[PATCH] perf test: Test BPF prologue

[Wang Nan]

This patch introduces a new BPF script to test BPF prologue. The new
script probes at null_lseek, which is the function pointer when we try
to lseek on '/dev/null'.

null_lseek is chosen because it is a function pointer, so we don't need
to consider inlining and LTP.

By extracting file->f_mode, bpf-script-test-prologue.c should know whether
the file is writable or readonly. According to llseek_loop() and
bpf-script-test-prologue.c, one forth of total lseeks should be collected.

This patch improve test__bpf so it can run multiple BPF programs on
different test functions.

Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxxxx>
Cc: Brendan Gregg <brendan.d.gregg@xxxxxxxxx>
Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: He Kuang <hekuang@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Kaixu Xia <xiakaixu@xxxxxxxxxx>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Zefan Li <lizefan@xxxxxxxxxx>
Cc: pi3orama@xxxxxxx
---
 tools/perf/tests/Build                      |  9 ++-
 tools/perf/tests/bpf-script-test-prologue.c | 35 +++++++++++
 tools/perf/tests/bpf.c                      | 93 +++++++++++++++++++++++------
 tools/perf/tests/llvm.c                     |  5 ++
 tools/perf/tests/llvm.h                     |  8 +++
 5 files changed, 130 insertions(+), 20 deletions(-)
 create mode 100644 tools/perf/tests/bpf-script-test-prologue.c

diff --git a/tools/perf/tests/Build b/tools/perf/tests/Build
index 2bd5f37..3e98a97 100644
--- a/tools/perf/tests/Build
+++ b/tools/perf/tests/Build
@@ -32,7 +32,7 @@ perf-y += sample-parsing.o
 perf-y += parse-no-sample-id-all.o
 perf-y += kmod-path.o
 perf-y += thread-map.o
-perf-y += llvm.o llvm-src-base.o llvm-src-kbuild.o
+perf-y += llvm.o llvm-src-base.o llvm-src-kbuild.o llvm-src-prologue.o
 perf-y += bpf.o
 perf-y += topology.o
 
@@ -50,6 +50,13 @@ $(OUTPUT)tests/llvm-src-kbuild.c: tests/bpf-script-test-kbuild.c
 	$(Q)sed -e 's/"/\\"/g' -e 's/\(.*\)/"\1\\n"/g' $< >> $@
 	$(Q)echo ';' >> $@
 
+$(OUTPUT)tests/llvm-src-prologue.c: tests/bpf-script-test-prologue.c
+	$(call rule_mkdir)
+	$(Q)echo '#include <tests/llvm.h>' > $@
+	$(Q)echo 'const char test_llvm__bpf_test_prologue_prog[] =' >> $@
+	$(Q)sed -e 's/"/\\"/g' -e 's/\(.*\)/"\1\\n"/g' $< >> $@
+	$(Q)echo ';' >> $@
+
 perf-$(CONFIG_X86) += perf-time-to-tsc.o
 ifdef CONFIG_AUXTRACE
 perf-$(CONFIG_X86) += insn-x86.o
diff --git a/tools/perf/tests/bpf-script-test-prologue.c b/tools/perf/tests/bpf-script-test-prologue.c
new file mode 100644
index 0000000..7230e62
--- /dev/null
+++ b/tools/perf/tests/bpf-script-test-prologue.c
@@ -0,0 +1,35 @@
+/*
+ * bpf-script-test-prologue.c
+ * Test BPF prologue
+ */
+#ifndef LINUX_VERSION_CODE
+# error Need LINUX_VERSION_CODE
+# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x40200" into llvm section of ~/.perfconfig'
+#endif
+#define SEC(NAME) __attribute__((section(NAME), used))
+
+#include <uapi/linux/fs.h>
+
+#define FMODE_READ		0x1
+#define FMODE_WRITE		0x2
+
+static void (*bpf_trace_printk)(const char *fmt, int fmt_size, ...) =
+	(void *) 6;
+
+SEC("func=null_lseek file->f_mode offset orig")
+int bpf_func__null_lseek(void *ctx, int err, unsigned long f_mode,
+			 unsigned long offset, unsigned long orig)
+{
+	if (err)
+		return 0;
+	if (f_mode & FMODE_WRITE)
+		return 0;
+	if (offset & 1)
+		return 0;
+	if (orig == SEEK_CUR)
+		return 0;
+	return 1;
+}
+
+char _license[] SEC("license") = "GPL";
+int _version SEC("version") = LINUX_VERSION_CODE;
diff --git a/tools/perf/tests/bpf.c b/tools/perf/tests/bpf.c
index 64aaab68..6305b3d 100644
--- a/tools/perf/tests/bpf.c
+++ b/tools/perf/tests/bpf.c
@@ -19,14 +19,37 @@ static int epoll_pwait_loop(void)
 	return 0;
 }
 
