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  1. 27 Feb, 2019 1 commit
  3. 09 Sep, 2018 1 commit
  5. 24 Aug, 2018 1 commit
  7. 09 Aug, 2018 1 commit
    • Masami Hiramatsu's avatar
      ring_buffer: tracing: Inherit the tracing setting to next ring buffer · a26030a6
      Masami Hiramatsu authored 
      commit 73c8d894 upstream.

Maintain the tracing on/off setting of the ring_buffer when switching
to the trace buffer snapshot.

Taking a snapshot is done by swapping the backup ring buffer
(max_tr_buffer). But since the tracing on/off setting is defined
by the ring buffer, when swapping it, the tracing on/off setting
can also be changed. This causes a strange result like below:

  /sys/kernel/debug/tracing # cat tracing_on
  1
  /sys/kernel/debug/tracing # echo 0 > tracing_on
  /sys/kernel/debug/tracing # cat tracing_on
  0
  /sys/kernel/debug/tracing # echo 1 > snapshot
  /sys/kernel/debug/tracing # cat tracing_on
  1
  /sys/kernel/debug/tracing # echo 1 > snapshot
  /sys/kernel/debug/tracing # cat tracing_on
  0

We don't touch tracing_on, but snapshot changes tracing_on
setting each time. This is an anomaly, because user doesn't know
that each "ring_buffer" stores its own tracing-enable state and
the snapshot is done by swapping ring buffers.

Link: http://lkml.kernel.org/r/153149929558.11274.11730609978254724394.stgit@devbox

Cc: Ingo Molnar <mingo@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
Cc: Hiraku Toyooka <hiraku.toyooka@cybertrust.co.jp>
Cc: stable@vger.kernel.org
Fixes: debdd57f

 ("tracing: Make a snapshot feature available from userspace")
Signed-off-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
[ Updated commit log and comment in the code ]
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: default avatarSudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      a26030a6
  9. 02 Jan, 2018 3 commits
  11. 20 Dec, 2017 1 commit
  13. 05 Oct, 2017 2 commits
  15. 27 Sep, 2017 2 commits
  17. 30 Aug, 2017 1 commit
  19. 27 Jul, 2017 1 commit
    • Chunyu Hu's avatar
      tracing: Fix kmemleak in instance_rmdir · 919e4811
      Chunyu Hu authored 
      commit db9108e0 upstream.

Hit the kmemleak when executing instance_rmdir, it forgot releasing
mem of tracing_cpumask. With this fix, the warn does not appear any
more.

unreferenced object 0xffff93a8dfaa7c18 (size 8):
  comm "mkdir", pid 1436, jiffies 4294763622 (age 9134.308s)
  hex dump (first 8 bytes):
    ff ff ff ff ff ff ff ff                          ........
  backtrace:
    [<ffffffff88b6567a>] kmemleak_alloc+0x4a/0xa0
    [<ffffffff8861ea41>] __kmalloc_node+0xf1/0x280
    [<ffffffff88b505d3>] alloc_cpumask_var_node+0x23/0x30
    [<ffffffff88b5060e>] alloc_cpumask_var+0xe/0x10
    [<ffffffff88571ab0>] instance_mkdir+0x90/0x240
    [<ffffffff886e5100>] tracefs_syscall_mkdir+0x40/0x70
    [<ffffffff886565c9>] vfs_mkdir+0x109/0x1b0
    [<ffffffff8865b1d0>] SyS_mkdir+0xd0/0x100
    [<ffffffff88403857>] do_syscall_64+0x67/0x150
    [<ffffffff88b710e7>] return_from_SYSCALL_64+0x0/0x6a
    [<ffffffffffffffff>] 0xffffffffffffffff

Link: http://lkml.kernel.org/r/1500546969-12594-1-git-send-email-chuhu@redhat.com

Fixes: ccfe9e42

 ("tracing: Make tracing_cpumask available for all instances")
Signed-off-by: default avatarChunyu Hu <chuhu@redhat.com>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      919e4811
  21. 21 Jul, 2017 1 commit
  23. 27 Apr, 2017 1 commit
  25. 21 Apr, 2017 1 commit
    • Namhyung Kim's avatar
      ftrace: Fix function pid filter on instances · 7da0f8e5
      Namhyung Kim authored 
      commit d879d0b8 upstream.

When function tracer has a pid filter, it adds a probe to sched_switch
to track if current task can be ignored.  The probe checks the
ftrace_ignore_pid from current tr to filter tasks.  But it misses to
delete the probe when removing an instance so that it can cause a crash
due to the invalid tr pointer (use-after-free).

