[compiler-rt] 849da03 - [scudo] Shuffle the regions

[Chia-hung Duan via llvm-commits]

Author: Chia-hung Duan
Date: 2023-03-08T22:58:08Z
New Revision: 849da03202530601c1c7d6a284e905b1ba6a4485

URL: https://github.com/llvm/llvm-project/commit/849da03202530601c1c7d6a284e905b1ba6a4485
DIFF: https://github.com/llvm/llvm-project/commit/849da03202530601c1c7d6a284e905b1ba6a4485.diff

LOG: [scudo] Shuffle the regions

Shuffle the regions' base address so that the layout of all regions is
less predictable.

Reviewed By: cferris, cryptoad

Differential Revision: https://reviews.llvm.org/D145407

Added: 
    

Modified: 
    compiler-rt/lib/scudo/standalone/primary64.h

Removed: 
    


################################################################################
diff  --git a/compiler-rt/lib/scudo/standalone/primary64.h b/compiler-rt/lib/scudo/standalone/primary64.h
index 3df8749898484..7868111bfc5c2 100644
--- a/compiler-rt/lib/scudo/standalone/primary64.h
+++ b/compiler-rt/lib/scudo/standalone/primary64.h
@@ -65,6 +65,7 @@ template <typename Config> class SizeClassAllocator64 {
   void init(s32 ReleaseToOsInterval) NO_THREAD_SAFETY_ANALYSIS {
     DCHECK(isAligned(reinterpret_cast<uptr>(this), alignof(ThisT)));
     DCHECK_EQ(PrimaryBase, 0U);
+
     // Reserve the space required for the Primary.
     PrimaryBase = reinterpret_cast<uptr>(map(
         nullptr, PrimarySize, "scudo:primary_reserve", MAP_NOACCESS, &Data));
@@ -78,13 +79,15 @@ template <typename Config> class SizeClassAllocator64 {
       RegionInfo *Region = getRegionInfo(I);
       // The actual start of a region is offset by a random number of pages
       // when PrimaryEnableRandomOffset is set.
-      Region->RegionBeg = getRegionBaseByClassId(I) +
+      Region->RegionBeg = (PrimaryBase + (I << Config::PrimaryRegionSizeLog)) +
                           (Config::PrimaryEnableRandomOffset
                                ? ((getRandomModN(&Seed, 16) + 1) * PageSize)
                                : 0);
       Region->RandState = getRandomU32(&Seed);
       Region->ReleaseInfo.LastReleaseAtNs = Time;
     }
+    shuffle(RegionInfoArray, NumClasses, &Seed);
+
     setOption(Option::ReleaseInterval, static_cast<sptr>(ReleaseToOsInterval));
   }
 
@@ -420,8 +423,10 @@ template <typename Config> class SizeClassAllocator64 {
     return &RegionInfoArray[ClassId];
   }
 
-  uptr getRegionBaseByClassId(uptr ClassId) const {
-    return PrimaryBase + (ClassId << Config::PrimaryRegionSizeLog);
+  uptr getRegionBaseByClassId(uptr ClassId) {
+    return roundDown(getRegionInfo(ClassId)->RegionBeg - PrimaryBase,
+                     RegionSize) +
+           PrimaryBase;
   }
 
   static CompactPtrT compactPtrInternal(uptr Base, uptr Ptr) {