[v1] codetag: Avoid unused alloc_tags sections/symbols

[PATCH] codetag: Avoid unused alloc_tags sections/symbols

Posted by Petr Pavlu 9 months, 1 week ago

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@suse.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

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

Posted by Kent Overstreet 9 months, 1 week ago

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@suse.com>

Reviewed-by: Kent Overstreet <kent.overstreet@linux.dev>

> ---
>  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
>

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

Posted by Suren Baghdasaryan 9 months, 1 week ago

On Thu, Mar 13, 2025 at 10:16 AM Kent Overstreet
<kent.overstreet@linux.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@suse.com>
>
> Reviewed-by: Kent Overstreet <kent.overstreet@linux.dev>

Reviewed-by: Suren Baghdasaryan <surenb@google.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
> >