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- /* Read ELF (Executable and Linking Format) object files for GDB.
- Copyright (C) 1991-2022 Free Software Foundation, Inc.
- Written by Fred Fish at Cygnus Support.
- 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 "bfd.h"
- #include "elf-bfd.h"
- #include "elf/common.h"
- #include "elf/internal.h"
- #include "elf/mips.h"
- #include "symtab.h"
- #include "symfile.h"
- #include "objfiles.h"
- #include "stabsread.h"
- #include "demangle.h"
- #include "psympriv.h"
- #include "filenames.h"
- #include "probe.h"
- #include "arch-utils.h"
- #include "gdbtypes.h"
- #include "value.h"
- #include "infcall.h"
- #include "gdbthread.h"
- #include "inferior.h"
- #include "regcache.h"
- #include "bcache.h"
- #include "gdb_bfd.h"
- #include "build-id.h"
- #include "location.h"
- #include "auxv.h"
- #include "mdebugread.h"
- #include "ctfread.h"
- #include "gdbsupport/gdb_string_view.h"
- #include "gdbsupport/scoped_fd.h"
- #include "debuginfod-support.h"
- #include "dwarf2/public.h"
- /* The struct elfinfo is available only during ELF symbol table and
- psymtab reading. It is destroyed at the completion of psymtab-reading.
- It's local to elf_symfile_read. */
- struct elfinfo
- {
- asection *stabsect; /* Section pointer for .stab section */
- asection *mdebugsect; /* Section pointer for .mdebug section */
- asection *ctfsect; /* Section pointer for .ctf section */
- };
- /* Type for per-BFD data. */
- typedef std::vector<std::unique_ptr<probe>> elfread_data;
- /* Per-BFD data for probe info. */
- static const struct bfd_key<elfread_data> probe_key;
- /* Minimal symbols located at the GOT entries for .plt - that is the real
- pointer where the given entry will jump to. It gets updated by the real
- function address during lazy ld.so resolving in the inferior. These
- minimal symbols are indexed for <tab>-completion. */
- #define SYMBOL_GOT_PLT_SUFFIX "@got.plt"
- /* Locate the segments in ABFD. */
- static symfile_segment_data_up
- elf_symfile_segments (bfd *abfd)
- {
- Elf_Internal_Phdr *phdrs, **segments;
- long phdrs_size;
- int num_phdrs, num_segments, num_sections, i;
- asection *sect;
- phdrs_size = bfd_get_elf_phdr_upper_bound (abfd);
- if (phdrs_size == -1)
- return NULL;
- phdrs = (Elf_Internal_Phdr *) alloca (phdrs_size);
- num_phdrs = bfd_get_elf_phdrs (abfd, phdrs);
- if (num_phdrs == -1)
- return NULL;
- num_segments = 0;
- segments = XALLOCAVEC (Elf_Internal_Phdr *, num_phdrs);
- for (i = 0; i < num_phdrs; i++)
- if (phdrs[i].p_type == PT_LOAD)
- segments[num_segments++] = &phdrs[i];
- if (num_segments == 0)
- return NULL;
- symfile_segment_data_up data (new symfile_segment_data);
- data->segments.reserve (num_segments);
- for (i = 0; i < num_segments; i++)
- data->segments.emplace_back (segments[i]->p_vaddr, segments[i]->p_memsz);
- num_sections = bfd_count_sections (abfd);
- /* All elements are initialized to 0 (map to no segment). */
- data->segment_info.resize (num_sections);
- for (i = 0, sect = abfd->sections; sect != NULL; i++, sect = sect->next)
- {
- int j;
- if ((bfd_section_flags (sect) & SEC_ALLOC) == 0)
- continue;
- Elf_Internal_Shdr *this_hdr = &elf_section_data (sect)->this_hdr;
- for (j = 0; j < num_segments; j++)
- if (ELF_SECTION_IN_SEGMENT (this_hdr, segments[j]))
- {
- data->segment_info[i] = j + 1;
- break;
- }
- /* We should have found a segment for every non-empty section.
- If we haven't, we will not relocate this section by any
- offsets we apply to the segments. As an exception, do not
- warn about SHT_NOBITS sections; in normal ELF execution
- environments, SHT_NOBITS means zero-initialized and belongs
- in a segment, but in no-OS environments some tools (e.g. ARM
- RealView) use SHT_NOBITS for uninitialized data. Since it is
- uninitialized, it doesn't need a program header. Such
- binaries are not relocatable. */
- /* Exclude debuginfo files from this warning, too, since those
- are often not strictly compliant with the standard. See, e.g.,
- ld/24717 for more discussion. */
- if (!is_debuginfo_file (abfd)
- && bfd_section_size (sect) > 0 && j == num_segments
- && (bfd_section_flags (sect) & SEC_LOAD) != 0)
- warning (_("Loadable section \"%s\" outside of ELF segments\n in %s"),
- bfd_section_name (sect), bfd_get_filename (abfd));
- }
- return data;
- }
- /* We are called once per section from elf_symfile_read. We
- need to examine each section we are passed, check to see
- if it is something we are interested in processing, and
- if so, stash away some access information for the section.
- For now we recognize the dwarf debug information sections and
- line number sections from matching their section names. The
- ELF definition is no real help here since it has no direct
- knowledge of DWARF (by design, so any debugging format can be
- used).
- We also recognize the ".stab" sections used by the Sun compilers
- released with Solaris 2.
- FIXME: The section names should not be hardwired strings (what
- should they be? I don't think most object file formats have enough
- section flags to specify what kind of debug section it is.
