopped. */
- /* Don't assume anything if /proc/PID/status can't be read. */
- if (linux_proc_pid_is_trace_stopped_nowarn (lp->ptid.lwp ()) == 0)
- {
- lp->stop_reason = TARGET_STOPPED_BY_NO_REASON;
- lp->status = 0;
- lp->waitstatus.set_ignore ();
- return 1;
- }
- return 0;
- }
- /* Like linux_resume_one_lwp_throw, but no error is thrown if the LWP
- disappears while we try to resume it. */
- static void
- linux_resume_one_lwp (struct lwp_info *lp, int step, enum gdb_signal signo)
- {
- try
- {
- linux_resume_one_lwp_throw (lp, step, signo);
- }
- catch (const gdb_exception_error &ex)
- {
- if (!check_ptrace_stopped_lwp_gone (lp))
- throw;
- }
- }
- /* Resume LP. */
- static void
- resume_lwp (struct lwp_info *lp, int step, enum gdb_signal signo)
- {
- if (lp->stopped)
- {
- struct inferior *inf = find_inferior_ptid (linux_target, lp->ptid);
- if (inf->vfork_child != NULL)
- {
- linux_nat_debug_printf ("Not resuming %s (vfork parent)",
- lp->ptid.to_string ().c_str ());
- }
- else if (!lwp_status_pending_p (lp))
- {
- linux_nat_debug_printf ("Resuming sibling %s, %s, %s",
- lp->ptid.to_string ().c_str (),
- (signo != GDB_SIGNAL_0
- ? strsignal (gdb_signal_to_host (signo))
- : "0"),
- step ? "step" : "resume");
- linux_resume_one_lwp (lp, step, signo);
- }
- else
- {
- linux_nat_debug_printf ("Not resuming sibling %s (has pending)",
- lp->ptid.to_string ().c_str ());
- }
- }
- else
- linux_nat_debug_printf ("Not resuming sibling %s (not stopped)",
- lp->ptid.to_string ().c_str ());
- }
- /* Callback for iterate_over_lwps. If LWP is EXCEPT, do nothing.
- Resume LWP with the last stop signal, if it is in pass state. */
- static int
- linux_nat_resume_callback (struct lwp_info *lp, struct lwp_info *except)
- {
- enum gdb_signal signo = GDB_SIGNAL_0;
- if (lp == except)
- return 0;
- if (lp->stopped)
- {
- struct thread_info *thread;
- thread = find_thread_ptid (linux_target, lp->ptid);
- if (thread != NULL)
- {
- signo = thread->stop_signal ();
- thread->set_stop_signal (GDB_SIGNAL_0);
- }
- }
- resume_lwp (lp, 0, signo);
- return 0;
- }
- static int
- resume_clear_callback (struct lwp_info *lp)
- {
- lp->resumed = 0;
- lp->last_resume_kind = resume_stop;
- return 0;
- }
- static int
- resume_set_callback (struct lwp_info *lp)
- {
- lp->resumed = 1;
- lp->last_resume_kind = resume_continue;
- return 0;
- }
- void
- linux_nat_target::resume (ptid_t ptid, int step, enum gdb_signal signo)
- {
- struct lwp_info *lp;
- int resume_many;
- linux_nat_debug_printf ("Preparing to %s %s, %s, inferior_ptid %s",
- step ? "step" : "resume",
- ptid.to_string ().c_str (),
- (signo != GDB_SIGNAL_0
- ? strsignal (gdb_signal_to_host (signo)) : "0"),
- inferior_ptid.to_string ().c_str ());
- /* A specific PTID means `step only this process id'. */
- resume_many = (minus_one_ptid == ptid
- || ptid.is_pid ());
- /* Mark the lwps we're resuming as resumed and update their
- last_resume_kind to resume_continue. */
- iterate_over_lwps (ptid, resume_set_callback);
- /* See if it's the current inferior that should be handled
- specially. */
- if (resume_many)
- lp = find_lwp_pid (inferior_ptid);
- else
- lp = find_lwp_pid (ptid);
- gdb_assert (lp != NULL);
- /* Remember if we're stepping. */
- lp->last_resume_kind = step ? resume_step : resume_continue;
- /* If we have a pending wait status for this thread, there is no
- point in resuming the process. But first make sure that
- linux_nat_wait won't preemptively handle the event - we
- should never take this short-circuit if we are going to
- leave LP running, since we have skipped resuming all the
- other threads. This bit of code needs to be synchronized
- with linux_nat_wait. */
- if (lp->status && WIFSTOPPED (lp->status))
- {
- if (!lp->step
- && WSTOPSIG (lp->status)
- && sigismember (&pass_mask, WSTOPSIG (lp->status)))
- {
- linux_nat_debug_printf
- ("Not short circuiting for ignored status 0x%x", lp->status);
- /* FIXME: What should we do if we are supposed to continue
- this thread with a signal? */
- gdb_assert (signo == GDB_SIGNAL_0);
- signo = gdb_signal_from_host (WSTOPSIG (lp->status));
- lp->status = 0;
- }
- }
- if (lwp_status_pending_p (lp))
- {
- /* FIXME: What should we do if we are supposed to continue
- this thread with a signal? */
- gdb_assert (signo == GDB_SIGNAL_0);
- linux_nat_debug_printf ("Short circuiting for status 0x%x",
- lp->status);
- if (target_can_async_p ())
- {
- target_async (1);
- /* Tell the event loop we have something to process. */
- async_file_mark ();
- }
- return;
- }
- if (resume_many)
- iterate_over_lwps (ptid, [=] (struct lwp_info *info)
- {
- return linux_nat_resume_callback (info, lp);
- });
- linux_nat_debug_printf ("%s %s, %s (resume event thread)",
- step ? "PTRACE_SINGLESTEP" : "PTRACE_CONT",
- lp->ptid.to_string ().c_str (),
- (signo != GDB_SIGNAL_0
- ? strsignal (gdb_signal_to_host (signo)) : "0"));
- linux_resume_one_lwp (lp, step, signo);
- }
- /* Send a signal to an LWP. */
- static int
- kill_lwp (int lwpid, int signo)
- {
- int ret;
- errno = 0;
- ret = syscall (__NR_tkill, lwpid, signo);
- if (errno == ENOSYS)
- {
- /* If tkill fails, then we are not using nptl threads, a
- configuration we no longer support. */
- perror_with_name (("tkill"));
- }
- return ret;
- }
- /* Handle a GNU/Linux syscall trap wait response. If we see a syscall
- event, check if the core is interested in it: if not, ignore the
- event, and keep waiting; otherwise, we need to toggle the LWP's
- syscall entry/exit status, since the ptrace event itself doesn't
- indicate it, and report the trap to higher layers. */
- static int
- linux_handle_syscall_trap (struct lwp_info *lp, int stopping)
- {
- struct target_waitstatus *ourstatus = &lp->waitstatus;
- struct gdbarch *gdbarch = target_thread_architecture (lp->ptid);
- thread_info *thread = find_thread_ptid (linux_target, lp->ptid);
- int syscall_number = (int) gdbarch_get_syscall_number (gdbarch, thread);
- if (stopping)
- {
- /* If we're stopping threads, there's a SIGSTOP pending, which
- makes it so that the LWP reports an immediate syscall return,
- followed by the SIGSTOP. Skip seeing that "return" using
- PTRACE_CONT directly, and let stop_wait_callback collect the
- SIGSTOP. Later when the thread is resumed, a new syscall
- entry event. If we didn't do this (and returned 0), we'd
- leave a syscall entry pending, and our caller, by using
- PTRACE_CONT to collect the SIGSTOP, skips the syscall return
- itself. Later, when the user re-resumes this LWP, we'd see
- another syscall entry event and we'd mistake it for a return.
- If stop_wait_callback didn't force the SIGSTOP out of the LWP
- (leaving immediately with LWP->signalled set, without issuing
- a PTRACE_CONT), it would still be problematic to leave this
- syscall enter pending, as later when the thread is resumed,
- it would then see the same syscall exit mentioned above,
- followed by the delayed SIGSTOP, while the syscall didn't
- actually get to execute. It seems it would be even more
- confusing to the user. */
- linux_nat_debug_printf
- ("ignoring syscall %d for LWP %ld (stopping threads), resuming with "
- "PTRACE_CONT for SIGSTOP", syscall_number, lp->ptid.lwp ());
- lp->syscall_state = TARGET_WAITKIND_IGNORE;
- ptrace (PTRACE_CONT, lp->ptid.lwp (), 0, 0);
- lp->stopped = 0;
- return 1;
- }
- /* Always update the entry/return state, even if this particular
- syscall isn't interesting to the core now. In async mode,
- the user could install a new catchpoint for this syscall
- between syscall enter/return, and we'll need to know to
- report a syscall return if that happens. */
- lp->syscall_state = (lp->syscall_state == TARGET_WAITKIND_SYSCALL_ENTRY
- ? TARGET_WAITKIND_SYSCALL_RETURN
- : TARGET_WAITKIND_SYSCALL_ENTRY);
- if (catch_syscall_enabled ())
- {
- if (catching_syscall_number (syscall_number))
- {
- /* Alright, an event to report. */
- if (lp->syscall_state == TARGET_WAITKIND_SYSCALL_ENTRY)
- ourstatus->set_syscall_entry (syscall_number);
- else if (lp->syscall_state == TARGET_WAITKIND_SYSCALL_RETURN)
- ourstatus->set_syscall_return (syscall_number);
- else
- gdb_assert_not_reached ("unexpected syscall state");
- linux_nat_debug_printf
- ("stopping for %s of syscall %d for LWP %ld",
- (lp->syscall_state == TARGET_WAITKIND_SYSCALL_ENTRY
- ? "entry" : "return"), syscall_number, lp->ptid.lwp ());
- return 0;
- }
- linux_nat_debug_printf
- ("ignoring %s of syscall %d for LWP %ld",
- (lp->syscall_state == TARGET_WAITKIND_SYSCALL_ENTRY
- ? "entry" : "return"), syscall_number, lp->ptid.lwp ());
- }
- else
- {
- /* If we had been syscall tracing, and hence used PT_SYSCALL
- before on this LWP, it could happen that the user removes all
- syscall catchpoints before we get to process this event.
- There are two noteworthy issues here:
- - When stopped at a syscall entry event, resuming with
- PT_STEP still resumes executing the syscall and reports a
- syscall return.
- - Only PT_SYSCALL catches syscall enters. If we last
- single-stepped this thread, then this event can't be a
- syscall enter. If we last single-stepped this thread, this
- has to be a syscall exit.
- The points above mean that the next resume, be it PT_STEP or
- PT_CONTINUE, can not trigger a syscall trace event. */
- linux_nat_debug_printf
- ("caught syscall event with no syscall catchpoints. %d for LWP %ld, "
- "ignoring", syscall_number, lp->ptid.lwp ());
- lp->syscall_state = TARGET_WAITKIND_IGNORE;
- }
- /* The core isn't interested in this event. For efficiency, avoid
- stopping all threads only to have the core resume them all again.
