XOR the frame pointer with the stack cookie when protecting the stack

Summary: This strengthens the guard and matches MSVC.

Reviewers: hans, etienneb

Subscribers: hiraditya, JDevlieghere, vlad.tsyrklevich, llvm-commits

Differential Revision: https://reviews.llvm.org/D40622

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@319490 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 11 insertions, 0 deletions

diff --git a/include/llvm/CodeGen/TargetLowering.h b/include/llvm/CodeGen/TargetLowering.h
index 4210f58ddb0..f9a61b8bf1a 100644
--- a/include/llvm/CodeGen/TargetLowering.h
+++ b/include/llvm/CodeGen/TargetLowering.h
@@ -1360,6 +1360,12 @@ public:
   /// getIRStackGuard returns nullptr.
   virtual Value *getSDagStackGuard(const Module &M) const;
 
+  /// If this function returns true, stack protection checks should XOR the
+  /// frame pointer (or whichever pointer is used to address locals) into the
+  /// stack guard value before checking it. getIRStackGuard must return nullptr
+  /// if this returns true.
+  virtual bool useStackGuardXorFP() const { return false; }
+
   /// If the target has a standard stack protection check function that
   /// performs validation and error handling, returns the function. Otherwise,
   /// returns nullptr. Must be previously inserted by insertSSPDeclarations.
@@ -3487,6 +3493,11 @@ public:
     return false;
   }
 
+  virtual SDValue emitStackGuardXorFP(SelectionDAG &DAG, SDValue Val,
+                                      const SDLoc &DL) const {
+    llvm_unreachable("not implemented for this target");
+  }
+
   /// Lower TLS global address SDNode for target independent emulated TLS model.
   virtual SDValue LowerToTLSEmulatedModel(const GlobalAddressSDNode *GA,
                                           SelectionDAG &DAG) const;