linux-kernel - Re: [PATCH 1/2] codetag: Use dot prefix for section name

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Message-ID: <CAJuCfpGXBH0FQppLppSkCLeRwCJsAGUMWL6F+G1TdqU4d=q4og@mail.gmail.com>
Date: Mon, 14 Oct 2024 14:16:52 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: Ard Biesheuvel <ardb+git@...gle.com>
Cc: linux-kernel@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>, 
	Linus Torvalds <torvalds@...ux-foundation.org>, Masahiro Yamada <masahiroy@...nel.org>, 
	Nathan Chancellor <nathan@...nel.org>, Kent Overstreet <kent.overstreet@...ux.dev>, 
	Arnd Bergmann <arnd@...db.de>, linux-arch@...r.kernel.org, linux-mm@...ck.org, 
	linux-kbuild@...r.kernel.org
Subject: Re: [PATCH 1/2] codetag: Use dot prefix for section name

On Mon, Oct 14, 2024 at 5:57 AM Ard Biesheuvel <ardb+git@...gle.com> wrote:
>
> From: Ard Biesheuvel <ardb@...nel.org>
>
> Sections typically use leading dots in their names, and deviating from
> this breaks some assumptions in the existing code, e.g., in strip_relocs
> on x86, which filters out .rela.* and .rela__* sections.
>
>   [65] alloc_tags        PROGBITS         0000000000000000  03a57958
>        0000000000026340  0000000000000000  WA       0     0     8
>   [66] .relaalloc_tags   RELA             0000000000000000  08dbb868
>        0000000000044c40  0000000000000018   I      280    65     8
>
> So use a leading dot for the alloc_tags sections.

No issues with renaming the section but please note that I posted a
patch [1] today that will have conflicts with this renaming.

[1] https://lore.kernel.org/all/20241014203646.1952505-3-surenb@google.com/

>
> Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
> ---
>  include/asm-generic/codetag.lds.h | 2 +-
>  include/linux/alloc_tag.h         | 4 ++--
>  2 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/include/asm-generic/codetag.lds.h b/include/asm-generic/codetag.lds.h
> index 64f536b80380..dcd18351ba2f 100644
> --- a/include/asm-generic/codetag.lds.h
> +++ b/include/asm-generic/codetag.lds.h
> @@ -5,7 +5,7 @@
>  #define SECTION_WITH_BOUNDARIES(_name) \
>         . = ALIGN(8);                   \
>         __start_##_name = .;            \
> -       KEEP(*(_name))                  \
> +       KEEP(*(. ## _name))             \
>         __stop_##_name = .;

I think leaving the SECTION_WITH_BOUNDARIES() definition as is and
changing its users to pass the name with the dot would be more
explicit and more flexible.
The only user today is CODETAG_SECTIONS() at [2], so I would add the
dot in there instead.

[2] https://elixir.bootlin.com/linux/v6.12-rc2/source/include/asm-generic/codetag.lds.h#L12

Thanks,
Suren.

>
>  #define CODETAG_SECTIONS()             \
> diff --git a/include/linux/alloc_tag.h b/include/linux/alloc_tag.h
> index 1f0a9ff23a2c..d45a8a582970 100644
> --- a/include/linux/alloc_tag.h
> +++ b/include/linux/alloc_tag.h
> @@ -76,7 +76,7 @@ DECLARE_PER_CPU(struct alloc_tag_counters, _shared_alloc_tag);
>
>  #define DEFINE_ALLOC_TAG(_alloc_tag)                                           \
>         static struct alloc_tag _alloc_tag __used __aligned(8)                  \
> -       __section("alloc_tags") = {                                             \
> +       __section(".alloc_tags") = {                                            \
>                 .ct = CODE_TAG_INIT,                                            \
>                 .counters = &_shared_alloc_tag };
>
> @@ -85,7 +85,7 @@ DECLARE_PER_CPU(struct alloc_tag_counters, _shared_alloc_tag);
>  #define DEFINE_ALLOC_TAG(_alloc_tag)                                           \
>         static DEFINE_PER_CPU(struct alloc_tag_counters, _alloc_tag_cntr);      \
>         static struct alloc_tag _alloc_tag __used __aligned(8)                  \
> -       __section("alloc_tags") = {                                             \
> +       __section(".alloc_tags") = {                                            \
>                 .ct = CODE_TAG_INIT,                                            \
>                 .counters = &_alloc_tag_cntr };
>
> --
> 2.47.0.rc1.288.g06298d1525-goog
>