- Since we're not stopping threads, if we're still syscall tracing
- and not stepping, we can't use PTRACE_CONT here, as we'd miss any
- subsequent syscall. Simply resume using the inf-ptrace layer,
- which knows when to use PT_SYSCALL or PT_CONTINUE. */
- linux_resume_one_lwp (lp, lp->step, GDB_SIGNAL_0);
- return 1;
- }
- /* Handle a GNU/Linux extended wait response. If we see a clone
- event, we need to add the new LWP to our list (and not report the
- trap to higher layers). This function returns non-zero if the
- event should be ignored and we should wait again. If STOPPING is
- true, the new LWP remains stopped, otherwise it is continued. */
- static int
- linux_handle_extended_wait (struct lwp_info *lp, int status)
- {
- int pid = lp->ptid.lwp ();
- struct target_waitstatus *ourstatus = &lp->waitstatus;
- int event = linux_ptrace_get_extended_event (status);
- /* All extended events we currently use are mid-syscall. Only
- PTRACE_EVENT_STOP is delivered more like a signal-stop, but
- you have to be using PTRACE_SEIZE to get that. */
- lp->syscall_state = TARGET_WAITKIND_SYSCALL_ENTRY;
- if (event == PTRACE_EVENT_FORK || event == PTRACE_EVENT_VFORK
- || event == PTRACE_EVENT_CLONE)
- {
- unsigned long new_pid;
- int ret;
- ptrace (PTRACE_GETEVENTMSG, pid, 0, &new_pid);
- /* If we haven't already seen the new PID stop, wait for it now. */
- if (! pull_pid_from_list (&stopped_pids, new_pid, &status))
- {
- /* The new child has a pending SIGSTOP. We can't affect it until it
- hits the SIGSTOP, but we're already attached. */
- ret = my_waitpid (new_pid, &status, __WALL);
- if (ret == -1)
- perror_with_name (_("waiting for new child"));
- else if (ret != new_pid)
- internal_error (__FILE__, __LINE__,
- _("wait returned unexpected PID %d"), ret);
- else if (!WIFSTOPPED (status))
- internal_error (__FILE__, __LINE__,
- _("wait returned unexpected status 0x%x"), status);
- }
- ptid_t child_ptid (new_pid, new_pid);
- if (event == PTRACE_EVENT_FORK || event == PTRACE_EVENT_VFORK)
- {
- open_proc_mem_file (child_ptid);
- /* The arch-specific native code may need to know about new
- forks even if those end up never mapped to an
- inferior. */
- linux_target->low_new_fork (lp, new_pid);
- }
- else if (event == PTRACE_EVENT_CLONE)
- {
- linux_target->low_new_clone (lp, new_pid);
- }
- if (event == PTRACE_EVENT_FORK
- && linux_fork_checkpointing_p (lp->ptid.pid ()))
- {
- /* Handle checkpointing by linux-fork.c here as a special
- case. We don't want the follow-fork-mode or 'catch fork'
- to interfere with this. */
- /* This won't actually modify the breakpoint list, but will
- physically remove the breakpoints from the child. */
- detach_breakpoints (ptid_t (new_pid, new_pid));
- /* Retain child fork in ptrace (stopped) state. */
- if (!find_fork_pid (new_pid))
- add_fork (new_pid);
- /* Report as spurious, so that infrun doesn't want to follow
- this fork. We're actually doing an infcall in
- linux-fork.c. */
- ourstatus->set_spurious ();
- /* Report the stop to the core. */
- return 0;
- }
- if (event == PTRACE_EVENT_FORK)
- ourstatus->set_forked (child_ptid);
- else if (event == PTRACE_EVENT_VFORK)
- ourstatus->set_vforked (child_ptid);
- else if (event == PTRACE_EVENT_CLONE)
- {
- struct lwp_info *new_lp;
- ourstatus->set_ignore ();
- linux_nat_debug_printf
- ("Got clone event from LWP %d, new child is LWP %ld", pid, new_pid);
- new_lp = add_lwp (ptid_t (lp->ptid.pid (), new_pid));
- new_lp->stopped = 1;
- new_lp->resumed = 1;
- /* If the thread_db layer is active, let it record the user
- level thread id and status, and add the thread to GDB's
- list. */
- if (!thread_db_notice_clone (lp->ptid, new_lp->ptid))
- {
- /* The process is not using thread_db. Add the LWP to
- GDB's list. */
- target_post_attach (new_lp->ptid.lwp ());
- add_thread (linux_target, new_lp->ptid);
- }
- /* Even if we're stopping the thread for some reason
- internal to this module, from the perspective of infrun
- and the user/frontend, this new thread is running until
- it next reports a stop. */
- set_running (linux_target, new_lp->ptid, true);
- set_executing (linux_target, new_lp->ptid, true);
- if (WSTOPSIG (status) != SIGSTOP)
- {
- /* This can happen if someone starts sending signals to
- the new thread before it gets a chance to run, which
- have a lower number than SIGSTOP (e.g. SIGUSR1).
- This is an unlikely case, and harder to handle for
- fork / vfork than for clone, so we do not try - but
- we handle it for clone events here. */
- new_lp->signalled = 1;
- /* We created NEW_LP so it cannot yet contain STATUS. */
- gdb_assert (new_lp->status == 0);
- /* Save the wait status to report later. */
- linux_nat_debug_printf
- ("waitpid of new LWP %ld, saving status %s",
- (long) new_lp->ptid.lwp (), status_to_str (status).c_str ());
- new_lp->status = status;
- }
- else if (report_thread_events)
- {
- new_lp->waitstatus.set_thread_created ();
- new_lp->status = status;
- }
- return 1;
- }
- return 0;
- }
- if (event == PTRACE_EVENT_EXEC)
- {
- linux_nat_debug_printf ("Got exec event from LWP %ld", lp->ptid.lwp ());
- /* Close the previous /proc/PID/mem file for this inferior,
- which was using the address space which is now gone.
- Reading/writing from this file would return 0/EOF. */
- close_proc_mem_file (lp->ptid.pid ());
- /* Open a new file for the new address space. */
- open_proc_mem_file (lp->ptid);
- ourstatus->set_execd
- (make_unique_xstrdup (linux_proc_pid_to_exec_file (pid)));
- /* The thread that execed must have been resumed, but, when a
- thread execs, it changes its tid to the tgid, and the old
- tgid thread might have not been resumed. */
- lp->resumed = 1;
- return 0;
- }
- if (event == PTRACE_EVENT_VFORK_DONE)
- {
- linux_nat_debug_printf
- ("Got PTRACE_EVENT_VFORK_DONE from LWP %ld",
- lp->ptid.lwp ());
- ourstatus->set_vfork_done ();
- return 0;
- }
- internal_error (__FILE__, __LINE__,
- _("unknown ptrace event %d"), event);
- }
- /* Suspend waiting for a signal. We're mostly interested in
- SIGCHLD/SIGINT. */
- static void
- wait_for_signal ()
- {
- linux_nat_debug_printf ("about to sigsuspend");
- sigsuspend (&suspend_mask);
- /* If the quit flag is set, it means that the user pressed Ctrl-C
- and we're debugging a process that is running on a separate
- terminal, so we must forward the Ctrl-C to the inferior. (If the
- inferior is sharing GDB's terminal, then the Ctrl-C reaches the
- inferior directly.) We must do this here because functions that
- need to block waiting for a signal loop forever until there's an
- event to report before returning back to the event loop. */
- if (!target_terminal::is_ours ())
- {
- if (check_quit_flag ())
- target_pass_ctrlc ();
- }
- }
- /* Wait for LP to stop. Returns the wait status, or 0 if the LWP has
- exited. */
- static int
- wait_lwp (struct lwp_info *lp)
- {
- pid_t pid;
- int status = 0;
- int thread_dead = 0;
- sigset_t prev_mask;
- gdb_assert (!lp->stopped);
- gdb_assert (lp->status == 0);
- /* Make sure SIGCHLD is blocked for sigsuspend avoiding a race below. */
- block_child_signals (&prev_mask);
- for (;;)
- {
- pid = my_waitpid (lp->ptid.lwp (), &status, __WALL | WNOHANG);
- if (pid == -1 && errno == ECHILD)
- {
- /* The thread has previously exited. We need to delete it
- now because if this was a non-leader thread execing, we
- won't get an exit event. See comments on exec events at
- the top of the file. */
- thread_dead = 1;
- linux_nat_debug_printf ("%s vanished.",
- lp->ptid.to_string ().c_str ());
- }
- if (pid != 0)
- break;
- /* Bugs 10970, 12702.
- Thread group leader may have exited in which case we'll lock up in
- waitpid if there are other threads, even if they are all zombies too.
- Basically, we're not supposed to use waitpid this way.
- tkill(pid,0) cannot be used here as it gets ESRCH for both
- for zombie and running processes.
- As a workaround, check if we're waiting for the thread group leader and
- if it's a zombie, and avoid calling waitpid if it is.
- This is racy, what if the tgl becomes a zombie right after we check?
- Therefore always use WNOHANG with sigsuspend - it is equivalent to
- waiting waitpid but linux_proc_pid_is_zombie is safe this way. */
- if (lp->ptid.pid () == lp->ptid.lwp ()
- && linux_proc_pid_is_zombie (lp->ptid.lwp ()))
- {
- thread_dead = 1;
- linux_nat_debug_printf ("Thread group leader %s vanished.",
- lp->ptid.to_string ().c_str ());
- break;
- }
- /* Wait for next SIGCHLD and try again. This may let SIGCHLD handlers
- get invoked despite our caller had them intentionally blocked by
- block_child_signals. This is sensitive only to the loop of
- linux_nat_wait_1 and there if we get called my_waitpid gets called
- again before it gets to sigsuspend so we can safely let the handlers
- get executed here. */
- wait_for_signal ();
- }
- restore_child_signals_mask (&prev_mask);
- if (!thread_dead)
- {
- gdb_assert (pid == lp->ptid.lwp ());
- linux_nat_debug_printf ("waitpid %s received %s",
- lp->ptid.to_string ().c_str (),
- status_to_str (status).c_str ());
- /* Check if the thread has exited. */
- if (WIFEXITED (status) || WIFSIGNALED (status))
- {
- if (report_thread_events
- || lp->ptid.pid () == lp->ptid.lwp ())
- {
- linux_nat_debug_printf ("LWP %d exited.", lp->ptid.pid ());
- /* If this is the leader exiting, it means the whole
- process is gone. Store the status to report to the
- core. Store it in lp->waitstatus, because lp->status
- would be ambiguous (W_EXITCODE(0,0) == 0). */
- lp->waitstatus = host_status_to_waitstatus (status);
- return 0;
- }
- thread_dead = 1;
- linux_nat_debug_printf ("%s exited.",
- lp->ptid.to_string ().c_str ());
- }
- }
- if (thread_dead)
- {
- exit_lwp (lp);
- return 0;
- }
- gdb_assert (WIFSTOPPED (status));
- lp->stopped = 1;
- if (lp->must_set_ptrace_flags)
- {
- inferior *inf = find_inferior_pid (linux_target, lp->ptid.pid ());
- int options = linux_nat_ptrace_options (inf->attach_flag);
- linux_enable_event_reporting (lp->ptid.lwp (), options);
- lp->must_set_ptrace_flags = 0;
- }
- /* Handle GNU/Linux's syscall SIGTRAPs. */
- if (WIFSTOPPED (status) && WSTOPSIG (status) == SYSCALL_SIGTRAP)
- {
- /* No longer need the sysgood bit. The ptrace event ends up
- recorded in lp->waitstatus if we care for it. We can carry
- on handling the event like a regular SIGTRAP from here
- on. */
- status = W_STOPCODE (SIGTRAP);
- if (linux_handle_syscall_trap (lp, 1))
- return wait_lwp (lp);
- }
- else
- {
- /* Almost all other ptrace-stops are known to be outside of system
- calls, with further exceptions in linux_handle_extended_wait. */
- lp->syscall_state = TARGET_WAITKIND_IGNORE;
- }
- /* Handle GNU/Linux's extended waitstatus for trace events. */
- if (WIFSTOPPED (status) && WSTOPSIG (status) == SIGTRAP
- && linux_is_extended_waitstatus (status))
- {
- linux_nat_debug_printf ("Handling extended status 0x%06x", status);
- linux_handle_extended_wait (lp, status);
- return 0;
- }
- return status;
- }
- /* Send a SIGSTOP to LP. */
- static int
- stop_callback (struct lwp_info *lp)
- {
- if (!lp->stopped && !lp->signalled)
- {
- int ret;
- linux_nat_debug_printf ("kill %s **<SIGSTOP>**",
- lp->ptid.to_string ().c_str ());
- errno = 0;
- ret = kill_lwp (lp->ptid.lwp (), SIGSTOP);
- linux_nat_debug_printf ("lwp kill %d %s", ret,
- errno ? safe_strerror (errno) : "ERRNO-OK");
- lp->signalled = 1;
- gdb_assert (lp->status == 0);
- }
- return 0;
- }
- /* Request a stop on LWP. */
- void
- linux_stop_lwp (struct lwp_info *lwp)
- {
- stop_callback (lwp);
- }
- /* See linux-nat.h */
- void
- linux_stop_and_wait_all_lwps (void)
- {
- /* Stop all LWP's ... */
- iterate_over_lwps (minus_one_ptid, stop_callback);
- /* ... and wait until all of them have reported back that
- they're no longer running. */
- iterate_over_lwps (minus_one_ptid, stop_wait_callback);
- }
- /* See linux-nat.h */
- void
- linux_unstop_all_lwps (void)
- {
- iterate_over_lwps (minus_one_ptid,
- [] (struct lwp_info *info)
- {
- return resume_stopped_resumed_lwps (info, minus_one_ptid);
- });
- }
- /* Return non-zero if LWP PID has a pending SIGINT. */
- static int
- linux_nat_has_pending_sigint (int pid)
- {
- sigset_t pending, blocked, ignored;
- linux_proc_pending_signals (pid, &pending, &blocked, &ignored);
- if (sigismember (&pending, SIGINT)
- && !sigismember (&ignored, SIGINT))
- return 1;
- return 0;
- }
- /* Set a flag in LP indicating that we should ignore its next SIGINT. */
- static int
- set_ignore_sigint (struct lwp_info *lp)
- {
- /* If a thread has a pending SIGINT, consume it; otherwise, set a
- flag to consume the next one. */
- if (lp->stopped && lp->status != 0 && WIFSTOPPED (lp->status)
- && WSTOPSIG (lp->status) == SIGINT)
- lp->status = 0;
- else
- lp->ignore_sigint = 1;
- return 0;
- }
- /* If LP does not have a SIGINT pending, then clear the ignore_sigint flag.
