diff --git a/compiler-rt/test/dfsan/event_callbacks.c b/compiler-rt/test/dfsan/event_callbacks.c
new file mode 100644
--- /dev/null
+++ b/compiler-rt/test/dfsan/event_callbacks.c
@@ -0,0 +1,67 @@
+// RUN: %clang_dfsan -fno-sanitize=dataflow -fPIE -DCALLBACKS -c %s -o %t-callbacks.o
+// RUN: %clang_dfsan -mllvm -dfsan-event-callbacks %s %t-callbacks.o -o %t
+// RUN: %run %t 2>&1 | FileCheck %s
+
+// Tests that callbacks are inserted for store events when
+// -dfsan-event-callbacks is specified.
+
+#include <assert.h>
+#include <sanitizer/dfsan_interface.h>
+#include <stdio.h>
+
+#ifdef CALLBACKS
+// Compile this code without DFSan to avoid recursive instrumentation.
+
+extern dfsan_label LabelI;
+extern dfsan_label LabelJ;
+extern dfsan_label LabelIJ;
+
+void __dfsan_store_callback(dfsan_label Label) {
+  if (!Label)
+    return;
+
+  static int Count = 0;
+  switch (Count++) {
+  case 0:
+    assert(Label == LabelI);
+    break;
+  case 1:
+    assert(Label == LabelJ);
+    break;
+  case 2:
+    assert(Label == LabelIJ);
+    break;
+  default:
+    assert(0);
+  }
+
+  // CHECK: Label 1 stored to memory
+  // CHECK: Label 2 stored to memory
+  // CHECK: Label 3 stored to memory
+  fprintf(stderr, "Label %u stored to memory\n", Label);
+}
+
+#else
+// Compile this code with DFSan and -dfsan-event-callbacks to insert the
+// callbacks.
+
+dfsan_label LabelI;
+dfsan_label LabelJ;
+dfsan_label LabelIJ;
+
+int main(void) {
+  int I = 1, J = 2;
+  LabelI = dfsan_create_label("I", 0);
+  dfsan_set_label(LabelI, &I, sizeof(I));
+  LabelJ = dfsan_create_label("J", 0);
+  dfsan_set_label(LabelJ, &J, sizeof(J));
+  LabelIJ = dfsan_union(LabelI, LabelJ);
+
+  volatile int Sink = I;
+  Sink = J;
+  Sink += I;
+
+  return 0;
+}
+
+#endif // #ifdef CALLBACKS
diff --git a/llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
--- a/llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
@@ -162,6 +162,17 @@
              "load or return with a nonzero label"),
     cl::Hidden);
 
+// Experimental feature that inserts callbacks for certain data events.
+// Currently callbacks are only inserted for stores.
+//
+// If this flag is set to true, the user must provide definitions for the
+// following callback functions:
+//   void __dfsan_store_callback(dfsan_label Label);
+static cl::opt<bool> ClEventCallbacks(
+    "dfsan-event-callbacks",
+    cl::desc("Insert calls to __dfsan_*_callback functions on data events."),
+    cl::Hidden, cl::init(false));
+
 static StringRef GetGlobalTypeString(const GlobalValue &G) {
   // Types of GlobalVariables are always pointer types.
   Type *GType = G.getValueType();
@@ -345,6 +356,7 @@
   FunctionType *DFSanSetLabelFnTy;
   FunctionType *DFSanNonzeroLabelFnTy;
   FunctionType *DFSanVarargWrapperFnTy;
+  FunctionType *DFSanStoreCallbackFnTy;
   FunctionCallee DFSanUnionFn;
   FunctionCallee DFSanCheckedUnionFn;
   FunctionCallee DFSanUnionLoadFn;
@@ -352,6 +364,7 @@
   FunctionCallee DFSanSetLabelFn;
   FunctionCallee DFSanNonzeroLabelFn;
   FunctionCallee DFSanVarargWrapperFn;
+  FunctionCallee DFSanStoreCallbackFn;
   MDNode *ColdCallWeights;
   DFSanABIList ABIList;
   DenseMap<Value *, Function *> UnwrappedFnMap;
@@ -583,6 +596,8 @@
       Type::getVoidTy(*Ctx), None, /*isVarArg=*/false);
   DFSanVarargWrapperFnTy = FunctionType::get(
       Type::getVoidTy(*Ctx), Type::getInt8PtrTy(*Ctx), /*isVarArg=*/false);
+  DFSanStoreCallbackFnTy =
+      FunctionType::get(Type::getVoidTy(*Ctx), ShadowTy, /*isVarArg=*/false);
 
   if (GetArgTLSPtr) {
     Type *ArgTLSTy = ArrayType::get(ShadowTy, 64);
@@ -783,6 +798,9 @@
   DFSanVarargWrapperFn = Mod->getOrInsertFunction("__dfsan_vararg_wrapper",
                                                   DFSanVarargWrapperFnTy);
 
+  DFSanStoreCallbackFn = Mod->getOrInsertFunction("__dfsan_store_callback",
+                                                  DFSanStoreCallbackFnTy);
+
   std::vector<Function *> FnsToInstrument;
   SmallPtrSet<Function *, 2> FnsWithNativeABI;
   for (Function &i : M) {
@@ -793,7 +811,8 @@
         &i != DFSanUnimplementedFn.getCallee()->stripPointerCasts() &&
         &i != DFSanSetLabelFn.getCallee()->stripPointerCasts() &&
         &i != DFSanNonzeroLabelFn.getCallee()->stripPointerCasts() &&
-        &i != DFSanVarargWrapperFn.getCallee()->stripPointerCasts())
+        &i != DFSanVarargWrapperFn.getCallee()->stripPointerCasts() &&
+        &i != DFSanStoreCallbackFn.getCallee()->stripPointerCasts())
       FnsToInstrument.push_back(&i);
   }
 
@@ -1396,6 +1415,10 @@
     Shadow = DFSF.combineShadows(Shadow, PtrShadow, &SI);
   }
   DFSF.storeShadow(SI.getPointerOperand(), Size, Alignement, Shadow, &SI);
+  if (ClEventCallbacks) {
+    IRBuilder<> IRB(&SI);
+    IRB.CreateCall(DFSF.DFS.DFSanStoreCallbackFn, Shadow);
+  }
 }
 
 void DFSanVisitor::visitUnaryOperator(UnaryOperator &UO) {