Re: [PATCH] arm: Fix build issue with LD_DEAD_CODE_DATA_ELIMINATION

[Harith George <mail2hgg@gmail.com>]

On 08-08-2024 18:05, Yuntao Liu wrote:
> There is a build issue with LD segmentation fault, while
> CONFIG_LD_DEAD_CODE_DATA_ELIMINATION is not enabled, as bellow.
> 
> scripts/link-vmlinux.sh: line 49:  3796 Segmentation fault
>   (core dumped) ${ld} ${ldflags} -o ${output} ${wl}--whole-archive
>   ${objs} ${wl}--no-whole-archive ${wl}--start-group
>   ${libs} ${wl}--end-group ${kallsymso} ${btf_vmlinux_bin_o} ${ldlibs}
> 
> The error occurs in older versions of the GNU ld with version earlier
> than 2.36. It makes most sense to have a minimum LD version as
> a dependency for HAVE_LD_DEAD_CODE_DATA_ELIMINATION and eliminate
> the impact of ".reloc  .text, R_ARM_NONE, ." when
> CONFIG_LD_DEAD_CODE_DATA_ELIMINATION is not enabled.
> 
> Fixes: ed0f94102251 ("ARM: 9404/1: arm32: enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION")
> Reported-by: Harith George <mail2hgg@gmail.com>
> Suggested-by: Arnd Bergmann <arnd@arndb.de>
> Signed-off-by: Yuntao Liu <liuyuntao12@huawei.com>
> Link: https://lore.kernel.org/all/14e9aefb-88d1-4eee-8288-ef15d4a9b059@gmail.com/
> ---
>   arch/arm/Kconfig             |  2 +-
>   arch/arm/kernel/entry-armv.S | 12 +++++++++---
>   2 files changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 54b2bb817a7f..173159e93c99 100644
> --- 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
>   	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
> diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
> index f01d23a220e6..cd443faf8645 100644
> --- a/arch/arm/kernel/entry-armv.S
> +++ b/arch/arm/kernel/entry-armv.S
> @@ -29,6 +29,12 @@
>   #include "entry-header.S"
>   #include <asm/probes.h>
>   
> +#ifdef CONFIG_HAVE_LD_DEAD_CODE_DATA_ELIMINATION
> +#define RELOC_TEXT_NONE (.reloc  .text, R_ARM_NONE, .)
> +#else
> +#define RELOC_TEXT_NONE
> +#endif
> +
>   /*
>    * Interrupt handling.
>    */
> @@ -1065,7 +1071,7 @@ vector_addrexcptn:
>   	.globl	vector_fiq
>   
>   	.section .vectors, "ax", %progbits
> -	.reloc  .text, R_ARM_NONE, .
> +	RELOC_TEXT_NONE
>   	W(b)	vector_rst
>   	W(b)	vector_und
>   ARM(	.reloc	., R_ARM_LDR_PC_G0, .L__vector_swi		)
> @@ -1079,7 +1085,7 @@ THUMB(	.reloc	., R_ARM_THM_PC12, .L__vector_swi		)
>   
>   #ifdef CONFIG_HARDEN_BRANCH_HISTORY
>   	.section .vectors.bhb.loop8, "ax", %progbits
> -	.reloc  .text, R_ARM_NONE, .
> +	RELOC_TEXT_NONE
>   	W(b)	vector_rst
>   	W(b)	vector_bhb_loop8_und
>   ARM(	.reloc	., R_ARM_LDR_PC_G0, .L__vector_bhb_loop8_swi	)
> @@ -1092,7 +1098,7 @@ THUMB(	.reloc	., R_ARM_THM_PC12, .L__vector_bhb_loop8_swi	)
>   	W(b)	vector_bhb_loop8_fiq
>   
>   	.section .vectors.bhb.bpiall, "ax", %progbits
> -	.reloc  .text, R_ARM_NONE, .
> +	RELOC_TEXT_NONE
>   	W(b)	vector_rst
>   	W(b)	vector_bhb_bpiall_und
>   ARM(	.reloc	., R_ARM_LDR_PC_G0, .L__vector_bhb_bpiall_swi	)
Build tested. Solves the earlier build issue I was seeing.
fwiw, you can add my tested by tag if needed.

Tested-by: Harith George <mail2hgg@gmail.com>