- This function is called after we know the LWP has stopped; if the LWP
- stopped before the expected SIGINT was delivered, then it will never have
- arrived. Also, if the signal was delivered to a shared queue and consumed
- by a different thread, it will never be delivered to this LWP. */
- static void
- maybe_clear_ignore_sigint (struct lwp_info *lp)
- {
- if (!lp->ignore_sigint)
- return;
- if (!linux_nat_has_pending_sigint (lp->ptid.lwp ()))
- {
- linux_nat_debug_printf ("Clearing bogus flag for %s",
- lp->ptid.to_string ().c_str ());
- lp->ignore_sigint = 0;
- }
- }
- /* Fetch the possible triggered data watchpoint info and store it in
- LP.
- On some archs, like x86, that use debug registers to set
- watchpoints, it's possible that the way to know which watched
- address trapped, is to check the register that is used to select
- which address to watch. Problem is, between setting the watchpoint
- and reading back which data address trapped, the user may change
- the set of watchpoints, and, as a consequence, GDB changes the
- debug registers in the inferior. To avoid reading back a stale
- stopped-data-address when that happens, we cache in LP the fact
- that a watchpoint trapped, and the corresponding data address, as
- soon as we see LP stop with a SIGTRAP. If GDB changes the debug
- registers meanwhile, we have the cached data we can rely on. */
- static int
- check_stopped_by_watchpoint (struct lwp_info *lp)
- {
- scoped_restore save_inferior_ptid = make_scoped_restore (&inferior_ptid);
- inferior_ptid = lp->ptid;
- if (linux_target->low_stopped_by_watchpoint ())
- {
- lp->stop_reason = TARGET_STOPPED_BY_WATCHPOINT;
- lp->stopped_data_address_p
- = linux_target->low_stopped_data_address (&lp->stopped_data_address);
- }
- return lp->stop_reason == TARGET_STOPPED_BY_WATCHPOINT;
- }
- /* Returns true if the LWP had stopped for a watchpoint. */
- bool
- linux_nat_target::stopped_by_watchpoint ()
- {
- struct lwp_info *lp = find_lwp_pid (inferior_ptid);
- gdb_assert (lp != NULL);
- return lp->stop_reason == TARGET_STOPPED_BY_WATCHPOINT;
- }
- bool
- linux_nat_target::stopped_data_address (CORE_ADDR *addr_p)
- {
- struct lwp_info *lp = find_lwp_pid (inferior_ptid);
- gdb_assert (lp != NULL);
- *addr_p = lp->stopped_data_address;
- return lp->stopped_data_address_p;
- }
- /* Commonly any breakpoint / watchpoint generate only SIGTRAP. */
- bool
- linux_nat_target::low_status_is_event (int status)
- {
- return WIFSTOPPED (status) && WSTOPSIG (status) == SIGTRAP;
- }
- /* Wait until LP is stopped. */
- static int
- stop_wait_callback (struct lwp_info *lp)
- {
- inferior *inf = find_inferior_ptid (linux_target, lp->ptid);
- /* If this is a vfork parent, bail out, it is not going to report
- any SIGSTOP until the vfork is done with. */
- if (inf->vfork_child != NULL)
- return 0;
- if (!lp->stopped)
- {
- int status;
- status = wait_lwp (lp);
- if (status == 0)
- return 0;
- if (lp->ignore_sigint && WIFSTOPPED (status)
- && WSTOPSIG (status) == SIGINT)
- {
- lp->ignore_sigint = 0;
- errno = 0;
- ptrace (PTRACE_CONT, lp->ptid.lwp (), 0, 0);
- lp->stopped = 0;
- linux_nat_debug_printf
- ("PTRACE_CONT %s, 0, 0 (%s) (discarding SIGINT)",
- lp->ptid.to_string ().c_str (),
- errno ? safe_strerror (errno) : "OK");
- return stop_wait_callback (lp);
- }
- maybe_clear_ignore_sigint (lp);
- if (WSTOPSIG (status) != SIGSTOP)
- {
- /* The thread was stopped with a signal other than SIGSTOP. */
- linux_nat_debug_printf ("Pending event %s in %s",
- status_to_str ((int) status).c_str (),
- lp->ptid.to_string ().c_str ());
- /* Save the sigtrap event. */
- lp->status = status;
- gdb_assert (lp->signalled);
- save_stop_reason (lp);
- }
- else
- {
- /* We caught the SIGSTOP that we intended to catch. */
- linux_nat_debug_printf ("Expected SIGSTOP caught for %s.",
- lp->ptid.to_string ().c_str ());
- lp->signalled = 0;
- /* If we are waiting for this stop so we can report the thread
- stopped then we need to record this status. Otherwise, we can
- now discard this stop event. */
- if (lp->last_resume_kind == resume_stop)
- {
- lp->status = status;
- save_stop_reason (lp);
- }
- }
- }
- return 0;
- }
- /* Return non-zero if LP has a wait status pending. Discard the
- pending event and resume the LWP if the event that originally
- caused the stop became uninteresting. */
- static int
- status_callback (struct lwp_info *lp)
- {
- /* Only report a pending wait status if we pretend that this has
- indeed been resumed. */
- if (!lp->resumed)
- return 0;
- if (!lwp_status_pending_p (lp))
- return 0;
- if (lp->stop_reason == TARGET_STOPPED_BY_SW_BREAKPOINT
- || lp->stop_reason == TARGET_STOPPED_BY_HW_BREAKPOINT)
- {
- struct regcache *regcache = get_thread_regcache (linux_target, lp->ptid);
- CORE_ADDR pc;
- int discard = 0;
- pc = regcache_read_pc (regcache);
- if (pc != lp->stop_pc)
- {
- linux_nat_debug_printf ("PC of %s changed. was=%s, now=%s",
- lp->ptid.to_string ().c_str (),
- paddress (target_gdbarch (), lp->stop_pc),
- paddress (target_gdbarch (), pc));
- discard = 1;
- }
- #if !USE_SIGTRAP_SIGINFO
- else if (!breakpoint_inserted_here_p (regcache->aspace (), pc))
- {
- linux_nat_debug_printf ("previous breakpoint of %s, at %s gone",
- lp->ptid.to_string ().c_str (),
- paddress (target_gdbarch (), lp->stop_pc));
- discard = 1;
- }
- #endif
- if (discard)
- {
- linux_nat_debug_printf ("pending event of %s cancelled.",
- lp->ptid.to_string ().c_str ());
- lp->status = 0;
- linux_resume_one_lwp (lp, lp->step, GDB_SIGNAL_0);
- return 0;
- }
- }
- return 1;
- }
- /* Count the LWP's that have had events. */
- static int
- count_events_callback (struct lwp_info *lp, int *count)
- {
- gdb_assert (count != NULL);
- /* Select only resumed LWPs that have an event pending. */
- if (lp->resumed && lwp_status_pending_p (lp))
- (*count)++;
- return 0;
- }
- /* Select the LWP (if any) that is currently being single-stepped. */
- static int
- select_singlestep_lwp_callback (struct lwp_info *lp)
- {
- if (lp->last_resume_kind == resume_step
- && lp->status != 0)
- return 1;
- else
- return 0;
- }
- /* Returns true if LP has a status pending. */
- static int
- lwp_status_pending_p (struct lwp_info *lp)
- {
- /* We check for lp->waitstatus in addition to lp->status, because we
- can have pending process exits recorded in lp->status and
- W_EXITCODE(0,0) happens to be 0. */
- return lp->status != 0 || lp->waitstatus.kind () != TARGET_WAITKIND_IGNORE;
- }
- /* Select the Nth LWP that has had an event. */
- static int
- select_event_lwp_callback (struct lwp_info *lp, int *selector)
- {
- gdb_assert (selector != NULL);
- /* Select only resumed LWPs that have an event pending. */
- if (lp->resumed && lwp_status_pending_p (lp))
- if ((*selector)-- == 0)
- return 1;
- return 0;
- }
- /* Called when the LWP stopped for a signal/trap. If it stopped for a
- trap check what caused it (breakpoint, watchpoint, trace, etc.),
- and save the result in the LWP's stop_reason field. If it stopped
- for a breakpoint, decrement the PC if necessary on the lwp's
- architecture. */
- static void
- save_stop_reason (struct lwp_info *lp)
- {
- struct regcache *regcache;
- struct gdbarch *gdbarch;
- CORE_ADDR pc;
- CORE_ADDR sw_bp_pc;
- #if USE_SIGTRAP_SIGINFO
- siginfo_t siginfo;
- #endif
- gdb_assert (lp->stop_reason == TARGET_STOPPED_BY_NO_REASON);
- gdb_assert (lp->status != 0);
- if (!linux_target->low_status_is_event (lp->status))
- return;
- regcache = get_thread_regcache (linux_target, lp->ptid);
- gdbarch = regcache->arch ();
- pc = regcache_read_pc (regcache);
- sw_bp_pc = pc - gdbarch_decr_pc_after_break (gdbarch);
- #if USE_SIGTRAP_SIGINFO
- if (linux_nat_get_siginfo (lp->ptid, &siginfo))
- {
- if (siginfo.si_signo == SIGTRAP)
- {
- if (GDB_ARCH_IS_TRAP_BRKPT (siginfo.si_code)
- && GDB_ARCH_IS_TRAP_HWBKPT (siginfo.si_code))
- {
- /* The si_code is ambiguous on this arch -- check debug
- registers. */
- if (!check_stopped_by_watchpoint (lp))
- lp->stop_reason = TARGET_STOPPED_BY_SW_BREAKPOINT;
- }
- else if (GDB_ARCH_IS_TRAP_BRKPT (siginfo.si_code))
- {
- /* If we determine the LWP stopped for a SW breakpoint,
- trust it. Particularly don't check watchpoint
- registers, because, at least on s390, we'd find
- stopped-by-watchpoint as long as there's a watchpoint
- set. */
- lp->stop_reason = TARGET_STOPPED_BY_SW_BREAKPOINT;
- }
- else if (GDB_ARCH_IS_TRAP_HWBKPT (siginfo.si_code))
- {
- /* This can indicate either a hardware breakpoint or
- hardware watchpoint. Check debug registers. */
- if (!check_stopped_by_watchpoint (lp))
- lp->stop_reason = TARGET_STOPPED_BY_HW_BREAKPOINT;
- }
- else if (siginfo.si_code == TRAP_TRACE)
- {
- linux_nat_debug_printf ("%s stopped by trace",
- lp->ptid.to_string ().c_str ());
- /* We may have single stepped an instruction that
- triggered a watchpoint. In that case, on some
- architectures (such as x86), instead of TRAP_HWBKPT,
- si_code indicates TRAP_TRACE, and we need to check
- the debug registers separately. */
- check_stopped_by_watchpoint (lp);
- }
- }
- }
- #else
- if ((!lp->step || lp->stop_pc == sw_bp_pc)
- && software_breakpoint_inserted_here_p (regcache->aspace (),
- sw_bp_pc))
- {
- /* The LWP was either continued, or stepped a software
- breakpoint instruction. */
- lp->stop_reason = TARGET_STOPPED_BY_SW_BREAKPOINT;
- }
- if (hardware_breakpoint_inserted_here_p (regcache->aspace (), pc))
- lp->stop_reason = TARGET_STOPPED_BY_HW_BREAKPOINT;
- if (lp->stop_reason == TARGET_STOPPED_BY_NO_REASON)
- check_stopped_by_watchpoint (lp);
- #endif
- if (lp->stop_reason == TARGET_STOPPED_BY_SW_BREAKPOINT)
- {
- linux_nat_debug_printf ("%s stopped by software breakpoint",
- lp->ptid.to_string ().c_str ());
- /* Back up the PC if necessary. */
- if (pc != sw_bp_pc)
- regcache_write_pc (regcache, sw_bp_pc);
- /* Update this so we record the correct stop PC below. */
- pc = sw_bp_pc;
- }
- else if (lp->stop_reason == TARGET_STOPPED_BY_HW_BREAKPOINT)
- {
- linux_nat_debug_printf ("%s stopped by hardware breakpoint",
