From: Denys Vlasenko <dvlasenk@redhat.com>
To: Ingo Molnar <mingo@kernel.org>
Cc: Denys Vlasenko <dvlasenk@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Steven Rostedt <rostedt@goodmis.org>,
Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>,
Andy Lutomirski <luto@amacapital.net>,
Oleg Nesterov <oleg@redhat.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Alexei Starovoitov <ast@plumgrid.com>,
Will Drewry <wad@chromium.org>, Kees Cook <keescook@chromium.org>,
x86@kernel.org, linux-kernel@vger.kernel.org
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 [thread overview]
Message-ID: <1427985378-4287-5-git-send-email-dvlasenk@redhat.com> (raw)
In-Reply-To: <1427985378-4287-1-git-send-email-dvlasenk@redhat.com>
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
next prev parent reply other threads:[~2015-04-02 14:36 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-02 14:36 [PATCH 1/9] x86/asm/entry/64: reuse stub return code Denys Vlasenko
2015-04-02 14:36 ` [PATCH 2/9] x86/asm/entry/64: optimize [v]fork/clone stubs Denys Vlasenko
2015-04-02 14:36 ` [PATCH 3/9] x86/asm/entry/64: do not SAVE_EXTRA_REGS in stub_sigreturn Denys Vlasenko
2015-04-02 15:01 ` Brian Gerst
2015-04-02 15:20 ` Denys Vlasenko
2015-04-02 19:10 ` Brian Gerst
2015-04-02 19:40 ` Denys Vlasenko
2015-04-02 19:40 ` Andy Lutomirski
2015-04-02 14:36 ` [PATCH 4/9] x86/asm/entry/64: delay popping return address in stubs Denys Vlasenko
2015-04-02 14:36 ` Denys Vlasenko [this message]
2015-04-02 14:36 ` [PATCH 6/9] x86/asm/entry/64: reuse stub epilogue by ret_from_fork Denys Vlasenko
2015-04-02 14:36 ` [PATCH 7/9] x86/asm/entry/64: remove a redundant jump Denys Vlasenko
2015-04-02 14:36 ` [PATCH 8/9] x86/asm/entry/64: simplify jumps in ret_from_fork Denys Vlasenko
2015-04-02 14:36 ` [PATCH 9/9] x86/asm/entry/64: Remove GET_THREAD_INFO " Denys Vlasenko
2015-04-02 19:02 ` Andy Lutomirski
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