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
  ...

3 files changed, 356 insertions, 0 deletions

diff --git a/Documentation/driver-api/nfc/index.rst b/Documentation/driver-api/nfc/index.rst
new file mode 100644
index 000000000..b6e9eedbf
--- /dev/null
+++ b/Documentation/driver-api/nfc/index.rst
@@ -0,0 +1,11 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+========================
+Near Field Communication
+========================
+
+.. toctree::
+   :maxdepth: 1
+
+   nfc-hci
+   nfc-pn544
diff --git a/Documentation/driver-api/nfc/nfc-hci.rst b/Documentation/driver-api/nfc/nfc-hci.rst
new file mode 100644
index 000000000..486aa647c
--- /dev/null
+++ b/Documentation/driver-api/nfc/nfc-hci.rst
@@ -0,0 +1,311 @@
+========================
+HCI backend for NFC Core
+========================
+
+- Author: Eric Lapuyade, Samuel Ortiz
+- Contact: eric.lapuyade@intel.com, samuel.ortiz@intel.com
+
+General
+-------
+
+The HCI layer implements much of the ETSI TS 102 622 V10.2.0 specification. It
+enables easy writing of HCI-based NFC drivers. The HCI layer runs as an NFC Core
+backend, implementing an abstract nfc device and translating NFC Core API
+to HCI commands and events.
+
+HCI
+---
+
+HCI registers as an nfc device with NFC Core. Requests coming from userspace are
+routed through netlink sockets to NFC Core and then to HCI. From this point,
+they are translated in a sequence of HCI commands sent to the HCI layer in the
+host controller (the chip). Commands can be executed synchronously (the sending
+context blocks waiting for response) or asynchronously (the response is returned
+from HCI Rx context).
+HCI events can also be received from the host controller. They will be handled
+and a translation will be forwarded to NFC Core as needed. There are hooks to
+let the HCI driver handle proprietary events or override standard behavior.
+HCI uses 2 execution contexts:
+
+- one for executing commands : nfc_hci_msg_tx_work(). Only one command
+  can be executing at any given moment.
+- one for dispatching received events and commands : nfc_hci_msg_rx_work().
+
+HCI Session initialization
+--------------------------
+
+The Session initialization is an HCI standard which must unfortunately
+support proprietary gates. This is the reason why the driver will pass a list
+of proprietary gates that must be part of the session. HCI will ensure all
+those gates have pipes connected when the hci device is set up.
+In case the chip supports pre-opened gates and pseudo-static pipes, the driver
+can pass that information to HCI core.
+
+HCI Gates and Pipes
+-------------------
+
+A gate defines the 'port' where some service can be found. In order to access
+a service, one must create a pipe to that gate and open it. In this
+implementation, pipes are totally hidden. The public API only knows gates.
+This is consistent with the driver need to send commands to proprietary gates
+without knowing the pipe connected to it.
+
+Driver interface
+----------------
+
+A driver is generally written in two parts : the physical link management and
+the HCI management. This makes it easier to maintain a driver for a chip that
+can be connected using various phy (i2c, spi, ...)
+
+HCI Management
+--------------
+
+A driver would normally register itself with HCI and provide the following
+entry points::
+
+  struct nfc_hci_ops {
+	int (*open)(struct nfc_hci_dev *hdev);
+	void (*close)(struct nfc_hci_dev *hdev);
+	int (*hci_ready) (struct nfc_hci_dev *hdev);
+	int (*xmit) (struct nfc_hci_dev *hdev, struct sk_buff *skb);
+	int (*start_poll) (struct nfc_hci_dev *hdev,
+			   u32 im_protocols, u32 tm_protocols);
+	int (*dep_link_up)(struct nfc_hci_dev *hdev, struct nfc_target *target,
+			   u8 comm_mode, u8 *gb, size_t gb_len);
+	int (*dep_link_down)(struct nfc_hci_dev *hdev);
+	int (*target_from_gate) (struct nfc_hci_dev *hdev, u8 gate,
+				 struct nfc_target *target);
+	int (*complete_target_discovered) (struct nfc_hci_dev *hdev, u8 gate,
+					   struct nfc_target *target);
+	int (*im_transceive) (struct nfc_hci_dev *hdev,
+			      struct nfc_target *target, struct sk_buff *skb,
+			      data_exchange_cb_t cb, void *cb_context);
+	int (*tm_send)(struct nfc_hci_dev *hdev, struct sk_buff *skb);
+	int (*check_presence)(struct nfc_hci_dev *hdev,
+			      struct nfc_target *target);
+	int (*event_received)(struct nfc_hci_dev *hdev, u8 gate, u8 event,
+			      struct sk_buff *skb);
+  };
+
+- open() and close() shall turn the hardware on and off.
+- hci_ready() is an optional entry point that is called right after the hci
+  session has been set up. The driver can use it to do additional initialization
+  that must be performed using HCI commands.
+- xmit() shall simply write a frame to the physical link.
+- start_poll() is an optional entrypoint that shall set the hardware in polling
+  mode. This must be implemented only if the hardware uses proprietary gates or a
+  mechanism slightly different from the HCI standard.
