Pull tracing fixes and cleanups from Steven Rostedt:
 "This contains a series of last minute clean ups, small fixes and error
  checks"

* tag 'trace-v5.1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  tracing/probe: Verify alloc_trace_*probe() result
  tracing/probe: Check event/group naming rule at parsing
  tracing/probe: Check the size of argument name and body
  tracing/probe: Check event name length correctly
  tracing/probe: Check maxactive error cases
  tracing: kdb: Fix ftdump to not sleep
  trace/probes: Remove kernel doc style from non kernel doc comment
  tracing/probes: Make reserved_field_names static

As reported back in 2016-11 [1], the "ftdump" kdb command triggers a
BUG for "sleeping function called from invalid context".

kdb's "ftdump" command wants to call ring_buffer_read_prepare() in
atomic context.  A very simple solution for this is to add allocation
flags to ring_buffer_read_prepare() so kdb can call it without
triggering the allocation error.  This patch does that.

Note that in the original email thread about this, it was suggested
that perhaps the solution for kdb was to either preallocate the buffer
ahead of time or create our own iterator.  I'm hoping that this
alternative of adding allocation flags to ring_buffer_read_prepare()
can be considered since it means I don't need to duplicate more of the
core trace code into "trace_kdb.c" (for either creating my own
iterator or re-preparing a ring allocator whose memory was already
allocated).

NOTE: another option for kdb is to actually figure out how to make it
reuse the existing ftrace_dump() function and totally eliminate the
duplication.  This sounds very appealing and actually works (the "sr
z" command can be seen to properly dump the ftrace buffer).  The
downside here is that ftrace_dump() fully consumes the trace buffer.
Unless that is changed I'd rather not use it because it means "ftdump
| grep xyz" won't be very useful to search the ftrace buffer since it
will throw away the whole trace on the first grep.  A future patch to
dump only the last few lines of the buffer will also be hard to
implement.

[1] https://lkml.kernel.org/r/20161117191605.GA21459@google.com

Link: http://lkml.kernel.org/r/20190308193205.213659-1-dianders@chromium.org

Reported-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

Pull misc vfs updates from Al Viro:
 "Assorted fixes (really no common topic here)"

* 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  vfs: Make __vfs_write() static
  vfs: fix preadv64v2 and pwritev64v2 compat syscalls with offset == -1
  pipe: stop using ->can_merge
  splice: don't merge into linked buffers
  fs: move generic stat response attr handling to vfs_getattr_nosec
  orangefs: don't reinitialize result_mask in ->getattr
  fs/devpts: always delete dcache dentry-s in dput()

Pull tracing updates from Steven Rostedt:
 "The biggest change for this release is in the histogram code:

   - Add "onchange(var)" histogram handler that executes a action when
     $var changes.

   - Add new "snapshot()" action for histogram handlers, that causes a
     snapshot of the ring buffer when triggered. ie.
     onchange(var).snapshot() will trigger a snapshot if var changes.

   - Add alternative for "trace()" action. Currently, to trigger a
     synthetic event, the name of that event is used as the handler
     name, which is inconsistent with the other actions.
     onchange(var).synthetic(param) where it can now be
     onchange(var).trace(synthetic, param). The older method will still
     be allowed, as long as the synthetic events do not overlap with
     other handler names.

   - The histogram documentation at testcases were updated for the new
     changes.

  Outside of the histogram code, we have:

   - Added a quicker way to enable set_ftrace_filter files, that will
     make it much quicker to bisect tracing a function that shouldn't be
     traced and crashes the kernel. (You can echo in numbers to
     set_ftrace_filter, and it will select the corresponding function
     that is in available_filter_functions).

   - Some better displaying of the tracing data (and more information
     was added).

  The rest are small fixes and more clean ups to the code"

* tag 'trace-v5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (37 commits)
  tracing: Use strncpy instead of memcpy when copying comm in trace.c
  tracing: Use strncpy instead of memcpy when copying comm for hist triggers
  tracing: Use strncpy instead of memcpy for string keys in hist triggers
  tracing: Use str_has_prefix() in synth_event_create()
  x86/ftrace: Fix warning and considate ftrace_jmp_replace() and ftrace_call_replace()
  tracing/perf: Use strndup_user() instead of buggy open-coded version
  doc: trace: Fix documentation for uprobe_profile
  tracing: Fix spelling mistake: "analagous" -> "analogous"
  tracing: Comment why cond_snapshot is checked outside of max_lock protection
  tracing: Add hist trigger action 'expected fail' test case
  tracing: Add alternative synthetic event trace action test case
  tracing: Add hist trigger onchange() handler test case
  tracing: Add hist trigger snapshot() action test case
  tracing: Add SPDX license GPL-2.0 license identifier to inter-event testcases
  tracing: Add alternative synthetic event trace action syntax
  tracing: Add hist trigger onchange() handler Documentation
  tracing: Add hist trigger onchange() handler
  tracing: Add hist trigger snapshot() action Documentation
  tracing: Add hist trigger snapshot() action
  tracing: Add conditional snapshot
  ...

Because there may be random garbage beyond a string's null terminator,
code that might use the entire comm array e.g. histogram keys, can
give unexpected results if that garbage is copied in too, so avoid
that possibility by using strncpy instead of memcpy.

Link: http://lkml.kernel.org/r/1d6ebac26570c2a29ce9fb575379f17ef5c8b81b.1551802084.git.tom.zanussi@linux.intel.com

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

There is a spelling mistake in the mini-howto help text. Fix it.

Link: http://lkml.kernel.org/r/20190217223222.16479-1-colin.king@canonical.com

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

Before setting tr->cond_snapshot, it must be NULL before it can be updated.
It can go to NULL when a trace event hist trigger is created or removed, and
can only be modified under the max_lock spin lock. But because it can only
be set to something other than NULL under both the max_lock spin lock as
well as the trace_types_lock, we can perform the check if it is not NULL
only under the trace_types_lock and fail out without having to grab the
max_lock spin lock.

This is very subtle, and deserves a comment.

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

Add a 'trace(synthetic_event_name, params)' alternative to
synthetic_event_name(params).

Currently, the syntax used for generating synthetic events is to
invoke synthetic_event_name(params) i.e. use the synthetic event name
as a function call.

Users requested a new form that more explicitly shows that the
synthetic event is in effect being traced.  In this version, a new
'trace()' keyword is used, and the synthetic event name is passed in
as the first argument.

In addition, for the sake of consistency with other actions, change
the documention to emphasize the trace() form over the function-call
form, which remains documented as equivalent.

Link: http://lkml.kernel.org/r/d082773e50232a001480cf837679a1e01c1a2eb7.1550100284.git.tom.zanussi@linux.intel.com

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

Add support for a hist:onchange($var) handler, similar to the onmax()
handler but triggering whenever there's any change in $var, not just a
max.

Link: http://lkml.kernel.org/r/dfbc7e4ada242603e9ec3f049b5ad076a07dfd03.1550100284.git.tom.zanussi@linux.intel.com

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

Add support for hist:handlerXXX($var).snapshot(), which will take a
snapshot of the current trace buffer whenever handlerXXX is hit.

As a first user, this also adds snapshot() action support for the
onmax() handler i.e. hist:onmax($var).snapshot().

Also, the hist trigger key printing is moved into a separate function
so the snapshot() action can print a histogram key outside the
histogram display - add and use hist_trigger_print_key() for that
purpose.

Link: http://lkml.kernel.org/r/2f1a952c0dcd8aca8702ce81269581a692396d45.1550100284.git.tom.zanussi@linux.intel.com

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