On Tue, Jul 1, 2025 at 11:17 PM Kumar Kartikeya Dwivedi
<memxor@xxxxxxxxx> wrote:
>
> Add selftests to stress test the various facets of the stream API,
> memory allocation pattern, and ensuring dumping support is tested and
> functional.
>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
> ---
> .../testing/selftests/bpf/prog_tests/stream.c | 141 ++++++++++++++++++
> tools/testing/selftests/bpf/progs/stream.c | 81 ++++++++++
> .../testing/selftests/bpf/progs/stream_fail.c | 17 +++
> 3 files changed, 239 insertions(+)
> create mode 100644 tools/testing/selftests/bpf/prog_tests/stream.c
> create mode 100644 tools/testing/selftests/bpf/progs/stream.c
> create mode 100644 tools/testing/selftests/bpf/progs/stream_fail.c
>
Reviewed-by: Emil Tsalapatis <emil@xxxxxxxxxxxxxxx>
> diff --git a/tools/testing/selftests/bpf/prog_tests/stream.c b/tools/testing/selftests/bpf/prog_tests/stream.c
> new file mode 100644
> index 000000000000..d9f0185dca61
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/stream.c
> @@ -0,0 +1,141 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */
> +#include <test_progs.h>
> +#include <sys/mman.h>
> +#include <regex.h>
> +
> +#include "stream.skel.h"
> +#include "stream_fail.skel.h"
> +
> +void test_stream_failure(void)
> +{
> + RUN_TESTS(stream_fail);
> +}
> +
> +void test_stream_success(void)
> +{
> + RUN_TESTS(stream);
> + return;
> +}
> +
> +struct {
> + int prog_off;
> + const char *errstr;
> +} stream_error_arr[] = {
> + {
> + offsetof(struct stream, progs.stream_cond_break),
> + "ERROR: Timeout detected for may_goto instruction\n"
> + "CPU: [0-9]+ UID: 0 PID: [0-9]+ Comm: .*\n"
> + "Call trace:\n"
> + "([a-zA-Z_][a-zA-Z0-9_]*\\+0x[0-9a-fA-F]+/0x[0-9a-fA-F]+\n"
> + "|[ \t]+[^\n]+\n)*",
> + },
> + {
> + offsetof(struct stream, progs.stream_deadlock),
> + "ERROR: AA or ABBA deadlock detected for bpf_res_spin_lock\n"
> + "Attempted lock = (0x[0-9a-fA-F]+)\n"
> + "Total held locks = 1\n"
> + "Held lock\\[ 0\\] = \\1\n" // Lock address must match
> + "CPU: [0-9]+ UID: 0 PID: [0-9]+ Comm: .*\n"
> + "Call trace:\n"
> + "([a-zA-Z_][a-zA-Z0-9_]*\\+0x[0-9a-fA-F]+/0x[0-9a-fA-F]+\n"
> + "|[ \t]+[^\n]+\n)*",
> + },
> +};
> +
> +static int match_regex(const char *pattern, const char *string)
> +{
> + int err, rc;
> + regex_t re;
> +
> + err = regcomp(&re, pattern, REG_EXTENDED | REG_NEWLINE);
> + if (err)
> + return -1;
> + rc = regexec(&re, string, 0, NULL, 0);
> + regfree(&re);
> + return rc == 0 ? 1 : 0;
Nit: You can just return rc and do ASSERT_TRUE(ret > 0) for the result in
test_stream_errors.
> +}
> +
> +void test_stream_errors(void)
> +{
> + LIBBPF_OPTS(bpf_test_run_opts, opts);
> + LIBBPF_OPTS(bpf_prog_stream_read_opts, ropts);
> + struct stream *skel;
> + int ret, prog_fd;
> + char buf[1024];
> +
> + skel = stream__open_and_load();
> + if (!ASSERT_OK_PTR(skel, "stream__open_and_load"))
> + return;
> +
> + for (int i = 0; i < ARRAY_SIZE(stream_error_arr); i++) {
> + struct bpf_program **prog;
> +
> + prog = (struct bpf_program **)(((char *)skel) + stream_error_arr[i].prog_off);
> + prog_fd = bpf_program__fd(*prog);
> + ret = bpf_prog_test_run_opts(prog_fd, &opts);
> + ASSERT_OK(ret, "ret");
> + ASSERT_OK(opts.retval, "retval");
> +
> +#if !defined(__x86_64__)
> + ASSERT_TRUE(1, "Timed may_goto unsupported, skip.");
> + if (i == 0) {
> + ret = bpf_prog_stream_read(prog_fd, 2, buf, sizeof(buf), &ropts);
> + ASSERT_EQ(ret, 0, "stream read");
> + continue;
> + }
> +#endif
> +
> + ret = bpf_prog_stream_read(prog_fd, BPF_STREAM_STDERR, buf, sizeof(buf), &ropts);
> + ASSERT_GT(ret, 0, "stream read");
> + ASSERT_LE(ret, 1023, "len for buf");
> + buf[ret] = '\0';
> +
> + ret = match_regex(stream_error_arr[i].errstr, buf);
> + if (!ASSERT_TRUE(ret == 1, "regex match"))
> + fprintf(stderr, "Output from stream:\n%s\n", buf);
> + }
> +
> + stream__destroy(skel);
> +}
> +
> +void test_stream_syscall(void)
> +{
> + LIBBPF_OPTS(bpf_test_run_opts, opts);
> + LIBBPF_OPTS(bpf_prog_stream_read_opts, ropts);
> + struct stream *skel;
> + int ret, prog_fd;
> + char buf[64];
> +
> + skel = stream__open_and_load();
> + if (!ASSERT_OK_PTR(skel, "stream__open_and_load"))
> + return;
> +
> + prog_fd = bpf_program__fd(skel->progs.stream_syscall);
