From 85c894a80ac46aa177df04e0a33bcad409b7d64f Mon Sep 17 00:00:00 2001 From: Thomas Falcon Date: Fri, 7 Nov 2025 11:31:50 -0600 Subject: [PATCH] perf header: Write bpf_prog (infos|btfs)_cnt to data file With commit f0d0f978f3f5830a ("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: f0d0f978f3f5830a ("perf header: Don't write empty BPF/BTF info") Reviewed-by: Ian Rogers Signed-off-by: Thomas Falcon Acked-by: Namhyung Kim Cc: Adrian Hunter Cc: Alexander Shishkin Cc: Ingo Molnar Cc: Jiri Olsa Cc: Mark Rutland Cc: Peter Zijlstra Signed-off-by: Arnaldo Carvalho de Melo --- 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 4f2a6e10ed5cc..4e12be579140a 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