Re: [edk2-devel] [PATCH v2 1/1] ArmPkg/Drivers/CpuDxe: Use lower and upper attributes

["Ard Biesheuvel" <ardb@kernel.org>]

On Tue, 28 Nov 2023 at 18:12, <mikuback@linux.microsoft.com> wrote:
>
> From: Michael Kubacki <michael.kubacki@microsoft.com>
>
> GetNextEntryAttribute() is currently applying a 64-bit mask
> (TT_ATTRIBUTES_MASK) to a 32-bit descriptor value (EntryType).
> The original descriptor was 64 bits containing the upper and
> lower attributes which are included in TT_ATTRIBUTES_MASK.
>
> The PrevEntryAttribute parameter is also a UINT32, but passed to
> PageAttributeToGcdAttribute() for a UINT64 parameter where the
> function checks masks in the upper 32 bits of the integer value:
>
>   PageAttributeToGcdAttribute (*PrevEntryAttribute)
>   ...
>   STATIC
>   UINT64
>   PageAttributeToGcdAttribute (
>     IN UINT64  PageAttributes
>     )
>   ...
>   if ((PageAttributes & (TT_PXN_MASK | TT_UXN_MASK)) != 0) {
>     GcdAttributes |= EFI_MEMORY_XP;
>   }
>   ...
>   #define TT_PXN_MASK  BIT53
>   #define TT_UXN_MASK  BIT54  // EL1&0
>
> This change removes UINT32 intermediary values. For EntryType,
> eliminating an unncessary cast. For EntryAttribute, preserving the
> upper and lower attributes for evaluation in
> PageAttributeToGcdAttribute().
>
> This also resolves the following compiler warning previously present
> on Visual Studio for the assignment to the previously 32-bit local
> variables.
>
>   '=': conversion from 'UINT64' to 'UINT32', possible loss of data
>
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> Cc: Leif Lindholm <quic_llindhol@quicinc.com>
> Cc: Sami Mujawar <sami.mujawar@arm.com>
> Signed-off-by: Michael Kubacki <michael.kubacki@microsoft.com>


Reviewed-by: Ard Biesheuvel <ardb@kernel.org>

Queued up now - thanks.


> ---
>  ArmPkg/Drivers/CpuDxe/AArch64/Mmu.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/ArmPkg/Drivers/CpuDxe/AArch64/Mmu.c b/ArmPkg/Drivers/CpuDxe/AArch64/Mmu.c
> index e14eb47ce4c6..ff14c2f814b2 100644
> --- a/ArmPkg/Drivers/CpuDxe/AArch64/Mmu.c
> +++ b/ArmPkg/Drivers/CpuDxe/AArch64/Mmu.c
> @@ -13,7 +13,7 @@ SPDX-License-Identifier: BSD-2-Clause-Patent
>  #include <Library/MemoryAllocationLib.h>
>  #include "CpuDxe.h"
>
> -#define INVALID_ENTRY  ((UINT32)~0)
> +#define INVALID_ENTRY  ((UINT64)~0)
>
>  #define MIN_T0SZ        16
>  #define BITS_PER_LEVEL  9
> @@ -169,14 +169,14 @@ GetNextEntryAttribute (
>    IN     UINTN   EntryCount,
>    IN     UINTN   TableLevel,
>    IN     UINT64  BaseAddress,
> -  IN OUT UINT32  *PrevEntryAttribute,
> +  IN OUT UINT64  *PrevEntryAttribute,
>    IN OUT UINT64  *StartGcdRegion
>    )
>  {
>    UINTN                            Index;
>    UINT64                           Entry;
> -  UINT32                           EntryAttribute;
> -  UINT32                           EntryType;
> +  UINT64                           EntryAttribute;
> +  UINT64                           EntryType;
>    EFI_STATUS                       Status;
>    UINTN                            NumberOfDescriptors;
>    EFI_GCD_MEMORY_SPACE_DESCRIPTOR  *MemorySpaceMap;
> @@ -271,7 +271,7 @@ SyncCacheConfig (
>    )
>  {
>    EFI_STATUS                       Status;
> -  UINT32                           PageAttribute;
> +  UINT64                           PageAttribute;
>    UINT64                           *FirstLevelTableAddress;
>    UINTN                            TableLevel;
>    UINTN                            TableCount;
> --
> 2.42.0.windows.2
>


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