Re: [PATCH v2 11/16] ArmPkg: Add Basic MMU Lib for Arm silicon

["Leif Lindholm" <leif@nuviainc.com>]

On Tue, Nov 02, 2021 at 13:17:43 -0700, brbarkel@microsoft.com wrote:
> From: Sean Brogan <sean.brogan@microsoft.com>
> 
> The previously Arm-specific "ArmMmuLib" has been generalized
> as "MmuLib". The Arm implementation of this lib can still use
> the existing library logic to back it.
> 
> As such, this implementation is currently just a shim to the
> old library, while enabling higher-level code to be more
> common.

This commit message still required me to go and cross refecence a few
patches to (I think) understand what's going on.
(not least because it relies on a patch to MdePkg which I wasn't cc:d
on, so hadn't spotted.)

Correct me if I've got this wrong, but here's my theory:
- 8/16 adds a library class that currently basically amounts to an
  unabstracted version of ArmMmuLib, but in MdePkg, minus the Arm
  prefixes.
- 9/16 switches MdeModulePkg to use the new MmuLib instead of
  ArmMmuLib.
- 10/16 does the same for StandaloneMmPkg.
- 11/16 adds an actual implementation of this library class under
  ArmPkg - backed by ArmMmuLib.

If that's accurate...

Starting with the commit message - could we reduce the use of passive
voice a bit? Suggestion:

---
After adding the abstract MmuLib to MdePkg, add an implementation
backed by the existing ArmMmuLib to ArmPkg.
---

While not required functionality-wise, it would also feel more logical
to me to add the arch-specific implementation immediately after the
abstract version rather than a few patches down the set (kees the
reviewer in the same context).

