On 6/28/19 8:49 PM, Andrii Nakryiko wrote:
> Add a wrapper utilizing bpf_link "infrastructure" to allow attaching BPF
> programs to raw tracepoints.
>
> Signed-off-by: Andrii Nakryiko <[email protected]>
> Acked-by: Song Liu <[email protected]>
> ---
> tools/lib/bpf/libbpf.c | 37 +++++++++++++++++++++++++++++++++++++
> tools/lib/bpf/libbpf.h | 3 +++
> tools/lib/bpf/libbpf.map | 1 +
> 3 files changed, 41 insertions(+)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 8ad4f915df38..f8c7a7ecb35e 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -4263,6 +4263,43 @@ struct bpf_link *bpf_program__attach_tracepoint(struct
> bpf_program *prog,
> return link;
> }
>
> +static int bpf_link__destroy_fd(struct bpf_link *link)
> +{
> + struct bpf_link_fd *l = (void *)link;
> +
> + return close(l->fd);
> +}
> +
> +struct bpf_link *bpf_program__attach_raw_tracepoint(struct bpf_program *prog,
> + const char *tp_name)
> +{
> + char errmsg[STRERR_BUFSIZE];
> + struct bpf_link_fd *link;
> + int prog_fd, pfd;
> +
> + prog_fd = bpf_program__fd(prog);
> + if (prog_fd < 0) {
> + pr_warning("program '%s': can't attach before loaded\n",
> + bpf_program__title(prog, false));
> + return ERR_PTR(-EINVAL);
> + }
> +
> + link = malloc(sizeof(*link));
> + link->link.destroy = &bpf_link__destroy_fd;
You can move the "link = malloc(...)" etc. after
bpf_raw_tracepoint_open(). That way, you do not need to free(link)
in the error case.
> +
> + pfd = bpf_raw_tracepoint_open(tp_name, prog_fd);
> + if (pfd < 0) {
> + pfd = -errno;
> + free(link);
> + pr_warning("program '%s': failed to attach to raw tracepoint
> '%s': %s\n",
> + bpf_program__title(prog, false), tp_name,
> + libbpf_strerror_r(pfd, errmsg, sizeof(errmsg)));
> + return ERR_PTR(pfd);
> + }
> + link->fd = pfd;
> + return (struct bpf_link *)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,
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index 60611f4b4e1d..f55933784f95 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -182,6 +182,9 @@ LIBBPF_API struct bpf_link *
> bpf_program__attach_tracepoint(struct bpf_program *prog,
> const char *tp_category,
> const char *tp_name);
> +LIBBPF_API struct bpf_link *
> +bpf_program__attach_raw_tracepoint(struct bpf_program *prog,
> + const char *tp_name);
>
> struct bpf_insn;
>
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index 3c618b75ef65..e6b7d4edbc93 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -171,6 +171,7 @@ LIBBPF_0.0.4 {
> bpf_object__load_xattr;
> bpf_program__attach_kprobe;
> bpf_program__attach_perf_event;
> + bpf_program__attach_raw_tracepoint;
> bpf_program__attach_tracepoint;
> bpf_program__attach_uprobe;
> btf_dump__dump_type;
>
