[safestack] Fast access to the unsafe stack pointer on AArch64/Android.

[oota-llvm.git] / lib / Transforms / Instrumentation / SafeStack.cpp

diff --git a/lib/Transforms/Instrumentation/SafeStack.cpp b/lib/Transforms/Instrumentation/SafeStack.cpp
index 96ef639138af3bdff2b2e8bd236d90aeec5b7108..ea5b1ee11d7ceebe7bf5fb1e3b520635111ef93b 100644 (file)
--- a/lib/Transforms/Instrumentation/SafeStack.cpp
+++ b/lib/Transforms/Instrumentation/SafeStack.cpp
@@ -46,9 +46,6 @@ using namespace llvm;
 
 #define DEBUG_TYPE "safestack"
 
-static const char *const kUnsafeStackPtrVar = "__safestack_unsafe_stack_ptr";
-static const char *const kUnsafeStackPtrAddrFn = "__safestack_pointer_address";
-
 namespace llvm {
 
 STATISTIC(NumFunctions, "Total number of functions");
@@ -182,10 +179,6 @@ class SafeStack : public FunctionPass {
   /// might expect to appear on the stack on most common targets.
   enum { StackAlignment = 16 };
 
-  /// \brief Build a constant representing a pointer to the unsafe stack
-  /// pointer.
-  Value *getOrCreateUnsafeStackPtr(IRBuilder<> &IRB, Function &F);
-
   /// \brief Find all static allocas, dynamic allocas, return instructions and
   /// stack restore points (exception unwind blocks and setjmp calls) in the
   /// given function and append them to the respective vectors.
@@ -247,54 +240,6 @@ public:
   bool runOnFunction(Function &F) override;
 }; // class SafeStack
 
-Value *SafeStack::getOrCreateUnsafeStackPtr(IRBuilder<> &IRB, Function &F) {
-  Module &M = *F.getParent();
-  Triple TargetTriple(M.getTargetTriple());
-
-  unsigned Offset;
-  unsigned AddressSpace;
-  // Check if the target keeps the unsafe stack pointer at a fixed offset.
-  if (TLI && TLI->getSafeStackPointerLocation(AddressSpace, Offset)) {
-    Constant *OffsetVal =
-        ConstantInt::get(Type::getInt32Ty(F.getContext()), Offset);
-    return ConstantExpr::getIntToPtr(OffsetVal,
-                                     StackPtrTy->getPointerTo(AddressSpace));
-  }
-
-  // Android provides a libc function that returns the stack pointer address.
-  if (TargetTriple.isAndroid()) {
-    Value *Fn = M.getOrInsertFunction(kUnsafeStackPtrAddrFn,
-                                      StackPtrTy->getPointerTo(0), nullptr);
-    return IRB.CreateCall(Fn);
-  } else {
-    // Otherwise, declare a thread-local variable with a magic name.
-    auto UnsafeStackPtr =
-        dyn_cast_or_null<GlobalVariable>(M.getNamedValue(kUnsafeStackPtrVar));
-
-    if (!UnsafeStackPtr) {
-      // The global variable is not defined yet, define it ourselves.
-      // We use the initial-exec TLS model because we do not support the
-      // variable living anywhere other than in the main executable.
-      UnsafeStackPtr = new GlobalVariable(
-          /*Module=*/M, /*Type=*/StackPtrTy,
-          /*isConstant=*/false, /*Linkage=*/GlobalValue::ExternalLinkage,
-          /*Initializer=*/nullptr, /*Name=*/kUnsafeStackPtrVar,
-          /*InsertBefore=*/nullptr,
-          /*ThreadLocalMode=*/GlobalValue::InitialExecTLSModel);
-    } else {
-      // The variable exists, check its type and attributes.
-      if (UnsafeStackPtr->getValueType() != StackPtrTy) {
-        report_fatal_error(Twine(kUnsafeStackPtrVar) + " must have void* type");
-      }
-
-      if (!UnsafeStackPtr->isThreadLocal()) {
-        report_fatal_error(Twine(kUnsafeStackPtrVar) + " must be thread-local");
-      }
-    }
-    return UnsafeStackPtr;
-  }
-}
-
 void SafeStack::findInsts(Function &F,
                           SmallVectorImpl<AllocaInst *> &StaticAllocas,
                           SmallVectorImpl<AllocaInst *> &DynamicAllocas,
@@ -597,7 +542,7 @@ bool SafeStack::runOnFunction(Function &F) {
     ++NumUnsafeStackRestorePointsFunctions;
 
   IRBuilder<> IRB(&F.front(), F.begin()->getFirstInsertionPt());
-  UnsafeStackPtr = getOrCreateUnsafeStackPtr(IRB, F);
+  UnsafeStackPtr = TLI->getSafeStackPointerLocation(IRB);
 
   // The top of the unsafe stack after all unsafe static allocas are allocated.
   Value *StaticTop = moveStaticAllocasToUnsafeStack(IRB, F, StaticAllocas, Returns);