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

[Jiri Olsa]

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@xxxxxxxxxx>
---
 .../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;
+
+	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);
+		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);
+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)
+{
+	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);
+	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));
+	bpf_map_update_elem(&files, &tmp_key, &tmp_data, 0);
+	return 0;
+}
-- 
2.39.1