Merge tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Don't destroy user event fields when removal fails

   User event fields are destroyed before the event is removed from
   visibility. But that can fail leaving the still visible event with no
   fields. Move the destroying of the fields to after the event is
   successfully removed from visibility.

 - Initialize function graph state is fork before calling
   copy_exec_state()

   For non-CLONE_VM forks, copy_exec_state() allocates a new
   task_exec_state. If that allocation fails, ftrace_graph_exit_task()
   will free the tasks ret_stack pointer. Since that pointer is still
   using the parent's ret_stack, it mistakenly frees the parent's
   pointer too.

   Call ftrace_graph_init() on the task first which will NULL out the
   new tasks's ret_stack and if the copy fails, it will not free
   anything.

 - Remove FGRAPH_MAX_INDEX

   The macro FGRAPH_MAX_INDEX was added but never used. Remove it.

 - Save ent_size in function graph printing of nested functions

   The function graph tracer needs to look at the next event to see if
   the next event is the return of the current function entry. If it is,
   it prints a single line:

	ktime_get();

   Otherwise it prints it like a nested function:

	tick_nohz_irq_exit() {
	    ktime_get();
	    kcpustat_irq_exit();
	}

   In order to look at the next event, it must save the current event so
   that it has the information to print from it. It saves the event in
   the iterator descriptor called "ent". What it doesn't save is the
   ent_size of the event which is now used to know if the function graph
   arguments are to be printed. The peek doesn't save the size so the
   size used happens to be that of the size of the last event that was
   seen.

   Save the entry event size in the iterator descriptor so that the
   correct size is used.

 - Fix several errors with freeing data in the histogram code

   The histogram code had a lot of leaked or or incorrect accounting
   when failures happen. Correct them.

 - Fix histogram regression of .percent and .graph modifiers

   Up until 6.3 histogram values could have "percent" or "graph"
   modifiers that changed how they were printed. But a change that added
   restricting histograms values from being strings, stack traces and
   other modifiers inadvertently prevented them from using the percent
   and graph modifiers, which were legal use cases for values.

   Put back the percent and graph modifiers.

 - Fix various typos in the comments

 - Set the trace_clock before initializing a histogram with clock
   argument

   The histogram API allows the user to specific which trace clock to
   use via a "clock=" string. The histogram is set up first before the
   clock is checked. If the passed in clock is not valid, it exits
   without fully fixing up the histogram leaving it on the list and a
   use-after-free can trigger.

   Update the clock argument first and if it fails then exit gracefully
   before the histogram trigger is placed on any lists.

 - Restore :mod: trailer after parsing in ftrace_set_clr_event

   The function ftrace_set_clr_event() modifies the parse string and
   needs to put it back to what was passed in. It searches for ":mod:"
   via a strsep() but fails to put back the first ':' in the string.

   Add back the ':' in the passed in string.

 - Take trace_array reference when opening a tracer options file

   The options files are dynamically created and some tracers add their
   own options. When a tracer adds their own list of options, the
   trace_array holding them has an array to hold the list of options for
   each tracer. This array increases in size via a krealloc(), and the
   new entry gets a newly allocated array to hold the options of the new
   tracer being added.

   The element in each entry of the tracer's option array holds a
   pointer back to the trace_array, a pointer to the tracer it is
   associated to, a pointer to the flags of the option.

   The issue is that these arrays are freed when the trace_array is
   freed when its instance it represents is removed from the instances
   directory. There's a race that an open of one of these options files
   can happen when the instance is being removed.

   Add a new helper function to be called by the open function of the
   options file to iterate all existing trace_arrays under a lock and
   find the one that has the given option element in one of it's tracer
   arrays. If found, then update the associated trace_array's reference
   counter to keep it from being freed. If not found, have the open call
   return -ENODEV.

 - Disable interrupts when acquiring the lock in rb_wake_up_waiters()

   The function rb_wake_up_waiters() assumes it will be called in
   interrupt context and does not disable irqs when taking
   cpu_buffer->reader_lock, which can be called in hard interrupt
   context. The issue is in PREEMPT_RT, this function is called in
   thread context leaving this lock open to a deadlock.

   Take the lock with interrupts disabled.

 - Use rcu_assign_pointer() for tmp_ops filter hash

   The tmp_ops used in update_ftrace_direct_mod() assigns its
   filter_hash field directly, but that field is annotated as __rcu and
   sparse complains. Assign it with rcu_assign_pointer()

 - Fix use-after-free in enable_trigger_private_data_free()

   The trace_event_call is accessed through the event_trigger_data's
   trace_event_file pointer to put the trace_event_call on freeing. The
   issue is that the trace_event_file data may have been freed already
   causing a use-after-free. Add a field to the event_trigger_data that
   points directly to the trace_event_call so that it can decrement its
   reference directly without needing to go through the
   trace_event_file.