-static int prepare_bpf(void *obj_buf, size_t obj_buf_sz)
+#ifdef HAVE_BPF_PROLOGUE
+
+static int llseek_loop(void)
+{
+	int fds[2], i;
+
+	fds[0] = open("/dev/null", O_RDONLY);
+	fds[1] = open("/dev/null", O_RDWR);
+
+	if (fds[0] < 0 || fds[1] < 0)
+		return -1;
+
+	for (i = 0; i < NR_ITERS; i++) {
+		lseek(fds[i % 2], i, (i / 2) % 2 ? SEEK_CUR : SEEK_SET);
+		lseek(fds[(i + 1) % 2], i, (i / 2) % 2 ? SEEK_CUR : SEEK_SET);
+	}
+	close(fds[0]);
+	close(fds[1]);
+	return 0;
+}
+
+#endif
+
+static int prepare_bpf(const char *name, void *obj_buf, size_t obj_buf_sz)
 {
 	int err;
 	char errbuf[BUFSIZ];
 
-	err = bpf__prepare_load_buffer(obj_buf, obj_buf_sz, NULL);
+	err = bpf__prepare_load_buffer(obj_buf, obj_buf_sz, name);
 	if (err) {
-		bpf__strerror_prepare_load("[buffer]", false, err, errbuf,
+		bpf__strerror_prepare_load(name, false, err, errbuf,
 					   sizeof(errbuf));
 		fprintf(stderr, " (%s)", errbuf);
 		return TEST_FAIL;
@@ -49,7 +72,7 @@ static int prepare_bpf(void *obj_buf, size_t obj_buf_sz)
 	return 0;
 }
 
-static int do_test(void)
+static int do_test(int (*func)(void), int expect)
 {
 	struct record_opts opts = {
 		.target = {
@@ -106,7 +129,7 @@ static int do_test(void)
 	}
 
 	perf_evlist__enable(evlist);
-	epoll_pwait_loop();
+	(*func)();
 	perf_evlist__disable(evlist);
 
 	for (i = 0; i < evlist->nr_mmaps; i++) {
@@ -120,8 +143,8 @@ static int do_test(void)
 		}
 	}
 
-	if (count != (NR_ITERS + 1) / 2) {
-		fprintf(stderr, " (filter result incorrect)");
+	if (count != expect) {
+		fprintf(stderr, " (filter result incorrect: %d != %d)", count, expect);
 		err = -EBADF;
 	}
 
@@ -132,30 +155,30 @@ out_delete_evlist:
 	return 0;
 }
 
-int test__bpf(void)
+static int __test__bpf(int index, const char *name,
+		       const char *message_compile,
+		       const char *message_load,
+		       int (*func)(void), int expect)
 {
 	int err;
 	void *obj_buf;
 	size_t obj_buf_sz;
 
