selftests: bpf: use __stderr in stream error tests

Start using __stderr directly in the bpf programs to test the reporting
of may_goto timeout detection and spin_lock dead lock detection.

Signed-off-by: Puranjay Mohan <[e-mail]>
Acked-by: Eduard Zingerman <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexei Starovoitov <[e-mail]>

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

···
 /* 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"
···
 {
 	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;
-}
-
-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__) && !defined(__s390x__) && !defined(__aarch64__)
-		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)

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

···
 }
 
 SEC("syscall")
+__arch_x86_64
+__arch_arm64
+__arch_s390x
 __success __retval(0)
+__stderr("ERROR: Timeout detected for may_goto instruction")
+__stderr("CPU: {{[0-9]+}} UID: 0 PID: {{[0-9]+}} Comm: {{.*}}")
+__stderr("Call trace:\n"
+"{{([a-zA-Z_][a-zA-Z0-9_]*\\+0x[0-9a-fA-F]+/0x[0-9a-fA-F]+\n"
+"|[ \t]+[^\n]+\n)*}}")
 int stream_cond_break(void *ctx)
 {
 	while (can_loop)
···
 
 SEC("syscall")
 __success __retval(0)
+__stderr("ERROR: AA or ABBA deadlock detected for bpf_res_spin_lock")
+__stderr("{{Attempted lock   = (0x[0-9a-fA-F]+)\n"
+"Total held locks = 1\n"
+"Held lock\\[ 0\\] = \\1}}")
+__stderr("...")
+__stderr("CPU: {{[0-9]+}} UID: 0 PID: {{[0-9]+}} Comm: {{.*}}")
+__stderr("Call trace:\n"
+"{{([a-zA-Z_][a-zA-Z0-9_]*\\+0x[0-9a-fA-F]+/0x[0-9a-fA-F]+\n"
+"|[ \t]+[^\n]+\n)*}}")
 int stream_deadlock(void *ctx)
 {
 	struct bpf_res_spin_lock *lock, *nlock;