+- dep_link_up() is called after a p2p target has been detected, to finish
+  the p2p connection setup with hardware parameters that need to be passed back
+  to nfc core.
+- dep_link_down() is called to bring the p2p link down.
+- target_from_gate() is an optional entrypoint to return the nfc protocols
+  corresponding to a proprietary gate.
+- complete_target_discovered() is an optional entry point to let the driver
+  perform additional proprietary processing necessary to auto activate the
+  discovered target.
+- im_transceive() must be implemented by the driver if proprietary HCI commands
+  are required to send data to the tag. Some tag types will require custom
+  commands, others can be written to using the standard HCI commands. The driver
+  can check the tag type and either do proprietary processing, or return 1 to ask
+  for standard processing. The data exchange command itself must be sent
+  asynchronously.
+- tm_send() is called to send data in the case of a p2p connection
+- check_presence() is an optional entry point that will be called regularly
+  by the core to check that an activated tag is still in the field. If this is
+  not implemented, the core will not be able to push tag_lost events to the user
+  space
+- event_received() is called to handle an event coming from the chip. Driver
+  can handle the event or return 1 to let HCI attempt standard processing.
+
+On the rx path, the driver is responsible to push incoming HCP frames to HCI
+using nfc_hci_recv_frame(). HCI will take care of re-aggregation and handling
+This must be done from a context that can sleep.
+
+PHY Management
+--------------
+
+The physical link (i2c, ...) management is defined by the following structure::
+
+  struct nfc_phy_ops {
+	int (*write)(void *dev_id, struct sk_buff *skb);
+	int (*enable)(void *dev_id);
+	void (*disable)(void *dev_id);
+  };
+
+enable():
+	turn the phy on (power on), make it ready to transfer data
+disable():
+	turn the phy off
+write():
+	Send a data frame to the chip. Note that to enable higher
+	layers such as an llc to store the frame for re-emission, this
+	function must not alter the skb. It must also not return a positive
+	result (return 0 for success, negative for failure).
+
+Data coming from the chip shall be sent directly to nfc_hci_recv_frame().
+
+LLC
+---
+
+Communication between the CPU and the chip often requires some link layer
+protocol. Those are isolated as modules managed by the HCI layer. There are
+currently two modules : nop (raw transfer) and shdlc.
+A new llc must implement the following functions::
+
+  struct nfc_llc_ops {
+	void *(*init) (struct nfc_hci_dev *hdev, xmit_to_drv_t xmit_to_drv,
+		       rcv_to_hci_t rcv_to_hci, int tx_headroom,
+		       int tx_tailroom, int *rx_headroom, int *rx_tailroom,
+		       llc_failure_t llc_failure);
+	void (*deinit) (struct nfc_llc *llc);
+	int (*start) (struct nfc_llc *llc);
+	int (*stop) (struct nfc_llc *llc);
+	void (*rcv_from_drv) (struct nfc_llc *llc, struct sk_buff *skb);
+	int (*xmit_from_hci) (struct nfc_llc *llc, struct sk_buff *skb);
+  };
+
+init():
+	allocate and init your private storage
+deinit():
+	cleanup
+start():
+	establish the logical connection
+stop ():
+	terminate the logical connection
+rcv_from_drv():
+	handle data coming from the chip, going to HCI
+xmit_from_hci():
+	handle data sent by HCI, going to the chip
+
+The llc must be registered with nfc before it can be used. Do that by
+calling::
+
+	nfc_llc_register(const char *name, const struct nfc_llc_ops *ops);
+
+Again, note that the llc does not handle the physical link. It is thus very
+easy to mix any physical link with any llc for a given chip driver.
+
+Included Drivers
+----------------
+
+An HCI based driver for an NXP PN544, connected through I2C bus, and using
+shdlc is included.
+
+Execution Contexts
+------------------
+
+The execution contexts are the following:
+- IRQ handler (IRQH):
+fast, cannot sleep. sends incoming frames to HCI where they are passed to
+the current llc. In case of shdlc, the frame is queued in shdlc rx queue.
+
+- SHDLC State Machine worker (SMW)
+
+  Only when llc_shdlc is used: handles shdlc rx & tx queues.
+
+  Dispatches HCI cmd responses.
+
+- HCI Tx Cmd worker (MSGTXWQ)
+
+  Serializes execution of HCI commands.
+
+  Completes execution in case of response timeout.
+
+- HCI Rx worker (MSGRXWQ)
+
+  Dispatches incoming HCI commands or events.
+
+- Syscall context from a userspace call (SYSCALL)
+
+  Any entrypoint in HCI called from NFC Core
+
+Workflow executing an HCI command (using shdlc)
+-----------------------------------------------
+
+Executing an HCI command can easily be performed synchronously using the
+following API::
+
+  int nfc_hci_send_cmd (struct nfc_hci_dev *hdev, u8 gate, u8 cmd,
+			const u8 *param, size_t param_len, struct sk_buff **skb)
+
+The API must be invoked from a context that can sleep. Most of the time, this
+will be the syscall context. skb will return the result that was received in
+the response.
