[PATCHv4 bpf-next 4/4] selftests/bpf: Add bpf_vma_build_id_parse task vma iterator test

[Jiri Olsa <jolsa@xxxxxxxxxx>]

Adding tests for using new bpf_vma_build_id_parse kfunc in task_vma
iterator program.

On bpf program side the iterator filters test proccess and proper
vma by provided function pointer and reads its build id with the
new kfunc.

On user side the test uses readelf to get test_progs build id and
compares it with the one read from iterator.

Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
 .../selftests/bpf/prog_tests/bpf_iter.c       | 44 +++++++++++++++++++
 .../selftests/bpf/progs/bpf_iter_build_id.c   | 41 +++++++++++++++++
 2 files changed, 85 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/bpf_iter_build_id.c

diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
index 6f8ed61fc4b4..b2cad9f70b32 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
@@ -33,6 +33,9 @@
 #include "bpf_iter_bpf_link.skel.h"
 #include "bpf_iter_ksym.skel.h"
 #include "bpf_iter_sockmap.skel.h"
+#include "bpf_iter_build_id.skel.h"
+
+#define BUILDID_STR_SIZE (BPF_BUILD_ID_SIZE*2 + 1)
 
 static int duration;
 
@@ -1560,6 +1563,45 @@ static void test_task_vma_offset(void)
 	test_task_vma_offset_common(NULL, false);
 }
 
+static void test_task_vma_build_id(void)
+{
+	struct bpf_iter_build_id *skel;
+	char buf[BUILDID_STR_SIZE] = {};
+	int iter_fd, len;
+	char *build_id;
+
+	skel = bpf_iter_build_id__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "bpf_iter_vma_offset__open_and_load"))
+		return;
+
+	skel->bss->pid = getpid();
+	skel->bss->address = (uintptr_t)trigger_func;
+
+	skel->links.vma_build_id = bpf_program__attach_iter(skel->progs.vma_build_id, NULL);
+	if (!ASSERT_OK_PTR(skel->links.vma_build_id, "attach_iter"))
+		goto exit;
+
+	iter_fd = bpf_iter_create(bpf_link__fd(skel->links.vma_build_id));
+	if (!ASSERT_GT(iter_fd, 0, "create_iter"))
+		goto exit;
+
+	while ((len = read(iter_fd, buf, sizeof(buf))) > 0)
+		;
+	buf[BUILDID_STR_SIZE] = 0;
+
+	/* Read build_id via readelf to compare with iterator buf. */
+	if (!ASSERT_OK(read_self_buildid(&build_id), "read_buildid"))
+		goto exit;
+
+	ASSERT_STREQ(buf, build_id, "build_id_match");
+	ASSERT_GT(skel->data->size, 0, "size");
+
+	free(build_id);
+	close(iter_fd);
+exit:
+	bpf_iter_build_id__destroy(skel);
+}
+
 void test_bpf_iter(void)
 {
 	ASSERT_OK(pthread_mutex_init(&do_nothing_mutex, NULL), "pthread_mutex_init");
@@ -1640,4 +1682,6 @@ void test_bpf_iter(void)
 		test_bpf_sockmap_map_iter_fd();
 	if (test__start_subtest("vma_offset"))
 		test_task_vma_offset();
+	if (test__start_subtest("vma_build_id"))
+		test_task_vma_build_id();
 }
diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_build_id.c b/tools/testing/selftests/bpf/progs/bpf_iter_build_id.c
new file mode 100644
index 000000000000..86694ce6a194
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpf_iter_build_id.c
@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "bpf_iter.h"
+#include <bpf/bpf_helpers.h>
+
+#define BPF_BUILD_ID_SIZE 20
+
+extern int bpf_vma_build_id_parse(struct vm_area_struct *vma, unsigned char *build_id,
+				  size_t build_id__sz) __ksym;
+
+char _license[] SEC("license") = "GPL";
+
+uintptr_t address = 0;
+__u32 pid = 0;
+int size = -1;
+
+static unsigned char build_id[BPF_BUILD_ID_SIZE];
+
+SEC("iter/task_vma")
+int vma_build_id(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;
+	int i;
+
+	if (task == NULL || vma == NULL)
+		return 0;
+
+	if (task->tgid != pid)
+		return 0;
+
+	if (address < vma->vm_start || vma->vm_end < address)
+		return 0;
+
+	size = bpf_vma_build_id_parse(vma, build_id, sizeof(build_id));
+
+	for (i = 0; i < BPF_BUILD_ID_SIZE; i++)
+		BPF_SEQ_PRINTF(seq, "%02x", build_id[i]);
+	return 0;
+}
-- 
2.38.1