[DFSan] Add option for conditional callbacks.

[browneee]

Summary

This allows DFSan to find tainted values used to control program behavior.

[browneee]

Fix formatting.

[browneee]

rebase

[morehouse]

compiler-rt/test/dfsan/conditional_callbacks.c

23

These Argv variables are unused.

56

Unused.

compiler-rt/test/dfsan/origin_conditional_callbacks.c

23

Argv variables unused again.

107

This test is nearly identical to conditional_callbacks.c. Let's combine them.

[browneee]

Fix comments

[morehouse]

LGTM

compiler-rt/include/sanitizer/dfsan_interface.h

 #endif
 
 typedef uint8_t dfsan_label;
 typedef uint32_t dfsan_origin;
 
 /// Signature of the callback argument to dfsan_set_write_callback().
 typedef void (*dfsan_write_callback_t)(int fd, const void *buf, size_t count);
 
+/// Signature of the callback argument to dfsan_set_conditional_callback().
+typedef void (*dfsan_conditional_callback_t)(dfsan_label label,
+                                             dfsan_origin origin);
+
 /// Computes the union of \c l1 and \c l2, resulting in a union label.
 dfsan_label dfsan_union(dfsan_label l1, dfsan_label l2);
 
 /// Sets the label for each address in [addr,addr+size) to \c label.
 void dfsan_set_label(dfsan_label label, void *addr, size_t size);
 
 /// Sets the label for each address in [addr,addr+size) to the union of the
 /// current label for that address and \c label.

 /// taint could still be written to shadow after the flush.
 void dfsan_flush(void);
 
 /// Sets a callback to be invoked on calls to write().  The callback is invoked
 /// before the write is done.  The write is not guaranteed to succeed when the
 /// callback executes.  Pass in NULL to remove any callback.
 void dfsan_set_write_callback(dfsan_write_callback_t labeled_write_callback);
 
+/// Sets a callback to be invoked on any conditional expressions which have a
+/// taint label set. This can be used to find where tainted data influences
+/// the behavior of the program.
+/// These callbacks will only be added when -dfsan-conditional-callbacks=true.
+void dfsan_set_conditional_callback(dfsan_conditional_callback_t callback);
+
+/// Conditional expressions occur during signal handlers.
+/// Making callbacks that handle signals well is tricky, so when
+/// -dfsan-conditional-callbacks=true, conditional expressions used in signal
+/// handlers will add the labels they see into a global (bitwise-or together).
+/// This function returns all label bits seen in signal handler conditions.
+dfsan_label dfsan_get_labels_in_signal_conditional();
+
 /// Interceptor hooks.
 /// Whenever a dfsan's custom function is called the corresponding
 /// hook is called it non-zero. The hooks should be defined by the user.
 /// The primary use case is taint-guided fuzzing, where the fuzzer
 /// needs to see the parameters of the function and the labels.
 /// FIXME: implement more hooks.
 void dfsan_weak_hook_memcmp(void *caller_pc, const void *s1, const void *s2,
                             size_t n, dfsan_label s1_label,

compiler-rt/lib/dfsan/dfsan.cpp

SANITIZER_INTERFACE_ATTRIBUTE void dfsan_set_label_origin(dfsan_label label,
   __dfsan_set_label(label, origin, addr, size);
 }
 
 extern "C" SANITIZER_INTERFACE_ATTRIBUTE int
 dfsan_has_label(dfsan_label label, dfsan_label elem) {
   return (label & elem) == elem;
 }
 
