| 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: <CAM9d7cjmH=nkEt-z_XpZ1J0oL-EY2d52oz70-KpN+uzM5SEk6A@mail.gmail.com>
Date: Wed, 29 May 2024 12:18:58 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Ben Gainey <Ben.Gainey@....com>
Cc: "alexander.shishkin@...ux.intel.com" <alexander.shishkin@...ux.intel.com>,
"peterz@...radead.org" <peterz@...radead.org>, "acme@...nel.org" <acme@...nel.org>,
"mingo@...hat.com" <mingo@...hat.com>, James Clark <James.Clark@....com>,
"adrian.hunter@...el.com" <adrian.hunter@...el.com>, "irogers@...gle.com" <irogers@...gle.com>,
"jolsa@...nel.org" <jolsa@...nel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>, Mark Rutland <Mark.Rutland@....com>
Subject: Re: [PATCH v6 4/4] tools/perf: Allow inherit + PERF_SAMPLE_READ when
opening events
Hello,
On Wed, May 29, 2024 at 10:48 AM Ben Gainey <Ben.Gainey@....com> wrote:
>
> On Mon, 2024-05-27 at 18:47 +0100, Ben Gainey wrote:
> > On Thu, 2024-05-23 at 18:41 -0700, Namhyung Kim wrote:
> > > On Tue, May 21, 2024 at 6:30 AM Ben Gainey <ben.gainey@....com>
> > > wrote:
> > > >
> > > > The tool will now default to this new mode if the user specifies
> > > > a
> > > > sampling group when not in system-wide mode, and when --no-
> > > > inherit
> > > > is not specified.
> > > >
> > > > This change updates evsel to allow the combination of inherit
> > > > and PERF_SAMPLE_READ.
> > > >
> > > > A fallback is implemented for kernel versions where this feature
> > > > is
> > > > not
> > > > supported.
> > >
> > > But I'm afraid the test would fail on old kernels. Maybe we need
> > > to
> > > put it in the selftests.
> > >
> >
> > Sorry, not clear what you mean?
> >
> > Is the issue that the fallback on older kernels fails, or that the
> > "perf test" tests fail?
> >
> > Thanks
> > Ben
>
> Just to follow up, I've rechecked the fallback on an unmodified 6.9.1
> kernel with the following:
>
> perf record -vv -e '{cycles,instructions}:S' ls
>
> With an unpatched version of perf running on an unpatched kernel, the
> cycles event is opened as:
>
> ------------------------------------------------------------
> perf_event_attr:
> type 0 (PERF_TYPE_HARDWARE)
> size 136
> config 0 (PERF_COUNT_HW_CPU_CYCLES)
> { sample_period, sample_freq } 4000
> sample_type IP|TID|TIME|READ|ID|PERIOD
> read_format ID|GROUP|LOST
> disabled 1
> exclude_kernel 1
> exclude_hv 1
> mmap 1
> comm 1
> freq 1
> enable_on_exec 1
> task 1
> sample_id_all 1
> exclude_guest 1
> mmap2 1
> comm_exec 1
> ksymbol 1
> bpf_event 1
> ------------------------------------------------------------
>
> whereas with these patches applied to perf, on an unpatched kernel, the
> output is as follows
>
> ------------------------------------------------------------
> perf_event_attr:
> type 0 (PERF_TYPE_HARDWARE)
> size 136
> config 0 (PERF_COUNT_HW_CPU_CYCLES)
> { sample_period, sample_freq } 4000
> sample_type IP|TID|TIME|READ|ID|PERIOD
> read_format ID|GROUP|LOST
> disabled 1
> inherit 1
> exclude_kernel 1
> exclude_hv 1
> mmap 1
> comm 1
> freq 1
> enable_on_exec 1
> task 1
> sample_id_all 1
> exclude_guest 1
> mmap2 1
> comm_exec 1
> ksymbol 1
> bpf_event 1
> ------------------------------------------------------------
> sys_perf_event_open: pid 3442954 cpu 0 group_fd -1 flags 0x8
> sys_perf_event_open failed, error -22
> Using PERF_SAMPLE_READ / :S modifier is not compatible with
> inherit, falling back to no-inherit.
> ------------------------------------------------------------
> perf_event_attr:
> type 0 (PERF_TYPE_HARDWARE)
> size 136
> config 0 (PERF_COUNT_HW_CPU_CYCLES)
> { sample_period, sample_freq } 4000
> sample_type IP|TID|TIME|READ|ID|PERIOD
> read_format ID|GROUP|LOST
> disabled 1
> exclude_kernel 1
> exclude_hv 1
> mmap 1
> comm 1
> freq 1
> enable_on_exec 1
> task 1
> sample_id_all 1
> exclude_guest 1
> mmap2 1
> comm_exec 1
> ksymbol 1
> bpf_event 1
> ------------------------------------------------------------
>
> The command falls back to the same configuration as was previously
> used. The same is true for the instructions event.
>
> `perf test` fails on an unpatched kernel in "15: Setup struct
> perf_event_attr" for the test "test-record-group-sampling1" but that is
> surely expected for unpatched kernels?
>
> Is there some very-old kernel version where this would be expected to
> succeed by accident?
I don't think so but I don't want the test to fail depending on the
kernel version. Maybe we can check the allowed combination
first and skip the test if perf_event_open() fails. And then it can
verify if the kernel rejects the unsupported combinations. Not
sure if it's easy to do that in the current attr test framework.
Thanks,
Namhyung
Powered by blists - more mailing lists