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/* longjmp for i386.
Copyright (C) 1995-2024 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <sysdep.h>
#include <pointer_guard.h>
#include <jmpbuf-offsets.h>
#include <jmp_buf-ssp.h>
#include <asm-syntax.h>
#include <stap-probe.h>
/* Don't restore shadow stack register if
1. Shadow stack isn't enabled. Or
2. __longjmp is defined for __longjmp_cancel.
*/
#if !SHSTK_ENABLED || defined __longjmp
# undef SHADOW_STACK_POINTER_OFFSET
#endif
.text
ENTRY (__longjmp)
#ifdef PTR_DEMANGLE
movl 4(%esp), %eax /* User's jmp_buf in %eax. */
# ifdef SHADOW_STACK_POINTER_OFFSET
# if IS_IN (libc) && defined SHARED && defined FEATURE_1_OFFSET
/* Check if Shadow Stack is enabled. */
testl $X86_FEATURE_1_SHSTK, %gs:FEATURE_1_OFFSET
jz L(skip_ssp)
# else
xorl %edx, %edx
# endif
/* Check and adjust the Shadow-Stack-Pointer. */
rdsspd %edx
/* And compare it with the saved ssp value. */
subl SHADOW_STACK_POINTER_OFFSET(%eax), %edx
je L(skip_ssp)
/* Count the number of frames to adjust and adjust it
with incssp instruction. The instruction can adjust
the ssp by [0..255] value only thus use a loop if
the number of frames is bigger than 255. */
negl %edx
shrl $2, %edx
/* NB: We saved Shadow-Stack-Pointer of setjmp. Since we are
restoring Shadow-Stack-Pointer of setjmp's caller, we
need to unwind shadow stack by one more frame. */
addl $1, %edx
movl $255, %ebx
L(loop):
cmpl %ebx, %edx
cmovb %edx, %ebx
incsspd %ebx
subl %ebx, %edx
ja L(loop)
L(skip_ssp):
# endif
/* Save the return address now. */
movl (JB_PC*4)(%eax), %edx
/* Get the stack pointer. */
movl (JB_SP*4)(%eax), %ecx
PTR_DEMANGLE (%edx)
PTR_DEMANGLE (%ecx)
LIBC_PROBE (longjmp, 3, 4@%eax, -4@8(%esp), 4@%edx)
cfi_def_cfa(%eax, 0)
cfi_register(%eip, %edx)
cfi_register(%esp, %ecx)
cfi_offset(%ebx, JB_BX*4)
cfi_offset(%esi, JB_SI*4)
cfi_offset(%edi, JB_DI*4)
cfi_offset(%ebp, JB_BP*4)
/* Restore registers. */
movl (JB_BX*4)(%eax), %ebx
movl (JB_SI*4)(%eax), %esi
movl (JB_DI*4)(%eax), %edi
movl (JB_BP*4)(%eax), %ebp
cfi_restore(%ebx)
cfi_restore(%esi)
cfi_restore(%edi)
cfi_restore(%ebp)
LIBC_PROBE (longjmp_target, 3, 4@%eax, -4@8(%esp), 4@%edx)
movl 8(%esp), %eax /* Second argument is return value. */
movl %ecx, %esp
#else
movl 4(%esp), %ecx /* User's jmp_buf in %ecx. */
movl 8(%esp), %eax /* Second argument is return value. */
# ifdef SHADOW_STACK_POINTER_OFFSET
# if IS_IN (libc) && defined SHARED
/* Check if Shadow Stack is enabled. */
testl $X86_FEATURE_1_SHSTK, %gs:FEATURE_1_OFFSET
jz L(skip_ssp)
# endif
/* Check and adjust the Shadow-Stack-Pointer. */
xorl %edx, %edx
/* Get the current ssp. */
rdsspd %edx
/* And compare it with the saved ssp value. */
subl SHADOW_STACK_POINTER_OFFSET(%ecx), %edx
je L(skip_ssp)
/* Count the number of frames to adjust and adjust it
with incssp instruction. The instruction can adjust
the ssp by [0..255] value only thus use a loop if
the number of frames is bigger than 255. */
negl %edx
shrl $2, %edx
/* NB: We saved Shadow-Stack-Pointer of setjmp. Since we are
restoring Shadow-Stack-Pointer of setjmp's caller, we
need to unwind shadow stack by one more frame. */
addl $1, %edx
movl $255, %ebx
L(loop):
cmpl %ebx, %edx
cmovb %edx, %ebx
incsspd %ebx
subl %ebx, %edx
ja L(loop)
L(skip_ssp):
# endif
/* Save the return address now. */
movl (JB_PC*4)(%ecx), %edx
LIBC_PROBE (longjmp, 3, 4@%ecx, -4@%eax, 4@%edx)
/* Restore registers. */
movl (JB_BX*4)(%ecx), %ebx
movl (JB_SI*4)(%ecx), %esi
movl (JB_DI*4)(%ecx), %edi
movl (JB_BP*4)(%ecx), %ebp
movl (JB_SP*4)(%ecx), %esp
LIBC_PROBE (longjmp_target, 3, 4@%ecx, -4@%ecx, 4@%edx)
#endif
/* Jump to saved PC. */
jmp *%edx
END (__longjmp)
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