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

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Message-Id: <20200616074934.1600036-2-keescook@chromium.org>
Date:   Tue, 16 Jun 2020 00:49:27 -0700
From:   Kees Cook <keescook@...omium.org>
To:     linux-kernel@...r.kernel.org
Cc:     Kees Cook <keescook@...omium.org>,
        Christian Brauner <christian@...uner.io>,
        Sargun Dhillon <sargun@...gun.me>,
        Tycho Andersen <tycho@...ho.ws>, Jann Horn <jannh@...gle.com>,
        "zhujianwei (C)" <zhujianwei7@...wei.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Matthew Wilcox <willy@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Will Drewry <wad@...omium.org>, Shuah Khan <shuah@...nel.org>,
        Matt Denton <mpdenton@...gle.com>,
        Chris Palmer <palmer@...gle.com>,
        Jeffrey Vander Stoep <jeffv@...gle.com>,
        Aleksa Sarai <cyphar@...har.com>,
        Hehuazhen <hehuazhen@...wei.com>, x86@...nel.org,
        Linux Containers <containers@...ts.linux-foundation.org>,
        linux-security-module@...r.kernel.org, linux-api@...r.kernel.org
Subject: [PATCH 1/8] selftests/seccomp: Improve calibration loop

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@...omium.org>
---
 .../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