linux-kernel - Re: [PATCH 1/2] arm64: vdso32: Shuffle .ARM.exidx section above ELF

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Message-ID: <Yr3C04jufBhzGJe2@dev-arch.thelio-3990X>
Date:   Thu, 30 Jun 2022 08:35:47 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>
Cc:     Joey Gouly <joey.gouly@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev
Subject: Re: [PATCH 1/2] arm64: vdso32: Shuffle .ARM.exidx section above
 ELF_DETAILS

On Thu, Jun 30, 2022 at 08:31:20AM -0700, Nathan Chancellor wrote:
> When building the 32-bit vDSO after commit 5c4fb60816ea ("arm64: vdso32:
> add ARM.exidx* sections"), ld.lld 11 fails to link:
> 
>   ld.lld: error: could not allocate headers
>   ld.lld: error: unable to place section .text at file offset [0x2A0, 0xBB1]; check your linker script for overflows
>   ld.lld: error: unable to place section .comment at file offset [0xBB2, 0xC8A]; check your linker script for overflows
>   ld.lld: error: unable to place section .symtab at file offset [0xC8C, 0xE0B]; check your linker script for overflows
>   ld.lld: error: unable to place section .strtab at file offset [0xE0C, 0xF1C]; check your linker script for overflows
>   ld.lld: error: unable to place section .shstrtab at file offset [0xF1D, 0xFAA]; check your linker script for overflows
>   ld.lld: error: section .ARM.exidx file range overlaps with .hash
>   >>> .ARM.exidx range is [0x90, 0xCF]
>   >>> .hash range is [0xB4, 0xE3]
> 
>   ld.lld: error: section .hash file range overlaps with .ARM.attributes
>   >>> .hash range is [0xB4, 0xE3]
>   >>> .ARM.attributes range is [0xD0, 0x10B]
> 
>   ld.lld: error: section .ARM.attributes file range overlaps with .dynsym
>   >>> .ARM.attributes range is [0xD0, 0x10B]
>   >>> .dynsym range is [0xE4, 0x133]
> 
>   ld.lld: error: section .ARM.exidx virtual address range overlaps with .hash
>   >>> .ARM.exidx range is [0x90, 0xCF]
>   >>> .hash range is [0xB4, 0xE3]
> 
>   ld.lld: error: section .ARM.exidx load address range overlaps with .hash
>   >>> .ARM.exidx range is [0x90, 0xCF]
>   >>> .hash range is [0xB4, 0xE3]
> 
> This was fixed in ld.lld 12 with a change to match GNU ld's semantics of
> placing non-SHF_ALLOC sections after SHF_ALLOC sections.
> 
> To workaround this issue, move the .ARM.exidx section before the
> .comment, .symtab, .strtab, and .shstrtab sections (ELF_DETAILS) so that
> those sections remain contiguous with the .ARM.attributes section.
> 
> Fixes: 5c4fb60816ea ("arm64: vdso32: add ARM.exidx* sections")

This should have been included to point out the exact commit that fixed
this in ld.lld, I can resend if necessary (since I also screwed up the
patches@...ts.linux.dev domain...)

Link: https://github.com/llvm/llvm-project/commit/ec29538af2e0886a65f479d6a533956a1c478132

> Signed-off-by: Nathan Chancellor <nathan@...nel.org>
> ---
>  arch/arm64/kernel/vdso32/vdso.lds.S | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kernel/vdso32/vdso.lds.S b/arch/arm64/kernel/vdso32/vdso.lds.S
> index 6e67a6524d58..c25bed8e6df1 100644
> --- a/arch/arm64/kernel/vdso32/vdso.lds.S
> +++ b/arch/arm64/kernel/vdso32/vdso.lds.S
> @@ -56,8 +56,8 @@ SECTIONS
>  
>  	.rel.dyn	: { *(.rel*) }
>  
> -	ELF_DETAILS
>  	.ARM.exidx : { *(.ARM.exidx*) }
> +	ELF_DETAILS
>  	.ARM.attributes 0 : { *(.ARM.attributes) }
>  
>  	/DISCARD/	: {
> -- 
> 2.37.0
>