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

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Date: Fri, 23 Feb 2024 07:32:32 +0100
From: "Arnd Bergmann" <arnd@...db.de>
To: "Yuntao Liu" <liuyuntao12@...wei.com>,
 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 Fri, Feb 23, 2024, at 02:39, 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.
>> 
>> 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?

My mistake. I did have DCE enabled in the kernel I built,
but ended up passing an older image to it in the end,
and that did not boot.

     Arnd