Re: [PATCH 3/4] ArmPkg/CpuDxe: ARM: ignore page table updates that only change permissions

[Leif Lindholm <leif.lindholm@linaro.org>]

On Thu, Feb 09, 2017 at 05:38:10PM +0000, Ard Biesheuvel wrote:
> Currently, we have not implemented support on 32-bit ARM for managing
> permission bits in the page tables. Since the new DXE page protection
> for PE/COFF images may invoke EFI_CPU_ARCH_PROTOCOL.SetMemoryAttributes()
> with only permission attributes set, let's simply ignore those for now.
> 
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>

> ---
>  ArmPkg/Drivers/CpuDxe/Arm/Mmu.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/ArmPkg/Drivers/CpuDxe/Arm/Mmu.c b/ArmPkg/Drivers/CpuDxe/Arm/Mmu.c
> index b6ba975b353a..89e429925ba9 100644
> --- a/ArmPkg/Drivers/CpuDxe/Arm/Mmu.c
> +++ b/ArmPkg/Drivers/CpuDxe/Arm/Mmu.c
> @@ -680,6 +680,13 @@ SetMemoryAttributes (
>  {
>    EFI_STATUS    Status;
>  
> +  //
> +  // Ignore invocations that only modify permission bits
> +  //
> +  if ((Attributes & EFI_MEMORY_CACHETYPE_MASK) == 0) {
> +    return EFI_SUCCESS;
> +  }
> +
>    if(((BaseAddress & 0xFFFFF) == 0) && ((Length & 0xFFFFF) == 0)) {
>      // Is the base and length a multiple of 1 MB?
>      DEBUG ((EFI_D_PAGE, "SetMemoryAttributes(): MMU section 0x%x length 0x%x to %lx\n", (UINTN)BaseAddress, (UINTN)Length, Attributes));
> -- 
> 2.7.4
>