[PATCH bpf-next v2] selftests/bpf: add BPF program dump in veristat

[Mykyta Yatsenko <mykyta.yatsenko5@xxxxxxxxx>]

From: Mykyta Yatsenko <yatsenko@xxxxxxxx>

This patch adds support for dumping BPF program instructions directly
from veristat.
While it is already possible to inspect BPF program dump using bpftool,
it requires multiple commands. During active development, it's common
for developers to use veristat for testing verification. Integrating
instruction dumping into veristat reduces the need to switch tools and
simplifies the workflow.
By making this information more readily accessible, this change aims
to streamline the BPF development cycle and improve usability for
developers.
This implementation leverages bpftool, by running it directly via popen
to avoid any code duplication and keep veristat simple.

Signed-off-by: Mykyta Yatsenko <yatsenko@xxxxxxxx>
---
 tools/testing/selftests/bpf/veristat.c | 43 +++++++++++++++++++++++++-
 1 file changed, 42 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/veristat.c b/tools/testing/selftests/bpf/veristat.c
index d532dd82a3a8..3ba06f532bfa 100644
--- a/tools/testing/selftests/bpf/veristat.c
+++ b/tools/testing/selftests/bpf/veristat.c
@@ -181,6 +181,12 @@ struct var_preset {
 	bool applied;
 };
 
+enum dump_mode {
+	NO_DUMP = 0,
+	XLATED,
+	JITED,
+};
+
 static struct env {
 	char **filenames;
 	int filename_cnt;
@@ -227,6 +233,7 @@ static struct env {
 	char orig_cgroup[PATH_MAX];
 	char stat_cgroup[PATH_MAX];
 	int memory_peak_fd;
+	enum dump_mode dump_mode;
 } env;
 
 static int libbpf_print_fn(enum libbpf_print_level level, const char *format, va_list args)
@@ -295,6 +302,7 @@ static const struct argp_option opts[] = {
 	  "Force BPF verifier failure on register invariant violation (BPF_F_TEST_REG_INVARIANTS program flag)" },
 	{ "top-src-lines", 'S', "N", 0, "Emit N most frequent source code lines" },
 	{ "set-global-vars", 'G', "GLOBAL", 0, "Set global variables provided in the expression, for example \"var1 = 1\"" },
+	{ "dump", 'p', "DUMP", 0, "Print BPF program dump" },
 	{},
 };
 
@@ -427,6 +435,16 @@ static error_t parse_arg(int key, char *arg, struct argp_state *state)
 			return err;
 		}
 		break;
+	case 'p':
+		if (strcmp(arg, "jited") == 0) {
+			env.dump_mode = JITED;
+		} else if (strcmp(arg, "xlated") == 0) {
+			env.dump_mode = XLATED;
+		} else {
+			fprintf(stderr, "Unrecognized dump mode '%s'\n", arg);
+			return -EINVAL;
+		}
+		break;
 	default:
 		return ARGP_ERR_UNKNOWN;
 	}
@@ -1554,6 +1572,26 @@ static int parse_rvalue(const char *val, struct rvalue *rvalue)
 	return 0;
 }
 
+static void dump(int prog_fd)
+{
+	char command[512];
+	char buf[1024];
+	FILE *fp;
+
+	snprintf(command, sizeof(command), "bpftool prog dump %s id %d",
+		 env.dump_mode == JITED ? "jited" : "xlated", prog_fd);
+	fp = popen(command, "r");
+	if (!fp) {
+		fprintf(stderr, "Can't run bpftool\n");
+		return;
+	}
+
+	while (fgets(buf, sizeof(buf), fp))
+		printf("%s", buf);
+
+	pclose(fp);
+}
+
 static int process_prog(const char *filename, struct bpf_object *obj, struct bpf_program *prog)
 {
 	const char *base_filename = basename(strdupa(filename));
@@ -1630,8 +1668,11 @@ static int process_prog(const char *filename, struct bpf_object *obj, struct bpf
 
 	memset(&info, 0, info_len);
 	fd = bpf_program__fd(prog);
-	if (fd > 0 && bpf_prog_get_info_by_fd(fd, &info, &info_len) == 0)
+	if (fd > 0 && bpf_prog_get_info_by_fd(fd, &info, &info_len) == 0) {
 		stats->stats[JITED_SIZE] = info.jited_prog_len;
+		if (env.dump_mode != NO_DUMP)
+			dump(info.id);
+	}
 
 	parse_verif_log(buf, buf_sz, stats);
 
-- 
2.50.1