Re: [PATCH -next] arm32: enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION

From: "Arnd Bergmann" <arnd@arndb.de>
To: "Yuntao Liu" <liuyuntao12@huawei.com>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Cc: "Russell King" <linux@armlinux.org.uk>,
	"Andrew Davis" <afd@ti.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	"Geert Uytterhoeven" <geert+renesas@glider.be>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"Mike Rapoport" <rppt@kernel.org>,
	"Eric DeVolder" <eric.devolder@oracle.com>,
	"Rob Herring" <robh@kernel.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Linus Walleij" <linus.walleij@linaro.org>
Subject: Re: [PATCH -next] arm32: enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION
Date: Fri, 23 Feb 2024 07:32:32 +0100	[thread overview]
Message-ID: <e7f5c111-6c8b-47e6-a6af-05abdb9c6595@app.fastmail.com> (raw)
In-Reply-To: <7396cdc0-e878-48fe-85b9-d88611d28444@huawei.com>

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