[PATCH v5 bpf-next 3/4] selftests/bpf: Add test verifying bpf_ringbuf_reserve retval use in map ops

Dave Marchevsky
2022-10-20T16:07:37Z

Add a test_ringbuf_map_key test prog, borrowing heavily from extant
test_ringbuf.c. The program tries to use the result of
bpf_ringbuf_reserve as map_key, which was not possible before previouis
commits in this series. The test runner added to prog_tests/ringbuf.c
verifies that the program loads and does basic sanity checks to confirm
that it runs as expected.

Also, refactor test_ringbuf such that runners for existing test_ringbuf
and newly-added test_ringbuf_map_key are subtests of 'ringbuf' top-level
test.

Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
---
v4->v5: lore.kernel.org/bpf/20220923060614.4025371-2-davemarchevsky@fb.com

* Fix some nits (Andrii)
* migrating prog from fentry -> ksyscall wasn't done as lskel doesn't
support the latter. Talked to Andrii about it offlist, he's fine with it.

v3->v4: lore.kernel.org/bpf/20220922142208.3009672-2-davemarchevsky@fb.com

* Fix some nits (Yonghong)
* make subtest runner functions static
* don't goto cleanup if -EDONE check fails
* add 'workaround' to comment in test to ease future grepping
* Add Yonghong ack

v2->v3: lore.kernel.org/bpf/20220914123600.927632-2-davemarchevsky@fb.com

* Test that ring_buffer__poll returns -EDONE (Alexei)

v1->v2: lore.kernel.org/bpf/20220912101106.2765921-1-davemarchevsky@fb.com

* Actually run the program instead of just loading (Yonghong)
* Add a bpf_map_update_elem call to the test (Yonghong)
* Refactor runner such that existing test and newly-added test are
subtests of 'ringbuf' top-level test (Yonghong)
* Remove unused globals in test prog (Yonghong)

tools/testing/selftests/bpf/Makefile | 8 ++-
.../selftests/bpf/prog_tests/ringbuf.c | 66 ++++++++++++++++-
.../bpf/progs/test_ringbuf_map_key.c | 70 +++++++++++++++++++
3 files changed, 140 insertions(+), 4 deletions(-)
create mode 100644 tools/testing/selftests/bpf/progs/test_ringbuf_map_key.c

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index e6cf21fad69f..79edef1dbda4 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -359,9 +359,11 @@ LINKED_SKELS := test_static_linked.skel.h linked_funcs.skel.h \
test_subskeleton.skel.h test_subskeleton_lib.skel.h \
test_usdt.skel.h

-LSKELS := fentry_test.c fexit_test.c fexit_sleep.c \
- test_ringbuf.c atomics.c trace_printk.c trace_vprintk.c \
- map_ptr_kern.c core_kern.c core_kern_overflow.c
+LSKELS := fentry_test.c fexit_test.c fexit_sleep.c atomics.c \
+ trace_printk.c trace_vprintk.c map_ptr_kern.c \
+ core_kern.c core_kern_overflow.c test_ringbuf.c \
+ test_ringbuf_map_key.c
+
# Generate both light skeleton and libbpf skeleton for these
LSKELS_EXTRA := test_ksyms_module.c test_ksyms_weak.c kfunc_call_test.c \
kfunc_call_test_subprog.c
diff --git a/tools/testing/selftests/bpf/prog_tests/ringbuf.c b/tools/testing/selftests/bpf/prog_tests/ringbuf.c
index 9a80fe8a6427..ac104dc652e3 100644
--- a/tools/testing/selftests/bpf/prog_tests/ringbuf.c
+++ b/tools/testing/selftests/bpf/prog_tests/ringbuf.c
@@ -13,6 +13,7 @@
#include <linux/perf_event.h>
#include <linux/ring_buffer.h>
#include "test_ringbuf.lskel.h"
+#include "test_ringbuf_map_key.lskel.h"

#define EDONE 7777

@@ -58,6 +59,7 @@ static int process_sample(void *ctx, void *data, size_t len)
}
}

+static struct test_ringbuf_map_key_lskel *skel_map_key;
static struct test_ringbuf_lskel *skel;
static struct ring_buffer *ringbuf;

@@ -81,7 +83,7 @@ static void *poll_thread(void *input)
return (void *)(long)ring_buffer__poll(ringbuf, timeout);
}

