Impact: extend and enable the function graph tracer to 64-bit x86

This patch implements the support for function graph tracer under x86-64.
Both static and dynamic tracing are supported.

This causes some small CPP conditional asm on arch/x86/kernel/ftrace.c I
wanted to use probe_kernel_read/write to make the return address
saving/patching code more generic but it causes tracing recursion.

That would be perhaps useful to implement a notrace version of these
function for other archs ports.

Note that arch/x86/process_64.c is not traced, as in X86-32. I first
thought __switch_to() was responsible of crashes during tracing because I
believed current task were changed inside but that's actually not the
case (actually yes, but not the "current" pointer).

So I will have to investigate to find the functions that harm here, to
enable tracing of the other functions inside (but there is no issue at
this time, while process_64.c stays out of -pg flags).

A little possible race condition is fixed inside this patch too. When the
tracer allocate a return stack dynamically, the current depth is not
initialized before but after. An interrupt could occur at this time and,
after seeing that the return stack is allocated, the tracer could try to
trace it with a random uninitialized depth. It's a prevention, even if I
hadn't problems with it.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tim Bird <tim.bird@am.sony.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: fix "no output from tracer" bug caused by ftrace_update_pid_func()

When disabling single thread function trace using
"echo -1 > set_ftrace_pid", the normal function trace
has to restore to original function, otherwise the normal
function trace will not work well.

Without this commit, something like below:

	$ ps |grep 850
	  850 root      2556 S    -/bin/sh
	$ echo 850 > /debug/tracing/set_ftrace_pid
	$ echo function > /debug/tracing/current_tracer
	$ echo 1 > /debug/tracing/tracing_enabled
	$ sleep 1
	$ echo 0 > /debug/tracing/tracing_enabled
	$ cat /debug/tracing/trace_pipe |wc -l
	59704
	$ echo -1 > /debug/tracing/set_ftrace_pid
	$ echo 1 > /debug/tracing/tracing_enabled
	$ sleep 1
	$ echo 0 > /debug/tracing/tracing_enabled
	$ more /debug/tracing/trace_pipe
		<====== nothing output now!
			it should output trace record.
Signed-off-by: NLiming Wang <liming.wang@windriver.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Merge branches 'tracing/branch-tracer', 'tracing/ftrace', 'tracing/function-graph-tracer', 'tracing/markers', 'tracing/powerpc', 'tracing/stack-tracer' and 'tracing/tracepoints' into tracing/core

Conflicts:
	kernel/trace/ring_buffer.c

Impact: fix typo in documentation

TPPROTO is misspelt in Documentation/tracepoints.txt
Kept me wondering what was wrong, when I was trying to add a new tracepoint
subsystem.
Signed-off-by: NNikanth Karthikesan <knikanth@suse.de>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: fix build error on branch tracer

This should fix a build error reported on alpha in linux-next:

 CC      kernel/trace/trace_branch.o
  kernel/trace/trace_branch.c: In function 'probe_likely_condition':
  kernel/trace/trace_branch.c:44: error: implicit declaration of function 'raw_local_irq_save'
  kernel/trace/trace_branch.c:76: error: implicit declaration of function 'raw_local_irq_restore'

Unfortunately, I can't test it since I don't have any Alpha build environment.
Reported-by: NAlexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

mangle_path() is trivial enough to make  export restrictions on it
pointless - so change the export from EXPORT_SYMBOL_GPL to EXPORT_SYMBOL.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Acked-by: NAl Viro <viro@ZenIV.linux.org.uk>

Add document and comments on marker_synchronize_unregister(): it
should be called before freeing resources that the probes depend on.

Based on comments from Lai Jiangshan and Mathieu Desnoyers.
Signed-off-by: NWu Fengguang <wfg@linux.intel.com>
Reviewed-by: NMathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Reviewed-by: NLai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: fix for PowerPC 32 code

There were some early init code that was not safe for static
ftrace to boot on my PowerBook. This code must only use relative
addressing, and static mcount performs a compare of the
ftrace_trace_function pointer, and gets that with an absolute address.
In the early init boot up code, this will cause a fault.

