[PATCH bpf-next 3/3] selftests/bpf: Add build_id_parse kfunc test

[Jiri Olsa <jolsa@kernel.org>]

Adding test for build_id_parse kfunc.

On bpf side it finds the vma of the test_progs text through
the test function pointer and reads its build id. On user
side we use readelf to get test_progs build id and compare
it with the one from bpf side.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 .../bpf/prog_tests/vma_build_id_parse.c       | 84 +++++++++++++++++++
 .../selftests/bpf/progs/vma_build_id_parse.c  | 34 ++++++++
 2 files changed, 118 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/vma_build_id_parse.c
 create mode 100644 tools/testing/selftests/bpf/progs/vma_build_id_parse.c

diff --git a/tools/testing/selftests/bpf/prog_tests/vma_build_id_parse.c b/tools/testing/selftests/bpf/prog_tests/vma_build_id_parse.c
new file mode 100644
index 000000000000..21c6f7771251
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/vma_build_id_parse.c
@@ -0,0 +1,84 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include "vma_build_id_parse.skel.h"
+
+static int read_buildid(char **build_id)
+{
+	char tmp[] = "/tmp/dataXXXXXX";
+	char buf[200];
+	int err, fd;
+	FILE *f;
+
+	fd = mkstemp(tmp);
+	if (fd == -1)
+		return -1;
+	close(fd);
+
+	snprintf(buf, sizeof(buf),
+		"readelf -n ./test_progs 2>/dev/null | grep 'Build ID' | awk '{print $3}' > %s",
+		tmp);
+	err = system(buf);
+	if (!ASSERT_OK(err, "system"))
+		goto out;
+
+	f = fopen(tmp, "r");
+	if (!ASSERT_OK_PTR(f, "fopen")) {
+		err = -1;
+		goto out;
+	}
+	if (fscanf(f, "%ms$*\n", build_id) != 1) {
+		*build_id = NULL;
+		err = -1;
+	}
+	fclose(f);
+out:
+	unlink(tmp);
+	return err;
+}
+
+void test_vma_build_id_parse(void)
+{
+	char bpf_build_id[BPF_BUILD_ID_SIZE*2 + 1] = {}, *build_id;
+	LIBBPF_OPTS(bpf_test_run_opts, topts);
+	struct vma_build_id_parse *skel;
+	int i, err, prog_fd, size;
+
+	skel = vma_build_id_parse__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "vma_build_id_parse__open_and_load"))
+		return;
+
+	skel->bss->target_pid = getpid();
+	skel->bss->addr = (__u64)(uintptr_t)test_vma_build_id_parse;
+
+	err = vma_build_id_parse__attach(skel);
+	if (!ASSERT_OK(err, "vma_build_id_parse__attach"))
+		goto out;
+
+	prog_fd = bpf_program__fd(skel->progs.test1);
+	err = bpf_prog_test_run_opts(prog_fd, &topts);
+	ASSERT_OK(err, "test_run");
+	ASSERT_EQ(topts.retval, 0, "test_run");
+
+	ASSERT_EQ(skel->data->find_addr_ret, 0, "find_addr_ret");
+	ASSERT_GT(skel->data->vma_build_id_parse_ret, 0, "vma_build_id_parse_ret");
+
+	if (!ASSERT_OK(read_buildid(&build_id), "read_buildid"))
+		goto out;
+
+	size = skel->data->vma_build_id_parse_ret;
+	ASSERT_EQ(size, strlen(build_id)/2, "build_id_size");
+
+	/* Convert bpf build id to string, so we can compare it. */
+	for (i = 0; i < size; i++) {
+		sprintf(bpf_build_id + i*2, "%02x",
+			(unsigned char) skel->bss->build_id[i]);
+	}
+	ASSERT_STREQ(bpf_build_id, build_id, "build_ids_match");
+
+	free(build_id);
+out:
+	vma_build_id_parse__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/vma_build_id_parse.c b/tools/testing/selftests/bpf/progs/vma_build_id_parse.c
new file mode 100644
index 000000000000..bc5bc9e1808c
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/vma_build_id_parse.c
@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+#define BPF_BUILD_ID_SIZE 20
+
+__u64 addr = 0;
+pid_t target_pid = 0;
+int find_addr_ret = -1;
+int vma_build_id_parse_ret = -1;
+
+unsigned char build_id[BPF_BUILD_ID_SIZE];
+
+static long check_vma(struct task_struct *task, struct vm_area_struct *vma,
+		      void *data)
+{
+	vma_build_id_parse_ret = bpf_vma_build_id_parse(vma, (char *) build_id);
+	return 0;
+}
+
+SEC("fentry/bpf_fentry_test1")
+int BPF_PROG(test1, int a)
+{
+	struct task_struct *task = bpf_get_current_task_btf();
+
+	if (task->pid != target_pid)
+		return 0;
+
+	find_addr_ret = bpf_find_vma(task, addr, check_vma, NULL, 0);
+	return 0;
+}
-- 
2.38.1