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

[Ard Biesheuvel]

On Wed, 29 Sept 2021 at 21:08, Nick Desaulniers <ndesaulniers@xxxxxxxxxx> 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>
> Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
> ---
>  arch/arm/Kconfig          | 1 +
>  arch/arm/mm/proc-macros.S | 1 +
>  2 files changed, 2 insertions(+)
>
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index fc196421b2ce..b760dd45b734 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -92,6 +92,7 @@ config ARM
>         select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
>         select HAVE_FUNCTION_GRAPH_TRACER if !THUMB2_KERNEL && !CC_IS_CLANG
>         select HAVE_FUNCTION_TRACER if !XIP_KERNEL
> +       select HAVE_FUTEX_CMPXCHG if FUTEX
>         select HAVE_GCC_PLUGINS
>         select HAVE_HW_BREAKPOINT if PERF_EVENTS && (CPU_V6 || CPU_V6K || CPU_V7)
>         select HAVE_IRQ_TIME_ACCOUNTING

I take it this hunk got included by accident?

> 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
> --
> 2.33.0.685.g46640cef36-goog
>

For this part,

Acked-by: Ard Biesheuvel <ardb@xxxxxxxxxx>