[edk2] [PATCH v3 2/3] MdeModulePkg/PiSmmCore: fix bits operation error on a boundary condition

[Jian J Wang]

If given address is on 64K boundary and the requested bit number is 64,
all SetBits(), ClearBits() and GetBits() will encounter ASSERT problem
in trying to do a 64 bits of shift, which is not allowed by LShift() and
RShift(). This patch tries to fix this issue by turning bits operation
into whole integer operation in such situation.

Cc: Star Zeng <star.z...@intel.com>
Cc: Eric Dong <eric.d...@intel.com>
Cc: Jiewen Yao <jiewen....@intel.com>
Cc: Ruiyu Ni <ruiyu...@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jian J Wang <jian.j.w...@intel.com>
---
 MdeModulePkg/Core/PiSmmCore/HeapGuard.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/MdeModulePkg/Core/PiSmmCore/HeapGuard.c 
b/MdeModulePkg/Core/PiSmmCore/HeapGuard.c
index 923af93de2..f9657f9baa 100644
--- a/MdeModulePkg/Core/PiSmmCore/HeapGuard.c
+++ b/MdeModulePkg/Core/PiSmmCore/HeapGuard.c
@@ -73,7 +73,7 @@ SetBits (
   StartBit  = (UINTN)GUARDED_HEAP_MAP_ENTRY_BIT_INDEX (Address);
   EndBit    = (StartBit + BitNumber - 1) % GUARDED_HEAP_MAP_ENTRY_BITS;
 
-  if ((StartBit + BitNumber) > GUARDED_HEAP_MAP_ENTRY_BITS) {
+  if ((StartBit + BitNumber) >= GUARDED_HEAP_MAP_ENTRY_BITS) {
     Msbs    = (GUARDED_HEAP_MAP_ENTRY_BITS - StartBit) %
               GUARDED_HEAP_MAP_ENTRY_BITS;
     Lsbs    = (EndBit + 1) % GUARDED_HEAP_MAP_ENTRY_BITS;
@@ -126,7 +126,7 @@ ClearBits (
   StartBit  = (UINTN)GUARDED_HEAP_MAP_ENTRY_BIT_INDEX (Address);
   EndBit    = (StartBit + BitNumber - 1) % GUARDED_HEAP_MAP_ENTRY_BITS;
 
-  if ((StartBit + BitNumber) > GUARDED_HEAP_MAP_ENTRY_BITS) {
+  if ((StartBit + BitNumber) >= GUARDED_HEAP_MAP_ENTRY_BITS) {
     Msbs    = (GUARDED_HEAP_MAP_ENTRY_BITS - StartBit) %
               GUARDED_HEAP_MAP_ENTRY_BITS;
     Lsbs    = (EndBit + 1) % GUARDED_HEAP_MAP_ENTRY_BITS;
@@ -191,10 +191,14 @@ GetBits (
     Lsbs = 0;
   }
 
-  Result    = RShiftU64 ((*BitMap), StartBit) & (LShiftU64 (1, Msbs) - 1);
-  if (Lsbs > 0) {
-    BitMap  += 1;
-    Result  |= LShiftU64 ((*BitMap) & (LShiftU64 (1, Lsbs) - 1), Msbs);
+  if (StartBit == 0 && BitNumber == GUARDED_HEAP_MAP_ENTRY_BITS) {
+    Result = *BitMap;
+  } else {
+    Result    = RShiftU64((*BitMap), StartBit) & (LShiftU64(1, Msbs) - 1);
+    if (Lsbs > 0) {
+      BitMap  += 1;
+      Result  |= LShiftU64 ((*BitMap) & (LShiftU64 (1, Lsbs) - 1), Msbs);
+    }
   }
 
   return Result;
-- 
2.16.2.windows.1

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