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, 196 insertions, 0 deletions

diff --git a/Documentation/dev-tools/kunit/architecture.rst b/Documentation/dev-tools/kunit/architecture.rst
new file mode 100644
index 000000000..f335f883f
--- /dev/null
+++ b/Documentation/dev-tools/kunit/architecture.rst
@@ -0,0 +1,196 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==================
+KUnit Architecture
+==================
+
+The KUnit architecture is divided into two parts:
+
+- `In-Kernel Testing Framework`_
+- `kunit_tool (Command-line Test Harness)`_
+
+In-Kernel Testing Framework
+===========================
+
+The kernel testing library supports KUnit tests written in C using
+KUnit. These KUnit tests are kernel code. KUnit performs the following
+tasks:
+
+- Organizes tests
+- Reports test results
+- Provides test utilities
+
+Test Cases
+----------
+
+The test case is the fundamental unit in KUnit. KUnit test cases are organised
+into suites. A KUnit test case is a function with type signature
+``void (*)(struct kunit *test)``. These test case functions are wrapped in a
+struct called struct kunit_case.
+
+.. note:
+	``generate_params`` is optional for non-parameterized tests.
+
+Each KUnit test case receives a ``struct kunit`` context object that tracks a
+running test. The KUnit assertion macros and other KUnit utilities use the
+``struct kunit`` context object. As an exception, there are two fields:
+
+- ``->priv``: The setup functions can use it to store arbitrary test
+  user data.
+
+- ``->param_value``: It contains the parameter value which can be
+  retrieved in the parameterized tests.
+
+Test Suites
+-----------
+
+A KUnit suite includes a collection of test cases. The KUnit suites
+are represented by the ``struct kunit_suite``. For example:
+
+.. code-block:: c
+
+	static struct kunit_case example_test_cases[] = {
+		KUNIT_CASE(example_test_foo),
+		KUNIT_CASE(example_test_bar),
+		KUNIT_CASE(example_test_baz),
+		{}
+	};
+
+	static struct kunit_suite example_test_suite = {
+		.name = "example",
+		.init = example_test_init,
+		.exit = example_test_exit,
+		.test_cases = example_test_cases,
+	};
+	kunit_test_suite(example_test_suite);
+
+In the above example, the test suite ``example_test_suite``, runs the
+test cases ``example_test_foo``, ``example_test_bar``, and
+``example_test_baz``. Before running the test, the ``example_test_init``
+is called and after running the test, ``example_test_exit`` is called.
+The ``kunit_test_suite(example_test_suite)`` registers the test suite
+with the KUnit test framework.
+
+Executor
+--------
+
+The KUnit executor can list and run built-in KUnit tests on boot.
+The Test suites are stored in a linker section
+called ``.kunit_test_suites``. For the code, see ``KUNIT_TABLE()`` macro
+definition in
+`include/asm-generic/vmlinux.lds.h <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/asm-generic/vmlinux.lds.h?h=v6.0#n950>`_.
+The linker section consists of an array of pointers to
+``struct kunit_suite``, and is populated by the ``kunit_test_suites()``
+macro. The KUnit executor iterates over the linker section array in order to
+run all the tests that are compiled into the kernel.
+
+.. kernel-figure:: kunit_suitememorydiagram.svg
+	:alt:	KUnit Suite Memory
+
+	KUnit Suite Memory Diagram
+
+On the kernel boot, the KUnit executor uses the start and end addresses
+of this section to iterate over and run all tests. For the implementation of the
+executor, see
+`lib/kunit/executor.c <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/lib/kunit/executor.c>`_.
+When built as a module, the ``kunit_test_suites()`` macro defines a
+``module_init()`` function, which runs all the tests in the compilation
+unit instead of utilizing the executor.
+
+In KUnit tests, some error classes do not affect other tests
+or parts of the kernel, each KUnit case executes in a separate thread
+context. See the ``kunit_try_catch_run()`` function in
+`lib/kunit/try-catch.c <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/lib/kunit/try-catch.c?h=v5.15#n58>`_.
+
+Assertion Macros
+----------------
+
+KUnit tests verify state using expectations/assertions.
+All expectations/assertions are formatted as:
+``KUNIT_{EXPECT|ASSERT}_<op>[_MSG](kunit, property[, message])``
+
+- ``{EXPECT|ASSERT}`` determines whether the check is an assertion or an
+  expectation.
