[PATCH bpf-next v4 3/6] selftests/bpf: ksyms_btf to test typed ksyms

Hao Luo
2020-09-29T23:51:36Z

Selftests for typed ksyms. Tests two types of ksyms: one is a struct,
the other is a plain int. This tests two paths in the kernel. Struct
ksyms will be converted into PTR_TO_BTF_ID by the verifier while int
typed ksyms will be converted into PTR_TO_MEM.

Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Hao Luo <haoluo@google.com>
---
.../testing/selftests/bpf/prog_tests/ksyms.c | 38 ++++------
.../selftests/bpf/prog_tests/ksyms_btf.c | 70 +++++++++++++++++++
.../selftests/bpf/progs/test_ksyms_btf.c | 23 ++++++
tools/testing/selftests/bpf/trace_helpers.c | 27 +++++++
tools/testing/selftests/bpf/trace_helpers.h | 4 ++
5 files changed, 137 insertions(+), 25 deletions(-)
create mode 100644 tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
create mode 100644 tools/testing/selftests/bpf/progs/test_ksyms_btf.c

diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms.c b/tools/testing/selftests/bpf/prog_tests/ksyms.c
index b771804b2342..b295969b263b 100644
--- a/tools/testing/selftests/bpf/prog_tests/ksyms.c
+++ b/tools/testing/selftests/bpf/prog_tests/ksyms.c
@@ -7,40 +7,28 @@

static int duration;

-static __u64 kallsyms_find(const char *sym)
-{
- char type, name[500];
- __u64 addr, res = 0;
- FILE *f;
-
- f = fopen("/proc/kallsyms", "r");
- if (CHECK(!f, "kallsyms_fopen", "failed to open: %d\n", errno))
- return 0;
-
- while (fscanf(f, "%llx %c %499s%*[^\n]\n", &addr, &type, name) > 0) {
- if (strcmp(name, sym) == 0) {
- res = addr;
- goto out;
- }
- }
-
- CHECK(false, "not_found", "symbol %s not found\n", sym);
-out:
- fclose(f);
- return res;
-}
-
void test_ksyms(void)
{
- __u64 per_cpu_start_addr = kallsyms_find("__per_cpu_start");
- __u64 link_fops_addr = kallsyms_find("bpf_link_fops");
const char *btf_path = "/sys/kernel/btf/vmlinux";
struct test_ksyms *skel;
struct test_ksyms__data *data;
+ __u64 link_fops_addr, per_cpu_start_addr;
struct stat st;
__u64 btf_size;
int err;

