linux-toradex.git/kernel/trace, branch v3.0.16

tracing: fix event_subsystem ref counting

2011-12-09T16:52:48+00:00

commit cb59974742aea24adf6637eb0c4b8e7b48bca6fb upstream.

Fix a bug introduced by e9dbfae5, which prevents event_subsystem from
ever being released.

Ref_count was added to keep track of subsystem users, not for counting
events.  Subsystem is created with ref_count = 1, so there is no need to
increment it for every event, we have nr_events for that.  Fix this by
touching ref_count only when we actually have a new user -
subsystem_open().

Signed-off-by: Ilya Dryomov 
Link: http://lkml.kernel.org/r/1320052062-7846-1-git-send-email-idryomov@gmail.com
Signed-off-by: Steven Rostedt 
Signed-off-by: Greg Kroah-Hartman

trace_events_filter: Use rcu_assign_pointer() when setting ftrace_event_call->filter

2011-12-09T16:52:47+00:00

commit d3d9acf646679c1981032b0985b386d12fccc60c upstream.

ftrace_event_call->filter is sched RCU protected but didn't use
rcu_assign_pointer().  Use it.

TODO: Add proper __rcu annotation to call->filter and all its users.

-v2: Use RCU_INIT_POINTER() for %NULL clearing as suggested by Eric.

Link: http://lkml.kernel.org/r/20111123164949.GA29639@google.com

Cc: Eric Dumazet 
Cc: Frederic Weisbecker 
Cc: Jiri Olsa 
Signed-off-by: Tejun Heo 
Signed-off-by: Steven Rostedt 
Signed-off-by: Greg Kroah-Hartman

tracing: Fix returning of duplicate data after EOF in trace_pipe_raw

2011-11-11T17:35:53+00:00

commit 436fc280261dcfce5af38f08b89287750dc91cd2 upstream.

The trace_pipe_raw handler holds a cached page from the time the file
is opened to the time it is closed. The cached page is used to handle
the case of the user space buffer being smaller than what was read from
the ring buffer. The left over buffer is held in the cache so that the
next read will continue where the data left off.

After EOF is returned (no more data in the buffer), the index of
the cached page is set to zero. If a user app reads the page again
after EOF, the check in the buffer will see that the cached page
is less than page size and will return the cached page again. This
will cause reading the trace_pipe_raw again after EOF to return
duplicate data, making the output look like the time went backwards
but instead data is just repeated.

The fix is to not reset the index right after all data is read
from the cache, but to reset it after all data is read and more
data exists in the ring buffer.

Reported-by: Jeremy Eder 
Signed-off-by: Steven Rostedt 
Signed-off-by: Greg Kroah-Hartman

ftrace: Fix regression where ftrace breaks when modules are loaded

2011-10-16T21:14:55+00:00

commit f7bc8b61f65726ff98f52e286b28e294499d7a08 upstream.

Enabling function tracer to trace all functions, then load a module and
then disable function tracing will cause ftrace to fail.

This can also happen by enabling function tracing on the command line:

  ftrace=function

and during boot up, modules are loaded, then you disable function tracing
with 'echo nop > current_tracer' you will trigger a bug in ftrace that
will shut itself down.

The reason is, the new ftrace code keeps ref counts of all ftrace_ops that
are registered for tracing. When one or more ftrace_ops are registered,
all the records that represent the functions that the ftrace_ops will
trace have a ref count incremented. If this ref count is not zero,
when the code modification runs, that function will be enabled for tracing.
If the ref count is zero, that function will be disabled from tracing.

To make sure the accounting was working, FTRACE_WARN_ON()s were added
to updating of the ref counts.

If the ref count hits its max (> 2^30 ftrace_ops added), or if
the ref count goes below zero, a FTRACE_WARN_ON() is triggered which
disables all modification of code.