- -kingdon). */
- static void
- elf_locate_sections (asection *sectp, struct elfinfo *ei)
- {
- if (strcmp (sectp->name, ".stab") == 0)
- {
- ei->stabsect = sectp;
- }
- else if (strcmp (sectp->name, ".mdebug") == 0)
- {
- ei->mdebugsect = sectp;
- }
- else if (strcmp (sectp->name, ".ctf") == 0)
- {
- ei->ctfsect = sectp;
- }
- }
- static struct minimal_symbol *
- record_minimal_symbol (minimal_symbol_reader &reader,
- gdb::string_view name, bool copy_name,
- CORE_ADDR address,
- enum minimal_symbol_type ms_type,
- asection *bfd_section, struct objfile *objfile)
- {
- struct gdbarch *gdbarch = objfile->arch ();
- if (ms_type == mst_text || ms_type == mst_file_text
- || ms_type == mst_text_gnu_ifunc)
- address = gdbarch_addr_bits_remove (gdbarch, address);
- /* We only setup section information for allocatable sections. Usually
- we'd only expect to find msymbols for allocatable sections, but if the
- ELF is malformed then this might not be the case. In that case don't
- create an msymbol that references an uninitialised section object. */
- int section_index = 0;
- if ((bfd_section_flags (bfd_section) & SEC_ALLOC) == SEC_ALLOC)
- section_index = gdb_bfd_section_index (objfile->obfd, bfd_section);
- struct minimal_symbol *result
- = reader.record_full (name, copy_name, address, ms_type, section_index);
- if ((objfile->flags & OBJF_MAINLINE) == 0
- && (ms_type == mst_data || ms_type == mst_bss))
- result->maybe_copied = 1;
- return result;
- }
- /* Read the symbol table of an ELF file.
- Given an objfile, a symbol table, and a flag indicating whether the
- symbol table contains regular, dynamic, or synthetic symbols, add all
- the global function and data symbols to the minimal symbol table.
- In stabs-in-ELF, as implemented by Sun, there are some local symbols
- defined in the ELF symbol table, which can be used to locate
- the beginnings of sections from each ".o" file that was linked to
- form the executable objfile. We gather any such info and record it
- in data structures hung off the objfile's private data. */
- #define ST_REGULAR 0
- #define ST_DYNAMIC 1
- #define ST_SYNTHETIC 2
- static void
- elf_symtab_read (minimal_symbol_reader &reader,
- struct objfile *objfile, int type,
- long number_of_symbols, asymbol **symbol_table,
- bool copy_names)
- {
- struct gdbarch *gdbarch = objfile->arch ();
- asymbol *sym;
- long i;
- CORE_ADDR symaddr;
- enum minimal_symbol_type ms_type;
- /* Name of the last file symbol. This is either a constant string or is
- saved on the objfile's filename cache. */
- const char *filesymname = "";
- int stripped = (bfd_get_symcount (objfile->obfd) == 0);
- int elf_make_msymbol_special_p
- = gdbarch_elf_make_msymbol_special_p (gdbarch);
- for (i = 0; i < number_of_symbols; i++)
- {
- sym = symbol_table[i];
- if (sym->name == NULL || *sym->name == '\0')
- {
- /* Skip names that don't exist (shouldn't happen), or names
- that are null strings (may happen). */
- continue;
- }
- elf_symbol_type *elf_sym = (elf_symbol_type *) sym;
- /* Skip "special" symbols, e.g. ARM mapping symbols. These are
- symbols which do not correspond to objects in the symbol table,
- but have some other target-specific meaning. */
- if (bfd_is_target_special_symbol (objfile->obfd, sym))
- {
- if (gdbarch_record_special_symbol_p (gdbarch))
- gdbarch_record_special_symbol (gdbarch, objfile, sym);
- continue;
- }
- if (type == ST_DYNAMIC
- && sym->section == bfd_und_section_ptr
- && (sym->flags & BSF_FUNCTION))
- {
- struct minimal_symbol *msym;
- bfd *abfd = objfile->obfd;
- asection *sect;
- /* Symbol is a reference to a function defined in
- a shared library.
- If its value is non zero then it is usually the address
- of the corresponding entry in the procedure linkage table,
- plus the desired section offset.
- If its value is zero then the dynamic linker has to resolve
- the symbol. We are unable to find any meaningful address
- for this symbol in the executable file, so we skip it. */
- symaddr = sym->value;
- if (symaddr == 0)
- continue;
- /* sym->section is the undefined section. However, we want to
- record the section where the PLT stub resides with the
- minimal symbol. Search the section table for the one that
- covers the stub's address. */
- for (sect = abfd->sections; sect != NULL; sect = sect->next)
- {
- if ((bfd_section_flags (sect) & SEC_ALLOC) == 0)
- continue;
- if (symaddr >= bfd_section_vma (sect)
- && symaddr < bfd_section_vma (sect)
- + bfd_section_size (sect))
- break;
- }
- if (!sect)
- continue;
- /* On ia64-hpux, we have discovered that the system linker
- adds undefined symbols with nonzero addresses that cannot
- be right (their address points inside the code of another
- function in the .text section). This creates problems
- when trying to determine which symbol corresponds to
- a given address.
- We try to detect those buggy symbols by checking which
- section we think they correspond to. Normally, PLT symbols
- are stored inside their own section, and the typical name
- for that section is ".plt". So, if there is a ".plt"
- section, and yet the section name of our symbol does not
- start with ".plt", we ignore that symbol. */
- if (!startswith (sect->name, ".plt")
- && bfd_get_section_by_name (abfd, ".plt") != NULL)
- continue;
- msym = record_minimal_symbol
- (reader, sym->name, copy_names,
- symaddr, mst_solib_trampoline, sect, objfile);
- if (msym != NULL)
- {
- msym->filename = filesymname;
- if (elf_make_msymbol_special_p)
- gdbarch_elf_make_msymbol_special (gdbarch, sym, msym);
- }
- continue;
- }
- /* If it is a nonstripped executable, do not enter dynamic
- symbols, as the dynamic symbol table is usually a subset
- of the main symbol table. */
- if (type == ST_DYNAMIC && !stripped)
- continue;
- if (sym->flags & BSF_FILE)
- filesymname = objfile->intern (sym->name);
- else if (sym->flags & BSF_SECTION_SYM)
- continue;
- else if (sym->flags & (BSF_GLOBAL | BSF_LOCAL | BSF_WEAK
- | BSF_GNU_UNIQUE))
- {
- struct minimal_symbol *msym;
- /* Select global/local/weak symbols. Note that bfd puts abs
- symbols in their own section, so all symbols we are
- interested in will have a section. */
- /* Bfd symbols are section relative. */
- symaddr = sym->value + sym->section->vma;
- /* For non-absolute symbols, use the type of the section
- they are relative to, to intuit text/data. Bfd provides
- no way of figuring this out for absolute symbols. */
- if (sym->section == bfd_abs_section_ptr)
- {
- /* This is a hack to get the minimal symbol type
- right for Irix 5, which has absolute addresses
- with special section indices for dynamic symbols.
