* [PATCH] perf: write bpf_prog (infos|btfs)_cnt to data file
@ 2025-11-07 17:31 Thomas Falcon
2025-11-11 22:07 ` Ian Rogers
2025-11-11 22:38 ` Namhyung Kim
0 siblings, 2 replies; 5+ messages in thread
From: Thomas Falcon @ 2025-11-07 17:31 UTC (permalink / raw)
To: Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo,
Namhyung Kim, Mark Rutland, Alexander Shishkin, Jiri Olsa,
Ian Rogers, Adrian Hunter
Cc: linux-perf-users, linux-kernel, Thomas Falcon
With commit f0d0f978f3f58 ("perf header: Don't write empty BPF/BTF
info"), the write_bpf_( prog_info() | btf() ) functions exit
without writing anything if env->bpf_prog.(infos| btfs)_cnt is zero.
process_bpf_( prog_info() | btf() ), however, still expect a "count"
value to exist in the data file. If btf information is empty, for
example, process_bpf_btf will read garbage or some other data as the
number of btf nodes in the data file. As a result, the data file will
not be processed correctly.
Instead, write the count to the data file and exit if it is zero.
Fixes: f0d0f978f3f58 ("perf header: Don't write empty BPF/BTF info")
Signed-off-by: Thomas Falcon <thomas.falcon@intel.com>
---
| 10 ++--------
1 file changed, 2 insertions(+), 8 deletions(-)
--git a/tools/perf/util/header.c b/tools/perf/util/header.c
index db2ad19fa50d..54968881481c 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -1022,12 +1022,9 @@ static int write_bpf_prog_info(struct feat_fd *ff,
down_read(&env->bpf_progs.lock);
- if (env->bpf_progs.infos_cnt == 0)
- goto out;
-
ret = do_write(ff, &env->bpf_progs.infos_cnt,
sizeof(env->bpf_progs.infos_cnt));
- if (ret < 0)
+ if (ret < 0 || env->bpf_progs.infos_cnt == 0)
goto out;
root = &env->bpf_progs.infos;
@@ -1067,13 +1064,10 @@ static int write_bpf_btf(struct feat_fd *ff,
down_read(&env->bpf_progs.lock);
- if (env->bpf_progs.btfs_cnt == 0)
- goto out;
-
ret = do_write(ff, &env->bpf_progs.btfs_cnt,
sizeof(env->bpf_progs.btfs_cnt));
- if (ret < 0)
+ if (ret < 0 || env->bpf_progs.btfs_cnt == 0)
goto out;
root = &env->bpf_progs.btfs;
--
2.47.3
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] perf: write bpf_prog (infos|btfs)_cnt to data file
2025-11-07 17:31 [PATCH] perf: write bpf_prog (infos|btfs)_cnt to data file Thomas Falcon
@ 2025-11-11 22:07 ` Ian Rogers
2025-11-11 22:38 ` Namhyung Kim
1 sibling, 0 replies; 5+ messages in thread
From: Ian Rogers @ 2025-11-11 22:07 UTC (permalink / raw)
To: Thomas Falcon
Cc: Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo,
Namhyung Kim, Mark Rutland, Alexander Shishkin, Jiri Olsa,
Adrian Hunter, linux-perf-users, linux-kernel
On Fri, Nov 7, 2025 at 9:32 AM Thomas Falcon <thomas.falcon@intel.com> wrote:
>
> With commit f0d0f978f3f58 ("perf header: Don't write empty BPF/BTF
> info"), the write_bpf_( prog_info() | btf() ) functions exit
> without writing anything if env->bpf_prog.(infos| btfs)_cnt is zero.
>
> process_bpf_( prog_info() | btf() ), however, still expect a "count"
> value to exist in the data file. If btf information is empty, for
> example, process_bpf_btf will read garbage or some other data as the
> number of btf nodes in the data file. As a result, the data file will
> not be processed correctly.
>
> Instead, write the count to the data file and exit if it is zero.
>
> Fixes: f0d0f978f3f58 ("perf header: Don't write empty BPF/BTF info")
> Signed-off-by: Thomas Falcon <thomas.falcon@intel.com>
Reviewed-by: Ian Rogers <irogers@google.com>
Thanks!