Since it is common for ftrace_ops to trace all functions in the kernel,
instead of creating > 20,000 hash items for the ftrace_ops, the hash
count is just set to zero, and it represents that the ftrace_ops is
to trace all functions. This is where the issues arrise.

If you enable function tracing to trace all functions, and then add
a module, the modules function records do not get the ref count updated.
When the function tracer is disabled, all function records ref counts
are subtracted. Since the modules never had their ref counts incremented,
they go below zero and the FTRACE_WARN_ON() is triggered.

The solution to this is rather simple. When modules are loaded, and
their functions are added to the the ftrace pool, look to see if any
ftrace_ops are registered that trace all functions. And for those,
update the ref count for the module function records.

Reported-by: Thomas Gleixner 
Signed-off-by: Steven Rostedt

ftrace: Fix regression of :mod:module function enabling

2011-10-16T21:14:55+00:00

commit 43dd61c9a09bd413e837df829e6bfb42159be52a upstream.

The new code that allows different utilities to pick and choose
what functions they trace broke the :mod: hook that allows users
to trace only functions of a particular module.

The reason is that the :mod: hook bypasses the hash that is setup
to allow individual users to trace their own functions and uses
the global hash directly. But if the global hash has not been
set up, it will cause a bug:

echo '*:mod:radeon' > /sys/kernel/debug/set_ftrace_filter

produces:

 [drm:drm_mode_getfb] *ERROR* invalid framebuffer id
 [drm:radeon_crtc_page_flip] *ERROR* failed to reserve new rbo buffer before flip
 BUG: unable to handle kernel paging request at ffffffff8160ec90
 IP: [] add_hash_entry+0x66/0xd0
 PGD 1a05067 PUD 1a09063 PMD 80000000016001e1
 Oops: 0003 [#1] SMP Jul  7 04:02:28 phyllis kernel: [55303.858604] CPU 1
 Modules linked in: cryptd aes_x86_64 aes_generic binfmt_misc rfcomm bnep ip6table_filter hid radeon r8169 ahci libahci mii ttm drm_kms_helper drm video i2c_algo_bit intel_agp intel_gtt

 Pid: 10344, comm: bash Tainted: G        WC  3.0.0-rc5 #1 Dell Inc. Inspiron N5010/0YXXJJ
 RIP: 0010:[]  [] add_hash_entry+0x66/0xd0
 RSP: 0018:ffff88003a96bda8  EFLAGS: 00010246
 RAX: ffff8801301735c0 RBX: ffffffff8160ec80 RCX: 0000000000306ee0
 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff880137c92940
 RBP: ffff88003a96bdb8 R08: ffff880137c95680 R09: 0000000000000000
 R10: 0000000000000001 R11: 0000000000000000 R12: ffffffff81c9df78
 R13: ffff8801153d1000 R14: 0000000000000000 R15: 0000000000000000
 FS: 00007f329c18a700(0000) GS:ffff880137c80000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: ffffffff8160ec90 CR3: 000000003002b000 CR4: 00000000000006e0
 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
 Process bash (pid: 10344, threadinfo ffff88003a96a000, task ffff88012fcfc470)
 Stack:
  0000000000000fd0 00000000000000fc ffff88003a96be38 ffffffff810d92f5
  ffff88011c4c4e00 ffff880000000000 000000000b69f4d0 ffffffff8160ec80
  ffff8800300e6f06 0000000081130295 0000000000000282 ffff8800300e6f00
 Call Trace:
  [] match_records+0x155/0x1b0
  [] ftrace_mod_callback+0xbc/0x100
  [] ftrace_regex_write+0x16f/0x210
  [] ftrace_filter_write+0xf/0x20
  [] vfs_write+0xc8/0x190
  [] sys_write+0x51/0x90
  [] system_call_fastpath+0x16/0x1b
 Code: 48 8b 33 31 d2 48 85 f6 75 33 49 89 d4 4c 03 63 08 49 8b 14 24 48 85 d2 48 89 10 74 04 48 89 42 08 49 89 04 24 4c 89 60 08 31 d2
 RIP [] add_hash_entry+0x66/0xd0
  RSP 
 CR2: ffffffff8160ec90
 ---[ end trace a5d031828efdd88e ]---

