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, 109 insertions, 0 deletions

diff --git a/Documentation/userspace-api/netlink/c-code-gen.rst b/Documentation/userspace-api/netlink/c-code-gen.rst
new file mode 100644
index 000000000..46415e6d6
--- /dev/null
+++ b/Documentation/userspace-api/netlink/c-code-gen.rst
@@ -0,0 +1,109 @@
+.. SPDX-License-Identifier: BSD-3-Clause
+
+==============================
+Netlink spec C code generation
+==============================
+
+This document describes how Netlink specifications are used to render
+C code (uAPI, policies etc.). It also defines the additional properties
+allowed in older families by the ``genetlink-c`` protocol level,
+to control the naming.
+
+For brevity this document refers to ``name`` properties of various
+objects by the object type. For example ``$attr`` is the value
+of ``name`` in an attribute, and ``$family`` is the name of the
+family (the global ``name`` property).
+
+The upper case is used to denote literal values, e.g. ``$family-CMD``
+means the concatenation of ``$family``, a dash character, and the literal
+``CMD``.
+
+The names of ``#defines`` and enum values are always converted to upper case,
+and with dashes (``-``) replaced by underscores (``_``).
+
+If the constructed name is a C keyword, an extra underscore is
+appended (``do`` -> ``do_``).
+
+Globals
+=======
+
+``c-family-name`` controls the name of the ``#define`` for the family
+name, default is ``$family-FAMILY-NAME``.
+
+``c-version-name`` controls the name of the ``#define`` for the version
+of the family, default is ``$family-FAMILY-VERSION``.
+
+``max-by-define`` selects if max values for enums are defined as a
+``#define`` rather than inside the enum.
+
+Definitions
+===========
+
+Constants
+---------
+
+Every constant is rendered as a ``#define``.
+The name of the constant is ``$family-$constant`` and the value
+is rendered as a string or integer according to its type in the spec.
+
+Enums and flags
+---------------
+
+Enums are named ``$family-$enum``. The full name can be set directly
+or suppressed by specifying the ``enum-name`` property.
+Default entry name is ``$family-$enum-$entry``.
+If ``name-prefix`` is specified it replaces the ``$family-$enum``
+portion of the entry name.
+
+Boolean ``render-max`` controls creation of the max values
+(which are enabled by default for attribute enums). These max
+values are named ``__$pfx-MAX`` and ``$pfx-MAX``. The name
+of the first value can be overridden via ``enum-cnt-name`` property.
+
+Attributes
+==========
+
+Each attribute set (excluding fractional sets) is rendered as an enum.
+
+Attribute enums are traditionally unnamed in netlink headers.
+If naming is desired ``enum-name`` can be used to specify the name.
+
+The default attribute name prefix is ``$family-A`` if the name of the set
+is the same as the name of the family and ``$family-A-$set`` if the names
+differ. The prefix can be overridden by the ``name-prefix`` property of a set.
+The rest of the section will refer to the prefix as ``$pfx``.
+
+Attributes are named ``$pfx-$attribute``.
+
+Attribute enums end with two special values ``__$pfx-MAX`` and ``$pfx-MAX``
+which are used for sizing attribute tables.
+These two names can be specified directly with the ``attr-cnt-name``
+and ``attr-max-name`` properties respectively.
+
+If ``max-by-define`` is set to ``true`` at the global level ``attr-max-name``
+will be specified as a ``#define`` rather than an enum value.
+
+Operations
+==========
+
+Operations are named ``$family-CMD-$operation``.
+If ``name-prefix`` is specified it replaces the ``$family-CMD``
+portion of the name.
+
+Similarly to attribute enums operation enums end with special count and max
+attributes. For operations those attributes can be renamed with
+``cmd-cnt-name`` and ``cmd-max-name``. Max will be a define if ``max-by-define``
+is ``true``.
+
+Multicast groups
+================
+
+Each multicast group gets a define rendered into the kernel uAPI header.
+The name of the define is ``$family-MCGRP-$group``, and can be overwritten
+with the ``c-define-name`` property.
+
+Code generation
+===============
+
+uAPI header is assumed to come from ``<linux/$family.h>`` in the default header
+search path. It can be changed using the ``uapi-header`` global property.