[PATCH 4/4] ArmPkg/CpuDxe: Implement EFI memory attributes protocol

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

Expose the protocol introduced in v2.10 that permits the caller to
manage mapping permissions in the page tables.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 ArmPkg/Drivers/CpuDxe/CpuDxe.c          |   2 +
 ArmPkg/Drivers/CpuDxe/CpuDxe.h          |   3 +
 ArmPkg/Drivers/CpuDxe/CpuDxe.inf        |   2 +
 ArmPkg/Drivers/CpuDxe/MemoryAttribute.c | 242 ++++++++++++++++++++
 4 files changed, 249 insertions(+)

diff --git a/ArmPkg/Drivers/CpuDxe/CpuDxe.c b/ArmPkg/Drivers/CpuDxe/CpuDxe.c
index e6742f0a25fc..d04958e79e52 100644
--- a/ArmPkg/Drivers/CpuDxe/CpuDxe.c
+++ b/ArmPkg/Drivers/CpuDxe/CpuDxe.c
@@ -244,6 +244,8 @@ CpuDxeInitialize (
                   &mCpuHandle,
                   &gEfiCpuArchProtocolGuid,
                   &mCpu,
+                  &gEfiMemoryAttributeProtocolGuid,
+                  &mMemoryAttribute,
                   NULL
                   );
 
diff --git a/ArmPkg/Drivers/CpuDxe/CpuDxe.h b/ArmPkg/Drivers/CpuDxe/CpuDxe.h
index 8933fa90c4ed..f45d2bc101a3 100644
--- a/ArmPkg/Drivers/CpuDxe/CpuDxe.h
+++ b/ArmPkg/Drivers/CpuDxe/CpuDxe.h
@@ -30,9 +30,12 @@
 #include <Protocol/Cpu.h>
 #include <Protocol/DebugSupport.h>
 #include <Protocol/LoadedImage.h>
+#include <Protocol/MemoryAttribute.h>
 
 extern BOOLEAN  mIsFlushingGCD;
 
+extern EFI_MEMORY_ATTRIBUTE_PROTOCOL  mMemoryAttribute;
+
 /**
   This function registers and enables the handler specified by InterruptHandler for a processor
   interrupt or exception type specified by InterruptType. If InterruptHandler is NULL, then the
diff --git a/ArmPkg/Drivers/CpuDxe/CpuDxe.inf b/ArmPkg/Drivers/CpuDxe/CpuDxe.inf
index 10792b393fc8..e732e21cb94a 100644
--- a/ArmPkg/Drivers/CpuDxe/CpuDxe.inf
+++ b/ArmPkg/Drivers/CpuDxe/CpuDxe.inf
@@ -23,6 +23,7 @@ [Sources.Common]
   CpuDxe.h
   CpuMmuCommon.c
   Exception.c
+  MemoryAttribute.c
 
 [Sources.ARM]
   Arm/Mmu.c
@@ -53,6 +54,7 @@ [LibraryClasses]
 
