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authorAndy Lutomirski <luto@amacapital.net>2014-07-07 11:37:17 -0700
committerAndy Lutomirski <luto@amacapital.net>2015-02-01 04:03:02 -0800
commit96b6352c12711d5c0bb7157f49c92580248e8146 (patch)
tree66414331ab05782fbecaf68aeb081cc8ea7d1c29
parent2a23c6b8a9c42620182a2d2cfc7c16f6ff8c42b4 (diff)
x86_64, entry: Remove the syscall exit audit and schedule optimizations
We used to optimize rescheduling and audit on syscall exit. Now that the full slow path is reasonably fast, remove these optimizations. Syscall exit auditing is now handled exclusively by syscall_trace_leave. This adds something like 10ns to the previously optimized paths on my computer, presumably due mostly to SAVE_REST / RESTORE_REST. I think that we should eventually replace both the syscall and non-paranoid interrupt exit slow paths with a pair of C functions along the lines of the syscall entry hooks. Link: http://lkml.kernel.org/r/22f2aa4a0361707a5cfb1de9d45260b39965dead.1421453410.git.luto@amacapital.net Acked-by: Borislav Petkov <bp@suse.de> Signed-off-by: Andy Lutomirski <luto@amacapital.net>
-rw-r--r--arch/x86/kernel/entry_64.S52
1 files changed, 5 insertions, 47 deletions
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index eeab4cf8b2c9..db13655c3a2a 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -361,15 +361,12 @@ system_call_fastpath:
* Has incomplete stack frame and undefined top of stack.
*/
ret_from_sys_call:
- movl $_TIF_ALLWORK_MASK,%edi
- /* edi: flagmask */
-sysret_check:
+ testl $_TIF_ALLWORK_MASK,TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET)
+ jnz int_ret_from_sys_call_fixup /* Go the the slow path */
+
LOCKDEP_SYS_EXIT
DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
- movl TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET),%edx
- andl %edi,%edx
- jnz sysret_careful
CFI_REMEMBER_STATE
/*
* sysretq will re-enable interrupts:
@@ -383,49 +380,10 @@ sysret_check:
USERGS_SYSRET64
CFI_RESTORE_STATE
- /* Handle reschedules */
- /* edx: work, edi: workmask */
-sysret_careful:
- bt $TIF_NEED_RESCHED,%edx
- jnc sysret_signal
- TRACE_IRQS_ON
- ENABLE_INTERRUPTS(CLBR_NONE)
- pushq_cfi %rdi
- SCHEDULE_USER
- popq_cfi %rdi
- jmp sysret_check
- /* Handle a signal */
-sysret_signal:
- TRACE_IRQS_ON
- ENABLE_INTERRUPTS(CLBR_NONE)
-#ifdef CONFIG_AUDITSYSCALL
- bt $TIF_SYSCALL_AUDIT,%edx
- jc sysret_audit
-#endif
- /*
- * We have a signal, or exit tracing or single-step.
- * These all wind up with the iret return path anyway,
- * so just join that path right now.
- */
+int_ret_from_sys_call_fixup:
FIXUP_TOP_OF_STACK %r11, -ARGOFFSET
- jmp int_check_syscall_exit_work
-
-#ifdef CONFIG_AUDITSYSCALL
- /*
- * Return fast path for syscall audit. Call __audit_syscall_exit()
- * directly and then jump back to the fast path with TIF_SYSCALL_AUDIT
- * masked off.
- */
-sysret_audit:
- movq RAX-ARGOFFSET(%rsp),%rsi /* second arg, syscall return value */
- cmpq $-MAX_ERRNO,%rsi /* is it < -MAX_ERRNO? */
- setbe %al /* 1 if so, 0 if not */
- movzbl %al,%edi /* zero-extend that into %edi */
- call __audit_syscall_exit
- movl $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT),%edi
- jmp sysret_check
-#endif /* CONFIG_AUDITSYSCALL */
+ jmp int_ret_from_sys_call
/* Do syscall tracing */
tracesys: