Re: [PATCH RFC v2 bpf-next 7/9] selftests/bpf: Replace extract_build_id with read_build_id

From: Andrii Nakryiko
Date: Tue Mar 07 2023 - 20:26:53 EST

On Tue, Feb 28, 2023 at 1:33 AM Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
>
> Replacing extract_build_id with read_build_id that parses out
> build id directly from elf without using readelf tool.
>
> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> ---

small nit below, but looks good. Thanks for clean up!

Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>

> .../bpf/prog_tests/stacktrace_build_id.c | 19 ++++++--------
> .../bpf/prog_tests/stacktrace_build_id_nmi.c | 17 +++++--------
> tools/testing/selftests/bpf/test_progs.c | 25 -------------------
> tools/testing/selftests/bpf/test_progs.h | 1 -
> 4 files changed, 13 insertions(+), 49 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id.c b/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id.c
> index 9ad09a6c538a..9e4b76ee356f 100644
> --- a/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id.c
> +++ b/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id.c
> @@ -7,13 +7,12 @@ void test_stacktrace_build_id(void)
>
> int control_map_fd, stackid_hmap_fd, stackmap_fd, stack_amap_fd;
> struct test_stacktrace_build_id *skel;
> - int err, stack_trace_len;
> + int err, stack_trace_len, build_id_size;
> __u32 key, prev_key, val, duration = 0;
> - char buf[256];
> - int i, j;
> + char buf[BPF_BUILD_ID_SIZE];
> struct bpf_stack_build_id id_offs[PERF_MAX_STACK_DEPTH];
> int build_id_matches = 0;
> - int retry = 1;
> + int i, retry = 1;
>
> retry:
> skel = test_stacktrace_build_id__open_and_load();
> @@ -52,9 +51,10 @@ void test_stacktrace_build_id(void)
> "err %d errno %d\n", err, errno))
> goto cleanup;
>
> - err = extract_build_id(buf, 256);
> + build_id_size = read_build_id("./urandom_read", buf);

nit: "urandom_read" vs "./urandom_read" matters only when executing
binary, not when opening a file. So all these "./" just creates
unnecessary confusion, IMO

> + err = build_id_size < 0 ? build_id_size : 0;
>
> - if (CHECK(err, "get build_id with readelf",
> + if (CHECK(err, "read_build_id",
> "err %d errno %d\n", err, errno))
> goto cleanup;
>
> @@ -64,8 +64,6 @@ void test_stacktrace_build_id(void)
> goto cleanup;
>
> do {
> - char build_id[64];
> -
> err = bpf_map_lookup_elem(stackmap_fd, &key, id_offs);
> if (CHECK(err, "lookup_elem from stackmap",
> "err %d, errno %d\n", err, errno))
> @@ -73,10 +71,7 @@ void test_stacktrace_build_id(void)
> for (i = 0; i < PERF_MAX_STACK_DEPTH; ++i)
> if (id_offs[i].status == BPF_STACK_BUILD_ID_VALID &&
> id_offs[i].offset != 0) {
> - for (j = 0; j < 20; ++j)
> - sprintf(build_id + 2 * j, "%02x",
> - id_offs[i].build_id[j] & 0xff);
> - if (strstr(buf, build_id) != NULL)
> + if (memcmp(buf, id_offs[i].build_id, build_id_size) == 0)
> build_id_matches = 1;
> }
> prev_key = key;
> diff --git a/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c b/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c
> index f4ea1a215ce4..8d84149ebcc7 100644
> --- a/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c
> +++ b/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c
> @@ -28,11 +28,10 @@ void test_stacktrace_build_id_nmi(void)
> .config = PERF_COUNT_HW_CPU_CYCLES,
> };
> __u32 key, prev_key, val, duration = 0;
> - char buf[256];
> - int i, j;
> + char buf[BPF_BUILD_ID_SIZE];
> struct bpf_stack_build_id id_offs[PERF_MAX_STACK_DEPTH];
> - int build_id_matches = 0;
> - int retry = 1;
> + int build_id_matches = 0, build_id_size;
> + int i, retry = 1;
>
> attr.sample_freq = read_perf_max_sample_freq();
>
> @@ -94,7 +93,8 @@ void test_stacktrace_build_id_nmi(void)
> "err %d errno %d\n", err, errno))
> goto cleanup;
>
> - err = extract_build_id(buf, 256);
> + build_id_size = read_build_id("./urandom_read", buf);
> + err = build_id_size < 0 ? build_id_size : 0;
>
> if (CHECK(err, "get build_id with readelf",
> "err %d errno %d\n", err, errno))
> @@ -106,8 +106,6 @@ void test_stacktrace_build_id_nmi(void)
> goto cleanup;
>
> do {
> - char build_id[64];
> -
> err = bpf_map__lookup_elem(skel->maps.stackmap, &key, sizeof(key),
> id_offs, sizeof(id_offs), 0);
> if (CHECK(err, "lookup_elem from stackmap",
> @@ -116,10 +114,7 @@ void test_stacktrace_build_id_nmi(void)
> for (i = 0; i < PERF_MAX_STACK_DEPTH; ++i)
> if (id_offs[i].status == BPF_STACK_BUILD_ID_VALID &&
> id_offs[i].offset != 0) {
> - for (j = 0; j < 20; ++j)
> - sprintf(build_id + 2 * j, "%02x",
> - id_offs[i].build_id[j] & 0xff);
> - if (strstr(buf, build_id) != NULL)
> + if (memcmp(buf, id_offs[i].build_id, build_id_size) == 0)
> build_id_matches = 1;
> }
> prev_key = key;
> diff --git a/tools/testing/selftests/bpf/test_progs.c b/tools/testing/selftests/bpf/test_progs.c
> index 6d5e3022c75f..9813d53c4878 100644
> --- a/tools/testing/selftests/bpf/test_progs.c
> +++ b/tools/testing/selftests/bpf/test_progs.c
> @@ -591,31 +591,6 @@ int compare_stack_ips(int smap_fd, int amap_fd, int stack_trace_len)
> return err;
> }
>
> -int extract_build_id(char *build_id, size_t size)
> -{
> - FILE *fp;
> - char *line = NULL;
> - size_t len = 0;
> -
> - fp = popen("readelf -n ./urandom_read | grep 'Build ID'", "r");
> - if (fp == NULL)
> - return -1;
> -
> - if (getline(&line, &len, fp) == -1)
> - goto err;
> - pclose(fp);
> -
> - if (len > size)
> - len = size;
> - memcpy(build_id, line, len);
> - build_id[len] = '\0';
> - free(line);
> - return 0;
> -err:
> - pclose(fp);
> - return -1;
> -}
> -
> static int finit_module(int fd, const char *param_values, int flags)
> {
> return syscall(__NR_finit_module, fd, param_values, flags);
> diff --git a/tools/testing/selftests/bpf/test_progs.h b/tools/testing/selftests/bpf/test_progs.h
> index 9fbdc57c5b57..3825c2797a4b 100644
> --- a/tools/testing/selftests/bpf/test_progs.h
> +++ b/tools/testing/selftests/bpf/test_progs.h
> @@ -404,7 +404,6 @@ static inline void *u64_to_ptr(__u64 ptr)
> int bpf_find_map(const char *test, struct bpf_object *obj, const char *name);
> int compare_map_keys(int map1_fd, int map2_fd);
> int compare_stack_ips(int smap_fd, int amap_fd, int stack_trace_len);
> -int extract_build_id(char *build_id, size_t size);
> int kern_sync_rcu(void);
> int trigger_module_test_read(int read_sz);
> int trigger_module_test_write(int write_sz);
> --
> 2.39.2
>