[PATCH RFC v2 bpf-next 8/9] selftests/bpf: Add inode_build_id test

Jiri Olsa
2023-02-28T09:34:21Z

The test attaches bpf program to sched_process_exec tracepoint
and gets build of executed file from bprm->file->f_inode object.

We use urandom_read as the test program and in addition we also
attach uprobe to liburandom_read.so:urandlib_read_without_sema
and retrieve and check build id of that shared library.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
.../selftests/bpf/prog_tests/inode_build_id.c | 68 +++++++++++++++++++
.../selftests/bpf/progs/inode_build_id.c | 62 +++++++++++++++++
tools/testing/selftests/bpf/test_progs.h | 10 +++
3 files changed, 140 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/inode_build_id.c
create mode 100644 tools/testing/selftests/bpf/progs/inode_build_id.c

diff --git a/tools/testing/selftests/bpf/prog_tests/inode_build_id.c b/tools/testing/selftests/bpf/prog_tests/inode_build_id.c
new file mode 100644
index 000000000000..d0add90f187d
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/inode_build_id.c
@@ -0,0 +1,68 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <unistd.h>
+#include <test_progs.h>
+#include "inode_build_id.skel.h"
+#include "trace_helpers.h"
+
+void test_inode_build_id(void)
+{
+ int go[2], err, child_pid, child_status, c = 1, sz;
+ char build_id[BPF_BUILD_ID_SIZE];
+ struct inode_build_id *skel;
+
+ skel = inode_build_id__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "inode_build_id__open_and_load"))
+ return;
+
+ if (!ASSERT_OK(pipe(go), "pipe"))
+ goto out;
+
+ child_pid = fork();
+ if (child_pid < 0)
+ goto out;
+
+ /* child */
+ if (child_pid == 0) {
+ /* wait for parent's pid update */
+ err = read(go[0], &c, 1);
+ if (!ASSERT_EQ(err, 1, "child_read_pipe"))
+ exit(err);
+
+ execle("./urandom_read", "urandom_read", NULL, NULL);
+ exit(errno);
+ }
+
+ /* parent, update child's pid and kick it */
+ skel->bss->pid = child_pid;
+
+ err = inode_build_id__attach(skel);
+ if (!ASSERT_OK(err, "inode_build_id__attach"))
+ goto out;
+
+ err = write(go[1], &c, 1);
+ if (!ASSERT_EQ(err, 1, "child_write_pipe"))
+ goto out;
+
+ /* wait for child to exit */
+ waitpid(child_pid, &child_status, 0);
+ if (!ASSERT_EQ(WEXITSTATUS(child_status), 0, "child_exit_value"))
+ goto out;
+
+ sz = read_build_id("./urandom_read", build_id);
+ if (!ASSERT_GT(sz, 0, "read_build_id"))
+ goto out;
+
+ ASSERT_EQ(skel->bss->build_id_bin_size, sz, "build_id_bin_size");
+ ASSERT_MEMEQ(skel->bss->build_id_bin, build_id, sz, "build_id_bin");
+
+ sz = read_build_id("./liburandom_read.so", build_id);
+ if (!ASSERT_GT(sz, 0, "read_build_id"))
+ goto out;
+
+ ASSERT_EQ(skel->bss->build_id_lib_size, sz, "build_id_lib_size");
+ ASSERT_MEMEQ(skel->bss->build_id_lib, build_id, sz, "build_id_lib");
+
+out:
+ inode_build_id__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/inode_build_id.c b/tools/testing/selftests/bpf/progs/inode_build_id.c
new file mode 100644
index 000000000000..eceb215b56b8
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/inode_build_id.c
@@ -0,0 +1,62 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "vmlinux.h"
+#include "err.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <linux/string.h>
+
+char _license[] SEC("license") = "GPL";
+
+int pid;
+
+u32 build_id_bin_size;
+u32 build_id_lib_size;
+
+char build_id_bin[20];
+char build_id_lib[20];
+
+static int store_build_id(struct inode *inode, char *build_id, u32 *sz)
+{
+ struct build_id *bid;
+
+ bid = inode->i_build_id;
+ if (IS_ERR_OR_NULL(bid))
+ return 0;
+ *sz = bid->sz;
+ if (bid->sz > sizeof(bid->data))
+ return 0;
+ __builtin_memcpy(build_id, bid->data, sizeof(bid->data));
+ return 0;
+}
+
+SEC("tp_btf/sched_process_exec")
+int BPF_PROG(prog, struct task_struct *p, pid_t old_pid, struct linux_binprm *bprm)
+{
+ int cur_pid = bpf_get_current_pid_tgid() >> 32;
+
+ if (pid != cur_pid)
+ return 0;
+ if (!bprm->file || !bprm->file->f_inode)
+ return 0;
+ return store_build_id(bprm->file->f_inode, build_id_bin, &build_id_bin_size);
+}
+
+static long check_vma(struct task_struct *task, struct vm_area_struct *vma,
+ void *data)
+{
+ if (!vma || !vma->vm_file || !vma->vm_file->f_inode)
+ return 0;
+ return store_build_id(vma->vm_file->f_inode, build_id_lib, &build_id_lib_size);
+}
+
+SEC("uprobe/liburandom_read.so:urandlib_read_without_sema")
+int BPF_UPROBE(urandlib_read_without_sema)
+{
+ struct task_struct *task = bpf_get_current_task_btf();
+ int cur_pid = bpf_get_current_pid_tgid() >> 32;
+
+ if (pid != cur_pid)
+ return 0;
+ return bpf_find_vma(task, ctx->ip, check_vma, NULL, 0);
+}
diff --git a/tools/testing/selftests/bpf/test_progs.h b/tools/testing/selftests/bpf/test_progs.h
index 3825c2797a4b..8156d6d4cb3b 100644
--- a/tools/testing/selftests/bpf/test_progs.h
+++ b/tools/testing/selftests/bpf/test_progs.h
@@ -310,6 +310,16 @@ int test__join_cgroup(const char *path);
___ok; \
})

+#define ASSERT_MEMEQ(actual, expected, sz, name) ({ \
+ static int duration = 0; \
+ const char *___act = actual; \
+ const char *___exp = expected; \
+ bool ___ok = memcmp(___act, ___exp, sz) == 0; \
+ CHECK(!___ok, (name), \
+ "unexpected %s does not match\n", (name)); \
+ ___ok; \
+})
+
#define ASSERT_STRNEQ(actual, expected, len, name) ({ \
static int duration = 0; \
const char *___act = actual; \
--
2.39.2