Re: [PATCH RFC 5/5] selftests/bpf: Add iter_task_vma_buildid test

Andrii Nakryiko
2023-02-09T00:02:02Z

On Wed, Feb 1, 2023 at 5:58 AM Jiri Olsa <jolsa@kernel.org> wrote:
>
> Testing iterator access to build id in vma->vm_file object
> by storing each binary with buildid into map and checking
> it against buildid retrieved in user space.
>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
> .../selftests/bpf/prog_tests/bpf_iter.c | 88 +++++++++++++++++++
> .../bpf/progs/bpf_iter_task_vma_buildid.c | 49 +++++++++++
> 2 files changed, 137 insertions(+)
> create mode 100644 tools/testing/selftests/bpf/progs/bpf_iter_task_vma_buildid.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
> index 3af6450763e9..fd3217b68c2e 100644
> --- a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
> +++ b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
> @@ -33,6 +33,7 @@
> #include "bpf_iter_bpf_link.skel.h"
> #include "bpf_iter_ksym.skel.h"
> #include "bpf_iter_sockmap.skel.h"
> +#include "bpf_iter_task_vma_buildid.skel.h"
>
> static int duration;
>
> @@ -1536,6 +1537,91 @@ static void test_task_vma_dead_task(void)
> bpf_iter_task_vma__destroy(skel);
> }
>
> +#define D_PATH_BUF_SIZE 1024
> +#define BUILD_ID_SIZE_MAX 20
> +
> +struct build_id {
> + u32 sz;
> + char data[BUILD_ID_SIZE_MAX];
> +};
> +
> +#define BUILDID_STR_SIZE (BPF_BUILD_ID_SIZE*2 + 1)
> +
> +static void test_task_vma_buildid(void)
> +{
> + int err, iter_fd = -1, proc_maps_fd = -1;
> + struct bpf_iter_task_vma_buildid *skel;
> + char key[D_PATH_BUF_SIZE], *prev_key;
> + char bpf_build_id[BUILDID_STR_SIZE];
> + int len, files_fd, i, cnt = 0;
> + struct build_id val;
> + char *build_id;
> + char c;
> +
> + skel = bpf_iter_task_vma_buildid__open();
> + if (!ASSERT_OK_PTR(skel, "bpf_iter_task_vma_buildid__open"))
> + return;
> +
> + err = bpf_iter_task_vma_buildid__load(skel);
> + if (!ASSERT_OK(err, "bpf_iter_task_vma_buildid__load"))
> + goto out;

minor: you can do __open_and_load() in one step

> +
> + skel->links.proc_maps = bpf_program__attach_iter(
> + skel->progs.proc_maps, NULL);
> +
> + if (!ASSERT_OK_PTR(skel->links.proc_maps, "bpf_program__attach_iter")) {
> + skel->links.proc_maps = NULL;
> + goto out;
> + }
> +
> + iter_fd = bpf_iter_create(bpf_link__fd(skel->links.proc_maps));
> + if (!ASSERT_GE(iter_fd, 0, "create_iter"))
> + goto out;
> +
> + /* trigger the iterator, there's no output, just map */
> + len = read(iter_fd, &c, 1);
> + ASSERT_EQ(len, 0, "len_check");
> +
> + files_fd = bpf_map__fd(skel->maps.files);
> +
> + prev_key = NULL;
> +
> + while (true) {
> + err = bpf_map_get_next_key(files_fd, prev_key, &key);
> + if (err) {
> + if (errno == ENOENT)
> + err = 0;
> + break;
> + }
> + if (bpf_map_lookup_elem(files_fd, key, &val))
> + break;
> + if (!ASSERT_LE(val.sz, BUILD_ID_SIZE_MAX, "buildid_size"))
> + break;
> +
> + memset(bpf_build_id, 0x0, sizeof(bpf_build_id));
> + for (i = 0; i < val.sz; i++) {
> + sprintf(bpf_build_id + i*2, "%02x",
> + (unsigned char) val.data[i]);
> + }
> +
> + if (!ASSERT_OK(read_buildid(key, &build_id), "read_buildid"))
> + break;
> +
> + printf("BUILDID %s %s %s\n", bpf_build_id, build_id, key);

debugging leftover or intentional?

> + ASSERT_OK(strncmp(bpf_build_id, build_id, strlen(bpf_build_id)), "buildid_cmp");
> +
> + free(build_id);
> + prev_key = key;
> + cnt++;
> + }
> +
> + printf("checked %d files\n", cnt);

ditto

> +out:
> + close(proc_maps_fd);
> + close(iter_fd);
> + bpf_iter_task_vma_buildid__destroy(skel);
> +}
> +
> void test_bpf_sockmap_map_iter_fd(void)
> {
> struct bpf_iter_sockmap *skel;
> @@ -1659,6 +1745,8 @@ void test_bpf_iter(void)
> test_task_vma();
> if (test__start_subtest("task_vma_dead_task"))
> test_task_vma_dead_task();
> + if (test__start_subtest("task_vma_buildid"))
> + test_task_vma_buildid();
> if (test__start_subtest("task_btf"))
> test_task_btf();
> if (test__start_subtest("tcp4"))
> diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_task_vma_buildid.c b/tools/testing/selftests/bpf/progs/bpf_iter_task_vma_buildid.c
> new file mode 100644
> index 000000000000..25e2179ae5f4
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/bpf_iter_task_vma_buildid.c
> @@ -0,0 +1,49 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include "bpf_iter.h"
> +#include <bpf/bpf_helpers.h>
> +#include <string.h>
> +
> +char _license[] SEC("license") = "GPL";
> +
> +#define VM_EXEC 0x00000004
> +#define D_PATH_BUF_SIZE 1024
> +
> +struct {
> + __uint(type, BPF_MAP_TYPE_HASH);
> + __uint(max_entries, 10000);
> + __type(key, char[D_PATH_BUF_SIZE]);
> + __type(value, struct build_id);
> +} files SEC(".maps");
> +
> +static char tmp_key[D_PATH_BUF_SIZE];
> +static struct build_id tmp_data;
> +
> +SEC("iter/task_vma") int proc_maps(struct bpf_iter__task_vma *ctx)

nit: let's keep SEC() on separate line from function itself

> +{
> + struct vm_area_struct *vma = ctx->vma;
> + struct seq_file *seq = ctx->meta->seq;
> + struct task_struct *task = ctx->task;
> + unsigned long file_key;
> + struct file *file;
> +
> + if (task == (void *)0 || vma == (void *)0)
> + return 0;
> +
> + if (!(vma->vm_flags & VM_EXEC))
> + return 0;
> +
> + file = vma->vm_file;
> + if (!file)
> + return 0;
> +
> + memset(tmp_key, 0x0, D_PATH_BUF_SIZE);

__builtin_memset() to not rely on compiler optimization?

> + bpf_d_path(&file->f_path, (char *) &tmp_key, D_PATH_BUF_SIZE);
> +
> + if (bpf_map_lookup_elem(&files, &tmp_key))
> + return 0;
> +
> + memcpy(&tmp_data, file->f_bid, sizeof(*file->f_bid));

same about __builtin_memcpy()

> + bpf_map_update_elem(&files, &tmp_key, &tmp_data, 0);
> + return 0;
> +}
> --
> 2.39.1
>