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, 224 insertions, 0 deletions

diff --git a/Documentation/devicetree/of_unittest.rst b/Documentation/devicetree/of_unittest.rst
new file mode 100644
index 000000000..6ed6e3291
--- /dev/null
+++ b/Documentation/devicetree/of_unittest.rst
@@ -0,0 +1,224 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=================================
+Open Firmware Devicetree Unittest
+=================================
+
+Author: Gaurav Minocha <gaurav.minocha.os@gmail.com>
+
+1. Introduction
+===============
+
+This document explains how the test data required for executing OF unittest
+is attached to the live tree dynamically, independent of the machine's
+architecture.
+
+It is recommended to read the following documents before moving ahead.
+
+(1) Documentation/devicetree/usage-model.rst
+(2) http://www.devicetree.org/Device_Tree_Usage
+
+OF Selftest has been designed to test the interface (include/linux/of.h)
+provided to device driver developers to fetch the device information..etc.
+from the unflattened device tree data structure. This interface is used by
+most of the device drivers in various use cases.
+
+
+2. Verbose Output (EXPECT)
+==========================
+
+If unittest detects a problem it will print a warning or error message to
+the console.  Unittest also triggers warning and error messages from other
+kernel code as a result of intentionally bad unittest data.  This has led
+to confusion as to whether the triggered messages are an expected result
+of a test or whether there is a real problem that is independent of unittest.
+
+'EXPECT \ : text' (begin) and 'EXPECT / : text' (end) messages have been
+added to unittest to report that a warning or error is expected.  The
+begin is printed before triggering the warning or error, and the end is
+printed after triggering the warning or error.
+
+The EXPECT messages result in very noisy console messages that are difficult
+to read.  The script scripts/dtc/of_unittest_expect was created to filter
+this verbosity and highlight mismatches between triggered warnings and
+errors vs expected warnings and errors.  More information is available
+from 'scripts/dtc/of_unittest_expect --help'.
+
+
+3. Test-data
+============
+
+The Device Tree Source file (drivers/of/unittest-data/testcases.dtso) contains
+the test data required for executing the unit tests automated in
+drivers/of/unittest.c. See the content of the folder::
+
+    drivers/of/unittest-data/tests-*.dtsi
+
+for the Device Tree Source Include files (.dtsi) included in testcases.dtso.
+
+When the kernel is built with CONFIG_OF_UNITTEST enabled, then the following make
+rule::
+
+    $(obj)/%.dtbo: $(src)/%.dtso $(DTC) FORCE
+	    $(call if_changed_dep,dtc)
+
+is used to compile the DT source file (testcases.dtso) into a binary blob
+(testcases.dtbo), also referred as flattened DT.
+
+After that, using the following rule the binary blob above is wrapped as an
+assembly file (testcases.dtbo.S)::
+
+    $(obj)/%.dtbo.S: $(obj)/%.dtbo FORCE
+	    $(call if_changed,wrap_S_dtb)
+
+The assembly file is compiled into an object file (testcases.dtbo.o), and is
+linked into the kernel image.
+
+
+3.1. Adding the test data
+-------------------------
+
+Un-flattened device tree structure:
+
+Un-flattened device tree consists of connected device_node(s) in form of a tree
+structure described below::
+
+    // following struct members are used to construct the tree
+    struct device_node {
+	...
+	struct  device_node *parent;
+	struct  device_node *child;
+	struct  device_node *sibling;
+	...