+namespace __dfsan {
+
+typedef void (*dfsan_conditional_callback_t)(dfsan_label label,
+                                             dfsan_origin origin);
+static dfsan_conditional_callback_t conditional_callback = nullptr;
+static dfsan_label labels_in_signal_conditional = 0;
+
+static void ConditionalCallback(dfsan_label label, dfsan_origin origin) {
+  // Programs have many branches. For efficiency the conditional sink callback
+  // handler needs to ignore as many as possible as early as possible.
+  if (label == 0) {
+    return;
+  }
+  if (conditional_callback == nullptr) {
+    return;
+  }
+
+  // This initial ConditionalCallback handler needs to be in here in dfsan
+  // runtime (rather than being an entirely user implemented hook) so that it
+  // has access to dfsan thread information.
+  DFsanThread *t = GetCurrentThread();
+  // A callback operation which does useful work (like record the flow) will
+  // likely be too long executed in a signal handler.
+  if (t && t->InSignalHandler()) {
+    // Record set of labels used in signal handler for completeness.
+    labels_in_signal_conditional |= label;
+    return;
+  }
+
+  conditional_callback(label, origin);
+}
+
+}  // namespace __dfsan
+
+extern "C" SANITIZER_INTERFACE_ATTRIBUTE void
+__dfsan_conditional_callback_origin(dfsan_label label, dfsan_origin origin) {
+  __dfsan::ConditionalCallback(label, origin);
+}
+
+extern "C" SANITIZER_INTERFACE_ATTRIBUTE void __dfsan_conditional_callback(
+    dfsan_label label) {
+  __dfsan::ConditionalCallback(label, 0);
+}
+
+extern "C" SANITIZER_INTERFACE_ATTRIBUTE void dfsan_set_conditional_callback(
+    __dfsan::dfsan_conditional_callback_t callback) {
+  __dfsan::conditional_callback = callback;
+}
+
+extern "C" SANITIZER_INTERFACE_ATTRIBUTE dfsan_label
+dfsan_get_labels_in_signal_conditional() {
+  return __dfsan::labels_in_signal_conditional;
+}
+
 class Decorator : public __sanitizer::SanitizerCommonDecorator {
  public:
   Decorator() : SanitizerCommonDecorator() {}
   const char *Origin() const { return Magenta(); }
 };
 
 namespace {
 
for (unsigned i = 0; i < kMemoryLayoutSize; ++i) {
     if (start >= maxVirtualAddress)
       continue;
 
     if (!MmapFixedSuperNoReserve(start, size, kMemoryLayout[i].name)) {
       Printf("FATAL: DataFlowSanitizer: failed to clear memory region\n");
       Die();
     }
   }
+  __dfsan::labels_in_signal_conditional = 0;
 }
 
 // TODO: CheckMemoryLayoutSanity is based on msan.
 // Consider refactoring these into a shared implementation.
 static void CheckMemoryLayoutSanity() {
   uptr prev_end = 0;
   for (unsigned i = 0; i < kMemoryLayoutSize; ++i) {
     uptr start = kMemoryLayout[i].start;

compiler-rt/lib/dfsan/done_abilist.txt

 fun:dfsan_get_origin=uninstrumented
 fun:dfsan_get_origin=custom
 fun:dfsan_read_origin_of_first_taint=uninstrumented
 fun:dfsan_read_origin_of_first_taint=discard
 fun:dfsan_get_init_origin=uninstrumented
 fun:dfsan_get_init_origin=discard
 fun:dfsan_get_track_origins=uninstrumented
 fun:dfsan_get_track_origins=discard
+fun:dfsan_set_conditional_callback=uninstrumented
+fun:dfsan_set_conditional_callback=discard
+fun:dfsan_get_labels_in_signal_conditional=uninstrumented
+fun:dfsan_get_labels_in_signal_conditional=discard
 
 ###############################################################################
 # glibc
 ###############################################################################
 # Functions of memory allocators
 fun:__libc_memalign=discard
 fun:aligned_alloc=discard
 fun:calloc=discard

compiler-rt/test/dfsan/Inputs/flags_abilist.txt

 fun:f=uninstrumented
 
 fun:function_to_force_zero=force_zero_labels
 
 fun:main=uninstrumented
 fun:main=discard
 
 fun:dfsan_set_label=uninstrumented
 fun:dfsan_set_label=discard
+
+fun:my_dfsan_conditional_callback=uninstrumented
+fun:my_dfsan_conditional_callback=discard
+
+fun:dfsan_set_conditional_callback=uninstrumented
+fun:dfsan_set_conditional_callback=discard

