[PATCH] D81367: [ASan][NFC] Refactor redzone size calculation

[Marco Elver via Phabricator via llvm-commits]

melver created this revision.
melver added a reviewer: glider.
Herald added subscribers: llvm-commits, hiraditya.
Herald added a project: LLVM.

Refactor redzone size calculation. This will simplify changing the
redzone size calculation in future.

Note that AddressSanitizer.cpp violaties the latest LLVM style guide in
various ways due to capitalized function names. Only code related to the
change here was changed to adhere to the style guide.

No functional change intended.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D81367

Files:
  llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp


Index: llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
===================================================================
--- llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -537,7 +537,7 @@
   return Mapping;
 }
 
-static size_t RedzoneSizeForScale(int MappingScale) {
+static uint64_t getRedzoneSizeForScale(int MappingScale) {
   // Redzone used for stack and globals is at least 32 bytes.
   // For scales 6 and 7, the redzone has to be 64 and 128 bytes respectively.
   return std::max(32U, 1U << MappingScale);
@@ -797,9 +797,10 @@
   StringRef getGlobalMetadataSection() const;
   void poisonOneInitializer(Function &GlobalInit, GlobalValue *ModuleName);
   void createInitializerPoisonCalls(Module &M, GlobalValue *ModuleName);
-  size_t MinRedzoneSizeForGlobal() const {
-    return RedzoneSizeForScale(Mapping.Scale);
+  uint64_t getMinRedzoneSizeForGlobal() const {
+    return getRedzoneSizeForScale(Mapping.Scale);
   }
+  uint64_t getRedzoneSizeForGlobal(uint64_t SizeInBytes) const;
   int GetAsanVersion(const Module &M) const;
 
   const GlobalsMetadata &GlobalsMD;
@@ -1808,7 +1809,7 @@
   //   - Need to poison all copies, not just the main thread's one.
   if (G->isThreadLocal()) return false;
   // For now, just ignore this Global if the alignment is large.
-  if (G->getAlignment() > MinRedzoneSizeForGlobal()) return false;
+  if (G->getAlignment() > getMinRedzoneSizeForGlobal()) return false;
 
   // For non-COFF targets, only instrument globals known to be defined by this
   // TU.
@@ -2271,7 +2272,6 @@
       M, M.getModuleIdentifier(), /*AllowMerging*/ false, kAsanGenPrefix);
 
   for (size_t i = 0; i < n; i++) {
-    static const uint64_t kMaxGlobalRedzone = 1 << 18;
     GlobalVariable *G = GlobalsToChange[i];
 
     // FIXME: Metadata should be attched directly to the global directly instead
@@ -2285,16 +2285,8 @@
         /*AllowMerging*/ true, kAsanGenPrefix);
 
     Type *Ty = G->getValueType();
-    uint64_t SizeInBytes = DL.getTypeAllocSize(Ty);
-    uint64_t MinRZ = MinRedzoneSizeForGlobal();
-    // MinRZ <= RZ <= kMaxGlobalRedzone
-    // and trying to make RZ to be ~ 1/4 of SizeInBytes.
-    uint64_t RZ = std::max(
-        MinRZ, std::min(kMaxGlobalRedzone, (SizeInBytes / MinRZ / 4) * MinRZ));
-    uint64_t RightRedzoneSize = RZ;
-    // Round up to MinRZ
-    if (SizeInBytes % MinRZ) RightRedzoneSize += MinRZ - (SizeInBytes % MinRZ);
-    assert(((RightRedzoneSize + SizeInBytes) % MinRZ) == 0);
+    const uint64_t SizeInBytes = DL.getTypeAllocSize(Ty);
+    const uint64_t RightRedzoneSize = getRedzoneSizeForGlobal(SizeInBytes);
     Type *RightRedZoneTy = ArrayType::get(IRB.getInt8Ty(), RightRedzoneSize);
 
     StructType *NewTy = StructType::get(Ty, RightRedZoneTy);
@@ -2310,7 +2302,7 @@
                            "", G, G->getThreadLocalMode());
     NewGlobal->copyAttributesFrom(G);
     NewGlobal->setComdat(G->getComdat());
-    NewGlobal->setAlignment(MaybeAlign(MinRZ));
+    NewGlobal->setAlignment(MaybeAlign(getMinRedzoneSizeForGlobal()));
     // Don't fold globals with redzones. ODR violation detector and redzone
     // poisoning implicitly creates a dependence on the global's address, so it
     // is no longer valid for it to be marked unnamed_addr.
@@ -2432,6 +2424,23 @@
   return true;
 }
 
+uint64_t
+ModuleAddressSanitizer::getRedzoneSizeForGlobal(uint64_t SizeInBytes) const {
+  constexpr uint64_t kMaxRZ = 1 << 18;
+  const uint64_t MinRZ = getMinRedzoneSizeForGlobal();
+
+  // Calculate RZ, where MinRZ <= RZ <= MaxRZ, and RZ ~ 1/4 * SizeInBytes.
+  uint64_t RZ =
+      std::max(MinRZ, std::min(kMaxRZ, (SizeInBytes / MinRZ / 4) * MinRZ));
+
+  // Round up to multiple of MinRZ.
+  if (SizeInBytes % MinRZ)
+    RZ += MinRZ - (SizeInBytes % MinRZ);
+  assert((RZ + SizeInBytes) % MinRZ == 0);
+
+  return RZ;
+}
+
 int ModuleAddressSanitizer::GetAsanVersion(const Module &M) const {
   int LongSize = M.getDataLayout().getPointerSizeInBits();
   bool isAndroid = Triple(M.getTargetTriple()).isAndroid();


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