Ian
> ---
> tools/perf/util/header.c | 10 ++--------
> 1 file changed, 2 insertions(+), 8 deletions(-)
>
> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> index db2ad19fa50d..54968881481c 100644
> --- a/tools/perf/util/header.c
> +++ b/tools/perf/util/header.c
> @@ -1022,12 +1022,9 @@ static int write_bpf_prog_info(struct feat_fd *ff,
>
> down_read(&env->bpf_progs.lock);
>
> - if (env->bpf_progs.infos_cnt == 0)
> - goto out;
> -
> ret = do_write(ff, &env->bpf_progs.infos_cnt,
> sizeof(env->bpf_progs.infos_cnt));
> - if (ret < 0)
> + if (ret < 0 || env->bpf_progs.infos_cnt == 0)
> goto out;
>
> root = &env->bpf_progs.infos;
> @@ -1067,13 +1064,10 @@ static int write_bpf_btf(struct feat_fd *ff,
>
> down_read(&env->bpf_progs.lock);
>
> - if (env->bpf_progs.btfs_cnt == 0)
> - goto out;
> -
> ret = do_write(ff, &env->bpf_progs.btfs_cnt,
> sizeof(env->bpf_progs.btfs_cnt));
>
> - if (ret < 0)
> + if (ret < 0 || env->bpf_progs.btfs_cnt == 0)
> goto out;
>
> root = &env->bpf_progs.btfs;
> --
> 2.47.3
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] perf: write bpf_prog (infos|btfs)_cnt to data file
2025-11-07 17:31 [PATCH] perf: write bpf_prog (infos|btfs)_cnt to data file Thomas Falcon
2025-11-11 22:07 ` Ian Rogers
@ 2025-11-11 22:38 ` Namhyung Kim
2025-11-13 12:52 ` Arnaldo Carvalho de Melo
1 sibling, 1 reply; 5+ messages in thread
From: Namhyung Kim @ 2025-11-11 22:38 UTC (permalink / raw)
To: Thomas Falcon, Arnaldo Carvalho de Melo
Cc: Peter Zijlstra, Ingo Molnar, Mark Rutland, Alexander Shishkin,
Jiri Olsa, Ian Rogers, Adrian Hunter, linux-perf-users,
linux-kernel
On Fri, Nov 07, 2025 at 11:31:50AM -0600, Thomas Falcon wrote:
> With commit f0d0f978f3f58 ("perf header: Don't write empty BPF/BTF
> info"), the write_bpf_( prog_info() | btf() ) functions exit
> without writing anything if env->bpf_prog.(infos| btfs)_cnt is zero.
>
> process_bpf_( prog_info() | btf() ), however, still expect a "count"
> value to exist in the data file. If btf information is empty, for
> example, process_bpf_btf will read garbage or some other data as the
> number of btf nodes in the data file. As a result, the data file will
> not be processed correctly.
>
> Instead, write the count to the data file and exit if it is zero.
Oh, I'm afraid it'd create a compatibility problem. But I think this is
a right behavior and it's should be fine if it goes to the stable soon.
Arnaldo, can you please take this into perf-tools tree for v6.18?
