Message ID | 20190806234201.6296-1-dxu@dxuuu.xyz |
---|---|
State | Changes Requested |
Delegated to: | BPF Maintainers |
Headers | show |
Series | Add PERF_EVENT_IOC_QUERY_KPROBE ioctl | expand |
On Tue, Aug 6, 2019 at 4:42 PM Daniel Xu <dxu@dxuuu.xyz> wrote: > > It is sometimes necessary to perform ioctl's on the underlying perf fd. > There is not currently a way to extract the fd given a bpf_link, so add a > helper for it. Missing "Signed-off-by" tag. Please run scripts/checkpatch.pl on the patches. Otherwise, looks good to me. Acked-by: Song Liu <songliubraving@fb.com> > --- > tools/lib/bpf/libbpf.c | 13 +++++++++++++ > tools/lib/bpf/libbpf.h | 1 + > tools/lib/bpf/libbpf.map | 5 +++++ > 3 files changed, 19 insertions(+) > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > index ead915aec349..8469d69448ae 100644 > --- a/tools/lib/bpf/libbpf.c > +++ b/tools/lib/bpf/libbpf.c > @@ -4004,6 +4004,19 @@ static int bpf_link__destroy_perf_event(struct bpf_link *link) > return err; > } > > +int bpf_link__get_perf_fd(struct bpf_link *link) > +{ > + struct bpf_link_fd *l = (void *)link; > + > + if (!link) > + return -1; > + > + if (link->destroy != &bpf_link__destroy_perf_event) > + return -1; > + > + return l->fd; > +} > + > struct bpf_link *bpf_program__attach_perf_event(struct bpf_program *prog, > int pfd) > { > diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h > index 8a9d462a6f6d..5391ac95e4fa 100644 > --- a/tools/lib/bpf/libbpf.h > +++ b/tools/lib/bpf/libbpf.h > @@ -168,6 +168,7 @@ LIBBPF_API void bpf_program__unload(struct bpf_program *prog); > struct bpf_link; > > LIBBPF_API int bpf_link__destroy(struct bpf_link *link); > +LIBBPF_API int bpf_link__get_perf_fd(struct bpf_link *link); > > LIBBPF_API struct bpf_link * > bpf_program__attach_perf_event(struct bpf_program *prog, int pfd); > diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map > index f9d316e873d8..0f844ce29b04 100644 > --- a/tools/lib/bpf/libbpf.map > +++ b/tools/lib/bpf/libbpf.map > @@ -184,3 +184,8 @@ LIBBPF_0.0.4 { > perf_buffer__new_raw; > perf_buffer__poll; > } LIBBPF_0.0.3; > + > +LIBBPF_0.0.5 { > + global: > + bpf_link__get_perf_fd; > +} LIBBPF_0.0.4; > -- > 2.20.1 >
On Tue, Aug 6, 2019 at 4:42 PM Daniel Xu <dxu@dxuuu.xyz> wrote: > > It is sometimes necessary to perform ioctl's on the underlying perf fd. > There is not currently a way to extract the fd given a bpf_link, so add a > helper for it. > --- So I've been going back and forth with this approach and the alternative one, and I think I'm leaning towards the alternative one still. I think it's better to have a broad "categories" of bpf_links, e.g.: - FD-based bpf_link (which is the only one we have right now): bpf_link_fd. It's not just for perf FD-based ones, raw tracepoint is not, but it's still FD-based; - for cgroup-related links (once they are added), it will be bpf_link_cg (or something along the lines); - there probably should be separate XDP-related bpf_link with device ID/name inside; - etc, whatever we'll need. Then we can have a set of casting APIs and getter APIs that extract useful information from specific type of bpf_link. We can also add direct bpf_link creation API (e.g., from known FD), for cases where it makes sense. So something like (in libbpf.h): struct bpf_link_fd; struct bpf_link_cg; /* casting APIs */ const struct bpf_link_fd *bpf_link__as_fd(const struct bpf_link *link); const struct bpf_link_cg *bpf_link__as_cg(const struct bpf_link *link); /* getters APIs */ int bpf_link_fd__fd(const struct bpf_link_fd *link); int bpf_link_cg__cgroup_fd(const struct bpf_link_cg *link); /* link factories (in addition to attach APIs) */ const struct bpf_link_fd *bpf_link__from_fd(int fd); const struct bpf_link_cg *bpf_link__from_cg(int cg_fd, /* whatever else necessary */); I think this way it becomes obvious what you can expect to get of each possible type of bpf_link and you'll have to explicitly cast to the right type. Yet we still hide implementation details, allow no-brainer bpf_link__destroy regardless of specific type of link (which probably will be a common case). Thoughts? > tools/lib/bpf/libbpf.c | 13 +++++++++++++ > tools/lib/bpf/libbpf.h | 1 + > tools/lib/bpf/libbpf.map | 5 +++++ > 3 files changed, 19 insertions(+) > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > index ead915aec349..8469d69448ae 100644 > --- a/tools/lib/bpf/libbpf.c > +++ b/tools/lib/bpf/libbpf.c > @@ -4004,6 +4004,19 @@ static int bpf_link__destroy_perf_event(struct bpf_link *link) > return err; > } > > +int bpf_link__get_perf_fd(struct bpf_link *link) this seems like a bit too specific name (and we should avoid "get" words, as we do in a bunch of other libbpf APIs for getters). Maybe just `bpf_link__fd`? This especially makes sense with a "file-based bpf_link" abstraction I proposed above. > +{ > + struct bpf_link_fd *l = (void *)link; > + > + if (!link) > + return -1; > + > + if (link->destroy != &bpf_link__destroy_perf_event) > + return -1; > + > + return l->fd; > +} > + > struct bpf_link *bpf_program__attach_perf_event(struct bpf_program *prog, > int