- NOTE: uweigand-20071112: Synthetic symbols do not
- have an ELF-private part, so do not touch those. */
- unsigned int shndx = type == ST_SYNTHETIC ? 0 :
- elf_sym->internal_elf_sym.st_shndx;
- switch (shndx)
- {
- case SHN_MIPS_TEXT:
- ms_type = mst_text;
- break;
- case SHN_MIPS_DATA:
- ms_type = mst_data;
- break;
- case SHN_MIPS_ACOMMON:
- ms_type = mst_bss;
- break;
- default:
- ms_type = mst_abs;
- }
- /* If it is an Irix dynamic symbol, skip section name
- symbols, relocate all others by section offset. */
- if (ms_type != mst_abs)
- {
- if (sym->name[0] == '.')
- continue;
- }
- }
- else if (sym->section->flags & SEC_CODE)
- {
- if (sym->flags & (BSF_GLOBAL | BSF_WEAK | BSF_GNU_UNIQUE))
- {
- if (sym->flags & BSF_GNU_INDIRECT_FUNCTION)
- ms_type = mst_text_gnu_ifunc;
- else
- ms_type = mst_text;
- }
- /* The BSF_SYNTHETIC check is there to omit ppc64 function
- descriptors mistaken for static functions starting with 'L'.
- */
- else if ((sym->name[0] == '.' && sym->name[1] == 'L'
- && (sym->flags & BSF_SYNTHETIC) == 0)
- || ((sym->flags & BSF_LOCAL)
- && sym->name[0] == '$'
- && sym->name[1] == 'L'))
- /* Looks like a compiler-generated label. Skip
- it. The assembler should be skipping these (to
- keep executables small), but apparently with
- gcc on the (deleted) delta m88k SVR4, it loses.
- So to have us check too should be harmless (but
- I encourage people to fix this in the assembler
- instead of adding checks here). */
- continue;
- else
- {
- ms_type = mst_file_text;
- }
- }
- else if (sym->section->flags & SEC_ALLOC)
- {
- if (sym->flags & (BSF_GLOBAL | BSF_WEAK | BSF_GNU_UNIQUE))
- {
- if (sym->flags & BSF_GNU_INDIRECT_FUNCTION)
- {
- ms_type = mst_data_gnu_ifunc;
- }
- else if (sym->section->flags & SEC_LOAD)
- {
- ms_type = mst_data;
- }
- else
- {
- ms_type = mst_bss;
- }
- }
- else if (sym->flags & BSF_LOCAL)
- {
- if (sym->section->flags & SEC_LOAD)
- {
- ms_type = mst_file_data;
- }
- else
- {
- ms_type = mst_file_bss;
- }
- }
- else
- {
- ms_type = mst_unknown;
- }
- }
- else
- {
- /* FIXME: Solaris2 shared libraries include lots of
- odd "absolute" and "undefined" symbols, that play
- hob with actions like finding what function the PC
- is in. Ignore them if they aren't text, data, or bss. */
- /* ms_type = mst_unknown; */
- continue; /* Skip this symbol. */
- }
- msym = record_minimal_symbol
- (reader, sym->name, copy_names, symaddr,
- ms_type, sym->section, objfile);
- if (msym)
- {
- /* NOTE: uweigand-20071112: A synthetic symbol does not have an
- ELF-private part. */
- if (type != ST_SYNTHETIC)
- {
- /* Pass symbol size field in via BFD. FIXME!!! */
- SET_MSYMBOL_SIZE (msym, elf_sym->internal_elf_sym.st_size);
- }
- msym->filename = filesymname;
- if (elf_make_msymbol_special_p)
- gdbarch_elf_make_msymbol_special (gdbarch, sym, msym);
- }
- /* If we see a default versioned symbol, install it under
- its version-less name. */
- if (msym != NULL)
- {
- const char *atsign = strchr (sym->name, '@');
- bool is_at_symbol = atsign != nullptr && atsign > sym->name;
- bool is_plt = is_at_symbol && strcmp (atsign, "@plt") == 0;
- int len = is_at_symbol ? atsign - sym->name : 0;
- if (is_at_symbol
- && !is_plt
- && (elf_sym->version & VERSYM_HIDDEN) == 0)
- record_minimal_symbol (reader,
- gdb::string_view (sym->name, len),
- true, symaddr, ms_type, sym->section,
- objfile);
- else if (is_plt)
- {
- /* For @plt symbols, also record a trampoline to the
- destination symbol. The @plt symbol will be used
- in disassembly, and the trampoline will be used
- when we are trying to find the target. */
- if (ms_type == mst_text && type == ST_SYNTHETIC)
- {
- struct minimal_symbol *mtramp;
- mtramp = record_minimal_symbol
- (reader, gdb::string_view (sym->name, len), true,
- symaddr, mst_solib_trampoline, sym->section, objfile);
- if (mtramp)
- {
- SET_MSYMBOL_SIZE (mtramp, MSYMBOL_SIZE (msym));
- mtramp->created_by_gdb = 1;
- mtramp->filename = filesymname;
- if (elf_make_msymbol_special_p)
- gdbarch_elf_make_msymbol_special (gdbarch,
- sym, mtramp);
- }
- }
- }
- }
- }
- }
- }
- /* Build minimal symbols named `function@got.plt' (see SYMBOL_GOT_PLT_SUFFIX)
- for later look ups of which function to call when user requests
- a STT_GNU_IFUNC function. As the STT_GNU_IFUNC type is found at the target
- library defining `function' we cannot yet know while reading OBJFILE which
- of the SYMBOL_GOT_PLT_SUFFIX entries will be needed and later
- DYN_SYMBOL_TABLE is no longer easily available for OBJFILE. */
- static void
- elf_rel_plt_read (minimal_symbol_reader &reader,
- struct objfile *objfile, asymbol **dyn_symbol_table)
- {
- bfd *obfd = objfile->obfd;
- const struct elf_backend_data *bed = get_elf_backend_data (obfd);
- asection *relplt, *got_plt;
- bfd_size_type reloc_count, reloc;
- struct gdbarch *gdbarch = objfile->arch ();
- struct type *ptr_type = builtin_type (gdbarch)->builtin_data_ptr;
- size_t ptr_size = TYPE_LENGTH (ptr_type);
- if (objfile->separate_debug_objfile_backlink)
- return;
- got_plt = bfd_get_section_by_name (obfd, ".got.plt");
- if (got_plt == NULL)
- {
- /* For platforms where there is no separate .got.plt. */
- got_plt = bfd_get_section_by_name (obfd, ".got");
- if (got_plt == NULL)
- return;
- }
- /* Depending on system, we may find jump slots in a relocation
- section for either .got.plt or .plt. */
- asection *plt = bfd_get_section_by_name (obfd, ".plt");
- int plt_elf_idx = (plt != NULL) ? elf_section_data (plt)->this_idx : -1;
- int got_plt_elf_idx = elf_section_data (got_plt)->this_idx;
