selftests/bpf: Fix arg parsing in veristat, test_progs

Current code parses arguments with strtok_r() using a construct like

    char *state = NULL;
    while ((next = strtok_r(state ? NULL : input, ",", &state))) {
        ...
    }

where logic assumes the 'state' var can distinguish between first and
subsequent strtok_r() calls, and adjusts parameters accordingly. However,
'state' is strictly internal context for strtok_r() and no such assumptions
are supported in the man page. Moreover, the exact behaviour of 'state'
depends on the libc implementation, making the above code fragile.

Indeed, invoking "./test_progs -t <test_name>" on mips64el/musl will hang,
with the above code in an infinite loop.

Similarly, we see strange behaviour running 'veristat' on mips64el/musl:

    $ ./veristat -e file,prog,verdict,insns -C two-ok add-failure
    Can't specify more than 9 stats

Rewrite code using a counter to distinguish between strtok_r() calls.

Fixes: 61ddff37 ("selftests/bpf: Improve by-name subtest selection logic in prog_tests")
Fixes: 394169b0 ("selftests/bpf: add comparison mode to veristat")
Fixes: c8bc5e05 ("selftests/bpf: Add veristat tool for mass-verifying BPF object files")
Signed-off-by: Tony Ambardar <tony.ambardar@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/392d8bf5559f85fa37926c1494e62312ef252c3d.1722244708.git.tony.ambardar@gmail.com

tools/testing/selftests/bpf/testing_helpers.c

@@ -221,13 +221,13 @@ int parse_test_list(const char *s,
 		    bool is_glob_pattern)
 {
 	char *input, *state = NULL, *test_spec;
-	int err = 0;
+	int err = 0, cnt = 0;
 
 	input = strdup(s);
 	if (!input)
 		return -ENOMEM;
 
-	while ((test_spec = strtok_r(state ? NULL : input, ",", &state))) {
+	while ((test_spec = strtok_r(cnt++ ? NULL : input, ",", &state))) {
 		err = insert_test(set, test_spec, is_glob_pattern);
 		if (err)
 			break;

tools/testing/selftests/bpf/veristat.c

@@ -785,13 +785,13 @@ static int parse_stat(const char *stat_name, struct stat_specs *specs)
 static int parse_stats(const char *stats_str, struct stat_specs *specs)
 {
 	char *input, *state = NULL, *next;
-	int err;
+	int err, cnt = 0;
 
 	input = strdup(stats_str);
 	if (!input)
 		return -ENOMEM;
 
-	while ((next = strtok_r(state ? NULL : input, ",", &state))) {
+	while ((next = strtok_r(cnt++ ? NULL : input, ",", &state))) {
 		err = parse_stat(next, specs);
 		if (err) {
 			free(input);
@@ -1495,7 +1495,7 @@ static int parse_stats_csv(const char *filename, struct stat_specs *specs,
 	while (fgets(line, sizeof(line), f)) {
 		char *input = line, *state = NULL, *next;
 		struct verif_stats *st = NULL;
-		int col = 0;
+		int col = 0, cnt = 0;
 
 		if (!header) {
 			void *tmp;
@@ -1513,7 +1513,7 @@ static int parse_stats_csv(const char *filename, struct stat_specs *specs,
 			*stat_cntp += 1;
 		}
 
-		while ((next = strtok_r(state ? NULL : input, ",\n", &state))) {
+		while ((next = strtok_r(cnt++ ? NULL : input, ",\n", &state))) {
 			if (header) {
 				/* for the first line, set up spec stats */
 				err = parse_stat(next, specs);