diff options
Diffstat (limited to 'sysdeps/unix/sysv/linux/i386/setcontext.S')
| -rw-r--r-- | sysdeps/unix/sysv/linux/i386/setcontext.S | 101 |
1 files changed, 3 insertions, 98 deletions
diff --git a/sysdeps/unix/sysv/linux/i386/setcontext.S b/sysdeps/unix/sysv/linux/i386/setcontext.S index 966fcbee1e..b6d827d11f 100644 --- a/sysdeps/unix/sysv/linux/i386/setcontext.S +++ b/sysdeps/unix/sysv/linux/i386/setcontext.S @@ -17,7 +17,6 @@ <https://www.gnu.org/licenses/>. */ #include <sysdep.h> -#include <asm/prctl.h> #include "ucontext_i.h" @@ -56,6 +55,9 @@ ENTRY(__setcontext) movl oFS(%eax), %ecx movw %cx, %fs + /* Fetch the address to return to. */ + movl oEIP(%eax), %ecx + /* Load the new stack pointer. */ cfi_def_cfa (eax, 0) cfi_offset (edi, oEDI) @@ -64,103 +66,6 @@ ENTRY(__setcontext) cfi_offset (ebx, oEBX) movl oESP(%eax), %esp -#if SHSTK_ENABLED - /* Check if Shadow Stack is enabled. */ - testl $X86_FEATURE_1_SHSTK, %gs:FEATURE_1_OFFSET - jz L(no_shstk) - - /* 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(%eax), %esi - movl %esi, %edi - - /* Get the base of the target shadow stack. */ - movl (oSSP + 4)(%eax), %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): - /* Pop return address from the shadow stack since setcontext - will not return. */ - movl $1, %ebx - incsspd %ebx - - /* 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)(%eax), %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 values of all the preserved registers (except ESP). */ - movl oEDI(%eax), %edi - movl oESI(%eax), %esi - movl oEBP(%eax), %ebp - movl oEBX(%eax), %ebx - - /* Get the return address set with getcontext. */ - movl oEIP(%eax), %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 - /* Push the return address on the new stack so we can return there. */ pushl %ecx |