Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 127 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/dev-kmsg b/Documentation/ABI/testing/dev-kmsg
new file mode 100644
index 000000000..a377b6c09
--- /dev/null
+++ b/Documentation/ABI/testing/dev-kmsg
@@ -0,0 +1,127 @@
+What:		/dev/kmsg
+Date:		Mai 2012
+KernelVersion:	3.5
+Contact:	Kay Sievers <kay@vrfy.org>
+Description:	The /dev/kmsg character device node provides userspace access
+		to the kernel's printk buffer.
+
+		Injecting messages:
+
+		Every write() to the opened device node places a log entry in
+		the kernel's printk buffer.
+
+		The logged line can be prefixed with a <N> syslog prefix, which
+		carries the syslog priority and facility. The single decimal
+		prefix number is composed of the 3 lowest bits being the syslog
+		priority and the next 8 bits the syslog facility number.
+
+		If no prefix is given, the priority number is the default kernel
+		log priority and the facility number is set to LOG_USER (1). It
+		is not possible to inject messages from userspace with the
+		facility number LOG_KERN (0), to make sure that the origin of
+		the messages can always be reliably determined.
+
+		Accessing the buffer:
+
+		Every read() from the opened device node receives one record
+		of the kernel's printk buffer.
+
+		The first read() directly following an open() always returns
+		first message in the buffer; there is no kernel-internal
+		persistent state; many readers can concurrently open the device
+		and read from it, without affecting other readers.
+
+		Every read() will receive the next available record. If no more
+		records are available read() will block, or if O_NONBLOCK is
+		used -EAGAIN returned.
+
+		Messages in the record ring buffer get overwritten as whole,
+		there are never partial messages received by read().
+
+		In case messages get overwritten in the circular buffer while
+		the device is kept open, the next read() will return -EPIPE,
+		and the seek position be updated to the next available record.
+		Subsequent reads() will return available records again.
+
+		Unlike the classic syslog() interface, the 64 bit record
+		sequence numbers allow to calculate the amount of lost
+		messages, in case the buffer gets overwritten. And they allow
+		to reconnect to the buffer and reconstruct the read position
+		if needed, without limiting the interface to a single reader.
+
+		The device supports seek with the following parameters:
+
+		SEEK_SET, 0
+		  seek to the first entry in the buffer
+		SEEK_END, 0
+		  seek after the last entry in the buffer
+		SEEK_DATA, 0
+		  seek after the last record available at the time
+		  the last SYSLOG_ACTION_CLEAR was issued.
+
+		Other seek operations or offsets are not supported because of
+		the special behavior this device has. The device allows to read
+		or write only whole variable length messages (records) that are
+		stored in a ring buffer.
+
+		Because of the non-standard behavior also the error values are
+		non-standard. -ESPIPE is returned for non-zero offset. -EINVAL
+		is returned for other operations, e.g. SEEK_CUR. This behavior
+		and values are historical and could not be modified without the
+		risk of breaking userspace.
+
+		The output format consists of a prefix carrying the syslog
+		prefix including priority and facility, the 64 bit message
+		sequence number and the monotonic timestamp in microseconds,
+		and a flag field. All fields are separated by a ','.
+
+		Future extensions might add more comma separated values before
+		the terminating ';'. Unknown fields and values should be
+		gracefully ignored.
+
+		The human readable text string starts directly after the ';'
+		and is terminated by a '\n'. Untrusted values derived from
+		hardware or other facilities are printed, therefore
+		all non-printable characters and '\' itself in the log message
+		are escaped by "\x00" C-style hex encoding.
+
+		A line starting with ' ', is a continuation line, adding
+		key/value pairs to the log message, which provide the machine
+		readable context of the message, for reliable processing in
+		userspace.
+
+		Example::
+
+		  7,160,424069,-;pci_root PNP0A03:00: host bridge window [io  0x0000-0x0cf7] (ignored)
+		   SUBSYSTEM=acpi
+		   DEVICE=+acpi:PNP0A03:00
+		  6,339,5140900,-;NET: Registered protocol family 10
+		  30,340,5690716,-;udevd[80]: starting version 181
+
+		The DEVICE= key uniquely identifies devices the following way:
+
+		  ============  =================
+		  b12:8         block dev_t
+		  c127:3        char dev_t
+		  n8            netdev ifindex
+		  +sound:card0  subsystem:devname
+		  ============  =================
+
+		The flags field carries '-' by default. A 'c' indicates a
+		fragment of a line. Note, that these hints about continuation
+		lines are not necessarily correct, and the stream could be
+		interleaved with unrelated messages, but merging the lines in
+		the output usually produces better human readable results. A
+		similar logic is used internally when messages are printed to
+		the console, /proc/kmsg or the syslog() syscall.
+
+		By default, kernel tries to avoid fragments by concatenating
+		when it can and fragments are rare; however, when extended
+		console support is enabled, the in-kernel concatenation is
+		disabled and /dev/kmsg output will contain more fragments. If
+		the log consumer performs concatenation, the end result
+		should be the same. In the future, the in-kernel concatenation
+		may be removed entirely and /dev/kmsg users are recommended to
+		implement fragment handling.
+
+Users:		dmesg(1), userspace kernel log consumers