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, 193 insertions, 0 deletions

diff --git a/Documentation/hid/uhid.rst b/Documentation/hid/uhid.rst
new file mode 100644
index 000000000..2243a6b75
--- /dev/null
+++ b/Documentation/hid/uhid.rst
@@ -0,0 +1,193 @@
+======================================================
+UHID - User-space I/O driver support for HID subsystem
+======================================================
+
+UHID allows user-space to implement HID transport drivers. Please see
+hid-transport.rst for an introduction into HID transport drivers. This document
+relies heavily on the definitions declared there.
+
+With UHID, a user-space transport driver can create kernel hid-devices for each
+device connected to the user-space controlled bus. The UHID API defines the I/O
+events provided from the kernel to user-space and vice versa.
+
+There is an example user-space application in ./samples/uhid/uhid-example.c
+
+The UHID API
+------------
+
+UHID is accessed through a character misc-device. The minor number is allocated
+dynamically so you need to rely on udev (or similar) to create the device node.
+This is /dev/uhid by default.
+
+If a new device is detected by your HID I/O Driver and you want to register this
+device with the HID subsystem, then you need to open /dev/uhid once for each
+device you want to register. All further communication is done by read()'ing or
+write()'ing "struct uhid_event" objects. Non-blocking operations are supported
+by setting O_NONBLOCK::
+
+  struct uhid_event {
+        __u32 type;
+        union {
+                struct uhid_create2_req create2;
+                struct uhid_output_req output;
+                struct uhid_input2_req input2;
+                ...
+        } u;
+  };
+
+The "type" field contains the ID of the event. Depending on the ID different
+payloads are sent. You must not split a single event across multiple read()'s or
+multiple write()'s. A single event must always be sent as a whole. Furthermore,
+only a single event can be sent per read() or write(). Pending data is ignored.
+If you want to handle multiple events in a single syscall, then use vectored
+I/O with readv()/writev().
+The "type" field defines the payload. For each type, there is a
+payload-structure available in the union "u" (except for empty payloads). This
+payload contains management and/or device data.
+
+The first thing you should do is send a UHID_CREATE2 event. This will
+register the device. UHID will respond with a UHID_START event. You can now
+start sending data to and reading data from UHID. However, unless UHID sends the
+UHID_OPEN event, the internally attached HID Device Driver has no user attached.
+That is, you might put your device asleep unless you receive the UHID_OPEN
+event. If you receive the UHID_OPEN event, you should start I/O. If the last
+user closes the HID device, you will receive a UHID_CLOSE event. This may be
+followed by a UHID_OPEN event again and so on. There is no need to perform
+reference-counting in user-space. That is, you will never receive multiple
+UHID_OPEN events without a UHID_CLOSE event. The HID subsystem performs
+ref-counting for you.
+You may decide to ignore UHID_OPEN/UHID_CLOSE, though. I/O is allowed even
+though the device may have no users.
+
+If you want to send data on the interrupt channel to the HID subsystem, you send
+a HID_INPUT2 event with your raw data payload. If the kernel wants to send data
+on the interrupt channel to the device, you will read a UHID_OUTPUT event.
+Data requests on the control channel are currently limited to GET_REPORT and
+SET_REPORT (no other data reports on the control channel are defined so far).
+Those requests are always synchronous. That means, the kernel sends
+UHID_GET_REPORT and UHID_SET_REPORT events and requires you to forward them to
+the device on the control channel. Once the device responds, you must forward
+the response via UHID_GET_REPORT_REPLY and UHID_SET_REPORT_REPLY to the kernel.
+The kernel blocks internal driver-execution during such round-trips (times out
+after a hard-coded period).
+
+If your device disconnects, you should send a UHID_DESTROY event. This will
+unregister the device. You can now send UHID_CREATE2 again to register a new
+device.
+If you close() the fd, the device is automatically unregistered and destroyed
+internally.
+
+write()
+-------
+write() allows you to modify the state of the device and feed input data into
+the kernel. The kernel will parse the event immediately and if the event ID is
+not supported, it will return -EOPNOTSUPP. If the payload is invalid, then
+-EINVAL is returned, otherwise, the amount of data that was read is returned and
+the request was handled successfully. O_NONBLOCK does not affect write() as
+writes are always handled immediately in a non-blocking fashion. Future requests
+might make use of O_NONBLOCK, though.
+
+UHID_CREATE2:
+  This creates the internal HID device. No I/O is possible until you send this
+  event to the kernel. The payload is of type struct uhid_create2_req and
+  contains information about your device. You can start I/O now.