compiler-rt/test/dfsan/conditional_callbacks.c

+// RUN: %clang_dfsan -fno-sanitize=dataflow -O2 -fPIE -DCALLBACKS -c %s -o %t-callbacks.o
+// RUN: %clang_dfsan -fsanitize-ignorelist=%S/Inputs/flags_abilist.txt -O2 -mllvm -dfsan-conditional-callbacks %s %t-callbacks.o -o %t
+// RUN: %run %t FooBarBaz 2>&1 | FileCheck %s
+//
+// REQUIRES: x86_64-target-arch
+
+// Tests that callbacks are inserted for conditionals when
+// -dfsan-conditional-callbacks is specified.
+
+#include <assert.h>
+#include <sanitizer/dfsan_interface.h>
+#include <stdio.h>
+#include <string.h>
+
+#ifdef CALLBACKS
+// Compile this code without DFSan to avoid recursive instrumentation.
+
+extern dfsan_label LabelI;
+extern dfsan_label LabelJ;
+extern dfsan_label LabelIJ;
+extern dfsan_label LabelArgv;
+extern size_t LenArgv;
+
+void my_dfsan_conditional_callback(dfsan_label Label, dfsan_origin Origin) {
+  assert(Label != 0);
+  assert(Origin == 0);
+
+  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:
+    break;
+  }
+
+  fprintf(stderr, "Label %u used as condition\n", Label);
+}
+
+#else
+// Compile this code with DFSan and -dfsan-conditional-callbacks to insert the
+// callbacks.
+
+dfsan_label LabelI;
+dfsan_label LabelJ;
+dfsan_label LabelIJ;
+dfsan_label LabelArgv;
+
+size_t LenArgv;
+
+extern void my_dfsan_conditional_callback(dfsan_label Label, dfsan_origin Origin);
+
+int main(int Argc, char *Argv[]) {
+  assert(Argc == 2);
+
+  dfsan_set_conditional_callback(my_dfsan_conditional_callback);
+
+  int result = 0;
+  // Make these not look like constants, otherwise the branch we're expecting
+  // may be optimized out.
+  int DataI = (Argv[0][0] != 0) ? 1 : 0;
+  int DataJ = (Argv[1][0] != 0) ? 2 : 0;
+  LabelI = 1;
+  dfsan_set_label(LabelI, &DataI, sizeof(DataI));
+  LabelJ = 2;
+  dfsan_set_label(LabelJ, &DataJ, sizeof(DataJ));
+  LabelIJ = dfsan_union(LabelI, LabelJ);
+
+  assert(dfsan_get_label(DataI) == LabelI);
+
+  // CHECK: Label 1 used as condition
+  if (DataI) {
+    result = 42;
+  }
+
+  assert(dfsan_get_label(DataJ) == LabelJ);
+
+  // CHECK: Label 2 used as condition
+  switch (DataJ) {
+    case 1:
+      result += 10000;
+      break;
+    case 2:
+      result += 4200;
+      break;
+    default:
+      break;
+  }
+
+  int tainted_cond = ((DataI * DataJ) != 1);
+  assert(dfsan_get_label(tainted_cond) == LabelIJ);
+
+  // CHECK: Label 3 used as condition
+  result = tainted_cond ? result + 420000 : 9;
+
+  assert(result == 424242);
+  return 0;
+}
+
+#endif // #ifdef CALLBACKS