- /* This search algorithm is from _bfd_elf_canonicalize_dynamic_reloc. */
- for (relplt = obfd->sections; relplt != NULL; relplt = relplt->next)
- {
- const auto &this_hdr = elf_section_data (relplt)->this_hdr;
- if (this_hdr.sh_type == SHT_REL || this_hdr.sh_type == SHT_RELA)
- {
- if (this_hdr.sh_info == plt_elf_idx
- || this_hdr.sh_info == got_plt_elf_idx)
- break;
- }
- }
- if (relplt == NULL)
- return;
- if (! bed->s->slurp_reloc_table (obfd, relplt, dyn_symbol_table, TRUE))
- return;
- std::string string_buffer;
- /* Does ADDRESS reside in SECTION of OBFD? */
- auto within_section = [obfd] (asection *section, CORE_ADDR address)
- {
- if (section == NULL)
- return false;
- return (bfd_section_vma (section) <= address
- && (address < bfd_section_vma (section)
- + bfd_section_size (section)));
- };
- reloc_count = relplt->size / elf_section_data (relplt)->this_hdr.sh_entsize;
- for (reloc = 0; reloc < reloc_count; reloc++)
- {
- const char *name;
- struct minimal_symbol *msym;
- CORE_ADDR address;
- const char *got_suffix = SYMBOL_GOT_PLT_SUFFIX;
- const size_t got_suffix_len = strlen (SYMBOL_GOT_PLT_SUFFIX);
- name = bfd_asymbol_name (*relplt->relocation[reloc].sym_ptr_ptr);
- address = relplt->relocation[reloc].address;
- asection *msym_section;
- /* Does the pointer reside in either the .got.plt or .plt
- sections? */
- if (within_section (got_plt, address))
- msym_section = got_plt;
- else if (within_section (plt, address))
- msym_section = plt;
- else
- continue;
- /* We cannot check if NAME is a reference to
- mst_text_gnu_ifunc/mst_data_gnu_ifunc as in OBJFILE the
- symbol is undefined and the objfile having NAME defined may
- not yet have been loaded. */
- string_buffer.assign (name);
- string_buffer.append (got_suffix, got_suffix + got_suffix_len);
- msym = record_minimal_symbol (reader, string_buffer,
- true, address, mst_slot_got_plt,
- msym_section, objfile);
- if (msym)
- SET_MSYMBOL_SIZE (msym, ptr_size);
- }
- }
- /* The data pointer is htab_t for gnu_ifunc_record_cache_unchecked. */
- static const struct objfile_key<htab, htab_deleter>
- elf_objfile_gnu_ifunc_cache_data;
- /* Map function names to CORE_ADDR in elf_objfile_gnu_ifunc_cache_data. */
- struct elf_gnu_ifunc_cache
- {
- /* This is always a function entry address, not a function descriptor. */
- CORE_ADDR addr;
- char name[1];
- };
- /* htab_hash for elf_objfile_gnu_ifunc_cache_data. */
- static hashval_t
- elf_gnu_ifunc_cache_hash (const void *a_voidp)
- {
- const struct elf_gnu_ifunc_cache *a
- = (const struct elf_gnu_ifunc_cache *) a_voidp;
- return htab_hash_string (a->name);
- }
- /* htab_eq for elf_objfile_gnu_ifunc_cache_data. */
- static int
- elf_gnu_ifunc_cache_eq (const void *a_voidp, const void *b_voidp)
- {
- const struct elf_gnu_ifunc_cache *a
- = (const struct elf_gnu_ifunc_cache *) a_voidp;
- const struct elf_gnu_ifunc_cache *b
- = (const struct elf_gnu_ifunc_cache *) b_voidp;
- return strcmp (a->name, b->name) == 0;
- }
- /* Record the target function address of a STT_GNU_IFUNC function NAME is the
- function entry address ADDR. Return 1 if NAME and ADDR are considered as
- valid and therefore they were successfully recorded, return 0 otherwise.
- Function does not expect a duplicate entry. Use
- elf_gnu_ifunc_resolve_by_cache first to check if the entry for NAME already
- exists. */
- static int
- elf_gnu_ifunc_record_cache (const char *name, CORE_ADDR addr)
- {
- struct bound_minimal_symbol msym;
- struct objfile *objfile;
- htab_t htab;
- struct elf_gnu_ifunc_cache entry_local, *entry_p;
- void **slot;
- msym = lookup_minimal_symbol_by_pc (addr);
- if (msym.minsym == NULL)
- return 0;
- if (BMSYMBOL_VALUE_ADDRESS (msym) != addr)
- return 0;
- objfile = msym.objfile;
- /* If .plt jumps back to .plt the symbol is still deferred for later
- resolution and it has no use for GDB. */
- const char *target_name = msym.minsym->linkage_name ();
- size_t len = strlen (target_name);
- /* Note we check the symbol's name instead of checking whether the
- symbol is in the .plt section because some systems have @plt
- symbols in the .text section. */
- if (len > 4 && strcmp (target_name + len - 4, "@plt") == 0)
- return 0;
- htab = elf_objfile_gnu_ifunc_cache_data.get (objfile);
- if (htab == NULL)
- {
- htab = htab_create_alloc (1, elf_gnu_ifunc_cache_hash,
- elf_gnu_ifunc_cache_eq,
- NULL, xcalloc, xfree);
- elf_objfile_gnu_ifunc_cache_data.set (objfile, htab);
- }
- entry_local.addr = addr;
- obstack_grow (&objfile->objfile_obstack, &entry_local,
- offsetof (struct elf_gnu_ifunc_cache, name));
- obstack_grow_str0 (&objfile->objfile_obstack, name);
- entry_p
- = (struct elf_gnu_ifunc_cache *) obstack_finish (&objfile->objfile_obstack);
- slot = htab_find_slot (htab, entry_p, INSERT);
- if (*slot != NULL)
- {
- struct elf_gnu_ifunc_cache *entry_found_p
- = (struct elf_gnu_ifunc_cache *) *slot;
- struct gdbarch *gdbarch = objfile->arch ();
- if (entry_found_p->addr != addr)
- {
- /* This case indicates buggy inferior program, the resolved address
- should never change. */
- warning (_("gnu-indirect-function \"%s\" has changed its resolved "
- "function_address from %s to %s"),
- name, paddress (gdbarch, entry_found_p->addr),
- paddress (gdbarch, addr));
- }
- /* New ENTRY_P is here leaked/duplicate in the OBJFILE obstack. */
- }
- *slot = entry_p;
- return 1;
- }
- /* Try to find the target resolved function entry address of a STT_GNU_IFUNC
- function NAME. If the address is found it is stored to *ADDR_P (if ADDR_P
- is not NULL) and the function returns 1. It returns 0 otherwise.
