procyberian/gcc
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions
gcc/libgcc/config/i386/linux-unwind.h
Roman Kagan e129b8d768 libgcc: i386/linux-unwind.h: always rely on sys/ucontext.h 
When gcc is built for x86_64-linux-musl target, stack unwinding from
within signal handler stops at the innermost signal frame.  The reason
for this behaviro is that the signal trampoline is not accompanied with
appropiate CFI directives, and the fallback path in libgcc to recognize
it by the code sequence is only enabled for glibc except 2.0.  The
latter is motivated by the lack of sys/ucontext.h in that glibc version.

Given that all relevant libc-s ship sys/ucontext.h for over a decade,
and that other arches aren't shy of unconditionally using it, follow
suit and remove the preprocessor condition, too.

libgcc/ChangeLog:

	* config/i386/linux-unwind.h: Remove preprocessor
	condition to enable fallback path for all libc-s.

Signed-off-by: Roman Kagan <rkagan@amazon.de>
2025-02-18 20:35:42 +01:00

196 lines
6.8 KiB
C
Raw Permalink Blame History

/* DWARF2 EH unwinding support for AMD x86-64 and x86.
Copyright (C) 2004-2025 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/>. */
/* Unwind shadow stack for -fcf-protection -mshstk. */
#if defined __SHSTK__ && defined __CET__ && (__CET__ & 2) != 0
# include "config/i386/shadow-stack-unwind.h"
#endif
/* Do code reading to identify a signal frame, and set the frame
state data appropriately. See unwind-dw2.c for the structs.
Don't use this at all if inhibit_libc is used. */
#ifndef inhibit_libc
#include <signal.h>
#include <sys/ucontext.h>
#ifdef __x86_64__
#define MD_FALLBACK_FRAME_STATE_FOR x86_64_fallback_frame_state
static _Unwind_Reason_Code
x86_64_fallback_frame_state (struct _Unwind_Context *context,
_Unwind_FrameState *fs)
{
unsigned char *pc = context->ra;
struct sigcontext *sc;
long new_cfa;
/* movq $__NR_rt_sigreturn, %rax ; syscall. */
#ifdef __LP64__
#define RT_SIGRETURN_SYSCALL 0x050f0000000fc0c7ULL
#else
#define RT_SIGRETURN_SYSCALL 0x050f40000201c0c7ULL
#endif
if (*(unsigned char *)(pc+0) == 0x48
&& *(unsigned long long *)(pc+1) == RT_SIGRETURN_SYSCALL)
{
ucontext_t *uc_ = context->cfa;
/* The void * cast is necessary to avoid an aliasing warning.
The aliasing warning is correct, but should not be a problem
because it does not alias anything. */
sc = (struct sigcontext *) (void *) &uc_->uc_mcontext;
}
else
return _URC_END_OF_STACK;
new_cfa = sc->rsp;
fs->regs.cfa_how = CFA_REG_OFFSET;
/* Register 7 is rsp */
fs->regs.cfa_reg = 7;
fs->regs.cfa_offset = new_cfa - (long) context->cfa;
/* The SVR4 register numbering macros aren't usable in libgcc. */
fs->regs.how[0] = REG_SAVED_OFFSET;
fs->regs.reg[0].loc.offset = (long)&sc->rax - new_cfa;
fs->regs.how[1] = REG_SAVED_OFFSET;
fs->regs.reg[1].loc.offset = (long)&sc->rdx - new_cfa;
fs->regs.how[2] = REG_SAVED_OFFSET;
fs->regs.reg[2].loc.offset = (long)&sc->rcx - new_cfa;
fs->regs.how[3] = REG_SAVED_OFFSET;
fs->regs.reg[3].loc.offset = (long)&sc->rbx - new_cfa;
fs->regs.how[4] = REG_SAVED_OFFSET;
fs->regs.reg[4].loc.offset = (long)&sc->rsi - new_cfa;
fs->regs.how[5] = REG_SAVED_OFFSET;
fs->regs.reg[5].loc.offset = (long)&sc->rdi - new_cfa;
fs->regs.how[6] = REG_SAVED_OFFSET;
fs->regs.reg[6].loc.offset = (long)&sc->rbp - new_cfa;
fs->regs.how[8] = REG_SAVED_OFFSET;
fs->regs.reg[8].loc.offset = (long)&sc->r8 - new_cfa;
fs->regs.how[9] = REG_SAVED_OFFSET;
