linux-toradex.git/scripts/recordmcount.h, branch v3.15-rc6

ftrace: Make recordmcount.c handle fentry

2012-08-23T15:24:43+00:00

With gcc 4.6.0 the -mfentry feature places the function profiling
call at the start of the function. When this is used, the call is
to __fentry__ and not mcount.

Change recordmcount.c to record both callers to __fentry__ and
mcount.

Link: http://lkml.kernel.org/r/20120807194058.990674363@goodmis.org

Acked-by: H. Peter Anvin 
Acked-by: John Reiser 
Acked-by: Ingo Molnar 
Cc: Andi Kleen 
Signed-off-by: Steven Rostedt

recordmcount: Fix handling of elf64 big-endian objects.

2012-01-06T22:06:42+00:00

In ELF64, the sh_flags field is 64-bits wide.  recordmcount was
erroneously treating it as a 32-bit wide field.  For little endian
objects this works because the flags of interest (SHF_EXECINSTR)
reside in the lower 32 bits of the word, and you get the same result
with either a 32-bit or 64-bit read.  Big endian objects on the
other hand do not work at all with this error.

The fix:  Correctly treat sh_flags as 64-bits wide in elf64 objects.

The symptom I observed was that my
__start_mcount_loc..__stop_mcount_loc was empty even though ftrace
function tracing was enabled.

Link: http://lkml.kernel.org/r/1324345362-12230-1-git-send-email-ddaney.cavm@gmail.com

Cc: stable@kernel.org # 3.0+
Signed-off-by: David Daney 
Signed-off-by: Steven Rostedt

ftrace/recordmcount: Avoid STT_FUNC symbols as base on ARM

2011-05-25T23:56:33+00:00

While find_secsym_ndx often finds the unamed local STT_SECTION, if a
section has only one function in it, the ARM toolchain generates the
STT_FUNC symbol before the STT_SECTION, and recordmcount finds this
instead.

This is problematic on ARM because in ARM ELFs, "if a [STT_FUNC] symbol
addresses a Thumb instruction, its value is the address of the
instruction with bit zero set (in a relocatable object, the section
offset with bit zero set)".  This leads to incorrect mcount addresses
being recorded.

Fix this by not using STT_FUNC symbols as the base on ARM.

Signed-off-by: Rabin Vincent 
Link: http://lkml.kernel.org/r/1305134631-31617-1-git-send-email-rabin@rab.in
Signed-off-by: Steven Rostedt

ftrace/recordmcount: mcount address adjustment

2011-05-16T18:53:22+00:00

Introduce mcount_adjust{,_32,_64} to the C implementation of
recordmcount analog to $mcount_adjust in the perl script.
The adjustment is added to the address of the relocations
against the mcount symbol. If this adjustment is done by
recordmcount at compile time the ftrace_call_adjust function
can be turned into a nop.

Cc: John Reiser 
Signed-off-by: Martin Schwidefsky 
Signed-off-by: Steven Rostedt

ftrace/recordmcount: Add helper function get_sym_str_and_relp()

2011-05-16T18:48:55+00:00

The code to get the symbol, string, and relp pointers in the two functions
sift_rel_mcount() and nop_mcount() are identical and also non-trivial.
Moving this duplicate code into a single helper function makes the code
easier to read and more maintainable.

Cc: John Reiser 
Link: http://lkml.kernel.org/r/20110421023739.723658553@goodmis.org
Signed-off-by: Steven Rostedt

ftrace/recordmcount: Remove duplicate code to find mcount symbol

2011-05-16T18:48:02+00:00

The code in sift_rel_mcount() and nop_mcount() to get the mcount symbol
number is identical. Replace the two locations with a call to a function
that does the work.

Cc: John Reiser 
Link: http://lkml.kernel.org/r/20110421023739.488093407@goodmis.org
Signed-off-by: Steven Rostedt

ftrace/recordmcount: Add warning logic to warn on mcount not recorded

2011-05-16T18:44:20+00:00

There's some sections that should not have mcount recorded and should not have
modifications to the that code. But currently they waste some time by calling
mcount anyway (which simply returns). As the real answer should be to
either whitelist the section or have gcc ignore it fully.

This change adds a option to recordmcount to warn when it finds a section
that is ignored by ftrace but still contains mcount callers. This is not on
by default as developers may not know if the section should be completely
ignored or added to the whitelist.

Cc: John Reiser 
Link: http://lkml.kernel.org/r/20110421023738.476989377@goodmis.org
Signed-off-by: Steven Rostedt

ftrace/recordmcount: Make ignored mcount calls into nops at compile time

2011-05-16T18:43:32+00:00

There are sections that are ignored by ftrace for the function tracing because
the text is in a section that can be removed without notice. The mcount calls
in these sections are ignored and ftrace never sees them. The downside of this
is that the functions in these sections still call mcount. Although the mcount
function is defined in assembly simply as a return, this added overhead is
unnecessary.

The solution is to convert these callers into nops at compile time.
A better solution is to add 'notrace' to the section markers, but as new sections
come up all the time, it would be nice that they are delt with when they
are created.

Later patches will deal with finding these sections and doing the proper solution.

Thanks to H. Peter Anvin for giving me the right nops to use for x86.

Cc: "H. Peter Anvin" 
Cc: John Reiser 
Link: http://lkml.kernel.org/r/20110421023738.237101176@goodmis.org
Signed-off-by: Steven Rostedt

ftrace/recordmcount: Modify only executable sections

2011-05-16T18:42:56+00:00

PROGBITS is not enough to determine if the section should be modified
or not. Only process sections that are marked as executable.

Cc: John Reiser 
Link: http://lkml.kernel.org/r/20110421023737.991485123@goodmis.org
Signed-off-by: Steven Rostedt

ftrace/trivial: Clean up recordmcount.c to use Linux style comparisons

2011-05-16T18:38:51+00:00

The Linux ftrace subsystem style for comparing is:

  var == 1
  var > 0

and not:

  1 == var
  0 < var

It is considered that Linux developers are smart enough not to do the

  if (var = 1)

mistake.

Cc: John Reiser 
Link: http://lkml.kernel.org/r/20110421023737.290712238@goodmis.org
Signed-off-by: Steven Rostedt