This is easily reproducible with the following:

  # cd /sys/kernel/debug/tracing
  # mkdir instances/buggy
  # echo $$ > instances/buggy/set_ftrace_pid
  # rmdir instances/buggy

  ============================================================================
  BUG: KASAN: use-after-free in ftrace_filter_pid_sched_switch_probe+0x3d/0x90
  Read of size 8 by task kworker/0:1/17
  CPU: 0 PID: 17 Comm: kworker/0:1 Tainted: G    B           4.11.0-rc3  #198
  Call Trace:
   dump_stack+0x68/0x9f
   kasan_object_err+0x21/0x70
   kasan_report.part.1+0x22b/0x500
   ? ftrace_filter_pid_sched_switch_probe+0x3d/0x90
   kasan_report+0x25/0x30
   __asan_load8+0x5e/0x70
   ftrace_filter_pid_sched_switch_probe+0x3d/0x90
   ? fpid_start+0x130/0x130
   __schedule+0x571/0xce0
   ...

To fix it, use ftrace_clear_pids() to unregister the probe.  As
instance_rmdir() already updated ftrace codes, it can just free the
filter safely.

Link: http://lkml.kernel.org/r/20170417024430.21194-2-namhyung@kernel.org

Fixes: 0c8916c3

 ("tracing: Add rmdir to remove multibuffer instances")
Cc: Ingo Molnar <mingo@kernel.org>
Reviewed-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: default avatarNamhyung Kim <namhyung@kernel.org>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      7da0f8e5
  27. 15 Mar, 2017 1 commit
    • Eric W. Biederman's avatar
      fs: Better permission checking for submounts · d3381fab
      Eric W. Biederman authored 
      commit 93faccbb upstream.

To support unprivileged users mounting filesystems two permission
checks have to be performed: a test to see if the user allowed to
create a mount in the mount namespace, and a test to see if
the user is allowed to access the specified filesystem.

The automount case is special in that mounting the original filesystem
grants permission to mount the sub-filesystems, to any user who
happens to stumble across the their mountpoint and satisfies the
ordinary filesystem permission checks.

Attempting to handle the automount case by using override_creds
almost works.  It preserves the idea that permission to mount
the original filesystem is permission to mount the sub-filesystem.
Unfortunately using override_creds messes up the filesystems
ordinary permission checks.

Solve this by being explicit that a mount is a submount by introducing
vfs_submount, and using it where appropriate.

vfs_submount uses a new mo...
      d3381fab
  29. 25 Sep, 2016 2 commits
  31. 12 Sep, 2016 1 commit
  33. 02 Sep, 2016 1 commit
    • Steven Rostedt (Red Hat)'s avatar
      tracing: Added hardware latency tracer · e7c15cd8
      Steven Rostedt (Red Hat) authored 
      
The hardware latency tracer has been in the PREEMPT_RT patch for some time.
It is used to detect possible SMIs or any other hardware interruptions that
the kernel is unaware of. Note, NMIs may also be detected, but that may be
good to note as well.

The logic is pretty simple. It simply creates a thread that spins on a
single CPU for a specified amount of time (width) within a periodic window
(window). These numbers may be adjusted by their cooresponding names in

   /sys/kernel/tracing/hwlat_detector/

The defaults are window = 1000000 us (1 second)
                 width  =  500000 us (1/2 second)

The loop consists of:

	t1 = trace_clock_local();
	t2 = trace_clock_local();

Where trace_clock_local() is a variant of sched_clock().

The difference of t2 - t1 is recorded as the "inner" timestamp and also the
timestamp  t1 - prev_t2 is recorded as the "outer" timestamp. If either of
these differences are greater than the time denoted in
/sys/kernel/tracing/tracing_thresh then it records the event.

When this tracer is started, and tracing_thresh is zero, it changes to the
default threshold of 10 us.

The hwlat tracer in the PREEMPT_RT patch was originally written by
Jon Masters. I have modified it quite a bit and turned it into a
tracer.
Based-on-code-by: default avatarJon Masters <jcm@redhat.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      e7c15cd8
  35. 23 Aug, 2016 1 commit
  37. 05 Jul, 2016 2 commits
  39. 23 Jun, 2016 1 commit
    • Steven Rostedt (Red Hat)'s avatar
      tracing: Skip more functions when doing stack tracing of events · be54f69c
      Steven Rostedt (Red Hat) authored 
       # echo 1 > options/stacktrace
 # echo 1 > events/sched/sched_switch/enable
 # cat trace
          <idle>-0     [002] d..2  1982.525169: <stack trace>
 => save_stack_trace
 => __ftrace_trace_stack
 => trace_buffer_unlock_commit_regs
 => event_trigger_unlock_commit
 => trace_event_buffer_commit
 => trace_event_raw_event_sched_switch
 => __schedule
 => schedule
 => schedule_preempt_disabled
 => cpu_startup_entry
 => start_secondary

The above shows that we are seeing 6 functions before ever making it to the
caller of the sched_switch event.

