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| Started by | Andy Lutomirski <luto@kernel.org> |
|---|---|
| First post | 2015-10-06 02:50 +0200 |
| Last post | 2015-10-09 15:20 +0200 |
| Articles | 2 — 2 participants |
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[PATCH v2 36/36] x86/entry: Split and inline syscall_return_slowpath Andy Lutomirski <luto@kernel.org> - 2015-10-06 02:50 +0200
[tip:x86/asm] x86/entry: Split and inline syscall_return_slowpath () tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2015-10-09 15:20 +0200
| From | Andy Lutomirski <luto@kernel.org> |
|---|---|
| Date | 2015-10-06 02:50 +0200 |
| Subject | [PATCH v2 36/36] x86/entry: Split and inline syscall_return_slowpath |
| Message-ID | <qgoC6-715-15@gated-at.bofh.it> |
GCC is unable to properly optimize functions that have a very short
likely case and a longer and register-heavier cold part -- it fails
to sink all of the register saving and stack frame setup code into
the unlikely part.
Help it out with syscall_return_slowpath by splitting it into two
parts and inline the hot part.
Saves 6 cycles for compat syscalls.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
arch/x86/entry/common.c | 50 ++++++++++++++++++++++++++++---------------------
1 file changed, 29 insertions(+), 21 deletions(-)
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index d6b8f4fd8274..3d64a739e607 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -284,15 +284,40 @@ __visible inline void prepare_exit_to_usermode(struct pt_regs *regs)
user_enter();
}
+#define SYSCALL_EXIT_WORK_FLAGS \
+ (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
+ _TIF_SINGLESTEP | _TIF_SYSCALL_TRACEPOINT)
+
+static void syscall_slow_exit_work(struct pt_regs *regs, u32 cached_flags)
+{
+ bool step;
+
+ audit_syscall_exit(regs);
+
+ if (cached_flags & _TIF_SYSCALL_TRACEPOINT)
+ trace_sys_exit(regs, regs->ax);
+
+ /*
+ * If TIF_SYSCALL_EMU is set, we only get here because of
+ * TIF_SINGLESTEP (i.e. this is PTRACE_SYSEMU_SINGLESTEP).
+ * We already reported this syscall instruction in
+ * syscall_trace_enter().
+ */
+ step = unlikely(
+ (cached_flags & (_TIF_SINGLESTEP | _TIF_SYSCALL_EMU))
+ == _TIF_SINGLESTEP);
+ if (step || cached_flags & _TIF_SYSCALL_TRACE)
+ tracehook_report_syscall_exit(regs, step);
+}
+
/*
* Called with IRQs on and fully valid regs. Returns with IRQs off in a
* state such that we can immediately switch to user mode.
*/
-__visible void syscall_return_slowpath(struct pt_regs *regs)
+__visible inline void syscall_return_slowpath(struct pt_regs *regs)
{
struct thread_info *ti = pt_regs_to_thread_info(regs);
u32 cached_flags = READ_ONCE(ti->flags);
- bool step;
CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
@@ -304,25 +329,8 @@ __visible void syscall_return_slowpath(struct pt_regs *regs)
* First do one-time work. If these work items are enabled, we
* want to run them exactly once per syscall exit with IRQs on.
*/
- if (cached_flags & (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT |
- _TIF_SINGLESTEP | _TIF_SYSCALL_TRACEPOINT)) {
- audit_syscall_exit(regs);
-
- if (cached_flags & _TIF_SYSCALL_TRACEPOINT)
- trace_sys_exit(regs, regs->ax);
-
- /*
- * If TIF_SYSCALL_EMU is set, we only get here because of
- * TIF_SINGLESTEP (i.e. this is PTRACE_SYSEMU_SINGLESTEP).
- * We already reported this syscall instruction in
- * syscall_trace_enter().
