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, 115 insertions, 0 deletions

diff --git a/tools/testing/memblock/README b/tools/testing/memblock/README
new file mode 100644
index 000000000..b435f48d8
--- /dev/null
+++ b/tools/testing/memblock/README
@@ -0,0 +1,115 @@
+==================
+Memblock simulator
+==================
+
+Introduction
+============
+
+Memblock is a boot time memory allocator[1] that manages memory regions before
+the actual memory management is initialized. Its APIs allow to register physical
+memory regions, mark them as available or reserved, allocate a block of memory
+within the requested range and/or in specific NUMA node, and many more.
+
+Because it is used so early in the booting process, testing and debugging it is
+difficult. This test suite, usually referred as memblock simulator, is
+an attempt at testing the memblock mechanism. It runs one monolithic test that
+consist of a series of checks that exercise both the basic operations and
+allocation functionalities of memblock. The main data structure of the boot time
+memory allocator is initialized at the build time, so the checks here reuse its
+instance throughout the duration of the test. To ensure that tests don't affect
+each other, region arrays are reset in between.
+
+As this project uses the actual memblock code and has to run in user space,
+some of the kernel definitions were stubbed by the initial commit that
+introduced memblock simulator (commit 16802e55dea9 ("memblock tests: Add
+skeleton of the memblock simulator")) and a few preparation commits just
+before it. Most of them don't match the kernel implementation, so one should
+consult them first before making any significant changes to the project.
+
+Usage
+=====
+
+To run the tests, build the main target and run it:
+
+$ make && ./main
+
+A successful run produces no output. It is possible to control the behavior
+by passing options from command line. For example, to include verbose output,
+append the `-v` options when you run the tests:
+
+$ ./main -v
+
+This will print information about which functions are being tested and the
+number of test cases that passed.
+
+For the full list of options from command line, see `./main --help`.
+
+It is also possible to override different configuration parameters to change
+the test functions. For example, to simulate enabled NUMA, use:
+
+$ make NUMA=1
+
+For the full list of build options, see `make help`.
+
+Project structure
+=================
+
+The project has one target, main, which calls a group of checks for basic and
+allocation functions. Tests for each group are defined in dedicated files, as it
+can be seen here:
+
+memblock
+|-- asm       ------------------,
+|-- lib                         |-- implement function and struct stubs
+|-- linux     ------------------'
+|-- scripts
+|    |-- Makefile.include        -- handles `make` parameters
+|-- tests
+|    |-- alloc_api.(c|h)         -- memblock_alloc tests
+|    |-- alloc_helpers_api.(c|h) -- memblock_alloc_from tests
+|    |-- alloc_nid_api.(c|h)     -- memblock_alloc_try_nid tests
+|    |-- basic_api.(c|h)         -- memblock_add/memblock_reserve/... tests
+|    |-- common.(c|h)            -- helper functions for resetting memblock;
+|-- main.c        --------------.   dummy physical memory definition
+|-- Makefile                     `- test runner
+|-- README
+|-- TODO
+|-- .gitignore
+
+Simulating physical memory
+==========================
+
+Some allocation functions clear the memory in the process, so it is required for
+memblock to track valid memory ranges. To achieve this, the test suite registers
+with memblock memory stored by test_memory struct. It is a small wrapper that
+points to a block of memory allocated via malloc. For each group of allocation
+tests, dummy physical memory is allocated, added to memblock, and then released
+at the end of the test run. The structure of a test runner checking allocation
+functions is as follows:
+
+int memblock_alloc_foo_checks(void)
+{
+	reset_memblock_attributes();     /* data structure reset */
+	dummy_physical_memory_init();    /* allocate and register memory */
+
+	(...allocation checks...)
+
+	dummy_physical_memory_cleanup(); /* free the memory */
+}
+
+There's no need to explicitly free the dummy memory from memblock via
+memblock_free() call. The entry will be erased by reset_memblock_regions(),
+called at the beginning of each test.
+
+Known issues
+============
+
+1. Tests for memblock_alloc_low() can't be easily implemented. The function uses
+   ARCH_LOW_ADDRESS_LIMIT marco, which can't be changed to point at the low
+   memory of the memory_block.
+
+References
+==========
+
+1. Boot time memory management documentation page:
+   https://www.kernel.org/doc/html/latest/core-api/boot-time-mm.html