 - Fix accounting of buffer data remote headers

   trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount
   the number of pages is needed for the asked for size as it doesn't
   take into account the meta data on each page. Add a helper function
   to do the calculation properly and use that in these functions.

 - Catch nr_page_va overflow in ring_buffer_desc sizing

   The number of pages per remote ring buffer is capped by
   ring_buffer_desc::nr_page_va (32 bits). A buffer_size large enough to
   overflow that field would silently allocate a descriptor smaller than
   what was asked for.

 - Do not resize the subbuf order if any per_cpu buffer is disabled

   The mmapping of ring buffers disables resizing the subbuffers, but it
   is done per-cpu whereas the subbuf size change is done for all the
   per_cpu buffers under the buffer->mutex. It could change the size of
   some while the mapping is happening on others. Have the resize of the
   subbuf order check all the per_cpu buffers under the lock to see if
   any of them is disabled before starting and causing an inconsistency
   between buffers that are being mapped.

* tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (25 commits)
  ring-buffer: Check resize_disabled before publishing the new subbuf order
  tracing/remotes: Catch nr_page_va overflow in ring_buffer_desc sizing
  tracing/remotes: Account for ring buffer page header in size calculation
  tracing: Don't dereference trace_event_file in deferred trigger free
  ftrace: Use rcu_assign_pointer() for tmp_ops filter hash
  ring-buffer: Acquire the lock with irqsave in rb_wake_up_waiters()
  tracing: Take trace_array reference when opening a tracer options file
  tracing: Fix ring_buffer_read_page_size() kernel-doc
  tracing: Restore :mod: trailer after parsing in ftrace_set_clr_event()
  tracing: Fix memory corruption from a "STACKTRACE" histogram key
  tracing: Fix memory corruption from the histogram stacktrace modifier
  tracing: Undo the registration when enabling the histogram trigger fails
  tracing: Take the reference before publishing the named histogram trigger
  tracing: Set the trace clock before registering the histogram trigger
  tracing: Fix typo "preceeded" in comment
  tracing: Fix typo "availabe" in comment
  tracing: Let histogram values keep the percent and graph modifiers
  tracing: Keep the entry count when the histogram stats allocation fails
  tracing: Free histogram the field rejected for a bad modifier
  tracing: Free histogram the var ref when its initialization fails
  ...

