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Commit f6de59c1 authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Daniel Borkmann
Browse files

libbpf: add tracepoint attach API 



Allow attaching BPF programs to kernel tracepoint BPF hooks specified by
category and name.

Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
Acked-by: default avatarSong Liu <songliubraving@fb.com>
Reviewed-by: default avatarStanislav Fomichev <sdf@google.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent b2650027

tools/lib/bpf/libbpf.c

+79 −0
Original line number Diff line number Diff line
@@ -4190,6 +4190,85 @@ struct bpf_link *bpf_program__attach_uprobe(struct bpf_program *prog, 
	return link;

}



static int determine_tracepoint_id(const char *tp_category,

				   const char *tp_name)

{

	char file[PATH_MAX];

	int ret;



	ret = snprintf(file, sizeof(file),

		       "/sys/kernel/debug/tracing/events/%s/%s/id",

		       tp_category, tp_name);

	if (ret < 0)

		return -errno;

	if (ret >= sizeof(file)) {

		pr_debug("tracepoint %s/%s path is too long\n",

			 tp_category, tp_name);

		return -E2BIG;

	}

	return parse_uint_from_file(file, "%d\n");

}



static int perf_event_open_tracepoint(const char *tp_category,

				      const char *tp_name)

{

	struct perf_event_attr attr = {};

	char errmsg[STRERR_BUFSIZE];

	int tp_id, pfd, err;



	tp_id = determine_tracepoint_id(tp_category, tp_name);

	if (tp_id < 0) {

		pr_warning("failed to determine tracepoint '%s/%s' perf event ID: %s\n",

			   tp_category, tp_name,

			   libbpf_strerror_r(tp_id, errmsg, sizeof(errmsg)));

		return tp_id;

	}



	attr.type = PERF_TYPE_TRACEPOINT;

	attr.size = sizeof(attr);

	attr.config = tp_id;



	pfd = syscall(__NR_perf_event_open, &attr, -1 /* pid */, 0 /* cpu */,

		      -1 /* group_fd */, PERF_FLAG_FD_CLOEXEC);

	if (pfd < 0) {

		err = -errno;

		pr_warning("tracepoint '%s/%s' perf_event_open() failed: %s\n",

			   tp_category, tp_name,

			   libbpf_strerror_r(err, errmsg, sizeof(errmsg)));

		return err;

	}

	return pfd;

}



struct bpf_link *bpf_program__attach_tracepoint(struct bpf_program *prog,

						const char *tp_category,

						const char *tp_name)

{

	char errmsg[STRERR_BUFSIZE];

	struct bpf_link *link;

	int pfd, err;



	pfd = perf_event_open_tracepoint(tp_category, tp_name);

	if (pfd < 0) {

		pr_warning("program '%s': failed to create tracepoint '%s/%s' perf event: %s\n",

			   bpf_program__title(prog, false),

			   tp_category, tp_name,

			   libbpf_strerror_r(pfd, errmsg, sizeof(errmsg)));

		return ERR_PTR(pfd);

	}

	link = bpf_program__attach_perf_event(prog, pfd);

	if (IS_ERR(link)) {

		close(pfd);

		err = PTR_ERR(link);

		pr_warning("program '%s': failed to attach to tracepoint '%s/%s': %s\n",

			   bpf_program__title(prog, false),

			   tp_category, tp_name,

			   libbpf_strerror_r(err, errmsg, sizeof(errmsg)));

		return link;

	}

	return link;

}



enum bpf_perf_event_ret

bpf_perf_event_read_simple(void *mmap_mem, size_t mmap_size, size_t page_size,

			   void **copy_mem, size_t *copy_size,

tools/lib/bpf/libbpf.h

+4 −0
Original line number Diff line number Diff line
@@ -178,6 +178,10 @@ LIBBPF_API struct bpf_link * 
bpf_program__attach_uprobe(struct bpf_program *prog, bool retprobe,

			   pid_t pid, const char *binary_path,

			   size_t func_offset);

LIBBPF_API struct bpf_link *

bpf_program__attach_tracepoint(struct bpf_program *prog,

			       const char *tp_category,

			       const char *tp_name);



struct bpf_insn;

tools/lib/bpf/libbpf.map

+1 −0
Original line number Diff line number Diff line
@@ -171,6 +171,7 @@ LIBBPF_0.0.4 { 
		bpf_object__load_xattr;

		bpf_program__attach_kprobe;

		bpf_program__attach_perf_event;

		bpf_program__attach_tracepoint;

		bpf_program__attach_uprobe;

		btf_dump__dump_type;

		btf_dump__free;