> + ret = bpf_prog_test_run_opts(prog_fd, &opts);
> + ASSERT_OK(ret, "ret");
> + ASSERT_OK(opts.retval, "retval");
> +
> + ASSERT_LT(bpf_prog_stream_read(0, BPF_STREAM_STDOUT, buf, sizeof(buf), &ropts), 0, "error");
> + ret = -errno;
> + ASSERT_EQ(ret, -EINVAL, "bad prog_fd");
> +
> + ASSERT_LT(bpf_prog_stream_read(prog_fd, 0, buf, sizeof(buf), &ropts), 0, "error");
> + ret = -errno;
> + ASSERT_EQ(ret, -ENOENT, "bad stream id");
> +
> + ASSERT_LT(bpf_prog_stream_read(prog_fd, BPF_STREAM_STDOUT, NULL, sizeof(buf), NULL), 0, "error");
> + ret = -errno;
> + ASSERT_EQ(ret, -EFAULT, "bad stream buf");
> +
> + ret = bpf_prog_stream_read(prog_fd, BPF_STREAM_STDOUT, buf, 2, NULL);
> + ASSERT_EQ(ret, 2, "bytes");
> + ret = bpf_prog_stream_read(prog_fd, BPF_STREAM_STDOUT, buf, 2, NULL);
> + ASSERT_EQ(ret, 1, "bytes");
> + ret = bpf_prog_stream_read(prog_fd, BPF_STREAM_STDOUT, buf, 1, &ropts);
> + ASSERT_EQ(ret, 0, "no bytes stdout");
> + ret = bpf_prog_stream_read(prog_fd, BPF_STREAM_STDERR, buf, 1, &ropts);
> + ASSERT_EQ(ret, 0, "no bytes stderr");
> +
> + stream__destroy(skel);
> +}
> diff --git a/tools/testing/selftests/bpf/progs/stream.c b/tools/testing/selftests/bpf/progs/stream.c
> new file mode 100644
> index 000000000000..ae163a656082
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/stream.c
> @@ -0,0 +1,81 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */
> +#include <vmlinux.h>
> +#include <bpf/bpf_tracing.h>
> +#include <bpf/bpf_helpers.h>
> +#include "bpf_misc.h"
> +#include "bpf_experimental.h"
> +
> +struct arr_elem {
> + struct bpf_res_spin_lock lock;
> +};
> +
> +struct {
> + __uint(type, BPF_MAP_TYPE_ARRAY);
> + __uint(max_entries, 1);
> + __type(key, int);
> + __type(value, struct arr_elem);
> +} arrmap SEC(".maps");
> +
> +#define ENOSPC 28
> +#define _STR "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
> +
> +#define STREAM_STR (u64)(_STR _STR _STR _STR)
Is this unused?
> +
> +int size;
> +
> +SEC("syscall")
> +__success __retval(0)
> +int stream_exhaust(void *ctx)
> +{
> + /* Use global variable for loop convergence. */
> + size = 0;
> + bpf_repeat(BPF_MAX_LOOPS) {
> + if (bpf_stream_printk(BPF_STDOUT, _STR) == -ENOSPC && size == 99954)
> + return 0;
> + size += sizeof(_STR) - 1;
> + }
> + return 1;
> +}
> +
> +SEC("syscall")
> +__success __retval(0)
> +int stream_cond_break(void *ctx)
> +{
> + while (can_loop)
> + ;
> + return 0;
> +}
> +
> +SEC("syscall")
> +__success __retval(0)
> +int stream_deadlock(void *ctx)
> +{
> + struct bpf_res_spin_lock *lock, *nlock;
> +
> + lock = bpf_map_lookup_elem(&arrmap, &(int){0});
> + if (!lock)
> + return 0;
Nit: Maybe change the unexpected failure paths to non-zero?
If they are followed then the test stderr output will fail the regex
in userspace, but still it would be nice to immediately be able
to see which step broke.
> + nlock = bpf_map_lookup_elem(&arrmap, &(int){0});
> + if (!nlock)
> + return 0;
> + if (bpf_res_spin_lock(lock))
> + return 0;
> + if (bpf_res_spin_lock(nlock)) {
> + bpf_res_spin_unlock(lock);
> + return 0;
> + }
> + bpf_res_spin_unlock(nlock);
> + bpf_res_spin_unlock(lock);
> + return 0;
> +}
> +
> +SEC("syscall")
> +__success __retval(0)
> +int stream_syscall(void *ctx)
> +{
> + bpf_stream_printk(BPF_STDOUT, "foo");
> + return 0;
> +}
> +
> +char _license[] SEC("license") = "GPL";
> diff --git a/tools/testing/selftests/bpf/progs/stream_fail.c b/tools/testing/selftests/bpf/progs/stream_fail.c
> new file mode 100644
> index 000000000000..12004d5092b7
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/stream_fail.c
> @@ -0,0 +1,17 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */
> +#include <vmlinux.h>
> +#include <bpf/bpf_tracing.h>
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_core_read.h>
> +#include "bpf_misc.h"
> +
> +SEC("syscall")
> +__failure __msg("Possibly NULL pointer passed")
> +int stream_vprintk_null_arg(void *ctx)
> +{
> + bpf_stream_vprintk(BPF_STDOUT, "", NULL, 0, NULL);
> + return 0;
> +}
> +
Possibly add a test passing a random scalar as the pointer? Though if the
test above succeeds, the verifier properly identifies the argument as a pointer
arg so it wouldn't give any extra signal.
> +char _license[] SEC("license") = "GPL";
> --
> 2.47.1
>