1 files changed, 392 insertions, 0 deletions

diff --git a/Documentation/admin-guide/dynamic-debug-howto.rst b/Documentation/admin-guide/dynamic-debug-howto.rst
new file mode 100644
index 000000000..9c2f096ed
--- /dev/null
+++ b/Documentation/admin-guide/dynamic-debug-howto.rst
@@ -0,0 +1,392 @@
+Dynamic debug
++++++++++++++
+
+
+Introduction
+============
+
+Dynamic debug allows you to dynamically enable/disable kernel
+debug-print code to obtain additional kernel information.
+
+If ``/proc/dynamic_debug/control`` exists, your kernel has dynamic
+debug.  You'll need root access (sudo su) to use this.
+
+Dynamic debug provides:
+
+ * a Catalog of all *prdbgs* in your kernel.
+   ``cat /proc/dynamic_debug/control`` to see them.
+
+ * a Simple query/command language to alter *prdbgs* by selecting on
+   any combination of 0 or 1 of:
+
+   - source filename
+   - function name
+   - line number (including ranges of line numbers)
+   - module name
+   - format string
+   - class name (as known/declared by each module)
+
+NOTE: To actually get the debug-print output on the console, you may
+need to adjust the kernel ``loglevel=``, or use ``ignore_loglevel``.
+Read about these kernel parameters in
+Documentation/admin-guide/kernel-parameters.rst.
+
+Viewing Dynamic Debug Behaviour
+===============================
+
+You can view the currently configured behaviour in the *prdbg* catalog::
+
+  :#> head -n7 /proc/dynamic_debug/control
+  # filename:lineno [module]function flags format
+  init/main.c:1179 [main]initcall_blacklist =_ "blacklisting initcall %s\n"
+  init/main.c:1218 [main]initcall_blacklisted =_ "initcall %s blacklisted\n"
+  init/main.c:1424 [main]run_init_process =_ "  with arguments:\n"
+  init/main.c:1426 [main]run_init_process =_ "    %s\n"
+  init/main.c:1427 [main]run_init_process =_ "  with environment:\n"
+  init/main.c:1429 [main]run_init_process =_ "    %s\n"
+
+The 3rd space-delimited column shows the current flags, preceded by
+a ``=`` for easy use with grep/cut. ``=p`` shows enabled callsites.
+
+Controlling dynamic debug Behaviour
+===================================
+
+The behaviour of *prdbg* sites are controlled by writing
+query/commands to the control file.  Example::
+
+  # grease the interface
+  :#> alias ddcmd='echo $* > /proc/dynamic_debug/control'
+
+  :#> ddcmd '-p; module main func run* +p'
+  :#> grep =p /proc/dynamic_debug/control
+  init/main.c:1424 [main]run_init_process =p "  with arguments:\n"
+  init/main.c:1426 [main]run_init_process =p "    %s\n"
+  init/main.c:1427 [main]run_init_process =p "  with environment:\n"
+  init/main.c:1429 [main]run_init_process =p "    %s\n"
+
+Error messages go to console/syslog::
+
+  :#> ddcmd mode foo +p
+  dyndbg: unknown keyword "mode"
+  dyndbg: query parse failed
+  bash: echo: write error: Invalid argument
+
+If debugfs is also enabled and mounted, ``dynamic_debug/control`` is
+also under the mount-dir, typically ``/sys/kernel/debug/``.
+
+Command Language Reference
+==========================
+
+At the basic lexical level, a command is a sequence of words separated
+by spaces or tabs.  So these are all equivalent::
+
+  :#> ddcmd file svcsock.c line 1603 +p
+  :#> ddcmd "file svcsock.c line 1603 +p"
+  :#> ddcmd '  file   svcsock.c     line  1603 +p  '
+
+Command submissions are bounded by a write() system call.
+Multiple commands can be written together, separated by ``;`` or ``\n``::
+
+  :#> ddcmd "func pnpacpi_get_resources +p; func pnp_assign_mem +p"
+  :#> ddcmd <<"EOC"
+  func pnpacpi_get_resources +p
+  func pnp_assign_mem +p
+  EOC
+  :#> cat query-batch-file > /proc/dynamic_debug/control
+
+You can also use wildcards in each query term. The match rule supports
+``*`` (matches zero or more characters) and ``?`` (matches exactly one
+character). For example, you can match all usb drivers::
+
+  :#> ddcmd file "drivers/usb/*" +p	# "" to suppress shell expansion
+
+Syntactically, a command is pairs of keyword values, followed by a
+flags change or setting::
+
+  command ::= match-spec* flags-spec
+
+The match-spec's select *prdbgs* from the catalog, upon which to apply
+the flags-spec, all constraints are ANDed together.  An absent keyword
+is the same as keyword "*".
+
+Note that since the match-spec can be empty, the flags are checked 1st,
+then the pairs of keyword and value.  Flag errs will hide keyword errs::
+
+  bash-5.2# ddcmd mod bar +foo
+  dyndbg: read 13 bytes from userspace
+  dyndbg: query 0: "mod bar +foo" mod:*
+  dyndbg: unknown flag 'o'
+  dyndbg: flags parse failed
+  dyndbg: processed 1 queries, with 0 matches, 1 errs
+
+So a match-spec is a keyword, which selects the attribute of the
+callsite to be compared, and a value to compare against.  Possible
+keywords are::
