diff options
Diffstat (limited to 'sysdeps/unix/sysv/linux/i386/swapcontext.S')
| -rw-r--r-- | sysdeps/unix/sysv/linux/i386/swapcontext.S | 139 |
1 files changed, 0 insertions, 139 deletions
diff --git a/sysdeps/unix/sysv/linux/i386/swapcontext.S b/sysdeps/unix/sysv/linux/i386/swapcontext.S index b8367f025e..bb736ae7d2 100644 --- a/sysdeps/unix/sysv/linux/i386/swapcontext.S +++ b/sysdeps/unix/sysv/linux/i386/swapcontext.S @@ -17,7 +17,6 @@ <https://www.gnu.org/licenses/>. */ #include <sysdep.h> -#include <asm/prctl.h> #include "ucontext_i.h" @@ -76,144 +75,6 @@ ENTRY(__swapcontext) 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(%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(no_shstk): -#endif - /* Fetch the address to return to. */ movl oEIP(%eax), %ecx |