[edk2-devel] [Patch V6 04/22] UefiCpuPkg/CpuPageTableLib: Fix the non-1:1 mapping issue

[duntan]

In previous code logic, when splitting a leaf parent entry to
smaller granularity child page table, if the parent entry
Attribute&Mask(without PageTableBaseAddress field) is equal to the
input attribute&mask(without PageTableBaseAddress field), the split
process won't happen. This may lead to failure in non-1:1 mapping.

For example, there is a page table in which [0, 1G] is mapped(Lv4[0]
,Lv3[0,0], a non-leaf level4 entry and a leaf level3 entry). And we
want to remap [0, 2M] linear address range to [1G, 1G + 2M] with the
same attibute. The expected behaviour should be: split Lv3[0,0]
entry into 512 level2 entries and remap the first level2 entry to
cover [0, 2M]. But the split won't happen in previous code since
PageTableBaseAddress of input Attribute is not checked.

So, when checking if a leaf parent entry needs to be splitted, we
should also check if PageTableBaseAddress calculated by parent entry
is equal to the value caculated by input attribute.

Signed-off-by: Dun Tan <dun.tan at intel.com>
Cc: Eric Dong <eric.dong at intel.com>
Cc: Ray Ni <ray.ni at intel.com>
Cc: Rahul Kumar <rahul1.kumar at intel.com>
Tested-by: Gerd Hoffmann <kraxel at redhat.com>
Acked-by: Gerd Hoffmann <kraxel at redhat.com>
---
 UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c b/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
index 127b65183f..b94ef07c56 100644
--- a/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
+++ b/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
@@ -274,6 +274,8 @@ PageTableLibMapInLevel (
   IA32_MAP_ATTRIBUTE  ChildMask;
   IA32_MAP_ATTRIBUTE  CurrentMask;
   IA32_MAP_ATTRIBUTE  LocalParentAttribute;
+  UINT64              PhysicalAddrInEntry;
+  UINT64              PhysicalAddrInAttr;
 
   ASSERT (Level != 0);
   ASSERT ((Attribute != NULL) && (Mask != NULL));
@@ -341,7 +343,15 @@ PageTableLibMapInLevel (
       // This function is called when the memory length is less than the region length of the parent level.
       // No need to split the page when the attributes equal.
       //
-      return RETURN_SUCCESS;
+      if (Mask->Bits.PageTableBaseAddress == 0) {
+        return RETURN_SUCCESS;
+      }
+
+      PhysicalAddrInEntry = IA32_MAP_ATTRIBUTE_PAGE_TABLE_BASE_ADDRESS (&PleBAttribute) + MultU64x32 (RegionLength, (UINT32)PagingEntryIndex);
+      PhysicalAddrInAttr  = (IA32_MAP_ATTRIBUTE_PAGE_TABLE_BASE_ADDRESS (Attribute) + Offset) & (~RegionMask);
+      if (PhysicalAddrInEntry == PhysicalAddrInAttr) {
+        return RETURN_SUCCESS;
+      }
     }
 
     ASSERT (Buffer == NULL || *BufferSize >= SIZE_4KB);
-- 
2.31.1.windows.1



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