Received-SPF: pass (google.com: domain of linux-kernel+bounces-77643-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) client-ip=2604:1380:45d1:ec00::1;
Message-ID: <7396cdc0-e878-48fe-85b9-d88611d28444@huawei.com>
Date: Fri, 23 Feb 2024 09:39:29 +0800
Precedence: bulk
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH -next] arm32: enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION
Content-Language: en-US
To: Arnd Bergmann <arnd@arndb.de>, <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>
References: <20240220081527.23408-1-liuyuntao12@huawei.com>
 <1342759e-b967-4ec4-98d5-48146f81f695@app.fastmail.com>
 <38c09a4b-69cc-4dc5-8a68-e5f5597613ac@huawei.com>
 <30b01c65-12f2-4ee0-81d5-c7a2da2c36b4@app.fastmail.com>
 <4e9396ca-460b-49ca-818e-73f0a8997b15@huawei.com>
 <58297ee9-4f33-4b3b-bd00-b44e86965892@app.fastmail.com>
From: "liuyuntao (F)" <liuyuntao12@huawei.com>
In-Reply-To: <58297ee9-4f33-4b3b-bd00-b44e86965892@app.fastmail.com>
Content-Type: text/plain; charset="UTF-8"; format=flowed
Content-Transfer-Encoding: 7bit


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.