[PATCH RFC v2 bpf-next 9/9] selftests/bpf: Add iter_task_vma_buildid test

Jiri Olsa
2023-02-28T09:34:37Z

Testing iterator access to build id in vma->vm_file->f_inode
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 | 78 +++++++++++++++++++
.../bpf/progs/bpf_iter_task_vma_buildid.c | 60 ++++++++++++++
2 files changed, 138 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 1f02168103dd..c7dd89e7cad0 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 +1537,81 @@ static void test_task_vma_dead_task(void)
bpf_iter_task_vma__destroy(skel);
}

+#define D_PATH_BUF_SIZE 1024
+
+struct build_id {
+ u32 sz;
+ char data[BPF_BUILD_ID_SIZE];
+};
+
+static void test_task_vma_buildid(void)
+{
+ int err, iter_fd = -1, proc_maps_fd = -1, sz;
+ struct bpf_iter_task_vma_buildid *skel;
+ char key[D_PATH_BUF_SIZE], *prev_key;
+ char build_id[BPF_BUILD_ID_SIZE];
+ int len, files_fd, cnt = 0;
+ struct build_id val;
+ char c;
+
+ skel = bpf_iter_task_vma_buildid__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "bpf_iter_task_vma_buildid__open_and_load"))
+ return;
+
+ 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, BPF_BUILD_ID_SIZE, "buildid_size"))
+ break;
+
+ sz = read_build_id(key, build_id);
+ /* If there's an error, the build id is not present or malformed, kernel
+ * should see the same result and bpf program pushed zero build id.
+ */
+ if (sz < 0) {
+ memset(build_id, 0x0, BPF_BUILD_ID_SIZE);
+ sz = BPF_BUILD_ID_SIZE;
+ }
+ ASSERT_EQ(val.sz, sz, "build_id_size");
+ ASSERT_MEMEQ(val.data, build_id, sz, "build_id_data");
+
+ prev_key = key;
+ cnt++;
+ }
+
+ printf("checked %d files\n", cnt);
+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 +1735,8 @@ 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..dc528a4783ec
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpf_iter_task_vma_buildid.c
@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "bpf_iter.h"
+#include "err.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 path[D_PATH_BUF_SIZE];
+static struct build_id build_id;
+
+SEC("iter/task_vma")
+int proc_maps(struct bpf_iter__task_vma *ctx)
+{
+ 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 inode *inode;
+ 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;
+
+ __builtin_memset(path, 0x0, D_PATH_BUF_SIZE);
+ bpf_d_path(&file->f_path, (char *) &path, D_PATH_BUF_SIZE);
+
+ if (bpf_map_lookup_elem(&files, &path))
+ return 0;
+
+ inode = file->f_inode;
+ if (IS_ERR_OR_NULL(inode->i_build_id)) {
+ /* On error return empty build id. */
+ __builtin_memset(&build_id.data, 0x0, sizeof(build_id.data));
+ build_id.sz = 20;
+ } else {
+ __builtin_memcpy(&build_id, inode->i_build_id, sizeof(*inode->i_build_id));
+ }
+
+ bpf_map_update_elem(&files, &path, &build_id, 0);
+ return 0;
+}
--
2.39.2