pfd) > { > diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h > index 8a9d462a6f6d..5391ac95e4fa 100644 > --- a/tools/lib/bpf/libbpf.h > +++ b/tools/lib/bpf/libbpf.h > @@ -168,6 +168,7 @@ LIBBPF_API void bpf_program__unload(struct bpf_program *prog); > struct bpf_link; > > LIBBPF_API int bpf_link__destroy(struct bpf_link *link); > +LIBBPF_API int bpf_link__get_perf_fd(struct bpf_link *link); > > LIBBPF_API struct bpf_link * > bpf_program__attach_perf_event(struct bpf_program *prog, int pfd); > diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map > index f9d316e873d8..0f844ce29b04 100644 > --- a/tools/lib/bpf/libbpf.map > +++ b/tools/lib/bpf/libbpf.map > @@ -184,3 +184,8 @@ LIBBPF_0.0.4 { > perf_buffer__new_raw; > perf_buffer__poll; > } LIBBPF_0.0.3; > + > +LIBBPF_0.0.5 { > + global: > + bpf_link__get_perf_fd; > +} LIBBPF_0.0.4; > -- > 2.20.1 >
On Wed, Aug 7, 2019, at 11:57 AM, Andrii Nakryiko wrote: > On Tue, Aug 6, 2019 at 4:42 PM Daniel Xu <dxu@dxuuu.xyz> wrote: > > > > It is sometimes necessary to perform ioctl's on the underlying perf fd. > > There is not currently a way to extract the fd given a bpf_link, so add a > > helper for it. > > --- > > So I've been going back and forth with this approach and the > alternative one, and I think I'm leaning towards the alternative one > still. > > I think it's better to have a broad "categories" of bpf_links, e.g.: > > - FD-based bpf_link (which is the only one we have right now): > bpf_link_fd. It's not just for perf FD-based ones, raw tracepoint is > not, but it's still FD-based; > - for cgroup-related links (once they are added), it will be > bpf_link_cg (or something along the lines); > - there probably should be separate XDP-related bpf_link with device > ID/name inside; > - etc, whatever we'll need. > > Then we can have a set of casting APIs and getter APIs that extract > useful information from specific type of bpf_link. We can also add > direct bpf_link creation API (e.g., from known FD), for cases where it > makes sense. > > So something like (in libbpf.h): > > struct bpf_link_fd; > struct bpf_link_cg; > > /* casting APIs */ > const struct bpf_link_fd *bpf_link__as_fd(const struct bpf_link *link); > const struct bpf_link_cg *bpf_link__as_cg(const struct bpf_link *link); > > /* getters APIs */ > int bpf_link_fd__fd(const struct bpf_link_fd *link); > int bpf_link_cg__cgroup_fd(const struct bpf_link_cg *link); > > /* link factories (in addition to attach APIs) */ > const struct bpf_link_fd *bpf_link__from_fd(int fd); > const struct bpf_link_cg *bpf_link__from_cg(int cg_fd, /* whatever > else necessary */); > > I think this way it becomes obvious what you can expect to get of each > possible type of bpf_link and you'll have to explicitly cast to the > right type. Yet we still hide implementation details, allow no-brainer > bpf_link__destroy regardless of specific type of link (which probably > will be a common case). > > Thoughts? Makes sense to me. This would probably result in a more predictable API when new types are added. I'll make it this way in V2. > > > tools/lib/bpf/libbpf.c | 13 +++++++++++++ > > tools/lib/bpf/libbpf.h | 1 + > > tools/lib/bpf/libbpf.map | 5 +++++ > > 3 files changed, 19 insertions(+) > > > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > > index ead915aec349..8469d69448ae 100644 > > --- a/tools/lib/bpf/libbpf.c > > +++ b/tools/lib/bpf/libbpf.c > > @@ -4004,6 +4004,19 @@ static int bpf_link__destroy_perf_event(struct bpf_link *link) > > return err; > > } > > > > +int bpf_link__get_perf_fd(struct bpf_link *link) > > this seems like a bit too specific name (and we should avoid "get" > words, as we do in a bunch of other libbpf APIs for getters). Maybe > just `bpf_link__fd`? This especially makes sense with a "file-based > bpf_link" abstraction I proposed above. Ok.
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index ead915aec349..8469d69448ae 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -4004,6 +4004,19 @@ static int bpf_link__destroy_perf_event(struct bpf_link *link) return err; } +int bpf_link__get_perf_fd(struct bpf_link *link) +{ + struct bpf_link_fd *l = (void *)link; + + if (!link) + return -1; + + if (link->destroy != &bpf_link__destroy_perf_event) + return -1; + + return l->fd; +} + struct bpf_link *bpf_program__attach_perf_event(struct bpf_program *prog, int pfd) { diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index 8a9d462a6f6d..5391ac95e4fa 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -168,6 +168,7 @@ LIBBPF_API void bpf_program__unload(struct bpf_program *prog); struct bpf_link; LIBBPF_API int bpf_link__destroy(struct bpf_link *link); +LIBBPF_API int bpf_link__get_perf_fd(struct bpf_link *link); LIBBPF_API struct bpf_link * bpf_program__attach_perf_event(struct bpf_program *prog, int pfd); diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index f9d316e873d8..0f844ce29b04 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map @@ -184,3 +184,8 @@ LIBBPF_0.0.4 { perf_buffer__new_raw; perf_buffer__poll; } LIBBPF_0.0.3; + +LIBBPF_0.0.5 { + global: + bpf_link__get_perf_fd; +} LIBBPF_0.0.4;