+  In the event of a failure, the testing flow differs as follows:
+
+	- For expectations, the test is marked as failed and the failure is logged.
+
+	- Failing assertions, on the other hand, result in the test case being
+	  terminated immediately.
+
+		- Assertions call the function:
+		  ``void __noreturn __kunit_abort(struct kunit *)``.
+
+		- ``__kunit_abort`` calls the function:
+		  ``void __noreturn kunit_try_catch_throw(struct kunit_try_catch *try_catch)``.
+
+		- ``kunit_try_catch_throw`` calls the function:
+		  ``void kthread_complete_and_exit(struct completion *, long) __noreturn;``
+		  and terminates the special thread context.
+
+- ``<op>`` denotes a check with options: ``TRUE`` (supplied property
+  has the boolean value "true"), ``EQ`` (two supplied properties are
+  equal), ``NOT_ERR_OR_NULL`` (supplied pointer is not null and does not
+  contain an "err" value).
+
+- ``[_MSG]`` prints a custom message on failure.
+
+Test Result Reporting
+---------------------
+KUnit prints the test results in KTAP format. KTAP is based on TAP14, see
+Documentation/dev-tools/ktap.rst.
+KTAP works with KUnit and Kselftest. The KUnit executor prints KTAP results to
+dmesg, and debugfs (if configured).
+
+Parameterized Tests
+-------------------
+
+Each KUnit parameterized test is associated with a collection of
+parameters. The test is invoked multiple times, once for each parameter
+value and the parameter is stored in the ``param_value`` field.
+The test case includes a KUNIT_CASE_PARAM() macro that accepts a
+generator function. The generator function is passed the previous parameter
+and returns the next parameter. It also includes a macro for generating
+array-based common-case generators.
+
+kunit_tool (Command-line Test Harness)
+======================================
+
+``kunit_tool`` is a Python script, found in ``tools/testing/kunit/kunit.py``. It
+is used to configure, build, execute, parse test results and run all of the
+previous commands in correct order (i.e., configure, build, execute and parse).
+You have two options for running KUnit tests: either build the kernel with KUnit
+enabled and manually parse the results (see
+Documentation/dev-tools/kunit/run_manual.rst) or use ``kunit_tool``
+(see Documentation/dev-tools/kunit/run_wrapper.rst).
+
+- ``configure`` command generates the kernel ``.config`` from a
+  ``.kunitconfig`` file (and any architecture-specific options).
+  The Python scripts available in ``qemu_configs`` folder
+  (for example, ``tools/testing/kunit/qemu configs/powerpc.py``) contains
+  additional configuration options for specific architectures.
+  It parses both the existing ``.config`` and the ``.kunitconfig`` files
+  to ensure that ``.config`` is a superset of ``.kunitconfig``.
+  If not, it will combine the two and run ``make olddefconfig`` to regenerate
+  the ``.config`` file. It then checks to see if ``.config`` has become a superset.
+  This verifies that all the Kconfig dependencies are correctly specified in the
+  file ``.kunitconfig``. The ``kunit_config.py`` script contains the code for parsing
+  Kconfigs. The code which runs ``make olddefconfig`` is part of the
+  ``kunit_kernel.py`` script. You can invoke this command through:
+  ``./tools/testing/kunit/kunit.py config`` and
+  generate a ``.config`` file.
+- ``build`` runs ``make`` on the kernel tree with required options
+  (depends on the architecture and some options, for example: build_dir)
+  and reports any errors.
+  To build a KUnit kernel from the current ``.config``, you can use the
+  ``build`` argument: ``./tools/testing/kunit/kunit.py build``.
+- ``exec`` command executes kernel results either directly (using
+  User-mode Linux configuration), or through an emulator such
+  as QEMU. It reads results from the log using standard
+  output (stdout), and passes them to ``parse`` to be parsed.
+  If you already have built a kernel with built-in KUnit tests,
+  you can run the kernel and display the test results with the ``exec``
+  argument: ``./tools/testing/kunit/kunit.py exec``.
+- ``parse`` extracts the KTAP output from a kernel log, parses
+  the test results, and prints a summary. For failed tests, any
+  diagnostic output will be included.