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, 386 insertions, 0 deletions

diff --git a/Documentation/userspace-api/ntsync.rst b/Documentation/userspace-api/ntsync.rst
new file mode 100644
index 000000000..a778016fe
--- /dev/null
+++ b/Documentation/userspace-api/ntsync.rst
@@ -0,0 +1,386 @@
+===================================
+NT synchronization primitive driver
+===================================
+
+This page documents the user-space API for the ntsync driver.
+
+ntsync is a support driver for emulation of NT synchronization
+primitives by user-space NT emulators. It exists because implementation
+in user-space, using existing tools, cannot match Windows performance
+while offering accurate semantics. It is implemented entirely in
+software, and does not drive any hardware device.
+
+This interface is meant as a compatibility tool only, and should not
+be used for general synchronization. Instead use generic, versatile
+interfaces such as futex(2) and poll(2).
+
+Synchronization primitives
+==========================
+
+The ntsync driver exposes three types of synchronization primitives:
+semaphores, mutexes, and events.
+
+A semaphore holds a single volatile 32-bit counter, and a static 32-bit
+integer denoting the maximum value. It is considered signaled (that is,
+can be acquired without contention, or will wake up a waiting thread)
+when the counter is nonzero. The counter is decremented by one when a
+wait is satisfied. Both the initial and maximum count are established
+when the semaphore is created.
+
+A mutex holds a volatile 32-bit recursion count, and a volatile 32-bit
+identifier denoting its owner. A mutex is considered signaled when its
+owner is zero (indicating that it is not owned). The recursion count is
+incremented when a wait is satisfied, and ownership is set to the given
+identifier.
+
+A mutex also holds an internal flag denoting whether its previous owner
+has died; such a mutex is said to be abandoned. Owner death is not
+tracked automatically based on thread death, but rather must be
+communicated using ``NTSYNC_IOC_MUTEX_KILL``. An abandoned mutex is
+inherently considered unowned.
+
+Except for the "unowned" semantics of zero, the actual value of the
+owner identifier is not interpreted by the ntsync driver at all. The
+intended use is to store a thread identifier; however, the ntsync
+driver does not actually validate that a calling thread provides
+consistent or unique identifiers.
+
+An event is similar to a semaphore with a maximum count of one. It holds
+a volatile boolean state denoting whether it is signaled or not. There
+are two types of events, auto-reset and manual-reset. An auto-reset
+event is designaled when a wait is satisfied; a manual-reset event is
+not. The event type is specified when the event is created.
+
+Unless specified otherwise, all operations on an object are atomic and
+totally ordered with respect to other operations on the same object.
+
+Objects are represented by files. When all file descriptors to an
+object are closed, that object is deleted.
+
+Char device
+===========
+
+The ntsync driver creates a single char device /dev/ntsync. Each file
+description opened on the device represents a unique instance intended
+to back an individual NT virtual machine. Objects created by one ntsync
+instance may only be used with other objects created by the same
+instance.
+
+ioctl reference
+===============
+
+All operations on the device are done through ioctls. There are four
+structures used in ioctl calls::
+
+   struct ntsync_sem_args {
+   	__u32 count;
+   	__u32 max;
+   };
+
+   struct ntsync_mutex_args {
+   	__u32 owner;
+   	__u32 count;
+   };
+
+   struct ntsync_event_args {
+   	__u32 manual;
+   	__u32 signaled;
+   };
+
+   struct ntsync_wait_args {
+   	__u64 timeout;
+   	__u64 objs;
+   	__u32 count;
+   	__u32 index;
+   	__u32 flags;
+   	__u32 owner;
+   	__u32 alert;
+   	__u32 pad;
+   };
+
+Depending on the ioctl, members of the structure may be used as input,
+output, or not at all.
