提交 96b6352c 编写于 作者: A Andy Lutomirski

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.netAcked-by: NBorislav Petkov <bp@suse.de>
Signed-off-by: NAndy Lutomirski <luto@amacapital.net>
上级 2a23c6b8
......@@ -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:
......
Markdown is supported
0% .
You are about to add 0 people to the discussion. Proceed with caution.
先完成此消息的编辑!
想要评论请 注册