/* Save current context and install the given one.
- Copyright (C) 2001 Free Software Foundation, Inc.
+ Copyright (C) 2001-2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@redhat.com>, 2001.
The GNU C Library is free software; you can redistribute it and/or
- modify it under the terms of the GNU Library General Public License as
- published by the Free Software Foundation; either version 2 of the
- License, or (at your option) any later version.
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- Library General Public License for more details.
+ Lesser General Public License for more details.
- You should have received a copy of the GNU Library General Public
- License along with the GNU C Library; see the file COPYING.LIB. If not,
- write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
- Boston, MA 02111-1307, USA. */
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
#include <sysdep.h>
+#include <asm/prctl.h>
#include "ucontext_i.h"
/* Load address of the context data structure we save in. */
movl 4(%esp), %eax
- /* Return value of swapcontext. EAX is the only register whose
- value is not preserved. */
- movl $0, oEAX(%eax)
-
- /* Save the 32-bit register values and the return address. */
- movl %ecx, oECX(%eax)
- movl %edx, oEDX(%eax)
+ /* Save the preserved register values and the return address. */
movl %edi, oEDI(%eax)
movl %esi, oESI(%eax)
movl %ebp, oEBP(%eax)
movl %ecx, oESP(%eax)
movl %ebx, oEBX(%eax)
- /* Save the FS and GS segment register. */
+ /* Save the FS segment register. */
xorl %edx, %edx
- xorl %ecx, %ecx
- movw %gs, %dx
- movw %fs, %cx
- movl %edx, oGS(%eax)
- movl %ecx, oFS(%eax)
+ movw %fs, %dx
+ movl %edx, oFS(%eax)
/* We have separate floating-point register content memory on the
stack. We use the __fpregs_mem block in the context. Set the
leal oSIGMASK(%ecx), %ecx
movl $SIG_SETMASK, %ebx
movl $__NR_sigprocmask, %eax
- int $0x80
+ ENTER_KERNEL
popl %ebx
cmpl $-4095, %eax /* Check %eax for error. */
jae SYSCALL_ERROR_LABEL /* Jump to error handler if error. */
movl oFPREGS(%eax), %ecx
fldenv (%ecx)
- /* Restore the FS and GS segment registers. */
- movl oGS(%eax), %edx
- movl oFS(%eax), %ecx
- movw %dx, %gs
- movw %cx, %fs
+ /* Restore the FS segment register. We don't touch the GS register
+ since it is used for threads. */
+ movl oFS(%eax), %edx
+ movw %dx, %fs
+
+#if SHSTK_ENABLED
+ /* Check if Shadow Stack is enabled. */
+ testl $X86_FEATURE_1_SHSTK, %gs:FEATURE_1_OFFSET
+ jz L(no_shstk)
+
+ xorl %eax, %eax
+ cmpl %gs:SSP_BASE_OFFSET, %eax
+ jnz L(shadow_stack_bound_recorded)
+
+ /* Get the base address and size of the default shadow stack
+ which must be the current shadow stack since nothing has
+ been recorded yet. */
+ sub $24, %esp
+ mov %esp, %ecx
+ movl $ARCH_CET_STATUS, %ebx
+ movl $__NR_arch_prctl, %eax
+ ENTER_KERNEL
+ testl %eax, %eax
+ jz L(continue_no_err)
+
+ /* This should never happen. */
+ hlt
+
+L(continue_no_err):
+ /* Record the base of the current shadow stack. */
+ movl 8(%esp), %eax
+ movl %eax, %gs:SSP_BASE_OFFSET
+ add $24, %esp
+
+L(shadow_stack_bound_recorded):
+ /* Load address of the context data structure we save in. */
+ movl 4(%esp), %eax
+
+ /* Load address of the context data structure we swap in */
+ movl 8(%esp), %edx
+
+ /* If we unwind the stack, we can't undo stack unwinding. Just
+ save the target shadow stack pointer as the current shadow
+ stack pointer. */
+ movl oSSP(%edx), %ecx
+ movl %ecx, oSSP(%eax)
+
+ /* Save the current shadow stack base in ucontext. */
+ movl %gs:SSP_BASE_OFFSET, %ecx
+ movl %ecx, (oSSP + 4)(%eax)
+
+ /* If the base of the target shadow stack is the same as the
+ base of the current shadow stack, we unwind the shadow
+ stack. Otherwise it is a stack switch and we look for a
+ restore token. */
+ movl oSSP(%edx), %esi
+ movl %esi, %edi
+
+ /* Get the base of the target shadow stack. */
+ movl (oSSP + 4)(%edx), %ecx
+ cmpl %gs:SSP_BASE_OFFSET, %ecx
+ je L(unwind_shadow_stack)
+
+ /* Align the saved original shadow stack pointer to the next
+ 8 byte aligned boundary. */
+ andl $-8, %esi
+
+L(find_restore_token_loop):
+ /* Look for a restore token. */
+ movl -8(%esi), %ebx
+ andl $-8, %ebx
+ cmpl %esi, %ebx
+ je L(restore_shadow_stack)
+
+ /* Try the next slot. */
+ subl $8, %esi
+ jmp L(find_restore_token_loop)
+
+L(restore_shadow_stack):
+ /* The target shadow stack will be restored. Save the current
+ shadow stack pointer. */
+ rdsspd %ecx
+ movl %ecx, oSSP(%eax)
+
+ /* Use the restore stoken to restore the target shadow stack. */
+ rstorssp -8(%esi)
+
+ /* Save the restore token on the old shadow stack. NB: This
+ restore token may be checked by setcontext or swapcontext
+ later. */
+ saveprevssp
+
+ /* Record the new shadow stack base that was switched to. */
+ movl (oSSP + 4)(%edx), %ebx
+ movl %ebx, %gs:SSP_BASE_OFFSET
+
+L(unwind_shadow_stack):
+ rdsspd %ebx
+ subl %edi, %ebx
+ je L(skip_unwind_shadow_stack)
+ negl %ebx
+ shrl $2, %ebx
+ movl $255, %esi
+L(loop):
+ cmpl %esi, %ebx
+ cmovb %ebx, %esi
+ incsspd %esi
+ subl %esi, %ebx
+ ja L(loop)
+
+L(skip_unwind_shadow_stack):
/* Load the new stack pointer. */
- movl oESP(%eax), %ecx
- /* Make room for 8 registers and the return address. We will load
- the values from the stack. */
- subl $36, %ecx
-
- /* Move the values of all the 32-bit registers (except ESP) on
- the stack. This happens in the form the 'popa' instruction
- expects it. Before this block put the address of the code
- to execute. */
- movl oEDI(%eax), %ebx
- movl oESI(%eax), %edx
- movl oEBP(%eax), %esi
- movl oEBX(%eax), %edi
- movl %ebx, (%ecx)
- movl %edx, 4(%ecx)
- movl %esi, 8(%ecx)
- movl %edi, 16(%ecx)
- movl oEDX(%eax), %ebx
- movl oECX(%eax), %edx
- movl oEAX(%eax), %esi
- movl oEIP(%eax), %edi
- movl %ebx, 20(%ecx)
- movl %edx, 24(%ecx)
- movl %esi, 28(%ecx)
- movl %edi, 32(%ecx)
-
- /* Set the new stack address. The stack points now to the block
- we put the register content in. */
- movl %ecx, %esp
- /* Restore the register content. */
- popa
- /* The following 'ret' will pop the addres of the code and jump
- to it. */
+ movl oESP(%edx), %esp
+
+ /* Load the values of all the preserved registers (except ESP). */
+ movl oEDI(%edx), %edi
+ movl oESI(%edx), %esi
+ movl oEBP(%edx), %ebp
+ movl oEBX(%edx), %ebx
+
+ /* Get the return address set with getcontext. */
+ movl oEIP(%edx), %ecx
+
+ /* Check if return address is valid for the case when setcontext
+ is invoked from L(exitcode) with linked context. */
+ rdsspd %eax
+ cmpl (%eax), %ecx
+ /* Clear EAX to indicate success. NB: Don't use xorl to keep
+ EFLAGS for jne. */
+ movl $0, %eax
+ jne L(jmp)
+ /* Return to the new context if return address valid. */
+ pushl %ecx
+ ret
+
+L(jmp):
+ /* Jump to the new context directly. */
+ jmp *%ecx
-L(pseudo_end):
+L(no_shstk):
+#endif
+
+ /* Fetch the address to return to. */
+ movl oEIP(%eax), %ecx
+
+ /* Load the new stack pointer. */
+ movl oESP(%eax), %esp
+
+ /* Push the return address on the new stack so we can return there. */
+ pushl %ecx
+
+ /* Load the values of all the preserved registers (except ESP). */
+ movl oEDI(%eax), %edi
+ movl oESI(%eax), %esi
+ movl oEBP(%eax), %ebp
+ movl oEBX(%eax), %ebx
+
+ /* All done, return 0 for success. */
+ xorl %eax, %eax
+
+ /* The following 'ret' will pop the address of the code and jump
+ to it. */
ret
PSEUDO_END(__swapcontext)
-weak_alias(__swapcontext, swapcontext)
+weak_alias (__swapcontext, swapcontext)
projects / thirdparty / glibc.git / blobdiff