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amd64: annotate the syscall return address check with __predict_false

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before:
   0xffffffff80b03ebb <+2059>:	mov    0x460(%r14),%rax
   0xffffffff80b03ec2 <+2066>:	mov    0x98(%rax),%rax
   0xffffffff80b03ec9 <+2073>:	shr    $0x2f,%rax
   0xffffffff80b03ecd <+2077>:	je     0xffffffff80b03edd <amd64_syscall+2093>
   0xffffffff80b03ecf <+2079>:	mov    0x3f8(%r14),%rax
   0xffffffff80b03ed6 <+2086>:	orl    $0x1,0xc8(%rax)
   0xffffffff80b03edd <+2093>:	add    $0xf8,%rsp

after:
   0xffffffff80b03ebb <+2059>:	mov    0x460(%r14),%rax
   0xffffffff80b03ec2 <+2066>:	mov    0x98(%rax),%rax
   0xffffffff80b03ec9 <+2073>:	shr    $0x2f,%rax
   0xffffffff80b03ecd <+2077>:	jne    0xffffffff80b03eef <amd64_syscall+2111>
   0xffffffff80b03ecf <+2079>:	add    $0xf8,%rsp

Reviewed by:	kib
MFC after:	1 week
This commit is contained in:
mjg 2017-08-02 11:25:38 +00:00
parent 5ce01a6461
commit 420c428175
1 changed files with 1 additions and 1 deletions
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2
sys/amd64/amd64/trap.c
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@ -935,6 +935,6 @@ amd64_syscall(struct thread *td, int traced)
* not be safe. Instead, use the full return path which
* catches the problem safely.
*/
if (td->td_frame->tf_rip >= VM_MAXUSER_ADDRESS)
if (__predict_false(td->td_frame->tf_rip >= VM_MAXUSER_ADDRESS))
set_pcb_flags(td->td_pcb, PCB_FULL_IRET);
}