+
+  match-spec ::= 'func' string |
+		 'file' string |
+		 'module' string |
+		 'format' string |
+		 'class' string |
+		 'line' line-range
+
+  line-range ::= lineno |
+		 '-'lineno |
+		 lineno'-' |
+		 lineno'-'lineno
+
+  lineno ::= unsigned-int
+
+.. note::
+
+  ``line-range`` cannot contain space, e.g.
+  "1-30" is valid range but "1 - 30" is not.
+
+
+The meanings of each keyword are:
+
+func
+    The given string is compared against the function name
+    of each callsite.  Example::
+
+	func svc_tcp_accept
+	func *recv*		# in rfcomm, bluetooth, ping, tcp
+
+file
+    The given string is compared against either the src-root relative
+    pathname, or the basename of the source file of each callsite.
+    Examples::
+
+	file svcsock.c
+	file kernel/freezer.c	# ie column 1 of control file
+	file drivers/usb/*	# all callsites under it
+	file inode.c:start_*	# parse :tail as a func (above)
+	file inode.c:1-100	# parse :tail as a line-range (above)
+
+module
+    The given string is compared against the module name
+    of each callsite.  The module name is the string as
+    seen in ``lsmod``, i.e. without the directory or the ``.ko``
+    suffix and with ``-`` changed to ``_``.  Examples::
+
+	module sunrpc
+	module nfsd
+	module drm*	# both drm, drm_kms_helper
+
+format
+    The given string is searched for in the dynamic debug format
+    string.  Note that the string does not need to match the
+    entire format, only some part.  Whitespace and other
+    special characters can be escaped using C octal character
+    escape ``\ooo`` notation, e.g. the space character is ``\040``.
+    Alternatively, the string can be enclosed in double quote
+    characters (``"``) or single quote characters (``'``).
+    Examples::
+
+	format svcrdma:         // many of the NFS/RDMA server pr_debugs
+	format readahead        // some pr_debugs in the readahead cache
+	format nfsd:\040SETATTR // one way to match a format with whitespace
+	format "nfsd: SETATTR"  // a neater way to match a format with whitespace
+	format 'nfsd: SETATTR'  // yet another way to match a format with whitespace
+
+class
+    The given class_name is validated against each module, which may
+    have declared a list of known class_names.  If the class_name is
+    found for a module, callsite & class matching and adjustment
+    proceeds.  Examples::
+
+	class DRM_UT_KMS	# a DRM.debug category
+	class JUNK		# silent non-match
+	// class TLD_*		# NOTICE: no wildcard in class names
+
+line
+    The given line number or range of line numbers is compared
+    against the line number of each ``pr_debug()`` callsite.  A single
+    line number matches the callsite line number exactly.  A
+    range of line numbers matches any callsite between the first
+    and last line number inclusive.  An empty first number means
+    the first line in the file, an empty last line number means the
+    last line number in the file.  Examples::
+
+	line 1603           // exactly line 1603
+	line 1600-1605      // the six lines from line 1600 to line 1605
+	line -1605          // the 1605 lines from line 1 to line 1605
+	line 1600-          // all lines from line 1600 to the end of the file
+
+The flags specification comprises a change operation followed
+by one or more flag characters.  The change operation is one
+of the characters::
+
+  -    remove the given flags
+  +    add the given flags
+  =    set the flags to the given flags
+
+The flags are::
+
+  p    enables the pr_debug() callsite.
+  _    enables no flags.
+
+  Decorator flags add to the message-prefix, in order:
+  t    Include thread ID, or <intr>
+  m    Include module name
+  f    Include the function name
+  s    Include the source file name
+  l    Include line number
+  d    Include call trace
+
+For ``print_hex_dump_debug()`` and ``print_hex_dump_bytes()``, only
+the ``p`` flag has meaning, other flags are ignored.
+
+Note the regexp ``^[-+=][fslmptd_]+$`` matches a flags specification.
+To clear all flags at once, use ``=_`` or ``-fslmptd``.
+
+
+Debug messages during Boot Process
+==================================
+
+To activate debug messages for core code and built-in modules during
+the boot process, even before userspace and debugfs exists, use
+``dyndbg="QUERY"`` or ``module.dyndbg="QUERY"``.  QUERY follows
+the syntax described above, but must not exceed 1023 characters.  Your
+bootloader may impose lower limits.
+
+These ``dyndbg`` params are processed just after the ddebug tables are
+processed, as part of the early_initcall.  Thus you can enable debug
+messages in all code run after this early_initcall via this boot
+parameter.
+
+On an x86 system for example ACPI enablement is a subsys_initcall and::
+
+   dyndbg="file ec.c +p"
+
