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/* Save current context.
Copyright (C) 2001-2022 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 <asm/prctl.h>
#include "ucontext_i.h"
ENTRY(__getcontext)
/* Load address of the context data structure. */
movl 4(%esp), %eax
/* Return value of getcontext. EAX is the only register whose
value is not preserved. */
movl $0, oEAX(%eax)
/* Save the 32-bit register values and the return address. */
movl %ecx, oECX(%eax)
movl %edx, oEDX(%eax)
movl %edi, oEDI(%eax)
movl %esi, oESI(%eax)
movl %ebp, oEBP(%eax)
movl (%esp), %ecx
movl %ecx, oEIP(%eax)
leal 4(%esp), %ecx /* Exclude the return address. */
movl %ecx, oESP(%eax)
movl %ebx, oEBX(%eax)
/* Save the FS segment register. We don't touch the GS register
since it is used for threads. */
xorl %edx, %edx
movw %fs, %dx
movl %edx, oFS(%eax)
#if SHSTK_ENABLED
/* Check if shadow stack is enabled. */
testl $X86_FEATURE_1_SHSTK, %gs:FEATURE_1_OFFSET
jz L(no_shstk)
/* Save EAX in EDX. */
movl %eax, %edx
xorl %eax, %eax
cmpl %gs:SSP_BASE_OFFSET, %eax
jnz L(shadow_stack_bound_recorded)
/* Save EBX in the first scratch register slot. */
movl %ebx, oSCRATCH1(%edx)
/* Get the base address and size of the default shadow stack
which must be the current shadow stack since nothing has
been recorded yet. */
sub $24, %esp
mov %esp, %ecx
movl $ARCH_CET_STATUS, %ebx
movl $__NR_arch_prctl, %eax
ENTER_KERNEL
testl %eax, %eax
jz L(continue_no_err)
/* This should never happen. */
hlt
L(continue_no_err):
/* Restore EBX from the first scratch register slot. */
movl oSCRATCH1(%edx), %ebx
/* Record the base of the current shadow stack. */
movl 8(%esp), %eax
movl %eax, %gs:SSP_BASE_OFFSET
add $24, %esp
L(shadow_stack_bound_recorded):
/* Load address of the context data structure. */
movl 4(%esp), %eax
/* Get the current shadow stack pointer. */
rdsspd %edx
/* NB: Save the caller's shadow stack so that we can jump back
to the caller directly. */
addl $4, %edx
movl %edx, oSSP(%eax)
/* Save the current shadow stack base in ucontext. */
movl %gs:SSP_BASE_OFFSET, %edx
movl %edx, (oSSP + 4)(%eax)
L(no_shstk):
#endif
/* We have separate floating-point register content memory on the
stack. We use the __fpregs_mem block in the context. Set the
links up correctly. */
leal oFPREGSMEM(%eax), %ecx
movl %ecx, oFPREGS(%eax)
/* Save the floating-point context. */
fnstenv (%ecx)
/* And load it right back since the processor changes the mask.
Intel thought this opcode to be used in interrupt handlers which
would block all exceptions. */
fldenv (%ecx)
/* Save the current signal mask. */
pushl %ebx
cfi_adjust_cfa_offset (4)
cfi_rel_offset (ebx, 0)
leal oSIGMASK(%eax), %edx
xorl %ecx, %ecx
movl $SIG_BLOCK, %ebx
movl $__NR_sigprocmask, %eax
ENTER_KERNEL
popl %ebx
cfi_adjust_cfa_offset (-4)
cfi_restore (ebx)
cmpl $-4095, %eax /* Check %eax for error. */
jae SYSCALL_ERROR_LABEL /* Jump to error handler if error. */
/* All done, return 0 for success. */
xorl %eax, %eax
ret
PSEUDO_END(__getcontext)
weak_alias (__getcontext, getcontext)
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