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15c19147a8
To prepare for shadow stack support, restore the pointer into %rdx after syscall and use %rdx, instead of %rsi, to restore context. There is no functional change. Signed-off-by: H.J. Lu <hjl.tools@gmail.com> Reviewed-by: Carlos O'Donell <carlos@redhat.com> * sysdeps/unix/sysv/linux/x86_64/swapcontext.S (__swapcontext): Restore the pointer into %rdx, after syscall and use %rdx, instead of %rsi, to restore context.
123 lines
3.6 KiB
ArmAsm
123 lines
3.6 KiB
ArmAsm
/* Save current context and install the given one.
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Copyright (C) 2002-2018 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Andreas Jaeger <aj@suse.de>, 2002.
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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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<http://www.gnu.org/licenses/>. */
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#include <sysdep.h>
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#include "ucontext_i.h"
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/* int __swapcontext (ucontext_t *oucp, const ucontext_t *ucp);
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Saves the machine context in oucp such that when it is activated,
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it appears as if __swapcontextt() returned again, restores the
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machine context in ucp and thereby resumes execution in that
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context.
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This implementation is intended to be used for *synchronous* context
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switches only. Therefore, it does not have to save anything
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other than the PRESERVED state. */
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ENTRY(__swapcontext)
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/* Save the preserved registers, the registers used for passing args,
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and the return address. */
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movq %rbx, oRBX(%rdi)
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movq %rbp, oRBP(%rdi)
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movq %r12, oR12(%rdi)
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movq %r13, oR13(%rdi)
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movq %r14, oR14(%rdi)
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movq %r15, oR15(%rdi)
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movq %rdi, oRDI(%rdi)
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movq %rsi, oRSI(%rdi)
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movq %rdx, oRDX(%rdi)
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movq %rcx, oRCX(%rdi)
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movq %r8, oR8(%rdi)
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movq %r9, oR9(%rdi)
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movq (%rsp), %rcx
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movq %rcx, oRIP(%rdi)
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leaq 8(%rsp), %rcx /* Exclude the return address. */
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movq %rcx, oRSP(%rdi)
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/* We have separate floating-point register content memory on the
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stack. We use the __fpregs_mem block in the context. Set the
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links up correctly. */
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leaq oFPREGSMEM(%rdi), %rcx
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movq %rcx, oFPREGS(%rdi)
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/* Save the floating-point environment. */
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fnstenv (%rcx)
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stmxcsr oMXCSR(%rdi)
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/* The syscall destroys some registers, save them. */
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movq %rsi, %r12
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/* Save the current signal mask and install the new one with
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rt_sigprocmask (SIG_BLOCK, newset, oldset,_NSIG/8). */
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leaq oSIGMASK(%rdi), %rdx
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leaq oSIGMASK(%rsi), %rsi
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movl $SIG_SETMASK, %edi
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movl $_NSIG8,%r10d
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movl $__NR_rt_sigprocmask, %eax
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syscall
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cmpq $-4095, %rax /* Check %rax for error. */
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jae SYSCALL_ERROR_LABEL /* Jump to error handler if error. */
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/* Restore destroyed register into RDX. The choice is arbitrary,
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but leaving RDI and RSI available for use later can avoid
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shuffling values. */
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movq %r12, %rdx
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/* Restore the floating-point context. Not the registers, only the
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rest. */
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movq oFPREGS(%rdx), %rcx
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fldenv (%rcx)
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ldmxcsr oMXCSR(%rdx)
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/* Load the new stack pointer and the preserved registers. */
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movq oRSP(%rdx), %rsp
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movq oRBX(%rdx), %rbx
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movq oRBP(%rdx), %rbp
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movq oR12(%rdx), %r12
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movq oR13(%rdx), %r13
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movq oR14(%rdx), %r14
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movq oR15(%rdx), %r15
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/* The following ret should return to the address set with
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getcontext. Therefore push the address on the stack. */
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movq oRIP(%rdx), %rcx
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pushq %rcx
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/* Setup registers used for passing args. */
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movq oRDI(%rdx), %rdi
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movq oRSI(%rdx), %rsi
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movq oRCX(%rdx), %rcx
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movq oR8(%rdx), %r8
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movq oR9(%rdx), %r9
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/* Setup finally %rdx. */
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movq oRDX(%rdx), %rdx
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/* Clear rax to indicate success. */
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xorl %eax, %eax
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ret
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PSEUDO_END(__swapcontext)
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weak_alias (__swapcontext, swapcontext)
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