[PATCHv3 bpf-next 9/9] selftests/bpf: Add file_build_id test

From: Jiri Olsa
Date: Thu Mar 16 2023 - 13:05:00 EST

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

Also executing the no_build_id binary to verify the bpf program
gets the error properly.

Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
tools/testing/selftests/bpf/Makefile | 7 +-
tools/testing/selftests/bpf/no_build_id.c | 6 ++
.../selftests/bpf/prog_tests/file_build_id.c | 98 +++++++++++++++++++
.../selftests/bpf/progs/file_build_id.c | 70 +++++++++++++
tools/testing/selftests/bpf/test_progs.h | 10 ++
5 files changed, 190 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/bpf/no_build_id.c
create mode 100644 tools/testing/selftests/bpf/prog_tests/file_build_id.c
create mode 100644 tools/testing/selftests/bpf/progs/file_build_id.c

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 55811c448eb7..cf93a23c7962 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -88,7 +88,7 @@ TEST_GEN_PROGS_EXTENDED = test_sock_addr test_skb_cgroup_id_user \
xskxceiver xdp_redirect_multi xdp_synproxy veristat xdp_hw_metadata \
xdp_features

-TEST_CUSTOM_PROGS = $(OUTPUT)/urandom_read $(OUTPUT)/sign-file
+TEST_CUSTOM_PROGS = $(OUTPUT)/urandom_read $(OUTPUT)/sign-file $(OUTPUT)/no_build_id
TEST_GEN_FILES += liburandom_read.so

# Emit succinct information message describing current building step
@@ -201,6 +201,10 @@ $(OUTPUT)/sign-file: ../../../../scripts/sign-file.c
$< -o $@ \
$(shell $(HOSTPKG_CONFIG) --libs libcrypto 2> /dev/null || echo -lcrypto)

+$(OUTPUT)/no_build_id: no_build_id.c
+ $(call msg,BINARY,,$@)
+ $(Q)$(CC) $^ -Wl,--build-id=none -o $@
+
$(OUTPUT)/bpf_testmod.ko: $(VMLINUX_BTF) $(wildcard bpf_testmod/Makefile bpf_testmod/*.[ch])
$(call msg,MOD,,$@)
$(Q)$(RM) bpf_testmod/bpf_testmod.ko # force re-compilation
@@ -564,6 +568,7 @@ TRUNNER_EXTRA_FILES := $(OUTPUT)/urandom_read $(OUTPUT)/bpf_testmod.ko \
$(OUTPUT)/liburandom_read.so \
$(OUTPUT)/xdp_synproxy \
$(OUTPUT)/sign-file \
+ $(OUTPUT)/no_build_id \
ima_setup.sh \
verify_sig_setup.sh \
$(wildcard progs/btf_dump_test_case_*.c) \
diff --git a/tools/testing/selftests/bpf/no_build_id.c b/tools/testing/selftests/bpf/no_build_id.c
new file mode 100644
index 000000000000..a6f28f1c06d5
--- /dev/null
+++ b/tools/testing/selftests/bpf/no_build_id.c
@@ -0,0 +1,6 @@
+// SPDX-License-Identifier: GPL-2.0
+
+int main(void)
+{
+ return 0;
+}
diff --git a/tools/testing/selftests/bpf/prog_tests/file_build_id.c b/tools/testing/selftests/bpf/prog_tests/file_build_id.c
new file mode 100644
index 000000000000..cb233cfd58cb
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/file_build_id.c
@@ -0,0 +1,98 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <unistd.h>
+#include <test_progs.h>
+#include "file_build_id.skel.h"
+#include "trace_helpers.h"
+
+static void
+test_build_id(const char *bin, const char *lib, long bin_err, long lib_err)
+{
+ int err, child_pid = 0, child_status, c = 1, sz;
+ char build_id[BPF_BUILD_ID_SIZE];
+ struct file_build_id *skel;
+ int go[2] = { -1, -1 };
+
+ if (!ASSERT_OK(pipe(go), "pipe"))
+ return;
+
+ skel = file_build_id__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "file_build_id__open_and_load"))
+ goto out;
+
+ child_pid = fork();
+ if (child_pid < 0)
+ goto out;
+
+ /* child */
+ if (child_pid == 0) {
+ close(go[1]);
+ /* wait for parent's pid update */
+ err = read(go[0], &c, 1);
+ if (!ASSERT_EQ(err, 1, "child_read_pipe"))
+ exit(err);
+
+ execle(bin, bin, NULL, NULL);
+ exit(errno);
+ }
+
+ /* parent, update child's pid and kick it */
+ skel->bss->pid = child_pid;
+
+ close(go[0]);
+
+ err = file_build_id__attach(skel);
+ if (!ASSERT_OK(err, "file_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);
+ child_pid = 0;
+ if (!ASSERT_EQ(WEXITSTATUS(child_status), 0, "child_exit_value"))
+ goto out;
+
+ /* test binary */
+ sz = read_build_id(bin, build_id);
+ err = sz > 0 ? 0 : sz;
+
+ ASSERT_EQ((long) err, bin_err, "read_build_id_bin_err");
+ ASSERT_EQ(skel->bss->build_id_bin_err, bin_err, "build_id_bin_err");
+
+ if (!err) {
+ 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");
+ }
+
+ /* test library if present */
+ if (lib) {
+ sz = read_build_id(lib, build_id);
+ err = sz > 0 ? 0 : sz;
+
+ ASSERT_EQ((long) err, lib_err, "read_build_id_lib_err");
+ ASSERT_EQ(skel->bss->build_id_lib_err, lib_err, "build_id_lib_err");
+
+ if (!err) {
+ 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:
+ close(go[1]);
+ close(go[0]);
+ if (child_pid)
+ waitpid(child_pid, &child_status, 0);
+ file_build_id__destroy(skel);
+}
+
+void test_file_build_id(void)
+{
+ if (test__start_subtest("present"))
+ test_build_id("./urandom_read", "./liburandom_read.so", 0, 0);
+ if (test__start_subtest("missing"))
+ test_build_id("./no_build_id", NULL, -EINVAL, 0);
+}
diff --git a/tools/testing/selftests/bpf/progs/file_build_id.c b/tools/testing/selftests/bpf/progs/file_build_id.c
new file mode 100644
index 000000000000..6dc10c8e17ac
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/file_build_id.c
@@ -0,0 +1,70 @@
+// 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[BUILD_ID_SIZE_MAX];
+char build_id_lib[BUILD_ID_SIZE_MAX];
+
+long build_id_bin_err;
+long build_id_lib_err;
+
+static int store_build_id(struct file *file, char *build_id, u32 *sz, long *err)
+{
+ struct build_id *bid;
+
+ bid = file->f_build_id;
+ if (IS_ERR_OR_NULL(bid)) {
+ *err = PTR_ERR(bid);
+ return 0;
+ }
+ *sz = bid->sz;
+ if (bid->sz > sizeof(bid->data)) {
+ *err = 1;
+ return 0;
+ }
+ __builtin_memcpy(build_id, bid->data, sizeof(bid->data));
+ *err = 0;
+ 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)
+ return 0;
+ return store_build_id(bprm->file, build_id_bin, &build_id_bin_size, &build_id_bin_err);
+}
+
+static long check_vma(struct task_struct *task, struct vm_area_struct *vma,
+ void *data)
+{
+ if (!vma || !vma->vm_file || !vma->vm_file)
+ return 0;
+ return store_build_id(vma->vm_file, build_id_lib, &build_id_lib_size, &build_id_lib_err);
+}
+
+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 d91427bfe0d7..285dd5d91426 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