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/* DWARF2 EH unwinding support for GNU Hurd: x86.
Copyright (C) 2020-2022 Free Software Foundation, Inc.
Contributed by Samuel Thibault <samuel.thibault@gnu.org>
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/>. */
/* Do code reading to identify a signal frame, and set the frame
state data appropriately. See unwind-dw2.c for the structs. */
#ifndef inhibit_libc
#include <signal.h>
#define MD_FALLBACK_FRAME_STATE_FOR x86_gnu_fallback_frame_state
static _Unwind_Reason_Code
x86_gnu_fallback_frame_state
(struct _Unwind_Context *context, _Unwind_FrameState *fs)
{
struct handler_args {
int signo;
union
{
struct
{
long int sigcode;
struct sigcontext *scp;
} legacy;
struct
{
siginfo_t *siginfop;
ucontext_t *uctxp;
} posix;
};
} *handler_args;
long int sigcode;
unsigned long usp;
/*
* i386 sigtramp frame we are looking for follows.
* (see glibc/sysdeps/mach/hurd/i386/trampoline.c assembly)
*
* rpc_wait_trampoline:
* 0: b8 e7 ff ff ff mov $-25,%eax mach_msg_trap
* 5: 9a 00 00 00 00 07 00 lcall $7,$0
* 12: 89 01 movl %eax, (%ecx)
* 14: 89 dc movl %ebx, %esp switch to signal stack
*
* trampoline:
* 16: ff d2 call *%edx call the handler function
* RA HERE
* 18: 83 c4 0c addl $12, %esp pop its args
* 21: c3 ret return to sigreturn
*
* firewall:
* 22: f4 hlt
*/
if (!( *(unsigned int *)(context->ra ) == 0xc30cc483
&& *(unsigned char *)(context->ra + 4) == 0xf4
&& *(unsigned int *)(context->ra - 4) == 0xd2ffdc89
&& *(unsigned int *)(context->ra - 8) == 0x01890007
&& *(unsigned int *)(context->ra - 12) == 0x00000000
&& *(unsigned int *)(context->ra - 16) == 0x9affffff
&& *(unsigned short *)(context->ra - 18) == 0xe7b8))
return _URC_END_OF_STACK;
handler_args = context->cfa;
sigcode = handler_args->legacy.sigcode;
if (sigcode >= -16 && sigcode < 4096)
{
/* This cannot be a SIGINFO pointer, assume legacy. */
struct sigcontext *scp = handler_args->legacy.scp;
usp = scp->sc_uesp;
fs->regs.reg[0].loc.offset = (unsigned long)&scp->sc_eax - usp;
fs->regs.reg[1].loc.offset = (unsigned long)&scp->sc_ecx - usp;
fs->regs.reg[2].loc.offset = (unsigned long)&scp->sc_edx - usp;
fs->regs.reg[3].loc.offset = (unsigned long)&scp->sc_ebx - usp;
fs->regs.reg[5].loc.offset = (unsigned long)&scp->sc_ebp - usp;
fs->regs.reg[6].loc.offset = (unsigned long)&scp->sc_esi - usp;
fs->regs.reg[7].loc.offset = (unsigned long)&scp->sc_edi - usp;
fs->regs.reg[8].loc.offset = (unsigned long)&scp->sc_eip - usp;
}
else
{
/* This is not a valid sigcode, assume SIGINFO. */
ucontext_t *uctxp = handler_args->posix.uctxp;
gregset_t *gregset = &uctxp->uc_mcontext.gregs;
usp = (*gregset)[REG_UESP];
fs->regs.reg[0].loc.offset = (unsigned long)&(*gregset)[REG_EAX] - usp;
fs->regs.reg[1].loc.offset = (unsigned long)&(*gregset)[REG_ECX] - usp;
fs->regs.reg[2].loc.offset = (unsigned long)&(*gregset)[REG_EDX] - usp;
fs->regs.reg[3].loc.offset = (unsigned long)&(*gregset)[REG_EBX] - usp;
fs->regs.reg[5].loc.offset = (unsigned long)&(*gregset)[REG_EBP] - usp;
fs->regs.reg[6].loc.offset = (unsigned long)&(*gregset)[REG_ESI] - usp;
fs->regs.reg[7].loc.offset = (unsigned long)&(*gregset)[REG_EDI] - usp;
fs->regs.reg[8].loc.offset = (unsigned long)&(*gregset)[REG_EIP] - usp;
}
fs->regs.cfa_how = CFA_REG_OFFSET;
fs->regs.cfa_reg = 4;
fs->regs.cfa_offset = usp - (unsigned long) context->cfa;
fs->regs.reg[0].how = REG_SAVED_OFFSET;
fs->regs.reg[1].how = REG_SAVED_OFFSET;
fs->regs.reg[2].how = REG_SAVED_OFFSET;
fs->regs.reg[3].how = REG_SAVED_OFFSET;
fs->regs.reg[5].how = REG_SAVED_OFFSET;
fs->regs.reg[6].how = REG_SAVED_OFFSET;
fs->regs.reg[7].how = REG_SAVED_OFFSET;
fs->regs.reg[8].how = REG_SAVED_OFFSET;
fs->retaddr_column = 8;
fs->signal_frame = 1;
return _URC_NO_REASON;
}
#endif /* ifndef inhibit_libc */
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