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- /* DWARF2 EH unwinding support for MIPS Linux.
- Copyright (C) 2004-2022 Free Software Foundation, Inc.
- This file is part of GCC.
- GCC 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, or (at your option)
- any later version.
- GCC 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.
- Under Section 7 of GPL version 3, you are granted additional
- permissions described in the GCC Runtime Library Exception, version
- 3.1, as published by the Free Software Foundation.
- You should have received a copy of the GNU General Public License and
- a copy of the GCC Runtime Library Exception along with this program;
- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
- <http://www.gnu.org/licenses/>. */
- #ifndef inhibit_libc
- /* Do code reading to identify a signal frame, and set the frame
- state data appropriately. See unwind-dw2.c for the structs. */
- #include <signal.h>
- #include <sys/syscall.h>
- /* The third parameter to the signal handler points to something with
- * this structure defined in asm/ucontext.h, but the name clashes with
- * struct ucontext from sys/ucontext.h so this private copy is used. */
- typedef struct _sig_ucontext {
- unsigned long uc_flags;
- struct _sig_ucontext *uc_link;
- stack_t uc_stack;
- struct sigcontext uc_mcontext;
- sigset_t uc_sigmask;
- } _sig_ucontext_t;
- #define MD_FALLBACK_FRAME_STATE_FOR mips_fallback_frame_state
- static _Unwind_Reason_Code
- mips_fallback_frame_state (struct _Unwind_Context *context,
- _Unwind_FrameState *fs)
- {
- u_int32_t *pc = (u_int32_t *) context->ra;
- struct sigcontext *sc;
- _Unwind_Ptr new_cfa, reg_offset;
- int i;
- /* A MIPS16 or microMIPS frame. Signal frames always use the standard
- ISA encoding. */
- if ((_Unwind_Ptr) pc & 3)
- return _URC_END_OF_STACK;
- /* 24021061 li v0, 0x1061 (rt_sigreturn)*/
- /* 0000000c syscall */
- /* or */
- /* 24021017 li v0, 0x1017 (sigreturn) */
- /* 0000000c syscall */
- if (pc[1] != 0x0000000c)
- return _URC_END_OF_STACK;
- #if _MIPS_SIM == _ABIO32
- if (pc[0] == (0x24020000 | __NR_sigreturn))
- {
- struct sigframe {
- u_int32_t ass[4]; /* Argument save space for o32. */
- u_int32_t trampoline[2];
- struct sigcontext sigctx;
- } *rt_ = context->cfa;
- sc = &rt_->sigctx;
- }
- else
- #endif
- if (pc[0] == (0x24020000 | __NR_rt_sigreturn))
- {
- struct rt_sigframe {
- u_int32_t ass[4]; /* Argument save space for o32. */
- u_int32_t trampoline[2];
- siginfo_t info;
- _sig_ucontext_t uc;
- } *rt_ = context->cfa;
- sc = &rt_->uc.uc_mcontext;
- }
- else
- return _URC_END_OF_STACK;
- new_cfa = (_Unwind_Ptr) sc;
- fs->regs.cfa_how = CFA_REG_OFFSET;
- fs->regs.cfa_reg = __LIBGCC_STACK_POINTER_REGNUM__;
- fs->regs.cfa_offset = new_cfa - (_Unwind_Ptr) context->cfa;
- /* On o32 Linux, the register save slots in the sigcontext are
- eight bytes. We need the lower half of each register slot,
- so slide our view of the structure back four bytes. */
- #if _MIPS_SIM == _ABIO32 && defined __MIPSEB__
- reg_offset = 4;
- #else
- reg_offset = 0;
- #endif
- for (i = 0; i < 32; i++) {
- fs->regs.reg[i].how = REG_SAVED_OFFSET;
- fs->regs.reg[i].loc.offset
- = (_Unwind_Ptr)&(sc->sc_regs[i]) + reg_offset - new_cfa;
- }
- /* "PC & -2" points to the faulting instruction, but the unwind code
- searches for "(ADDR & -2) - 1". (See MASK_RETURN_ADDR for the source
- of the -2 mask.) Adding 2 here ensures that "(ADDR & -2) - 1" is the
- address of the second byte of the faulting instruction.
- Note that setting fs->signal_frame would not work. As the comment
- above MASK_RETURN_ADDR explains, MIPS unwinders must earch for an
- odd-valued address. */
- fs->regs.reg[__LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__].how
- = REG_SAVED_VAL_OFFSET;
- fs->regs.reg[__LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__].loc.offset
- = (_Unwind_Ptr)(sc->sc_pc) + 2 - new_cfa;
- fs->retaddr_column = __LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__;
- return _URC_NO_REASON;
- }
- #endif
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