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Message-ID: <CANLsYkyhSO13NhKMkCsHT87z-380JHDKsM3U_R=HesN0bKEDPA@mail.gmail.com>
Date: Thu, 15 Aug 2019 09:01:51 -0600
From: Mathieu Poirier <mathieu.poirier@...aro.org>
To: "Lubashev, Igor" <ilubashe@...mai.com>
Cc: Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Jiri Olsa <jolsa@...hat.com>,
Alexey Budankov <alexey.budankov@...ux.intel.com>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Namhyung Kim <namhyung@...nel.org>,
Suzuki K Poulose <suzuki.poulose@....com>,
linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
James Morris <jmorris@...ei.org>
Subject: Re: [PATCH v3 3/4] perf: Use CAP_SYSLOG with kptr_restrict checks
On Wed, 14 Aug 2019 at 14:02, Lubashev, Igor <ilubashe@...mai.com> wrote:
>
> > On Wed, August 14, 2019 at 2:52 PM Arnaldo Carvalho de Melo <arnaldo.melo@...il.com> wrote:
> > Em Wed, Aug 14, 2019 at 03:48:14PM -0300, Arnaldo Carvalho de Melo
> > escreveu:
> > > Em Wed, Aug 14, 2019 at 12:04:33PM -0600, Mathieu Poirier escreveu:
> > > > # echo 0 > /proc/sys/kernel/kptr_restrict # ./tools/perf/perf record
> > > > -e instructions:k uname
> > > > perf: Segmentation fault
> > > > Obtained 10 stack frames.
> > > > ./tools/perf/perf(sighandler_dump_stack+0x44) [0x55af9e5da5d4]
> > > > /lib/x86_64-linux-gnu/libc.so.6(+0x3ef20) [0x7fd31efb6f20]
> > > > ./tools/perf/perf(perf_event__synthesize_kernel_mmap+0xa7)
> > > > [0x55af9e590337]
> > > > ./tools/perf/perf(+0x1cf5be) [0x55af9e50c5be]
> > > > ./tools/perf/perf(cmd_record+0x1022) [0x55af9e50dff2]
> > > > ./tools/perf/perf(+0x23f98d) [0x55af9e57c98d]
> > > > ./tools/perf/perf(+0x23fc9e) [0x55af9e57cc9e]
> > > > ./tools/perf/perf(main+0x369) [0x55af9e4f6bc9]
> > > > /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xe7)
> > > > [0x7fd31ef99b97]
> > > > ./tools/perf/perf(_start+0x2a) [0x55af9e4f704a] Segmentation fault
> > > >
> > > > I can reproduce this on both x86 and ARM64.
> > >
> > > I don't see this with these two csets removed:
> > >
> > > 7ff5b5911144 perf symbols: Use CAP_SYSLOG with kptr_restrict checks
> > > d7604b66102e perf tools: Use CAP_SYS_ADMIN with perf_event_paranoid
> > > checks
> > >
> > > Which were the ones I guessed were related to the problem you
> > > reported, so they are out of my ongoing perf/core pull request to
> > > Ingo/Thomas, now trying with these applied and your instructions...
> >
> > Can't repro:
> >
> > [root@...co ~]# cat /proc/sys/kernel/kptr_restrict
> > 0
> > [root@...co ~]# perf record -e instructions:k uname Linux [ perf record:
> > Woken up 1 times to write data ] [ perf record: Captured and wrote 0.024 MB
> > perf.data (1 samples) ] [root@...co ~]# echo 1 >
> > /proc/sys/kernel/kptr_restrict [root@...co ~]# perf record -e instructions:k
> > uname Linux [ perf record: Woken up 1 times to write data ] [ perf record:
> > Captured and wrote 0.024 MB perf.data (1 samples) ] [root@...co ~]# echo
> > 0 > /proc/sys/kernel/kptr_restrict [root@...co ~]# perf record -e
> > instructions:k uname Linux [ perf record: Woken up 1 times to write data ] [
> > perf record: Captured and wrote 0.024 MB perf.data (1 samples) ]
> > [root@...co ~]#
> >
> > [acme@...co perf]$ git log --oneline --author Lubashev tools/
> > 7ff5b5911144 (HEAD -> perf/cap, acme.korg/tmp.perf/cap,
> > acme.korg/perf/cap) perf symbols: Use CAP_SYSLOG with kptr_restrict
> > checks d7604b66102e perf tools: Use CAP_SYS_ADMIN with
> > perf_event_paranoid checks c766f3df635d perf ftrace: Use CAP_SYS_ADMIN
> > instead of euid==0 c22e150e3afa perf tools: Add helpers to use capabilities if
> > present
> > 74d5f3d06f70 tools build: Add capability-related feature detection perf
> > version 5.3.rc4.g7ff5b5911144 [acme@...co perf]$
>
> I got an ARM64 cloud VM, but I cannot reproduce.
> # cat /proc/sys/kernel/kptr_restrict
> 0
>
> Perf trace works fine (does not die):
> # ./perf trace -a
>
> Here is my setup:
> Repo: git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git
> Branch: tmp.perf/cap
> Commit: 7ff5b5911 "perf symbols: Use CAP_SYSLOG with kptr_restrict checks"
> gcc --version: gcc (Ubuntu/Linaro 7.4.0-1ubuntu1~18.04.1) 7.4.0
> uname -a: Linux arm-4-par-1 4.9.93-mainline-rev1 #1 SMP Tue Apr 10 09:54:46 UTC 2018 aarch64 aarch64 aarch64 GNU/Linux
> lsb_release -a: Ubuntu 18.04.3 LTS
>
> Auto-detecting system features:
> ... dwarf: [ on ]
> ... dwarf_getlocations: [ on ]
> ... glibc: [ on ]
> ... gtk2: [ on ]
> ... libaudit: [ on ]
> ... libbfd: [ on ]
> ... libcap: [ on ]
> ... libelf: [ on ]
> ... libnuma: [ on ]
> ... numa_num_possible_cpus: [ on ]
> ... libperl: [ on ]
> ... libpython: [ on ]
> ... libcrypto: [ on ]
> ... libunwind: [ on ]
> ... libdw-dwarf-unwind: [ on ]
> ... zlib: [ on ]
> ... lzma: [ on ]
> ... get_cpuid: [ OFF ]
> ... bpf: [ on ]
> ... libaio: [ on ]
> ... libzstd: [ on ]
> ... disassembler-four-args: [ on ]
Thank you for posting your configuration. I will see where things are
different with mine.
>
> I also could not reproduce on x86:
> lsb_release -a: Ubuntu 18.04.1 LTS
> gcc --version: gcc (Ubuntu 7.4.0-1ubuntu1~18.04aka10.0.0) 7.4.0
> uname -r: 4.4.0-154-generic
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