Messages in this thread Patch in this message | | | From | Denys Vlasenko <> | Subject | [PATCH 5/9] x86/asm/entry/64: if execve fails, no need to use IRET return | Date | Thu, 2 Apr 2015 16:36:14 +0200 |
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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 <dvlasenk@redhat.com> CC: Linus Torvalds <torvalds@linux-foundation.org> CC: Steven Rostedt <rostedt@goodmis.org> CC: Ingo Molnar <mingo@kernel.org> CC: Borislav Petkov <bp@alien8.de> CC: "H. Peter Anvin" <hpa@zytor.com> CC: Andy Lutomirski <luto@amacapital.net> CC: Oleg Nesterov <oleg@redhat.com> CC: Frederic Weisbecker <fweisbec@gmail.com> CC: Alexei Starovoitov <ast@plumgrid.com> CC: Will Drewry <wad@chromium.org> CC: Kees Cook <keescook@chromium.org> CC: x86@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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