+
+The ioctls on the device file are as follows:
+
+.. c:macro:: NTSYNC_IOC_CREATE_SEM
+
+  Create a semaphore object. Takes a pointer to struct
+  :c:type:`ntsync_sem_args`, which is used as follows:
+
+  .. list-table::
+
+     * - ``count``
+       - Initial count of the semaphore.
+     * - ``max``
+       - Maximum count of the semaphore.
+
+  Fails with ``EINVAL`` if ``count`` is greater than ``max``.
+  On success, returns a file descriptor the created semaphore.
+
+.. c:macro:: NTSYNC_IOC_CREATE_MUTEX
+
+  Create a mutex object. Takes a pointer to struct
+  :c:type:`ntsync_mutex_args`, which is used as follows:
+
+  .. list-table::
+
+     * - ``count``
+       - Initial recursion count of the mutex.
+     * - ``owner``
+       - Initial owner of the mutex.
+
+  If ``owner`` is nonzero and ``count`` is zero, or if ``owner`` is
+  zero and ``count`` is nonzero, the function fails with ``EINVAL``.
+  On success, returns a file descriptor the created mutex.
+
+.. c:macro:: NTSYNC_IOC_CREATE_EVENT
+
+  Create an event object. Takes a pointer to struct
+  :c:type:`ntsync_event_args`, which is used as follows:
+
+  .. list-table::
+
+     * - ``signaled``
+       - If nonzero, the event is initially signaled, otherwise
+         nonsignaled.
+     * - ``manual``
+       - If nonzero, the event is a manual-reset event, otherwise
+         auto-reset.
+
+  On success, returns a file descriptor the created event.
+
+The ioctls on the individual objects are as follows:
+
+.. c:macro:: NTSYNC_IOC_SEM_RELEASE
+
+  Post to a semaphore object. Takes a pointer to a 32-bit integer,
+  which on input holds the count to be added to the semaphore, and on
+  output contains its previous count.
+
+  If adding to the semaphore's current count would raise the latter
+  past the semaphore's maximum count, the ioctl fails with
+  ``EOVERFLOW`` and the semaphore is not affected. If raising the
+  semaphore's count causes it to become signaled, eligible threads
+  waiting on this semaphore will be woken and the semaphore's count
+  decremented appropriately.
+
+.. c:macro:: NTSYNC_IOC_MUTEX_UNLOCK
+
+  Release a mutex object. Takes a pointer to struct
+  :c:type:`ntsync_mutex_args`, which is used as follows:
+
+  .. list-table::
+
+     * - ``owner``
+       - Specifies the owner trying to release this mutex.
+     * - ``count``
+       - On output, contains the previous recursion count.
+
+  If ``owner`` is zero, the ioctl fails with ``EINVAL``. If ``owner``
+  is not the current owner of the mutex, the ioctl fails with
+  ``EPERM``.
+
+  The mutex's count will be decremented by one. If decrementing the
+  mutex's count causes it to become zero, the mutex is marked as
+  unowned and signaled, and eligible threads waiting on it will be
+  woken as appropriate.
+
+.. c:macro:: NTSYNC_IOC_EVENT_SET
+
+  Signal an event object. Takes a pointer to a 32-bit integer, which on
+  output contains the previous state of the event.
+
+  Eligible threads will be woken, and auto-reset events will be
+  designaled appropriately.
+
+.. c:macro:: NTSYNC_IOC_EVENT_RESET
+
+  Designal an event object. Takes a pointer to a 32-bit integer, which
+  on output contains the previous state of the event.
+
+.. c:macro:: NTSYNC_IOC_EVENT_PULSE
+
+  Wake threads waiting on an event object while leaving it in an
+  unsignaled state. Takes a pointer to a 32-bit integer, which on
+  output contains the previous state of the event.
+
+  A pulse operation can be thought of as a set followed by a reset,
+  performed as a single atomic operation. If two threads are waiting on
+  an auto-reset event which is pulsed, only one will be woken. If two
+  threads are waiting a manual-reset event which is pulsed, both will
+  be woken. However, in both cases, the event will be unsignaled
+  afterwards, and a simultaneous read operation will always report the
+  event as unsignaled.