This patch removes tracing from the files containing the offending
functions.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: clean up

Paul Mackerras pointed out that the code to determine if the branch
can reach the destination is incorrect. Michael Ellerman suggested
to pull out the code from create_branch and use that.

Simply using create_branch is probably the best.
Reported-by: NMichael Ellerman <michael@ellerman.id.au>
Reported-by: NPaul Mackerras <paulus@samba.org>
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: fix to PowerPC code modification

After modifying code it is essential to flush the icache. This patch
adds the missing flush.
Reported-by: NPaul Mackerras <paulus@samba.org>
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: clean up and robustness addition

This patch addresses the comments made by Paul Mackerras.
It removes the type casting between unsigned int and unsigned char
pointers, and replaces them with a use of all unsigned int.

Verification that the jump is indeed made to a trampoline has also
been added.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: quicken mcount calls that are not replaced by dyn ftrace

Dynamic ftrace no longer does on the fly recording of mcount locations.
The mcount locations are now found at compile time. The mcount
function no longer needs to store registers and call a stub function.
It can now just simply return.

Since there are some functions that do not get converted to a nop
(.init sections and other code that may disappear), this patch should
help speed up that code.

Also, the stub for mcount on PowerPC 32 can not be a simple branch
link register like it is on PowerPC 64. According to the ABI specification:

"The _mcount routine is required to restore the link register from
 the stack so that the profiling code can be inserted transparently,
 whether or not the profiled function saves the link register itself."

This means that we must restore the link register that was used
to make the call to mcount.  The minimal mcount function for PPC32
ends up being:

 mcount:
        mflr    r0
        mtctr   r0
        lwz     r0, 4(r1)
        mtlr    r0
        bctr

Where we move the link register used to call mcount into the
ctr register, and then restore the link register from the stack.
Then we use the ctr register to jump back to the mcount caller.
The r0 register is free for us to use.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: extend documentation with notice of using wild cards correctly

We know that we can use wild cards to set set_ftrace_filter, but there's
problem when using them naively such as:

   echo h* > /debug/tracing/set_ftrace_filter

If there are files named with "h" prefix in current directory,
echo "h*" will echo these filenames to set_ftrace_filter, not the
intended "h*".

For example:

  $ cat /debug/tracing/available_filter_functions |grep ^hr |wc -l
  23
  $ ls
  $ touch hraa hrdd
  $ ls
  hraa  hrdd
  $ echo hr* > /debug/tracing/set_ftrace_filter
  $ cat /debug/tracing/set_ftrace_filter

No output in /debug/tracing/set_ftrace_filter!

If we use '' to escape wild cards, it works:

  $ ls
  hraa  hrdd
  $ echo "hr*" > /debug/tracing/set_ftrace_filter
  $ cat /debug/tracing/set_ftrace_filter |wc -l
  23

This problem can lead to unexpected result if current directory has a
lot of files.
Signed-off-by: Nwalimis <walimisdev@gmail.com>
Acked-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: make ftrace position computing more sane

First remove useless ->pos field. Then we needn't check seq_printf
in .show like other place.
Signed-off-by: NLiming Wang <liming.wang@windriver.com>
Reviewed-by: NBruce Ashfield <bruce.ashfield@windriver.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

There are architectures that still have no stacktrace support.
Signed-off-by: NTörök Edwin <edwintorok@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: prettify the output some more

Before:

0)           |     sys_read() {
0)      0.796 us |   fget_light();
0)           |       vfs_read() {
0)           |         rw_verify_area() {
0)           |           security_file_permission() {
------------8<---------- thread sshd-1755 ------------8<----------

After:

 0)               |  sys_read() {
 0)      0.796 us |    fget_light();
 0)               |    vfs_read() {
 0)               |      rw_verify_area() {
 0)               |        security_file_permission() {
 ------------------------------------------
 | 1)  migration/0--1  =>  sshd-1755
 ------------------------------------------
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: increase the visual qualities of the call-graph-tracer output

This patch applies various trace output formatting changes:

 - CPU is now a decimal number, followed by a parenthesis.

