linux-kernel - Re: [RFC][PATCH 00/13] Cleanup recordmcount and begin objtool conversion

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Date:   Tue, 28 May 2019 09:43:28 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Matt Helsley <mhelsley@...are.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [RFC][PATCH 00/13] Cleanup recordmcount and begin objtool
 conversion

On Wed, May 22, 2019 at 05:03:23PM -0700, Matt Helsley wrote:
> This series cleans up recordmcount and then makes it into
> an objtool subcommand.
> 
> The series starts with 8 cleanup patches which make recordmcount
> easier to review and integrate with objtool. The final 5 patches
> show the beginning steps of converting recordmcount to use objtool's
> ELF code rather than its own open-coded methods of accessing ELF
> files.

Hi Matt,

Thanks for the patches.  This looks like a good step in the right
direction.

What's the performance difference between the old recordmcount and the
new version which relies on elf_open()?  It would be useful to compare
kernel build times, before and after.

Would it be feasible to eventually combine subcommands so that objtool
could do both ORC and mcount generation in a single invocation?  I
wonder what what the interface would look like.

> Matt Helsley (13):
>   recordmcount: Remove redundant strcmp
>   recordmcount: Remove uread()
>   recordmcount: Remove unused fd from uwrite() and ulseek()
>   recordmcount: Rewrite error/success handling
>   recordmcount: Kernel style function signature formatting
>   recordmcount: Kernel style formatting
>   recordmcount: Remove redundant cleanup() calls
>   recordmcount: Clarify what cleanup() does
>   objtool: Prepare to merge recordmcount
>   objtool: Make recordmcount into an objtool subcmd
>   objtool: recordmcount: Start using objtool's elf wrapper
>   objtool: recordmcount: Search for __mcount_loc before walking the
>     sections
>   objtool: recordmcount: Convert do_func() relhdrs
> 
>  scripts/.gitignore                         |   1 -
>  scripts/Makefile                           |   1 -
>  scripts/Makefile.build                     |  22 +-
>  tools/objtool/.gitignore                   |   1 +
>  tools/objtool/Build                        |   1 +
>  tools/objtool/Makefile                     |   7 +-
>  tools/objtool/builtin-mcount.c             |  72 +++++
>  tools/objtool/builtin-mcount.h             |  23 ++
>  tools/objtool/builtin.h                    |   6 +
>  tools/objtool/objtool.c                    |   6 +
>  {scripts => tools/objtool}/recordmcount.c  | 350 ++++++++++-----------
>  {scripts => tools/objtool}/recordmcount.h  | 197 +++++++-----
>  {scripts => tools/objtool}/recordmcount.pl |   0
>  13 files changed, 420 insertions(+), 267 deletions(-)
>  create mode 100644 tools/objtool/builtin-mcount.c
>  create mode 100644 tools/objtool/builtin-mcount.h
>  rename {scripts => tools/objtool}/recordmcount.c (78%)
>  rename {scripts => tools/objtool}/recordmcount.h (78%)
>  rename {scripts => tools/objtool}/recordmcount.pl (100%)
> 
> -- 
> 2.20.1
> 

-- 
Josh