- Only the elf_objfile_gnu_ifunc_cache_data hash table is searched by this
- function. */
- static int
- elf_gnu_ifunc_resolve_by_cache (const char *name, CORE_ADDR *addr_p)
- {
- for (objfile *objfile : current_program_space->objfiles ())
- {
- htab_t htab;
- struct elf_gnu_ifunc_cache *entry_p;
- void **slot;
- htab = elf_objfile_gnu_ifunc_cache_data.get (objfile);
- if (htab == NULL)
- continue;
- entry_p = ((struct elf_gnu_ifunc_cache *)
- alloca (sizeof (*entry_p) + strlen (name)));
- strcpy (entry_p->name, name);
- slot = htab_find_slot (htab, entry_p, NO_INSERT);
- if (slot == NULL)
- continue;
- entry_p = (struct elf_gnu_ifunc_cache *) *slot;
- gdb_assert (entry_p != NULL);
- if (addr_p)
- *addr_p = entry_p->addr;
- return 1;
- }
- return 0;
- }
- /* Try to find the target resolved function entry address of a STT_GNU_IFUNC
- function NAME. If the address is found it is stored to *ADDR_P (if ADDR_P
- is not NULL) and the function returns 1. It returns 0 otherwise.
- Only the SYMBOL_GOT_PLT_SUFFIX locations are searched by this function.
- elf_gnu_ifunc_resolve_by_cache must have been already called for NAME to
- prevent cache entries duplicates. */
- static int
- elf_gnu_ifunc_resolve_by_got (const char *name, CORE_ADDR *addr_p)
- {
- char *name_got_plt;
- const size_t got_suffix_len = strlen (SYMBOL_GOT_PLT_SUFFIX);
- name_got_plt = (char *) alloca (strlen (name) + got_suffix_len + 1);
- sprintf (name_got_plt, "%s" SYMBOL_GOT_PLT_SUFFIX, name);
- for (objfile *objfile : current_program_space->objfiles ())
- {
- bfd *obfd = objfile->obfd;
- struct gdbarch *gdbarch = objfile->arch ();
- struct type *ptr_type = builtin_type (gdbarch)->builtin_data_ptr;
- size_t ptr_size = TYPE_LENGTH (ptr_type);
- CORE_ADDR pointer_address, addr;
- asection *plt;
- gdb_byte *buf = (gdb_byte *) alloca (ptr_size);
- struct bound_minimal_symbol msym;
- msym = lookup_minimal_symbol (name_got_plt, NULL, objfile);
- if (msym.minsym == NULL)
- continue;
- if (MSYMBOL_TYPE (msym.minsym) != mst_slot_got_plt)
- continue;
- pointer_address = BMSYMBOL_VALUE_ADDRESS (msym);
- plt = bfd_get_section_by_name (obfd, ".plt");
- if (plt == NULL)
- continue;
- if (MSYMBOL_SIZE (msym.minsym) != ptr_size)
- continue;
- if (target_read_memory (pointer_address, buf, ptr_size) != 0)
- continue;
- addr = extract_typed_address (buf, ptr_type);
- addr = gdbarch_convert_from_func_ptr_addr
- (gdbarch, addr, current_inferior ()->top_target ());
- addr = gdbarch_addr_bits_remove (gdbarch, addr);
- if (elf_gnu_ifunc_record_cache (name, addr))
- {
- if (addr_p != NULL)
- *addr_p = addr;
- return 1;
- }
- }
- return 0;
- }
- /* Try to find the target resolved function entry address of a STT_GNU_IFUNC
- function NAME. If the address is found it is stored to *ADDR_P (if ADDR_P
- is not NULL) and the function returns true. It returns false otherwise.
- Both the elf_objfile_gnu_ifunc_cache_data hash table and
- SYMBOL_GOT_PLT_SUFFIX locations are searched by this function. */
- static bool
- elf_gnu_ifunc_resolve_name (const char *name, CORE_ADDR *addr_p)
- {
- if (elf_gnu_ifunc_resolve_by_cache (name, addr_p))
- return true;
- if (elf_gnu_ifunc_resolve_by_got (name, addr_p))
- return true;
- return false;
- }
- /* Call STT_GNU_IFUNC - a function returning addresss of a real function to
- call. PC is theSTT_GNU_IFUNC resolving function entry. The value returned
- is the entry point of the resolved STT_GNU_IFUNC target function to call.