 - Overhead is now on the second column (gives a good visibility)

 - Cost is now on the third column, can't exceed 9999.99 us. It is
   followed by a virtual line based on a "|" character.

 - Functions calls are now the last column on the right. This way, we
   haven't dynamic column (which flow is harder to follow) on its right.

 - CPU and Overhead have their own option flag. They are default-on but you
   can disable them easily:

      echo nofuncgraph-cpu > trace_options
      echo nofuncgraph-overhead > trace_options

TODO:

_ Refactoring of the thread switch output.
_ Give a default-off option to output the thread and its pid on each row.
_ Provide headers
_ ....

Here is an example of the new trace style:

0)           |             mutex_unlock() {
0)      0.639 us |           __mutex_unlock_slowpath();
0)      1.607 us |         }
0)           |             remove_wait_queue() {
0)      0.616 us |           _spin_lock_irqsave();
0)      0.616 us |           _spin_unlock_irqrestore();
0)      2.779 us |         }
0)      0.495 us |         n_tty_set_room();
0) ! 9999.999 us |       }
0)           |           tty_ldisc_deref() {
0)      0.615 us |         _spin_lock_irqsave();
0)      0.616 us |         _spin_unlock_irqrestore();
0)      2.793 us |       }
0)           |           current_fs_time() {
0)      0.488 us |         current_kernel_time();
0)      0.495 us |         timespec_trunc();
0)      2.486 us |       }
0) ! 9999.999 us |     }
0) ! 9999.999 us |   }
0) ! 9999.999 us | }
0)           |     sys_read() {
0)      0.796 us |   fget_light();
0)           |       vfs_read() {
0)           |         rw_verify_area() {
0)           |           security_file_permission() {
0)      0.488 us |         cap_file_permission();
0)      1.720 us |       }
0)      3.  4 us |     }
0)           |         tty_read() {
0)      0.488 us |       tty_paranoia_check();
0)           |           tty_ldisc_ref_wait() {
0)           |             tty_ldisc_try() {
0)      0.615 us |           _spin_lock_irqsave();
0)      0.615 us |           _spin_unlock_irqrestore();
0)      5.436 us |         }
0)      6.427 us |       }
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: enhance the output of the graph-tracer

This patch applies some ideas of Ingo Molnar and Steven Rostedt.

* Output leaf functions in one line with parenthesis, semicolon and duration
  output.

* Add a second column (after cpu) for an overhead sign.
  if duration > 100 us, "!"
  if duration > 10 us, "+"
  else " "

* Print output in us with remaining nanosec: u.n

* Print duration on the right end, following the indentation of the functions.
  Use also visual clues: "-" on entry call (no duration to output) and "+" on
  return (duration output).

The name of the tracer has been fixed as well: function-branch becomes
function_branch.

Here is an example of the new output:

CPU[000]           dequeue_entity() {                    -
CPU[000]             update_curr() {                    -
CPU[000]               update_min_vruntime();                    + 0.512 us
CPU[000]             }                                + 1.504 us
CPU[000]             clear_buddies();                    + 0.481 us
CPU[000]             update_min_vruntime();                    + 0.504 us
CPU[000]           }                                + 4.557 us
CPU[000]           hrtick_update() {                    -
CPU[000]             hrtick_start_fair();                    + 0.489 us
CPU[000]           }                                + 1.443 us
CPU[000] +       }                                + 14.655 us
CPU[000] +     }                                + 15.678 us
CPU[000] +   }                                + 16.686 us
CPU[000]     msecs_to_jiffies();                    + 0.481 us
CPU[000]     put_prev_task_fair();                    + 0.504 us
CPU[000]     pick_next_task_fair();                    + 0.482 us
CPU[000]     pick_next_task_rt();                    + 0.504 us
CPU[000]     pick_next_task_fair();                    + 0.481 us
CPU[000]     pick_next_task_idle();                    + 0.489 us
CPU[000]     _spin_trylock();                    + 0.655 us
CPU[000]     _spin_unlock();                    + 0.609 us