Thanks,
Namhyung
>
> Fixes: f0d0f978f3f58 ("perf header: Don't write empty BPF/BTF info")
> Signed-off-by: Thomas Falcon <thomas.falcon@intel.com>
> ---
> tools/perf/util/header.c | 10 ++--------
> 1 file changed, 2 insertions(+), 8 deletions(-)
>
> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> index db2ad19fa50d..54968881481c 100644
> --- a/tools/perf/util/header.c
> +++ b/tools/perf/util/header.c
> @@ -1022,12 +1022,9 @@ static int write_bpf_prog_info(struct feat_fd *ff,
>
> down_read(&env->bpf_progs.lock);
>
> - if (env->bpf_progs.infos_cnt == 0)
> - goto out;
> -
> ret = do_write(ff, &env->bpf_progs.infos_cnt,
> sizeof(env->bpf_progs.infos_cnt));
> - if (ret < 0)
> + if (ret < 0 || env->bpf_progs.infos_cnt == 0)
> goto out;
>
> root = &env->bpf_progs.infos;
> @@ -1067,13 +1064,10 @@ static int write_bpf_btf(struct feat_fd *ff,
>
> down_read(&env->bpf_progs.lock);
>
> - if (env->bpf_progs.btfs_cnt == 0)
> - goto out;
> -
> ret = do_write(ff, &env->bpf_progs.btfs_cnt,
> sizeof(env->bpf_progs.btfs_cnt));
>
> - if (ret < 0)
> + if (ret < 0 || env->bpf_progs.btfs_cnt == 0)
> goto out;
>
> root = &env->bpf_progs.btfs;
> --
> 2.47.3
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] perf: write bpf_prog (infos|btfs)_cnt to data file
2025-11-11 22:38 ` Namhyung Kim
@ 2025-11-13 12:52 ` Arnaldo Carvalho de Melo
2025-11-14 7:21 ` Namhyung Kim
0 siblings, 1 reply; 5+ messages in thread
From: Arnaldo Carvalho de Melo @ 2025-11-13 12:52 UTC (permalink / raw)
To: Namhyung Kim
Cc: Thomas Falcon, Peter Zijlstra, Ingo Molnar, Mark Rutland,
Alexander Shishkin, Jiri Olsa, Ian Rogers, Adrian Hunter,
linux-perf-users, linux-kernel
On Tue, Nov 11, 2025 at 02:38:07PM -0800, Namhyung Kim wrote:
> On Fri, Nov 07, 2025 at 11:31:50AM -0600, Thomas Falcon wrote:
> > With commit f0d0f978f3f58 ("perf header: Don't write empty BPF/BTF
> > info"), the write_bpf_( prog_info() | btf() ) functions exit
> > without writing anything if env->bpf_prog.(infos| btfs)_cnt is zero.
> >
> > process_bpf_( prog_info() | btf() ), however, still expect a "count"
> > value to exist in the data file. If btf information is empty, for
> > example, process_bpf_btf will read garbage or some other data as the
> > number of btf nodes in the data file. As a result, the data file will
> > not be processed correctly.
> >
> > Instead, write the count to the data file and exit if it is zero.
>
> Oh, I'm afraid it'd create a compatibility problem. But I think this is
> a right behavior and it's should be fine if it goes to the stable soon.
>
> Arnaldo, can you please take this into perf-tools tree for v6.18?
Ok, agreed, I'm taking your request as an Acked-by, ok?
- Arnaldo
> Thanks,
> Namhyung
>
> >
> > Fixes: f0d0f978f3f58 ("perf header: Don't write empty BPF/BTF info")
> > Signed-off-by: Thomas Falcon <thomas.falcon@intel.com>
> > ---
> > tools/perf/util/header.c | 10 ++--------
> > 1 file changed, 2 insertions(+), 8 deletions(-)
> >
> > diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> > index db2ad19fa50d..54968881481c 100644
> > --- a/tools/perf/util/header.c
> > +++ b/tools/perf/util/header.c
> > @@ -1022,12 +1022,9 @@ static int write_bpf_prog_info(struct feat_fd *ff,
> >
> > down_read(&env->bpf_progs.lock);
> >
> > - if (env->bpf_progs.infos_cnt == 0)
> > - goto out;
> > -
> > ret = do_write(ff, &env->bpf_progs.infos_cnt,
> > sizeof(env->bpf_progs.infos_cnt));
> > - if (ret < 0)
> > + if (ret < 0 || env->bpf_progs.infos_cnt == 0)
> > goto out;
> >
> > root = &env->bpf_progs.infos;
> > @@ -1067,13 +1064,10 @@ static int write_bpf_btf(struct feat_fd *ff,
> >
> > down_read(&env->bpf_progs.lock);
> >
> > - if (env->bpf_progs.btfs_cnt == 0)
> > - goto out;
> > -
> > ret = do_write(ff, &env->bpf_progs.btfs_cnt,
> > sizeof(env->bpf_progs.btfs_cnt));
> >
> > - if (ret < 0)
> > + if (ret < 0 || env->bpf_progs.btfs_cnt == 0)
> > goto out;
> >
> > root = &env->bpf_progs.btfs;
> > --
> > 2.47.3
> >
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] perf: write bpf_prog (infos|btfs)_cnt to data file
2025-11-13 12:52 ` Arnaldo Carvalho de Melo
@ 2025-11-14 7:21 ` Namhyung Kim
0 siblings, 0 replies; 5+ messages in thread
From: Namhyung Kim @ 2025-11-14 7:21 UTC (permalink / raw)
To: Arnaldo Carvalho de Melo
Cc: Thomas Falcon, Peter Zijlstra, Ingo Molnar, Mark Rutland,
Alexander Shishkin, Jiri Olsa, Ian Rogers, Adrian Hunter,
linux-perf-users, linux-kernel
On Thu, Nov 13, 2025 at 09:52:40AM -0300, Arnaldo Carvalho de Melo wrote:
> On Tue, Nov 11, 2025 at 02:38:07PM -0800, Namhyung Kim wrote:
> > On Fri, Nov 07, 2025 at 11:31:50AM -0600, Thomas Falcon wrote:
> > > With commit f0d0f978f3f58 ("perf header: Don't write empty BPF/BTF
> > > info"), the write_bpf_( prog_info() | btf() ) functions exit
> > > without writing anything if env->bpf_prog.(infos| btfs)_cnt is zero.
