samples/bpf/offwaketime_user.c

Source file repositories/reference/linux-study-clean/samples/bpf/offwaketime_user.c

File Facts

System
Linux kernel
Corpus path
samples/bpf/offwaketime_user.c
Extension
.c
Size
3240 bytes
Lines
154
Domain
Support Tooling And Documentation
Bucket
samples
Inferred role
Support Tooling And Documentation: implementation source
Status
source implementation candidate

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

struct key_t {
	char waker[TASK_COMM_LEN];
	char target[TASK_COMM_LEN];
	__u32 wret;
	__u32 tret;
};

static void print_stack(struct key_t *key, __u64 count)
{
	__u64 ip[PERF_MAX_STACK_DEPTH] = {};
	static bool warned;
	int i;

	printf("%s;", key->target);
	if (bpf_map_lookup_elem(map_fd[1], &key->tret, ip) != 0) {
		printf("---;");
	} else {
		for (i = PERF_MAX_STACK_DEPTH - 1; i >= 0; i--)
			print_ksym(ip[i]);
	}
	printf("-;");
	if (bpf_map_lookup_elem(map_fd[1], &key->wret, ip) != 0) {
		printf("---;");
	} else {
		for (i = 0; i < PERF_MAX_STACK_DEPTH; i++)
			print_ksym(ip[i]);
	}
	printf(";%s %lld\n", key->waker, count);

	if ((key->tret == -EEXIST || key->wret == -EEXIST) && !warned) {
		printf("stackmap collisions seen. Consider increasing size\n");
		warned = true;
	} else if (((int)(key->tret) < 0 || (int)(key->wret) < 0)) {
		printf("err stackid %d %d\n", key->tret, key->wret);
	}
}

static void print_stacks(int fd)
{
	struct key_t key = {}, next_key;
	__u64 value;

	while (bpf_map_get_next_key(fd, &key, &next_key) == 0) {
		bpf_map_lookup_elem(fd, &next_key, &value);
		print_stack(&next_key, value);
		key = next_key;
	}
}

static void int_exit(int sig)
{
	print_stacks(map_fd[0]);
	exit(0);
}

int main(int argc, char **argv)
{
	struct bpf_object *obj = NULL;
	struct bpf_link *links[2];
	struct bpf_program *prog;
	int delay = 1, i = 0;
	char filename[256];

	if (load_kallsyms()) {
		printf("failed to process /proc/kallsyms\n");
		return 2;
	}

	snprintf(filename, sizeof(filename), "%s.bpf.o", argv[0]);
	obj = bpf_object__open_file(filename, NULL);
	if (libbpf_get_error(obj)) {
		fprintf(stderr, "ERROR: opening BPF object file failed\n");
		obj = NULL;
		goto cleanup;
	}

	/* load BPF program */
	if (bpf_object__load(obj)) {
		fprintf(stderr, "ERROR: loading BPF object file failed\n");
		goto cleanup;
	}

	map_fd[0] = bpf_object__find_map_fd_by_name(obj, "counts");
	map_fd[1] = bpf_object__find_map_fd_by_name(obj, "stackmap");
	if (map_fd[0] < 0 || map_fd[1] < 0) {
		fprintf(stderr, "ERROR: finding a map in obj file failed\n");
		goto cleanup;
	}

	signal(SIGINT, int_exit);

Annotation

Implementation Notes