compiler-rt/test/dfsan/conditional_callbacks_sig.c

+// RUN: %clang_dfsan -fno-sanitize=dataflow -O2 -fPIE -DCALLBACKS -c %s -o %t-callbacks.o
+// RUN: %clang_dfsan -fsanitize-ignorelist=%S/Inputs/flags_abilist.txt -O2 -mllvm -dfsan-conditional-callbacks %s %t-callbacks.o -o %t
+// RUN: %run %t FooBarBaz 2>&1 | FileCheck %s
+//
+// REQUIRES: x86_64-target-arch
+
+#include <sanitizer/dfsan_interface.h>
+#include <assert.h>
+#include <stdio.h>
+#include <string.h>
+#include <signal.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#ifdef CALLBACKS
+// Compile this code without DFSan to avoid recursive instrumentation.
+
+void my_dfsan_conditional_callback(dfsan_label Label, dfsan_origin Origin) {
+  assert(Label != 0);
+  assert(Origin == 0);
+
+  static int Count = 0;
+  switch (Count++) {
+  case 0:
+    assert(Label == 1);
+    break;
+  case 1:
+    assert(Label == 4);
+    break;
+  default:
+    break;
+  }
+
+  fprintf(stderr, "Label %u used as condition\n", Label);
+}
+
+#else
+// Compile this code with DFSan and -dfsan-conditional-callbacks to insert the
+// callbacks.
+
+extern void my_dfsan_conditional_callback(dfsan_label Label, dfsan_origin Origin);
+
+volatile int x = 0;
+volatile int y = 1;
+volatile int z = 0;
+
+void SignalHandler(int signo) {
+  assert(dfsan_get_label(x) == 0);
+  assert(dfsan_get_label(y) != 0);
+  assert(dfsan_get_label(z) != 0);
+  // Running the conditional callback from a signal handler is risky,
+  // because the code must be written with signal handler context in mind.
+  // Instead dfsan_get_labels_in_signal_conditional() will indicate labels
+  // used in conditions inside signal handlers.
+  // CHECK-NOT: Label 8 used as condition
+  if (z != 0) {
+    x = y;
+  }
+}
+
+int main(int Argc, char *Argv[]) {
+  assert(Argc >= 1);
+  int unknown = (Argv[0][0] != 0) ? 1 : 0;
+  dfsan_set_label(1, &unknown, sizeof(unknown));
+
+  dfsan_set_conditional_callback(my_dfsan_conditional_callback);
+
+  // CHECK: Label 1 used as condition
+  if (unknown) {
+      z = 42;
+  }
+
+  assert(dfsan_get_labels_in_signal_conditional() == 0);
+  dfsan_set_label(4, (void *)&y, sizeof(y));
+  dfsan_set_label(8, (void *)&z, sizeof(z));
+
+  struct sigaction sa = {};
+  sa.sa_handler = SignalHandler;
+  int r = sigaction(SIGHUP, &sa, NULL);
+  assert(dfsan_get_label(r) == 0);
+
+  kill(getpid(), SIGHUP);
+  signal(SIGHUP, SIG_DFL);
+
+  assert(dfsan_get_labels_in_signal_conditional() == 8);
+  assert(x == 1);
+  // CHECK: Label 4 used as condition
+  if (x != 0) {
+    z = 123;
+  }
+  // Flush should clear the conditional signals seen.
+  dfsan_flush();
+  assert(dfsan_get_labels_in_signal_conditional() == 0);
+  return 0;
+}
+
+#endif // #ifdef CALLBACKS