- */
- static CORE_ADDR
- elf_gnu_ifunc_resolve_addr (struct gdbarch *gdbarch, CORE_ADDR pc)
- {
- const char *name_at_pc;
- CORE_ADDR start_at_pc, address;
- struct type *func_func_type = builtin_type (gdbarch)->builtin_func_func;
- struct value *function, *address_val;
- CORE_ADDR hwcap = 0;
- struct value *hwcap_val;
- /* Try first any non-intrusive methods without an inferior call. */
- if (find_pc_partial_function (pc, &name_at_pc, &start_at_pc, NULL)
- && start_at_pc == pc)
- {
- if (elf_gnu_ifunc_resolve_name (name_at_pc, &address))
- return address;
- }
- else
- name_at_pc = NULL;
- function = allocate_value (func_func_type);
- VALUE_LVAL (function) = lval_memory;
- set_value_address (function, pc);
- /* STT_GNU_IFUNC resolver functions usually receive the HWCAP vector as
- parameter. FUNCTION is the function entry address. ADDRESS may be a
- function descriptor. */
- target_auxv_search (current_inferior ()->top_target (), AT_HWCAP, &hwcap);
- hwcap_val = value_from_longest (builtin_type (gdbarch)
- ->builtin_unsigned_long, hwcap);
- address_val = call_function_by_hand (function, NULL, hwcap_val);
- address = value_as_address (address_val);
- address = gdbarch_convert_from_func_ptr_addr
- (gdbarch, address, current_inferior ()->top_target ());
- address = gdbarch_addr_bits_remove (gdbarch, address);
- if (name_at_pc)
- elf_gnu_ifunc_record_cache (name_at_pc, address);
- return address;
- }
- /* Handle inferior hit of bp_gnu_ifunc_resolver, see its definition. */
- static void
- elf_gnu_ifunc_resolver_stop (struct breakpoint *b)
- {
- struct breakpoint *b_return;
- struct frame_info *prev_frame = get_prev_frame (get_current_frame ());
- struct frame_id prev_frame_id = get_stack_frame_id (prev_frame);
- CORE_ADDR prev_pc = get_frame_pc (prev_frame);
- int thread_id = inferior_thread ()->global_num;
- gdb_assert (b->type == bp_gnu_ifunc_resolver);
- for (b_return = b->related_breakpoint; b_return != b;
- b_return = b_return->related_breakpoint)
- {
- gdb_assert (b_return->type == bp_gnu_ifunc_resolver_return);
- gdb_assert (b_return->loc != NULL && b_return->loc->next == NULL);
- gdb_assert (frame_id_p (b_return->frame_id));
- if (b_return->thread == thread_id
- && b_return->loc->requested_address == prev_pc
- && frame_id_eq (b_return->frame_id, prev_frame_id))
- break;
- }
- if (b_return == b)
- {
- /* No need to call find_pc_line for symbols resolving as this is only
- a helper breakpointer never shown to the user. */
- symtab_and_line sal;
- sal.pspace = current_inferior ()->pspace;
- sal.pc = prev_pc;
- sal.section = find_pc_overlay (sal.pc);
- sal.explicit_pc = 1;
- b_return
- = set_momentary_breakpoint (get_frame_arch (prev_frame), sal,
- prev_frame_id,
- bp_gnu_ifunc_resolver_return).release ();
- /* set_momentary_breakpoint invalidates PREV_FRAME. */
- prev_frame = NULL;
- /* Add new b_return to the ring list b->related_breakpoint. */
- gdb_assert (b_return->related_breakpoint == b_return);
- b_return->related_breakpoint = b->related_breakpoint;
- b->related_breakpoint = b_return;
- }
- }
- /* Handle inferior hit of bp_gnu_ifunc_resolver_return, see its definition. */
- static void
- elf_gnu_ifunc_resolver_return_stop (struct breakpoint *b)
- {
- thread_info *thread = inferior_thread ();
- struct gdbarch *gdbarch = get_frame_arch (get_current_frame ());
- struct type *func_func_type = builtin_type (gdbarch)->builtin_func_func;
- struct type *value_type = TYPE_TARGET_TYPE (func_func_type);
- struct regcache *regcache = get_thread_regcache (thread);
- struct value *func_func;
- struct value *value;
- CORE_ADDR resolved_address, resolved_pc;
- gdb_assert (b->type == bp_gnu_ifunc_resolver_return);
- while (b->related_breakpoint != b)
- {
- struct breakpoint *b_next = b->related_breakpoint;
- switch (b->type)
- {
- case bp_gnu_ifunc_resolver:
- break;
- case bp_gnu_ifunc_resolver_return:
- delete_breakpoint (b);
- break;
- default:
- internal_error (__FILE__, __LINE__,
- _("handle_inferior_event: Invalid "
- "gnu-indirect-function breakpoint type %d"),
- (int) b->type);
- }
- b = b_next;
- }
- gdb_assert (b->type == bp_gnu_ifunc_resolver);
- gdb_assert (b->loc->next == NULL);
- func_func = allocate_value (func_func_type);
- VALUE_LVAL (func_func) = lval_memory;
- set_value_address (func_func, b->loc->related_address);
- value = allocate_value (value_type);
- gdbarch_return_value (gdbarch, func_func, value_type, regcache,
- value_contents_raw (value).data (), NULL);
- resolved_address = value_as_address (value);
- resolved_pc = gdbarch_convert_from_func_ptr_addr
- (gdbarch, resolved_address, current_inferior ()->top_target ());
- resolved_pc = gdbarch_addr_bits_remove (gdbarch, resolved_pc);
- gdb_assert (current_program_space == b->pspace || b->pspace == NULL);
- elf_gnu_ifunc_record_cache (event_location_to_string (b->location.get ()),
- resolved_pc);
- b->type = bp_breakpoint;
- update_breakpoint_locations (b, current_program_space,
- find_function_start_sal (resolved_pc, NULL, true),
- {});
- }
- /* A helper function for elf_symfile_read that reads the minimal
- symbols. */
- static void
- elf_read_minimal_symbols (struct objfile *objfile, int symfile_flags,
- const struct elfinfo *ei)
- {
- bfd *synth_abfd, *abfd = objfile->obfd;
- long symcount = 0, dynsymcount = 0, synthcount, storage_needed;
- asymbol **symbol_table = NULL, **dyn_symbol_table = NULL;
- asymbol *synthsyms;
- if (symtab_create_debug)
- {
- gdb_printf (gdb_stdlog,
- "Reading minimal symbols of objfile %s ...\n",
- objfile_name (objfile));
- }
- /* If we already have minsyms, then we can skip some work here.