+
+.. c:macro:: NTSYNC_IOC_SEM_READ
+
+  Read the current state of a semaphore object. Takes a pointer to
+  struct :c:type:`ntsync_sem_args`, which is used as follows:
+
+  .. list-table::
+
+     * - ``count``
+       - On output, contains the current count of the semaphore.
+     * - ``max``
+       - On output, contains the maximum count of the semaphore.
+
+.. c:macro:: NTSYNC_IOC_MUTEX_READ
+
+  Read the current state of a mutex object. Takes a pointer to struct
+  :c:type:`ntsync_mutex_args`, which is used as follows:
+
+  .. list-table::
+
+     * - ``owner``
+       - On output, contains the current owner of the mutex, or zero
+         if the mutex is not currently owned.
+     * - ``count``
+       - On output, contains the current recursion count of the mutex.
+
+  If the mutex is marked as abandoned, the function fails with
+  ``EOWNERDEAD``. In this case, ``count`` and ``owner`` are set to
+  zero.
+
+.. c:macro:: NTSYNC_IOC_EVENT_READ
+
+  Read the current state of an event object. Takes a pointer to struct
+  :c:type:`ntsync_event_args`, which is used as follows:
+
+  .. list-table::
+
+     * - ``signaled``
+       - On output, contains the current state of the event.
+     * - ``manual``
+       - On output, contains 1 if the event is a manual-reset event,
+         and 0 otherwise.
+
+.. c:macro:: NTSYNC_IOC_MUTEX_KILL
+
+  Mark a mutex as unowned and abandoned if it is owned by the given
+  owner. Takes an input-only pointer to a 32-bit integer denoting the
+  owner. If the owner is zero, the ioctl fails with ``EINVAL``. If the
+  owner does not own the mutex, the function fails with ``EPERM``.
+
+  Eligible threads waiting on the mutex will be woken as appropriate
+  (and such waits will fail with ``EOWNERDEAD``, as described below).
+
+.. c:macro:: NTSYNC_IOC_WAIT_ANY
+
+  Poll on any of a list of objects, atomically acquiring at most one.
+  Takes a pointer to struct :c:type:`ntsync_wait_args`, which is
+  used as follows:
+
+  .. list-table::
+
+     * - ``timeout``
+       - Absolute timeout in nanoseconds. If ``NTSYNC_WAIT_REALTIME``
+         is set, the timeout is measured against the REALTIME clock;
+         otherwise it is measured against the MONOTONIC clock in the
+         caller's time namespace. If the timeout is equal to or earlier
+         than the current time, the function returns immediately
+         without sleeping. If ``timeout`` is U64_MAX, the function will
+         sleep until an object is signaled, and will not fail with
+         ``ETIMEDOUT``.
+     * - ``objs``
+       - Pointer to an array of ``count`` file descriptors
+         (specified as an integer so that the structure has the same
+         size regardless of architecture). If any object is
+         invalid, the function fails with ``EINVAL``.
+     * - ``count``
+       - Number of objects specified in the ``objs`` array.
+         If greater than ``NTSYNC_MAX_WAIT_COUNT``, the function fails
+         with ``EINVAL``.
+     * - ``owner``
+       - Mutex owner identifier. If any object in ``objs`` is a mutex,
+         the ioctl will attempt to acquire that mutex on behalf of
+         ``owner``. If ``owner`` is zero, the ioctl fails with
+         ``EINVAL``.
+     * - ``index``
+       - On success, contains the index (into ``objs``) of the object
+         which was signaled. If ``alert`` was signaled instead,
+         this contains ``count``.
+     * - ``alert``
+       - Optional event object file descriptor. If nonzero, this
+         specifies an "alert" event object which, if signaled, will
+         terminate the wait. If nonzero, the identifier must point to a
+         valid event.
