| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <2c992bfb-8ffd-2e35-c9a2-a961de5e958d@linux.intel.com>
Date: Mon, 10 Aug 2020 08:35:00 +0800
From: "Jin, Yao" <yao.jin@...ux.intel.com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Jiri Olsa <jolsa@...hat.com>, jolsa@...nel.org,
peterz@...radead.org, mingo@...hat.com,
alexander.shishkin@...ux.intel.com, Linux-kernel@...r.kernel.org,
ak@...ux.intel.com, kan.liang@...el.com, yao.jin@...el.com
Subject: Re: [PATCH] perf record: Skip side-band event setup if
HAVE_LIBBPF_SUPPORT is not set
Hi Arnaldo,
On 8/7/2020 8:28 PM, Arnaldo Carvalho de Melo wrote:
> Em Fri, Aug 07, 2020 at 09:16:29AM -0300, Arnaldo Carvalho de Melo escreveu:
>> Em Fri, Aug 07, 2020 at 09:09:56AM -0300, Arnaldo Carvalho de Melo escreveu:
>>> Em Fri, Aug 07, 2020 at 09:08:24AM -0300, Arnaldo Carvalho de Melo escreveu:
>>>> Em Thu, Aug 06, 2020 at 09:43:57PM +0200, Jiri Olsa escreveu:
>>>>> On Wed, Aug 05, 2020 at 10:29:37AM +0800, Jin Yao wrote:
>>>>>> 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=<synthetic pointer>, 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@...ry=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=<optimized out>) at pthread_create.c:477
>>>>>> #6 0x00007fad7823c103 in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95
>>>>>
>>>>> hum, I recall discussing the same issue,
>>>>> I thought it was already fixed :-\ in any case:
>>>>>
>>>>> Acked-by: Jiri Olsa <jolsa@...hat.com>
>>>>
>>>> I added this:
>>>>
>>>> Fixes: 23cbb41c939a ("perf record: Move side band evlist setup to separate routine")
>>>>
>>>> To help this fixe go back to a few stable kernels. Technically the
>>>> problem was introduced much earlier, when the side band thread was
>>>> added, but then this would require more cherry-picking of patches and
>>>> since we have a workaround, i.e. build with libbpf, I think this is
>>>> enough.
>>>
>>> I backtrack on that, as the sideband event is not just for BPF... The
>>> switch-output-event code uses it as well, so it can't be dependent on
>>> LIBBPF being built...
>>>
>>> I'll see what I can do
>>
>> So this is the change I made, the side band thread is may have been
>> already created by
>>
>> [acme@...co ~]$ perf record -h switch-output-event
>>
>> Usage: perf record [<options>] [<command>]
>> or: perf record [<options>] -- <command> [<options>]
>>
>> --switch-output-event <switch output event>
>> switch output event selector. use 'perf list' to list available events
>>
>> [acme@...co ~]$
>>
>> I'm doing some extra checking now on your report, and the patch below
>> has skews because it clashed with the clockid patches by Jiri so I had
>> to resolve its merge.
>
> Sorry, I resent your patch, doh, here is the end result, with my change,
> its ok to call perf_evlist__start_sb_thread() with a NULL evlist, it'll
> just return 0.
>
> - Arnald
>
>
> commit b13536a7e93680625094beb18cdce4ae47a3dbfb
> Author: Jin Yao <yao.jin@...ux.intel.com>
> Date: Wed Aug 5 10:29:37 2020 +0800
>
> perf record: Skip side-band event setup if HAVE_LIBBPF_SUPPORT is not set
>
> 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=<synthetic pointer>, 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@...ry=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=<optimized out>) 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@...t:~# ./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 <yao.jin@...ux.intel.com>
> Acked-by: Jiri Olsa <jolsa@...nel.org>
> Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> Cc: Andi Kleen <ak@...ux.intel.com>
> Cc: Jin Yao <yao.jin@...el.com>
> Cc: Kan Liang <kan.liang@...ux.intel.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Link: http://lore.kernel.org/lkml/20200805022937.29184-1-yao.jin@linux.intel.com
> Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
>
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 7d97c8e9f7f9..f91352f847c0 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -1531,7 +1531,7 @@ 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();
> @@ -1547,7 +1547,7 @@ 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;
>
Thanks so much for helping to refine the patch!
Thanks
Jin Yao
Powered by blists - more mailing lists