[PATCH v3 08/16] ArmPkg/ArmMmuLib: Reuse XIP MMU routines when splitting entries

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

In order to reduce the likelihood that we will need to rely on the logic
that disables and re-enables the MMU for updating a page table entry
safely, expose the XIP version of the helper routine via a HOB and use
it instead of the one that is copied into DRAM. Since the XIP copy is
already clean to the PoC, and will never end up getting unmapped during
a block entry split, we can use it safely without any cache maintenance,
and without running the risk of pulling the rug from under our feet when
updating an entry by going through an invalid mapping.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 ArmPkg/ArmPkg.dec                                          |  2 ++
 ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c           | 27 ++++++++++++--------
 ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuPeiLibConstructor.c | 17 ++++++++++++
 ArmPkg/Library/ArmMmuLib/ArmMmuBaseLib.inf                 |  4 +++
 ArmPkg/Library/ArmMmuLib/ArmMmuPeiLib.inf                  |  4 +++
 5 files changed, 44 insertions(+), 10 deletions(-)

diff --git a/ArmPkg/ArmPkg.dec b/ArmPkg/ArmPkg.dec
index 9da1bbc9f216..cfb6fe602485 100644
--- a/ArmPkg/ArmPkg.dec
+++ b/ArmPkg/ArmPkg.dec
@@ -99,6 +99,8 @@ [Guids.common]
   # Include/Guid/ArmMpCoreInfo.h
   gArmMpCoreInfoGuid = { 0xa4ee0728, 0xe5d7, 0x4ac5,  {0xb2, 0x1e, 0x65, 0x8e, 0xd8, 0x57, 0xe8, 0x34} }
 
+  gArmMmuReplaceLiveTranslationEntryFuncGuid = { 0xa8b50ff3, 0x08ec, 0x4dd3, {0xbf, 0x04, 0x28, 0xbf, 0x71, 0x75, 0xc7, 0x4a} }
+
 [Protocols.common]
   ## Arm System Control and Management Interface(SCMI) Base protocol
   ## ArmPkg/Include/Protocol/ArmScmiBaseProtocol.h
diff --git a/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c b/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c
index ae59e9a7d04e..764c7d362e2e 100644
--- a/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c
+++ b/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c
@@ -10,6 +10,7 @@
 **/
 
 #include <Uefi.h>
+#include <Pi/PiMultiPhase.h>
 #include <Chipset/AArch64.h>
 #include <Library/BaseMemoryLib.h>
 #include <Library/CacheMaintenanceLib.h>
@@ -120,14 +121,14 @@ ReplaceTableEntry (
     // use an ordinary break before make. Otherwise, we will need to
     // temporarily disable the MMU.
     DisableMmu = FALSE;
-    if ((((RegionStart ^ (UINTN)ArmReplaceLiveTranslationEntry) & ~BlockMask) == 0) ||
+    if ((((RegionStart ^ (UINTN)mReplaceLiveEntryFunc) & ~BlockMask) == 0) ||
         (((RegionStart ^ (UINTN)Entry) & ~BlockMask) == 0))
     {
       DisableMmu = TRUE;
       DEBUG ((DEBUG_WARN, "%a: splitting block entry with MMU disabled\n", __FUNCTION__));
     }
 
-    ArmReplaceLiveTranslationEntry (Entry, Value, RegionStart, DisableMmu);
+    mReplaceLiveEntryFunc (Entry, Value, RegionStart, DisableMmu);
   }
 }
 
@@ -747,15 +748,21 @@ ArmMmuBaseLibConstructor (
   )
 {
   extern UINT32  ArmReplaceLiveTranslationEntrySize;
+  VOID           *Hob;
 
