Merge tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Don't destroy user event fields when removal fails

   User event fields are destroyed before the event is removed from
   visibility. But that can fail leaving the still visible event with no
   fields. Move the destroying of the fields to after the event is
   successfully removed from visibility.

 - Initialize function graph state is fork before calling
   copy_exec_state()

   For non-CLONE_VM forks, copy_exec_state() allocates a new
   task_exec_state. If that allocation fails, ftrace_graph_exit_task()
   will free the tasks ret_stack pointer. Since that pointer is still
   using the parent's ret_stack, it mistakenly frees the parent's
   pointer too.

   Call ftrace_graph_init() on the task first which will NULL out the
   new tasks's ret_stack and if the copy fails, it will not free
   anything.

 - Remove FGRAPH_MAX_INDEX

   The macro FGRAPH_MAX_INDEX was added but never used. Remove it.

 - Save ent_size in function graph printing of nested functions

   The function graph tracer needs to look at the next event to see if
   the next event is the return of the current function entry. If it is,
   it prints a single line:

	ktime_get();

   Otherwise it prints it like a nested function:

	tick_nohz_irq_exit() {
	    ktime_get();
	    kcpustat_irq_exit();
	}

   In order to look at the next event, it must save the current event so
   that it has the information to print from it. It saves the event in
   the iterator descriptor called "ent". What it doesn't save is the
   ent_size of the event which is now used to know if the function graph
   arguments are to be printed. The peek doesn't save the size so the
   size used happens to be that of the size of the last event that was
   seen.

   Save the entry event size in the iterator descriptor so that the
   correct size is used.

 - Fix several errors with freeing data in the histogram code

   The histogram code had a lot of leaked or or incorrect accounting
   when failures happen. Correct them.

 - Fix histogram regression of .percent and .graph modifiers

   Up until 6.3 histogram values could have "percent" or "graph"
   modifiers that changed how they were printed. But a change that added
   restricting histograms values from being strings, stack traces and
   other modifiers inadvertently prevented them from using the percent
   and graph modifiers, which were legal use cases for values.

   Put back the percent and graph modifiers.

 - Fix various typos in the comments

 - Set the trace_clock before initializing a histogram with clock
   argument

   The histogram API allows the user to specific which trace clock to
   use via a "clock=" string. The histogram is set up first before the
   clock is checked. If the passed in clock is not valid, it exits
   without fully fixing up the histogram leaving it on the list and a
   use-after-free can trigger.

   Update the clock argument first and if it fails then exit gracefully
   before the histogram trigger is placed on any lists.

 - Restore :mod: trailer after parsing in ftrace_set_clr_event

   The function ftrace_set_clr_event() modifies the parse string and
   needs to put it back to what was passed in. It searches for ":mod:"
   via a strsep() but fails to put back the first ':' in the string.

   Add back the ':' in the passed in string.

 - Take trace_array reference when opening a tracer options file

   The options files are dynamically created and some tracers add their
   own options. When a tracer adds their own list of options, the
   trace_array holding them has an array to hold the list of options for
   each tracer. This array increases in size via a krealloc(), and the
   new entry gets a newly allocated array to hold the options of the new
   tracer being added.

   The element in each entry of the tracer's option array holds a
   pointer back to the trace_array, a pointer to the tracer it is
   associated to, a pointer to the flags of the option.

   The issue is that these arrays are freed when the trace_array is
   freed when its instance it represents is removed from the instances
   directory. There's a race that an open of one of these options files
   can happen when the instance is being removed.

   Add a new helper function to be called by the open function of the
   options file to iterate all existing trace_arrays under a lock and
   find the one that has the given option element in one of it's tracer
   arrays. If found, then update the associated trace_array's reference
   counter to keep it from being freed. If not found, have the open call
   return -ENODEV.

 - Disable interrupts when acquiring the lock in rb_wake_up_waiters()

   The function rb_wake_up_waiters() assumes it will be called in
   interrupt context and does not disable irqs when taking
   cpu_buffer->reader_lock, which can be called in hard interrupt
   context. The issue is in PREEMPT_RT, this function is called in
   thread context leaving this lock open to a deadlock.

   Take the lock with interrupts disabled.

 - Use rcu_assign_pointer() for tmp_ops filter hash

   The tmp_ops used in update_ftrace_direct_mod() assigns its
   filter_hash field directly, but that field is annotated as __rcu and
   sparse complains. Assign it with rcu_assign_pointer()

 - Fix use-after-free in enable_trigger_private_data_free()

   The trace_event_call is accessed through the event_trigger_data's
   trace_event_file pointer to put the trace_event_call on freeing. The
   issue is that the trace_event_file data may have been freed already
   causing a use-after-free. Add a field to the event_trigger_data that
   points directly to the trace_event_call so that it can decrement its
   reference directly without needing to go through the
   trace_event_file.

