linux-kernel - Re: [PATCH -next] arm32: enable HAVE_LD_DEAD_CODE_DATA

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Date: Fri, 23 Feb 2024 09:39:29 +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>, Eric DeVolder <eric.devolder@...cle.com>, 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 2024/2/23 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.
> 
> I experimented with lld myself now and I did get a booting
> kernel even without the the KEEP() on the vectors. I also

When the kernel booted up successfully, was config DCE enabled?

> see that this is the only use of OVERLAY in the kernel, so
> I hope that we can find a way to make it work with existing
> lld after all, either without the KEEP or without the OVERLAY.

Yeah, i will try other way to make it work.

> 
> Did you see any problems without the KEEP() on the vectors?
> 
>       Arnd

Without the KEEP(),disable DCE, qemu boots well,
enable DCE,qemu hangs on startup.
I experimented with lld using vexpress_defconfig.