- lp->ptid.to_string ().c_str ());
- }
- else if (lp->stop_reason == TARGET_STOPPED_BY_WATCHPOINT)
- {
- linux_nat_debug_printf ("%s stopped by hardware watchpoint",
- lp->ptid.to_string ().c_str ());
- }
- lp->stop_pc = pc;
- }
- /* Returns true if the LWP had stopped for a software breakpoint. */
- bool
- linux_nat_target::stopped_by_sw_breakpoint ()
- {
- struct lwp_info *lp = find_lwp_pid (inferior_ptid);
- gdb_assert (lp != NULL);
- return lp->stop_reason == TARGET_STOPPED_BY_SW_BREAKPOINT;
- }
- /* Implement the supports_stopped_by_sw_breakpoint method. */
- bool
- linux_nat_target::supports_stopped_by_sw_breakpoint ()
- {
- return USE_SIGTRAP_SIGINFO;
- }
- /* Returns true if the LWP had stopped for a hardware
- breakpoint/watchpoint. */
- bool
- linux_nat_target::stopped_by_hw_breakpoint ()
- {
- struct lwp_info *lp = find_lwp_pid (inferior_ptid);
- gdb_assert (lp != NULL);
- return lp->stop_reason == TARGET_STOPPED_BY_HW_BREAKPOINT;
- }
- /* Implement the supports_stopped_by_hw_breakpoint method. */
- bool
- linux_nat_target::supports_stopped_by_hw_breakpoint ()
- {
- return USE_SIGTRAP_SIGINFO;
- }
- /* Select one LWP out of those that have events pending. */
- static void
- select_event_lwp (ptid_t filter, struct lwp_info **orig_lp, int *status)
- {
- int num_events = 0;
- int random_selector;
- struct lwp_info *event_lp = NULL;
- /* Record the wait status for the original LWP. */
- (*orig_lp)->status = *status;
- /* In all-stop, give preference to the LWP that is being
- single-stepped. There will be at most one, and it will be the
- LWP that the core is most interested in. If we didn't do this,
- then we'd have to handle pending step SIGTRAPs somehow in case
- the core later continues the previously-stepped thread, as
- otherwise we'd report the pending SIGTRAP then, and the core, not
- having stepped the thread, wouldn't understand what the trap was
- for, and therefore would report it to the user as a random
- signal. */
- if (!target_is_non_stop_p ())
- {
- event_lp = iterate_over_lwps (filter, select_singlestep_lwp_callback);
- if (event_lp != NULL)
- {
- linux_nat_debug_printf ("Select single-step %s",
- event_lp->ptid.to_string ().c_str ());
- }
- }
- if (event_lp == NULL)
- {
- /* Pick one at random, out of those which have had events. */
- /* First see how many events we have. */
- iterate_over_lwps (filter,
- [&] (struct lwp_info *info)
- {
- return count_events_callback (info, &num_events);
- });
- gdb_assert (num_events > 0);
- /* Now randomly pick a LWP out of those that have had
- events. */
- random_selector = (int)
- ((num_events * (double) rand ()) / (RAND_MAX + 1.0));
- if (num_events > 1)
- linux_nat_debug_printf ("Found %d events, selecting #%d",
- num_events, random_selector);
- event_lp
- = (iterate_over_lwps
- (filter,
- [&] (struct lwp_info *info)
- {
- return select_event_lwp_callback (info,
- &random_selector);
- }));
- }
- if (event_lp != NULL)
- {
- /* Switch the event LWP. */
- *orig_lp = event_lp;
- *status = event_lp->status;
- }
- /* Flush the wait status for the event LWP. */
- (*orig_lp)->status = 0;
- }
- /* Return non-zero if LP has been resumed. */
- static int
- resumed_callback (struct lwp_info *lp)
- {
- return lp->resumed;
- }
- /* Check if we should go on and pass this event to common code.
- If so, save the status to the lwp_info structure associated to LWPID. */
- static void
- linux_nat_filter_event (int lwpid, int status)
- {
- struct lwp_info *lp;
- int event = linux_ptrace_get_extended_event (status);
- lp = find_lwp_pid (ptid_t (lwpid));
- /* Check for events reported by anything not in our LWP list. */
- if (lp == nullptr)
- {
- if (WIFSTOPPED (status))
- {
- if (WSTOPSIG (status) == SIGTRAP && event == PTRACE_EVENT_EXEC)
- {
- /* A non-leader thread exec'ed after we've seen the
- leader zombie, and removed it from our lists (in
- check_zombie_leaders). The non-leader thread changes
- its tid to the tgid. */
- linux_nat_debug_printf
- ("Re-adding thread group leader LWP %d after exec.",
- lwpid);
- lp = add_lwp (ptid_t (lwpid, lwpid));
- lp->stopped = 1;
- lp->resumed = 1;
- add_thread (linux_target, lp->ptid);
- }
- else
- {
- /* A process we are controlling has forked and the new
- child's stop was reported to us by the kernel. Save
- its PID and go back to waiting for the fork event to
- be reported - the stopped process might be returned
- from waitpid before or after the fork event is. */
- linux_nat_debug_printf
- ("Saving LWP %d status %s in stopped_pids list",
- lwpid, status_to_str (status).c_str ());
- add_to_pid_list (&stopped_pids, lwpid, status);
- }
- }
- else
- {
- /* Don't report an event for the exit of an LWP not in our
- list, i.e. not part of any inferior we're debugging.
- This can happen if we detach from a program we originally
- forked and then it exits. However, note that we may have
- earlier deleted a leader of an inferior we're debugging,
- in check_zombie_leaders. Re-add it back here if so. */
- for (inferior *inf : all_inferiors (linux_target))
- {
- if (inf->pid == lwpid)
- {
- linux_nat_debug_printf
- ("Re-adding thread group leader LWP %d after exit.",
- lwpid);
- lp = add_lwp (ptid_t (lwpid, lwpid));
- lp->resumed = 1;
- add_thread (linux_target, lp->ptid);
- break;
- }
- }
- }
- if (lp == nullptr)
- return;
- }
- /* This LWP is stopped now. (And if dead, this prevents it from
- ever being continued.) */
- lp->stopped = 1;
- if (WIFSTOPPED (status) && lp->must_set_ptrace_flags)
- {
- inferior *inf = find_inferior_pid (linux_target, lp->ptid.pid ());
- int options = linux_nat_ptrace_options (inf->attach_flag);
- linux_enable_event_reporting (lp->ptid.lwp (), options);
- lp->must_set_ptrace_flags = 0;
- }
- /* Handle GNU/Linux's syscall SIGTRAPs. */
- if (WIFSTOPPED (status) && WSTOPSIG (status) == SYSCALL_SIGTRAP)
- {
- /* No longer need the sysgood bit. The ptrace event ends up
- recorded in lp->waitstatus if we care for it. We can carry
- on handling the event like a regular SIGTRAP from here
- on. */
- status = W_STOPCODE (SIGTRAP);
- if (linux_handle_syscall_trap (lp, 0))
- return;
- }
- else
- {
- /* Almost all other ptrace-stops are known to be outside of system
- calls, with further exceptions in linux_handle_extended_wait. */
- lp->syscall_state = TARGET_WAITKIND_IGNORE;
- }
- /* Handle GNU/Linux's extended waitstatus for trace events. */
- if (WIFSTOPPED (status) && WSTOPSIG (status) == SIGTRAP
- && linux_is_extended_waitstatus (status))
- {
- linux_nat_debug_printf ("Handling extended status 0x%06x", status);
- if (linux_handle_extended_wait (lp, status))
- return;
- }
- /* Check if the thread has exited. */
- if (WIFEXITED (status) || WIFSIGNALED (status))
- {
- if (!report_thread_events && !is_leader (lp))
- {
- linux_nat_debug_printf ("%s exited.",
- lp->ptid.to_string ().c_str ());
- /* If this was not the leader exiting, then the exit signal
- was not the end of the debugged application and should be
- ignored. */
- exit_lwp (lp);
- return;
- }
- /* Note that even if the leader was ptrace-stopped, it can still
- exit, if e.g., some other thread brings down the whole
- process (calls `exit'). So don't assert that the lwp is
- resumed. */
- linux_nat_debug_printf ("LWP %ld exited (resumed=%d)",
- lp->ptid.lwp (), lp->resumed);
- /* Dead LWP's aren't expected to reported a pending sigstop. */
- lp->signalled = 0;
- /* Store the pending event in the waitstatus, because
- W_EXITCODE(0,0) == 0. */
- lp->waitstatus = host_status_to_waitstatus (status);
- return;
- }
- /* Make sure we don't report a SIGSTOP that we sent ourselves in
- an attempt to stop an LWP. */
- if (lp->signalled
- && WIFSTOPPED (status) && WSTOPSIG (status) == SIGSTOP)
- {
- lp->signalled = 0;
- if (lp->last_resume_kind == resume_stop)
- {
- linux_nat_debug_printf ("resume_stop SIGSTOP caught for %s.",
- lp->ptid.to_string ().c_str ());
- }
- else
- {
- /* This is a delayed SIGSTOP. Filter out the event. */
- linux_nat_debug_printf
- ("%s %s, 0, 0 (discard delayed SIGSTOP)",
- lp->step ? "PTRACE_SINGLESTEP" : "PTRACE_CONT",
- lp->ptid.to_string ().c_str ());
- linux_resume_one_lwp (lp, lp->step, GDB_SIGNAL_0);
- gdb_assert (lp->resumed);
- return;
- }
- }
- /* Make sure we don't report a SIGINT that we have already displayed
- for another thread. */
- if (lp->ignore_sigint
- && WIFSTOPPED (status) && WSTOPSIG (status) == SIGINT)
- {
- linux_nat_debug_printf ("Delayed SIGINT caught for %s.",
- lp->ptid.to_string ().c_str ());
- /* This is a delayed SIGINT. */
- lp->ignore_sigint = 0;
- linux_resume_one_lwp (lp, lp->step, GDB_SIGNAL_0);
- linux_nat_debug_printf ("%s %s, 0, 0 (discard SIGINT)",
- lp->step ? "PTRACE_SINGLESTEP" : "PTRACE_CONT",
- lp->ptid.to_string ().c_str ());
- gdb_assert (lp->resumed);
- /* Discard the event. */
- return;
- }
- /* Don't report signals that GDB isn't interested in, such as
- signals that are neither printed nor stopped upon. Stopping all
- threads can be a bit time-consuming, so if we want decent
- performance with heavily multi-threaded programs, especially when
- they're using a high frequency timer, we'd better avoid it if we
- can. */
- if (WIFSTOPPED (status))
- {
- enum gdb_signal signo = gdb_signal_from_host (WSTOPSIG (status));
- if (!target_is_non_stop_p ())
- {
- /* Only do the below in all-stop, as we currently use SIGSTOP
- to implement target_stop (see linux_nat_stop) in
- non-stop. */
- if (signo == GDB_SIGNAL_INT && signal_pass_state (signo) == 0)
- {
- /* If ^C/BREAK is typed at the tty/console, SIGINT gets
- forwarded to the entire process group, that is, all LWPs
- will receive it - unless they're using CLONE_THREAD to
- share signals. Since we only want to report it once, we
- mark it as ignored for all LWPs except this one. */
- iterate_over_lwps (ptid_t (lp->ptid.pid ()), set_ignore_sigint);
- lp->ignore_sigint = 0;
- }
- else
- maybe_clear_ignore_sigint (lp);
- }
- /* When using hardware single-step, we need to report every signal.
