[PATCH v3 1/4] MdeModulePkg/CapsuleRuntimeDxe: clean the capsule payload to DRAM

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

When capsule updates are staged for processing after a warm reboot,
they are copied into memory with the MMU and caches enabled. When
the capsule PEI gets around to coalescing the capsule, the MMU and
caches may still be disabled, and so on architectures where uncached
accesses are incoherent with the caches (such as ARM and AARCH64),
we need to ensure that the data passed into UpdateCapsule() is
written back to main memory before performing the warm reboot.

Unfortunately, on ARM, the only type of cache maintenance instructions
that are suitable for this purpose operate on virtual addresses only,
and given that the UpdateCapsule() prototype includes the physical
address of a linked list of scatter/gather data structures that are
mapped at an address that is unknown to the firmware (and may not even
be mapped at all when UpdateCapsule() is invoked), we can only perform
this cache maintenance at boot time. Fortunately, both Windows and Linux
only invoke UpdateCapsule() before calling ExitBootServices(), so this
is not a problem in practice.

In the future, we may propose adding a secure firmware service that
permits performing the cache maintenance at OS runtime, in which case
this code may be enhanced to call that service if available. For now,
we just fail any UpdateCapsule() calls performed at OS runtime on ARM.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 MdeModulePkg/Universal/CapsuleRuntimeDxe/Arm/CacheMaintenance.c | 70 ++++++++++++++++++++
 MdeModulePkg/Universal/CapsuleRuntimeDxe/CacheMaintenance.c     | 39 +++++++++++
 MdeModulePkg/Universal/CapsuleRuntimeDxe/CapsuleRuntimeDxe.inf  | 13 +++-
 MdeModulePkg/Universal/CapsuleRuntimeDxe/CapsuleService.c       | 24 +++++++
 4 files changed, 144 insertions(+), 2 deletions(-)

diff --git a/MdeModulePkg/Universal/CapsuleRuntimeDxe/Arm/CacheMaintenance.c b/MdeModulePkg/Universal/CapsuleRuntimeDxe/Arm/CacheMaintenance.c
new file mode 100644
index 000000000000..dc05e345fb8d
--- /dev/null
+++ b/MdeModulePkg/Universal/CapsuleRuntimeDxe/Arm/CacheMaintenance.c
@@ -0,0 +1,70 @@
+ /** @file
+  Capsule cache maintenance as is required on ARM and AARCH64
+
+  Copyright (c) 2018, Linaro, Ltd. All rights reserved.<BR>
+
+  This program and the accompanying materials are licensed and made available
+  under the terms and conditions of the BSD License which accompanies this
+  distribution.  The full text of the license may be found at
+  http://opensource.org/licenses/bsd-license.php
+
+  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+
+**/
+
+#include <Uefi.h>
+
+#include <Library/CacheMaintenanceLib.h>
+#include <Library/UefiRuntimeLib.h>
+
+/**
+  Writes Back a range of data cache lines covering a set of capsules in memory.
+
+  Writes Back the data cache lines specified by ScatterGatherList.
+
+  @param  ScatterGatherList Physical address of the data structure that
+                            describes a set of capsules in memory
+
+  @return EFI_SUCCESS       if the operation succeeded.
+          EFI_UNSUPPORTED   if cache maintenance cannot be performed at this
+                            time.
+
+**/
+EFI_STATUS
+EFIAPI
+CapsuleCacheWriteBack (
+  IN  EFI_PHYSICAL_ADDRESS    ScatterGatherList
+  )
+{
+  EFI_CAPSULE_BLOCK_DESCRIPTOR    *Desc;
+
+  //
+  // ARM requires the capsule payload to be cleaned to the point of coherency
+  // (PoC), but only permits doing so using cache maintenance instructions that
+  // operate on virtual addresses. Since at runtime, we don't know the virtual
+  // addresses of the data structures that make up the scatter/gather list, we
+  // cannot perform the maintenance, and all we can do is give up.
+  //
+  if (EfiAtRuntime ()) {
+    return EFI_UNSUPPORTED;
+  }
+
+  Desc = (EFI_CAPSULE_BLOCK_DESCRIPTOR *)(UINTN)ScatterGatherList;
+  do {
+    WriteBackDataCacheRange (Desc, sizeof *Desc);
+
+    if (Desc->Length > 0) {
+      WriteBackDataCacheRange ((VOID *)(UINTN)Desc->Union.DataBlock,
+                               Desc->Length
+                               );
+      Desc++;
+    } else if (Desc->Union.ContinuationPointer > 0) {
+      Desc = (EFI_CAPSULE_BLOCK_DESCRIPTOR *)(UINTN)Desc->Union.ContinuationPointer;
+    }
+  } while (Desc->Length > 0 || Desc->Union.ContinuationPointer > 0);
+
+  WriteBackDataCacheRange (Desc, sizeof *Desc);
+
+  return EFI_SUCCESS;
+}
diff --git a/MdeModulePkg/Universal/CapsuleRuntimeDxe/CacheMaintenance.c b/MdeModulePkg/Universal/CapsuleRuntimeDxe/CacheMaintenance.c
new file mode 100644
index 000000000000..fb7504bb3e1d
--- /dev/null
+++ b/MdeModulePkg/Universal/CapsuleRuntimeDxe/CacheMaintenance.c
@@ -0,0 +1,39 @@
+/** @file
+  Create NULL function for capsule cache maintenance which is only needed
+  on ARM and AARCH64
+
+  Copyright (c) 2018, Linaro, Ltd. All rights reserved.<BR>
+
+  This program and the accompanying materials are licensed and made available
+  under the terms and conditions of the BSD License which accompanies this
+  distribution.  The full text of the license may be found at
+  http://opensource.org/licenses/bsd-license.php
+
+  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+
+**/
+
+#include <Uefi.h>
+
+/**
+  Writes Back a range of data cache lines covering a set of capsules in memory.
+
+  Writes Back the data cache lines specified by ScatterGatherList.
+
+  @param  ScatterGatherList Physical address of the data structure that
+                            describes a set of capsules in memory
+
+  @return EFI_SUCCESS       if the operation succeeded.
+          EFI_UNSUPPORTED   if cache maintenance cannot be performed at this
+                            time.
+
+**/
+EFI_STATUS
+EFIAPI
+CapsuleCacheWriteBack (
+  IN  EFI_PHYSICAL_ADDRESS    ScatterGatherList
+  )
+{
+  return EFI_SUCCESS;
+}
diff --git a/MdeModulePkg/Universal/CapsuleRuntimeDxe/CapsuleRuntimeDxe.inf b/MdeModulePkg/Universal/CapsuleRuntimeDxe/CapsuleRuntimeDxe.inf
index 9ab04ce1b301..3ceebc5d9646 100644
--- a/MdeModulePkg/Universal/CapsuleRuntimeDxe/CapsuleRuntimeDxe.inf
+++ b/MdeModulePkg/Universal/CapsuleRuntimeDxe/CapsuleRuntimeDxe.inf
@@ -27,17 +27,23 @@ [Defines]
 #
 # The following information is for reference only and not required by the build tools.
 #
-#  VALID_ARCHITECTURES           = IA32 X64 IPF EBC
+#  VALID_ARCHITECTURES           = IA32 X64 IPF EBC ARM AARCH64
 #
 
