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[209.132.180.67]) by mx.google.com with ESMTP id r185si10034725pgr.506.2019.08.19.09.52.56; Mon, 19 Aug 2019 09:53:10 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@linaro.org header.s=google header.b=LZKpjAQj; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linaro.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727957AbfHSQvZ (ORCPT + 99 others); Mon, 19 Aug 2019 12:51:25 -0400 Received: from mail-io1-f65.google.com ([209.85.166.65]:40459 "EHLO mail-io1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727681AbfHSQvZ (ORCPT ); Mon, 19 Aug 2019 12:51:25 -0400 Received: by mail-io1-f65.google.com with SMTP id t6so5764525ios.7 for ; Mon, 19 Aug 2019 09:51:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=azVJnvWnS4iAifUctENzXhTQHJYaXzLyjFRbYXJ3Y50=; b=LZKpjAQj2QbA2t3Oya83T0tkOuZepDBwNBcQ1E9gNnRT5/RFMFtxywYg2gkGk5Q+TQ S+GoMGajFBqn+OADKQIsTCE/t6B6x6aOUpwgeG70xCWKK6r6DWhiCDXnDtNBxuyAMpol V1rPHeWk5pZ0XO8As+HpZB3J4oT477oJGWlBtKan88A+clNVpVZKE+SZqOEo2RwUBWD1 3AXbtUIksfCEZxAivt6sApyqgvWnDFPRkWmo/t5Tm27TRBqAcXSbrBr5SCRxfhhh/+ey HzVwbAA4gmauUK5UDCznOS4WecJLIF64CeVR9s/c6BqXNfBWGDp+/AZt8QUfxI9ZZnmU sjwg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=azVJnvWnS4iAifUctENzXhTQHJYaXzLyjFRbYXJ3Y50=; b=Rq1/tqWVu4TPqn7Hv+YBe2eJfeH/U8puomq8R5GlS2QJk3FMXKXbHeHKxDn1UTMtUn qmLGqFW/OTDt305AFEU5s+ZSKA+9BIKqyyVMRcHOxfooAhzmgKHrur4r9J0tvmMo5Z4R D5gah8BP3V/gHungo1ADDKzf8LV+0cDdK94shZlP/UfMAeV8U736B8wwf1UKm9HN+ax4 4papmTuKA4RoS1a8toW1bWjDqt1e8qRptuLq2Y5XlM0SBaAJ4POOfsetQgFIxfJiLqHA JvYBnE9H6tzqEcxA1AgOPVcL7BeFaxptOv9ZgOF2tQlNTyi9PM8qZ9sSt+DJz1KjGa7r lrxg== X-Gm-Message-State: APjAAAUlNlw+3c7nODch4tkMBBoAe0LNb0OqF+xg3KooM9V817TQpzdL 8OrD8EQCreaLD0WRpnIXwZ/vL5VIh8r1YqF/MRytRQ== X-Received: by 2002:a02:6914:: with SMTP id e20mr27123117jac.83.1566233484138; Mon, 19 Aug 2019 09:51:24 -0700 (PDT) MIME-Version: 1.0 References: <291d2cda6ee75b4cd4c9ce717c177db18bf03a31.1565188228.git.ilubashe@akamai.com> <20190814184814.GM9280@kernel.org> <20190814185213.GN9280@kernel.org> <23f7b8c7616a467c93ee2c77e8ffd3cf@usma1ex-dag1mb6.msg.corp.akamai.com> <20190815214236.GA3929@kernel.org> In-Reply-To: <20190815214236.GA3929@kernel.org> From: Mathieu Poirier Date: Mon, 19 Aug 2019 10:51:12 -0600 Message-ID: Subject: Re: [PATCH v3 3/4] perf: Use CAP_SYSLOG with kptr_restrict checks To: Arnaldo Carvalho de Melo Cc: "Lubashev, Igor" , Linux Kernel Mailing List , Jiri Olsa , Alexey Budankov , Peter Zijlstra , Ingo Molnar , Alexander Shishkin , Namhyung Kim , Suzuki K Poulose , linux-arm-kernel , James Morris , Leo Yan Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 15 Aug 2019 at 15:42, Arnaldo Carvalho de Melo wrote: > > Em Thu, Aug 15, 2019 at 02:16:48PM -0600, Mathieu Poirier escreveu: > > On Wed, 14 Aug 2019 at 14:02, Lubashev, Igor wrote: > > > > > > > On Wed, August 14, 2019 at 2:52 PM Arnaldo Carvalho de Melo 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@quaco ~]# cat /proc/sys/kernel/kptr_restrict > > > > 0 > > > > [root@quaco ~]# 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@quaco ~]# echo 1 > > > > > /proc/sys/kernel/kptr_restrict [root@quaco ~]# 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@quaco ~]# echo > > > > 0 > /proc/sys/kernel/kptr_restrict [root@quaco ~]# 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@quaco ~]# > > > > > > > > [acme@quaco 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@quaco 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 ] > > > > > > 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 > > > > I isolated the problem to libcap-dev - if it is not installed a > > segmentation fault will occur. Since this set is about using > > capabilities it is obvious that not having it on a system should fail > > a trace session, but it should not crash it. > > It shouldn't crash on x86_64: > > root@quaco ~]# sysctl kernel.kptr_restrict > kernel.kptr_restrict = 0 > [root@quaco ~]# perf record -e instructions:k uname > Linux > [ perf record: Woken up 1 times to write data ] > [ perf record: Captured and wrote 0.023 MB perf.data (5 samples) ] > [root@quaco ~]# ldd ~/bin/perf | grep libcap > [root@quaco ~]# perf -v > perf version 5.3.rc4.g329ca330bf8b > [root@quaco ~]# > [acme@quaco perf]$ git log --oneline -4 > 329ca330bf8b (HEAD -> perf/cap) perf symbols: Use CAP_SYSLOG with kptr_restrict checks > f7b9999387af perf tools: Use CAP_SYS_ADMIN with perf_event_paranoid checks > 4d0489cf1c47 (acme.korg/tmp.perf/script-switch-on-off, perf/core) perf report: Add --switch-on/--switch-off events > 2f53ae347f59 perf top: Add --switch-on/--switch-off events > [acme@quaco perf]$ > > > If libcap-dev is not installed function symbol__restricted_filename() > > will return true, which in turn will prevent symbol_name to be set in > > machine__get_running_kernel_start(). That prevents function > > map__set_kallsyms_ref_reloc_sym() from being called in > > machine__create_kernel_maps(), resulting in kmap->ref_reloc_sym being > > NULL in _perf_event__synthesize_kernel_mmap() and a segmentation > > fault. > > Can you please try with my perf/cap branch? Perhaps you're using Igor's > original set of patches? I made changes to the fallback, he was making > it return false while I made it fallback to geteuid() == 0, as was > before his patches. Things are working properly on your perf/cap branch. I tested with on both x86 and ARM. Mathieu > > - Arnaldo > > > I am not sure how this can be fixed. I counted a total of 19 > > instances where kmap->ref_reloc_sym->XYZ is called, only 2 of wich > > care to check if kmap->ref_reloc_sym is valid before proceeding. As > > such I must hope that in the 17 other cases, kmap->ref_reloc_sym is > > guaranteed to be valid. If I am correct then all we need is to check > > for a valid pointer in _perf_event__synthesize_kernel_mmap(). > > Otherwise it will be a little harder. > > > > Mathieu > > -- > > - Arnaldo