From 94a9bdbc2b35ecadc094d84844a4a30a7596807c Mon Sep 17 00:00:00 2001 From: Jin Yao Date: Wed, 5 Aug 2020 10:29:37 +0800 Subject: [PATCH] perf record: Skip side-band event setup if HAVE_LIBBPF_SUPPORT is not set [ Upstream commit 1101c872c8c7869c78dc106ae820040f36807eda ] We received an error report that perf-record caused 'Segmentation fault' on a newly system (e.g. on the new installed ubuntu). (gdb) backtrace #0 __read_once_size (size=4, res=, p=0x14) at /root/0-jinyao/acme/tools/include/linux/compiler.h:139 #1 atomic_read (v=0x14) at /root/0-jinyao/acme/tools/include/asm/../../arch/x86/include/asm/atomic.h:28 #2 refcount_read (r=0x14) at /root/0-jinyao/acme/tools/include/linux/refcount.h:65 #3 perf_mmap__read_init (map=map@entry=0x0) at mmap.c:177 #4 0x0000561ce5c0de39 in perf_evlist__poll_thread (arg=0x561ce68584d0) at util/sideband_evlist.c:62 #5 0x00007fad78491609 in start_thread (arg=) at pthread_create.c:477 #6 0x00007fad7823c103 in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95 The root cause is, evlist__add_bpf_sb_event() just returns 0 if HAVE_LIBBPF_SUPPORT is not defined (inline function path). So it will not create a valid evsel for side-band event. But perf-record still creates BPF side band thread to process the side-band event, then the error happpens. We can reproduce this issue by removing the libelf-dev. e.g. 1. apt-get remove libelf-dev 2. perf record -a -- sleep 1 root@test:~# ./perf record -a -- sleep 1 perf: Segmentation fault Obtained 6 stack frames. ./perf(+0x28eee8) [0x5562d6ef6ee8] /lib/x86_64-linux-gnu/libc.so.6(+0x46210) [0x7fbfdc65f210] ./perf(+0x342e74) [0x5562d6faae74] ./perf(+0x257e39) [0x5562d6ebfe39] /lib/x86_64-linux-gnu/libpthread.so.0(+0x9609) [0x7fbfdc990609] /lib/x86_64-linux-gnu/libc.so.6(clone+0x43) [0x7fbfdc73b103] Segmentation fault (core dumped) To fix this issue, 1. We either install the missing libraries to let HAVE_LIBBPF_SUPPORT be defined. e.g. apt-get install libelf-dev and install other related libraries. 2. Use this patch to skip the side-band event setup if HAVE_LIBBPF_SUPPORT is not set. Committer notes: The side band thread is not used just with BPF, it is also used with --switch-output-event, so narrow the ifdef to the BPF specific part. Fixes: 23cbb41c939a ("perf record: Move side band evlist setup to separate routine") Signed-off-by: Jin Yao Acked-by: Jiri Olsa Cc: Alexander Shishkin Cc: Andi Kleen Cc: Jin Yao Cc: Kan Liang Cc: Peter Zijlstra Link: http://lore.kernel.org/lkml/20200805022937.29184-1-yao.jin@linux.intel.com Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Sasha Levin --- tools/perf/builtin-record.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c index a37e7910e9e90b..23ea934f30b347 100644 --- a/tools/perf/builtin-record.c +++ b/tools/perf/builtin-record.c @@ -1489,7 +1489,7 @@ static int record__setup_sb_evlist(struct record *rec) evlist__set_cb(rec->sb_evlist, record__process_signal_event, rec); rec->thread_id = pthread_self(); } - +#ifdef HAVE_LIBBPF_SUPPORT if (!opts->no_bpf_event) { if (rec->sb_evlist == NULL) { rec->sb_evlist = evlist__new(); @@ -1505,7 +1505,7 @@ static int record__setup_sb_evlist(struct record *rec) return -1; } } - +#endif if (perf_evlist__start_sb_thread(rec->sb_evlist, &rec->opts.target)) { pr_debug("Couldn't start the BPF side band thread:\nBPF programs starting from now on won't be annotatable\n"); opts->no_bpf_event = true;