This makes failed execve's faster.
This also enables a future possible optimization: SAVE_EXTRA_REGS can be avoided
in execve's.
Run-tested.
Signed-off-by: Denys Vlasenko <dvlas...@redhat.com>
CC: Linus Torvalds <torva...@linux-foundation.org>
CC: Steven Rostedt <rost...@goodmis.org>
CC: Ingo Molnar <mi...@kernel.org>
CC: Borislav Petkov <b...@alien8.de>
CC: "H. Peter Anvin" <h...@zytor.com>
CC: Andy Lutomirski <l...@amacapital.net>
CC: Oleg Nesterov <o...@redhat.com>
CC: Frederic Weisbecker <fweis...@gmail.com>
CC: Alexei Starovoitov <a...@plumgrid.com>
CC: Will Drewry <w...@chromium.org>
CC: Kees Cook <keesc...@chromium.org>
CC: x...@kernel.org
CC: linux-kernel@vger.kernel.org
---
arch/x86/kernel/entry_64.S | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 060cb2e..e8f2aeb 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -421,6 +421,11 @@ ENTRY(stub_execve)
DEFAULT_FRAME 0, 8
SAVE_EXTRA_REGS 8
call sys_execve
+return_from_exec:
+ testl %eax,%eax
+ jz return_from_stub
+ /* exec failed, can use fast SYSRET code path in this case */
+ ret
return_from_stub:
addq $8, %rsp
movq %rax,RAX(%rsp)
@@ -434,7 +439,7 @@ ENTRY(stub_execveat)
DEFAULT_FRAME 0, 8
SAVE_EXTRA_REGS 8
call sys_execveat
- jmp return_from_stub
+ jmp return_from_exec
CFI_ENDPROC
END(stub_execveat)
@@ -471,7 +476,7 @@ ENTRY(stub_x32_execve)
DEFAULT_FRAME 0, 8
SAVE_EXTRA_REGS 8
call compat_sys_execve
- jmp return_from_stub
+ jmp return_from_exec
CFI_ENDPROC
END(stub_x32_execve)
@@ -480,7 +485,7 @@ ENTRY(stub_x32_execveat)
DEFAULT_FRAME 0, 8
SAVE_EXTRA_REGS 8
call compat_sys_execveat
- jmp return_from_stub
+ jmp return_from_exec
CFI_ENDPROC
END(stub_x32_execveat)
--
1.8.1.4
--
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