[Qemu-devel] [PATCH 6/7] linux-user: add IBT support to x86 safe-syscall.S

[Paolo Bonzini]

Because safe-syscall.S does not go through the C compiler, the
.note.gnu.property note has to be added manually.  Safe syscalls do not
involve any indirect branch or stack unwinding, so they are trivially
safe for IBT or shadow stacks.

Signed-off-by: Paolo Bonzini <address@hidden>
---
 linux-user/host/i386/safe-syscall.inc.S   | 19 +++++++++++++++++++
 linux-user/host/x86_64/safe-syscall.inc.S | 19 +++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/linux-user/host/i386/safe-syscall.inc.S 
b/linux-user/host/i386/safe-syscall.inc.S
index 9e58fc6504..6c6d568d62 100644
--- a/linux-user/host/i386/safe-syscall.inc.S
+++ b/linux-user/host/i386/safe-syscall.inc.S
@@ -98,3 +98,22 @@ safe_syscall_end:
        .cfi_endproc
 
        .size   safe_syscall_base, .-safe_syscall_base
+
+       .pushsection ".note.gnu.property", "a"
+       .p2align 2
+       .long 1f - 0f          /* name length.  */
+       .long 4f - 1f          /* data length.  */
+       .long 5                /* NT_GNU_PROPERTY_TYPE_0.  */
+0:
+       .asciz "GNU"           /* vendor name.  */
+       .p2align 2
+1:
+        /* GNU_PROPERTY_X86_FEATURE_1_AND.  */
+       .long 0xc0000002       /* pr_type.  */
+       .long 3f - 2f          /* pr_datasz.  */
+2:
+       .long 0x3              /* IBT, SHSTK */
+3:
+       .p2align 2
+4:
+       .popsection
diff --git a/linux-user/host/x86_64/safe-syscall.inc.S 
b/linux-user/host/x86_64/safe-syscall.inc.S
index f36992daa3..e1a57db338 100644
--- a/linux-user/host/x86_64/safe-syscall.inc.S
+++ b/linux-user/host/x86_64/safe-syscall.inc.S
@@ -89,3 +89,22 @@ safe_syscall_end:
         .cfi_endproc
 
         .size   safe_syscall_base, .-safe_syscall_base
+
+       .pushsection ".note.gnu.property", "a"
+       .p2align 3
+       .long 1f - 0f          /* name length.  */
+       .long 4f - 1f          /* data length.  */
+       .long 5                /* NT_GNU_PROPERTY_TYPE_0.  */
+0:
+       .asciz "GNU"           /* vendor name.  */
+       .p2align 3
+1:
+        /* GNU_PROPERTY_X86_FEATURE_1_AND.  */
+       .long 0xc0000002       /* pr_type.  */
+       .long 3f - 2f          /* pr_datasz.  */
+2:
+       .long 0x3              /* IBT, SHSTK */
+3:
+       .p2align 3
+4:
+       .popsection
-- 
2.20.1