linux-kernel - Re: [PATCH v6 3/7] Adjust symbol ordering in text output section

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Message-ID: <CAK7LNAR6Ni5FZJBK_FZXWZpMZG2ppvZFCtwjx9Z=o8L1e-CyjA@mail.gmail.com>
Date: Sat, 2 Nov 2024 03:05:46 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: Rong Xu <xur@...gle.com>
Cc: Alice Ryhl <aliceryhl@...gle.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	Arnd Bergmann <arnd@...db.de>, Bill Wendling <morbo@...gle.com>, Borislav Petkov <bp@...en8.de>, 
	Breno Leitao <leitao@...ian.org>, Brian Gerst <brgerst@...il.com>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, David Li <davidxl@...gle.com>, 
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	Justin Stitt <justinstitt@...gle.com>, Kees Cook <kees@...nel.org>, 
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	sparclinux@...r.kernel.org, linux-doc@...r.kernel.org, 
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	llvm@...ts.linux.dev
Subject: Re: [PATCH v6 3/7] Adjust symbol ordering in text output section

On Sat, Oct 26, 2024 at 7:14 AM Rong Xu <xur@...gle.com> wrote:
>
> When the -ffunction-sections compiler option is enabled, each function
> is placed in a separate section named .text.function_name rather than
> putting all functions in a single .text section.
>
> However, using -function-sections can cause problems with the
> linker script. The comments included in include/asm-generic/vmlinux.lds.h
> note these issues.:
>   “TEXT_MAIN here will match .text.fixup and .text.unlikely if dead
>    code elimination is enabled, so these sections should be converted
>    to use ".." first.”
>
> It is unclear whether there is a straightforward method for converting
> a suffix to "..".
>
> This patch modifies the order of subsections within the text output
> section. Specifically, it repositions sections with certain fixed patterns
> (for example .text.unlikely) before TEXT_MAIN, ensuring that they are
> grouped and matched together. It also places .text.hot section at the
> beginning of a page to help the TLB performance.


The fixed patterns are currently listed in this order:

  .text.hot, .text_unlikely, .text.unknown, .text.asan.

You reorder them to:

  .text.asan, .text.unknown, .text.unlikely, .text.hot


I believe it is better to describe your thoughts
about the reshuffling among the fixed pattern sections.

Otherwise, It is unclear to me.




--
Best Regards
Masahiro Yamada