Merge branch 'perf-core-for-linus' of...

!Iinclude/trace/events/irq.h

  </chapter>

  <chapter id="signal">

   <title>SIGNAL</title>

!Iinclude/trace/events/signal.h

  </chapter>

</book>

                        Kprobe-based Event Tracing

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

                 Documentation is written by Masami Hiramatsu

Overview

--------

These events are similar to tracepoint based events. Instead of Tracepoint,

this is based on kprobes (kprobe and kretprobe). So it can probe wherever

kprobes can probe (this means, all functions body except for __kprobes

functions). Unlike the Tracepoint based event, this can be added and removed

dynamically, on the fly.

To enable this feature, build your kernel with CONFIG_KPROBE_TRACING=y.

Similar to the events tracer, this doesn't need to be activated via

current_tracer. Instead of that, add probe points via

/sys/kernel/debug/tracing/kprobe_events, and enable it via

/sys/kernel/debug/tracing/events/kprobes/<EVENT>/enabled.

Synopsis of kprobe_events

-------------------------

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

  r[:[GRP/]EVENT] SYMBOL[+0] [FETCHARGS]		: Set a return probe

 GRP		: Group name. If omitted, use "kprobes" for it.

 EVENT		: Event name. If omitted, the event name is generated

		  based on SYMBOL+offs or MEMADDR.

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

 MEMADDR	: Address where the probe is inserted.

 FETCHARGS	: Arguments. Each probe can have up to 128 args.

  %REG		: Fetch register REG

  @ADDR		: Fetch memory at ADDR (ADDR should be in kernel)

  @SYM[+|-offs]	: Fetch memory at SYM +|- offs (SYM should be a data symbol)

  $stackN	: Fetch Nth entry of stack (N >= 0)

  $stack	: Fetch stack address.

  $argN		: Fetch function argument. (N >= 0)(*)

  $retval	: Fetch return value.(**)

  +|-offs(FETCHARG) : Fetch memory at FETCHARG +|- offs address.(***)

  NAME=FETCHARG: Set NAME as the argument name of FETCHARG.

  (*) aN may not correct on asmlinkaged functions and at the middle of

      function body.

  (**) only for return probe.

  (***) this is useful for fetching a field of data structures.

Per-Probe Event Filtering

-------------------------

 Per-probe event filtering feature allows you to set different filter on each

probe and gives you what arguments will be shown in trace buffer. If an event

name is specified right after 'p:' or 'r:' in kprobe_events, it adds an event

under tracing/events/kprobes/<EVENT>, at the directory you can see 'id',

'enabled', 'format' and 'filter'.

enabled:

  You can enable/disable the probe by writing 1 or 0 on it.

format:

  This shows the format of this probe event.

filter:

  You can write filtering rules of this event.

id:

  This shows the id of this probe event.

Event Profiling

---------------

 You can check the total number of probe hits and probe miss-hits via

/sys/kernel/debug/tracing/kprobe_profile.

 The first column is event name, the second is the number of probe hits,

the third is the number of probe miss-hits.

Usage examples

--------------

To add a probe as a new event, write a new definition to kprobe_events

as below.

  echo p:myprobe do_sys_open dfd=$arg0 filename=$arg1 flags=$arg2 mode=$arg3 > /sys/kernel/debug/tracing/kprobe_events

 This sets a kprobe on the top of do_sys_open() function with recording

1st to 4th arguments as "myprobe" event. As this example shows, users can

choose more familiar names for each arguments.

  echo r:myretprobe do_sys_open $retval >> /sys/kernel/debug/tracing/kprobe_events

 This sets a kretprobe on the return point of do_sys_open() function with

recording return value as "myretprobe" event.

 You can see the format of these events via

/sys/kernel/debug/tracing/events/kprobes/<EVENT>/format.

  cat /sys/kernel/debug/tracing/events/kprobes/myprobe/format

name: myprobe

ID: 75

format:

	field:unsigned short common_type;	offset:0;	size:2;

	field:unsigned char common_flags;	offset:2;	size:1;

	field:unsigned char common_preempt_count;	offset:3;	size:1;

	field:int common_pid;	offset:4;	size:4;

	field:int common_tgid;	offset:8;	size:4;

	field: unsigned long ip;	offset:16;tsize:8;

	field: int nargs;	offset:24;tsize:4;

	field: unsigned long dfd;	offset:32;tsize:8;

	field: unsigned long filename;	offset:40;tsize:8;

	field: unsigned long flags;	offset:48;tsize:8;

	field: unsigned long mode;	offset:56;tsize:8;

print fmt: "(%lx) dfd=%lx filename=%lx flags=%lx mode=%lx", REC->ip, REC->dfd, REC->filename, REC->flags, REC->mode

 You can see that the event has 4 arguments as in the expressions you specified.

  echo > /sys/kernel/debug/tracing/kprobe_events

 This clears all probe points.

 Right after definition, each event is disabled by default. For tracing these

events, you need to enable it.

  echo 1 > /sys/kernel/debug/tracing/events/kprobes/myprobe/enable

  echo 1 > /sys/kernel/debug/tracing/events/kprobes/myretprobe/enable

 And you can see the traced information via /sys/kernel/debug/tracing/trace.

  cat /sys/kernel/debug/tracing/trace

# tracer: nop

#

#           TASK-PID    CPU#    TIMESTAMP  FUNCTION

#              | |       |          |         |

           <...>-1447  [001] 1038282.286875: myprobe: (do_sys_open+0x0/0xd6) dfd=3 filename=7fffd1ec4440 flags=8000 mode=0

           <...>-1447  [001] 1038282.286878: myretprobe: (sys_openat+0xc/0xe <- do_sys_open) $retval=fffffffffffffffe

           <...>-1447  [001] 1038282.286885: myprobe: (do_sys_open+0x0/0xd6) dfd=ffffff9c filename=40413c flags=8000 mode=1b6

           <...>-1447  [001] 1038282.286915: myretprobe: (sys_open+0x1b/0x1d <- do_sys_open) $retval=3

           <...>-1447  [001] 1038282.286969: myprobe: (do_sys_open+0x0/0xd6) dfd=ffffff9c filename=4041c6 flags=98800 mode=10

           <...>-1447  [001] 1038282.286976: myretprobe: (sys_open+0x1b/0x1d <- do_sys_open) $retval=3

 Each line shows when the kernel hits an event, and <- SYMBOL means kernel

returns from SYMBOL(e.g. "sys_open+0x1b/0x1d <- do_sys_open" means kernel

returns from do_sys_open to sys_open+0x1b).

config HAVE_DEFAULT_NO_SPIN_MUTEXES

	bool

config HAVE_HW_BREAKPOINT

	bool

	depends on HAVE_PERF_EVENTS

	select ANON_INODES

	select PERF_EVENTS

source "kernel/gcov/Kconfig"

config HCALL_STATS

	bool "Hypervisor call instrumentation"

	depends on PPC_PSERIES && DEBUG_FS

	depends on PPC_PSERIES && DEBUG_FS && TRACEPOINTS

	help

	  Adds code to keep track of the number of hypervisor calls made and

	  the amount of time spent in hypervisor calls.  Wall time spent in

CONFIG_DEBUG_STACKOVERFLOW=y

# CONFIG_DEBUG_STACK_USAGE is not set

# CONFIG_DEBUG_PAGEALLOC is not set

CONFIG_HCALL_STATS=y

# CONFIG_HCALL_STATS is not set

# CONFIG_CODE_PATCHING_SELFTEST is not set

# CONFIG_FTR_FIXUP_SELFTEST is not set

# CONFIG_MSI_BITMAP_SELFTEST is not set