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
>