fs->regs.reg[9].loc.offset = (long)&sc->r9 - new_cfa;
fs->regs.how[10] = REG_SAVED_OFFSET;
fs->regs.reg[10].loc.offset = (long)&sc->r10 - new_cfa;
fs->regs.how[11] = REG_SAVED_OFFSET;
fs->regs.reg[11].loc.offset = (long)&sc->r11 - new_cfa;
fs->regs.how[12] = REG_SAVED_OFFSET;
fs->regs.reg[12].loc.offset = (long)&sc->r12 - new_cfa;
fs->regs.how[13] = REG_SAVED_OFFSET;
fs->regs.reg[13].loc.offset = (long)&sc->r13 - new_cfa;
fs->regs.how[14] = REG_SAVED_OFFSET;
fs->regs.reg[14].loc.offset = (long)&sc->r14 - new_cfa;
fs->regs.how[15] = REG_SAVED_OFFSET;
fs->regs.reg[15].loc.offset = (long)&sc->r15 - new_cfa;
fs->regs.how[16] = REG_SAVED_OFFSET;
fs->regs.reg[16].loc.offset = (long)&sc->rip - new_cfa;
fs->retaddr_column = 16;
fs->signal_frame = 1;
return _URC_NO_REASON;
}
#else /* ifdef __x86_64__ */
#define MD_FALLBACK_FRAME_STATE_FOR x86_fallback_frame_state
static _Unwind_Reason_Code
x86_fallback_frame_state (struct _Unwind_Context *context,
_Unwind_FrameState *fs)
{
unsigned char *pc = context->ra;
struct sigcontext *sc;
long new_cfa;
/* popl %eax ; movl $__NR_sigreturn,%eax ; int $0x80 */
if (*(unsigned short *)(pc+0) == 0xb858
&& *(unsigned int *)(pc+2) == 119
&& *(unsigned short *)(pc+6) == 0x80cd)
sc = context->cfa + 4;
/* movl $__NR_rt_sigreturn,%eax ; int $0x80 */
else if (*(unsigned char *)(pc+0) == 0xb8
&& *(unsigned int *)(pc+1) == 173
&& *(unsigned short *)(pc+5) == 0x80cd)
{
struct rt_sigframe {
int sig;
siginfo_t *pinfo;
void *puc;
siginfo_t info;
ucontext_t uc;
} *rt_ = context->cfa;
/* The void * cast is necessary to avoid an aliasing warning.
The aliasing warning is correct, but should not be a problem
because it does not alias anything. */
sc = (struct sigcontext *) (void *) &rt_->uc.uc_mcontext;
}
else
return _URC_END_OF_STACK;
new_cfa = sc->esp;
fs->regs.cfa_how = CFA_REG_OFFSET;
fs->regs.cfa_reg = 4;
fs->regs.cfa_offset = new_cfa - (long) context->cfa;
/* The SVR4 register numbering macros aren't usable in libgcc. */
fs->regs.how[0] = REG_SAVED_OFFSET;
fs->regs.reg[0].loc.offset = (long)&sc->eax - new_cfa;
fs->regs.how[3] = REG_SAVED_OFFSET;
fs->regs.reg[3].loc.offset = (long)&sc->ebx - new_cfa;
fs->regs.how[1] = REG_SAVED_OFFSET;
fs->regs.reg[1].loc.offset = (long)&sc->ecx - new_cfa;
fs->regs.how[2] = REG_SAVED_OFFSET;
fs->regs.reg[2].loc.offset = (long)&sc->edx - new_cfa;
fs->regs.how[6] = REG_SAVED_OFFSET;
fs->regs.reg[6].loc.offset = (long)&sc->esi - new_cfa;
fs->regs.how[7] = REG_SAVED_OFFSET;
fs->regs.reg[7].loc.offset = (long)&sc->edi - new_cfa;
fs->regs.how[5] = REG_SAVED_OFFSET;
fs->regs.reg[5].loc.offset = (long)&sc->ebp - new_cfa;
fs->regs.how[8] = REG_SAVED_OFFSET;
fs->regs.reg[8].loc.offset = (long)&sc->eip - new_cfa;
fs->retaddr_column = 8;
fs->signal_frame = 1;
return _URC_NO_REASON;
}
#define MD_FROB_UPDATE_CONTEXT x86_frob_update_context
/* Fix up for kernels that have vDSO, but don't have S flag in it. */
static void
x86_frob_update_context (struct _Unwind_Context *context,
_Unwind_FrameState *fs ATTRIBUTE_UNUSED)
{
unsigned char *pc = context->ra;
/* movl $__NR_rt_sigreturn,%eax ; {int $0x80 | syscall} */
if (*(unsigned char *)(pc+0) == 0xb8
&& *(unsigned int *)(pc+1) == 173
&& (*(unsigned short *)(pc+5) == 0x80cd
|| *(unsigned short *)(pc+5) == 0x050f))
_Unwind_SetSignalFrame (context, 1);
}
#endif /* ifdef __x86_64__ */
#endif /* ifdef inhibit_libc */
Reference in a new issue View git blame Copy permalink