linux-stable.git/include/linux/ftrace.h, branch v3.4.97

ftrace/module: Hardcode ftrace_module_init() call into load_module()

2014-06-07T23:02:00+00:00

commit a949ae560a511fe4e3adf48fa44fefded93e5c2b upstream.

A race exists between module loading and enabling of function tracer.

	CPU 1				CPU 2
	-----				-----
  load_module()
   module->state = MODULE_STATE_COMING

				register_ftrace_function()
				 mutex_lock(&ftrace_lock);
				 ftrace_startup()
				  update_ftrace_function();
				   ftrace_arch_code_modify_prepare()
				    set_all_module_text_rw();
				   
				    ftrace_arch_code_modify_post_process()
				     set_all_module_text_ro();

				[ here all module text is set to RO,
				  including the module that is
				  loading!! ]

   blocking_notifier_call_chain(MODULE_STATE_COMING);
    ftrace_init_module()

     [ tries to modify code, but it's RO, and fails!
       ftrace_bug() is called]

When this race happens, ftrace_bug() will produces a nasty warning and
all of the function tracing features will be disabled until reboot.

The simple solution is to treate module load the same way the core
kernel is treated at boot. To hardcode the ftrace function modification
of converting calls to mcount into nops. This is done in init/main.c
there's no reason it could not be done in load_module(). This gives
a better control of the changes and doesn't tie the state of the
module to its notifiers as much. Ftrace is special, it needs to be
treated as such.

The reason this would work, is that the ftrace_module_init() would be
called while the module is in MODULE_STATE_UNFORMED, which is ignored
by the set_all_module_text_ro() call.

Link: http://lkml.kernel.org/r/1395637826-3312-1-git-send-email-indou.takao@jp.fujitsu.com

Reported-by: Takao Indoh 
Acked-by: Rusty Russell 
Signed-off-by: Steven Rostedt 
Signed-off-by: Greg Kroah-Hartman

ftrace: Move ftrace_filter_lseek out of CONFIG_DYNAMIC_FTRACE section

2013-06-13T16:45:03+00:00

commit 7f49ef69db6bbf756c0abca7e9b65b32e999eec8 upstream.

As ftrace_filter_lseek is now used with ftrace_pid_fops, it needs to
be moved out of the #ifdef CONFIG_DYNAMIC_FTRACE section as the
ftrace_pid_fops is defined when DYNAMIC_FTRACE is not.

Signed-off-by: Steven Rostedt 
Cc: Namhyung Kim 
[ lizf: adjust context ]
Signed-off-by: Li Zefan 
Signed-off-by: Greg Kroah-Hartman

tracing: Fix possible NULL pointer dereferences

2013-06-13T16:45:03+00:00

commit 6a76f8c0ab19f215af2a3442870eeb5f0e81998d upstream.

Currently set_ftrace_pid and set_graph_function files use seq_lseek
for their fops.  However seq_open() is called only for FMODE_READ in
the fops->open() so that if an user tries to seek one of those file
when she open it for writing, it sees NULL seq_file and then panic.

It can be easily reproduced with following command:

  $ cd /sys/kernel/debug/tracing
  $ echo 1234 | sudo tee -a set_ftrace_pid

In this example, GNU coreutils' tee opens the file with fopen(, "a")
and then the fopen() internally calls lseek().

Link:
http://lkml.kernel.org/r/1365663302-2170-1-git-send-email-namhyung@kernel.org

Signed-off-by: Namhyung Kim 
Cc: Frederic Weisbecker 
Cc: Ingo Molnar 
Cc: Namhyung Kim 
Signed-off-by: Steven Rostedt 
[ lizf: adjust context ]
Signed-off-by: Li Zefan 
Signed-off-by: Greg Kroah-Hartman

ftrace, perf: Add filter support for function trace event

2012-02-21T16:08:30+00:00

Adding support to filter function trace event via perf
interface. It is now possible to use filter interface
in the perf tool like:

  perf record -e ftrace:function --filter="(ip == mm_*)" ls

The filter syntax is restricted to the the 'ip' field only,
and following operators are accepted '==' '!=' '||', ending
up with the filter strings like:

  ip == f1[, ]f2 ... || ip != f3[, ]f4 ...

with comma ',' or space ' ' as a function separator. If the
space ' ' is used as a separator, the right side of the
assignment needs to be enclosed in double quotes '"', e.g.:

  perf record -e ftrace:function --filter '(ip == do_execve,sys_*,ext*)' ls
  perf record -e ftrace:function --filter '(ip == "do_execve,sys_*,ext*")' ls
  perf record -e ftrace:function --filter '(ip == "do_execve sys_* ext*")' ls

The '==' operator adds trace filter with same effect as would
be added via set_ftrace_filter file.

