Commit fefa636d authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'trace-v5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace 

Pull tracing updates from Steven Rostedt:
 "Updates for tracing and bootconfig:

   - Add support for "bool" type in synthetic events

   - Add per instance tracing for bootconfig

   - Support perf-style return probe ("SYMBOL%return") in kprobes and
     uprobes

   - Allow for kprobes to be enabled earlier in boot up

   - Added tracepoint helper function to allow testing if tracepoints
     are enabled in headers

   - Synthetic events can now have dynamic strings (variable length)

   - Various fixes and cleanups"

* tag 'trace-v5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (58 commits)
  tracing: support "bool" type in synthetic trace events
  selftests/ftrace: Add test case for synthetic event syntax errors
  tracing: Handle synthetic event array field type checking correctly
  selftests/ftrace: Change synthetic event name for inter-event-combined test
  tracing: Add synthetic event error logging
  tracing: Check that the synthetic event and field names are legal
  tracing: Move is_good_name() from trace_probe.h to trace.h
  tracing: Don't show dynamic string internals in synthetic event description
  tracing: Fix some typos in comments
  tracing/boot: Add ftrace.instance.*.alloc_snapshot option
  tracing: Fix race in trace_open and buffer resize call
  tracing: Check return value of __create_val_fields() before using its result
  tracing: Fix synthetic print fmt check for use of __get_str()
  tracing: Remove a pointless assignment
  ftrace: ftrace_global_list is renamed to ftrace_ops_list
  ftrace: Format variable declarations of ftrace_allocate_records
  ftrace: Simplify the calculation of page number for ftrace_page->records
  ftrace: Simplify the dyn_ftrace->flags macro
  ftrace: Simplify the hash calculation
  ftrace: Use fls() to get the bits for dup_hash()
  ...
parents 2d0f6b0a 6107742d

Documentation/trace/boottime-trace.rst

+38 −0
Original line number Diff line number Diff line
@@ -61,6 +61,10 @@ These options can be used for each instance including global ftrace node. 
ftrace.[instance.INSTANCE.]options = OPT1[, OPT2[...]]

   Enable given ftrace options.



ftrace.[instance.INSTANCE.]tracing_on = 0|1

   Enable/Disable tracing on this instance when starting boot-time tracing.

   (you can enable it by the "traceon" event trigger action)



ftrace.[instance.INSTANCE.]trace_clock = CLOCK

   Set given CLOCK to ftrace's trace_clock.
@@ -116,6 +120,20 @@ instance node, but those are also visible from other instances. So please 
take care for event name conflict.





When to Start

=============



All boot-time tracing options starting with ``ftrace`` will be enabled at the

end of core_initcall. This means you can trace the events from postcore_initcall.

Most of the subsystems and architecture dependent drivers will be initialized

after that (arch_initcall or subsys_initcall). Thus, you can trace those with

boot-time tracing.

If you want to trace events before core_initcall, you can use the options

starting with ``kernel``. Some of them will be enabled eariler than the initcall

processing (for example,. ``kernel.ftrace=function`` and ``kernel.trace_event``

will start before the initcall.)





Examples

========
@@ -164,6 +182,26 @@ is for tracing functions starting with "user\_", and others tracing 
The instance node also accepts event nodes so that each instance

can customize its event tracing.



With the trigger action and kprobes, you can trace function-graph while

a function is called. For example, this will trace all function calls in

the pci_proc_init()::



  ftrace {

        tracing_on = 0

        tracer = function_graph

        event.kprobes {

                start_event {

                        probes = "pci_proc_init"

                        actions = "traceon"

                }

                end_event {

                        probes = "pci_proc_init%return"

                        actions = "traceoff"

                }

        }

  }





This boot-time tracing also supports ftrace kernel parameters via boot

config.

For example, following kernel parameters::

Documentation/trace/events.rst

+13 −2
Original line number Diff line number Diff line
@@ -589,8 +589,19 @@ name:: 
        { .type = "int",                .name = "my_int_field" },

  };



See synth_field_size() for available types. If field_name contains [n]

the field is considered to be an array.

See synth_field_size() for available types.



If field_name contains [n], the field is considered to be a static array.



If field_names contains[] (no subscript), the field is considered to

be a dynamic array, which will only take as much space in the event as

is required to hold the array.



Because space for an event is reserved before assigning field values

to the event, using dynamic arrays implies that the piecewise

in-kernel API described below can't be used with dynamic arrays.  The

other non-piecewise in-kernel APIs can, however, be used with dynamic

arrays.



If the event is created from within a module, a pointer to the module

must be passed to synth_event_create().  This will ensure that the

Documentation/trace/histogram.rst

+18 −0
Original line number Diff line number Diff line
@@ -1776,6 +1776,24 @@ consisting of the name of the new event along with one or more 
variables and their types, which can be any valid field type,

separated by semicolons, to the tracing/synthetic_events file.



See synth_field_size() for available types.



If field_name contains [n], the field is considered to be a static array.



If field_names contains[] (no subscript), the field is considered to

be a dynamic array, which will only take as much space in the event as

is required to hold the array.



A string field can be specified using either the static notation:



  char name[32];



Or the dynamic:



  char name[];



The size limit for either is 256.



For instance, the following creates a new event named 'wakeup_latency'

with 3 fields: lat, pid, and prio.  Each of those fields is simply a

variable reference to a variable on another event::

Documentation/trace/kprobetrace.rst

+2 −0
Original line number Diff line number Diff line
@@ -30,6 +30,7 @@ Synopsis of kprobe_events 


  p[:[GRP/]EVENT] [MOD:]SYM[+offs]|MEMADDR [FETCHARGS]	: Set a probe

  r[MAXACTIVE][:[GRP/]EVENT] [MOD:]SYM[+0] [FETCHARGS]	: Set a return probe

  p:[GRP/]EVENT] [MOD:]SYM[+0]%return [FETCHARGS]	: Set a return probe

  -:[GRP/]EVENT						: Clear a probe



 GRP		: Group name. If omitted, use "kprobes" for it.
@@ -37,6 +38,7 @@ Synopsis of kprobe_events 
		  based on SYM+offs or MEMADDR.

 MOD		: Module name which has given SYM.

 SYM[+offs]	: Symbol+offset where the probe is inserted.

 SYM%return	: Return address of the symbol

 MEMADDR	: Address where the probe is inserted.

 MAXACTIVE	: Maximum number of instances of the specified function that

		  can be probed simultaneously, or 0 for the default value

Documentation/trace/tracepoints.rst

+27 −0
Original line number Diff line number Diff line
@@ -146,3 +146,30 @@ with jump labels and avoid conditional branches. 
      define tracepoints. Check http://lwn.net/Articles/379903,

      http://lwn.net/Articles/381064 and http://lwn.net/Articles/383362

      for a series of articles with more details.



If you require calling a tracepoint from a header file, it is not

recommended to call one directly or to use the trace_<tracepoint>_enabled()

function call, as tracepoints in header files can have side effects if a

header is included from a file that has CREATE_TRACE_POINTS set, as

well as the trace_<tracepoint>() is not that small of an inline

and can bloat the kernel if used by other inlined functions. Instead,

include tracepoint-defs.h and use tracepoint_enabled().



In a C file::



	void do_trace_foo_bar_wrapper(args)

	{

		trace_foo_bar(args);

	}



In the header file::



	DECLARE_TRACEPOINT(foo_bar);



	static inline void some_inline_function()

	{

		[..]

		if (tracepoint_enabled(foo_bar))

			do_trace_foo_bar_wrapper(args);

		[..]

	}

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