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188 lines
4.8 KiB
ArmAsm
188 lines
4.8 KiB
ArmAsm
/* Install given 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(__setcontext)
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/* Load address of the context data structure. */
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movl 4(%esp), %eax
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/* Get the current signal mask. Note that we preserve EBX in case
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the system call fails and we return from the function with an
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error. */
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pushl %ebx
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cfi_adjust_cfa_offset (4)
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xorl %edx, %edx
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leal oSIGMASK(%eax), %ecx
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movl $SIG_SETMASK, %ebx
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cfi_rel_offset (ebx, 0)
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movl $__NR_sigprocmask, %eax
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ENTER_KERNEL
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popl %ebx
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cfi_adjust_cfa_offset (-4)
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cfi_restore (ebx)
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cmpl $-4095, %eax /* Check %eax for error. */
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jae SYSCALL_ERROR_LABEL /* Jump to error handler if error. */
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/* EAX was modified, reload it. */
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movl 4(%esp), %eax
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/* Restore the floating-point context. Not the registers, only the
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rest. */
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movl oFPREGS(%eax), %ecx
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fldenv (%ecx)
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/* Restore the FS segment register. We don't touch the GS register
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since it is used for threads. */
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movl oFS(%eax), %ecx
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movw %cx, %fs
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/* Load the new stack pointer. */
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cfi_def_cfa (eax, 0)
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cfi_offset (edi, oEDI)
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cfi_offset (esi, oESI)
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cfi_offset (ebp, oEBP)
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cfi_offset (ebx, oEBX)
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movl oESP(%eax), %esp
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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(no_shstk)
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/* If the base of the target shadow stack is the same as the
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base of the current shadow stack, we unwind the shadow
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stack. Otherwise it is a stack switch and we look for a
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restore token. */
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movl oSSP(%eax), %esi
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movl %esi, %edi
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/* Get the base of the target shadow stack. */
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movl (oSSP + 4)(%eax), %ecx
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cmpl %gs:SSP_BASE_OFFSET, %ecx
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je L(unwind_shadow_stack)
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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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L(find_restore_token_loop):
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/* Look for a restore token. */
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movl -8(%esi), %ebx
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andl $-8, %ebx
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cmpl %esi, %ebx
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je L(restore_shadow_stack)
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/* Try the next slot. */
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subl $8, %esi
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jmp L(find_restore_token_loop)
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L(restore_shadow_stack):
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/* Pop return address from the shadow stack since setcontext
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will not return. */
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movl $1, %ebx
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incsspd %ebx
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/* Use the restore stoken to restore the target shadow stack. */
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rstorssp -8(%esi)
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/* Save the restore token on the old shadow stack. NB: This
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restore token may be checked by setcontext or swapcontext
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later. */
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saveprevssp
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/* Record the new shadow stack base that was switched to. */
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movl (oSSP + 4)(%eax), %ebx
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movl %ebx, %gs:SSP_BASE_OFFSET
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L(unwind_shadow_stack):
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rdsspd %ebx
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subl %edi, %ebx
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je L(skip_unwind_shadow_stack)
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negl %ebx
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shrl $2, %ebx
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movl $255, %esi
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L(loop):
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cmpl %esi, %ebx
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cmovb %ebx, %esi
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incsspd %esi
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subl %esi, %ebx
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ja L(loop)
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L(skip_unwind_shadow_stack):
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/* Load the values of all the preserved registers (except ESP). */
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movl oEDI(%eax), %edi
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movl oESI(%eax), %esi
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movl oEBP(%eax), %ebp
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movl oEBX(%eax), %ebx
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/* Get the return address set with getcontext. */
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movl oEIP(%eax), %ecx
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/* Check if return address is valid for the case when setcontext
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is invoked from L(exitcode) with linked context. */
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rdsspd %eax
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cmpl (%eax), %ecx
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/* Clear EAX to indicate success. NB: Don't use xorl to keep
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EFLAGS for jne. */
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movl $0, %eax
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jne L(jmp)
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/* Return to the new context if return address valid. */
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pushl %ecx
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ret
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L(jmp):
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/* Jump to the new context directly. */
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jmp *%ecx
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L(no_shstk):
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#endif
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/* Fetch the address to return to. */
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movl oEIP(%eax), %ecx
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/* Push the return address on the new stack so we can return there. */
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pushl %ecx
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/* Load the values of all the preserved registers (except ESP). */
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movl oEDI(%eax), %edi
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movl oESI(%eax), %esi
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movl oEBP(%eax), %ebp
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movl oEBX(%eax), %ebx
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/* All done, return 0 for success. */
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xorl %eax, %eax
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/* End FDE here, we fall into another context. */
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cfi_endproc
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cfi_startproc
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/* The following 'ret' will pop the address of the code and jump
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to it. */
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ret
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PSEUDO_END(__setcontext)
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libc_hidden_def (__setcontext)
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weak_alias (__setcontext, setcontext)
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