> > >
> > > process_bpf_( prog_info() | btf() ), however, still expect a "count"
> > > value to exist in the data file. If btf information is empty, for
> > > example, process_bpf_btf will read garbage or some other data as the
> > > number of btf nodes in the data file. As a result, the data file will
> > > not be processed correctly.
> > >
> > > Instead, write the count to the data file and exit if it is zero.
> >
> > Oh, I'm afraid it'd create a compatibility problem. But I think this is
> > a right behavior and it's should be fine if it goes to the stable soon.
> >
> > Arnaldo, can you please take this into perf-tools tree for v6.18?
>
> Ok, agreed, I'm taking your request as an Acked-by, ok?
Sure, thanks!
Namhyung
> >
> > >
> > > Fixes: f0d0f978f3f58 ("perf header: Don't write empty BPF/BTF info")
> > > Signed-off-by: Thomas Falcon <thomas.falcon@intel.com>
> > > ---
> > > tools/perf/util/header.c | 10 ++--------
> > > 1 file changed, 2 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> > > index db2ad19fa50d..54968881481c 100644
> > > --- a/tools/perf/util/header.c
> > > +++ b/tools/perf/util/header.c
> > > @@ -1022,12 +1022,9 @@ static int write_bpf_prog_info(struct feat_fd *ff,
> > >
> > > down_read(&env->bpf_progs.lock);
> > >
> > > - if (env->bpf_progs.infos_cnt == 0)
> > > - goto out;
> > > -
> > > ret = do_write(ff, &env->bpf_progs.infos_cnt,
> > > sizeof(env->bpf_progs.infos_cnt));
> > > - if (ret < 0)
> > > + if (ret < 0 || env->bpf_progs.infos_cnt == 0)
> > > goto out;
> > >
> > > root = &env->bpf_progs.infos;
> > > @@ -1067,13 +1064,10 @@ static int write_bpf_btf(struct feat_fd *ff,
> > >
> > > down_read(&env->bpf_progs.lock);
> > >
> > > - if (env->bpf_progs.btfs_cnt == 0)
> > > - goto out;
> > > -
> > > ret = do_write(ff, &env->bpf_progs.btfs_cnt,
> > > sizeof(env->bpf_progs.btfs_cnt));
> > >
> > > - if (ret < 0)
> > > + if (ret < 0 || env->bpf_progs.btfs_cnt == 0)
> > > goto out;
> > >
> > > root = &env->bpf_progs.btfs;
> > > --
> > > 2.47.3
> > >
^ permalink raw reply [flat|nested] 5+ messages in thread
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2025-11-07 17:31 [PATCH] perf: write bpf_prog (infos|btfs)_cnt to data file Thomas Falcon
2025-11-11 22:07 ` Ian Rogers
2025-11-11 22:38 ` Namhyung Kim
2025-11-13 12:52 ` Arnaldo Carvalho de Melo
2025-11-14 7:21 ` Namhyung Kim
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