2001-04-07 20:09:42 +00:00
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/* Save current context and install the given one.
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2021-01-02 19:32:25 +00:00
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Copyright (C) 2001-2021 Free Software Foundation, Inc.
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2001-04-07 20:09:42 +00:00
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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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2001-07-06 04:58:11 +00:00
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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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2001-04-07 20:09:42 +00:00
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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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2001-07-06 04:58:11 +00:00
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Lesser General Public License for more details.
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2001-04-07 20:09:42 +00:00
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2001-07-06 04:58:11 +00:00
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You should have received a copy of the GNU Lesser General Public
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2012-02-09 23:18:22 +00:00
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License along with the GNU C Library; if not, see
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Prefer https to http for gnu.org and fsf.org URLs
Also, change sources.redhat.com to sourceware.org.
This patch was automatically generated by running the following shell
script, which uses GNU sed, and which avoids modifying files imported
from upstream:
sed -ri '
s,(http|ftp)(://(.*\.)?(gnu|fsf|sourceware)\.org($|[^.]|\.[^a-z])),https\2,g
s,(http|ftp)(://(.*\.)?)sources\.redhat\.com($|[^.]|\.[^a-z]),https\2sourceware.org\4,g
' \
$(find $(git ls-files) -prune -type f \
! -name '*.po' \
! -name 'ChangeLog*' \
! -path COPYING ! -path COPYING.LIB \
! -path manual/fdl-1.3.texi ! -path manual/lgpl-2.1.texi \
! -path manual/texinfo.tex ! -path scripts/config.guess \
! -path scripts/config.sub ! -path scripts/install-sh \
! -path scripts/mkinstalldirs ! -path scripts/move-if-change \
! -path INSTALL ! -path locale/programs/charmap-kw.h \
! -path po/libc.pot ! -path sysdeps/gnu/errlist.c \
! '(' -name configure \
-execdir test -f configure.ac -o -f configure.in ';' ')' \
! '(' -name preconfigure \
-execdir test -f preconfigure.ac ';' ')' \
-print)
and then by running 'make dist-prepare' to regenerate files built
from the altered files, and then executing the following to cleanup:
chmod a+x sysdeps/unix/sysv/linux/riscv/configure
# Omit irrelevant whitespace and comment-only changes,
# perhaps from a slightly-different Autoconf version.
git checkout -f \
sysdeps/csky/configure \
sysdeps/hppa/configure \
sysdeps/riscv/configure \
sysdeps/unix/sysv/linux/csky/configure
# Omit changes that caused a pre-commit check to fail like this:
# remote: *** error: sysdeps/powerpc/powerpc64/ppc-mcount.S: trailing lines
git checkout -f \
sysdeps/powerpc/powerpc64/ppc-mcount.S \
sysdeps/unix/sysv/linux/s390/s390-64/syscall.S
# Omit change that caused a pre-commit check to fail like this:
# remote: *** error: sysdeps/sparc/sparc64/multiarch/memcpy-ultra3.S: last line does not end in newline
git checkout -f sysdeps/sparc/sparc64/multiarch/memcpy-ultra3.S
2019-09-07 05:40:42 +00:00
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<https://www.gnu.org/licenses/>. */
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2001-04-07 20:09:42 +00:00
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#include <sysdep.h>
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i386: Enable CET support in ucontext functions
1. getcontext and swapcontext are updated to save the caller's shadow
stack pointer and return address.
2. setcontext and swapcontext are updated to restore shadow stack and
jump to new context directly.
3. makecontext is updated to allocate a new shadow stack and set the
caller's return address to the helper code, L(exitcode).
4. Since we no longer save and restore EAX, ECX and EDX in getcontext,
setcontext and swapcontext, we can use them as scratch register slots
to enable CET in ucontext functions.