+will show early Embedded Controller transactions during ACPI setup if
+your machine (typically a laptop) has an Embedded Controller.
+PCI (or other devices) initialization also is a hot candidate for using
+this boot parameter for debugging purposes.
+
+If ``foo`` module is not built-in, ``foo.dyndbg`` will still be processed at
+boot time, without effect, but will be reprocessed when module is
+loaded later. Bare ``dyndbg=`` is only processed at boot.
+
+
+Debug Messages at Module Initialization Time
+============================================
+
+When ``modprobe foo`` is called, modprobe scans ``/proc/cmdline`` for
+``foo.params``, strips ``foo.``, and passes them to the kernel along with
+params given in modprobe args or ``/etc/modprobe.d/*.conf`` files,
+in the following order:
+
+1. parameters given via ``/etc/modprobe.d/*.conf``::
+
+	options foo dyndbg=+pt
+	options foo dyndbg # defaults to +p
+
+2. ``foo.dyndbg`` as given in boot args, ``foo.`` is stripped and passed::
+
+	foo.dyndbg=" func bar +p; func buz +mp"
+
+3. args to modprobe::
+
+	modprobe foo dyndbg==pmf # override previous settings
+
+These ``dyndbg`` queries are applied in order, with last having final say.
+This allows boot args to override or modify those from ``/etc/modprobe.d``
+(sensible, since 1 is system wide, 2 is kernel or boot specific), and
+modprobe args to override both.
+
+In the ``foo.dyndbg="QUERY"`` form, the query must exclude ``module foo``.
+``foo`` is extracted from the param-name, and applied to each query in
+``QUERY``, and only 1 match-spec of each type is allowed.
+
+The ``dyndbg`` option is a "fake" module parameter, which means:
+
+- modules do not need to define it explicitly
+- every module gets it tacitly, whether they use pr_debug or not
+- it doesn't appear in ``/sys/module/$module/parameters/``
+  To see it, grep the control file, or inspect ``/proc/cmdline.``
+
+For ``CONFIG_DYNAMIC_DEBUG`` kernels, any settings given at boot-time (or
+enabled by ``-DDEBUG`` flag during compilation) can be disabled later via
+the debugfs interface if the debug messages are no longer needed::
+
+   echo "module module_name -p" > /proc/dynamic_debug/control
+
+Examples
+========
+
+::
+
+  // enable the message at line 1603 of file svcsock.c
+  :#> ddcmd 'file svcsock.c line 1603 +p'
+
+  // enable all the messages in file svcsock.c
+  :#> ddcmd 'file svcsock.c +p'
+
+  // enable all the messages in the NFS server module
+  :#> ddcmd 'module nfsd +p'
+
+  // enable all 12 messages in the function svc_process()
+  :#> ddcmd 'func svc_process +p'
+
+  // disable all 12 messages in the function svc_process()
+  :#> ddcmd 'func svc_process -p'
+
+  // enable messages for NFS calls READ, READLINK, READDIR and READDIR+.
+  :#> ddcmd 'format "nfsd: READ" +p'
+
+  // enable messages in files of which the paths include string "usb"
+  :#> ddcmd 'file *usb* +p'
+
+  // enable all messages
+  :#> ddcmd '+p'
+
+  // add module, function to all enabled messages
+  :#> ddcmd '+mf'
+
+  // boot-args example, with newlines and comments for readability
+  Kernel command line: ...
+    // see what's going on in dyndbg=value processing
+    dynamic_debug.verbose=3
+    // enable pr_debugs in the btrfs module (can be builtin or loadable)
+    btrfs.dyndbg="+p"
+    // enable pr_debugs in all files under init/
+    // and the function parse_one, #cmt is stripped
+    dyndbg="file init/* +p #cmt ; func parse_one +p"
+    // enable pr_debugs in 2 functions in a module loaded later
+    pc87360.dyndbg="func pc87360_init_device +p; func pc87360_find +p"
+
+Kernel Configuration
+====================
+
+Dynamic Debug is enabled via kernel config items::
+
+  CONFIG_DYNAMIC_DEBUG=y	# build catalog, enables CORE
+  CONFIG_DYNAMIC_DEBUG_CORE=y	# enable mechanics only, skip catalog
+
+If you do not want to enable dynamic debug globally (i.e. in some embedded
+system), you may set ``CONFIG_DYNAMIC_DEBUG_CORE`` as basic support of dynamic
+debug and add ``ccflags := -DDYNAMIC_DEBUG_MODULE`` into the Makefile of any
+modules which you'd like to dynamically debug later.
+
+
+Kernel *prdbg* API
+==================
+
+The following functions are cataloged and controllable when dynamic
+debug is enabled::
+
+  pr_debug()
+  dev_dbg()
+  print_hex_dump_debug()
+  print_hex_dump_bytes()
+
+Otherwise, they are off by default; ``ccflags += -DDEBUG`` or
+``#define DEBUG`` in a source file will enable them appropriately.
+
+If ``CONFIG_DYNAMIC_DEBUG`` is not set, ``print_hex_dump_debug()`` is
+just a shortcut for ``print_hex_dump(KERN_DEBUG)``.
+
+For ``print_hex_dump_debug()``/``print_hex_dump_bytes()``, format string is
+its ``prefix_str`` argument, if it is constant string; or ``hexdump``
+in case ``prefix_str`` is built dynamically.