CPU[000]  ------------8<---------- thread bash-2794 ------------8<----------

CPU[000]               finish_task_switch() {                    -
CPU[000]                 _spin_unlock_irq();                    + 0.722 us
CPU[000]               }                                + 2.369 us
CPU[000] !           }                                + 501972.605 us
CPU[000] !         }                                + 501973.763 us
CPU[000]           copy_from_read_buf() {                    -
CPU[000]             _spin_lock_irqsave();                    + 0.670 us
CPU[000]             _spin_unlock_irqrestore();                    + 0.699 us
CPU[000]             copy_to_user() {                    -
CPU[000]               might_fault() {                    -
CPU[000]                 __might_sleep();                    + 0.503 us
CPU[000]               }                                + 1.632 us
CPU[000]               __copy_to_user_ll();                    + 0.542 us
CPU[000]             }                                + 3.858 us
CPU[000]             tty_audit_add_data() {                    -
CPU[000]               _spin_lock_irq();                    + 0.609 us
CPU[000]               _spin_unlock_irq();                    + 0.624 us
CPU[000]             }                                + 3.196 us
CPU[000]             _spin_lock_irqsave();                    + 0.624 us
CPU[000]             _spin_unlock_irqrestore();                    + 0.625 us
CPU[000] +         }                                + 13.611 us
CPU[000]           copy_from_read_buf() {                    -
CPU[000]             _spin_lock_irqsave();                    + 0.624 us
CPU[000]             _spin_unlock_irqrestore();                    + 0.616 us
CPU[000]           }                                + 2.820 us
CPU[000]
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Merge branches 'tracing/blktrace', 'tracing/ftrace', 'tracing/function-graph-tracer' and 'tracing/power-tracer' into tracing/core

Impact: prevent unnecessary stack recursion

if the resched flag was set before we entered, then don't reschedule.
Signed-off-by: NLai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Port to the new tracepoints API: split DEFINE_TRACE() and DECLARE_TRACE()
sites. Spread them out to the usage sites, as suggested by
Mathieu Desnoyers.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Acked-by: NMathieu Desnoyers <mathieu.desnoyers@polymtl.ca>

This was a forward port of work done by Mathieu Desnoyers, I changed it to
encode the 'what' parameter on the tracepoint name, so that one can register
interest in specific events and not on classes of events to then check the
'what' parameter.
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: new "power-tracer" ftrace plugin

This patch adds a C/P-state ftrace plugin that will generate
detailed statistics about the C/P-states that are being used,
so that we can look at detailed decisions that the C/P-state
code is making, rather than the too high level "average"
that we have today.

An example way of using this is:

 mount -t debugfs none /sys/kernel/debug
 echo cstate > /sys/kernel/debug/tracing/current_tracer
 echo 1 > /sys/kernel/debug/tracing/tracing_enabled
 sleep 1
 echo 0 > /sys/kernel/debug/tracing/tracing_enabled
 cat /sys/kernel/debug/tracing/trace | perl scripts/trace/cstate.pl > out.svg
Signed-off-by: NArjan van de Ven <arjan@linux.intel.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: enhancement for function graph tracer

When run on a SMP box, the function graph tracer is confusing because
it shows the different CPUS as changes in the trace.