compiler-rt/test/dfsan/origin_conditional_callbacks.c

+// RUN: %clang_dfsan -fno-sanitize=dataflow -O2 -fPIE -DCALLBACKS -c %s -o %t-callbacks.o
+// RUN: %clang_dfsan -fsanitize-ignorelist=%S/Inputs/flags_abilist.txt -O2 -mllvm -dfsan-conditional-callbacks -mllvm -dfsan-track-origins=1 %s %t-callbacks.o -o %t
+// RUN: %run %t FooBarBaz 2>&1 | FileCheck %s
+//
+// REQUIRES: x86_64-target-arch
+
+// Tests that callbacks are inserted for conditionals when
+// -dfsan-conditional-callbacks is specified.
+
+#include <assert.h>
+#include <sanitizer/dfsan_interface.h>
+#include <stdio.h>
+#include <string.h>
+
+#ifdef CALLBACKS
+// Compile this code without DFSan to avoid recursive instrumentation.
+
+extern dfsan_label LabelI;
+extern dfsan_label LabelJ;
+extern dfsan_label LabelIJ;
+extern dfsan_label LabelArgv;
+extern size_t LenArgv;
+
+void my_dfsan_conditional_callback(dfsan_label Label, dfsan_origin Origin) {
+  assert(Label != 0);
+  assert(Origin != 0);
+
+  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:
+    break;
+  }
+
+  fprintf(stderr, "Label %u used as condition\n", Label);
+}
+
+#else
+// Compile this code with DFSan and -dfsan-conditional-callbacks to insert the
+// callbacks.
+
+dfsan_label LabelI;
+dfsan_label LabelJ;
+dfsan_label LabelIJ;
+dfsan_label LabelArgv;
+
+size_t LenArgv;
+
+extern void my_dfsan_conditional_callback(dfsan_label Label, dfsan_origin Origin);
+
+int main(int Argc, char *Argv[]) {
+  assert(Argc == 2);
+
+  dfsan_set_conditional_callback(my_dfsan_conditional_callback);
+
+  int result = 0;
+  // Make these not look like constants, otherwise the branch we're expecting
+  // may be optimized out.
+  int DataI = (Argv[0][0] != 0) ? 1 : 0;
+  int DataJ = (Argv[1][0] != 0) ? 2 : 0;
+  LabelI = 1;
+  dfsan_set_label(LabelI, &DataI, sizeof(DataI));
+  LabelJ = 2;
+  dfsan_set_label(LabelJ, &DataJ, sizeof(DataJ));
+  LabelIJ = dfsan_union(LabelI, LabelJ);
+
+  assert(dfsan_get_label(DataI) == LabelI);
+
+  // CHECK: Label 1 used as condition
+  if (DataI) {
+    result = 42;
+  }
+
+  assert(dfsan_get_label(DataJ) == LabelJ);
+
+  // CHECK: Label 2 used as condition
+  switch (DataJ) {
+    case 1:
+      result += 10000;
+      break;
+    case 2:
+      result += 4200;
+      break;
+    default:
+      break;
+  }
+
+  int tainted_cond = ((DataI * DataJ) != 1);
+  assert(dfsan_get_label(tainted_cond) == LabelIJ);
+
+  // CHECK: Label 3 used as condition
+  result = tainted_cond ? result + 420000 : 9;
+
+  assert(result == 424242);
+  return 0;
+}
+
+#endif // #ifdef CALLBACKS

llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp

 //   void __dfsan_store_callback(dfsan_label Label, void* addr);
 //   void __dfsan_mem_transfer_callback(dfsan_label *Start, size_t Len);
 //   void __dfsan_cmp_callback(dfsan_label CombinedLabel);
 static cl::opt<bool> ClEventCallbacks(
     "dfsan-event-callbacks",
     cl::desc("Insert calls to __dfsan_*_callback functions on data events."),
     cl::Hidden, cl::init(false));
 
+// Experimental feature that inserts callbacks for conditionals, including:
+// conditional branch, switch, select.
+// This must be true for dfsan_set_conditional_callback() to have effect.
+static cl::opt<bool> ClConditionalCallbacks(
+    "dfsan-conditional-callbacks",
+    cl::desc("Insert calls to callback functions on conditionals."), cl::Hidden,
+    cl::init(false));
+
 // Controls whether the pass tracks the control flow of select instructions.
 static cl::opt<bool> ClTrackSelectControlFlow(
     "dfsan-track-select-control-flow",
     cl::desc("Propagate labels from condition values of select instructions "
              "to results."),
     cl::Hidden, cl::init(true));
 
