linux-kernel - Re: [PATCH] powerpc/vmlinux.lds: Drop .interp description

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Message-ID: <aPdBpqhm3JHvKIWJ@linux.ibm.com>
Date: Tue, 21 Oct 2025 13:48:31 +0530
From: Vishal Chourasia <vishalc@...ux.ibm.com>
To: Nathan Chancellor <nathan@...nel.org>
Cc: Madhavan Srinivasan <maddy@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
        Bill Wendling <morbo@...gle.com>,
        Justin Stitt <justinstitt@...gle.com>, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH] powerpc/vmlinux.lds: Drop .interp description

On Sat, Oct 18, 2025 at 06:52:40PM +0100, Nathan Chancellor wrote:
> Commit da30705c4621 ("arch/powerpc: Remove .interp section in vmlinux")
> intended to drop the .interp section from vmlinux but even with this
> change, relocatable kernels linked with ld.lld contain an empty .interp
> section, which ends up causing crashes in GDB [1].
> 
>   $ make -skj"$(nproc)" ARCH=powerpc LLVM=1 clean pseries_le_defconfig vmlinux
> 
>   $ llvm-readelf -S vmlinux | grep interp
>     [44] .interp           PROGBITS        c0000000021ddb34 21edb34 000000 00   A  0   0  1
> 
> There appears to be a subtle difference between GNU ld and ld.lld when
> it comes to discarding sections that specify load addresses [2].
> 
> Since '--no-dynamic-linker' prevents emission of the .interp section,
> there is no need to describe it in the output sections of the vmlinux
> linker script. Drop the .interp section description from vmlinux.lds.S
> to avoid this issue altogether.
> 
> Link: https://sourceware.org/bugzilla/show_bug.cgi?id=33481 [1]
> Link: https://github.com/ClangBuiltLinux/linux/issues/2137 [2]
> Reported-by: Vishal Chourasia <vishalc@...ux.ibm.com>
> Closes: https://lore.kernel.org/20251013040148.560439-1-vishalc@linux.ibm.com/
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>
> ---
>  arch/powerpc/kernel/vmlinux.lds.S | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
> index de6ee7d35cff..15850296c0a9 100644
> --- a/arch/powerpc/kernel/vmlinux.lds.S
> +++ b/arch/powerpc/kernel/vmlinux.lds.S
> @@ -330,7 +330,6 @@ SECTIONS
>  	}
>  	.hash : AT(ADDR(.hash) - LOAD_OFFSET) { *(.hash) }
>  	.gnu.hash : AT(ADDR(.gnu.hash) - LOAD_OFFSET) { *(.gnu.hash) }
> -	.interp : AT(ADDR(.interp) - LOAD_OFFSET) { *(.interp) }
>  	.rela.dyn : AT(ADDR(.rela.dyn) - LOAD_OFFSET)
>  	{
>  		__rela_dyn_start = .;
> 
> ---
> base-commit: 3a8660878839faadb4f1a6dd72c3179c1df56787
> change-id: 20251018-ppc-fix-lld-interp-1a78c361cd42
> 

With this patch, I don't see .interp section being emitted the final
vmlinux binary.

```
(i) ❯ make LLVM=1 vmlinux
(i) ❯ llvm-readelf -p .comment vmlinux

String dump of section '.comment':
[     1] clang version 22.0.0git (https://github.com/llvm/llvm-project.git 7314565281ec28b745502c3f429fd431e16673eb)
[    6d] Linker: LLD 22.0.0 (https://github.com/llvm/llvm-project.git 7314565281ec28b745502c3f429fd431e16673eb)

(i) ❯ llvm-readelf -p .interp vmlinux
llvm-readelf: warning: 'vmlinux': could not find section '.interp'
```

Tested-by: Vishal Chourasia <vishalc@...ux.ibm.com>