+ err = kallsyms_find("bpf_link_fops", &link_fops_addr);
+ if (CHECK(err == -EINVAL, "kallsyms_fopen", "failed to open: %d\n", errno))
+ return;
+ if (CHECK(err == -ENOENT, "ksym_find", "symbol 'bpf_link_fops' not found\n"))
+ return;
+
+ err = kallsyms_find("__per_cpu_start", &per_cpu_start_addr);
+ if (CHECK(err == -EINVAL, "kallsyms_fopen", "failed to open: %d\n", errno))
+ return;
+ if (CHECK(err == -ENOENT, "ksym_find", "symbol 'per_cpu_start' not found\n"))
+ return;
+
if (CHECK(stat(btf_path, &st), "stat_btf", "err %d\n", errno))
return;
btf_size = st.st_size;
diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
new file mode 100644
index 000000000000..c6ef06c0629a
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
@@ -0,0 +1,70 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Google */
+
+#include <test_progs.h>
+#include <bpf/libbpf.h>
+#include <bpf/btf.h>
+#include "test_ksyms_btf.skel.h"
+
+static int duration;
+
+void test_ksyms_btf(void)
+{
+ __u64 runqueues_addr, bpf_prog_active_addr;
+ struct test_ksyms_btf *skel = NULL;
+ struct test_ksyms_btf__data *data;
+ struct btf *btf;
+ int percpu_datasec;
+ int err;
+
+ err = kallsyms_find("runqueues", &runqueues_addr);
+ if (CHECK(err == -EINVAL, "kallsyms_fopen", "failed to open: %d\n", errno))
+ return;
+ if (CHECK(err == -ENOENT, "ksym_find", "symbol 'runqueues' not found\n"))
+ return;
+
+ err = kallsyms_find("bpf_prog_active", &bpf_prog_active_addr);
+ if (CHECK(err == -EINVAL, "kallsyms_fopen", "failed to open: %d\n", errno))
+ return;
+ if (CHECK(err == -ENOENT, "ksym_find", "symbol 'bpf_prog_active' not found\n"))
+ return;
+
+ btf = libbpf_find_kernel_btf();
+ if (CHECK(IS_ERR(btf), "btf_exists", "failed to load kernel BTF: %ld\n",
+ PTR_ERR(btf)))
+ return;
+
+ percpu_datasec = btf__find_by_name_kind(btf, ".data..percpu",
+ BTF_KIND_DATASEC);
+ if (percpu_datasec < 0) {
+ printf("%s:SKIP:no PERCPU DATASEC in kernel btf\n",
+ __func__);
+ test__skip();
+ goto cleanup;
+ }
+
+ skel = test_ksyms_btf__open_and_load();
+ if (CHECK(!skel, "skel_open", "failed to open and load skeleton\n"))
+ goto cleanup;
+
+ err = test_ksyms_btf__attach(skel);
+ if (CHECK(err, "skel_attach", "skeleton attach failed: %d\n", err))
+ goto cleanup;
+
+ /* trigger tracepoint */
+ usleep(1);
+
+ data = skel->data;
+ CHECK(data->out__runqueues_addr != runqueues_addr, "runqueues_addr",
+ "got %llu, exp %llu\n",
+ (unsigned long long)data->out__runqueues_addr,
+ (unsigned long long)runqueues_addr);
+ CHECK(data->out__bpf_prog_active_addr != bpf_prog_active_addr, "bpf_prog_active_addr",
+ "got %llu, exp %llu\n",
+ (unsigned long long)data->out__bpf_prog_active_addr,
+ (unsigned long long)bpf_prog_active_addr);
+
+cleanup:
+ btf__free(btf);
+ test_ksyms_btf__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/test_ksyms_btf.c b/tools/testing/selftests/bpf/progs/test_ksyms_btf.c
new file mode 100644
index 000000000000..7dde2082131d
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_ksyms_btf.c
@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Google */
+
+#include "vmlinux.h"
+
+#include <bpf/bpf_helpers.h>
+
+__u64 out__runqueues_addr = -1;
+__u64 out__bpf_prog_active_addr = -1;
+
+extern const struct rq runqueues __ksym; /* struct type global var. */
+extern const int bpf_prog_active __ksym; /* int type global var. */
+
+SEC("raw_tp/sys_enter")
+int handler(const void *ctx)
+{
+ out__runqueues_addr = (__u64)&runqueues;
+ out__bpf_prog_active_addr = (__u64)&bpf_prog_active;
+
+ return 0;
+}
+
+char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/trace_helpers.c b/tools/testing/selftests/bpf/trace_helpers.c
index 4d0e913bbb22..1bbd1d9830c8 100644
--- a/tools/testing/selftests/bpf/trace_helpers.c
+++ b/tools/testing/selftests/bpf/trace_helpers.c
@@ -90,6 +90,33 @@ long ksym_get_addr(const char *name)
return 0;
}

+/* open kallsyms and read symbol addresses on the fly. Without caching all symbols,
+ * this is faster than load + find.
+ */
+int kallsyms_find(const char *sym, unsigned long long *addr)
+{
+ char type, name[500];
+ unsigned long long value;
+ int err = 0;
+ FILE *f;
+
+ f = fopen("/proc/kallsyms", "r");
+ if (!f)
+ return -EINVAL;
+
+ while (fscanf(f, "%llx %c %499s%*[^\n]\n", &value, &type, name) > 0) {
+ if (strcmp(name, sym) == 0) {
+ *addr = value;
+ goto out;
+ }
+ }
+ err = -ENOENT;
+
+out:
+ fclose(f);
+ return err;
+}
+
void read_trace_pipe(void)
{
int trace_fd;
diff --git a/tools/testing/selftests/bpf/trace_helpers.h b/tools/testing/selftests/bpf/trace_helpers.h
index 25ef597dd03f..f62fdef9e589 100644
--- a/tools/testing/selftests/bpf/trace_helpers.h
+++ b/tools/testing/selftests/bpf/trace_helpers.h
@@ -12,6 +12,10 @@ struct ksym {
int load_kallsyms(void);
struct ksym *ksym_search(long key);
long ksym_get_addr(const char *name);
+
+/* open kallsyms and find addresses on the fly, faster than load + search. */
+int kallsyms_find(const char *sym, unsigned long long *addr);
+
void read_trace_pipe(void);

#endif
--
2.28.0.709.gb0816b6eb0-goog