 - Fix accounting of buffer data remote headers

   trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount
   the number of pages is needed for the asked for size as it doesn't
   take into account the meta data on each page. Add a helper function
   to do the calculation properly and use that in these functions.

 - Catch nr_page_va overflow in ring_buffer_desc sizing

   The number of pages per remote ring buffer is capped by
   ring_buffer_desc::nr_page_va (32 bits). A buffer_size large enough to
   overflow that field would silently allocate a descriptor smaller than
   what was asked for.

 - Do not resize the subbuf order if any per_cpu buffer is disabled

   The mmapping of ring buffers disables resizing the subbuffers, but it
   is done per-cpu whereas the subbuf size change is done for all the
   per_cpu buffers under the buffer->mutex. It could change the size of
   some while the mapping is happening on others. Have the resize of the
   subbuf order check all the per_cpu buffers under the lock to see if
   any of them is disabled before starting and causing an inconsistency
   between buffers that are being mapped.

* tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (25 commits)
  ring-buffer: Check resize_disabled before publishing the new subbuf order
  tracing/remotes: Catch nr_page_va overflow in ring_buffer_desc sizing
  tracing/remotes: Account for ring buffer page header in size calculation
  tracing: Don't dereference trace_event_file in deferred trigger free
  ftrace: Use rcu_assign_pointer() for tmp_ops filter hash
  ring-buffer: Acquire the lock with irqsave in rb_wake_up_waiters()
  tracing: Take trace_array reference when opening a tracer options file
  tracing: Fix ring_buffer_read_page_size() kernel-doc
  tracing: Restore :mod: trailer after parsing in ftrace_set_clr_event()
  tracing: Fix memory corruption from a "STACKTRACE" histogram key
  tracing: Fix memory corruption from the histogram stacktrace modifier
  tracing: Undo the registration when enabling the histogram trigger fails
  tracing: Take the reference before publishing the named histogram trigger
  tracing: Set the trace clock before registering the histogram trigger
  tracing: Fix typo "preceeded" in comment
  tracing: Fix typo "availabe" in comment
  tracing: Let histogram values keep the percent and graph modifiers
  tracing: Keep the entry count when the histogram stats allocation fails
  tracing: Free histogram the field rejected for a bad modifier
  tracing: Free histogram the var ref when its initialization fails
  ...

