Re: [PATCH] arm64: Force position-independent veneers

[Nathan Chancellor <nathan@kernel.org>]

On Fri, Sep 27, 2024 at 11:18:38AM +0100, Mark Rutland wrote:
> Certain portions of code always need to be position-independent
> regardless of CONFIG_RELOCATABLE, including code which is executed in an
> idmap or which is executed before relocations are applied. In some
> kernel configurations the LLD linker generates position-dependent
> veneers for such code, and when executed these result in early boot-time
> failures.
> 
> Marc Zyngier encountered a boot failure resulting from this when
> building a (particularly cursed) configuration with LLVM, as he reported
> to the list:

Heh, I admire the "particularly cursed" bit.

> I've tested with GNU LD 2.30 to 2.42 inclusive and LLVM 13.0.1 to 19.1.0
> inclusive, using the kernel.org binaries from:
> 
> * https://mirrors.edge.kernel.org/pub/tools/crosstool/
> * https://mirrors.edge.kernel.org/pub/tools/llvm/
> 
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> Reported-by: Marc Zyngier <maz@kernel.org>
> Cc: Ard Biesheuvel <ardb@kernel.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Nathan Chancellor <nathan@kernel.org>
> Cc: Nick Desaulniers <ndesaulniers@google.com>
> Cc: Will Deacon <will@kernel.org>

Thanks for the patch!

Reviewed-by: Nathan Chancellor <nathan@kernel.org>

> ---
>  arch/arm64/Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
> index f6bc3da1ef110..c8e237b20ef29 100644
> --- a/arch/arm64/Makefile
> +++ b/arch/arm64/Makefile
> @@ -10,7 +10,7 @@
>  #
>  # Copyright (C) 1995-2001 by Russell King
>  
> -LDFLAGS_vmlinux	:=--no-undefined -X
> +LDFLAGS_vmlinux	:=--no-undefined -X --pic-veneer
>  
>  ifeq ($(CONFIG_RELOCATABLE), y)
>  # Pass --no-apply-dynamic-relocs to restore pre-binutils-2.27 behaviour
> -- 
> 2.30.2
>