linux-toradex.git/kernel/trace, branch v2.6.33.1

tracing: Fix ftrace_event_call alignment for use with gcc 4.5

2010-03-15T16:06:17+00:00

commit 86c38a31aa7f2dd6e74a262710bf8ebf7455acc5 upstream.

GCC 4.5 introduces behavior that forces the alignment of structures to
 use the largest possible value. The default value is 32 bytes, so if
 some structures are defined with a 4-byte alignment and others aren't
 declared with an alignment constraint at all - it will align at 32-bytes.

 For things like the ftrace events, this results in a non-standard array.
 When initializing the ftrace subsystem, we traverse the _ftrace_events
 section and call the initialization callback for each event. When the
 structures are misaligned, we could be treating another part of the
 structure (or the zeroed out space between them) as a function pointer.

 This patch forces the alignment for all the ftrace_event_call structures
 to 4 bytes.

 Without this patch, the kernel fails to boot very early when built with
 gcc 4.5.

 It's trivial to check the alignment of the members of the array, so it
 might be worthwhile to add something to the build system to do that
 automatically. Unfortunately, that only covers this case. I've asked one
 of the gcc developers about adding a warning when this condition is seen.

Signed-off-by: Jeff Mahoney 
LKML-Reference: <4B85770B.6010901@suse.com>
Signed-off-by: Steven Rostedt 
Signed-off-by: Greg Kroah-Hartman

tracing/kprobes: Fix probe parsing

2010-02-14T08:43:58+00:00

Trying to add a probe like:

  echo p:myprobe 0x10000 > /sys/kernel/debug/tracing/kprobe_events

will fail since the wrong pointer is passed to strict_strtoul
when trying to convert the address to an unsigned long.

Signed-off-by: Heiko Carstens 
Acked-by: Masami Hiramatsu 
Cc: Frederic Weisbecker 
Cc: Steven Rostedt 
LKML-Reference: <20100210162346.GA6933@osiris.boeblingen.de.ibm.com>
Signed-off-by: Ingo Molnar

tracing: Fix circular dead lock in stack trace

2010-02-02T15:20:18+00:00

When we cat /tracing/stack_trace, we may cause circular lock:
sys_read()
  t_start()
     arch_spin_lock(&max_stack_lock);

  t_show()
     seq_printf(), vsnprintf() .... /* they are all trace-able,
       when they are traced, max_stack_lock may be required again. */

The following script can trigger this circular dead lock very easy:
#!/bin/bash

echo 1 > /proc/sys/kernel/stack_tracer_enabled

mount -t debugfs xxx /mnt > /dev/null 2>&1

(
# make check_stack() zealous to require max_stack_lock
for ((; ;))
{
	echo 1 > /mnt/tracing/stack_max_size
}
) &

for ((; ;))
{
	cat /mnt/tracing/stack_trace > /dev/null
}

To fix this bug, we increase the percpu trace_active before
require the lock.

Reported-by: Li Zefan 
Signed-off-by: Lai Jiangshan 
LKML-Reference: <4B67D4F9.9080905@cn.fujitsu.com>
Signed-off-by: Steven Rostedt

tracing/documentation: Cover new frame pointer semantics

2010-01-26T22:00:39+00:00

Update the graph tracer examples to cover the new frame pointer semantics
(in terms of passing it along).  Move the HAVE_FUNCTION_GRAPH_FP_TEST docs
out of the Kconfig, into the right place, and expand on the details.

Signed-off-by: Mike Frysinger 
LKML-Reference: <1264165967-18938-1-git-send-email-vapier@gentoo.org>
Signed-off-by: Steven Rostedt

ring-buffer: Check for end of page in iterator

2010-01-26T21:14:08+00:00

If the iterator comes to an empty page for some reason, or if
the page is emptied by a consuming read. The iterator code currently
does not check if the iterator is pass the contents, and may
return a false entry.

This patch adds a check to the ring buffer iterator to test if the
current page has been completely read and sets the iterator to the
next page if necessary.

Signed-off-by: Steven Rostedt

ring-buffer: Check if ring buffer iterator has stale data

2010-01-26T21:09:30+00:00

Usually reads of the ring buffer is performed by a single task.
There are two types of reads from the ring buffer.

One is a consuming read which will consume the entry that was read
and the next read will be the entry that follows.

The other is an iterator that will let the user read the contents of
the ring buffer without modifying it. When an iterator is allocated,
writes to the ring buffer are disabled to protect the iterator.

The problem exists when consuming reads happen while an iterator is
allocated. Specifically, the kind of read that swaps out an entire
page (used by splice) and replaces it with a new read. If the iterator
is on the page that is swapped out, then the next read may read
from this swapped out page and return garbage.

This patch adds a check when reading the iterator to make sure that
the iterator contents are still valid. If a consuming read has taken
place, the iterator is reset.

Signed-off-by: Steven Rostedt

tracing: Prevent kernel oops with corrupted buffer

2010-01-25T20:11:53+00:00

If the contents of the ftrace ring buffer gets corrupted and the trace
file is read, it could create a kernel oops (usualy just killing the user
task thread). This is caused by the checking of the pid in the buffer.
If the pid is negative, it still references the cmdline cache array,
which could point to an invalid address.

The simple fix is to test for negative PIDs.

Signed-off-by: Steven Rostedt

tracing/filters: Add comment for match callbacks

2010-01-15T03:38:14+00:00

We should be clear on 2 things:

- the length parameter of a match callback includes
  tailing '\0'.

- the string to be searched might not be NULL-terminated.

Signed-off-by: Li Zefan 
LKML-Reference: <4B4E8770.7000608@cn.fujitsu.com>
Signed-off-by: Steven Rostedt

tracing/filters: Fix MATCH_FULL filter matching for PTR_STRING

2010-01-15T03:38:12+00:00

MATCH_FULL matching for PTR_STRING is not working correctly:

  # echo 'func == vt' > events/bkl/lock_kernel/filter
  # echo 1 > events/bkl/lock_kernel/enable
  ...
  # cat trace
   Xorg-1484  [000]  1973.392586: lock_kernel: ... func=vt_ioctl()
    gpm-1402  [001]  1974.027740: lock_kernel: ... func=vt_ioctl()

We should pass to regex.match(..., len) the length (including '\0')
of the source string instead of the length of the pattern string.

Signed-off-by: Li Zefan 
LKML-Reference: <4B4E8763.5070707@cn.fujitsu.com>
Acked-by: Frederic Weisbecker 
Signed-off-by: Steven Rostedt

tracing/filters: Fix MATCH_MIDDLE_ONLY filter matching

2010-01-15T03:38:11+00:00

The @str might not be NULL-terminated if it's of type
DYN_STRING or STATIC_STRING, so we should use strnstr()
instead of strstr().

Signed-off-by: Li Zefan 
LKML-Reference: <4B4E8753.2000102@cn.fujitsu.com>
Acked-by: Frederic Weisbecker 
Signed-off-by: Steven Rostedt