- However, if there were stabs or mdebug sections, we go ahead and
- redo all the work anyway, because the psym readers for those
- kinds of debuginfo need extra information found here. This can
- go away once all types of symbols are in the per-BFD object. */
- if (objfile->per_bfd->minsyms_read
- && ei->stabsect == NULL
- && ei->mdebugsect == NULL
- && ei->ctfsect == NULL)
- {
- if (symtab_create_debug)
- gdb_printf (gdb_stdlog,
- "... minimal symbols previously read\n");
- return;
- }
- minimal_symbol_reader reader (objfile);
- /* Process the normal ELF symbol table first. */
- storage_needed = bfd_get_symtab_upper_bound (objfile->obfd);
- if (storage_needed < 0)
- error (_("Can't read symbols from %s: %s"),
- bfd_get_filename (objfile->obfd),
- bfd_errmsg (bfd_get_error ()));
- if (storage_needed > 0)
- {
- /* Memory gets permanently referenced from ABFD after
- bfd_canonicalize_symtab so it must not get freed before ABFD gets. */
- symbol_table = (asymbol **) bfd_alloc (abfd, storage_needed);
- symcount = bfd_canonicalize_symtab (objfile->obfd, symbol_table);
- if (symcount < 0)
- error (_("Can't read symbols from %s: %s"),
- bfd_get_filename (objfile->obfd),
- bfd_errmsg (bfd_get_error ()));
- elf_symtab_read (reader, objfile, ST_REGULAR, symcount, symbol_table,
- false);
- }
- /* Add the dynamic symbols. */
- storage_needed = bfd_get_dynamic_symtab_upper_bound (objfile->obfd);
- if (storage_needed > 0)
- {
- /* Memory gets permanently referenced from ABFD after
- bfd_get_synthetic_symtab so it must not get freed before ABFD gets.
- It happens only in the case when elf_slurp_reloc_table sees
- asection->relocation NULL. Determining which section is asection is
- done by _bfd_elf_get_synthetic_symtab which is all a bfd
- implementation detail, though. */
- dyn_symbol_table = (asymbol **) bfd_alloc (abfd, storage_needed);
- dynsymcount = bfd_canonicalize_dynamic_symtab (objfile->obfd,
- dyn_symbol_table);
- if (dynsymcount < 0)
- error (_("Can't read symbols from %s: %s"),
- bfd_get_filename (objfile->obfd),
- bfd_errmsg (bfd_get_error ()));
- elf_symtab_read (reader, objfile, ST_DYNAMIC, dynsymcount,
- dyn_symbol_table, false);
- elf_rel_plt_read (reader, objfile, dyn_symbol_table);
- }
- /* Contrary to binutils --strip-debug/--only-keep-debug the strip command from
- elfutils (eu-strip) moves even the .symtab section into the .debug file.
- bfd_get_synthetic_symtab on ppc64 for each function descriptor ELF symbol
- 'name' creates a new BSF_SYNTHETIC ELF symbol '.name' with its code
- address. But with eu-strip files bfd_get_synthetic_symtab would fail to
- read the code address from .opd while it reads the .symtab section from
- a separate debug info file as the .opd section is SHT_NOBITS there.
- With SYNTH_ABFD the .opd section will be read from the original
- backlinked binary where it is valid. */
- if (objfile->separate_debug_objfile_backlink)
- synth_abfd = objfile->separate_debug_objfile_backlink->obfd;
- else
- synth_abfd = abfd;
- /* Add synthetic symbols - for instance, names for any PLT entries. */
- synthcount = bfd_get_synthetic_symtab (synth_abfd, symcount, symbol_table,
- dynsymcount, dyn_symbol_table,
- &synthsyms);
- if (synthcount > 0)
- {
- long i;
- std::unique_ptr<asymbol *[]>
- synth_symbol_table (new asymbol *[synthcount]);
- for (i = 0; i < synthcount; i++)
- synth_symbol_table[i] = synthsyms + i;
- elf_symtab_read (reader, objfile, ST_SYNTHETIC, synthcount,
- synth_symbol_table.get (), true);
- xfree (synthsyms);
- synthsyms = NULL;
- }
- /* Install any minimal symbols that have been collected as the current
- minimal symbols for this objfile. The debug readers below this point
- should not generate new minimal symbols; if they do it's their
- responsibility to install them. "mdebug" appears to be the only one
- which will do this. */
- reader.install ();
- if (symtab_create_debug)
- gdb_printf (gdb_stdlog, "Done reading minimal symbols.\n");
- }
- /* Scan and build partial symbols for a symbol file.
- We have been initialized by a call to elf_symfile_init, which
- currently does nothing.
- This function only does the minimum work necessary for letting the
- user "name" things symbolically; it does not read the entire symtab.
- Instead, it reads the external and static symbols and puts them in partial
- symbol tables. When more extensive information is requested of a
- file, the corresponding partial symbol table is mutated into a full
- fledged symbol table by going back and reading the symbols
- for real.
- We look for sections with specific names, to tell us what debug
- format to look for: FIXME!!!
- elfstab_build_psymtabs() handles STABS symbols;
- mdebug_build_psymtabs() handles ECOFF debugging information.
- Note that ELF files have a "minimal" symbol table, which looks a lot
- like a COFF symbol table, but has only the minimal information necessary
- for linking. We process this also, and use the information to
- build gdb's minimal symbol table. This gives us some minimal debugging
- capability even for files compiled without -g. */
- static void
- elf_symfile_read (struct objfile *objfile, symfile_add_flags symfile_flags)
- {
- bfd *abfd = objfile->obfd;
- struct elfinfo ei;
- bool has_dwarf2 = true;
- memset ((char *) &ei, 0, sizeof (ei));
- if (!(objfile->flags & OBJF_READNEVER))
- {
- for (asection *sect : gdb_bfd_sections (abfd))
- elf_locate_sections (sect, &ei);
- }
- elf_read_minimal_symbols (objfile, symfile_flags, &ei);
- /* ELF debugging information is inserted into the psymtab in the
- order of least informative first - most informative last. Since
- the psymtab table is searched `most recent insertion first' this
- increases the probability that more detailed debug information
- for a section is found.
