On Fri, Jun 28, 2019 at 12:50 PM Song Liu <liu.song.a23@xxxxxxxxx> wrote:
>
> On Thu, Jun 27, 2019 at 10:53 PM Andrii Nakryiko <andriin@xxxxxx> wrote:
> >
> > Allow attaching BPF programs to kernel tracepoint BPF hooks specified by
> > category and name.
> >
> > Signed-off-by: Andrii Nakryiko <andriin@xxxxxx>
Acked-by: Song Liu <songliubraving@xxxxxx>
> > ---
> > tools/lib/bpf/libbpf.c | 78 ++++++++++++++++++++++++++++++++++++++++
> > tools/lib/bpf/libbpf.h | 4 +++
> > tools/lib/bpf/libbpf.map | 1 +
> > 3 files changed, 83 insertions(+)
> >
> > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > index 65d2fef41003..76d1599a7d56 100644
> > --- a/tools/lib/bpf/libbpf.c
> > +++ b/tools/lib/bpf/libbpf.c
> > @@ -4229,6 +4229,84 @@ 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);
> > +}
> > +
> > +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 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;
> > + }
>
> Similar to the 4/9, I guess we can remove some duplicated pr_warning().
>
> Thanks,
> Song
>
> > + 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,
> > diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> > index bd767cc11967..60611f4b4e1d 100644
> > --- a/tools/lib/bpf/libbpf.h
> > +++ b/tools/lib/bpf/libbpf.h
> > @@ -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;
> >
> > diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> > index 57a40fb60718..3c618b75ef65 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_tracepoint;
> > bpf_program__attach_uprobe;
> > btf_dump__dump_type;
> > btf_dump__free;
> > --
> > 2.17.1
> >