/
    Leif

> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3651
> 
> Cc: Leif Lindholm <leif@nuviainc.com>
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> Cc: Sean Brogan <sean.brogan@microsoft.com>
> Signed-off-by: Bret Barkelew <bret.barkelew@microsoft.com>
> ---
>  ArmPkg/Library/MmuLib/MmuLib.c       | 120 ++++++++++++++++++++
>  ArmPkg/ArmPkg.dsc                    |   1 +
>  ArmPkg/Library/MmuLib/BaseMmuLib.inf |  30 +++++
>  3 files changed, 151 insertions(+)
> 
> diff --git a/ArmPkg/Library/MmuLib/MmuLib.c b/ArmPkg/Library/MmuLib/MmuLib.c
> new file mode 100644
> index 000000000000..70840c26f489
> --- /dev/null
> +++ b/ArmPkg/Library/MmuLib/MmuLib.c
> @@ -0,0 +1,120 @@
> +/** @file
> +This library instance implements a very limited MMU Lib instance
> +for the ARM/AARCH64 architectures.  This library shims a common library
> +interface to the ArmPkg defined ArmMmuLib.ib.
> +
> +Copyright (c) Microsoft Corporation.
> +SPDX-License-Identifier: BSD-2-Clause-Patent
> +
> +**/
> +
> +#include <Library/ArmMmuLib.h>
> +#include <Library/DebugLib.h>
> +#include <Library/MmuLib.h>
> +
> +/**
> +  Bitwise sets the memory attributes on a range of memory based on an attributes mask.
> +
> +  @param  BaseAddress           The start of the range for which to set attributes.
> +  @param  Length                The length of the range.
> +  @param  Attributes            A bitmask of the attributes to set. See "Physical memory
> +                                protection attributes" in UefiSpec.h
> +
> +  @return EFI_SUCCESS
> +  @return Others
> +
> +**/
> +EFI_STATUS
> +EFIAPI
> +MmuSetAttributes (
> +  IN  EFI_PHYSICAL_ADDRESS      BaseAddress,
> +  IN  UINT64                    Length,
> +  IN  UINT64                    Attributes
> +  )
> +  {
> +    EFI_STATUS Status;
> +
> +    Status = EFI_UNSUPPORTED;
> +
> +    if (Attributes & EFI_MEMORY_XP) {
> +      Status = ArmSetMemoryRegionNoExec (BaseAddress, Length);
> +      if (EFI_ERROR(Status)) {
> +        DEBUG((DEBUG_ERROR, "%a - Failed to set NX.  Status = %r\n", __FUNCTION__, Status));
> +      }
> +    }
> +
> +    ASSERT_EFI_ERROR(Status);
> +    return Status;
> +  }
> +
> +
> +/**
> +  Bitwise clears the memory attributes on a range of memory based on an attributes mask.
> +
> +  @param  BaseAddress           The start of the range for which to clear attributes.
> +  @param  Length                The length of the range.
> +  @param  Attributes            A bitmask of the attributes to clear. See "Physical memory
> +                                protection attributes" in UefiSpec.h
> +
> +  @return EFI_SUCCESS
> +  @return Others
> +
> +**/
> +EFI_STATUS
> +EFIAPI
> +MmuClearAttributes (
> +  IN  EFI_PHYSICAL_ADDRESS      BaseAddress,
> +  IN  UINT64                    Length,
> +  IN  UINT64                    Attributes
> +  )
> +  {
> +    EFI_STATUS Status;
> +
> +    Status = EFI_UNSUPPORTED;
> +
> +    if (Attributes & EFI_MEMORY_XP) {
> +      Status = ArmClearMemoryRegionNoExec (BaseAddress, Length);
> +      if (EFI_ERROR(Status)) {
> +        DEBUG((DEBUG_ERROR, "%a - Failed to clear NX.  Status = %r\n", __FUNCTION__, Status));
> +      }
> +    }
> +
> +    if (Attributes & EFI_MEMORY_RO) {
> +      Status = ArmClearMemoryRegionReadOnly(BaseAddress, Length);
> +      if (EFI_ERROR(Status)) {
> +        DEBUG((DEBUG_ERROR, "%a - Failed to clear RO.  Status = %r\n", __FUNCTION__, Status));
> +      }
> +    }
> +
> +    ASSERT_EFI_ERROR(Status);
> +    return Status;
> +  }
> +
> +
> +/**
> +  Returns the memory attributes on a range of memory.
> +
> +  @param  BaseAddress           The start of the range for which to set attributes.
> +  @param  Attributes            A return pointer for the attributes.
> +
> +  @return EFI_SUCCESS
> +  @return EFI_INVALID_PARAMETER   A return pointer is NULL.
> +  @return Others
> +
> +**/
> +EFI_STATUS
> +EFIAPI
> +MmuGetAttributes (
> +  IN  EFI_PHYSICAL_ADDRESS      BaseAddress,
> +  OUT UINT64                    *Attributes
> +  )
> +  {
> +    EFI_STATUS Status;
> +
> +    Status = EFI_UNSUPPORTED;
> +
> +    DEBUG ((DEBUG_ERROR, "%a() API not implemented\n", __FUNCTION__));
> +
> +    ASSERT_EFI_ERROR(Status);
> +    return Status;
> +  }
> diff --git a/ArmPkg/ArmPkg.dsc b/ArmPkg/ArmPkg.dsc
> index 06ede068f99d..cbc67daa7696 100644
> --- a/ArmPkg/ArmPkg.dsc
> +++ b/ArmPkg/ArmPkg.dsc
> @@ -165,3 +165,4 @@ [Components.AARCH64]
>  
>  [Components.AARCH64, Components.ARM]
>    ArmPkg/Library/StandaloneMmMmuLib/ArmMmuStandaloneMmLib.inf
> +  ArmPkg/Library/MmuLib/BaseMmuLib.inf
> diff --git a/ArmPkg/Library/MmuLib/BaseMmuLib.inf b/ArmPkg/Library/MmuLib/BaseMmuLib.inf
> new file mode 100644
> index 000000000000..15095abee9c3
> --- /dev/null
> +++ b/ArmPkg/Library/MmuLib/BaseMmuLib.inf
> @@ -0,0 +1,30 @@
> +## @file
> +# This library instance implements a very limited MMU Lib instance
> +# for the ARM/AARCH64 architectures.  This library shims a common library
> +# interface to the ArmPkg defined ArmMmuLib.
> +#
> +# Copyright (c) Microsoft Corporation.
> +#
> +# SPDX-License-Identifier: BSD-2-Clause-Patent
> +#
> +##
> +
> +[Defines]
> +  INF_VERSION                    = 0x00010005
> +  BASE_NAME                      = MmuLib
> +  FILE_GUID                      = 6f2ee9a4-79b3-4b77-9a47-e2bd4b917b75
> +  MODULE_TYPE                    = BASE
> +  VERSION_STRING                 = 1.0
> +  LIBRARY_CLASS                  = MmuLib
> +
> +[Sources]
> +  MmuLib.c
> +
> +[Packages]
> +  MdePkg/MdePkg.dec
> +  MdeModulePkg/MdeModulePkg.dec
> +  ArmPkg/ArmPkg.dec
> +
> +[LibraryClasses]
> +  DebugLib
> +  ArmMmuLib
> -- 
> 2.31.1.windows.1
>