On Thu, 20 Apr 2023 at 17:24, 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.
> To make sure related issues are reliably caught in the future, align the
> end of the function before checking the total occupied size. This
> ensures crossing a 0x200 boundary will cause a compilation error.
>
> Reviewed-by: Leif Lindholm
> Signed-off-by: Marvin Häuser
> Cc: Leif Lindholm
> Cc: Ard Biesheuvel
> Cc: Sami Mujawar
> Cc: Vitaly Cheptsov
Thanks. I've queued these up as #4291
> ---
> .../ArmMmuLib/AArch64/ArmMmuLibReplaceEntry.S | 14 --
> 1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibReplaceEntry.S
> b/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibReplaceEntry.S
> index e936a5be4e11..887439bc042f 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
> @@ -101,5 +100,8 @@ ASM_GLOBAL ASM_PFX(ArmReplaceLiveTranslationEntrySize)
> ASM_PFX(ArmReplaceLiveTranslationEntrySize):
>.long . - ArmReplaceLiveTranslationEntry
>
> - // Double check that we did not overrun the assumed maximum size
> + // Double check that we did not overrun the assumed maximum size or cross a
> + // 0x200 boundary (and thus implicitly not any larger power of two,
> including
> + // the page size).
> + .balign 0x200
>.orgArmReplaceLiveTranslationEntry + 0x200
> --
> 2.40.0
>
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