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[thirdparty/glibc.git] / sysdeps / i386 / __longjmp.S

diff --git a/sysdeps/i386/__longjmp.S b/sysdeps/i386/__longjmp.S
index 36c692209ecaad13c5dc6640c86d94df05cbcb6f..ff910f10bc46dc6f255e85a595dde69709fd5841 100644 (file)
--- a/sysdeps/i386/__longjmp.S
+++ b/sysdeps/i386/__longjmp.S
@@ -1,5 +1,5 @@
 /* longjmp for i386.
-   Copyright (C) 1995-2016 Free Software Foundation, Inc.
+   Copyright (C) 1995-2019 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
 
    The GNU C Library is free software; you can redistribute it and/or
@@ -14,18 +14,59 @@
 
    You should have received a copy of the GNU Lesser General Public
    License along with the GNU C Library; if not, see
-   <http://www.gnu.org/licenses/>.  */
+   <https://www.gnu.org/licenses/>.  */
 
 #include <sysdep.h>
 #include <jmpbuf-offsets.h>
+#include <jmp_buf-ssp.h>
 #include <asm-syntax.h>
 #include <stap-probe.h>
 
+/* Don't restore shadow stack register if
+   1. Shadow stack isn't enabled.  Or
+   2. __longjmp is defined for __longjmp_cancel.
+ */
+#if !SHSTK_ENABLED || defined __longjmp
+# undef SHADOW_STACK_POINTER_OFFSET
+#endif
+
        .text
 ENTRY (__longjmp)
 #ifdef PTR_DEMANGLE
        movl 4(%esp), %eax      /* User's jmp_buf in %eax.  */
 
+# ifdef SHADOW_STACK_POINTER_OFFSET
+#  if IS_IN (libc) && defined SHARED && defined FEATURE_1_OFFSET
+       /* Check if Shadow Stack is enabled.  */
+       testl $X86_FEATURE_1_SHSTK, %gs:FEATURE_1_OFFSET
+       jz L(skip_ssp)
+#  else
+       xorl %edx, %edx
+#  endif
+       /* Check and adjust the Shadow-Stack-Pointer.  */
+       rdsspd %edx
+       /* And compare it with the saved ssp value.  */
+       subl SHADOW_STACK_POINTER_OFFSET(%eax), %edx
+       je L(skip_ssp)
+       /* Count the number of frames to adjust and adjust it
+          with incssp instruction.  The instruction can adjust
+          the ssp by [0..255] value only thus use a loop if
+          the number of frames is bigger than 255.  */
+       negl %edx
+       shrl $2, %edx
+       /* NB: We saved Shadow-Stack-Pointer of setjmp.  Since we are
+              restoring Shadow-Stack-Pointer of setjmp's caller, we
+              need to unwind shadow stack by one more frame.  */
+       addl $1, %edx
+       movl    $255, %ebx
+L(loop):
+       cmpl    %ebx, %edx
+       cmovb   %edx, %ebx
+       incsspd %ebx
+       subl    %ebx, %edx
+       ja      L(loop)
+L(skip_ssp):
+# endif
        /* Save the return address now.  */
        movl (JB_PC*4)(%eax), %edx
        /* Get the stack pointer.  */
@@ -56,6 +97,38 @@ ENTRY (__longjmp)
 #else
        movl 4(%esp), %ecx      /* User's jmp_buf in %ecx.  */
        movl 8(%esp), %eax      /* Second argument is return value.  */
+# ifdef SHADOW_STACK_POINTER_OFFSET
+#  if IS_IN (libc) && defined SHARED
+       /* Check if Shadow Stack is enabled.  */
+       testl $X86_FEATURE_1_SHSTK, %gs:FEATURE_1_OFFSET
+       jz L(skip_ssp)
+#  endif
+       /* Check and adjust the Shadow-Stack-Pointer.  */
+       xorl %edx, %edx
+       /* Get the current ssp.  */
+       rdsspd  %edx
+       /* And compare it with the saved ssp value.  */
+       subl SHADOW_STACK_POINTER_OFFSET(%ecx), %edx
+       je L(skip_ssp)
+       /* Count the number of frames to adjust and adjust it
+          with incssp instruction.  The instruction can adjust
+          the ssp by [0..255] value only thus use a loop if
+          the number of frames is bigger than 255.  */
+       negl %edx
+       shrl $2, %edx
+       /* NB: We saved Shadow-Stack-Pointer of setjmp.  Since we are
+              restoring Shadow-Stack-Pointer of setjmp's caller, we
+              need to unwind shadow stack by one more frame.  */
+       addl $1, %edx
+       movl    $255, %ebx
+L(loop):
+       cmpl    %ebx, %edx
+       cmovb   %edx, %ebx
+       incsspd %ebx
+       subl    %ebx, %edx
+       ja      L(loop)
+L(skip_ssp):
+# endif
        /* Save the return address now.  */
        movl (JB_PC*4)(%ecx), %edx
        LIBC_PROBE (longjmp, 3, 4@%ecx, -4@%eax, 4@%edx)