+    };
+
+Figure 1, describes a generic structure of machine's un-flattened device tree
+considering only child and sibling pointers. There exists another pointer,
+``*parent``, that is used to traverse the tree in the reverse direction. So, at
+a particular level the child node and all the sibling nodes will have a parent
+pointer pointing to a common node (e.g. child1, sibling2, sibling3, sibling4's
+parent points to root node)::
+
+    root ('/')
+    |
+    child1 -> sibling2 -> sibling3 -> sibling4 -> null
+    |         |           |           |
+    |         |           |          null
+    |         |           |
+    |         |        child31 -> sibling32 -> null
+    |         |           |          |
+    |         |          null       null
+    |         |
+    |      child21 -> sibling22 -> sibling23 -> null
+    |         |          |            |
+    |        null       null         null
+    |
+    child11 -> sibling12 -> sibling13 -> sibling14 -> null
+    |           |           |            |
+    |           |           |           null
+    |           |           |
+    null        null       child131 -> null
+			    |
+			    null
+
+Figure 1: Generic structure of un-flattened device tree
+
+
+Before executing OF unittest, it is required to attach the test data to
+machine's device tree (if present). So, when selftest_data_add() is called,
+at first it reads the flattened device tree data linked into the kernel image
+via the following kernel symbols::
+
+    __dtb_testcases_begin - address marking the start of test data blob
+    __dtb_testcases_end   - address marking the end of test data blob
+
+Secondly, it calls of_fdt_unflatten_tree() to unflatten the flattened
+blob. And finally, if the machine's device tree (i.e. live tree) is present,
+then it attaches the unflattened test data tree to the live tree, else it
+attaches itself as a live device tree.
+
+attach_node_and_children() uses of_attach_node() to attach the nodes into the
+live tree as explained below. To explain the same, the test data tree described
+in Figure 2 is attached to the live tree described in Figure 1::
+
+    root ('/')
+	|
+    testcase-data
+	|
+    test-child0 -> test-sibling1 -> test-sibling2 -> test-sibling3 -> null
+	|               |                |                |
+    test-child01      null             null             null
+
+
+Figure 2: Example test data tree to be attached to live tree.
+
+According to the scenario above, the live tree is already present so it isn't
+required to attach the root('/') node. All other nodes are attached by calling
+of_attach_node() on each node.
+
+In the function of_attach_node(), the new node is attached as the child of the
+given parent in live tree. But, if parent already has a child then the new node
+replaces the current child and turns it into its sibling. So, when the testcase
+data node is attached to the live tree above (Figure 1), the final structure is
+as shown in Figure 3::
+
+    root ('/')
+    |
+    testcase-data -> child1 -> sibling2 -> sibling3 -> sibling4 -> null
+    |               |          |           |           |
+    (...)             |          |           |          null
+		    |          |         child31 -> sibling32 -> null
+		    |          |           |           |
+		    |          |          null        null
+		    |          |
+		    |        child21 -> sibling22 -> sibling23 -> null
+		    |          |           |            |
+		    |         null        null         null
+		    |
+		    child11 -> sibling12 -> sibling13 -> sibling14 -> null
+		    |          |            |            |
+		    null       null          |           null
+					    |
+					    child131 -> null
+					    |
+					    null
+    -----------------------------------------------------------------------
+
+    root ('/')
+    |
+    testcase-data -> child1 -> sibling2 -> sibling3 -> sibling4 -> null
+    |               |          |           |           |
+    |             (...)      (...)       (...)        null
+    |
+    test-sibling3 -> test-sibling2 -> test-sibling1 -> test-child0 -> null
+    |                |                   |                |
+    null             null                null         test-child01
+
+
+Figure 3: Live device tree structure after attaching the testcase-data.
+
+
+Astute readers would have noticed that test-child0 node becomes the last
+sibling compared to the earlier structure (Figure 2). After attaching first
+test-child0 the test-sibling1 is attached that pushes the child node
+(i.e. test-child0) to become a sibling and makes itself a child node,
+as mentioned above.
+
+If a duplicate node is found (i.e. if a node with same full_name property is
+already present in the live tree), then the node isn't attached rather its
+properties are updated to the live tree's node by calling the function
+update_node_properties().
+
+
+3.2. Removing the test data
+---------------------------
+
+Once the test case execution is complete, selftest_data_remove is called in
+order to remove the device nodes attached initially (first the leaf nodes are
+detached and then moving up the parent nodes are removed, and eventually the
+whole tree). selftest_data_remove() calls detach_node_and_children() that uses
+of_detach_node() to detach the nodes from the live device tree.
+
+To detach a node, of_detach_node() either updates the child pointer of given
+node's parent to its sibling or attaches the previous sibling to the given
+node's sibling, as appropriate. That is it :)