[PATCH 1/8] selftests/seccomp: Improve calibration loop

From: Kees Cook
Date: Tue Jun 16 2020 - 03:49:52 EST


The seccomp benchmark calibration loop did not need to take so long.
Instead, use a simple 1 second timeout and multiply up to target. It
does not need to be accurate.

Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
.../selftests/seccomp/seccomp_benchmark.c | 50 ++++++++++++-------
1 file changed, 32 insertions(+), 18 deletions(-)

diff --git a/tools/testing/selftests/seccomp/seccomp_benchmark.c b/tools/testing/selftests/seccomp/seccomp_benchmark.c
index eca13fe1fba9..91f5a89cadac 100644
--- a/tools/testing/selftests/seccomp/seccomp_benchmark.c
+++ b/tools/testing/selftests/seccomp/seccomp_benchmark.c
@@ -18,9 +18,9 @@

unsigned long long timing(clockid_t clk_id, unsigned long long samples)
{
- pid_t pid, ret;
- unsigned long long i;
struct timespec start, finish;
+ unsigned long long i;
+ pid_t pid, ret;

pid = getpid();
assert(clock_gettime(clk_id, &start) == 0);
@@ -31,30 +31,43 @@ unsigned long long timing(clockid_t clk_id, unsigned long long samples)
assert(clock_gettime(clk_id, &finish) == 0);

i = finish.tv_sec - start.tv_sec;
- i *= 1000000000;
+ i *= 1000000000ULL;
i += finish.tv_nsec - start.tv_nsec;

- printf("%lu.%09lu - %lu.%09lu = %llu\n",
+ printf("%lu.%09lu - %lu.%09lu = %llu (%.1fs)\n",
finish.tv_sec, finish.tv_nsec,
start.tv_sec, start.tv_nsec,
- i);
+ i, (double)i / 1000000000.0);

return i;
}

unsigned long long calibrate(void)
{
- unsigned long long i;
-
- printf("Calibrating reasonable sample size...\n");
+ struct timespec start, finish;
+ unsigned long long i, samples, step = 9973;
+ pid_t pid, ret;
+ int seconds = 15;

- for (i = 5; ; i++) {
- unsigned long long samples = 1 << i;
+ printf("Calibrating sample size for %d seconds worth of syscalls ...\n", seconds);

- /* Find something that takes more than 5 seconds to run. */
- if (timing(CLOCK_REALTIME, samples) / 1000000000ULL > 5)
- return samples;
- }
+ samples = 0;
+ pid = getpid();
+ assert(clock_gettime(CLOCK_MONOTONIC, &start) == 0);
+ do {
+ for (i = 0; i < step; i++) {
+ ret = syscall(__NR_getpid);
+ assert(pid == ret);
+ }
+ assert(clock_gettime(CLOCK_MONOTONIC, &finish) == 0);
+
+ samples += step;
+ i = finish.tv_sec - start.tv_sec;
+ i *= 1000000000ULL;
+ i += finish.tv_nsec - start.tv_nsec;
+ } while (i < 1000000000ULL);
+
+ return samples * seconds;
}

int main(int argc, char *argv[])
@@ -70,15 +83,16 @@ int main(int argc, char *argv[])
unsigned long long samples;
unsigned long long native, filter1, filter2;

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

/* Native call */
native = timing(CLOCK_PROCESS_CPUTIME_ID, samples) / samples;
--
2.25.1