1 files changed, 154 insertions, 0 deletions

diff --git a/Documentation/driver-api/usb/hotplug.rst b/Documentation/driver-api/usb/hotplug.rst
new file mode 100644
index 000000000..12260f704
--- /dev/null
+++ b/Documentation/driver-api/usb/hotplug.rst
@@ -0,0 +1,154 @@
+USB hotplugging
+~~~~~~~~~~~~~~~
+
+Linux Hotplugging
+=================
+
+
+In hotpluggable buses like USB (and Cardbus PCI), end-users plug devices
+into the bus with power on.  In most cases, users expect the devices to become
+immediately usable.  That means the system must do many things, including:
+
+    - Find a driver that can handle the device.  That may involve
+      loading a kernel module; newer drivers can use module-init-tools
+      to publish their device (and class) support to user utilities.
+
+    - Bind a driver to that device.  Bus frameworks do that using a
+      device driver's probe() routine.
+
+    - Tell other subsystems to configure the new device.  Print
+      queues may need to be enabled, networks brought up, disk
+      partitions mounted, and so on.  In some cases these will
+      be driver-specific actions.
+
+This involves a mix of kernel mode and user mode actions.  Making devices
+be immediately usable means that any user mode actions can't wait for an
+administrator to do them:  the kernel must trigger them, either passively
+(triggering some monitoring daemon to invoke a helper program) or
+actively (calling such a user mode helper program directly).
+
+Those triggered actions must support a system's administrative policies;
+such programs are called "policy agents" here.  Typically they involve
+shell scripts that dispatch to more familiar administration tools.
+
+Because some of those actions rely on information about drivers (metadata)
+that is currently available only when the drivers are dynamically linked,
+you get the best hotplugging when you configure a highly modular system.
+
+Kernel Hotplug Helper (``/sbin/hotplug``)
+=========================================
+
+There is a kernel parameter: ``/proc/sys/kernel/hotplug``, which normally
+holds the pathname ``/sbin/hotplug``.  That parameter names a program
+which the kernel may invoke at various times.
+
+The /sbin/hotplug program can be invoked by any subsystem as part of its
+reaction to a configuration change, from a thread in that subsystem.
+Only one parameter is required: the name of a subsystem being notified of
+some kernel event.  That name is used as the first key for further event
+dispatch; any other argument and environment parameters are specified by
+the subsystem making that invocation.
+
+Hotplug software and other resources is available at:
+
+	http://linux-hotplug.sourceforge.net
+
+Mailing list information is also available at that site.
+
+
+USB Policy Agent
+================
+
+The USB subsystem currently invokes ``/sbin/hotplug`` when USB devices
+are added or removed from system.  The invocation is done by the kernel
+hub workqueue [hub_wq], or else as part of root hub initialization
+(done by init, modprobe, kapmd, etc).  Its single command line parameter
+is the string "usb", and it passes these environment variables:
+
+========== ============================================
+ACTION     ``add``, ``remove``
+PRODUCT    USB vendor, product, and version codes (hex)
+TYPE       device class codes (decimal)
+INTERFACE  interface 0 class codes (decimal)
+========== ============================================
+
+If "usbdevfs" is configured, DEVICE and DEVFS are also passed.  DEVICE is
+the pathname of the device, and is useful for devices with multiple and/or
+alternate interfaces that complicate driver selection.  By design, USB
+hotplugging is independent of ``usbdevfs``:  you can do most essential parts
+of USB device setup without using that filesystem, and without running a
+user mode daemon to detect changes in system configuration.
+
+Currently available policy agent implementations can load drivers for
+modules, and can invoke driver-specific setup scripts.  The newest ones
+leverage USB module-init-tools support.  Later agents might unload drivers.
+
+
+USB Modutils Support
+====================
+
+Current versions of module-init-tools will create a ``modules.usbmap`` file
+which contains the entries from each driver's ``MODULE_DEVICE_TABLE``.  Such
+files can be used by various user mode policy agents to make sure all the
+right driver modules get loaded, either at boot time or later.
+
+See ``linux/usb.h`` for full information about such table entries; or look
+at existing drivers.  Each table entry describes one or more criteria to
+be used when matching a driver to a device or class of devices.  The
+specific criteria are identified by bits set in "match_flags", paired
+with field values.  You can construct the criteria directly, or with
+macros such as these, and use driver_info to store more information::
+
+    USB_DEVICE (vendorId, productId)
+	... matching devices with specified vendor and product ids
+    USB_DEVICE_VER (vendorId, productId, lo, hi)
+	... like USB_DEVICE with lo <= productversion <= hi
+    USB_INTERFACE_INFO (class, subclass, protocol)
+	... matching specified interface class info
+    USB_DEVICE_INFO (class, subclass, protocol)
+	... matching specified device class info
+
+A short example, for a driver that supports several specific USB devices
+and their quirks, might have a MODULE_DEVICE_TABLE like this::
+
+    static const struct usb_device_id mydriver_id_table[] = {
+	{ USB_DEVICE (0x9999, 0xaaaa), driver_info: QUIRK_X },
+	{ USB_DEVICE (0xbbbb, 0x8888), driver_info: QUIRK_Y|QUIRK_Z },
+	...
+	{ } /* end with an all-zeroes entry */
+    };
+    MODULE_DEVICE_TABLE(usb, mydriver_id_table);
+
+Most USB device drivers should pass these tables to the USB subsystem as
+well as to the module management subsystem.  Not all, though: some driver
+frameworks connect using interfaces layered over USB, and so they won't
+need such a struct usb_driver.
+
+Drivers that connect directly to the USB subsystem should be declared
+something like this::
+
+    static struct usb_driver mydriver = {
+	.name		= "mydriver",
+	.id_table	= mydriver_id_table,
+	.probe		= my_probe,
+	.disconnect	= my_disconnect,
+
+	/*
+	if using the usb chardev framework:
+	    .minor		= MY_USB_MINOR_START,
+	    .fops		= my_file_ops,
+	if exposing any operations through usbdevfs:
+	    .ioctl		= my_ioctl,
+	*/
+    };
+
+When the USB subsystem knows about a driver's device ID table, it's used when
+choosing drivers to probe().  The thread doing new device processing checks
+drivers' device ID entries from the ``MODULE_DEVICE_TABLE`` against interface
+and device descriptors for the device.  It will only call ``probe()`` if there
+is a match, and the third argument to ``probe()`` will be the entry that
+matched.
+
+If you don't provide an ``id_table`` for your driver, then your driver may get
+probed for each new device; the third parameter to ``probe()`` will be
+``NULL``.