 [Protocols]
   gEfiCpuArchProtocolGuid
+  gEfiMemoryAttributeProtocolGuid
 
 [Guids]
   gEfiDebugImageInfoTableGuid
diff --git a/ArmPkg/Drivers/CpuDxe/MemoryAttribute.c b/ArmPkg/Drivers/CpuDxe/MemoryAttribute.c
new file mode 100644
index 000000000000..9aeb83fff1b9
--- /dev/null
+++ b/ArmPkg/Drivers/CpuDxe/MemoryAttribute.c
@@ -0,0 +1,242 @@
+/** @file
+
+  Copyright (c) 2023, Google LLC. All rights reserved.
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#include "CpuDxe.h"
+
+/**
+  This function retrieves the attributes of the memory region specified by
+  BaseAddress and Length. If different attributes are got from different part
+  of the memory region, EFI_NO_MAPPING will be returned.
+
+  @param  This              The EFI_MEMORY_ATTRIBUTE_PROTOCOL instance.
+  @param  BaseAddress       The physical address that is the start address of
+                            a memory region.
+  @param  Length            The size in bytes of the memory region.
+  @param  Attributes        Pointer to attributes returned.
+
+  @retval EFI_SUCCESS           The attributes got for the memory region.
+  @retval EFI_INVALID_PARAMETER Length is zero.
+                                Attributes is NULL.
+  @retval EFI_NO_MAPPING        Attributes are not consistent cross the memory
+                                region.
+  @retval EFI_UNSUPPORTED       The processor does not support one or more
+                                bytes of the memory resource range specified
+                                by BaseAddress and Length.
+
+**/
+STATIC
+EFI_STATUS
+GetMemoryAttributes (
+  IN  EFI_MEMORY_ATTRIBUTE_PROTOCOL       *This,
+  IN  EFI_PHYSICAL_ADDRESS                BaseAddress,
+  IN  UINT64                              Length,
+  OUT UINT64                              *Attributes
+  )
+{
+  UINTN       RegionAddress;
+  UINTN       RegionLength;
+  UINTN       RegionAttributes;
+  UINTN       Union;
+  UINTN       Intersection;
+  EFI_STATUS  Status;
+
+  if ((Length == 0) || (Attributes == NULL)) {
+    return EFI_INVALID_PARAMETER;
+  }
+
+  DEBUG ((DEBUG_INFO,
+          "%a: BaseAddress == 0x%lx, Length == 0x%lx\n",
+          __FUNCTION__,
+          (UINTN)BaseAddress,
+          (UINTN)Length
+          ));
+
+  Union         = 0;
+  Intersection  = MAX_UINTN;
+
+  for (RegionAddress = (UINTN)BaseAddress;
+       RegionAddress < (UINTN)(BaseAddress + Length);
+       RegionAddress += RegionLength) {
+
+    Status = GetMemoryRegion (&RegionAddress,
+                              &RegionLength,
+                              &RegionAttributes
+                              );
+
+    DEBUG ((DEBUG_INFO,
+            "%a: RegionAddress == 0x%lx, RegionLength == 0x%lx, RegionAttributes == 0x%lx\n",
+            __FUNCTION__,
+            RegionAddress,
+            RegionLength,
+            RegionAttributes
+            ));
+
+    if (EFI_ERROR (Status)) {
+      return EFI_NO_MAPPING;
+    }
+
+    Union         |= RegionAttributes;
+    Intersection  &= RegionAttributes;
+  }
+
+  DEBUG ((DEBUG_INFO,
+          "%a: Union == %lx, Intersection == %lx\n",
+          __FUNCTION__,
+          Union,
+          Intersection
+          ));
+
+  if (Union != Intersection) {
+    return EFI_NO_MAPPING;
+  }
+
+  *Attributes = PageAttributeToGcdAttribute (Union) & (EFI_MEMORY_RO | EFI_MEMORY_XP);
+  return EFI_SUCCESS;
+}
+
+/**
+  This function set given attributes of the memory region specified by
+  BaseAddress and Length.
+
+  The valid Attributes is EFI_MEMORY_RP, EFI_MEMORY_XP, and EFI_MEMORY_RO.
+
+  @param  This              The EFI_MEMORY_ATTRIBUTE_PROTOCOL instance.
+  @param  BaseAddress       The physical address that is the start address of
+                            a memory region.
+  @param  Length            The size in bytes of the memory region.
+  @param  Attributes        The bit mask of attributes to set for the memory
+                            region.
+
+  @retval EFI_SUCCESS           The attributes were set for the memory region.
+  @retval EFI_INVALID_PARAMETER Length is zero.
+                                Attributes specified an illegal combination of