This patch adds the annotation of 'CPU[###]' where ### is a three digit
number. The output will look similar to this:

CPU[001]     dput() {
CPU[000] } 726
CPU[001]     } 487
CPU[000] do_softirq() {
CPU[001]   } 2221
CPU[000]   __do_softirq() {
CPU[000]     __local_bh_disable() {
CPU[001]   unroll_tree_refs() {
CPU[000]     } 569
CPU[001]   } 501
CPU[000]     rcu_process_callbacks() {
CPU[001]   kfree() {

What makes this nice is that now you can grep the file and produce
readable format for a particular CPU.

 # cat /debug/tracing/trace > /tmp/trace
 # grep '^CPU\[000\]' /tmp/trace > /tmp/trace0
 # grep '^CPU\[001\]' /tmp/trace > /tmp/trace1

Will give you:

 # head /tmp/trace0
CPU[000] ------------8<---------- thread sshd-3899 ------------8<----------
CPU[000]     inotify_dentry_parent_queue_event() {
CPU[000]     } 2531
CPU[000]     inotify_inode_queue_event() {
CPU[000]     } 505
CPU[000]   } 69626
CPU[000] } 73089
CPU[000] audit_syscall_exit() {
CPU[000]   path_put() {
CPU[000]     dput() {

 # head /tmp/trace1
CPU[001] ------------8<---------- thread pcscd-3446 ------------8<----------
CPU[001]               } 4186
CPU[001]               dput() {
CPU[001]               } 543
CPU[001]               vfs_permission() {
CPU[001]                 inode_permission() {
CPU[001]                   shmem_permission() {
CPU[001]                     generic_permission() {
CPU[001]                     } 501
CPU[001]                   } 2205
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: enhancement to function graph tracer

Export the trace_find_cmdline so the function graph tracer can
use it to print the comms of the threads.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: feature

This patch enables function tracing and function return to run together.
I've tested this by enabling the stack tracer and return tracer, where
both the function entry and function return are used together with
dynamic ftrace.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: more efficient code for ftrace graph tracer

This patch uses the dynamic patching, when available, to patch
the function graph code into the kernel.

This patch will ease the way for letting both function tracing
and function graph tracing run together.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: feature to function trace a single thread

This patch adds the ability to function trace a single thread.
The file:

  /debugfs/tracing/set_ftrace_pid

contains the pid to trace. Valid pids are any positive integer.
Writing any negative number to this file will disable the pid
tracing and the function tracer will go back to tracing all of
threads.

This feature works with both static and dynamic function tracing.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: widen the scope of recordmcount.pl

Besides .text section, there are three .text sections that won't
be freed after kernel booting. They are: .sched.text, .spinlock.text
and .kprobes.text, which contain functions we can trace. But the last
section ".kprobes.text" is particular, which has been marked as "notrace",
we ignore it. Thus we add other two sections.
Signed-off-by: NLiming Wang <liming.wang@windriver.com>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

fix return-tracer => graph-tracer namespace rename fallout.
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: feature

This patch sets a C-like output for the function graph tracing.
For this aim, we now call two handler for each function: one on the entry
and one other on return. This way we can draw a well-ordered call stack.

The pid of the previous trace is loosely stored to be compared against
the one of the current trace to see if there were a context switch.

Without this little feature, the call tree would seem broken at
some locations.
We could use the sched_tracer to capture these sched_events but this
way of processing is much more simpler.

2 spaces have been chosen for indentation to fit the screen while deep
calls. The time of execution in nanosecs is printed just after closed
braces, it seems more easy this way to find the corresponding function.
If the time was printed as a first column, it would be not so easy to
find the corresponding function if it is called on a deep depth.

I plan to output the return value but on 32 bits CPU, the return value
can be 32 or 64, and its difficult to guess on which case we are.
I don't know what would be the better solution on X86-32: only print
eax (low-part) or even edx (high-part).

Actually it's thee same problem when a function return a 8 bits value, the
high part of eax could contain junk values...