 // TODO: This default value follows MSan. DFSan may use a different value.
class DataFlowSanitizer {
   Constant *RetvalTLS;
   Constant *RetvalOriginTLS;
   FunctionType *DFSanUnionLoadFnTy;
   FunctionType *DFSanLoadLabelAndOriginFnTy;
   FunctionType *DFSanUnimplementedFnTy;
   FunctionType *DFSanSetLabelFnTy;
   FunctionType *DFSanNonzeroLabelFnTy;
   FunctionType *DFSanVarargWrapperFnTy;
+  FunctionType *DFSanConditionalCallbackFnTy;
+  FunctionType *DFSanConditionalCallbackOriginFnTy;
   FunctionType *DFSanCmpCallbackFnTy;
   FunctionType *DFSanLoadStoreCallbackFnTy;
   FunctionType *DFSanMemTransferCallbackFnTy;
   FunctionType *DFSanChainOriginFnTy;
   FunctionType *DFSanChainOriginIfTaintedFnTy;
   FunctionType *DFSanMemOriginTransferFnTy;
   FunctionType *DFSanMaybeStoreOriginFnTy;
   FunctionCallee DFSanUnionLoadFn;
   FunctionCallee DFSanLoadLabelAndOriginFn;
   FunctionCallee DFSanUnimplementedFn;
   FunctionCallee DFSanSetLabelFn;
   FunctionCallee DFSanNonzeroLabelFn;
   FunctionCallee DFSanVarargWrapperFn;
   FunctionCallee DFSanLoadCallbackFn;
   FunctionCallee DFSanStoreCallbackFn;
   FunctionCallee DFSanMemTransferCallbackFn;
+  FunctionCallee DFSanConditionalCallbackFn;
+  FunctionCallee DFSanConditionalCallbackOriginFn;
   FunctionCallee DFSanCmpCallbackFn;
   FunctionCallee DFSanChainOriginFn;
   FunctionCallee DFSanChainOriginIfTaintedFn;
   FunctionCallee DFSanMemOriginTransferFn;
   FunctionCallee DFSanMaybeStoreOriginFn;
   SmallPtrSet<Value *, 16> DFSanRuntimeFunctions;
   MDNode *ColdCallWeights;
   MDNode *OriginStoreWeights;
struct DFSanFunction {
   /// CTP(other types, PS) = PS
   Value *collapseToPrimitiveShadow(Value *Shadow, Instruction *Pos);
 
   void storeZeroPrimitiveShadow(Value *Addr, uint64_t Size, Align ShadowAlign,
                                 Instruction *Pos);
 
   Align getShadowAlign(Align InstAlignment);
 
+  // If ClConditionalCallbacks is enabled, insert a callback after a given
+  // branch instruction using the given conditional expression.
+  void addConditionalCallbacksIfEnabled(Instruction &I, Value *Condition);
+
 private:
   /// Collapses the shadow with aggregate type into a single primitive shadow
   /// value.
   template <class AggregateType>
   Value *collapseAggregateShadow(AggregateType *AT, Value *Shadow,
                                  IRBuilder<> &IRB);
 
   Value *collapseToPrimitiveShadow(Value *Shadow, IRBuilder<> &IRB);
public:
   void visitInsertElementInst(InsertElementInst &I);
   void visitShuffleVectorInst(ShuffleVectorInst &I);
   void visitExtractValueInst(ExtractValueInst &I);
   void visitInsertValueInst(InsertValueInst &I);
   void visitAllocaInst(AllocaInst &I);
   void visitSelectInst(SelectInst &I);
   void visitMemSetInst(MemSetInst &I);
   void visitMemTransferInst(MemTransferInst &I);
+  void visitBranchInst(BranchInst &BR);
+  void visitSwitchInst(SwitchInst &SW);
 
 private:
   void visitCASOrRMW(Align InstAlignment, Instruction &I);
 
   // Returns false when this is an invoke of a custom function.
   bool visitWrappedCallBase(Function &F, CallBase &CB);
 
   // Combines origins for all of I's operands.
Value *DFSanFunction::collapseToPrimitiveShadow(Value *Shadow,
 
   IRBuilder<> IRB(Pos);
   Value *PrimitiveShadow = collapseToPrimitiveShadow(Shadow, IRB);
   // Caches the converted primitive shadow value.
   CS = PrimitiveShadow;
   return PrimitiveShadow;
 }
 