- For instance, an object file might contain both .mdebug (XCOFF)
- and .debug_info (DWARF2) sections then .mdebug is inserted first
- (searched last) and DWARF2 is inserted last (searched first). If
- we don't do this then the XCOFF info is found first - for code in
- an included file XCOFF info is useless. */
- if (ei.mdebugsect)
- {
- const struct ecoff_debug_swap *swap;
- /* .mdebug section, presumably holding ECOFF debugging
- information. */
- swap = get_elf_backend_data (abfd)->elf_backend_ecoff_debug_swap;
- if (swap)
- elfmdebug_build_psymtabs (objfile, swap, ei.mdebugsect);
- }
- if (ei.stabsect)
- {
- asection *str_sect;
- /* Stab sections have an associated string table that looks like
- a separate section. */
- str_sect = bfd_get_section_by_name (abfd, ".stabstr");
- /* FIXME should probably warn about a stab section without a stabstr. */
- if (str_sect)
- elfstab_build_psymtabs (objfile,
- ei.stabsect,
- str_sect->filepos,
- bfd_section_size (str_sect));
- }
- if (dwarf2_has_info (objfile, NULL, true))
- dwarf2_initialize_objfile (objfile);
- /* If the file has its own symbol tables it has no separate debug
- info. `.dynsym'/`.symtab' go to MSYMBOLS, `.debug_info' goes to
- SYMTABS/PSYMTABS. `.gnu_debuglink' may no longer be present with
- `.note.gnu.build-id'.
- .gnu_debugdata is !objfile::has_partial_symbols because it contains only
- .symtab, not .debug_* section. But if we already added .gnu_debugdata as
- an objfile via find_separate_debug_file_in_section there was no separate
- debug info available. Therefore do not attempt to search for another one,
- objfile->separate_debug_objfile->separate_debug_objfile GDB guarantees to
- be NULL and we would possibly violate it. */
- else if (!objfile->has_partial_symbols ()
- && objfile->separate_debug_objfile == NULL
- && objfile->separate_debug_objfile_backlink == NULL)
- {
- std::string debugfile = find_separate_debug_file_by_buildid (objfile);
- if (debugfile.empty ())
- debugfile = find_separate_debug_file_by_debuglink (objfile);
- if (!debugfile.empty ())
- {
- gdb_bfd_ref_ptr debug_bfd (symfile_bfd_open (debugfile.c_str ()));
- symbol_file_add_separate (debug_bfd.get (), debugfile.c_str (),
- symfile_flags, objfile);
- }
- else
- {
- has_dwarf2 = false;
- const struct bfd_build_id *build_id = build_id_bfd_get (objfile->obfd);
- if (build_id != nullptr)
- {
- gdb::unique_xmalloc_ptr<char> symfile_path;
- scoped_fd fd (debuginfod_debuginfo_query (build_id->data,
- build_id->size,
- objfile->original_name,
- &symfile_path));
- if (fd.get () >= 0)
- {
- /* File successfully retrieved from server. */
- gdb_bfd_ref_ptr debug_bfd (symfile_bfd_open (symfile_path.get ()));
- if (debug_bfd == nullptr)
- warning (_("File \"%s\" from debuginfod cannot be opened as bfd"),
- objfile->original_name);
- else if (build_id_verify (debug_bfd.get (), build_id->size, build_id->data))
- {
- symbol_file_add_separate (debug_bfd.get (), symfile_path.get (),
- symfile_flags, objfile);
- has_dwarf2 = true;
- }
- }
- }
- }
- }
- /* Read the CTF section only if there is no DWARF info. */
- if (!has_dwarf2 && ei.ctfsect)
- {
- elfctf_build_psymtabs (objfile);
- }
- }
- /* Initialize anything that needs initializing when a completely new symbol
- file is specified (not just adding some symbols from another file, e.g. a
- shared library). */
- static void
- elf_new_init (struct objfile *ignore)
- {
- }
- /* Perform any local cleanups required when we are done with a particular
- objfile. I.E, we are in the process of discarding all symbol information
- for an objfile, freeing up all memory held for it, and unlinking the
- objfile struct from the global list of known objfiles. */
- static void
- elf_symfile_finish (struct objfile *objfile)
- {
- }
- /* ELF specific initialization routine for reading symbols. */
- static void
- elf_symfile_init (struct objfile *objfile)
- {
- /* ELF objects may be reordered, so set OBJF_REORDERED. If we
- find this causes a significant slowdown in gdb then we could
- set it in the debug symbol readers only when necessary. */
- objfile->flags |= OBJF_REORDERED;
- }
- /* Implementation of `sym_get_probes', as documented in symfile.h. */
- static const elfread_data &
- elf_get_probes (struct objfile *objfile)
- {
- elfread_data *probes_per_bfd = probe_key.get (objfile->obfd);
- if (probes_per_bfd == NULL)
- {
- probes_per_bfd = probe_key.emplace (objfile->obfd);
- /* Here we try to gather information about all types of probes from the
- objfile. */
- for (const static_probe_ops *ops : all_static_probe_ops)
- ops->get_probes (probes_per_bfd, objfile);
- }
- return *probes_per_bfd;
- }
- /* Implementation `sym_probe_fns', as documented in symfile.h. */
- static const struct sym_probe_fns elf_probe_fns =
- {
- elf_get_probes, /* sym_get_probes */
- };
- /* Register that we are able to handle ELF object file formats. */
- static const struct sym_fns elf_sym_fns =
- {
- elf_new_init, /* init anything gbl to entire symtab */
- elf_symfile_init, /* read initial info, setup for sym_read() */
- elf_symfile_read, /* read a symbol file into symtab */
- elf_symfile_finish, /* finished with file, cleanup */
- default_symfile_offsets, /* Translate ext. to int. relocation */
- elf_symfile_segments, /* Get segment information from a file. */
- NULL,
- default_symfile_relocate, /* Relocate a debug section. */
- &elf_probe_fns, /* sym_probe_fns */
- };
- /* STT_GNU_IFUNC resolver vector to be installed to gnu_ifunc_fns_p. */
- static const struct gnu_ifunc_fns elf_gnu_ifunc_fns =
- {
- elf_gnu_ifunc_resolve_addr,
- elf_gnu_ifunc_resolve_name,
- elf_gnu_ifunc_resolver_stop,
- elf_gnu_ifunc_resolver_return_stop
- };
- void _initialize_elfread ();
- void
- _initialize_elfread ()
- {
- add_symtab_fns (bfd_target_elf_flavour, &elf_sym_fns);
- gnu_ifunc_fns_p = &elf_gnu_ifunc_fns;
- }
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