-	if (geteuid() != 0) {
-		fprintf(stderr, " (try run as root)");
-		return TEST_SKIP;
-	}
-
-	test_llvm__fetch_bpf_obj(&obj_buf, &obj_buf_sz, LLVM_TESTCASE_BASE);
-
+	test_llvm__fetch_bpf_obj(&obj_buf, &obj_buf_sz, index);
 	if (!obj_buf || !obj_buf_sz) {
 		if (verbose == 0)
-			fprintf(stderr, " (fix 'perf test LLVM' first)");
+			fprintf(stderr, " (%s)", message_compile);
 		return TEST_SKIP;
 	}
 
-	err = prepare_bpf(obj_buf, obj_buf_sz);
-	if (err)
+	err = prepare_bpf(name, obj_buf, obj_buf_sz);
+	if (err) {
+		if ((verbose == 0) && (message_load[0] != '\0'))
+			fprintf(stderr, " (%s)", message_load);
 		goto out;
+	}
 
-	err = do_test();
+	err = do_test(func, expect);
 	if (err)
 		goto out;
 out:
@@ -166,6 +189,38 @@ out:
 	return 0;
 }
 
+int test__bpf(void)
+{
+	int err;
+
+	if (geteuid() != 0) {
+		fprintf(stderr, " (try run as root)");
+		return TEST_SKIP;
+	}
+
+	err = __test__bpf(LLVM_TESTCASE_BASE,
+			  "[basic_bpf_test]",
+			  "fix 'perf test LLVM' first",
+			  "load bpf object failed",
+			  &epoll_pwait_loop,
+			  (NR_ITERS + 1) / 2);
+	if (err)
+		return err;
+
+#ifdef HAVE_BPF_PROLOGUE
+	err = __test__bpf(LLVM_TESTCASE_BPF_PROLOGUE,
+			  "[bpf_prologue_test]",
+			  "fix kbuild first",
+			  "check your vmlinux setting?",
+			  &llseek_loop,
+			  (NR_ITERS + 1) / 4);
+	return err;
+#else
+	fprintf(stderr, " (skip BPF prologue test)");
+	return TEST_OK;
+#endif
+}
+
 #else
 int test__bpf(void)
 {
diff --git a/tools/perf/tests/llvm.c b/tools/perf/tests/llvm.c
index 75cd99f..e722e8a 100644
--- a/tools/perf/tests/llvm.c
+++ b/tools/perf/tests/llvm.c
@@ -22,6 +22,11 @@ struct llvm_testcase {
 	[LLVM_TESTCASE_KBUILD]	= {.source = test_llvm__bpf_test_kbuild_prog,
 				   .errmsg = "llvm.kbuild-dir can be fixed",
 				   .tried = false},
+	/* Don't output if this one fail. */
+	[LLVM_TESTCASE_BPF_PROLOGUE]	= {
+				   .source = test_llvm__bpf_test_prologue_prog,
+				   .errmsg = "failed for unknown reason",
+				   .tried = false},
 	{.source = NULL}
 };
 
diff --git a/tools/perf/tests/llvm.h b/tools/perf/tests/llvm.h
index 78ec01d..c00c1be 100644
--- a/tools/perf/tests/llvm.h
+++ b/tools/perf/tests/llvm.h
@@ -10,10 +10,18 @@ struct test_llvm__bpf_result {
 
 extern const char test_llvm__bpf_prog[];
 extern const char test_llvm__bpf_test_kbuild_prog[];
+extern const char test_llvm__bpf_test_prologue_prog[];
 
 enum test_llvm__testcase {
 	LLVM_TESTCASE_BASE,
 	LLVM_TESTCASE_KBUILD,
+	/*
+	 * We must put LLVM_TESTCASE_BPF_PROLOGUE after
+	 * LLVM_TESTCASE_KBUILD, so if kbuild test failed,
+	 * don't need to try this one, because it depend on
+	 * kernel header.
+	 */
+	LLVM_TESTCASE_BPF_PROLOGUE,
 	NR_LLVM_TESTCASES,
 };
 void test_llvm__fetch_bpf_obj(void **p_obj_buf, size_t *p_obj_buf_sz, int index);
-- 
1.8.3.4

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