selftests/bpf: test_progs avoid minus shell exit codes

There are a number of places in test_progs that use minus-1 as the argument
to exit(). This is confusing as a process exit status is masked to be a
number between 0 and 255 as defined in man exit(3). Thus, users will see
status 255 instead of minus-1.

This patch use positive exit code 3 instead of minus-1. These cases are put
in the same group of infrastructure setup errors.

Fixes: fd27b1835e70 ("selftests/bpf: Reset process and thread affinity after each test/sub-test")
Fixes: 811d7e375d08 ("bpf: selftests: Restore netns after each test")
Signed-off-by: Jesper Dangaard Brouer <[e-mail]>
Signed-off-by: Daniel Borkmann <[e-mail]>
Acked-by: Andrii Nakryiko <[e-mail]>
Link: https://lore.kernel.org/bpf/159410594499.1093222.11080787853132708654.stgit@firesoul

tools/testing/selftests/bpf/test_progs.c

···
 #include <execinfo.h> /* backtrace */
 
 #define EXIT_NO_TEST		2
+#define EXIT_ERR_SETUP_INFRA	3
 
 /* defined in test_progs.h */
 struct test_env env = {};
···
 	if (err < 0) {
 		stdio_restore();
 		fprintf(stderr, "Failed to reset process affinity: %d!\n", err);
-		exit(-1);
+		exit(EXIT_ERR_SETUP_INFRA);
 	}
 	err = pthread_setaffinity_np(pthread_self(), sizeof(cpuset), &cpuset);
 	if (err < 0) {
 		stdio_restore();
 		fprintf(stderr, "Failed to reset thread affinity: %d!\n", err);
-		exit(-1);
+		exit(EXIT_ERR_SETUP_INFRA);
 	}
 }
 
···
 	env.saved_netns_fd = open("/proc/self/ns/net", O_RDONLY);
 	if (env.saved_netns_fd == -1) {
 		perror("open(/proc/self/ns/net)");
-		exit(-1);
+		exit(EXIT_ERR_SETUP_INFRA);
 	}
 }
 
···
 	if (setns(env.saved_netns_fd, CLONE_NEWNET) == -1) {
 		stdio_restore();
 		perror("setns(CLONE_NEWNS)");
-		exit(-1);
+		exit(EXIT_ERR_SETUP_INFRA);
 	}
 }