Since makecontext allocates a new shadow stack when making a new
context and kernel allocates a new shadow stack for clone/fork/vfork
syscalls, we track the current shadow stack base. In setcontext and
swapcontext, if the target shadow stack base is the same as the current
shadow stack base, we unwind the shadow stack. Otherwise it is a stack
switch and we look for a restore token.
We enable shadow stack at run-time only if program and all used shared
objects, including dlopened ones, are shadow stack enabled, which means
that they must be compiled with GCC 8 or above and glibc 2.28 or above.
We need to save and restore shadow stack only if shadow stack is enabled.
When caller of getcontext, setcontext, swapcontext and makecontext is
compiled with smaller ucontext_t, shadow stack won't be enabled at
run-time. We check if shadow stack is enabled before accessing the
extended field in ucontext_t.
Tested on i386 CET/non-CET machines.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2020-02-14 22:45:34 +00:00
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#include <asm/prctl.h>
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2001-04-07 20:09:42 +00:00
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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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2020-02-01 13:44:55 +00:00
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/* Save the preserved register values and the return address. */
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2001-04-07 20:09:42 +00:00
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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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2001-07-31 20:57:24 +00:00
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/* Save the FS segment register. */
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2001-04-07 20:09:42 +00:00
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xorl %edx, %edx
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2001-07-31 20:57:24 +00:00
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movw %fs, %dx
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movl %edx, oFS(%eax)
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2001-04-07 20:09:42 +00:00
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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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2002-12-20 07:12:24 +00:00
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ENTER_KERNEL
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2001-04-07 20:09:42 +00:00
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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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2003-04-06 20:59:45 +00:00
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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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2001-07-31 20:57:24 +00:00
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movl oFS(%eax), %edx
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movw %dx, %fs
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2001-04-07 20:09:42 +00:00
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i386: Enable CET support in ucontext functions
1. getcontext and swapcontext are updated to save the caller's shadow
stack pointer and return address.
2. setcontext and swapcontext are updated to restore shadow stack and
jump to new context directly.
3. makecontext is updated to allocate a new shadow stack and set the
caller's return address to the helper code, L(exitcode).
4. Since we no longer save and restore EAX, ECX and EDX in getcontext,
setcontext and swapcontext, we can use them as scratch register slots
to enable CET in ucontext functions.
Since makecontext allocates a new shadow stack when making a new
context and kernel allocates a new shadow stack for clone/fork/vfork
syscalls, we track the current shadow stack base. In setcontext and
swapcontext, if the target shadow stack base is the same as the current
shadow stack base, we unwind the shadow stack. Otherwise it is a stack
switch and we look for a restore token.
We enable shadow stack at run-time only if program and all used shared
objects, including dlopened ones, are shadow stack enabled, which means
that they must be compiled with GCC 8 or above and glibc 2.28 or above.
We need to save and restore shadow stack only if shadow stack is enabled.
When caller of getcontext, setcontext, swapcontext and makecontext is
compiled with smaller ucontext_t, shadow stack won't be enabled at
run-time. We check if shadow stack is enabled before accessing the
extended field in ucontext_t.
Tested on i386 CET/non-CET machines.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2020-02-14 22:45:34 +00:00
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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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2003-04-06 20:59:45 +00:00
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/* Fetch the address to return to. */
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movl oEIP(%eax), %ecx
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2001-04-07 20:09:42 +00:00
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/* Load the new stack pointer. */
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2003-04-06 20:59:45 +00:00
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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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2020-02-01 13:44:55 +00:00
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/* Load the values of all the preserved registers (except ESP). */
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2003-04-06 20:59:45 +00:00
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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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2020-02-01 13:44:55 +00:00
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/* All done, return 0 for success. */
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xorl %eax, %eax
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2003-04-06 20:59:45 +00:00
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/* The following 'ret' will pop the address of the code and jump
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2001-04-07 20:09:42 +00:00
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to it. */
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ret
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PSEUDO_END(__swapcontext)
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2005-05-26 14:30:51 +00:00
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|
weak_alias (__swapcontext, swapcontext)
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