-void test_ringbuf(void)
+static void ringbuf_subtest(void)
{
const size_t rec_sz = BPF_RINGBUF_HDR_SZ + sizeof(struct sample);
pthread_t thread;
@@ -297,3 +299,65 @@ void test_ringbuf(void)
ring_buffer__free(ringbuf);
test_ringbuf_lskel__destroy(skel);
}
+
+static int process_map_key_sample(void *ctx, void *data, size_t len)
+{
+ struct sample *s;
+ int err, val;
+
+ s = data;
+ switch (s->seq) {
+ case 1:
+ ASSERT_EQ(s->value, 42, "sample_value");
+ err = bpf_map_lookup_elem(skel_map_key->maps.hash_map.map_fd,
+ s, &val);
+ ASSERT_OK(err, "hash_map bpf_map_lookup_elem");
+ ASSERT_EQ(val, 1, "hash_map val");
+ return -EDONE;
+ default:
+ return 0;
+ }
+}
+
+static void ringbuf_map_key_subtest(void)
+{
+ int err;
+
+ skel_map_key = test_ringbuf_map_key_lskel__open();
+ if (!ASSERT_OK_PTR(skel_map_key, "test_ringbuf_map_key_lskel__open"))
+ return;
+
+ skel_map_key->maps.ringbuf.max_entries = getpagesize();
+ skel_map_key->bss->pid = getpid();
+
+ err = test_ringbuf_map_key_lskel__load(skel_map_key);
+ if (!ASSERT_OK(err, "test_ringbuf_map_key_lskel__load"))
+ goto cleanup;
+
+ ringbuf = ring_buffer__new(skel_map_key->maps.ringbuf.map_fd,
+ process_map_key_sample, NULL, NULL);
+ if (!ASSERT_OK_PTR(ringbuf, "ring_buffer__new"))
+ goto cleanup;
+
+ err = test_ringbuf_map_key_lskel__attach(skel_map_key);
+ if (!ASSERT_OK(err, "test_ringbuf_map_key_lskel__attach"))
+ goto cleanup_ringbuf;
+
+ syscall(__NR_getpgid);
+ ASSERT_EQ(skel_map_key->bss->seq, 1, "skel_map_key->bss->seq");
+ err = ring_buffer__poll(ringbuf, -1);
+ ASSERT_EQ(err, -EDONE, "ring_buffer__poll");
+
+cleanup_ringbuf:
+ ring_buffer__free(ringbuf);
+cleanup:
+ test_ringbuf_map_key_lskel__destroy(skel_map_key);
+}
+
+void test_ringbuf(void)
+{
+ if (test__start_subtest("ringbuf"))
+ ringbuf_subtest();
+ if (test__start_subtest("ringbuf_map_key"))
+ ringbuf_map_key_subtest();
+}
diff --git a/tools/testing/selftests/bpf/progs/test_ringbuf_map_key.c b/tools/testing/selftests/bpf/progs/test_ringbuf_map_key.c
new file mode 100644
index 000000000000..2760bf60d05a
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_ringbuf_map_key.c
@@ -0,0 +1,70 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+
+char _license[] SEC("license") = "GPL";
+
+struct sample {
+ int pid;
+ int seq;
+ long value;
+ char comm[16];
+};
+
+struct {
+ __uint(type, BPF_MAP_TYPE_RINGBUF);
+} ringbuf SEC(".maps");
+
+struct {
+ __uint(type, BPF_MAP_TYPE_HASH);
+ __uint(max_entries, 1000);
+ __type(key, struct sample);
+ __type(value, int);
+} hash_map SEC(".maps");
+
+/* inputs */
+int pid = 0;
+
+/* inner state */
+long seq = 0;
+
+SEC("fentry/" SYS_PREFIX "sys_getpgid")
+int test_ringbuf_mem_map_key(void *ctx)
+{
+ int cur_pid = bpf_get_current_pid_tgid() >> 32;
+ struct sample *sample, sample_copy;
+ int *lookup_val;
+
+ if (cur_pid != pid)
+ return 0;
+
+ sample = bpf_ringbuf_reserve(&ringbuf, sizeof(*sample), 0);
+ if (!sample)
+ return 0;
+
+ sample->pid = pid;
+ bpf_get_current_comm(sample->comm, sizeof(sample->comm));
+ sample->seq = ++seq;
+ sample->value = 42;
+
+ /* test using 'sample' (PTR_TO_MEM | MEM_ALLOC) as map key arg
+ */
+ lookup_val = (int *)bpf_map_lookup_elem(&hash_map, sample);
+
+ /* workaround - memcpy is necessary so that verifier doesn't
+ * complain with:
+ * verifier internal error: more than one arg with ref_obj_id R3
+ * when trying to do bpf_map_update_elem(&hash_map, sample, &sample->seq, BPF_ANY);
+ *
+ * Since bpf_map_lookup_elem above uses 'sample' as key, test using
+ * sample field as value below
+ */
+ __builtin_memcpy(&sample_copy, sample, sizeof(struct sample));
+ bpf_map_update_elem(&hash_map, &sample_copy, &sample->seq, BPF_ANY);
+
+ bpf_ringbuf_submit(sample, 0);
+ return 0;
+}
--
2.30.2