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253 lines
6.6 KiB
ArmAsm
253 lines
6.6 KiB
ArmAsm
/* Create new context.
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Copyright (C) 2001-2023 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <sysdep.h>
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#include <asm/prctl.h>
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#include "ucontext_i.h"
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ENTRY(__makecontext)
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movl 4(%esp), %eax
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/* Load the address of the function we are supposed to run. */
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movl 8(%esp), %ecx
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/* Compute the address of the stack. The information comes from
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to us_stack element. */
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movl oSS_SP(%eax), %edx
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movl %ecx, oEIP(%eax)
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addl oSS_SIZE(%eax), %edx
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/* Remember the number of parameters for the exit handler since
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it has to remove them. We store the number in the EBX register
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which the function we will call must preserve. */
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movl 12(%esp), %ecx
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movl %ecx, oEBX(%eax)
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/* Make room on the new stack for the parameters.
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Room for the arguments, return address (== L(exitcode)) and
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oLINK pointer is needed. One of the pointer sizes is subtracted
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after aligning the stack. */
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negl %ecx
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leal -4(%edx,%ecx,4), %edx
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negl %ecx
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/* Align the stack. */
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andl $0xfffffff0, %edx
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subl $4, %edx
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/* Store the future stack pointer. */
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movl %edx, oESP(%eax)
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/* Put the next context on the new stack (from the uc_link
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element). */
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movl oLINK(%eax), %eax
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movl %eax, 4(%edx,%ecx,4)
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/* Copy all the parameters. */
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jecxz 2f
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1: movl 12(%esp,%ecx,4), %eax
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movl %eax, (%edx,%ecx,4)
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decl %ecx
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jnz 1b
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2:
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#if SHSTK_ENABLED
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/* Check if Shadow Stack is enabled. */
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testl $X86_FEATURE_1_SHSTK, %gs:FEATURE_1_OFFSET
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jz L(skip_ssp)
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/* Reload the pointer to ucontext. */
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movl 4(%esp), %eax
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/* Shadow stack is enabled. We need to allocate a new shadow
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stack. */
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subl oSS_SP(%eax), %edx
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shrl $STACK_SIZE_TO_SHADOW_STACK_SIZE_SHIFT, %edx
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/* Align shadow stack size to 8 bytes. */
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addl $7, %edx
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andl $-8, %edx
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/* Store shadow stack size in __ssp[2]. */
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movl %edx, (oSSP + 8)(%eax)
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/* Save ESI in the second scratch register slot. */
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movl %esi, oSCRATCH2(%eax)
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/* Save EDI in the third scratch register slot. */
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movl %edi, oSCRATCH3(%eax)
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/* Save the pointer to ucontext. */
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movl %eax, %edi
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/* Get the original shadow stack pointer. */
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rdsspd %esi
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/* Align the saved original shadow stack pointer to the next
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8 byte aligned boundary. */
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andl $-8, %esi
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/* Load the top of the new stack into EDX. */
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movl oESP(%eax), %edx
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/* We need to terminate the FDE here because the unwinder looks
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at ra-1 for unwind information. */
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cfi_endproc
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/* Swap the original stack pointer with the top of the new
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stack. */
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xchgl %esp, %edx
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/* Add 4 bytes since CALL will push the 4-byte return address
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onto stack. */
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addl $4, %esp
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/* Allocate the new shadow stack. Save EBX in the first scratch
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register slot. */
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movl %ebx, oSCRATCH1(%eax)
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/* CET syscall takes 64-bit sizes. */
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subl $16, %esp
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movl (oSSP + 8)(%eax), %ecx
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movl %ecx, (%esp)
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movl $0, 4(%esp)
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movl %ecx, 8(%esp)
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movl $0, 12(%esp)
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movl %esp, %ecx
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movl $ARCH_CET_ALLOC_SHSTK, %ebx
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movl $__NR_arch_prctl, %eax
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ENTER_KERNEL
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testl %eax, %eax
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jne L(hlt) /* This should never happen. */
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/* Copy the base address of the new shadow stack to __ssp[1]. */
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movl (%esp), %eax
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movl %eax, (oSSP + 4)(%edi)
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addl $16, %esp
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/* Restore EBX from the first scratch register slot. */
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movl oSCRATCH1(%edi), %ebx
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/* Get the size of the new shadow stack. */
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movl (oSSP + 8)(%edi), %ecx
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/* Use the restore stoken to restore the new shadow stack. */
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rstorssp -8(%eax, %ecx)
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/* Save the restore token at the next 8 byte aligned boundary
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on the original shadow stack. */
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saveprevssp
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/* Push the address of "jmp exitcode" onto the new stack as
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well as the new shadow stack. */
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call 1f
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jmp L(exitcode)
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1:
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/* Get the new shadow stack pointer. */
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rdsspd %eax
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/* Use the restore stoken to restore the original shadow stack. */
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rstorssp -8(%esi)
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/* Save the restore token on the new shadow stack. */
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saveprevssp
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/* Store the new shadow stack pointer in __ssp[0]. */
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movl %eax, oSSP(%edi)
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/* Restore the original stack. */
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mov %edx, %esp
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cfi_startproc
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/* Restore ESI from the second scratch register slot. */
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movl oSCRATCH2(%edi), %esi
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/* Restore EDI from the third scratch register slot. */
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movl oSCRATCH3(%edi), %edi
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ret
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L(skip_ssp):
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#endif
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/* If the function we call returns we must continue with the
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context which is given in the uc_link element. To do this
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set the return address for the function the user provides
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to a little bit of helper code which does the magic (see
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below). */
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#ifdef PIC
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call 1f
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cfi_adjust_cfa_offset (4)
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1: popl %ecx
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cfi_adjust_cfa_offset (-4)
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addl $L(exitcode)-1b, %ecx
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movl %ecx, (%edx)
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#else
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movl $L(exitcode), (%edx)
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#endif
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/* We need to terminate the FDE here instead of after ret because
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the unwinder looks at ra-1 for unwind information. */
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cfi_endproc
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/* 'makecontext' returns no value. */
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ret
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/* This is the helper code which gets called if a function which
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is registered with 'makecontext' returns. In this case we
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have to install the context listed in the uc_link element of
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the context 'makecontext' manipulated at the time of the
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'makecontext' call. If the pointer is NULL the process must
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terminate. */
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L(exitcode):
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/* This removes the parameters passed to the function given to
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'makecontext' from the stack. EBX contains the number of
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parameters (see above). */
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leal (%esp,%ebx,4), %esp
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cmpl $0, (%esp) /* Check the next context. */
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je 2f /* If it is zero exit. */
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call HIDDEN_JUMPTARGET(__setcontext)
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/* If this returns (which can happen if the syscall fails) we'll
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exit the program with the return error value (-1). */
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jmp L(call_exit)
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2:
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/* Exit with status 0. */
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xorl %eax, %eax
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L(call_exit):
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/* Align the stack and pass the exit code (from %eax). */
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andl $0xfffffff0, %esp
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subl $12, %esp
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pushl %eax
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call HIDDEN_JUMPTARGET(exit)
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/* The 'exit' call should never return. In case it does cause
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the process to terminate. */
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L(hlt):
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hlt
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cfi_startproc
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END(__makecontext)
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weak_alias (__makecontext, makecontext)
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