Re: [PATCH v3] ARM: module.lds: fix unwind metadata for merged .text sections

[Petr Pavlu]

On 5/30/26 5:46 PM, Egg12138 wrote:
> From: Xiao Junzhe <egg12138@xxxxxxxxxxx>
> 
> Commit 1ba9f8979426 ("vmlinux.lds: Unify TEXT_MAIN, DATA_MAIN,
> and related macros") made scripts/module.lds.S merge module input
> .text.* sections into the output .text section.
> 
> On ARM, the paired unwind input sections keep their original names.  A
> module can therefore contain .ARM.exidx.text.unlikely with sh_link
> pointing at .text, while .text.unlikely no longer exists.
> 
> This is a valid ELF relationship, but ARM module_finalize() does not use
> sh_link when registering module unwind tables.  It derives the target
> text section from the exidx section name instead:
> 
>   .ARM.exidx.text.unlikely -> .text.unlikely
> 
> The lookup fails and the unwind table is not registered for the actual
> .text range.  This can make module stack unwinding fail with:
> 
>   unwind: Index not found
> 
> Keep the ARM module unwind output names in sync with the text sections
> that scripts/module.lds.S now produces.  Coalesce the .ARM.exidx/.ARM.extab
> section associated with .text.*, into the
> stable output names expected by the existing ARM module unwind code.
> 
> Fixes: 1ba9f8979426 ("vmlinux.lds: Unify TEXT_MAIN, DATA_MAIN, and related macros")
> Signed-off-by: Xiao Junzhe <egg12138@xxxxxxxxxxx>

Reviewed-by: Petr Pavlu <petr.pavlu@xxxxxxxx>

As mentioned previously, please don't forget to put the fix in Russell's
patch tracker [1].

[1] https://www.arm.linux.org.uk/developer/patches/

-- 
Thanks,
Petr

> ---
> Changes in v3:
>   - Apply the ARM unwind section coalescing under CONFIG_ARM_UNWIND.
>   - Remove quotes around linker-script wildcard patterns so GNU ld expands
>     them correctly.
>   - Use conventional linker-script wildcard syntax, i.e. *(...) without a
>     space after the wildcard.
> 
>  arch/arm/include/asm/module.lds.h | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/arch/arm/include/asm/module.lds.h b/arch/arm/include/asm/module.lds.h
> index 0e7cb4e314b4..1d56c0375c18 100644
> --- a/arch/arm/include/asm/module.lds.h
> +++ b/arch/arm/include/asm/module.lds.h
> @@ -1,4 +1,16 @@
>  /* SPDX-License-Identifier: GPL-2.0 */
> +
> +#ifdef CONFIG_ARM_UNWIND
> +SECTIONS {
> +	.ARM.extab		0 : {
> +		*(.ARM.extab .ARM.extab.text .ARM.extab.text.[0-9a-zA-Z_]*)
> +	}
> +	.ARM.exidx		0 : {
> +		*(.ARM.exidx .ARM.exidx.text .ARM.exidx.text.[0-9a-zA-Z_]*)
> +	}
> +}
> +#endif
> +
>  #ifdef CONFIG_ARM_MODULE_PLTS
>  SECTIONS {
>  	.plt : { BYTE(0) }