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. Acked-by: Borislav Petkov <bp@xxxxxxx> Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx> --- arch/x86/kernel/entry_64.S | 52 +++++----------------------------------------- 1 file 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: -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
