[PATCH 21/22] perf test: Test BPF prologue

From: Wang Nan
Date: Wed Sep 23 2015 - 07:27:59 EST


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
Link: http://lkml.kernel.org/n/ebpf-6yw9eg0ej3l4jnqhinngkw86@xxxxxxxxxxxxxx
---
tools/perf/tests/Build | 9 ++-
tools/perf/tests/bpf-script-test-prologue.c | 35 ++++++++++++
tools/perf/tests/bpf.c | 89 +++++++++++++++++++++++------
tools/perf/tests/llvm.c | 5 ++
tools/perf/tests/llvm.h | 8 +++
5 files changed, 128 insertions(+), 18 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 4dd701b..5a6290a 100644
--- a/tools/perf/tests/bpf.c
+++ b/tools/perf/tests/bpf.c
@@ -19,11 +19,35 @@ static int epoll_pwait_loop(void)
return 0;
}

-static struct bpf_object *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 struct bpf_object *prepare_bpf(const char *name, void *obj_buf,
+ size_t obj_buf_sz)
{
struct bpf_object *obj;

- obj = bpf__prepare_load_buffer(obj_buf, obj_buf_sz, "[buffer]");
+ obj = bpf__prepare_load_buffer(obj_buf, obj_buf_sz, name);
if (IS_ERR(obj)) {
fprintf(stderr, " (compile failed)");
return NULL;
@@ -31,7 +55,7 @@ static struct bpf_object *prepare_bpf(void *obj_buf, size_t obj_buf_sz)
return obj;
}

-static int do_test(struct bpf_object *obj)
+static int do_test(struct bpf_object *obj, int (*func)(void), int expect)
{
struct record_opts opts = {
.target = {
@@ -101,7 +125,7 @@ static int do_test(struct bpf_object *obj)
}

perf_evlist__enable(evlist);
- epoll_pwait_loop();
+ (*func)();
perf_evlist__disable(evlist);

for (i = 0; i < evlist->nr_mmaps; i++) {
@@ -115,8 +139,8 @@ static int do_test(struct bpf_object *obj)
}
}

- 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;
}

@@ -128,33 +152,32 @@ out:
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;
struct bpf_object *obj;

- 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;
}

- obj = prepare_bpf(obj_buf, obj_buf_sz);
+ obj = prepare_bpf(name, obj_buf, obj_buf_sz);
if (!obj) {
err = -EINVAL;
+ if ((verbose == 0) && (message_load[0] != '\0'))
+ fprintf(stderr, " (%s)", message_load);
goto out;
}

- err = do_test(obj);
+ err = do_test(obj, func, expect);
if (err)
goto out;
out:
@@ -164,6 +187,38 @@ 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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