linux-kernel - [PATCH 5.8 053/186] perf top: Skip side-band event setup if HAVE_LIBBPF

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Message-Id: <20200908152244.243347192@linuxfoundation.org>
Date:   Tue,  8 Sep 2020 17:23:15 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Tiezhu Yang <yangtiezhu@...ngson.cn>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Xuefeng Li <lixuefeng@...ngson.cn>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.8 053/186] perf top: Skip side-band event setup if HAVE_LIBBPF_SUPPORT is not set

From: Tiezhu Yang <yangtiezhu@...ngson.cn>

[ Upstream commit 0c5f1acc2a14416bf30023f373558d369afdbfc8 ]

When I execute 'perf top' without HAVE_LIBBPF_SUPPORT, there exists the
following segmentation fault, skip the side-band event setup to fix it,
this is similar with commit 1101c872c8c7 ("perf record: Skip side-band
event setup if HAVE_LIBBPF_SUPPORT is not set").

  [yangtiezhu@...ux perf]$ ./perf top
  <SNIP>
  perf: Segmentation fault
  Obtained 6 stack frames.
  ./perf(sighandler_dump_stack+0x5c) [0x12011b604]
  [0xffffffc010]
  ./perf(perf_mmap__read_init+0x3e) [0x1201feeae]
  ./perf() [0x1200d715c]
  /lib64/libpthread.so.0(+0xab9c) [0xffee10ab9c]
  /lib64/libc.so.6(+0x128f4c) [0xffedc08f4c]
  Segmentation fault
  [yangtiezhu@...ux perf]$

I use git bisect to find commit b38d85ef49cf ("perf bpf: Decouple
creating the evlist from adding the SB event") is the first bad commit,
so also add the Fixes tag.

Committer testing:

First build perf explicitely disabling libbpf:

  $ make NO_LIBBPF=1 O=/tmp/build/perf -C tools/perf install-bin && perf test python

Now make sure it isn't linked:

  $ perf -vv | grep -w bpf
                   bpf: [ OFF ]  # HAVE_LIBBPF_SUPPORT
  $
  $ nm ~/bin/perf | grep libbpf
  $

And now try to run 'perf top':

  # perf top
  perf: Segmentation fault
  -------- backtrace --------
  perf[0x5bcd6d]
  /lib64/libc.so.6(+0x3ca6f)[0x7fd0f5a66a6f]
  perf(perf_mmap__read_init+0x1e)[0x5e1afe]
  perf[0x4cc468]
  /lib64/libpthread.so.0(+0x9431)[0x7fd0f645a431]
  /lib64/libc.so.6(clone+0x42)[0x7fd0f5b2b912]
  #

Applying this patch fixes the issue.

Fixes: b38d85ef49cf ("perf bpf: Decouple creating the evlist from adding the SB event")
Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
Tested-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Xuefeng Li <lixuefeng@...ngson.cn>
Link: http://lore.kernel.org/lkml/1597753837-16222-1-git-send-email-yangtiezhu@loongson.cn
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 tools/perf/builtin-top.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 13889d73f8dd5..c665d69c0651d 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -1746,6 +1746,7 @@ int cmd_top(int argc, const char **argv)
 		goto out_delete_evlist;
 	}
 
+#ifdef HAVE_LIBBPF_SUPPORT
 	if (!top.record_opts.no_bpf_event) {
 		top.sb_evlist = evlist__new();
 
@@ -1759,6 +1760,7 @@ int cmd_top(int argc, const char **argv)
 			goto out_delete_evlist;
 		}
 	}
+#endif
 
 	if (perf_evlist__start_sb_thread(top.sb_evlist, target)) {
 		pr_debug("Couldn't start the BPF side band thread:\nBPF programs starting from now on won't be annotatable\n");
-- 
2.25.1