selftests/bpf: Add tests for prog streams

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 <[email protected]>

Author: kkdwivedi

tools/testing/selftests/bpf/prog_tests/stream.c

@@ -0,0 +1,112 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */
+#include <test_progs.h>
+#include <sys/mman.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",
+	},
+	{
+		offsetof(struct stream, progs.stream_deadlock),
+		"ERROR: AA or ABBA deadlock detected",
+	},
+};
+
+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[64];
+
+	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_EQ(ret, sizeof(buf), "stream read");
+		ASSERT_STRNEQ(stream_error_arr[i].errstr, buf, strlen(stream_error_arr[i].errstr),
+			      "compare error msg");
+	}
+
+	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, 2, "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);
+}

tools/testing/selftests/bpf/progs/stream.c

@@ -0,0 +1,75 @@
+// 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)
+
+SEC("syscall")
+__success __retval(0)
+int stream_exhaust(void *ctx)
+{
+	bpf_repeat(BPF_MAX_LOOPS)
+		if (bpf_stream_printk(BPF_STDOUT, _STR) == -ENOSPC)
+			return 0;
+	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;
+	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";

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;
+}
+
+char _license[] SEC("license") = "GPL";