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

["Bret Barkelew" <bret@corthon.com>]

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Will address in next release.

On Thu, Nov 4, 2021 at 5:43 AM Leif Lindholm <leif@nuviainc.com> wrote:

> 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
> >
>

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