linux-kernel - Re: [PATCH] codetag: Avoid unused alloc

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Message-ID: <CAJuCfpEpFqLX-WtXzSdktkp7w3s3JWeSqeG_fms6Ydun+docTA@mail.gmail.com>
Date: Thu, 13 Mar 2025 11:07:53 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: Kent Overstreet <kent.overstreet@...ux.dev>
Cc: Petr Pavlu <petr.pavlu@...e.com>, Arnd Bergmann <arnd@...db.de>, linux-arch@...r.kernel.org, 
	linux-modules@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] codetag: Avoid unused alloc_tags sections/symbols

On Thu, Mar 13, 2025 at 10:16 AM Kent Overstreet
<kent.overstreet@...ux.dev> wrote:
>
> On Thu, Mar 13, 2025 at 03:29:20PM +0100, Petr Pavlu wrote:
> > With CONFIG_MEM_ALLOC_PROFILING=n, vmlinux and all modules unnecessarily
> > contain the symbols __start_alloc_tags and __stop_alloc_tags, which define
> > an empty range. In the case of modules, the presence of these symbols also
> > forces the linker to create an empty .codetag.alloc_tags section.
> >
> > Update codetag.lds.h to make the data conditional on
> > CONFIG_MEM_ALLOC_PROFILING.
> >
> > Signed-off-by: Petr Pavlu <petr.pavlu@...e.com>
>
> Reviewed-by: Kent Overstreet <kent.overstreet@...ux.dev>

Reviewed-by: Suren Baghdasaryan <surenb@...gle.com>

>
> > ---
> >  include/asm-generic/codetag.lds.h | 10 ++++++++--
> >  1 file changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/asm-generic/codetag.lds.h b/include/asm-generic/codetag.lds.h
> > index 372c320c5043..0ea1fa678405 100644
> > --- a/include/asm-generic/codetag.lds.h
> > +++ b/include/asm-generic/codetag.lds.h
> > @@ -2,6 +2,12 @@
> >  #ifndef __ASM_GENERIC_CODETAG_LDS_H
> >  #define __ASM_GENERIC_CODETAG_LDS_H
> >
> > +#ifdef CONFIG_MEM_ALLOC_PROFILING
> > +#define IF_MEM_ALLOC_PROFILING(...) __VA_ARGS__
> > +#else
> > +#define IF_MEM_ALLOC_PROFILING(...)
> > +#endif
> > +
> >  #define SECTION_WITH_BOUNDARIES(_name)       \
> >       . = ALIGN(8);                   \
> >       __start_##_name = .;            \
> > @@ -9,7 +15,7 @@
> >       __stop_##_name = .;
> >
> >  #define CODETAG_SECTIONS()           \
> > -     SECTION_WITH_BOUNDARIES(alloc_tags)
> > +     IF_MEM_ALLOC_PROFILING(SECTION_WITH_BOUNDARIES(alloc_tags))
> >
> >  /*
> >   * Module codetags which aren't used after module unload, therefore have the
> > @@ -28,6 +34,6 @@
> >   * unload them individually once unused.
> >   */
> >  #define MOD_SEPARATE_CODETAG_SECTIONS()              \
> > -     MOD_SEPARATE_CODETAG_SECTION(alloc_tags)
> > +     IF_MEM_ALLOC_PROFILING(MOD_SEPARATE_CODETAG_SECTION(alloc_tags))
> >
> >  #endif /* __ASM_GENERIC_CODETAG_LDS_H */
> >
> > base-commit: 80e54e84911a923c40d7bee33a34c1b4be148d7a
> > --
> > 2.43.0
> >