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SubjectRe: [PATCH 2/2] vmlinux.lds.h: add HEADERED_SECTION_* macros
Date
From: Jim Cromie <jim.cromie@gmail.com>
Date: Wed, 16 Nov 2022 17:20:22 -0700

> These macros elaborate on BOUNDED_SECTION_(PRE|POST)_LABEL macros,
> prepending an optional KEEP(.gnu.linkonce##_sec_) reservation, and a
> linker-symbol to address it.
>
> This allows a developer to define a header struct (which must fit with
> the section's base struct-type), and could contain:

[...]

> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> index 85d5d5b203dc..a3b6aa30a525 100644
> --- a/include/asm-generic/vmlinux.lds.h
> +++ b/include/asm-generic/vmlinux.lds.h
> @@ -214,6 +214,21 @@
>
> #define BOUNDED_SECTION(_sec) BOUNDED_SECTION_BY(_sec, _sec)
>
> +#define HEADERED_SECTION_PRE_LABEL(_sec_, _label_, _BEGIN_, _END_, _HDR_) \
> + _HDR_##_label_ = .; \
> + KEEP(*(.gnu.linkonce.##_sec_)) \
> + BOUNDED_SECTION_PRE_LABEL(_sec_, _label_, _BEGIN_, _END_)
> +
> +#define HEADERED_SECTION_POST_LABEL(_sec_, _label_, _BEGIN_, _END_, _HDR_) \
> + _label_##_HDR_ = .; \
> + KEEP(*(.gnu.linkonce.##_sec_)) \
> + BOUNDED_SECTION_POST_LABEL(_sec_, _label_, _BEGIN_, _END_)
> +
> +#define HEADERED_SECTION_BY(_sec_, _label_) \
> + HEADERED_SECTION_PRE_LABEL(_sec_, _label_, __start, __stop)

Now HEADERED_SECTION_PRE_LABEL() takes 5 arguments, but this line
passes only 4 to it. This went unnoticed probably due to that the
macro is not used anywhere, thus can't trigger a compiler error.
Would you prefer to fix it yourself or me to send the fix?[*]

> +
> +#define HEADERED_SECTION(_sec) HEADERED_SECTION_BY(_sec, _sec)
> +
> #ifdef CONFIG_TRACE_BRANCH_PROFILING
> #define LIKELY_PROFILE() \
> BOUNDED_SECTION_BY(_ftrace_annotated_branch, _annotated_branch_profile)
> --
> 2.38.1

[*] If it needs fixing at all -- some people over the MLs say that
if there's no trigger, then there's nothing to fix :clownface:

Thanks,
Olek

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