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/*
* Strictly speaking, this is not a test. But it can report during test
* runs so relative performace can be measured.
*/
#define _GNU_SOURCE
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>
#include <linux/filter.h>
#include <linux/seccomp.h>
#include <sys/prctl.h>
#include <sys/syscall.h>
#include <sys/types.h>
#define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
unsigned long long timing(clockid_t clk_id, unsigned long long samples)
{
pid_t pid, ret;
unsigned long long i;
struct timespec start, finish;
pid = getpid();
assert(clock_gettime(clk_id, &start) == 0);
for (i = 0; i < samples; i++) {
ret = syscall(__NR_getpid);
assert(pid == ret);
}
assert(clock_gettime(clk_id, &finish) == 0);
i = finish.tv_sec - start.tv_sec;
i *= 1000000000;
i += finish.tv_nsec - start.tv_nsec;
printf("%lu.%09lu - %lu.%09lu = %llu\n",
finish.tv_sec, finish.tv_nsec,
start.tv_sec, start.tv_nsec,
i);
return i;
}
unsigned long long calibrate(void)
{
unsigned long long i;
printf("Calibrating reasonable sample size...\n");
for (i = 5; ; i++) {
unsigned long long samples = 1 << i;
/* Find something that takes more than 5 seconds to run. */
if (timing(CLOCK_REALTIME, samples) / 1000000000ULL > 5)
return samples;
}
}
int main(int argc, char *argv[])
{
struct sock_filter filter[] = {
BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
};
struct sock_fprog prog = {
.len = (unsigned short)ARRAY_SIZE(filter),
.filter = filter,
};
long ret;
unsigned long long samples;
unsigned long long native, filtered;
if (argc > 1)
samples = strtoull(argv[1], NULL, 0);
else
samples = calibrate();
printf("Benchmarking %llu samples...\n", samples);
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);
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);
printf("Estimated seccomp overhead per syscall: %llu ns\n",
filtered - native);
if (filtered == native)
printf("Trying running again with more samples.\n");
return 0;
}
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