- Otherwise, signals in pass_mask may be short-circuited
- except signals that might be caused by a breakpoint, or SIGSTOP
- if we sent the SIGSTOP and are waiting for it to arrive. */
- if (!lp->step
- && WSTOPSIG (status) && sigismember (&pass_mask, WSTOPSIG (status))
- && (WSTOPSIG (status) != SIGSTOP
- || !find_thread_ptid (linux_target, lp->ptid)->stop_requested)
- && !linux_wstatus_maybe_breakpoint (status))
- {
- linux_resume_one_lwp (lp, lp->step, signo);
- linux_nat_debug_printf
- ("%s %s, %s (preempt 'handle')",
- lp->step ? "PTRACE_SINGLESTEP" : "PTRACE_CONT",
- lp->ptid.to_string ().c_str (),
- (signo != GDB_SIGNAL_0
- ? strsignal (gdb_signal_to_host (signo)) : "0"));
- return;
- }
- }
- /* An interesting event. */
- gdb_assert (lp);
- lp->status = status;
- save_stop_reason (lp);
- }
- /* Detect zombie thread group leaders, and "exit" them. We can't reap
- their exits until all other threads in the group have exited. */
- static void
- check_zombie_leaders (void)
- {
- for (inferior *inf : all_inferiors ())
- {
- struct lwp_info *leader_lp;
- if (inf->pid == 0)
- continue;
- leader_lp = find_lwp_pid (ptid_t (inf->pid));
- if (leader_lp != NULL
- /* Check if there are other threads in the group, as we may
- have raced with the inferior simply exiting. Note this
- isn't a watertight check. If the inferior is
- multi-threaded and is exiting, it may be we see the
- leader as zombie before we reap all the non-leader
- threads. See comments below. */
- && num_lwps (inf->pid) > 1
- && linux_proc_pid_is_zombie (inf->pid))
- {
- /* A zombie leader in a multi-threaded program can mean one
- of three things:
- #1 - Only the leader exited, not the whole program, e.g.,
- with pthread_exit. Since we can't reap the leader's exit
- status until all other threads are gone and reaped too,
- we want to delete the zombie leader right away, as it
- can't be debugged, we can't read its registers, etc.
- This is the main reason we check for zombie leaders
- disappearing.
- #2 - The whole thread-group/process exited (a group exit,
- via e.g. exit(3), and there is (or will be shortly) an
- exit reported for each thread in the process, and then
- finally an exit for the leader once the non-leaders are
- reaped.
- #3 - There are 3 or more threads in the group, and a
- thread other than the leader exec'd. See comments on
- exec events at the top of the file.
- Ideally we would never delete the leader for case #2.
- Instead, we want to collect the exit status of each
- non-leader thread, and then finally collect the exit
- status of the leader as normal and use its exit code as
- whole-process exit code. Unfortunately, there's no
- race-free way to distinguish cases #1 and #2. We can't
- assume the exit events for the non-leaders threads are
- already pending in the kernel, nor can we assume the
- non-leader threads are in zombie state already. Between
- the leader becoming zombie and the non-leaders exiting
- and becoming zombie themselves, there's a small time
- window, so such a check would be racy. Temporarily
- pausing all threads and checking to see if all threads
- exit or not before re-resuming them would work in the
- case that all threads are running right now, but it
- wouldn't work if some thread is currently already
- ptrace-stopped, e.g., due to scheduler-locking.
- So what we do is we delete the leader anyhow, and then
- later on when we see its exit status, we re-add it back.
- We also make sure that we only report a whole-process
- exit when we see the leader exiting, as opposed to when
- the last LWP in the LWP list exits, which can be a
- non-leader if we deleted the leader here. */
- linux_nat_debug_printf ("Thread group leader %d zombie "
- "(it exited, or another thread execd), "
- "deleting it.",
- inf->pid);
- exit_lwp (leader_lp);
- }
- }
- }
- /* Convenience function that is called when the kernel reports an exit
- event. This decides whether to report the event to GDB as a
- process exit event, a thread exit event, or to suppress the
- event. */
- static ptid_t
- filter_exit_event (struct lwp_info *event_child,
- struct target_waitstatus *ourstatus)
- {
- ptid_t ptid = event_child->ptid;
- if (!is_leader (event_child))
- {
- if (report_thread_events)
- ourstatus->set_thread_exited (0);
- else
- ourstatus->set_ignore ();
- exit_lwp (event_child);
- }
- return ptid;
- }
- static ptid_t
- linux_nat_wait_1 (ptid_t ptid, struct target_waitstatus *ourstatus,
- target_wait_flags target_options)
- {
- sigset_t prev_mask;
- enum resume_kind last_resume_kind;
- struct lwp_info *lp;
- int status;
- linux_nat_debug_printf ("enter");
- /* The first time we get here after starting a new inferior, we may
- not have added it to the LWP list yet - this is the earliest
- moment at which we know its PID. */
- if (ptid.is_pid () && find_lwp_pid (ptid) == nullptr)
- {
- ptid_t lwp_ptid (ptid.pid (), ptid.pid ());
- /* Upgrade the main thread's ptid. */
- thread_change_ptid (linux_target, ptid, lwp_ptid);
- lp = add_initial_lwp (lwp_ptid);
- lp->resumed = 1;
- }
- /* Make sure SIGCHLD is blocked until the sigsuspend below. */
- block_child_signals (&prev_mask);
- /* First check if there is a LWP with a wait status pending. */
- lp = iterate_over_lwps (ptid, status_callback);
- if (lp != NULL)
- {
- linux_nat_debug_printf ("Using pending wait status %s for %s.",
- status_to_str (lp->status).c_str (),
- lp->ptid.to_string ().c_str ());
- }
- /* But if we don't find a pending event, we'll have to wait. Always
- pull all events out of the kernel. We'll randomly select an
- event LWP out of all that have events, to prevent starvation. */
- while (lp == NULL)
- {
- pid_t lwpid;
- /* Always use -1 and WNOHANG, due to couple of a kernel/ptrace
- quirks:
- - If the thread group leader exits while other threads in the
- thread group still exist, waitpid(TGID, ...) hangs. That
- waitpid won't return an exit status until the other threads
- in the group are reaped.
- - When a non-leader thread execs, that thread just vanishes
- without reporting an exit (so we'd hang if we waited for it
- explicitly in that case). The exec event is reported to
- the TGID pid. */
- errno = 0;
- lwpid = my_waitpid (-1, &status, __WALL | WNOHANG);
- linux_nat_debug_printf ("waitpid(-1, ...) returned %d, %s",
- lwpid,
- errno ? safe_strerror (errno) : "ERRNO-OK");
- if (lwpid > 0)
- {
- linux_nat_debug_printf ("waitpid %ld received %s",
- (long) lwpid,
- status_to_str (status).c_str ());
- linux_nat_filter_event (lwpid, status);
- /* Retry until nothing comes out of waitpid. A single
- SIGCHLD can indicate more than one child stopped. */
- continue;
- }
- /* Now that we've pulled all events out of the kernel, resume
- LWPs that don't have an interesting event to report. */
- iterate_over_lwps (minus_one_ptid,
- [] (struct lwp_info *info)
- {
- return resume_stopped_resumed_lwps (info, minus_one_ptid);
- });
- /* ... and find an LWP with a status to report to the core, if
- any. */
- lp = iterate_over_lwps (ptid, status_callback);
- if (lp != NULL)
- break;
- /* Check for zombie thread group leaders. Those can't be reaped
- until all other threads in the thread group are. */
- check_zombie_leaders ();
- /* If there are no resumed children left, bail. We'd be stuck
- forever in the sigsuspend call below otherwise. */
- if (iterate_over_lwps (ptid, resumed_callback) == NULL)
- {
- linux_nat_debug_printf ("exit (no resumed LWP)");
- ourstatus->set_no_resumed ();
- restore_child_signals_mask (&prev_mask);
- return minus_one_ptid;
- }
- /* No interesting event to report to the core. */
- if (target_options & TARGET_WNOHANG)
- {
- linux_nat_debug_printf ("exit (ignore)");
- ourstatus->set_ignore ();
- restore_child_signals_mask (&prev_mask);
- return minus_one_ptid;
- }
- /* We shouldn't end up here unless we want to try again. */
- gdb_assert (lp == NULL);
- /* Block until we get an event reported with SIGCHLD. */
- wait_for_signal ();
- }
- gdb_assert (lp);
- status = lp->status;
- lp->status = 0;
- if (!target_is_non_stop_p ())
- {
- /* Now stop all other LWP's ... */
- iterate_over_lwps (minus_one_ptid, stop_callback);
- /* ... and wait until all of them have reported back that
- they're no longer running. */
- iterate_over_lwps (minus_one_ptid, stop_wait_callback);
- }
- /* If we're not waiting for a specific LWP, choose an event LWP from
- among those that have had events. Giving equal priority to all
- LWPs that have had events helps prevent starvation. */
- if (ptid == minus_one_ptid || ptid.is_pid ())
- select_event_lwp (ptid, &lp, &status);
- gdb_assert (lp != NULL);
- /* Now that we've selected our final event LWP, un-adjust its PC if
- it was a software breakpoint, and we can't reliably support the
- "stopped by software breakpoint" stop reason. */
- if (lp->stop_reason == TARGET_STOPPED_BY_SW_BREAKPOINT
- && !USE_SIGTRAP_SIGINFO)
- {
- struct regcache *regcache = get_thread_regcache (linux_target, lp->ptid);
- struct gdbarch *gdbarch = regcache->arch ();
- int decr_pc = gdbarch_decr_pc_after_break (gdbarch);
- if (decr_pc != 0)
- {
- CORE_ADDR pc;
- pc = regcache_read_pc (regcache);
- regcache_write_pc (regcache, pc + decr_pc);
- }
- }
- /* We'll need this to determine whether to report a SIGSTOP as
- GDB_SIGNAL_0. Need to take a copy because resume_clear_callback
- clears it. */
- last_resume_kind = lp->last_resume_kind;
- if (!target_is_non_stop_p ())
- {
- /* In all-stop, from the core's perspective, all LWPs are now
- stopped until a new resume action is sent over. */
- iterate_over_lwps (minus_one_ptid, resume_clear_callback);
- }
- else
- {
- resume_clear_callback (lp);
- }
- if (linux_target->low_status_is_event (status))
- {
- linux_nat_debug_printf ("trap ptid is %s.",
- lp->ptid.to_string ().c_str ());
- }
- if (lp->waitstatus.kind () != TARGET_WAITKIND_IGNORE)
- {
- *ourstatus = lp->waitstatus;
- lp->waitstatus.set_ignore ();
- }
- else
- *ourstatus = host_status_to_waitstatus (status);
- linux_nat_debug_printf ("exit");
- restore_child_signals_mask (&prev_mask);
- if (last_resume_kind == resume_stop
- && ourstatus->kind () == TARGET_WAITKIND_STOPPED
- && WSTOPSIG (status) == SIGSTOP)
- {
- /* A thread that has been requested to stop by GDB with
- target_stop, and it stopped cleanly, so report as SIG0. The
- use of SIGSTOP is an implementation detail. */
- ourstatus->set_stopped (GDB_SIGNAL_0);
- }
- if (ourstatus->kind () == TARGET_WAITKIND_EXITED