+
+UHID_DESTROY:
+  This destroys the internal HID device. No further I/O will be accepted. There
+  may still be pending messages that you can receive with read() but no further
+  UHID_INPUT events can be sent to the kernel.
+  You can create a new device by sending UHID_CREATE2 again. There is no need to
+  reopen the character device.
+
+UHID_INPUT2:
+  You must send UHID_CREATE2 before sending input to the kernel! This event
+  contains a data-payload. This is the raw data that you read from your device
+  on the interrupt channel. The kernel will parse the HID reports.
+
+UHID_GET_REPORT_REPLY:
+  If you receive a UHID_GET_REPORT request you must answer with this request.
+  You  must copy the "id" field from the request into the answer. Set the "err"
+  field to 0 if no error occurred or to EIO if an I/O error occurred.
+  If "err" is 0 then you should fill the buffer of the answer with the results
+  of the GET_REPORT request and set "size" correspondingly.
+
+UHID_SET_REPORT_REPLY:
+  This is the SET_REPORT equivalent of UHID_GET_REPORT_REPLY. Unlike GET_REPORT,
+  SET_REPORT never returns a data buffer, therefore, it's sufficient to set the
+  "id" and "err" fields correctly.
+
+read()
+------
+read() will return a queued output report. No reaction is required to any of
+them but you should handle them according to your needs.
+
+UHID_START:
+  This is sent when the HID device is started. Consider this as an answer to
+  UHID_CREATE2. This is always the first event that is sent. Note that this
+  event might not be available immediately after write(UHID_CREATE2) returns.
+  Device drivers might require delayed setups.
+  This event contains a payload of type uhid_start_req. The "dev_flags" field
+  describes special behaviors of a device. The following flags are defined:
+
+      - UHID_DEV_NUMBERED_FEATURE_REPORTS
+      - UHID_DEV_NUMBERED_OUTPUT_REPORTS
+      - UHID_DEV_NUMBERED_INPUT_REPORTS
+
+          Each of these flags defines whether a given report-type uses numbered
+          reports. If numbered reports are used for a type, all messages from
+          the kernel already have the report-number as prefix. Otherwise, no
+          prefix is added by the kernel.
+          For messages sent by user-space to the kernel, you must adjust the
+          prefixes according to these flags.
+
+UHID_STOP:
+  This is sent when the HID device is stopped. Consider this as an answer to
+  UHID_DESTROY.
+
+  If you didn't destroy your device via UHID_DESTROY, but the kernel sends an
+  UHID_STOP event, this should usually be ignored. It means that the kernel
+  reloaded/changed the device driver loaded on your HID device (or some other
+  maintenance actions happened).
+
+  You can usually ignore any UHID_STOP events safely.
+
+UHID_OPEN:
+  This is sent when the HID device is opened. That is, the data that the HID
+  device provides is read by some other process. You may ignore this event but
+  it is useful for power-management. As long as you haven't received this event
+  there is actually no other process that reads your data so there is no need to
+  send UHID_INPUT2 events to the kernel.
+
+UHID_CLOSE:
+  This is sent when there are no more processes which read the HID data. It is
+  the counterpart of UHID_OPEN and you may as well ignore this event.
+
+UHID_OUTPUT:
+  This is sent if the HID device driver wants to send raw data to the I/O
+  device on the interrupt channel. You should read the payload and forward it to
+  the device. The payload is of type "struct uhid_output_req".
+  This may be received even though you haven't received UHID_OPEN yet.
+
+UHID_GET_REPORT:
+  This event is sent if the kernel driver wants to perform a GET_REPORT request
+  on the control channel as described in the HID specs. The report-type and
+  report-number are available in the payload.
+  The kernel serializes GET_REPORT requests so there will never be two in
+  parallel. However, if you fail to respond with a UHID_GET_REPORT_REPLY, the
+  request might silently time out.
+  Once you read a GET_REPORT request, you shall forward it to the HID device and
+  remember the "id" field in the payload. Once your HID device responds to the
+  GET_REPORT (or if it fails), you must send a UHID_GET_REPORT_REPLY to the
+  kernel with the exact same "id" as in the request. If the request already
+  timed out, the kernel will ignore the response silently. The "id" field is
+  never re-used, so conflicts cannot happen.
+
+UHID_SET_REPORT:
+  This is the SET_REPORT equivalent of UHID_GET_REPORT. On receipt, you shall
+  send a SET_REPORT request to your HID device. Once it replies, you must tell
+  the kernel about it via UHID_SET_REPORT_REPLY.
+  The same restrictions as for UHID_GET_REPORT apply.
+
+----------------------------------------------------
+
+Written 2012, David Herrmann <dh.herrmann@gmail.com>