+     * - ``flags``
+       - Zero or more flags. Currently the only flag is
+         ``NTSYNC_WAIT_REALTIME``, which causes the timeout to be
+         measured against the REALTIME clock instead of MONOTONIC.
+     * - ``pad``
+       - Unused, must be set to zero.
+
+  This function attempts to acquire one of the given objects. If unable
+  to do so, it sleeps until an object becomes signaled, subsequently
+  acquiring it, or the timeout expires. In the latter case the ioctl
+  fails with ``ETIMEDOUT``. The function only acquires one object, even
+  if multiple objects are signaled.
+
+  A semaphore is considered to be signaled if its count is nonzero, and
+  is acquired by decrementing its count by one. A mutex is considered
+  to be signaled if it is unowned or if its owner matches the ``owner``
+  argument, and is acquired by incrementing its recursion count by one
+  and setting its owner to the ``owner`` argument. An auto-reset event
+  is acquired by designaling it; a manual-reset event is not affected
+  by acquisition.
+
+  Acquisition is atomic and totally ordered with respect to other
+  operations on the same object. If two wait operations (with different
+  ``owner`` identifiers) are queued on the same mutex, only one is
+  signaled. If two wait operations are queued on the same semaphore,
+  and a value of one is posted to it, only one is signaled.
+
+  If an abandoned mutex is acquired, the ioctl fails with
+  ``EOWNERDEAD``. Although this is a failure return, the function may
+  otherwise be considered successful. The mutex is marked as owned by
+  the given owner (with a recursion count of 1) and as no longer
+  abandoned, and ``index`` is still set to the index of the mutex.
+
+  The ``alert`` argument is an "extra" event which can terminate the
+  wait, independently of all other objects.
+
+  It is valid to pass the same object more than once, including by
+  passing the same event in the ``objs`` array and in ``alert``. If a
+  wakeup occurs due to that object being signaled, ``index`` is set to
+  the lowest index corresponding to that object.
+
+  The function may fail with ``EINTR`` if a signal is received.
+
+.. c:macro:: NTSYNC_IOC_WAIT_ALL
+
+  Poll on a list of objects, atomically acquiring all of them. Takes a
+  pointer to struct :c:type:`ntsync_wait_args`, which is used
+  identically to ``NTSYNC_IOC_WAIT_ANY``, except that ``index`` is
+  always filled with zero on success if not woken via alert.
+
+  This function attempts to simultaneously acquire all of the given
+  objects. If unable to do so, it sleeps until all objects become
+  simultaneously signaled, subsequently acquiring them, or the timeout
+  expires. In the latter case the ioctl fails with ``ETIMEDOUT`` and no
+  objects are modified.
+
+  Objects may become signaled and subsequently designaled (through
+  acquisition by other threads) while this thread is sleeping. Only
+  once all objects are simultaneously signaled does the ioctl acquire
+  them and return. The entire acquisition is atomic and totally ordered
+  with respect to other operations on any of the given objects.
+
+  If an abandoned mutex is acquired, the ioctl fails with
+  ``EOWNERDEAD``. Similarly to ``NTSYNC_IOC_WAIT_ANY``, all objects are
+  nevertheless marked as acquired. Note that if multiple mutex objects
+  are specified, there is no way to know which were marked as
+  abandoned.
+
+  As with "any" waits, the ``alert`` argument is an "extra" event which
+  can terminate the wait. Critically, however, an "all" wait will
+  succeed if all members in ``objs`` are signaled, *or* if ``alert`` is
+  signaled. In the latter case ``index`` will be set to ``count``. As
+  with "any" waits, if both conditions are filled, the former takes
+  priority, and objects in ``objs`` will be acquired.
+
+  Unlike ``NTSYNC_IOC_WAIT_ANY``, it is not valid to pass the same
+  object more than once, nor is it valid to pass the same object in
+  ``objs`` and in ``alert``. If this is attempted, the function fails
+  with ``EINVAL``.