-  //
-  // The ArmReplaceLiveTranslationEntry () helper function may be invoked
-  // with the MMU off so we have to ensure that it gets cleaned to the PoC
-  //
-  WriteBackDataCacheRange (
-    (VOID *)(UINTN)ArmReplaceLiveTranslationEntry,
-    ArmReplaceLiveTranslationEntrySize
-    );
+  Hob = GetFirstGuidHob (&gArmMmuReplaceLiveTranslationEntryFuncGuid);
+  if (Hob != NULL) {
+    mReplaceLiveEntryFunc = *(VOID **)GET_GUID_HOB_DATA (Hob);
+  } else {
+    //
+    // The ArmReplaceLiveTranslationEntry () helper function may be invoked
+    // with the MMU off so we have to ensure that it gets cleaned to the PoC
+    //
+    WriteBackDataCacheRange (
+      (VOID *)(UINTN)ArmReplaceLiveTranslationEntry,
+      ArmReplaceLiveTranslationEntrySize
+      );
+  }
 
   return RETURN_SUCCESS;
 }
diff --git a/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuPeiLibConstructor.c b/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuPeiLibConstructor.c
index caace2c17cdc..5f50a605a338 100644
--- a/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuPeiLibConstructor.c
+++ b/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuPeiLibConstructor.c
@@ -12,6 +12,7 @@
 #include <Library/ArmMmuLib.h>
 #include <Library/CacheMaintenanceLib.h>
 #include <Library/DebugLib.h>
+#include <Library/HobLib.h>
 
 EFI_STATUS
 EFIAPI
@@ -21,6 +22,8 @@ ArmMmuPeiLibConstructor (
   )
 {
   extern UINT32  ArmReplaceLiveTranslationEntrySize;
+  VOID           *ArmReplaceLiveTranslationEntryFunc;
+  VOID           *Hob;
 
   EFI_FV_FILE_INFO  FileInfo;
   EFI_STATUS        Status;
@@ -42,6 +45,20 @@ ArmMmuPeiLibConstructor (
        (UINTN)ArmReplaceLiveTranslationEntry + ArmReplaceLiveTranslationEntrySize))
   {
     DEBUG ((DEBUG_INFO, "ArmMmuLib: skipping cache maintenance on XIP PEIM\n"));
+
+    //
+    // Expose the XIP version of the ArmReplaceLiveTranslationEntry() routine
+    // via a HOB so we can fall back to it later when we need to split block
+    // mappings in a way that adheres to break-before-make requirements.
+    //
+    ArmReplaceLiveTranslationEntryFunc = ArmReplaceLiveTranslationEntry;
+
+    Hob = BuildGuidDataHob (
+            &gArmMmuReplaceLiveTranslationEntryFuncGuid,
+            &ArmReplaceLiveTranslationEntryFunc,
+            sizeof ArmReplaceLiveTranslationEntryFunc
+            );
+    ASSERT (Hob != NULL);
   } else {
     DEBUG ((DEBUG_INFO, "ArmMmuLib: performing cache maintenance on shadowed PEIM\n"));
     //
diff --git a/ArmPkg/Library/ArmMmuLib/ArmMmuBaseLib.inf b/ArmPkg/Library/ArmMmuLib/ArmMmuBaseLib.inf
index 3d78e7dabf47..57cb71f90ee3 100644
--- a/ArmPkg/Library/ArmMmuLib/ArmMmuBaseLib.inf
+++ b/ArmPkg/Library/ArmMmuLib/ArmMmuBaseLib.inf
@@ -36,7 +36,11 @@ [Packages]
 [LibraryClasses]
   ArmLib
   CacheMaintenanceLib
+  HobLib
   MemoryAllocationLib
 
+[Guids]
+  gArmMmuReplaceLiveTranslationEntryFuncGuid
+
 [Pcd.ARM]
   gArmTokenSpaceGuid.PcdNormalMemoryNonshareableOverride
diff --git a/ArmPkg/Library/ArmMmuLib/ArmMmuPeiLib.inf b/ArmPkg/Library/ArmMmuLib/ArmMmuPeiLib.inf
index ce9674ea99ef..02f874a1a994 100644
--- a/ArmPkg/Library/ArmMmuLib/ArmMmuPeiLib.inf
+++ b/ArmPkg/Library/ArmMmuLib/ArmMmuPeiLib.inf
@@ -29,4 +29,8 @@ [Packages]
 [LibraryClasses]
   ArmLib
   CacheMaintenanceLib
+  HobLib
   MemoryAllocationLib
+
+[Guids]
+  gArmMmuReplaceLiveTranslationEntryFuncGuid
-- 
2.35.1