Re: [PATCH] codetag: Avoid unused alloc_tags sections/symbols

From: Suren Baghdasaryan
Date: Thu Mar 13 2025 - 14:08:17 EST


On Thu, Mar 13, 2025 at 10:16 AM Kent Overstreet
<kent.overstreet@xxxxxxxxx> 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@xxxxxxxx>
>
> Reviewed-by: Kent Overstreet <kent.overstreet@xxxxxxxxx>

Reviewed-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>

>
> > ---
> > 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
> >