Here is an example of trace:

sys_read() {
  fget_light() {
  } 526
  vfs_read() {
    rw_verify_area() {
      security_file_permission() {
        cap_file_permission() {
        } 519
      } 1564
    } 2640
    do_sync_read() {
      pipe_read() {
        __might_sleep() {
        } 511
        pipe_wait() {
          prepare_to_wait() {
          } 760
          deactivate_task() {
            dequeue_task() {
              dequeue_task_fair() {
                dequeue_entity() {
                  update_curr() {
                    update_min_vruntime() {
                    } 504
                  } 1587
                  clear_buddies() {
                  } 512
                  add_cfs_task_weight() {
                  } 519
                  update_min_vruntime() {
                  } 511
                } 5602
                dequeue_entity() {
                  update_curr() {
                    update_min_vruntime() {
                    } 496
                  } 1631
                  clear_buddies() {
                  } 496
                  update_min_vruntime() {
                  } 527
                } 4580
                hrtick_update() {
                  hrtick_start_fair() {
                  } 488
                } 1489
              } 13700
            } 14949
          } 16016
          msecs_to_jiffies() {
          } 496
          put_prev_task_fair() {
          } 504
          pick_next_task_fair() {
          } 489
          pick_next_task_rt() {
          } 496
          pick_next_task_fair() {
          } 489
          pick_next_task_idle() {
          } 489

------------8<---------- thread 4 ------------8<----------

finish_task_switch() {
} 1203
do_softirq() {
  __do_softirq() {
    __local_bh_disable() {
    } 669
    rcu_process_callbacks() {
      __rcu_process_callbacks() {
        cpu_quiet() {
          rcu_start_batch() {
          } 503
        } 1647
      } 3128
      __rcu_process_callbacks() {
      } 542
    } 5362
    _local_bh_enable() {
    } 587
  } 8880
} 9986
kthread_should_stop() {
} 669
deactivate_task() {
  dequeue_task() {
    dequeue_task_fair() {
      dequeue_entity() {
        update_curr() {
          calc_delta_mine() {
          } 511
          update_min_vruntime() {
          } 511
        } 2813
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: cleanup

This patch changes the name of the "return function tracer" into
function-graph-tracer which is a more suitable name for a tracing
which makes one able to retrieve the ordered call stack during
the code flow.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: add new ftrace plugin

A prototype for a BTS ftrace plug-in.

The tracer collects branch trace in a cyclic buffer for each cpu.

The tracer is not configurable and the trace for each snapshot is
appended when doing cat /debug/tracing/trace.

This is a proof of concept that will be extended with future patches
to become a (hopefully) useful tool.
Signed-off-by: NMarkus Metzger <markus.t.metzger@intel.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Add a callback to allow an ftrace plug-in to write its own header.

Move the call to trace->open() up a few lines.

The changes are required by the BTS ftrace plug-in.
Signed-off-by: NMarkus Metzger <markus.t.metzger@intel.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: restructure DS memory allocation to be done by the usage site of DS

Require pre-allocated buffers in ds.h.

Move the BTS buffer allocation for ptrace into ptrace.c.
The pointer to the allocated buffer is stored in the traced task's
task_struct together with the handle returned by ds_request_bts().

Removes memory accounting code.
Signed-off-by: NMarkus Metzger <markus.t.metzger@intel.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: generalize the DS code to shared buffers

Change the in-kernel ds.h interface to identify the tracer via a
handle returned on ds_request_~().

Tracers used to be identified via their task_struct.

The changes are required to allow DS to be shared between different
tasks, which is needed for perfmon2 and for ftrace.

For ptrace, the handle is stored in the traced task's task_struct.
This should probably go into a (arch-specific) ptrace context some
time.
Signed-off-by: NMarkus Metzger <markus.t.metzger@intel.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

This pulls together all the topic branches that are needed
for the DS/BTS/PEBS tracing work.