- */
- step = unlikely(
- (cached_flags & (_TIF_SINGLESTEP | _TIF_SYSCALL_EMU))
- == _TIF_SINGLESTEP);
- if (step || cached_flags & _TIF_SYSCALL_TRACE)
- tracehook_report_syscall_exit(regs, step);
- }
+ if (unlikely(cached_flags & SYSCALL_EXIT_WORK_FLAGS))
+ syscall_slow_exit_work(regs, cached_flags);
#ifdef CONFIG_COMPAT
/*
--
2.4.3
--
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| From | tip-bot for Andy Lutomirski <tipbot@zytor.com> |
|---|---|
| Date | 2015-10-09 15:20 +0200 |
| Subject | [tip:x86/asm] x86/entry: Split and inline syscall_return_slowpath () |
| Message-ID | <qhFKy-3bI-21@gated-at.bofh.it> |
| In reply to | #1240054 |
Commit-ID: f5e6a9753ac2965564a14e6285a06f44043ed9c8
Gitweb: http://git.kernel.org/tip/f5e6a9753ac2965564a14e6285a06f44043ed9c8
Author: Andy Lutomirski <luto@kernel.org>
AuthorDate: Mon, 5 Oct 2015 17:48:24 -0700
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 9 Oct 2015 09:41:13 +0200
x86/entry: Split and inline syscall_return_slowpath()
GCC is unable to properly optimize functions that have a very
short likely case and a longer and register-heavier cold part --
it fails to sink all of the register saving and stack frame
setup code into the unlikely part.
Help it out with syscall_return_slowpath() by splitting it into
two parts and inline the hot part.
Saves 6 cycles for compat syscalls.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/0f773a894ab15c589ac794c2d34ca6ba9b5335c9.1444091585.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/entry/common.c | 50 ++++++++++++++++++++++++++++---------------------
1 file changed, 29 insertions(+), 21 deletions(-)
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index 66ccbd6..b53e04d 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -284,15 +284,40 @@ __visible inline void prepare_exit_to_usermode(struct pt_regs *regs)
user_enter();
}
+#define SYSCALL_EXIT_WORK_FLAGS \
+ (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
+ _TIF_SINGLESTEP | _TIF_SYSCALL_TRACEPOINT)
+
+static void syscall_slow_exit_work(struct pt_regs *regs, u32 cached_flags)
+{
+ bool step;
+
+ audit_syscall_exit(regs);
+
+ if (cached_flags & _TIF_SYSCALL_TRACEPOINT)
+ trace_sys_exit(regs, regs->ax);
+
+ /*
+ * If TIF_SYSCALL_EMU is set, we only get here because of
+ * TIF_SINGLESTEP (i.e. this is PTRACE_SYSEMU_SINGLESTEP).
+ * We already reported this syscall instruction in
+ * syscall_trace_enter().
+ */
+ step = unlikely(
+ (cached_flags & (_TIF_SINGLESTEP | _TIF_SYSCALL_EMU))
+ == _TIF_SINGLESTEP);
+ if (step || cached_flags & _TIF_SYSCALL_TRACE)
+ tracehook_report_syscall_exit(regs, step);
+}
+
/*
* Called with IRQs on and fully valid regs. Returns with IRQs off in a
* state such that we can immediately switch to user mode.
*/
-__visible void syscall_return_slowpath(struct pt_regs *regs)
+__visible inline void syscall_return_slowpath(struct pt_regs *regs)
{
struct thread_info *ti = pt_regs_to_thread_info(regs);
u32 cached_flags = READ_ONCE(ti->flags);
- bool step;
CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
@@ -304,25 +329,8 @@ __visible void syscall_return_slowpath(struct pt_regs *regs)
* First do one-time work. If these work items are enabled, we
* want to run them exactly once per syscall exit with IRQs on.
*/
- if (cached_flags & (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT |
- _TIF_SINGLESTEP | _TIF_SYSCALL_TRACEPOINT)) {
- audit_syscall_exit(regs);
-
- if (cached_flags & _TIF_SYSCALL_TRACEPOINT)
- trace_sys_exit(regs, regs->ax);
-
- /*
- * If TIF_SYSCALL_EMU is set, we only get here because of
- * TIF_SINGLESTEP (i.e. this is PTRACE_SYSEMU_SINGLESTEP).
- * We already reported this syscall instruction in
- * syscall_trace_enter().
- */
- step = unlikely(
- (cached_flags & (_TIF_SINGLESTEP | _TIF_SYSCALL_EMU))
- == _TIF_SINGLESTEP);
- if (step || cached_flags & _TIF_SYSCALL_TRACE)
- tracehook_report_syscall_exit(regs, step);
- }
+ if (unlikely(cached_flags & SYSCALL_EXIT_WORK_FLAGS))
+ syscall_slow_exit_work(regs, cached_flags);
#ifdef CONFIG_COMPAT
/*
--
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