- || ourstatus->kind () == TARGET_WAITKIND_SIGNALLED)
- lp->core = -1;
- else
- lp->core = linux_common_core_of_thread (lp->ptid);
- if (ourstatus->kind () == TARGET_WAITKIND_EXITED)
- return filter_exit_event (lp, ourstatus);
- return lp->ptid;
- }
- /* Resume LWPs that are currently stopped without any pending status
- to report, but are resumed from the core's perspective. */
- static int
- resume_stopped_resumed_lwps (struct lwp_info *lp, const ptid_t wait_ptid)
- {
- if (!lp->stopped)
- {
- linux_nat_debug_printf ("NOT resuming LWP %s, not stopped",
- lp->ptid.to_string ().c_str ());
- }
- else if (!lp->resumed)
- {
- linux_nat_debug_printf ("NOT resuming LWP %s, not resumed",
- lp->ptid.to_string ().c_str ());
- }
- else if (lwp_status_pending_p (lp))
- {
- linux_nat_debug_printf ("NOT resuming LWP %s, has pending status",
- lp->ptid.to_string ().c_str ());
- }
- else
- {
- struct regcache *regcache = get_thread_regcache (linux_target, lp->ptid);
- struct gdbarch *gdbarch = regcache->arch ();
- try
- {
- CORE_ADDR pc = regcache_read_pc (regcache);
- int leave_stopped = 0;
- /* Don't bother if there's a breakpoint at PC that we'd hit
- immediately, and we're not waiting for this LWP. */
- if (!lp->ptid.matches (wait_ptid))
- {
- if (breakpoint_inserted_here_p (regcache->aspace (), pc))
- leave_stopped = 1;
- }
- if (!leave_stopped)
- {
- linux_nat_debug_printf
- ("resuming stopped-resumed LWP %s at %s: step=%d",
- lp->ptid.to_string ().c_str (), paddress (gdbarch, pc),
- lp->step);
- linux_resume_one_lwp_throw (lp, lp->step, GDB_SIGNAL_0);
- }
- }
- catch (const gdb_exception_error &ex)
- {
- if (!check_ptrace_stopped_lwp_gone (lp))
- throw;
- }
- }
- return 0;
- }
- ptid_t
- linux_nat_target::wait (ptid_t ptid, struct target_waitstatus *ourstatus,
- target_wait_flags target_options)
- {
- ptid_t event_ptid;
- linux_nat_debug_printf ("[%s], [%s]", ptid.to_string ().c_str (),
- target_options_to_string (target_options).c_str ());
- /* Flush the async file first. */
- if (target_is_async_p ())
- async_file_flush ();
- /* Resume LWPs that are currently stopped without any pending status
- to report, but are resumed from the core's perspective. LWPs get
- in this state if we find them stopping at a time we're not
- interested in reporting the event (target_wait on a
- specific_process, for example, see linux_nat_wait_1), and
- meanwhile the event became uninteresting. Don't bother resuming
- LWPs we're not going to wait for if they'd stop immediately. */
- if (target_is_non_stop_p ())
- iterate_over_lwps (minus_one_ptid,
- [=] (struct lwp_info *info)
- {
- return resume_stopped_resumed_lwps (info, ptid);
- });
- event_ptid = linux_nat_wait_1 (ptid, ourstatus, target_options);
- /* If we requested any event, and something came out, assume there
- may be more. If we requested a specific lwp or process, also
- assume there may be more. */
- if (target_is_async_p ()
- && ((ourstatus->kind () != TARGET_WAITKIND_IGNORE
- && ourstatus->kind () != TARGET_WAITKIND_NO_RESUMED)
- || ptid != minus_one_ptid))
- async_file_mark ();
- return event_ptid;
- }
- /* Kill one LWP. */
- static void
- kill_one_lwp (pid_t pid)
- {
- /* PTRACE_KILL may resume the inferior. Send SIGKILL first. */
- errno = 0;
- kill_lwp (pid, SIGKILL);
- if (debug_linux_nat)
- {
- int save_errno = errno;
- linux_nat_debug_printf
- ("kill (SIGKILL) %ld, 0, 0 (%s)", (long) pid,
- save_errno != 0 ? safe_strerror (save_errno) : "OK");
- }
- /* Some kernels ignore even SIGKILL for processes under ptrace. */
- errno = 0;
- ptrace (PTRACE_KILL, pid, 0, 0);
- if (debug_linux_nat)
- {
- int save_errno = errno;
- linux_nat_debug_printf
- ("PTRACE_KILL %ld, 0, 0 (%s)", (long) pid,
- save_errno ? safe_strerror (save_errno) : "OK");
- }
- }
- /* Wait for an LWP to die. */
- static void
- kill_wait_one_lwp (pid_t pid)
- {
- pid_t res;
- /* We must make sure that there are no pending events (delayed
- SIGSTOPs, pending SIGTRAPs, etc.) to make sure the current
- program doesn't interfere with any following debugging session. */
- do
- {
- res = my_waitpid (pid, NULL, __WALL);
- if (res != (pid_t) -1)
- {
- linux_nat_debug_printf ("wait %ld received unknown.", (long) pid);
- /* The Linux kernel sometimes fails to kill a thread
- completely after PTRACE_KILL; that goes from the stop
- point in do_fork out to the one in get_signal_to_deliver
- and waits again. So kill it again. */
- kill_one_lwp (pid);
- }
- }
- while (res == pid);
- gdb_assert (res == -1 && errno == ECHILD);
- }
- /* Callback for iterate_over_lwps. */
- static int
- kill_callback (struct lwp_info *lp)
- {
- kill_one_lwp (lp->ptid.lwp ());
- return 0;
- }
- /* Callback for iterate_over_lwps. */
- static int
- kill_wait_callback (struct lwp_info *lp)
- {
- kill_wait_one_lwp (lp->ptid.lwp ());
- return 0;
- }
- /* Kill the fork children of any threads of inferior INF that are
- stopped at a fork event. */
- static void
- kill_unfollowed_fork_children (struct inferior *inf)
- {
- for (thread_info *thread : inf->non_exited_threads ())
- {
- struct target_waitstatus *ws = &thread->pending_follow;
- if (ws->kind () == TARGET_WAITKIND_FORKED
- || ws->kind () == TARGET_WAITKIND_VFORKED)
- {
- ptid_t child_ptid = ws->child_ptid ();
- int child_pid = child_ptid.pid ();
- int child_lwp = child_ptid.lwp ();
- kill_one_lwp (child_lwp);
- kill_wait_one_lwp (child_lwp);
- /* Let the arch-specific native code know this process is
- gone. */
- linux_target->low_forget_process (child_pid);
- }
- }
- }
- void
- linux_nat_target::kill ()
- {
- /* If we're stopped while forking and we haven't followed yet,
- kill the other task. We need to do this first because the
- parent will be sleeping if this is a vfork. */
- kill_unfollowed_fork_children (current_inferior ());
- if (forks_exist_p ())
- linux_fork_killall ();
- else
- {
- ptid_t ptid = ptid_t (inferior_ptid.pid ());
- /* Stop all threads before killing them, since ptrace requires
- that the thread is stopped to successfully PTRACE_KILL. */
- iterate_over_lwps (ptid, stop_callback);
- /* ... and wait until all of them have reported back that
- they're no longer running. */
- iterate_over_lwps (ptid, stop_wait_callback);
- /* Kill all LWP's ... */
- iterate_over_lwps (ptid, kill_callback);
- /* ... and wait until we've flushed all events. */
- iterate_over_lwps (ptid, kill_wait_callback);
- }
- target_mourn_inferior (inferior_ptid);
- }
- void
- linux_nat_target::mourn_inferior ()
- {
- int pid = inferior_ptid.pid ();
- purge_lwp_list (pid);
- close_proc_mem_file (pid);
- if (! forks_exist_p ())
- /* Normal case, no other forks available. */
- inf_ptrace_target::mourn_inferior ();
- else
- /* Multi-fork case. The current inferior_ptid has exited, but
- there are other viable forks to debug. Delete the exiting
- one and context-switch to the first available. */
- linux_fork_mourn_inferior ();
- /* Let the arch-specific native code know this process is gone. */
- linux_target->low_forget_process (pid);
- }
- /* Convert a native/host siginfo object, into/from the siginfo in the
- layout of the inferiors' architecture. */
- static void
- siginfo_fixup (siginfo_t *siginfo, gdb_byte *inf_siginfo, int direction)
- {
- /* If the low target didn't do anything, then just do a straight
- memcpy. */
- if (!linux_target->low_siginfo_fixup (siginfo, inf_siginfo, direction))
- {
- if (direction == 1)
- memcpy (siginfo, inf_siginfo, sizeof (siginfo_t));
- else
- memcpy (inf_siginfo, siginfo, sizeof (siginfo_t));
- }
- }
- static enum target_xfer_status
- linux_xfer_siginfo (enum target_object object,
- const char *annex, gdb_byte *readbuf,
- const gdb_byte *writebuf, ULONGEST offset, ULONGEST len,
- ULONGEST *xfered_len)
- {
- int pid;
- siginfo_t siginfo;
- gdb_byte inf_siginfo[sizeof (siginfo_t)];
- gdb_assert (object == TARGET_OBJECT_SIGNAL_INFO);
- gdb_assert (readbuf || writebuf);
- pid = inferior_ptid.lwp ();
- if (pid == 0)
- pid = inferior_ptid.pid ();
- if (offset > sizeof (siginfo))
- return TARGET_XFER_E_IO;
- errno = 0;
- ptrace (PTRACE_GETSIGINFO, pid, (PTRACE_TYPE_ARG3) 0, &siginfo);
- if (errno != 0)
- return TARGET_XFER_E_IO;
- /* When GDB is built as a 64-bit application, ptrace writes into
- SIGINFO an object with 64-bit layout. Since debugging a 32-bit
- inferior with a 64-bit GDB should look the same as debugging it
- with a 32-bit GDB, we need to convert it. GDB core always sees
- the converted layout, so any read/write will have to be done
- post-conversion. */
- siginfo_fixup (&siginfo, inf_siginfo, 0);
- if (offset + len > sizeof (siginfo))
- len = sizeof (siginfo) - offset;
- if (readbuf != NULL)
- memcpy (readbuf, inf_siginfo + offset, len);
- else
- {
- memcpy (inf_siginfo + offset, writebuf, len);
- /* Convert back to ptrace layout before flushing it out. */
- siginfo_fixup (&siginfo, inf_siginfo, 1);
- errno = 0;
- ptrace (PTRACE_SETSIGINFO, pid, (PTRACE_TYPE_ARG3) 0, &siginfo);
- if (errno != 0)
- return TARGET_XFER_E_IO;
- }
- *xfered_len = len;
- return TARGET_XFER_OK;
- }
- static enum target_xfer_status
- linux_nat_xfer_osdata (enum target_object object,
- const char *annex, gdb_byte *readbuf,
- const gdb_byte *writebuf, ULONGEST offset, ULONGEST len,
- ULONGEST *xfered_len);
- static enum target_xfer_status
- linux_proc_xfer_memory_partial (gdb_byte *readbuf, const gdb_byte *writebuf,
- ULONGEST offset, LONGEST len, ULONGEST *xfered_len);
- enum target_xfer_status
- linux_nat_target::xfer_partial (enum target_object object,
- const char *annex, gdb_byte *readbuf,
- const gdb_byte *writebuf,
- ULONGEST offset, ULONGEST len, ULONGEST *xfered_len)
- {
- if (object == TARGET_OBJECT_SIGNAL_INFO)
- return linux_xfer_siginfo (object, annex, readbuf, writebuf,
- offset, len, xfered_len);
- /* The target is connected but no live inferior is selected. Pass
- this request down to a lower stratum (e.g., the executable
- file). */
- if (object == TARGET_OBJECT_MEMORY && inferior_ptid == null_ptid)
- return TARGET_XFER_EOF;
- if (object == TARGET_OBJECT_AUXV)
- return memory_xfer_auxv (this, object, annex, readbuf, writebuf,
- offset, len, xfered_len);
- if (object == TARGET_OBJECT_OSDATA)
- return linux_nat_xfer_osdata (object, annex, readbuf, writebuf,
- offset, len, xfered_len);
- if (object == TARGET_OBJECT_MEMORY)
- {
- /* GDB calculates all addresses in the largest possible address
- width. The address width must be masked before its final use
- by linux_proc_xfer_partial.
