[PATCH] perf: record: Clear BPF headers if not needed

[PATCH] perf: record: Clear BPF headers if not needed

[Mayuresh Chitale]

When perf is compiled without libbpf support (e.g., passing NO_LIBELF=1)
and even if the user explicitly passes the '--no-bpf-event' flag, the file
header feature bitmask still unconditionally retains the BPF/BTF tracking
bits. As a result, write_bpf_prog_info() and write_bpf_btf() always get
called and display the error messages below:

ERROR: Trying to write bpf_prog_info without libbpf support.
ERROR: Trying to write btf data without libbpf support.

Fix this by clearing HEADER_BPF_PROG_INFO and HEADER_BPF_BTF from the
features bitmask, whenever the user passes the '--no-bpf-event' flag.

Fixes: 598de368375e ("perf header: Properly warn/print when libtraceevent/libbpf support is missing")
Signed-off-by: Mayuresh Chitale <mayuresh.chitale@oss.qualcomm.com>
---
 tools/perf/builtin-record.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index e91539055675..692ab7138d2c 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1829,6 +1829,11 @@ static void record__init_features(struct record *rec)
 	if (!record__comp_enabled(rec))
 		perf_header__clear_feat(&session->header, HEADER_COMPRESSED);
 
+	if (rec->opts.no_bpf_event) {
+		perf_header__clear_feat(&session->header, HEADER_BPF_PROG_INFO);
+		perf_header__clear_feat(&session->header, HEADER_BPF_BTF);
+	}
+
 	perf_header__clear_feat(&session->header, HEADER_STAT);
 }
 
-- 
2.43.0

Re: [PATCH] perf: record: Clear BPF headers if not needed

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The patch conditionally clears BPF header features based on `rec->opts.no_bpf_event` too early in `record__init_features()`, failing to fix the spurious error messages for default and dynamically evaluated cases when `perf` is compiled without `libbpf`.
--

commit 9515d1b27d6dcc9884718d4505a8cf399d665c9e
Author: Mayuresh Chitale <mayuresh.chitale@oss.qualcomm.com>

perf: record: Clear BPF headers if not needed

This patch clears the HEADER_BPF_PROG_INFO and HEADER_BPF_BTF bits from the
file header feature bitmask when the '--no-bpf-event' flag is passed. This
aims to prevent spurious error messages about missing libbpf support when
writing perf data.

> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index e915390556752..692ab7138d2c3 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -1829,6 +1829,11 @@ static void record__init_features(struct record *rec)
>  	if (!record__comp_enabled(rec))
>  		perf_header__clear_feat(&session->header, HEADER_COMPRESSED);
>  
> +	if (rec->opts.no_bpf_event) {
> +		perf_header__clear_feat(&session->header, HEADER_BPF_PROG_INFO);
> +		perf_header__clear_feat(&session->header, HEADER_BPF_BTF);
> +	}
> +

[Severity: Medium]
Does this conditionally clear the features too early in the initialization
process?

If the user does not explicitly pass the flag (the default case), or if the
flag is dynamically updated to true later (e.g. if updated after checking
!evlist__needs_bpf_sb_event(rec->evlist)), this condition will evaluate to
false.

Will this leave the spurious errors unresolved for default and dynamically
evaluated cases when perf is compiled without libbpf?

>  	perf_header__clear_feat(&session->header, HEADER_STAT);
>  }

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260701141347.4098670-1-mayuresh.chitale@oss.qualcomm.com?part=1