Add a testcase for the ring_buffer__consume_n() API.

The test produces multiple samples in a ring buffer, using a sys_getpid() fentry prog, and consumes them from user-space in batches, rather than consuming all of them greedily, like ring_buffer__consume() does.

Link: https://lore.kernel.org/lkml/CAEf4BzaR4zqUpDmj44KNLdpJ=Tpa97GrvzuzVNO5nM6b7o... Signed-off-by: Andrea Righi andrea.righi@canonical.com --- tools/testing/selftests/bpf/Makefile | 2 +- .../selftests/bpf/prog_tests/ringbuf.c | 65 +++++++++++++++++++ .../selftests/bpf/progs/test_ringbuf_n.c | 52 +++++++++++++++ 3 files changed, 118 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/bpf/progs/test_ringbuf_n.c

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile index edc73f8f5aef..6332277edeca 100644 --- a/tools/testing/selftests/bpf/Makefile +++ b/tools/testing/selftests/bpf/Makefile @@ -455,7 +455,7 @@ LINKED_SKELS := test_static_linked.skel.h linked_funcs.skel.h \ 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 + test_ringbuf_n.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 \ diff --git a/tools/testing/selftests/bpf/prog_tests/ringbuf.c b/tools/testing/selftests/bpf/prog_tests/ringbuf.c index 48c5695b7abf..7e085bfce9b5 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_n.lskel.h" #include "test_ringbuf_map_key.lskel.h"

#define EDONE 7777 @@ -60,6 +61,7 @@ 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_n_lskel *skel_n; static struct test_ringbuf_lskel *skel; static struct ring_buffer *ringbuf;

@@ -326,6 +328,67 @@ static void ringbuf_subtest(void) test_ringbuf_lskel__destroy(skel); }

+/* + * Test ring_buffer__consume_n() by producing N_TOT_SAMPLES samples in the ring + * buffer, via getpid(), and consuming them in chunks of N_SAMPLES. + */ +#define N_TOT_SAMPLES 32 +#define N_SAMPLES 4 + +/* Sample value to verify the callback validity */ +#define SAMPLE_VALUE 42L + +static int process_n_sample(void *ctx, void *data, size_t len) +{ + struct sample *s = data; + + CHECK(s->value != SAMPLE_VALUE, + "sample_value", "exp %ld, got %ld\n", SAMPLE_VALUE, s->value); + + return 0; +} + +static void ringbuf_n_subtest(void) +{ + int err, i; + + skel_n = test_ringbuf_n_lskel__open(); + if (!ASSERT_OK_PTR(skel_n, "test_ringbuf_n_lskel__open")) + return; + + skel_n->maps.ringbuf.max_entries = getpagesize(); + skel_n->bss->pid = getpid(); + + err = test_ringbuf_n_lskel__load(skel_n); + if (!ASSERT_OK(err, "test_ringbuf_n_lskel__load")) + goto cleanup; + + ringbuf = ring_buffer__new(skel_n->maps.ringbuf.map_fd, + process_n_sample, NULL, NULL); + if (!ASSERT_OK_PTR(ringbuf, "ring_buffer__new")) + goto cleanup; + + err = test_ringbuf_n_lskel__attach(skel_n); + if (!ASSERT_OK(err, "test_ringbuf_n_lskel__attach")) + goto cleanup_ringbuf; + + /* Produce N_TOT_SAMPLES samples in the ring buffer by calling getpid() */ + skel->bss->value = SAMPLE_VALUE; + for (i = 0; i < N_TOT_SAMPLES; i++) + syscall(__NR_getpgid); + + /* Consume all samples from the ring buffer in batches of N_SAMPLES */ + for (i = 0; i < N_TOT_SAMPLES; i += err) { + err = ring_buffer__consume_n(ringbuf, N_SAMPLES); + ASSERT_EQ(err, N_SAMPLES, "rb_consume"); + } + +cleanup_ringbuf: + ring_buffer__free(ringbuf); +cleanup: + test_ringbuf_n_lskel__destroy(skel_n); +} + static int process_map_key_sample(void *ctx, void *data, size_t len) { struct sample *s; @@ -384,6 +447,8 @@ void test_ringbuf(void) { if (test__start_subtest("ringbuf")) ringbuf_subtest(); + if (test__start_subtest("ringbuf_n")) + ringbuf_n_subtest(); if (test__start_subtest("ringbuf_map_key")) ringbuf_map_key_subtest(); } diff --git a/tools/testing/selftests/bpf/progs/test_ringbuf_n.c b/tools/testing/selftests/bpf/progs/test_ringbuf_n.c new file mode 100644 index 000000000000..b98b5bb20699 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/test_ringbuf_n.c @@ -0,0 +1,52 @@ +// SPDX-License-Identifier: GPL-2.0 +// Copyright (c) 2024 Andrea Righi andrea.righi@canonical.com + +#include <linux/bpf.h> +#include <sched.h> +#include <unistd.h> +#include <bpf/bpf_helpers.h> +#include "bpf_misc.h" + +char _license[] SEC("license") = "GPL"; + +#define TASK_COMM_LEN 16 + +struct sample { + int pid; + int seq; + long value; + char comm[16]; +}; + +struct { + __uint(type, BPF_MAP_TYPE_RINGBUF); +} ringbuf SEC(".maps"); + +int pid = 0; +long value = 0; + +/* inner state */ +long seq = 0; + +SEC("fentry/" SYS_PREFIX "sys_getpgid") +int test_ringbuf_n(void *ctx) +{ + int cur_pid = bpf_get_current_pid_tgid() >> 32; + struct sample *sample; + + if (cur_pid != pid) + return 0; + + sample = bpf_ringbuf_reserve(&ringbuf, sizeof(*sample), 0); + if (!sample) + return 0; + + sample->pid = pid; + sample->seq = seq++; + sample->value = value; + bpf_get_current_comm(sample->comm, sizeof(sample->comm)); + + bpf_ringbuf_submit(sample, 0); + + return 0; +}