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30891f35fa
We stopped adding "Contributed by" or similar lines in sources in 2012 in favour of git logs and keeping the Contributors section of the glibc manual up to date. Removing these lines makes the license header a bit more consistent across files and also removes the possibility of error in attribution when license blocks or files are copied across since the contributed-by lines don't actually reflect reality in those cases. Move all "Contributed by" and similar lines (Written by, Test by, etc.) into a new file CONTRIBUTED-BY to retain record of these contributions. These contributors are also mentioned in manual/contrib.texi, so we just maintain this additional record as a courtesy to the earlier developers. The following scripts were used to filter a list of files to edit in place and to clean up the CONTRIBUTED-BY file respectively. These were not added to the glibc sources because they're not expected to be of any use in future given that this is a one time task: https://gist.github.com/siddhesh/b5ecac94eabfd72ed2916d6d8157e7dc https://gist.github.com/siddhesh/15ea1f5e435ace9774f485030695ee02 Reviewed-by: Carlos O'Donell <carlos@redhat.com>
251 lines
6.6 KiB
ArmAsm
251 lines
6.6 KiB
ArmAsm
/* Save current context and install the given one.
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Copyright (C) 2002-2021 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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/* 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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movq %rdi, %r9
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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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#if SHSTK_ENABLED
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/* Check if shadow stack is enabled. */
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testl $X86_FEATURE_1_SHSTK, %fs:FEATURE_1_OFFSET
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jz L(no_shstk)
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xorl %eax, %eax
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cmpq %fs:SSP_BASE_OFFSET, %rax
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jnz L(shadow_stack_bound_recorded)
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/* Get the base address and size of the default shadow stack
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which must be the current shadow stack since nothing has
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been recorded yet. */
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sub $24, %RSP_LP
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mov %RSP_LP, %RSI_LP
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movl $ARCH_CET_STATUS, %edi
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movl $__NR_arch_prctl, %eax
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syscall
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testq %rax, %rax
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jz L(continue_no_err)
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/* This should never happen. */
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hlt
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L(continue_no_err):
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/* Record the base of the current shadow stack. */
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movq 8(%rsp), %rax
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movq %rax, %fs:SSP_BASE_OFFSET
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add $24, %RSP_LP
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L(shadow_stack_bound_recorded):
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/* If we unwind the stack, we can't undo stack unwinding. Just
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save the target shadow stack pointer as the current shadow
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stack pointer. */
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movq oSSP(%rdx), %rcx
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movq %rcx, oSSP(%r9)
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/* Save the base of the current shadow stack. */
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movq %fs:SSP_BASE_OFFSET, %rax
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movq %rax, (oSSP + 8)(%r9)
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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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movq oSSP(%rdx), %rsi
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movq %rsi, %rdi
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/* Get the base of the target shadow stack. */
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movq (oSSP + 8)(%rdx), %rcx
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cmpq %fs:SSP_BASE_OFFSET, %rcx
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je L(unwind_shadow_stack)
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L(find_restore_token_loop):
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/* Look for a restore token. */
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movq -8(%rsi), %rax
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andq $-8, %rax
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cmpq %rsi, %rax
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je L(restore_shadow_stack)
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/* Try the next slot. */
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subq $8, %rsi
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jmp L(find_restore_token_loop)
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L(restore_shadow_stack):
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/* The target shadow stack will be restored. Save the current
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shadow stack pointer. */
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rdsspq %rcx
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movq %rcx, oSSP(%r9)
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/* Restore the target shadow stack. */
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rstorssp -8(%rsi)
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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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movq (oSSP + 8)(%rdx), %rax
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movq %rax, %fs:SSP_BASE_OFFSET
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L(unwind_shadow_stack):
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rdsspq %rcx
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subq %rdi, %rcx
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je L(skip_unwind_shadow_stack)
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negq %rcx
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shrq $3, %rcx
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movl $255, %esi
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L(loop):
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cmpq %rsi, %rcx
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cmovb %rcx, %rsi
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incsspq %rsi
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subq %rsi, %rcx
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ja L(loop)
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L(skip_unwind_shadow_stack):
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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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/* Get the return address set with getcontext. */
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movq oRIP(%rdx), %r10
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/* Setup finally %rdx. */
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movq oRDX(%rdx), %rdx
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/* Check if return address is valid for the case when setcontext
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is invoked from __start_context with linked context. */
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rdsspq %rax
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cmpq (%rax), %r10
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/* Clear rax 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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pushq %r10
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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 *%r10
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L(no_shstk):
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#endif
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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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