- Compare ADDR_BIT first to avoid a compiler warning on shift overflow. */
- int addr_bit = gdbarch_addr_bit (target_gdbarch ());
- if (addr_bit < (sizeof (ULONGEST) * HOST_CHAR_BIT))
- offset &= ((ULONGEST) 1 << addr_bit) - 1;
- return linux_proc_xfer_memory_partial (readbuf, writebuf,
- offset, len, xfered_len);
- }
- return inf_ptrace_target::xfer_partial (object, annex, readbuf, writebuf,
- offset, len, xfered_len);
- }
- bool
- linux_nat_target::thread_alive (ptid_t ptid)
- {
- /* As long as a PTID is in lwp list, consider it alive. */
- return find_lwp_pid (ptid) != NULL;
- }
- /* Implement the to_update_thread_list target method for this
- target. */
- void
- linux_nat_target::update_thread_list ()
- {
- /* We add/delete threads from the list as clone/exit events are
- processed, so just try deleting exited threads still in the
- thread list. */
- delete_exited_threads ();
- /* Update the processor core that each lwp/thread was last seen
- running on. */
- for (lwp_info *lwp : all_lwps ())
- {
- /* Avoid accessing /proc if the thread hasn't run since we last
- time we fetched the thread's core. Accessing /proc becomes
- noticeably expensive when we have thousands of LWPs. */
- if (lwp->core == -1)
- lwp->core = linux_common_core_of_thread (lwp->ptid);
- }
- }
- std::string
- linux_nat_target::pid_to_str (ptid_t ptid)
- {
- if (ptid.lwp_p ()
- && (ptid.pid () != ptid.lwp ()
- || num_lwps (ptid.pid ()) > 1))
- return string_printf ("LWP %ld", ptid.lwp ());
- return normal_pid_to_str (ptid);
- }
- const char *
- linux_nat_target::thread_name (struct thread_info *thr)
- {
- return linux_proc_tid_get_name (thr->ptid);
- }
- /* Accepts an integer PID; Returns a string representing a file that
- can be opened to get the symbols for the child process. */
- char *
- linux_nat_target::pid_to_exec_file (int pid)
- {
- return linux_proc_pid_to_exec_file (pid);
- }
- /* Object representing an /proc/PID/mem open file. We keep one such
- file open per inferior.
- It might be tempting to think about only ever opening one file at
- most for all inferiors, closing/reopening the file as we access
- memory of different inferiors, to minimize number of file
- descriptors open, which can otherwise run into resource limits.
- However, that does not work correctly -- if the inferior execs and
- we haven't processed the exec event yet, and, we opened a
- /proc/PID/mem file, we will get a mem file accessing the post-exec
- address space, thinking we're opening it for the pre-exec address
- space. That is dangerous as we can poke memory (e.g. clearing
- breakpoints) in the post-exec memory by mistake, corrupting the
- inferior. For that reason, we open the mem file as early as
- possible, right after spawning, forking or attaching to the
- inferior, when the inferior is stopped and thus before it has a
- chance of execing.
- Note that after opening the file, even if the thread we opened it
- for subsequently exits, the open file is still usable for accessing
- memory. It's only when the whole process exits or execs that the
- file becomes invalid, at which point reads/writes return EOF. */
- class proc_mem_file
- {
- public:
- proc_mem_file (ptid_t ptid, int fd)
- : m_ptid (ptid), m_fd (fd)
- {
- gdb_assert (m_fd != -1);
- }
- ~proc_mem_file ()
- {
- linux_nat_debug_printf ("closing fd %d for /proc/%d/task/%ld/mem",
- m_fd, m_ptid.pid (), m_ptid.lwp ());
- close (m_fd);
- }
- DISABLE_COPY_AND_ASSIGN (proc_mem_file);
- int fd ()
- {
- return m_fd;
- }
- private:
- /* The LWP this file was opened for. Just for debugging
- purposes. */
- ptid_t m_ptid;
- /* The file descriptor. */
- int m_fd = -1;
- };
- /* The map between an inferior process id, and the open /proc/PID/mem
- file. This is stored in a map instead of in a per-inferior
- structure because we need to be able to access memory of processes
- which don't have a corresponding struct inferior object. E.g.,
- with "detach-on-fork on" (the default), and "follow-fork parent"
- (also default), we don't create an inferior for the fork child, but
- we still need to remove breakpoints from the fork child's
- memory. */
- static std::unordered_map<int, proc_mem_file> proc_mem_file_map;
- /* Close the /proc/PID/mem file for PID. */
- static void
- close_proc_mem_file (pid_t pid)
- {
- proc_mem_file_map.erase (pid);
- }
- /* Open the /proc/PID/mem file for the process (thread group) of PTID.
- We actually open /proc/PID/task/LWP/mem, as that's the LWP we know
- exists and is stopped right now. We prefer the
- /proc/PID/task/LWP/mem form over /proc/LWP/mem to avoid tid-reuse
- races, just in case this is ever called on an already-waited
- LWP. */
- static void
- open_proc_mem_file (ptid_t ptid)
- {
- auto iter = proc_mem_file_map.find (ptid.pid ());
- gdb_assert (iter == proc_mem_file_map.end ());
- char filename[64];
- xsnprintf (filename, sizeof filename,
- "/proc/%d/task/%ld/mem", ptid.pid (), ptid.lwp ());
- int fd = gdb_open_cloexec (filename, O_RDWR | O_LARGEFILE, 0).release ();
- if (fd == -1)
- {
- warning (_("opening /proc/PID/mem file for lwp %d.%ld failed: %s (%d)"),
- ptid.pid (), ptid.lwp (),
- safe_strerror (errno), errno);
- return;
- }
- proc_mem_file_map.emplace (std::piecewise_construct,
- std::forward_as_tuple (ptid.pid ()),
- std::forward_as_tuple (ptid, fd));
- linux_nat_debug_printf ("opened fd %d for lwp %d.%ld",
- fd, ptid.pid (), ptid.lwp ());
- }
- /* Implement the to_xfer_partial target method using /proc/PID/mem.
- Because we can use a single read/write call, this can be much more
- efficient than banging away at PTRACE_PEEKTEXT. Also, unlike
- PTRACE_PEEKTEXT/PTRACE_POKETEXT, this works with running
- threads. */
- static enum target_xfer_status
- linux_proc_xfer_memory_partial (gdb_byte *readbuf, const gdb_byte *writebuf,
- ULONGEST offset, LONGEST len,
- ULONGEST *xfered_len)
- {
- ssize_t ret;
- auto iter = proc_mem_file_map.find (inferior_ptid.pid ());
- if (iter == proc_mem_file_map.end ())
- return TARGET_XFER_EOF;
- int fd = iter->second.fd ();
- gdb_assert (fd != -1);
- /* Use pread64/pwrite64 if available, since they save a syscall and can
- handle 64-bit offsets even on 32-bit platforms (for instance, SPARC
- debugging a SPARC64 application). */
- #ifdef HAVE_PREAD64
- ret = (readbuf ? pread64 (fd, readbuf, len, offset)
- : pwrite64 (fd, writebuf, len, offset));
- #else
- ret = lseek (fd, offset, SEEK_SET);
- if (ret != -1)
- ret = (readbuf ? read (fd, readbuf, len)
- : write (fd, writebuf, len));
- #endif
- if (ret == -1)
- {
- linux_nat_debug_printf ("accessing fd %d for pid %d failed: %s (%d)",
- fd, inferior_ptid.pid (),
- safe_strerror (errno), errno);
- return TARGET_XFER_EOF;
- }
- else if (ret == 0)
- {
- /* EOF means the address space is gone, the whole process exited
- or execed. */
- linux_nat_debug_printf ("accessing fd %d for pid %d got EOF",
- fd, inferior_ptid.pid ());
- return TARGET_XFER_EOF;
- }
- else
- {
- *xfered_len = ret;
- return TARGET_XFER_OK;
- }
- }
- /* Parse LINE as a signal set and add its set bits to SIGS. */
- static void
- add_line_to_sigset (const char *line, sigset_t *sigs)
- {
- int len = strlen (line) - 1;
- const char *p;
- int signum;
- if (line[len] != '\n')
- error (_("Could not parse signal set: %s"), line);
- p = line;
- signum = len * 4;
- while (len-- > 0)
- {
- int digit;
- if (*p >= '0' && *p <= '9')
- digit = *p - '0';
- else if (*p >= 'a' && *p <= 'f')
- digit = *p - 'a' + 10;
- else
- error (_("Could not parse signal set: %s"), line);
- signum -= 4;
- if (digit & 1)
- sigaddset (sigs, signum + 1);
- if (digit & 2)
- sigaddset (sigs, signum + 2);
- if (digit & 4)
- sigaddset (sigs, signum + 3);
- if (digit & 8)
- sigaddset (sigs, signum + 4);
- p++;
- }
- }
- /* Find process PID's pending signals from /proc/pid/status and set
- SIGS to match. */
- void
- linux_proc_pending_signals (int pid, sigset_t *pending,
- sigset_t *blocked, sigset_t *ignored)
- {
- char buffer[PATH_MAX], fname[PATH_MAX];
- sigemptyset (pending);
- sigemptyset (blocked);
- sigemptyset (ignored);
- xsnprintf (fname, sizeof fname, "/proc/%d/status", pid);
- gdb_file_up procfile = gdb_fopen_cloexec (fname, "r");
- if (procfile == NULL)
- error (_("Could not open %s"), fname);
- while (fgets (buffer, PATH_MAX, procfile.get ()) != NULL)
- {
- /* Normal queued signals are on the SigPnd line in the status
- file. However, 2.6 kernels also have a "shared" pending
- queue for delivering signals to a thread group, so check for
- a ShdPnd line also.
