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

3 files changed, 148 insertions, 0 deletions

diff --git a/Documentation/driver-api/hte/hte.rst b/Documentation/driver-api/hte/hte.rst
new file mode 100644
index 000000000..153f3233c
--- /dev/null
+++ b/Documentation/driver-api/hte/hte.rst
@@ -0,0 +1,79 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+============================================
+The Linux Hardware Timestamping Engine (HTE)
+============================================
+
+:Author: Dipen Patel
+
+Introduction
+------------
+
+Certain devices have built in hardware timestamping engines which can
+monitor sets of system signals, lines, buses etc... in realtime for state
+change; upon detecting the change they can automatically store the timestamp at
+the moment of occurrence. Such functionality may help achieve better accuracy
+in obtaining timestamps than using software counterparts i.e. ktime and
+friends.
+
+This document describes the API that can be used by hardware timestamping
+engine provider and consumer drivers that want to use the hardware timestamping
+engine (HTE) framework. Both consumers and providers must include
+``#include <linux/hte.h>``.
+
+The HTE framework APIs for the providers
+----------------------------------------
+
+.. kernel-doc:: drivers/hte/hte.c
+   :functions: devm_hte_register_chip hte_push_ts_ns
+
+The HTE framework APIs for the consumers
+----------------------------------------
+
+.. kernel-doc:: drivers/hte/hte.c
+   :functions: hte_init_line_attr hte_ts_get hte_ts_put devm_hte_request_ts_ns hte_request_ts_ns hte_enable_ts hte_disable_ts of_hte_req_count hte_get_clk_src_info
+
+The HTE framework public structures
+-----------------------------------
+.. kernel-doc:: include/linux/hte.h
+
+More on the HTE timestamp data
+------------------------------
+The ``struct hte_ts_data`` is used to pass timestamp details between the
+consumers and the providers. It expresses timestamp data in nanoseconds in
+u64. An example of the typical timestamp data life cycle, for the GPIO line is
+as follows::
+
+ - Monitors GPIO line change.
+ - Detects the state change on GPIO line.
+ - Converts timestamps in nanoseconds.
+ - Stores GPIO raw level in raw_level variable if the provider has that
+ hardware capability.
+ - Pushes this hte_ts_data object to HTE subsystem.
+ - HTE subsystem increments seq counter and invokes consumer provided callback.
+ Based on callback return value, the HTE core invokes secondary callback in
+ the thread context.
+
+HTE subsystem debugfs attributes
+--------------------------------
+HTE subsystem creates debugfs attributes at ``/sys/kernel/debug/hte/``.
+It also creates line/signal-related debugfs attributes at
+``/sys/kernel/debug/hte/<provider>/<label or line id>/``. Note that these
+attributes are read-only.
+
+`ts_requested`
+		The total number of entities requested from the given provider,
+		where entity is specified by the provider and could represent
+		lines, GPIO, chip signals, buses etc...
+                The attribute will be available at
+		``/sys/kernel/debug/hte/<provider>/``.
+
+`total_ts`
+		The total number of entities supported by the provider.
+                The attribute will be available at
+		``/sys/kernel/debug/hte/<provider>/``.
+
+`dropped_timestamps`
+		The dropped timestamps for a given line.
+                The attribute will be available at
+		``/sys/kernel/debug/hte/<provider>/<label or line id>/``.
diff --git a/Documentation/driver-api/hte/index.rst b/Documentation/driver-api/hte/index.rst
new file mode 100644
index 000000000..29011de9a
--- /dev/null
+++ b/Documentation/driver-api/hte/index.rst
@@ -0,0 +1,22 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+============================================
+The Linux Hardware Timestamping Engine (HTE)
+============================================
+
+The HTE Subsystem
+=================
+
+.. toctree::
+   :maxdepth: 1
+
+   hte
+
+HTE Tegra Provider
+==================
+
+.. toctree::
+   :maxdepth: 1
+
+   tegra-hte
+
diff --git a/Documentation/driver-api/hte/tegra-hte.rst b/Documentation/driver-api/hte/tegra-hte.rst
new file mode 100644
index 000000000..85e654772
--- /dev/null
+++ b/Documentation/driver-api/hte/tegra-hte.rst
@@ -0,0 +1,47 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+HTE Kernel provider driver
+==========================
+
+Description
+-----------
+The Nvidia tegra HTE provider also known as GTE (Generic Timestamping Engine)
+driver implements two GTE instances: 1) GPIO GTE and 2) LIC
+(Legacy Interrupt Controller) IRQ GTE. Both GTE instances get the timestamp
+from the system counter TSC which has 31.25MHz clock rate, and the driver
+converts clock tick rate to nanoseconds before storing it as timestamp value.
+
+GPIO GTE
+--------
+
+This GTE instance timestamps GPIO in real time. For that to happen GPIO
+needs to be configured as input. Only the always on (AON) GPIO controller
+instance supports timestamping GPIOs in real time as it is tightly coupled with
+the GPIO GTE. To support this, GPIOLIB adds two optional APIs as mentioned
+below. The GPIO GTE code supports both kernel and userspace consumers. The
+kernel space consumers can directly talk to HTE subsystem while userspace
+consumers timestamp requests go through GPIOLIB CDEV framework to HTE
+subsystem. The hte devicetree binding described at
+``Documentation/devicetree/bindings/timestamp`` provides an example of how a
+consumer can request an GPIO line.
+
+See gpiod_enable_hw_timestamp_ns() and gpiod_disable_hw_timestamp_ns().
+
+For userspace consumers, GPIO_V2_LINE_FLAG_EVENT_CLOCK_HTE flag must be
+specified during IOCTL calls. Refer to ``tools/gpio/gpio-event-mon.c``, which
+returns the timestamp in nanoseconds.
+
+LIC (Legacy Interrupt Controller) IRQ GTE
+-----------------------------------------
+
+This GTE instance timestamps LIC IRQ lines in real time. The hte devicetree
+binding described at ``Documentation/devicetree/bindings/timestamp``
+provides an example of how a consumer can request an IRQ line. Since it is a
+one-to-one mapping with IRQ GTE provider, consumers can simply specify the IRQ
+number that they are interested in. There is no userspace consumer support for
+this GTE instance in the HTE framework.
+
+The provider source code of both IRQ and GPIO GTE instances is located at
+``drivers/hte/hte-tegra194.c``. The test driver
+``drivers/hte/hte-tegra194-test.c`` demonstrates HTE API usage for both IRQ
+and GPIO GTE.