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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>
241 lines
6.2 KiB
ArmAsm
241 lines
6.2 KiB
ArmAsm
/* Save current context and install the given one.
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Copyright (C) 2001-2021 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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ENTRY(__swapcontext)
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/* Load address of the context data structure we save in. */
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movl 4(%esp), %eax
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/* Save the preserved register values and the return address. */
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movl %edi, oEDI(%eax)
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movl %esi, oESI(%eax)
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movl %ebp, oEBP(%eax)
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movl (%esp), %ecx
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movl %ecx, oEIP(%eax)
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leal 4(%esp), %ecx
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movl %ecx, oESP(%eax)
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movl %ebx, oEBX(%eax)
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/* Save the FS segment register. */
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xorl %edx, %edx
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movw %fs, %dx
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movl %edx, oFS(%eax)
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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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leal oFPREGSMEM(%eax), %ecx
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movl %ecx, oFPREGS(%eax)
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/* Save the floating-point context. */
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fnstenv (%ecx)
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/* Load address of the context data structure we have to load. */
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movl 8(%esp), %ecx
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/* Save the current signal mask and install the new one. */
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pushl %ebx
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leal oSIGMASK(%eax), %edx
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leal oSIGMASK(%ecx), %ecx
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movl $SIG_SETMASK, %ebx
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movl $__NR_sigprocmask, %eax
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ENTER_KERNEL
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popl %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 8(%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), %edx
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movw %dx, %fs
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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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xorl %eax, %eax
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cmpl %gs:SSP_BASE_OFFSET, %eax
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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, %esp
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mov %esp, %ecx
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movl $ARCH_CET_STATUS, %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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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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movl 8(%esp), %eax
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movl %eax, %gs:SSP_BASE_OFFSET
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add $24, %esp
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L(shadow_stack_bound_recorded):
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/* Load address of the context data structure we save in. */
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movl 4(%esp), %eax
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/* Load address of the context data structure we swap in */
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movl 8(%esp), %edx
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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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movl oSSP(%edx), %ecx
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movl %ecx, oSSP(%eax)
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/* Save the current shadow stack base in ucontext. */
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movl %gs:SSP_BASE_OFFSET, %ecx
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movl %ecx, (oSSP + 4)(%eax)
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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(%edx), %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)(%edx), %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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/* The target shadow stack will be restored. Save the current
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shadow stack pointer. */
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rdsspd %ecx
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movl %ecx, oSSP(%eax)
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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)(%edx), %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 new stack pointer. */
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movl oESP(%edx), %esp
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/* Load the values of all the preserved registers (except ESP). */
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movl oEDI(%edx), %edi
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movl oESI(%edx), %esi
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movl oEBP(%edx), %ebp
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movl oEBX(%edx), %ebx
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/* Get the return address set with getcontext. */
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movl oEIP(%edx), %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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/* Load the new stack pointer. */
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movl oESP(%eax), %esp
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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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/* 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(__swapcontext)
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weak_alias (__swapcontext, swapcontext)
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