Reported-by: Brian Marete 
Signed-off-by: Steven Rostedt 
Signed-off-by: Greg Kroah-Hartman

tracing: Have "enable" file use refcounts like the "filter" file

2011-08-05T04:58:38+00:00

commit 40ee4dffff061399eb9358e0c8fcfbaf8de4c8fe upstream.

The "enable" file for the event system can be removed when a module
is unloaded and the event system only has events from that module.
As the event system nr_events count goes to zero, it may be freed
if its ref_count is also set to zero.

Like the "filter" file, the "enable" file may be opened by a task and
referenced later, after a module has been unloaded and the events for
that event system have been removed.

Although the "filter" file referenced the event system structure,
the "enable" file only references a pointer to the event system
name. Since the name is freed when the event system is removed,
it is possible that an access to the "enable" file may reference
a freed pointer.

Update the "enable" file to use the subsystem_open() routine that
the "filter" file uses, to keep a reference to the event system
structure while the "enable" file is opened.

Reported-by: Johannes Berg 
Signed-off-by: Steven Rostedt 
Signed-off-by: Greg Kroah-Hartman

tracing: Fix bug when reading system filters on module removal

2011-08-05T04:58:38+00:00

commit e9dbfae53eeb9fc3d4bb7da3df87fa9875f5da02 upstream.

The event system is freed when its nr_events is set to zero. This happens
when a module created an event system and then later the module is
removed. Modules may share systems, so the system is allocated when
it is created and freed when the modules are unloaded and all the
events under the system are removed (nr_events set to zero).

The problem arises when a task opened the "filter" file for the
system. If the module is unloaded and it removed the last event for
that system, the system structure is freed. If the task that opened
the filter file accesses the "filter" file after the system has
been freed, the system will access an invalid pointer.

By adding a ref_count, and using it to keep track of what
is using the event system, we can free it after all users
are finished with the event system.

Reported-by: Johannes Berg 
Signed-off-by: Steven Rostedt 
Signed-off-by: Greg Kroah-Hartman

tracing: Fix regression in printk_formats file

2011-06-09T12:42:15+00:00

The fix to fix the printk_formats of modules broke the
printk_formats of trace_printks in the kernel.

The update of what to show via the seq_file was only updated
if the passed in fmt was NULL, which happens only on the first
iteration. The result was showing the first format every time
instead of iterating through the available formats.

Signed-off-by: Steven Rostedt

ftrace: Revert 8ab2b7efd ftrace: Remove unnecessary disabling of irqs

2011-06-07T18:49:19+00:00

Revert the commit that removed the disabling of interrupts around
the initial modifying of mcount callers to nops, and update the comment.

The original comment was outdated and stated that the interrupts were
being disabled to prevent kstop machine, which was required with the
old ftrace daemon, but was no longer the case.

What the comment failed to mention was that interrupts needed to be
disabled to keep interrupts from preempting the modifying of the code
and then executing the code that was partially modified.

Revert the commit and update the comment.

Reported-by: Richard W.M. Jones 
Tested-by: Richard W.M. Jones 
Signed-off-by: Steven Rostedt

kprobes/trace: Fix kprobe selftest for gcc 4.6

2011-06-07T18:47:36+00:00

With gcc 4.6, the self test kprobe function:

 kprobe_trace_selftest_target()

is optimized such that kallsyms does not list it. The kprobes
test uses this function to insert a probe and test it. But
it will fail the test if the function is not listed in kallsyms.

Adding a __used annotation keeps the symbol in the kallsyms table.

Suggested-by: David Daney 
Cc: Masami Hiramatsu 
Signed-off-by: Steven Rostedt