On Wed, Dec 22, 2021 at 5:44 AM Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
>
> On Tue, Dec 21, 2021 at 01:58:14PM -0800, Andrii Nakryiko wrote:
> > On Tue, Dec 21, 2021 at 12:23 AM Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
> > >
> > > On Thu, Dec 16, 2021 at 02:21:08PM -0800, Christy Lee wrote:
> > > > bpf__object_next is deprecated, track bpf_objects directly in
> > > > perf instead.
> > > >
> > > > Signed-off-by: Christy Lee <christylee@xxxxxx>
> > > > Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> > > > ---
> > > > tools/perf/util/bpf-loader.c | 72 +++++++++++++++++++++++++++---------
> > > > tools/perf/util/bpf-loader.h | 1 +
> > > > 2 files changed, 55 insertions(+), 18 deletions(-)
> > > >
> > > > diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
> > > > index 528aeb0ab79d..9e3988fd719a 100644
> > > > --- a/tools/perf/util/bpf-loader.c
> > > > +++ b/tools/perf/util/bpf-loader.c
> > > > @@ -29,9 +29,6 @@
> > > >
> > > > #include <internal/xyarray.h>
> > > >
> > > > -/* temporarily disable libbpf deprecation warnings */
> > > > -#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
> > > > -
> > > > static int libbpf_perf_print(enum libbpf_print_level level __attribute__((unused)),
> > > > const char *fmt, va_list args)
> > > > {
> > > > @@ -49,6 +46,36 @@ struct bpf_prog_priv {
> > > > int *type_mapping;
> > > > };
> > > >
> > > > +struct bpf_perf_object {
> > > > + struct bpf_object *obj;
> > > > + struct list_head list;
> > > > +};
> > > > +
> > > > +static LIST_HEAD(bpf_objects_list);
> > >
> > > hum, so this duplicates libbpf's bpf_objects_list,
> > > how do objects get on this list?
> >
> > yep, this list needs to be updated on perf side each time
> > bpf_object__open() (and any variant of open) is called.
> >
> > >
> > > could you please put more comments in changelog
> > > and share how you tested this?
> >
> > I actually have no idea how to test this as well, can you please share
> > some ideas?
> >
>
> I don't use it, I just know it's there.. that's why I asked ;-)
>
> it's possible to specify bpf program on the perf command line
> to be attached to event, like:
>
> # cat tools/perf/examples/bpf/hello.c
> #include <stdio.h>
>
> int syscall_enter(openat)(void *args)
> {
> puts("Hello, world\n");
> return 0;
> }
>
> license(GPL);
> #
> # perf trace -e openat,tools/perf/examples/bpf/hello.c cat /etc/passwd > /dev/null
> 0.016 ( ): __bpf_stdout__:Hello, world
> 0.018 ( 0.010 ms): cat/9079 openat(dfd: CWD, filename: /etc/ld.so.cache, flags: CLOEXEC) = 3
> 0.057 ( ): __bpf_stdout__:Hello, world
> 0.059 ( 0.011 ms): cat/9079 openat(dfd: CWD, filename: /lib64/libc.so.6, flags: CLOEXEC) = 3
> 0.417 ( ): __bpf_stdout__:Hello, world
> 0.419 ( 0.009 ms): cat/9079 openat(dfd: CWD, filename: /etc/passwd) = 3
> #
>
> I took that example from commit message
>
> >
> > BTW, while we are at it, Jiri, do you have any good ideas on how to
> > remove perf's usage of bpf_program__set_priv() and
> > bpf_program__set_prep() APIs in perf code base? These APIs are
> > deprecated as well, but seems like perf relies on them pretty heavily.
> > What would be the best way to stop using them?
> >
> > For set_priv(), I think it should be totally fine to maintain a
> > separate lookup hash table by `struct bpf_program *` or its name, that
> > shouldn't be hard.
>
> ok, so there's no alternative api for this one then
nope
>
> >
> > But for set_prep(), what does perf use it for? I assume for cloning
> > BPF programs, right? Anything else besides that? If it's just for
> > cloning, libbpf provides bpf_program__insns() API to get access to
> > underlying bpf_insn array, do you think it's possible to switch perf
> > to that instead?
>
> look like it's used to generate prologs for programs:
> a08357d8dc7d perf bpf: Generate prologue for BPF programs
>
> the author Wang Nan haven't touched that for some time,
> I'm cc-ing other folks that were involved.. Arnaldo? ;-)
>
> if nobody volunteers, I can check on that
thanks! I appreciate the help with moving perf away for libbpf's
obscure and deprecated APIs.
>
> jirka
>