- Unfortunately some Red Hat kernels include the shared pending
- queue but not the ShdPnd status field. */
- if (startswith (buffer, "SigPnd:\t"))
- add_line_to_sigset (buffer + 8, pending);
- else if (startswith (buffer, "ShdPnd:\t"))
- add_line_to_sigset (buffer + 8, pending);
- else if (startswith (buffer, "SigBlk:\t"))
- add_line_to_sigset (buffer + 8, blocked);
- else if (startswith (buffer, "SigIgn:\t"))
- add_line_to_sigset (buffer + 8, ignored);
- }
- }
- static enum target_xfer_status
- linux_nat_xfer_osdata (enum target_object object,
- const char *annex, gdb_byte *readbuf,
- const gdb_byte *writebuf, ULONGEST offset, ULONGEST len,
- ULONGEST *xfered_len)
- {
- gdb_assert (object == TARGET_OBJECT_OSDATA);
- *xfered_len = linux_common_xfer_osdata (annex, readbuf, offset, len);
- if (*xfered_len == 0)
- return TARGET_XFER_EOF;
- else
- return TARGET_XFER_OK;
- }
- std::vector<static_tracepoint_marker>
- linux_nat_target::static_tracepoint_markers_by_strid (const char *strid)
- {
- char s[IPA_CMD_BUF_SIZE];
- int pid = inferior_ptid.pid ();
- std::vector<static_tracepoint_marker> markers;
- const char *p = s;
- ptid_t ptid = ptid_t (pid, 0);
- static_tracepoint_marker marker;
- /* Pause all */
- target_stop (ptid);
- memcpy (s, "qTfSTM", sizeof ("qTfSTM"));
- s[sizeof ("qTfSTM")] = 0;
- agent_run_command (pid, s, strlen (s) + 1);
- /* Unpause all. */
- SCOPE_EXIT { target_continue_no_signal (ptid); };
- while (*p++ == 'm')
- {
- do
- {
- parse_static_tracepoint_marker_definition (p, &p, &marker);
- if (strid == NULL || marker.str_id == strid)
- markers.push_back (std::move (marker));
- }
- while (*p++ == ','); /* comma-separated list */
- memcpy (s, "qTsSTM", sizeof ("qTsSTM"));
- s[sizeof ("qTsSTM")] = 0;
- agent_run_command (pid, s, strlen (s) + 1);
- p = s;
- }
- return markers;
- }
- /* target_can_async_p implementation. */
- bool
- linux_nat_target::can_async_p ()
- {
- /* This flag should be checked in the common target.c code. */
- gdb_assert (target_async_permitted);
-
- /* Otherwise, this targets is always able to support async mode. */
- return true;
- }
- bool
- linux_nat_target::supports_non_stop ()
- {
- return true;
- }
- /* to_always_non_stop_p implementation. */
- bool
- linux_nat_target::always_non_stop_p ()
- {
- return true;
- }
- bool
- linux_nat_target::supports_multi_process ()
- {
- return true;
- }
- bool
- linux_nat_target::supports_disable_randomization ()
- {
- return true;
- }
- /* SIGCHLD handler that serves two purposes: In non-stop/async mode,
- so we notice when any child changes state, and notify the
- event-loop; it allows us to use sigsuspend in linux_nat_wait_1
- above to wait for the arrival of a SIGCHLD. */
- static void
- sigchld_handler (int signo)
- {
- int old_errno = errno;
- if (debug_linux_nat)
- gdb_stdlog->write_async_safe ("sigchld\n", sizeof ("sigchld\n") - 1);
- if (signo == SIGCHLD)
- {
- /* Let the event loop know that there are events to handle. */
- linux_nat_target::async_file_mark_if_open ();
- }
- errno = old_errno;
- }
- /* Callback registered with the target events file descriptor. */
- static void
- handle_target_event (int error, gdb_client_data client_data)
- {
- inferior_event_handler (INF_REG_EVENT);
- }
- /* target_async implementation. */
- void
- linux_nat_target::async (int enable)
- {
- if ((enable != 0) == is_async_p ())
- return;
- /* Block child signals while we create/destroy the pipe, as their
- handler writes to it. */
- gdb::block_signals blocker;
- if (enable)
- {
- if (!async_file_open ())
- internal_error (__FILE__, __LINE__, "creating event pipe failed.");
- add_file_handler (async_wait_fd (), handle_target_event, NULL,
- "linux-nat");
- /* There may be pending events to handle. Tell the event loop
- to poll them. */
- async_file_mark ();
- }
- else
- {
- delete_file_handler (async_wait_fd ());
- async_file_close ();
- }
- }
- /* Stop an LWP, and push a GDB_SIGNAL_0 stop status if no other
- event came out. */
- static int
- linux_nat_stop_lwp (struct lwp_info *lwp)
- {
- if (!lwp->stopped)
- {
- linux_nat_debug_printf ("running -> suspending %s",
- lwp->ptid.to_string ().c_str ());
- if (lwp->last_resume_kind == resume_stop)
- {
- linux_nat_debug_printf ("already stopping LWP %ld at GDB's request",
- lwp->ptid.lwp ());
- return 0;
- }
- stop_callback (lwp);
- lwp->last_resume_kind = resume_stop;
- }
- else
- {
- /* Already known to be stopped; do nothing. */
- if (debug_linux_nat)
- {
- if (find_thread_ptid (linux_target, lwp->ptid)->stop_requested)
- linux_nat_debug_printf ("already stopped/stop_requested %s",
- lwp->ptid.to_string ().c_str ());
- else
- linux_nat_debug_printf ("already stopped/no stop_requested yet %s",
- lwp->ptid.to_string ().c_str ());
- }
- }
- return 0;
- }
- void
- linux_nat_target::stop (ptid_t ptid)
- {
- LINUX_NAT_SCOPED_DEBUG_ENTER_EXIT;
- iterate_over_lwps (ptid, linux_nat_stop_lwp);
- }
- /* When requests are passed down from the linux-nat layer to the
- single threaded inf-ptrace layer, ptids of (lwpid,0,0) form are
- used. The address space pointer is stored in the inferior object,
- but the common code that is passed such ptid can't tell whether
- lwpid is a "main" process id or not (it assumes so). We reverse
- look up the "main" process id from the lwp here. */
- struct address_space *
- linux_nat_target::thread_address_space (ptid_t ptid)
- {
- struct lwp_info *lwp;
- struct inferior *inf;
- int pid;
- if (ptid.lwp () == 0)
- {
- /* An (lwpid,0,0) ptid. Look up the lwp object to get at the
- tgid. */
- lwp = find_lwp_pid (ptid);
- pid = lwp->ptid.pid ();
- }
- else
- {
- /* A (pid,lwpid,0) ptid. */
- pid = ptid.pid ();
- }
- inf = find_inferior_pid (this, pid);
- gdb_assert (inf != NULL);
- return inf->aspace;
- }
- /* Return the cached value of the processor core for thread PTID. */
- int
- linux_nat_target::core_of_thread (ptid_t ptid)
- {
- struct lwp_info *info = find_lwp_pid (ptid);
- if (info)
- return info->core;
- return -1;
- }
- /* Implementation of to_filesystem_is_local. */
- bool
- linux_nat_target::filesystem_is_local ()
- {
- struct inferior *inf = current_inferior ();
- if (inf->fake_pid_p || inf->pid == 0)
- return true;
- return linux_ns_same (inf->pid, LINUX_NS_MNT);
- }
- /* Convert the INF argument passed to a to_fileio_* method
- to a process ID suitable for passing to its corresponding
- linux_mntns_* function. If INF is non-NULL then the
- caller is requesting the filesystem seen by INF. If INF
- is NULL then the caller is requesting the filesystem seen
- by the GDB. We fall back to GDB's filesystem in the case
- that INF is non-NULL but its PID is unknown. */
- static pid_t
- linux_nat_fileio_pid_of (struct inferior *inf)
- {
- if (inf == NULL || inf->fake_pid_p || inf->pid == 0)
- return getpid ();
- else
- return inf->pid;
- }
- /* Implementation of to_fileio_open. */
- int
- linux_nat_target::fileio_open (struct inferior *inf, const char *filename,
- int flags, int mode, int warn_if_slow,
- int *target_errno)
- {
- int nat_flags;
- mode_t nat_mode;
- int fd;
- if (fileio_to_host_openflags (flags, &nat_flags) == -1
- || fileio_to_host_mode (mode, &nat_mode) == -1)
- {
- *target_errno = FILEIO_EINVAL;
- return -1;
- }
- fd = linux_mntns_open_cloexec (linux_nat_fileio_pid_of (inf),
- filename, nat_flags, nat_mode);
- if (fd == -1)
- *target_errno = host_to_fileio_error (errno);
- return fd;
- }
- /* Implementation of to_fileio_readlink. */
- gdb::optional<std::string>
- linux_nat_target::fileio_readlink (struct inferior *inf, const char *filename,
- int *target_errno)
- {
- char buf[PATH_MAX];
- int len;
- len = linux_mntns_readlink (linux_nat_fileio_pid_of (inf),
- filename, buf, sizeof (buf));
- if (len < 0)
- {
- *target_errno = host_to_fileio_error (errno);
- return {};
- }
- return std::string (buf, len);
- }
- /* Implementation of to_fileio_unlink. */
- int
- linux_nat_target::fileio_unlink (struct inferior *inf, const char *filename,
- int *target_errno)
- {
- int ret;
- ret = linux_mntns_unlink (linux_nat_fileio_pid_of (inf),
- filename);
- if (ret == -1)
- *target_errno = host_to_fileio_error (errno);
- return ret;
- }
- /* Implementation of the to_thread_events method. */
- void
- linux_nat_target::thread_events (int enable)
- {
- report_thread_events = enable;
- }
- linux_nat_target::linux_nat_target ()
- {
- /* We don't change the stratum; this target will sit at
- process_stratum and thread_db will set at thread_stratum. This
- is a little strange, since this is a multi-threaded-capable
- target, but we want to be on the stack below thread_db, and we
- also want to be used for single-threaded processes. */
- }
- /* See linux-nat.h. */
- int
- linux_nat_get_siginfo (ptid_t ptid, siginfo_t *siginfo)
- {
- int pid;
- pid = ptid.lwp ();
- if (pid == 0)
- pid = ptid.pid ();
- errno = 0;
- ptrace (PTRACE_GETSIGINFO, pid, (PTRACE_TYPE_ARG3) 0, siginfo);
- if (errno != 0)
- {
- memset (siginfo, 0, sizeof (*siginfo));
- return 0;
- }
- return 1;
- }
- /* See nat/linux-nat.h. */
- ptid_t
- current_lwp_ptid (void)
- {
- gdb_assert (inferior_ptid.lwp_p ());
- return inferior_ptid;
- }
- void _initialize_linux_nat ();
- void
- _initialize_linux_nat ()
- {
- add_setshow_boolean_cmd ("linux-nat", class_maintenance,
- &debug_linux_nat, _("\
- Set debugging of GNU/Linux native target."), _(" \
- Show debugging of GNU/Linux native target."), _(" \
- When on, print debug messages relating to the GNU/Linux native target."),
- nullptr,
- show_debug_linux_nat,
- &setdebuglist, &showdebuglist);
- add_setshow_boolean_cmd ("linux-namespaces", class_maintenance,
- &debug_linux_namespaces, _("\
- Set debugging of GNU/Linux namespaces module."), _("\
- Show debugging of GNU/Linux namespaces module."), _("\
- Enables printf debugging output."),
- NULL,
- NULL,
- &setdebuglist, &showdebuglist);
- /* Install a SIGCHLD handler. */
- sigchld_action.sa_handler = sigchld_handler;
- sigemptyset (&sigchld_action.sa_mask);
- sigchld_action.sa_flags = SA_RESTART;
- /* Make it the default. */
- sigaction (SIGCHLD, &sigchld_action, NULL);
- /* Make sure we don't block SIGCHLD during a sigsuspend. */
- gdb_sigmask (SIG_SETMASK, NULL, &suspend_mask);
- sigdelset (&suspend_mask, SIGCHLD);
- sigemptyset (&blocked_mask);
- lwp_lwpid_htab_create ();
- }
- /* FIXME: kettenis/2000-08-26: The stuff on this page is specific to
- the GNU/Linux Threads library and therefore doesn't really belong
- here. */
- /* NPTL reserves the first two RT signals, but does not provide any
- way for the debugger to query the signal numbers - fortunately
- they don't change. */
- static int lin_thread_signals[] = { __SIGRTMIN, __SIGRTMIN + 1 };
- /* See linux-nat.h. */
- unsigned int
- lin_thread_get_thread_signal_num (void)
- {
- return sizeof (lin_thread_signals) / sizeof (lin_thread_signals[0]);
- }
- /* See linux-nat.h. */
- int
- lin_thread_get_thread_signal (unsigned int i)
- {
- gdb_assert (i < lin_thread_get_thread_signal_num ());
- return lin_thread_signals[i];
- }
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