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Message-ID: <0255a8e9-d973-497c-9011-5651e0002a9c@huawei.com>
Date: Thu, 7 Mar 2024 11:09:53 +0800
From: "liuyuntao (F)" <liuyuntao12@...wei.com>
To: Arnd Bergmann <arnd@...db.de>, <linux-arm-kernel@...ts.infradead.org>,
<linux-kernel@...r.kernel.org>
CC: Russell King <linux@...linux.org.uk>, Andrew Davis <afd@...com>, Andrew
Morton <akpm@...ux-foundation.org>, "Kirill A. Shutemov"
<kirill.shutemov@...ux.intel.com>, Geert Uytterhoeven
<geert+renesas@...der.be>, Jonathan Corbet <corbet@....net>, Mike Rapoport
<rppt@...nel.org>, Rob Herring <robh@...nel.org>, Thomas Gleixner
<tglx@...utronix.de>, Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH -next] arm32: enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION
On 2024/2/27 16:06, liuyuntao (F) wrote:
>
>
> On 2024/2/23 0:04, Arnd Bergmann wrote:
>> On Thu, Feb 22, 2024, at 12:24, liuyuntao (F) wrote:
>>>
>>> The position of the caret has been moved below the right brace
>>> of { KEEP(*(.vectors.bhb.loop8)) }, indicating that lld is treating
>>> the entire `KEEP(*(.vectors))` as a file name. This could potentially be
>>> a bug in lld. Perhaps we can temporarily
>>> enable the DCE option only when option LD_IS_LLD is disabled,
>>> like risc-v:
>>>
>>> `select HAVE_LD_DEAD_CODE_DATA_ELIMINATION if !LD_IS_LLD`.
>>
>> I would really like to see this working with lld if at all
>> possible, as it allows the combination of gc-sections with
>> lto and CONFIG_TRIM_UNUSED_KSYMS.
>
Another way to preserve .vector sections without using KEEP annotation.
It boots well. How do you feel about this approach? and, could I submit
a v2 patch?
1: Define ARM_VECTORS_TEXT to explicitly preserve .vectors section.
> --- a/arch/arm/include/asm/vmlinux.lds.h
> +++ b/arch/arm/include/asm/vmlinux.lds.h
> @@ -87,6 +87,13 @@
> *(.vfp11_veneer) \
> *(.v4_bx)
>
> +#define ARM_VECTORS_TEXT \
> + .vectors.text : { \
> + KEEP(*(.vectors)) \
> + KEEP(*(.vectors.bhb.loop8)) \
> + KEEP(*(.vectors.bhb.bpiall)) \
> + }
> +
> #define ARM_TEXT \
> IDMAP_TEXT \
> __entry_text_start = .; \
2: Ref ARM_VECTORS_TEXT if config HAVE_LD_DEAD_CODE_DATA_ELIMINATION is
enabled, and the same to arch/arm/kernel/vmlinux.lds.S
> --- a/arch/arm/kernel/vmlinux-xip.lds.S
> +++ b/arch/arm/kernel/vmlinux-xip.lds.S
> @@ -135,6 +135,10 @@ SECTIONS
> ARM_TCM
> #endif
>
> +#ifdef HAVE_LD_DEAD_CODE_DATA_ELIMINATION
> + ARM_VECTORS_TEXT
> +#endif
> +
> /*
> * End of copied data. We need a dummy section to get its
LMA.
> * Also located before final ALIGN() as trailing padding is
> not stored
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