 [Sources]
   CapsuleService.c
 
-[Sources.Ia32, Sources.IPF, Sources.EBC, Sources.ARM, Sources.AARCH64]
+[Sources.Ia32, Sources.IPF, Sources.EBC]
   SaveLongModeContext.c
+  CacheMaintenance.c
 
 [Sources.X64]
   X64/SaveLongModeContext.c
+  CacheMaintenance.c
+
+[Sources.ARM, Sources.AARCH64]
+  SaveLongModeContext.c
+  Arm/CacheMaintenance.c
 
 [Packages]
   MdePkg/MdePkg.dec
@@ -59,6 +65,9 @@ [LibraryClasses.X64]
   UefiLib
   BaseMemoryLib
 
+[LibraryClasses.ARM, LibraryClasses.AARCH64]
+  CacheMaintenanceLib
+
 [Guids]
   ## SOMETIMES_PRODUCES   ## Variable:L"CapsuleUpdateData" # (Process across reset capsule image) for capsule updated data
   ## SOMETIMES_PRODUCES   ## Variable:L"CapsuleLongModeBuffer" # The long mode buffer used by IA32 Capsule PEIM to call X64 CapsuleCoalesce code to handle >4GB capsule blocks
diff --git a/MdeModulePkg/Universal/CapsuleRuntimeDxe/CapsuleService.c b/MdeModulePkg/Universal/CapsuleRuntimeDxe/CapsuleService.c
index 216798d1617e..ee8515adf62f 100644
--- a/MdeModulePkg/Universal/CapsuleRuntimeDxe/CapsuleService.c
+++ b/MdeModulePkg/Universal/CapsuleRuntimeDxe/CapsuleService.c
@@ -53,6 +53,25 @@ SaveLongModeContext (
   VOID
   );
 
+/**
+  Writes Back a range of data cache lines covering a set of capsules in memory.
+
+  Writes Back the data cache lines specified by ScatterGatherList.
+
+  @param  ScatterGatherList Physical address of the data structure that
+                            describes a set of capsules in memory
+
+  @return EFI_SUCCESS       if the operation succeeded.
+          EFI_UNSUPPORTED   if cache maintenance cannot be performed at this
+                            time.
+
+**/
+EFI_STATUS
+EFIAPI
+CapsuleCacheWriteBack (
+  IN  EFI_PHYSICAL_ADDRESS    ScatterGatherList
+  );
+
 /**
   Passes capsules to the firmware with both virtual and physical mapping. Depending on the intended
   consumption, the firmware may process the capsule immediately. If the payload should persist
@@ -214,6 +233,11 @@ UpdateCapsule (
       );
   }
 
+  Status = CapsuleCacheWriteBack (ScatterGatherList);
+  if (EFI_ERROR (Status)) {
+    return Status;
+  }
+
   //
   // ScatterGatherList is only referenced if the capsules are defined to persist across
   // system reset. Set its value into NV storage to let pre-boot driver to pick it up 
-- 
2.17.1