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  1. 23 Sep, 2019 2 commits
    • Arnaldo Carvalho de Melo's avatar
      perf record: Move restricted maps check to after a possible fallback to not collect kernel samples · c8b567c8
      Arnaldo Carvalho de Melo authored 
      Before:

  [acme@quaco ~]$ perf record -b -e cycles date
  WARNING: Kernel address maps (/proc/{kallsyms,modules}) are restricted,
  check /proc/sys/kernel/kptr_restrict and /proc/sys/kernel/perf_event_paranoid.

  Samples in kernel functions may not be resolved if a suitable vmlinux
  file is not found in the buildid cache or in the vmlinux path.

  Samples in kernel modules won't be resolved at all.

  If some relocation was applied (e.g. kexec) symbols may be misresolved
  even with a suitable vmlinux or kallsyms file.

  Mon 23 Sep 2019 11:00:59 AM -03
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.005 MB perf.data (14 samples) ]
  [acme@quaco ~]$

But we did a fallback and exclude_kernel was set, so no need for
resolving kernel symbols:

  $ perf evlist -v
  cycles:u: size: 112, { sample_period, sample_freq }: 4000, sample_type: IP|TID|TIME|PERIOD|BRANCH_STACK, read_format: ID, 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, branch_sample_type: ANY
  $

After:

  [acme@quaco ~]$ perf record -b -e cycles date
  Mon 23 Sep 2019 11:07:18 AM -03
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.007 MB perf.data (16 samples) ]
  [acme@quaco ~]$ perf evlist -v
  cycles:u: size: 112, { sample_period, sample_freq }: 4000, sample_type: IP|TID|TIME|PERIOD|BRANCH_STACK, read_format: ID, 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, branch_sample_type: ANY
  [acme@quaco ~]$

No needless warning is emitted.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lkml.kernel.org/n/tip-5yqnr8xcqwhr15xktj2097ac@git.kernel.orgSigned-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
      c8b567c8
    • Stephane Eranian's avatar
      perf record: Fix priv level with branch sampling for paranoid=2 · 4ec8d984
      Stephane Eranian authored 
      Now that the default perf_events paranoid level is set to 2, a regular
user cannot monitor kernel level activity anymore. As such, with the
following cmdline:

  $ perf record -e cycles date

The perf tool first tries cycles:uk but then falls back to cycles:u as
can be seen in the perf report --header-only output:

  cmdline : /export/hda3/tmp/perf.tip record -e cycles ls
  event : name = cycles:u, , id = { 436186, ... }

This is okay as long as there is way to learn the priv level was changed
internally by the tool.

But consider a similar example:

  $ perf record -b -e cycles date
  Error:
  You may not have permission to collect stats.

Consider tweaking /proc/sys/kernel/perf_event_paranoid,
which controls use of the performance events system by
unprivileged users (without CAP_SYS_ADMIN).
...

Why is that treated differently given that the branch sampling inherits the
priv level of the first event in this case, i.e., cycles:u? It turns out
that the branch sampling code is more picky and also checks exclude_hv.

In the fallback path, perf record is setting exclude_kernel = 1, but it
does not change exclude_hv. This does not seem to match the restriction
imposed by paranoid = 2.

This patch fixes the problem by forcing exclude_hv = 1 in the fallback
for paranoid=2. With this in place:

  $ perf record -b -e cycles date
    cmdline : /export/hda3/tmp/perf.tip record -b -e cycles ls
    event : name = cycles:u, , id = { 436847, ... }

And the command succeeds as expected.

V2 fix a white space.

Committer testing:

After aplying the patch we get:

  [acme@quaco ~]$ perf record -b -e cycles date
  WARNING: Kernel address maps (/proc/{kallsyms,modules}) are restricted,
  check /proc/sys/kernel/kptr_restrict and /proc/sys/kernel/perf_event_paranoid.

  Samples in kernel functions may not be resolved if a suitable vmlinux
  file is not found in the buildid cache or in the vmlinux path.

  Samples in kernel modules won't be resolved at all.

  If some relocation was applied (e.g. kexec) symbols may be misresolved
  even with a suitable vmlinux or kallsyms file.

  Mon 23 Sep 2019 11:00:59 AM -03
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.005 MB perf.data (14 samples) ]
  [acme@quaco ~]$ perf evlist -v
  cycles:u: size: 112, { sample_period, sample_freq }: 4000, sample_type: IP|TID|TIME|PERIOD|BRANCH_STACK, read_format: ID, 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, branch_sample_type: ANY
  [acme@quaco ~]$

That warning about restricted kernel maps will be suppressed in a follow
up patch, as perf_event_attr.exclude_kernel is set, i.e. no samples for
the kernel will be taken and thus no need for those maps.
Signed-off-by: default avatarStephane Eranian <eranian@google.com>
Acked-by: default avatarJiri Olsa <jolsa@redhat.com>
Tested-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20190920230356.41420-1-eranian@google.comSigned-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
      4ec8d984
  3. 22 Sep, 2019 1 commit
    • Ingo Molnar's avatar
      Merge tag 'perf-urgent-for-mingo-5.4-20190921' of... · 2b327697
      Ingo Molnar authored 
      Merge tag 'perf-urgent-for-mingo-5.4-20190921' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux into perf/urgent

Pull perf/urgent fixes from Arnaldo Carvalho de Melo:

perf tests:

  Jiri Olsa:

  - Fix 'make -C tools/perf build-test' static build entry.

perf record:

  Jiri Olsa:

  - Fix segfault in cpu_cache_level__read() when reading CPU topology.

session:

  Mamatha Inamdar:

  - Properly propagate error when reading a perf.data file, it may
    not exist or the user may not have permissions, etc.

perf probe:

  Masami Hiramatsu:

  - Skip same probe address for a given line.

  - Clear tev->nargs in clear_probe_trace_event(), fixing segfault.

tools headers UAPI:

  Arnaldo Carvalho de Melo:

  - Sync headers, among them prctl.h, that introduces two new options
    that are now supported in the 'perf trace' prctl syscall args
    beautifiers.
Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      2b327697
  5. 20 Sep, 2019 37 commits
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