[PATCHSET 0/6] perf tools: Minimal build without libelf dependency (v3)

[Namhyung Kim]

Hi,

This is my third version of the series. I removed RFC tag in subject
line since I think most of you seem to agree with the change. :)

Patch 1 and 2 are independent to the series and can be applied solely
(and possibly merged to one).

This patchset is based on Arnaldo's perf/core branch at 81e9b994bb20
("Merge tag 'libtraceevent-core-for-acme' of
git://git.kernel.org/pub/scm/linux/kernel/git/namhyung/linux-perf into
perf/core") and tested on x86_64 and ARM.

You can also get this set on perf/minimal-v3 branch on my tree (see
above) if you want.

Any comments are welcome.
Namhyung


v3:
 * drop already merged (cross-build related) patches
 * drop SYMBIND_* change (Arnaldo)

v2:
 * change make option name to NO_LIBELF
 * make it default when libelf doesn't exist (Ingo)
 * get rid of elf-minimal.h and use elf.h (Jiri)

The original description follows.

--- 

Current build procedure of perf tools requires a couple of external
libraries. Although most of them are optional, elfutils' libelf is
mandatory for resolving symbols and build-id of the binaries being
profiled. For some reason, it makes embedded guys' life harder who
want to build and run perf tools on their boards.

This patchset tries to fix the problem by letting the perf could
be built without the libelf. The initial intent was just providing
perf record command to gather performance events interested on the
system and copies perf.data to development box to be used by (full-
fledged) perf report for analysis.

However it's changed to have most of perf commands as is because
perf can resolve kernel symbols without libelf and many of perf
commands deal (mostly) with kernel events - so no need to restrict
capability of perf tools. Therefore, the end result is not so
minimalistic actually and the only thing it cannot do is "perf probe".

And there's a poor man's version of ELF parser only for parsing the
build-id info. While it's not absolutely needed, I think it's good to
have, just in case.

In addition, I changed my mind to keep unrelated configurations -
i.g. tui/gui and perf/python support - enabled by default so that
it can be configured by a find-grained config method in the future.

To build a minimal perf tools explicitly, pass NO_LIBELF=1 to make.
Or, if the system doesn't provide the elfutils it'll detect that
and converts to the minimal build mode automatically. The resulting
perf report will not display symbol names in userland:

 # Samples: 3K of event 'cycles'
 # Event count (approx.): 3740267998
 #
 # Overhead  Command      Shared Object                          Symbol
 # ........  .......  .................  ..............................
 #
     99.70%  noploop  noploop            [.] 0x000000000000066d        
      0.10%  noploop  [kernel.kallsyms]  [k] free_pgd_range            
      0.03%  noploop  [kernel.kallsyms]  [k] native_write_msr_safe     
      0.03%  noploop  [kernel.kallsyms]  [k] raise_softirq             
      0.03%  noploop  [kernel.kallsyms]  [k] rb_insert_color       
 
But perf buildid-list can show the build-id's:

 $ ./perf buildid-list --with-hits
 5eaf1839576cc801053e63300762def90a77a305 [kernel.kallsyms]
 43a7a2b399b6ee2ff29c6bdadbda6bff88712ed4 /home/namhyung/bin/noploop

So it can be packed using perf archive command and copied and
analized with full-fledged perf tools on a development machine.


Namhyung Kim (6):
  tools lib traceevent: Detect build environment changes
  tools lib traceevent: Ignore TRACEEVENT-CFLAGS file
  perf symbols: Introduce symbol__elf_init()
  perf tools: Split out util/symbol-elf.c
  perf tools: Support minimal build without libelf
  perf symbols: Implement poor man's ELF parser

 tools/lib/traceevent/.gitignore     |    1 +
 tools/lib/traceevent/Makefile       |   14 +-
 tools/perf/Makefile                 |   58 ++-
 tools/perf/builtin-buildid-list.c   |    4 +-
 tools/perf/builtin-inject.c         |    5 +-
 tools/perf/command-list.txt         |    2 +-
 tools/perf/perf.c                   |    2 +
 tools/perf/util/generate-cmdlist.sh |   15 +
 tools/perf/util/map.c               |   22 +-
 tools/perf/util/map.h               |    1 +
 tools/perf/util/symbol-elf.c        |  775 +++++++++++++++++++++++++++++++++
 tools/perf/util/symbol-minimal.c    |  267 ++++++++++++
 tools/perf/util/symbol.c            |  802 +----------------------------------
 tools/perf/util/symbol.h            |   16 +
 14 files changed, 1169 insertions(+), 815 deletions(-)
 create mode 100644 tools/lib/traceevent/.gitignore
 create mode 100644 tools/perf/util/symbol-elf.c
 create mode 100644 tools/perf/util/symbol-minimal.c

-- 
1.7.10.4

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