[PATCH bpf-next v7 4/6] selftests/bpf: Adjust veristat stack depth parsing

[Kumar Kartikeya Dwivedi <memxor@gmail.com>]

The verifier now reports instruction and stack depth statistics using
uniform "subprog <id> (<name>) <kind>" records. Subprogram 0 is classified
as main, while other records are global or static. Each record carries
insns_self, insns_total, and stack depth.

Teach veristat to parse the new records while retaining support for the
legacy one-line stack depth format used by older kernels. Skip both
instruction counts and match only through the stack value so fields can
still be appended without breaking parsing.

Increase the bounded backward scan so it can include all 256 per-subprogram
records.

Zero-initialize the legacy stack buffer because logs using the new format do
not populate it before the trailing tokenizer loop. This makes the loop see
an empty string instead of reading uninitialized data.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 tools/testing/selftests/bpf/veristat.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/bpf/veristat.c b/tools/testing/selftests/bpf/veristat.c
index c9c257784ee3..0ee4a675b938 100644
--- a/tools/testing/selftests/bpf/veristat.c
+++ b/tools/testing/selftests/bpf/veristat.c
@@ -993,13 +993,15 @@ static void free_verif_stats(struct verif_stats *stats, size_t stat_cnt)
 
 static char verif_log_buf[64 * 1024];
 
-#define MAX_PARSED_LOG_LINES 100
+/* Keep room for all 256 subprogram records and trailing statistics. */
+#define MAX_PARSED_LOG_LINES 300
 
 static int parse_verif_log(char * const buf, size_t buf_sz, struct verif_stats *s)
 {
 	const char *cur;
-	int pos, lines, sub_stack, cnt = 0;
-	char *state = NULL, *token, stack[512];
+	long sub_stack;
+	int pos, lines, cnt = 0;
+	char *state = NULL, *token, stack[512] = {};
 
 	buf[buf_sz - 1] = '\0';
 
@@ -1025,11 +1027,17 @@ static int parse_verif_log(char * const buf, size_t buf_sz, struct verif_stats *
 				&s->stats[MARK_READ_MAX_LEN]))
 			continue;
 
+		if (sscanf(cur, "stack depth max %ld", &s->stats[MAX_STACK]) == 1)
+			continue;
+		if (sscanf(cur, "subprog %*d %*s %*s insns_self %*d insns_total %*d stack %ld", &sub_stack) == 1) {
+			s->stats[STACK] += sub_stack;
+			continue;
+		}
 		if (2 == sscanf(cur, "stack depth %511s max %ld", stack, &s->stats[MAX_STACK]))
 			continue;
 	}
 	while ((token = strtok_r(cnt++ ? NULL : stack, "+", &state))) {
-		if (sscanf(token, "%d", &sub_stack) == 0)
+		if (sscanf(token, "%ld", &sub_stack) == 0)
 			break;
 		s->stats[STACK] += sub_stack;
 	}
-- 
2.53.0