linux-kernel - Re: [build fail] v6.11-rc2 from "ARM: 9404/1: arm32: enable HAVE_LD_DEAD_CODE_DATA

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Message-ID: <44ffc9bc-f14e-4576-94fe-189c1f672444@gmail.com>
Date: Wed, 7 Aug 2024 21:18:06 +0530
From: Harith George <mail2hgg@...il.com>
To: Arnd Bergmann <arnd@...db.de>, Yuntao Liu <liuyuntao12@...wei.com>,
 Linus Walleij <linus.walleij@...aro.org>,
 Russell King <rmk+kernel@...linux.org.uk>, Ard Biesheuvel <ardb@...nel.org>,
 harith.g@...fsemi.com
Cc: linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [build fail] v6.11-rc2 from "ARM: 9404/1: arm32: enable
 HAVE_LD_DEAD_CODE_DATA_ELIMINATION"



On 07-08-2024 21:11, Arnd Bergmann wrote:
> On Wed, Aug 7, 2024, at 17:36, Harith George wrote:
>> On 07-08-2024 20:52, liuyuntao (F) wrote:
>>> Thanks, I reproduce the link error with toolchain
>>> gcc version 9.3.0
>>> GNU ld (GNU Binutils) 2.33.1
>>>
>>> with same gcc version, just upgrading ld version to 2.36.1, it does not
>>> segfault and build completes. there should be bugs in low version of ld,
>>> and the ".reloc  .text, R_ARM_NONE, ." triggers that.
>>>
>> Thanks for confirming.
>>
>> I guess we need to add something like
>> #if !CONFIG_CC_IS_GCC || CONFIG_LD_VERSION >= 23600
>> around the entry-armv.S changes and maybe select
>> HAVE_LD_DEAD_CODE_DATA_ELIMINATION in arch/arm/Kconfig only if the same
>> conditions are met ??
> 
> I think it makes most sense to have a minimum LD
> version as a dependency for HAVE_LD_DEAD_CODE_DATA_ELIMINATION.
> Are you sure that 2.36 is the first one that works, and it's
> not just 2.33 specifically that is broken?
> 
> If so, we could use
> 
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -117,7 +117,7 @@ config ARM
>          select HAVE_KERNEL_XZ
>          select HAVE_KPROBES if !XIP_KERNEL && !CPU_ENDIAN_BE32 && !CPU_V7M && !CPU_32v3
>          select HAVE_KRETPROBES if HAVE_KPROBES
> -       select HAVE_LD_DEAD_CODE_DATA_ELIMINATION
> +       select HAVE_LD_DEAD_CODE_DATA_ELIMINATION if (LD_VERSION >= 23600 || LD_IS_LLD)
>          select HAVE_MOD_ARCH_SPECIFIC
>          select HAVE_NMI
>          select HAVE_OPTPROBES if !THUMB2_KERNEL
>
The select alone may not be enough. Wont the changes in 
arch/arm/kernel/entry-armv.S still result in LD Segfaults even if the 
HAVE_LD_DEAD_CODE_DATA_ELIMINATION flag is not set in .config for older 
toolchains?

Thanks,
Warm Regards,
Harith
> 
> binutils only takes a few seconds to build from source, so
> you could just try all version from 2.25 (the oldest supported)
> to 2.36) to see which ones work.
> 
>         Arnd