commit 8b8b36834d0fff67fc8668093f4312dd04dcf21d upstream.

The per_cpu buffers are created one per possible CPU. But these do
not mean that those CPUs are online, nor do they even exist.

With the addition of the ring buffer polling, it assumes that the
caller polls on an existing buffer. But this is not the case if
the user reads trace_pipe from a CPU that does not exist, and this
causes the kernel to crash.

Simple fix is to check the cpu against buffer bitmask against to see
if the buffer was allocated or not and return -ENODEV if it is
not.

More updates were done to pass the -ENODEV back up to userspace.

Link: http://lkml.kernel.org/r/5393DB61.6060707@oracle.com

Reported-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit 099ed151675cd1d2dbeae1dac697975f6a68716d upstream.

Disabling reading and writing to the trace file should not be able to
disable all function tracing callbacks. There's other users today
(like kprobes and perf). Reading a trace file should not stop those
from happening.

Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit 379cfdac37923653c9d4242d10052378b7563005 upstream.

In order to prevent the saved cmdline cache from being filled when
tracing is not active, the comms are only recorded after a trace event
is recorded.

The problem is, a comm can fail to be recorded if the trace_cmdline_lock
is held. That lock is taken via a trylock to allow it to happen from
any context (including NMI). If the lock fails to be taken, the comm
is skipped. No big deal, as we will try again later.

But! Because of the code that was added to only record after an event,
we may not try again later as the recording is made as a oneshot per
event per CPU.

Only disable the recording of the comm if the comm is actually recorded.

Fixes: 7ffbd48d5cab "tracing: Cache comms only after an event occurred"
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

While working on my tutorial for 2014 Linux Collaboration Summit
I found that the traceon trigger did not work when conditions were
used. The other triggers worked fine though. Looking into it, it
is because of the way the triggers use the ring buffer to store
the fields it will use for the condition. But if tracing is off, nothing
is stored in the buffer, and the tracepoint exits before calling the
trigger to test the condition. This is fine for all the triggers that
only work when tracing is on, but for traceon trigger that is to
work when tracing is off, nothing happens.

The fix is simple, just use a temp ring buffer to record the event
if tracing is off and the event has a trace event conditional trigger
enabled. The rest of the tracepoint code will work just fine, but
the tracepoint wont be recorded in the other buffers.

Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

If trace_puts() is used very early in boot up, it can crash the machine
if it is called before the ring buffer is allocated. If a trace_printk()
is used with no arguments, then it will be converted into a trace_puts()
and suffer the same fate.

Cc: stable@vger.kernel.org # 3.10+
Fixes: 09ae72348ecc "tracing: Add trace_puts() for even faster trace_printk() tracing"
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

Fix the formatting of the README file in the trace debugfs to fit in
an 80 character window.

Also add a comment about the event trigger counter with regards to
traceon and traceoff.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

It would be useful to have a cheat-sheet for everything under
tracing/events/ alongside the existing text describing the other files
in the tracing/ dir.

Add short descriptions of the directories and files under events/
along with examples, similar to the existing text for the other files
in tracing/.

Also clean up a few minor alignment problems noticed when adding the
new text.

Link: http://lkml.kernel.org/r/1389993104.3040.445.camel@empanada

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

In kernel/trace/trace.c we have this:
static void tracing_pipe_buf_release(struct pipe_inode_info *pipe,
                                     struct pipe_buffer *buf)
{
        __free_page(buf->page);
}
static const struct pipe_buf_operations tracing_pipe_buf_ops = {
        .can_merge              = 0,
        .map                    = generic_pipe_buf_map,
        .unmap                  = generic_pipe_buf_unmap,
        .confirm                = generic_pipe_buf_confirm,
        .release                = tracing_pipe_buf_release,
        .steal                  = generic_pipe_buf_steal,
        .get                    = generic_pipe_buf_get,
};
with
void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
{
        page_cache_get(buf->page);
}

and I don't see anything that would've prevented tee(2) called on the pipe
that got stuff spliced into it from that sucker.  ->ops->get() will be
called, then buf gets copied into target pipe's ->bufs[] and eventually
readers get to both copies of the buffer.  With
	get_page(page)
	look at that page
	__free_page(page)
	look at that page
	__free_page(page)
which is not a good thing, to put it mildly.  AFAICS, that ought to use
the normal generic_pipe_buf_release() (aka page_cache_release(buf->page)),
shouldn't it?

[
 SDR - As trace_pipe just allocates the page with alloc_page(GFP_KERNEL),
  and doesn't do anything special with it (no LRU logic). The __free_page()
  should be fine, as it wont actually free a page with reference count.
  Maybe there's a chance to leak memory? Anyway, This change is at a minimum
  good for being symmetric with generic_pipe_buf_get, it is fine to add.
]

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
[ SDR - Removed no longer used tracing_pipe_buf_release ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

The trace buffer has a descriptor pointer that goes back to the trace
array. But it was never assigned. Luckily, nothing uses it (yet), but
it will in the future.

Although nothing currently uses this, if any of the new features get
backported to older kernels, and because this is such a simple change,
I'm marking it for stable too.

Cc: stable@vger.kernel.org # v3.10+
Fixes: 12883efb670c "tracing: Consolidate max_tr into main trace_array structure"
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

Trace event triggers added a lseek that uses the ftrace_filter_lseek()
function. Unfortunately, when function tracing is not configured in
that function is not defined and the kernel fails to build.

This is the second time that function was added to a file ops and
it broke the build due to requiring special config dependencies.

Make a generic tracing_lseek() that all the tracing utilities may
use.

Also, modify the old ftrace_filter_lseek() to return 0 instead of
1 on WRONLY. Not sure why it was a 1 as that does not make sense.

This also changes the old tracing_seek() to modify the file pos
pointer on WRONLY as well.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Tested-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Acked-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>