[edk2-devel] [PATCH v5 21/38] ArmPkg: Implement ArmSetMemoryOverrideLib

[Leif Lindholm]

On Mon, Mar 13, 2023 at 18:16:57 +0100, Ard Biesheuvel wrote:
> Implement the ARM version of a NULL class library that can be overlaid
> on top of the DXE core to equip it right from its launch with an
> implementation of the CPU arch protocol member that sets type and
> permission attributes on memory regions.
> 
> This bridges the gap between dispatch of DXE core and dispatch of the
> DXE driver that implements the CPU arch protocol, removing the need to
> rely on memory mappings that are writable and executable at the same
> time.
> 
> Signed-off-by: Ard Biesheuvel <ardb at kernel.org>
> ---
>  ArmPkg/ArmPkg.dsc                                                  |  1 +
>  ArmPkg/Library/ArmSetMemoryOverrideLib/ArmSetMemoryOverrideLib.c   | 78 ++++++++++++++++++++
>  ArmPkg/Library/ArmSetMemoryOverrideLib/ArmSetMemoryOverrideLib.inf | 28 +++++++
>  3 files changed, 107 insertions(+)
> 
> diff --git a/ArmPkg/ArmPkg.dsc b/ArmPkg/ArmPkg.dsc
> index 3fb95d1951a9..43eb0f4f463e 100644
> --- a/ArmPkg/ArmPkg.dsc
> +++ b/ArmPkg/ArmPkg.dsc
> @@ -119,6 +119,7 @@ [Components.common]
>    ArmPkg/Library/ArmPsciResetSystemLib/ArmPsciResetSystemLib.inf
>    ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.inf
>    ArmPkg/Library/ArmExceptionLib/ArmRelocateExceptionLib.inf
> +  ArmPkg/Library/ArmSetMemoryOverrideLib/ArmSetMemoryOverrideLib.inf
>  
>    ArmPkg/Drivers/CpuDxe/CpuDxe.inf
>    ArmPkg/Drivers/CpuPei/CpuPei.inf
> diff --git a/ArmPkg/Library/ArmSetMemoryOverrideLib/ArmSetMemoryOverrideLib.c b/ArmPkg/Library/ArmSetMemoryOverrideLib/ArmSetMemoryOverrideLib.c
> new file mode 100644
> index 000000000000..866dbbdaa7d5
> --- /dev/null
> +++ b/ArmPkg/Library/ArmSetMemoryOverrideLib/ArmSetMemoryOverrideLib.c
> @@ -0,0 +1,78 @@
> +/** @file
> +  Overlay implementation of DXE core gCpuSetMemoryAttributes for ARM.
> +
> +  Copyright (c) 2023, Google LLC. All rights reserved.
> +
> +  SPDX-License-Identifier: BSD-2-Clause-Patent
> +**/
> +
> +#include <PiDxe.h>
> +
> +#include <Library/ArmMmuLib.h>
> +#include <Library/DebugLib.h>
> +#include <Protocol/Cpu.h>
> +
> +extern EFI_CPU_SET_MEMORY_ATTRIBUTES  gCpuSetMemoryAttributes;

Could this declaration live in a global include?

/
    Leif

> +
> +STATIC UINTN  mRecursionLevel;
> +
> +/**
> +  Clone of CPU_ARCH_PROTOCOL::SetMemoryAttributes() which is made available to
> +  the DXE core by NULL library class resolution, so that it can manage page
> +  permissions right from the start.
> +
> +  @param  This                  CPU arch protocol pointer, should be NULL.
> +  @param  BaseAddress           Start address of the region.
> +  @param  Length                Size of the region, in bytes.
> +  @param  Attributes            Attributes to set on the region.
> +
> +  @retval EFI_SUCCESS           Operation completed successfully.
> +  @retval EFI_OUT_OF_RESOURCES  Operation failed due to lack of memory.
> +
> +**/
> +STATIC
> +EFI_STATUS
> +EFIAPI
> +EarlyArmSetMemoryAttributes (
> +  IN  EFI_CPU_ARCH_PROTOCOL  *This,
> +  IN  EFI_PHYSICAL_ADDRESS   BaseAddress,
> +  IN  UINT64                 Length,
> +  IN  UINT64                 Attributes
> +  )
> +{
> +  EFI_STATUS  Status;
> +
> +  // There are cases where the use of strict memory permissions may trigger
> +  // unbounded recursion in the page table code. This happens when setting
> +  // memory permissions results in a page table split and therefore a page
> +  // allocation, which could trigger a recursive invocation of this function.
> +  ASSERT (mRecursionLevel < 2);
> +
> +  mRecursionLevel++;
> +
> +  Status = ArmSetMemoryAttributes (
> +             BaseAddress,
> +             Length,
> +             Attributes
> +             );
> +
> +  mRecursionLevel--;
> +  return Status;
> +}
> +
> +/**
> +  Library constructor.
> +
> +  @retval RETURN_SUCCESS   Operation successful.
> +
> +**/
> +RETURN_STATUS
> +EFIAPI
> +ArmSetMemoryOverrideLibConstructor (
> +  VOID
> +  )
> +{
> +  gCpuSetMemoryAttributes = EarlyArmSetMemoryAttributes;
> +
> +  return RETURN_SUCCESS;
> +}
> diff --git a/ArmPkg/Library/ArmSetMemoryOverrideLib/ArmSetMemoryOverrideLib.inf b/ArmPkg/Library/ArmSetMemoryOverrideLib/ArmSetMemoryOverrideLib.inf
> new file mode 100644
> index 000000000000..2dc9d42d09bd
> --- /dev/null
> +++ b/ArmPkg/Library/ArmSetMemoryOverrideLib/ArmSetMemoryOverrideLib.inf
> @@ -0,0 +1,28 @@
> +## @file
> +#  Overlay implementation of DXE core gCpuSetMemoryAttributes for ARM.
> +#
> +#  Copyright (c) 2023, Google LLC. All rights reserved.
> +#
> +#  SPDX-License-Identifier: BSD-2-Clause-Patent
> +#
> +##
> +
> +[Defines]
> +  INF_VERSION                    = 1.29
> +  BASE_NAME                      = ArmSetMemoryOverrideLib
> +  FILE_GUID                      = 849a43c0-6ad9-428e-8a5a-e090f7853bd3
> +  MODULE_TYPE                    = BASE
> +  VERSION_STRING                 = 1.0
> +  LIBRARY_CLASS                  = NULL|DXE_CORE
> +  CONSTRUCTOR                    = ArmSetMemoryOverrideLibConstructor
> +
> +[Sources.common]
> +  ArmSetMemoryOverrideLib.c
> +
> +[Packages]
> +  ArmPkg/ArmPkg.dec
> +  MdePkg/MdePkg.dec
> +
> +[LibraryClasses]
> +  ArmMmuLib
> +  DebugLib
> -- 
> 2.39.2
> 
> 
> 
> 
> 
> 


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