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| author | Andy Lutomirski <luto@amacapital.net> | 2014-09-05 15:13:56 -0700 |
|---|---|---|
| committer | H. Peter Anvin <hpa@linux.intel.com> | 2014-09-08 14:14:12 -0700 |
| commit | 1dcf74f6edfc3a9acd84d83d8865dd9e2a3b1d1e (patch) | |
| tree | 21030b6f0394f5b82cd17b96fd0008375b3f254b /arch | |
| parent | 54eea9957f5763dd1a2555d7e4cb53b4dd389cc6 (diff) | |
| download | linux-1dcf74f6edfc3a9acd84d83d8865dd9e2a3b1d1e.tar.bz2 | |
x86_64, entry: Use split-phase syscall_trace_enter for 64-bit syscalls
On KVM on my box, this reduces the overhead from an always-accept
seccomp filter from ~130ns to ~17ns. Most of that comes from
avoiding IRET on every syscall when seccomp is enabled.
In extremely approximate hacked-up benchmarking, just bypassing IRET
saves about 80ns, so there's another 43ns of savings here from
simplifying the seccomp path.
The diffstat is also rather nice :)
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/a3dbd267ee990110478d349f78cccfdac5497a84.1409954077.git.luto@amacapital.net
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kernel/entry_64.S | 38 |
1 files changed, 15 insertions, 23 deletions
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index 0bd6d3c28064..df088bb03fb3 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -478,22 +478,6 @@ sysret_signal: #ifdef CONFIG_AUDITSYSCALL /* - * Fast path for syscall audit without full syscall trace. - * We just call __audit_syscall_entry() directly, and then - * jump back to the normal fast path. - */ -auditsys: - movq %r10,%r9 /* 6th arg: 4th syscall arg */ - movq %rdx,%r8 /* 5th arg: 3rd syscall arg */ - movq %rsi,%rcx /* 4th arg: 2nd syscall arg */ - movq %rdi,%rdx /* 3rd arg: 1st syscall arg */ - movq %rax,%rsi /* 2nd arg: syscall number */ - movl $AUDIT_ARCH_X86_64,%edi /* 1st arg: audit arch */ - call __audit_syscall_entry - LOAD_ARGS 0 /* reload call-clobbered registers */ - jmp system_call_fastpath - - /* * 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. @@ -510,17 +494,25 @@ sysret_audit: /* Do syscall tracing */ tracesys: -#ifdef CONFIG_AUDITSYSCALL - testl $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT),TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET) - jz auditsys -#endif + leaq -REST_SKIP(%rsp), %rdi + movq $AUDIT_ARCH_X86_64, %rsi + call syscall_trace_enter_phase1 + test %rax, %rax + jnz tracesys_phase2 /* if needed, run the slow path */ + LOAD_ARGS 0 /* else restore clobbered regs */ + jmp system_call_fastpath /* and return to the fast path */ + +tracesys_phase2: SAVE_REST FIXUP_TOP_OF_STACK %rdi - movq %rsp,%rdi - call syscall_trace_enter + movq %rsp, %rdi + movq $AUDIT_ARCH_X86_64, %rsi + movq %rax,%rdx + call syscall_trace_enter_phase2 + /* * Reload arg registers from stack in case ptrace changed them. - * We don't reload %rax because syscall_trace_enter() returned + * We don't reload %rax because syscall_trace_entry_phase2() returned * the value it wants us to use in the table lookup. */ LOAD_ARGS ARGOFFSET, 1 |