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

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Message-ID: <70772ce5-9dca-418e-9714-80ba4ae28959@gmail.com>
Date: Tue, 12 Nov 2024 08:45:01 +0100
From: Klara Modin <klarasmodin@...il.com>
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>,
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Subject: Re: [PATCH v6 3/7] Adjust symbol ordering in text output section

On 2024-11-12 06:38, Rong Xu wrote:
> I compared the System.map files from Klara Modin. The linker script is
> doing what I expected: relocating the unlikely executed functions to the
> beginning of the .text section.
> 
> However, the problem is with the _stext symbol. It belongs to the
> .text section, so
> it is positioned after the unlikely (or hot) functions. But it really
> needs to be
> the start of the text section.
> 
> I checked all vmlinux.lds.S in arch/, I found that most archs
> explicitly assign _stext to the same address as _text, with the
> following 3 exceptions:
>    arch/sh/kernel/vmlinux.lds.S
>    arch/mips/kernel/vmlinux.lds.S
>    arch/sparc/kernel/vmlinux.lds.S
> 
> Note that we already partially handled arch/sparc/kernel/vmlinux.lds.S
> for sparc64.
> But we need to handle sparc32 also.
> 
> Additionally, the boot/compressed/vmlinux.lds.S also the TEXT_TEXT
> template. However,
> I presume these files do not generate the .text.unlikely. or
> .text.hot.* sections.
> 
> I sent the following patch to Klara because I don't have an
> environment to build and test.
> ====================
> diff --git a/arch/mips/kernel/vmlinux.lds.S b/arch/mips/kernel/vmlinux.lds.S
> index 9ff55cb80a64..5f130af44247 100644
> --- a/arch/mips/kernel/vmlinux.lds.S
> +++ b/arch/mips/kernel/vmlinux.lds.S
> @@ -61,6 +61,7 @@ SECTIONS
>          /* read-only */
>          _text = .;      /* Text and read-only data */
>          .text : {
> +               _stext = .;
>                  TEXT_TEXT
>                  SCHED_TEXT
>                  LOCK_TEXT
> ======================
> 
> If Klara confirms the fix, I will send the patch for review.
> 
> Thanks,
> 
> -Rong
> 

This does indeed fix the issue for me.

Thanks,
Tested-by: Klara Modin <klarasmodin@...il.com>