+
+Internally, execution is asynchronous. So all this API does is to enqueue the
+HCI command, setup a local wait queue on stack, and wait_event() for completion.
+The wait is not interruptible because it is guaranteed that the command will
+complete after some short timeout anyway.
+
+MSGTXWQ context will then be scheduled and invoke nfc_hci_msg_tx_work().
+This function will dequeue the next pending command and send its HCP fragments
+to the lower layer which happens to be shdlc. It will then start a timer to be
+able to complete the command with a timeout error if no response arrive.
+
+SMW context gets scheduled and invokes nfc_shdlc_sm_work(). This function
+handles shdlc framing in and out. It uses the driver xmit to send frames and
+receives incoming frames in an skb queue filled from the driver IRQ handler.
+SHDLC I(nformation) frames payload are HCP fragments. They are aggregated to
+form complete HCI frames, which can be a response, command, or event.
+
+HCI Responses are dispatched immediately from this context to unblock
+waiting command execution. Response processing involves invoking the completion
+callback that was provided by nfc_hci_msg_tx_work() when it sent the command.
+The completion callback will then wake the syscall context.
+
+It is also possible to execute the command asynchronously using this API::
+
+  static int nfc_hci_execute_cmd_async(struct nfc_hci_dev *hdev, u8 pipe, u8 cmd,
+				       const u8 *param, size_t param_len,
+				       data_exchange_cb_t cb, void *cb_context)
+
+The workflow is the same, except that the API call returns immediately, and
+the callback will be called with the result from the SMW context.
+
+Workflow receiving an HCI event or command
+------------------------------------------
+
+HCI commands or events are not dispatched from SMW context. Instead, they are
+queued to HCI rx_queue and will be dispatched from HCI rx worker
+context (MSGRXWQ). This is done this way to allow a cmd or event handler
+to also execute other commands (for example, handling the
+NFC_HCI_EVT_TARGET_DISCOVERED event from PN544 requires to issue an
+ANY_GET_PARAMETER to the reader A gate to get information on the target
+that was discovered).
+
+Typically, such an event will be propagated to NFC Core from MSGRXWQ context.
+
+Error management
+----------------
+
+Errors that occur synchronously with the execution of an NFC Core request are
+simply returned as the execution result of the request. These are easy.
+
+Errors that occur asynchronously (e.g. in a background protocol handling thread)
+must be reported such that upper layers don't stay ignorant that something
+went wrong below and know that expected events will probably never happen.
+Handling of these errors is done as follows:
+
+- driver (pn544) fails to deliver an incoming frame: it stores the error such
+  that any subsequent call to the driver will result in this error. Then it
+  calls the standard nfc_shdlc_recv_frame() with a NULL argument to report the
+  problem above. shdlc stores a EREMOTEIO sticky status, which will trigger
+  SMW to report above in turn.
+
+- SMW is basically a background thread to handle incoming and outgoing shdlc
+  frames. This thread will also check the shdlc sticky status and report to HCI
+  when it discovers it is not able to run anymore because of an unrecoverable
+  error that happened within shdlc or below. If the problem occurs during shdlc
+  connection, the error is reported through the connect completion.
+
+- HCI: if an internal HCI error happens (frame is lost), or HCI is reported an
+  error from a lower layer, HCI will either complete the currently executing
+  command with that error, or notify NFC Core directly if no command is
+  executing.
+
+- NFC Core: when NFC Core is notified of an error from below and polling is
+  active, it will send a tag discovered event with an empty tag list to the user
+  space to let it know that the poll operation will never be able to detect a
+  tag. If polling is not active and the error was sticky, lower levels will
+  return it at next invocation.
diff --git a/Documentation/driver-api/nfc/nfc-pn544.rst b/Documentation/driver-api/nfc/nfc-pn544.rst
new file mode 100644
index 000000000..6b2d8aae0
--- /dev/null
+++ b/Documentation/driver-api/nfc/nfc-pn544.rst
@@ -0,0 +1,34 @@
+============================================================================
+Kernel driver for the NXP Semiconductors PN544 Near Field Communication chip
+============================================================================
+
+
+General
+-------
+
+The PN544 is an integrated transmission module for contactless
+communication. The driver goes under drives/nfc/ and is compiled as a
+module named "pn544".
+
+Host Interfaces: I2C, SPI and HSU, this driver supports currently only I2C.
+
+Protocols
+---------
+
+In the normal (HCI) mode and in the firmware update mode read and
+write functions behave a bit differently because the message formats
+or the protocols are different.
+
+In the normal (HCI) mode the protocol used is derived from the ETSI
+HCI specification. The firmware is updated using a specific protocol,
+which is different from HCI.
+
+HCI messages consist of an eight bit header and the message body. The
+header contains the message length. Maximum size for an HCI message is
+33. In HCI mode sent messages are tested for a correct
+checksum. Firmware update messages have the length in the second (MSB)
+and third (LSB) bytes of the message. The maximum FW message length is
+1024 bytes.
+
+For the ETSI HCI specification see
+http://www.etsi.org/WebSite/Technologies/ProtocolSpecification.aspx