diff options
author | Andy Lutomirski <luto@kernel.org> | 2015-10-05 17:48:24 -0700 |
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committer | Ingo Molnar <mingo@kernel.org> | 2015-10-09 09:41:13 +0200 |
commit | f5e6a9753ac2965564a14e6285a06f44043ed9c8 (patch) | |
tree | 0582fb04b19ee92de88288a28f214d07db5abda7 /arch/x86/entry | |
parent | 39b48e575e92e31251b74b4b48cea2129cee90bd (diff) | |
download | linux-f5e6a9753ac2965564a14e6285a06f44043ed9c8.tar.bz2 |
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>
Diffstat (limited to 'arch/x86/entry')
-rw-r--r-- | arch/x86/entry/common.c | 50 |
1 files changed, 29 insertions, 21 deletions
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index 66ccbd664d4c..b53e04d301a3 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 /* |