It's useful to see how much (at a minimum) each filter adds to the syscall overhead. Add additional calculations.

Signed-off-by: Kees Cook keescook@chromium.org --- As part of the performance discussions, this is what I'm adding to the seccomp selftest in for-next/seccomp to get more details. https://lore.kernel.org/linux-security-module/202006011116.3F7109A@keescook/... This does not include the BPF-bypass mode, which I don't see a way to do without creating major problems with seccomp. ;) --- .../selftests/seccomp/seccomp_benchmark.c | 36 +++++++++++++++---- tools/testing/selftests/seccomp/seccomp_bpf.c | 2 -- 2 files changed, 29 insertions(+), 9 deletions(-)

diff --git a/tools/testing/selftests/seccomp/seccomp_benchmark.c b/tools/testing/selftests/seccomp/seccomp_benchmark.c index 5838c8697ec3..eca13fe1fba9 100644 --- a/tools/testing/selftests/seccomp/seccomp_benchmark.c +++ b/tools/testing/selftests/seccomp/seccomp_benchmark.c @@ -68,32 +68,54 @@ int main(int argc, char *argv[]) }; long ret; unsigned long long samples; - unsigned long long native, filtered; + unsigned long long native, filter1, filter2;

if (argc > 1) samples = strtoull(argv[1], NULL, 0); else samples = calibrate();

+ printf("Current BPF sysctl settings:\n"); + system("sysctl net.core.bpf_jit_enable"); + system("sysctl net.core.bpf_jit_harden"); printf("Benchmarking %llu samples...\n", samples);

+ /* Native call */ native = timing(CLOCK_PROCESS_CPUTIME_ID, samples) / samples; printf("getpid native: %llu ns\n", native);

ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0); assert(ret == 0);

+ /* One filter */ ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog); assert(ret == 0);

- filtered = timing(CLOCK_PROCESS_CPUTIME_ID, samples) / samples; - printf("getpid RET_ALLOW: %llu ns\n", filtered); + filter1 = timing(CLOCK_PROCESS_CPUTIME_ID, samples) / samples; + printf("getpid RET_ALLOW 1 filter: %llu ns\n", filter1);

- printf("Estimated seccomp overhead per syscall: %llu ns\n", - filtered - native); + if (filter1 == native) + printf("No overhead measured!? Try running again with more samples.\n");

- if (filtered == native) - printf("Trying running again with more samples.\n"); + /* Two filters */ + ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog); + assert(ret == 0); + + filter2 = timing(CLOCK_PROCESS_CPUTIME_ID, samples) / samples; + printf("getpid RET_ALLOW 2 filters: %llu ns\n", filter2); + + /* Calculations */ + printf("Estimated total seccomp overhead for 1 filter: %llu ns\n", + filter1 - native); + + printf("Estimated total seccomp overhead for 2 filters: %llu ns\n", + filter2 - native); + + printf("Estimated seccomp per-filter overhead: %llu ns\n", + filter2 - filter1); + + printf("Estimated seccomp entry overhead: %llu ns\n", + filter1 - native - (filter2 - filter1));

return 0; } diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c index 4dae278cf77e..402ccb3a4e52 100644 --- a/tools/testing/selftests/seccomp/seccomp_bpf.c +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c @@ -3824,7 +3824,6 @@ TEST(user_notification_filter_empty_threaded)

/* * TODO: - * - add microbenchmarks * - expand NNP testing * - better arch-specific TRACE and TRAP handlers. * - endianness checking when appropriate @@ -3832,7 +3831,6 @@ TEST(user_notification_filter_empty_threaded) * - arch value testing (x86 modes especially) * - verify that FILTER_FLAG_LOG filters generate log messages * - verify that RET_LOG generates log messages - * - ... */

TEST_HARNESS_MAIN