The '!=' operator adds trace filter with same effect as would
be added via set_ftrace_notrace file.

The right side of the '!=', '==' operators is list of functions
or regexp. to be added to filter separated by space.

The '||' operator is used for connecting multiple filter definitions
together. It is possible to have more than one '==' and '!='
operators within one filter string.

Link: http://lkml.kernel.org/r/1329317514-8131-8-git-send-email-jolsa@redhat.com

Signed-off-by: Jiri Olsa 
Signed-off-by: Steven Rostedt

ftrace: Add enable/disable ftrace_ops control interface

2012-02-21T16:08:23+00:00

Adding a way to temporarily enable/disable ftrace_ops. The change
follows the same way as 'global' ftrace_ops are done.

Introducing 2 global ftrace_ops - control_ops and ftrace_control_list
which take over all ftrace_ops registered with FTRACE_OPS_FL_CONTROL
flag. In addition new per cpu flag called 'disabled' is also added to
ftrace_ops to provide the control information for each cpu.

When ftrace_ops with FTRACE_OPS_FL_CONTROL is registered, it is
set as disabled for all cpus.

The ftrace_control_list contains all the registered 'control' ftrace_ops.
The control_ops provides function which iterates ftrace_control_list
and does the check for 'disabled' flag on current cpu.

Adding 3 inline functions:
  ftrace_function_local_disable/ftrace_function_local_enable
  - enable/disable the ftrace_ops on current cpu
  ftrace_function_local_disabled
  - get disabled ftrace_ops::disabled value for current cpu

Link: http://lkml.kernel.org/r/1329317514-8131-2-git-send-email-jolsa@redhat.com

Acked-by: Frederic Weisbecker 
Signed-off-by: Jiri Olsa 
Signed-off-by: Steven Rostedt

ftrace: Change filter/notrace set functions to return exit code

2012-02-03T14:48:18+00:00

Currently the ftrace_set_filter and ftrace_set_notrace functions
do not return any return code. So there's no way for ftrace_ops
user to tell wether the filter was correctly applied.

The set_ftrace_filter interface returns error in case the filter
did not match:

  # echo krava > set_ftrace_filter
  bash: echo: write error: Invalid argument

Changing both ftrace_set_filter and ftrace_set_notrace functions
to return zero if the filter was applied correctly or -E* values
in case of error.

Link: http://lkml.kernel.org/r/1325495060-6402-2-git-send-email-jolsa@redhat.com

Acked-by: Frederic Weisbecker 
Signed-off-by: Jiri Olsa 
Signed-off-by: Steven Rostedt

tracing: Fix compile error when static ftrace is enabled

2012-01-07T22:26:49+00:00

The stack tracer uses the call ftrace_set_early_filter() function
to allow the stack tracer to pick its own functions on boot.
But this function is not defined if dynamic ftrace is not set.
This causes a compiler error when stack tracer is enabled and
dynamic ftrace is not.

Reported-by: Ingo Molnar 
Signed-off-by: Steven Rostedt

ftrace: Allow access to the boot time function enabling

2011-12-21T12:26:35+00:00

Change set_ftrace_early_filter() to ftrace_set_early_filter()
and make it a global function. This will allow other subsystems
in the kernel to be able to enable function tracing at start
up and reuse the ftrace function parsing code.

Signed-off-by: Steven Rostedt

ftrace: Decouple hash items from showing filtered functions

2011-12-21T12:25:24+00:00

The set_ftrace_filter shows "hashed" functions, which are functions
that are added with operations to them (like traceon and traceoff).

As other subsystems may be able to show what functions they are
using for function tracing, the hash items should no longer
be shown just because the FILTER flag is set. As they have nothing
to do with other subsystems filters.

Signed-off-by: Steven Rostedt

ftrace: Allow other users of function tracing to use the output listing

2011-12-21T12:25:06+00:00

The function tracer is set up to allow any other subsystem (like perf)
to use it. Ftrace already has a way to list what functions are enabled
by the global_ops. It would be very helpful to let other users of
the function tracer to be able to use the same code.

Signed-off-by: Steven Rostedt