Re: [PATCH v2] ARM: mm: proc-macros: ensure *_tlb_fns are 4B aligned

[Nathan Chancellor]

On Wed, Sep 29, 2021 at 12:20:24PM -0700, Nick Desaulniers wrote:
> QEMU 6.1.0 is more correct about trapping on misaligned accesses. A
> kernel built with CONFIG_THUMB2_KERNEL=y and using clang as the
> assembler could generate non-naturally-aligned v7wbi_tlb_fns which
> results in a boot failure. The original commit adding the macro missed
> the .align directive on this data.
> 
> Fixes: 66a625a88174 ("ARM: mm: proc-macros: Add generic proc/cache/tlb struct definition macros")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1447
> Link: https://lore.kernel.org/all/0699da7b-354f-aecc-a62f-e25693209af4@xxxxxxxxxx/
> Debugged-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
> Debugged-by: Nathan Chancellor <nathan@xxxxxxxxxx>
> Debugged-by: Richard Henderson <richard.henderson@xxxxxxxxxx>
> Suggested-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
> Acked-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
> Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>

Tested-by: Nathan Chancellor <nathan@xxxxxxxxxx>

> ---
> Changes V1 -> V2:
> * Drop accidentally committed Kconfig change.
> * Pick up Ard's AB tag.
> 
>  arch/arm/mm/proc-macros.S | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/arm/mm/proc-macros.S b/arch/arm/mm/proc-macros.S
> index e2c743aa2eb2..d9f7dfe2a7ed 100644
> --- a/arch/arm/mm/proc-macros.S
> +++ b/arch/arm/mm/proc-macros.S
> @@ -340,6 +340,7 @@ ENTRY(\name\()_cache_fns)
>  
>  .macro define_tlb_functions name:req, flags_up:req, flags_smp
>  	.type	\name\()_tlb_fns, #object
> +	.align 2
>  ENTRY(\name\()_tlb_fns)
>  	.long	\name\()_flush_user_tlb_range
>  	.long	\name\()_flush_kern_tlb_range
> 
> base-commit: 02d5e016800d082058b3d3b7c3ede136cdc6ddcb
> prerequisite-patch-id: 3edbe4a8485c7a75a61dbbe299e8ce1985d87ee0
> -- 
> 2.33.0.685.g46640cef36-goog
> 
>