linux-kernel - Re: [PATCH v4] ARM: module: Add all unwind tables when load module

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Date:   Fri, 29 Apr 2022 00:45:24 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Chen Zhongjin <chenzhongjin@...wei.com>
Cc:     linux@...linux.org.uk, alexander.sverdlin@...ia.com,
        ardb@...nel.org, nico@...xnic.net,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] ARM: module: Add all unwind tables when load module

On Fri, Apr 1, 2022 at 3:16 PM Chen Zhongjin <chenzhongjin@...wei.com> wrote:

> For EABI stack unwinding, when loading .ko module
> the EXIDX sections will be added to a unwind_table list.
>
> However not all EXIDX sections are added because EXIDX
> sections are searched by hardcoded section names.
>
> For functions in other sections such as .ref.text
> or .kprobes.text, gcc generates seprated EXIDX sections
> (such as .ARM.exidx.ref.text or .ARM.exidx.kprobes.text).
>
> These extra EXIDX sections are not loaded, so when unwinding
> functions in these sections, we will failed with:
>
>         unwind: Index not found xxx
>
> To fix that, I refactor the code for searching and adding
> EXIDX sections:
>
> - Check section type to search EXIDX tables (0x70000001)
> instead of strcmp() the hardcoded names. Then find the
> corresponding text sections by their section names.
>
> - Add a unwind_table list in module->arch to save their own
> unwind_table instead of the fixed-lenth array.
>
> - Save .ARM.exidx.init.text section ptr, because it should
> be cleaned after module init.
>
> Now all EXIDX sections of .ko can be added correctly.
>
> Signed-off-by: Chen Zhongjin <chenzhongjin@...wei.com>

This looks reasonable to me:
Acked-by: Linus Walleij <linus.walleij@...aro.org>

If no one else comments I would say you should put this
into Russell's patch tracker for consideration.

Yours,
Linus Walleij