 # echo stacktrace > events/sched/sched_switch/trigger
 # cat trace
          <idle>-0     [002] d..3  2146.335208: <stack trace>
 => trace_event_buffer_commit
 => trace_event_raw_event_sched_switch
 => __schedule
 => schedule
 => schedule_preempt_disabled
 => cpu_startup_entry
 => start_secondary

The stacktrace trigger isn't as bad, because it adds its own skip to the
stacktracing, but still has two events extra.

One issue is that if the stacktrace passes its own "regs" then there should
be no addition to the skip, as the regs will not include the functions being
called. This was an issue that was fixed by commit 7717c6be

 ("tracing:
Fix stacktrace skip depth in trace_buffer_unlock_commit_regs()" as adding
the skip number for kprobes made the probes not have any stack at all.

But since this is only an issue when regs is being used, a skip should be
added if regs is NULL. Now we have:

 # echo 1 > options/stacktrace
 # echo 1 > events/sched/sched_switch/enable
 # cat trace
          <idle>-0     [000] d..2  1297.676333: <stack trace>
 => __schedule
 => schedule
 => schedule_preempt_disabled
 => cpu_startup_entry
 => rest_init
 => start_kernel
 => x86_64_start_reservations
 => x86_64_start_kernel

 # echo stacktrace > events/sched/sched_switch/trigger
 # cat trace
          <idle>-0     [002] d..3  1370.759745: <stack trace>
 => __schedule
 => schedule
 => schedule_preempt_disabled
 => cpu_startup_entry
 => start_secondary

And kprobes are not touched.
Reported-by: default avatarPeter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      be54f69c
  41. 20 Jun, 2016 5 commits
  43. 03 May, 2016 1 commit
    • Steven Rostedt (Red Hat)'s avatar
      tracing: Use temp buffer when filtering events · 0fc1b09f
      Steven Rostedt (Red Hat) authored 
      
Filtering of events requires the data to be written to the ring buffer
before it can be decided to filter or not. This is because the parameters of
the filter are based on the result that is written to the ring buffer and
not on the parameters that are passed into the trace functions.

The ftrace ring buffer is optimized for writing into the ring buffer and
committing. The discard procedure used when filtering decides the event
should be discarded is much more heavy weight. Thus, using a temporary
filter when filtering events can speed things up drastically.

Without a temp buffer we have:

 # trace-cmd start -p nop
 # perf stat -r 10 hackbench 50
       0.790706626 seconds time elapsed ( +-  0.71% )

 # trace-cmd start -e all
 # perf stat -r 10 hackbench 50
       1.566904059 seconds time elapsed ( +-  0.27% )

 # trace-cmd start -e all -f 'common_preempt_count==20'
 # perf stat -r 10 hackbench 50
       1.690598511 seconds time elapsed ( +-  0.19% )

 # trace-cmd start -e all -f 'common_preempt_count!=20'
 # perf stat -r 10 hackbench 50
       1.707486364 seconds time elapsed ( +-  0.30% )

The first run above is without any tracing, just to get a based figure.
hackbench takes ~0.79 seconds to run on the system.

The second run enables tracing all events where nothing is filtered. This
increases the time by 100% and hackbench takes 1.57 seconds to run.

The third run filters all events where the preempt count will equal "20"
(this should never happen) thus all events are discarded. This takes 1.69
seconds to run. This is 10% slower than just committing the events!

The last run enables all events and filters where the filter will commit all
events, and this takes 1.70 seconds to run. The filtering overhead is
approximately 10%. Thus, the discard and commit of an event from the ring
buffer may be about the same time.

With this patch, the numbers change:

 # trace-cmd start -p nop
 # perf stat -r 10 hackbench 50
       0.778233033 seconds time elapsed ( +-  0.38% )

 # trace-cmd start -e all
 # perf stat -r 10 hackbench 50
       1.582102692 seconds time elapsed ( +-  0.28% )

 # trace-cmd start -e all -f 'common_preempt_count==20'
 # perf stat -r 10 hackbench 50
       1.309230710 seconds time elapsed ( +-  0.22% )

 # trace-cmd start -e all -f 'common_preempt_count!=20'
 # perf stat -r 10 hackbench 50
       1.786001924 seconds time elapsed ( +-  0.20% )

The first run is again the base with no tracing.

The second run is all tracing with no filtering. It is a little slower, but
that may be well within the noise.

The third run shows that discarding all events only took 1.3 seconds. This
is a speed up of 23%! The discard is much faster than even the commit.

The one downside is shown in the last run. Events that are not discarded by
the filter will take longer to add, this is due to the extra copy of the
event.

Cc: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      0fc1b09f
  45. 29 Apr, 2016 5 commits
  47. 27 Apr, 2016 1 commit
  49. 26 Apr, 2016 2 commits
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