+                                attributes that cannot be set together.
+  @retval EFI_UNSUPPORTED       The processor does not support one or more
+                                bytes of the memory resource range specified
+                                by BaseAddress and Length.
+                                The bit mask of attributes is not supported for
+                                the memory resource range specified by
+                                BaseAddress and Length.
+
+**/
+STATIC
+EFI_STATUS
+SetMemoryAttributes (
+  IN  EFI_MEMORY_ATTRIBUTE_PROTOCOL       *This,
+  IN  EFI_PHYSICAL_ADDRESS                BaseAddress,
+  IN  UINT64                              Length,
+  IN  UINT64                              Attributes
+  )
+{
+  EFI_STATUS  Status;
+
+  DEBUG ((DEBUG_INFO,
+          "%a: BaseAddress == 0x%lx, Length == 0x%lx, Attributes == 0x%lx\n",
+          __FUNCTION__,
+          (UINTN)BaseAddress,
+          (UINTN)Length,
+          (UINTN)Attributes
+          ));
+
+  if ((Length == 0) ||
+      ((Attributes & ~(EFI_MEMORY_RO | EFI_MEMORY_RP | EFI_MEMORY_XP)) != 0)) {
+    return EFI_INVALID_PARAMETER;
+  }
+
+  if ((Attributes & EFI_MEMORY_RP) != 0) {
+    return EFI_UNSUPPORTED;
+  }
+
+  if ((Attributes & EFI_MEMORY_RO) != 0) {
+    Status = ArmSetMemoryRegionReadOnly (BaseAddress, Length);
+    if (EFI_ERROR (Status)) {
+      return EFI_UNSUPPORTED;
+    }
+  }
+
+  if ((Attributes & EFI_MEMORY_XP) != 0) {
+    Status = ArmSetMemoryRegionNoExec (BaseAddress, Length);
+    if (EFI_ERROR (Status)) {
+      return EFI_UNSUPPORTED;
+    }
+  }
+
+  return EFI_SUCCESS;
+}
+
+/**
+  This function clears given attributes of the memory region specified by
+  BaseAddress and Length.
+
+  The valid Attributes is EFI_MEMORY_RP, EFI_MEMORY_XP, and EFI_MEMORY_RO.
+
+  @param  This              The EFI_MEMORY_ATTRIBUTE_PROTOCOL instance.
+  @param  BaseAddress       The physical address that is the start address of
+                            a memory region.
+  @param  Length            The size in bytes of the memory region.
+  @param  Attributes        The bit mask of attributes to clear for the memory
+                            region.
+
+  @retval EFI_SUCCESS           The attributes were cleared for the memory region.
+  @retval EFI_INVALID_PARAMETER Length is zero.
+                                Attributes specified an illegal combination of
+                                attributes that cannot be cleared together.
+  @retval EFI_UNSUPPORTED       The processor does not support one or more
+                                bytes of the memory resource range specified
+                                by BaseAddress and Length.
+                                The bit mask of attributes is not supported for
+                                the memory resource range specified by
+                                BaseAddress and Length.
+
+**/
+STATIC
+EFI_STATUS
+ClearMemoryAttributes (
+  IN  EFI_MEMORY_ATTRIBUTE_PROTOCOL       *This,
+  IN  EFI_PHYSICAL_ADDRESS                BaseAddress,
+  IN  UINT64                              Length,
+  IN  UINT64                              Attributes
+  )
+{
+  EFI_STATUS  Status;
+
+  DEBUG ((DEBUG_INFO,
+          "%a: BaseAddress == 0x%lx, Length == 0x%lx, Attributes == 0x%lx\n",
+          __FUNCTION__,
+          (UINTN)BaseAddress,
+          (UINTN)Length,
+          (UINTN)Attributes
+          ));
+
+  if ((Length == 0) ||
+      ((Attributes & ~(EFI_MEMORY_RO | EFI_MEMORY_RP | EFI_MEMORY_XP)) != 0)) {
+    return EFI_INVALID_PARAMETER;
+  }
+
+  if ((Attributes & EFI_MEMORY_RO) != 0) {
+    Status = ArmClearMemoryRegionReadOnly (BaseAddress, Length);
+    if (EFI_ERROR (Status)) {
+      return EFI_UNSUPPORTED;
+    }
+  }
+
+  if ((Attributes & EFI_MEMORY_XP) != 0) {
+    Status = ArmClearMemoryRegionNoExec (BaseAddress, Length);
+    if (EFI_ERROR (Status)) {
+      return EFI_UNSUPPORTED;
+    }
+  }
+
+  return EFI_SUCCESS;
+}
+
+EFI_MEMORY_ATTRIBUTE_PROTOCOL  mMemoryAttribute = {
+  GetMemoryAttributes,
+  SetMemoryAttributes,
+  ClearMemoryAttributes
+};
-- 
2.39.0