[PATCH] D15642: [asan] Use private aliases for global variables (LLVM part).

[Maxim Ostapenko via llvm-commits]

m.ostapenko removed rL LLVM as the repository for this revision.
m.ostapenko updated this revision to Diff 43455.
m.ostapenko added a comment.

Updating the diff. Don't export _asan_genXXX symbols in -fvisibility=hidden case.


http://reviews.llvm.org/D15642

Files:
  lib/Transforms/Instrumentation/AddressSanitizer.cpp

Index: lib/Transforms/Instrumentation/AddressSanitizer.cpp
===================================================================
--- lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -1307,6 +1307,7 @@
 
   // A global is described by a structure
   //   size_t beg;
+  //   size_t odr_indicator;
   //   size_t size;
   //   size_t size_with_redzone;
   //   const char *name;
@@ -1316,7 +1317,7 @@
   // We initialize an array of such structures and pass it to a run-time call.
   StructType *GlobalStructTy =
       StructType::get(IntptrTy, IntptrTy, IntptrTy, IntptrTy, IntptrTy,
-                      IntptrTy, IntptrTy, nullptr);
+                      IntptrTy, IntptrTy, IntptrTy, nullptr);
   SmallVector<Constant *, 16> Initializers(n);
 
   bool HasDynamicallyInitializedGlobals = false;
@@ -1332,12 +1333,14 @@
     GlobalVariable *G = GlobalsToChange[i];
 
     auto MD = GlobalsMD.get(G);
+    StringRef NameForGlobal =  G->getName();
     // Create string holding the global name (use global name from metadata
     // if it's available, otherwise just write the name of global variable).
     GlobalVariable *Name = createPrivateGlobalForString(
-        M, MD.Name.empty() ? G->getName() : MD.Name,
+        M, MD.Name.empty() ? NameForGlobal : MD.Name,
         /*AllowMerging*/ true);
 
+
     PointerType *PtrTy = cast<PointerType>(G->getType());
     Type *Ty = PtrTy->getElementType();
     uint64_t SizeInBytes = DL.getTypeAllocSize(Ty);
@@ -1384,8 +1387,24 @@
       SourceLoc = ConstantInt::get(IntptrTy, 0);
     }
 
+    // Create local alias for NewGlobal to avoid crash on ODR between
+    // instrumented and non-instrumented libraries.
+    auto *GA = GlobalAlias::create(
+        GlobalValue::InternalLinkage, NameForGlobal + M.getName(), NewGlobal);
+
+    // With local aliases, we need to provide another externally visible symbol
+    // _asan_genXXX to detect ODR violation. However, if we hide global symbol
+    // via -fvisibility=hidden, use PrivateLinkage to avoid false positives.
+    if (NewGlobal->hasHiddenVisibility()) Linkage = GlobalValue::PrivateLinkage;
+    auto *ODRIndicatorSym =
+        new GlobalVariable(M, IRB.getInt8Ty(), false, Linkage,
+                           Constant::getNullValue(IRB.getInt8Ty()),
+                           kAsanGenPrefix + NameForGlobal, nullptr,
+                           NewGlobal->getThreadLocalMode());
+
     Initializers[i] = ConstantStruct::get(
-        GlobalStructTy, ConstantExpr::getPointerCast(NewGlobal, IntptrTy),
+        GlobalStructTy, ConstantExpr::getPointerCast(GA, IntptrTy),
+        ConstantExpr::getPointerCast(ODRIndicatorSym, IntptrTy),
         ConstantInt::get(IntptrTy, SizeInBytes),
         ConstantInt::get(IntptrTy, SizeInBytes + RightRedzoneSize),
         ConstantExpr::getPointerCast(Name, IntptrTy),


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D15642.43455.patch
Type: text/x-patch
Size: 2892 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20151222/d1efe008/attachment.bin>