Re: [PATCH 2/2] ArmPkg/ArmMmuLib: Fix ArmReplaceLiveTranslationEntry() alignment

["Leif Lindholm" <quic_llindhol@quicinc.com>]

On Mon, Apr 17, 2023 at 18:09:16 +0000, Marvin Häuser wrote:
> As the ASM_FUNC() macro performs a section switch, the preceding
> .balign directive applies the alignment constraint to the current
> location in the previous section. As the linker may not merge the
> sections in-order, ArmReplaceLiveTranslationEntry() may be left
> unaligned.
> 
> Replace the explicit invocation of .balign with the ASM_FUNC_ALIGN()
> macro, which guarantees the alignment constraint is applied correctly.
> 
> Signed-off-by: Marvin Häuser <mhaeuser@posteo.de>
> Cc: Leif Lindholm <quic_llindhol@quicinc.com>
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> Cc: Sami Mujawar <sami.mujawar@arm.com>
> Cc: Vitaly Cheptsov <vit9696@protonmail.com>

Assuming we reach consensus on the preceding patch, this one is a no
brainer:
Reviewed-by: Leif Lindholm <quic_llindhol@quicinc.com>

> ---
>  ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibReplaceEntry.S | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibReplaceEntry.S b/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibReplaceEntry.S
> index e936a5be4e11..7627aeb95464 100644
> --- a/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibReplaceEntry.S
> +++ b/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibReplaceEntry.S
> @@ -69,17 +69,16 @@
>  .L2_\@:
>    .endm
>  
> -  // Align this routine to a log2 upper bound of its size, so that it is
> -  // guaranteed not to cross a page or block boundary.
> -  .balign 0x200
> -
>  //VOID
>  //ArmReplaceLiveTranslationEntry (
>  //  IN  UINT64  *Entry,
>  //  IN  UINT64  Value,
>  //  IN  UINT64  Address
>  //  )
> -ASM_FUNC(ArmReplaceLiveTranslationEntry)
> +//
> +// Align this routine to a log2 upper bound of its size, so that it is
> +// guaranteed not to cross a page or block boundary.
> +ASM_FUNC_ALIGN(ArmReplaceLiveTranslationEntry, 0x200)
>  
>    // disable interrupts
>    mrs   x4, daif
> -- 
> 2.40.0
>