diff options
Diffstat (limited to 'sysdeps/unix/sysv/linux/i386/makecontext.S')
| -rw-r--r-- | sysdeps/unix/sysv/linux/i386/makecontext.S | 123 |
1 files changed, 123 insertions, 0 deletions
diff --git a/sysdeps/unix/sysv/linux/i386/makecontext.S b/sysdeps/unix/sysv/linux/i386/makecontext.S index ad9ce5f977..91009675d1 100644 --- a/sysdeps/unix/sysv/linux/i386/makecontext.S +++ b/sysdeps/unix/sysv/linux/i386/makecontext.S @@ -18,6 +18,7 @@ <https://www.gnu.org/licenses/>. */ #include <sysdep.h> +#include <asm/prctl.h> #include "ucontext_i.h" @@ -68,6 +69,127 @@ ENTRY(__makecontext) jnz 1b 2: +#if SHSTK_ENABLED + /* Check if Shadow Stack is enabled. */ + testl $X86_FEATURE_1_SHSTK, %gs:FEATURE_1_OFFSET + jz L(skip_ssp) + + /* Reload the pointer to ucontext. */ + movl 4(%esp), %eax + + /* Shadow stack is enabled. We need to allocate a new shadow + stack. */ + subl oSS_SP(%eax), %edx + shrl $STACK_SIZE_TO_SHADOW_STACK_SIZE_SHIFT, %edx + + /* Align shadow stack size to 8 bytes. */ + addl $7, %edx + andl $-8, %edx + + /* Store shadow stack size in __ssp[2]. */ + movl %edx, (oSSP + 8)(%eax) + + /* Save ESI in the second scratch register slot. */ + movl %esi, oSCRATCH2(%eax) + /* Save EDI in the third scratch register slot. */ + movl %edi, oSCRATCH3(%eax) + + /* Save the pointer to ucontext. */ + movl %eax, %edi + + /* Get the original shadow stack pointer. */ + rdsspd %esi + + /* Align the saved original shadow stack pointer to the next + 8 byte aligned boundary. */ + andl $-8, %esi + + /* Load the top of the new stack into EDX. */ + movl oESP(%eax), %edx + + /* We need to terminate the FDE here because the unwinder looks + at ra-1 for unwind information. */ + cfi_endproc + + /* Swap the original stack pointer with the top of the new + stack. */ + xchgl %esp, %edx + + /* Add 4 bytes since CALL will push the 4-byte return address + onto stack. */ + addl $4, %esp + + /* Allocate the new shadow stack. Save EBX in the first scratch + register slot. */ + movl %ebx, oSCRATCH1(%eax) + + /* CET syscall takes 64-bit sizes. */ + subl $16, %esp + movl (oSSP + 8)(%eax), %ecx + movl %ecx, (%esp) + movl $0, 4(%esp) + movl %ecx, 8(%esp) + movl $0, 12(%esp) + movl %esp, %ecx + + movl $ARCH_CET_ALLOC_SHSTK, %ebx + movl $__NR_arch_prctl, %eax + ENTER_KERNEL + testl %eax, %eax + jne L(hlt) /* This should never happen. */ + + /* Copy the base address of the new shadow stack to __ssp[1]. */ + movl (%esp), %eax + movl %eax, (oSSP + 4)(%edi) + + addl $16, %esp + + /* Restore EBX from the first scratch register slot. */ + movl oSCRATCH1(%edi), %ebx + + /* Get the size of the new shadow stack. */ + movl (oSSP + 8)(%edi), %ecx + + /* Use the restore stoken to restore the new shadow stack. */ + rstorssp -8(%eax, %ecx) + + /* Save the restore token at the next 8 byte aligned boundary + on the original shadow stack. */ + saveprevssp + + /* Push the address of "jmp exitcode" onto the new stack as + well as the new shadow stack. */ + call 1f + jmp L(exitcode) +1: + + /* Get the new shadow stack pointer. */ + rdsspd %eax + + /* Use the restore stoken to restore the original shadow stack. */ + rstorssp -8(%esi) + + /* Save the restore token on the new shadow stack. */ + saveprevssp + + /* Store the new shadow stack pointer in __ssp[0]. */ + movl %eax, oSSP(%edi) + + /* Restore the original stack. */ + mov %edx, %esp + + cfi_startproc + + /* Restore ESI from the second scratch register slot. */ + movl oSCRATCH2(%edi), %esi + /* Restore EDI from the third scratch register slot. */ + movl oSCRATCH3(%edi), %edi + + ret + +L(skip_ssp): +#endif + /* If the function we call returns we must continue with the context which is given in the uc_link element. To do this set the return address for the function the user provides @@ -123,6 +245,7 @@ L(call_exit): call HIDDEN_JUMPTARGET(exit) /* The 'exit' call should never return. In case it does cause the process to terminate. */ +L(hlt): hlt cfi_startproc END(__makecontext) |