+void DFSanFunction::addConditionalCallbacksIfEnabled(Instruction &I,
+                                                     Value *Condition) {
+  if (!ClConditionalCallbacks) {
+    return;
+  }
+  IRBuilder<> IRB(&I);
+  Value *CondShadow = getShadow(Condition);
+  if (DFS.shouldTrackOrigins()) {
+    Value *CondOrigin = getOrigin(Condition);
+    IRB.CreateCall(DFS.DFSanConditionalCallbackOriginFn,
+                   {CondShadow, CondOrigin});
+  } else {
+    IRB.CreateCall(DFS.DFSanConditionalCallbackFn, {CondShadow});
+  }
+}
+
 Type *DataFlowSanitizer::getShadowTy(Type *OrigTy) {
   if (!OrigTy->isSized())
     return PrimitiveShadowTy;
   if (isa<IntegerType>(OrigTy))
     return PrimitiveShadowTy;
   if (isa<VectorType>(OrigTy))
     return PrimitiveShadowTy;
   if (ArrayType *AT = dyn_cast<ArrayType>(OrigTy))
bool DataFlowSanitizer::initializeModule(Module &M) {
   Type *DFSanSetLabelArgs[4] = {PrimitiveShadowTy, OriginTy,
                                 Type::getInt8PtrTy(*Ctx), IntptrTy};
   DFSanSetLabelFnTy = FunctionType::get(Type::getVoidTy(*Ctx),
                                         DFSanSetLabelArgs, /*isVarArg=*/false);
   DFSanNonzeroLabelFnTy =
       FunctionType::get(Type::getVoidTy(*Ctx), None, /*isVarArg=*/false);
   DFSanVarargWrapperFnTy = FunctionType::get(
       Type::getVoidTy(*Ctx), Type::getInt8PtrTy(*Ctx), /*isVarArg=*/false);
+  DFSanConditionalCallbackFnTy =
+      FunctionType::get(Type::getVoidTy(*Ctx), PrimitiveShadowTy,
+                        /*isVarArg=*/false);
+  Type *DFSanConditionalCallbackOriginArgs[2] = {PrimitiveShadowTy, OriginTy};
+  DFSanConditionalCallbackOriginFnTy = FunctionType::get(
+      Type::getVoidTy(*Ctx), DFSanConditionalCallbackOriginArgs,
+      /*isVarArg=*/false);
   DFSanCmpCallbackFnTy =
       FunctionType::get(Type::getVoidTy(*Ctx), PrimitiveShadowTy,
                         /*isVarArg=*/false);
   DFSanChainOriginFnTy =
       FunctionType::get(OriginTy, OriginTy, /*isVarArg=*/false);
   Type *DFSanChainOriginIfTaintedArgs[2] = {PrimitiveShadowTy, OriginTy};
   DFSanChainOriginIfTaintedFnTy = FunctionType::get(
       OriginTy, DFSanChainOriginIfTaintedArgs, /*isVarArg=*/false);
DFSanRuntimeFunctions.insert(
       DFSanVarargWrapperFn.getCallee()->stripPointerCasts());
   DFSanRuntimeFunctions.insert(
       DFSanLoadCallbackFn.getCallee()->stripPointerCasts());
   DFSanRuntimeFunctions.insert(
       DFSanStoreCallbackFn.getCallee()->stripPointerCasts());
   DFSanRuntimeFunctions.insert(
       DFSanMemTransferCallbackFn.getCallee()->stripPointerCasts());
   DFSanRuntimeFunctions.insert(
+      DFSanConditionalCallbackFn.getCallee()->stripPointerCasts());
+  DFSanRuntimeFunctions.insert(
+      DFSanConditionalCallbackOriginFn.getCallee()->stripPointerCasts());
+  DFSanRuntimeFunctions.insert(
       DFSanCmpCallbackFn.getCallee()->stripPointerCasts());
   DFSanRuntimeFunctions.insert(
       DFSanChainOriginFn.getCallee()->stripPointerCasts());
   DFSanRuntimeFunctions.insert(
       DFSanChainOriginIfTaintedFn.getCallee()->stripPointerCasts());
   DFSanRuntimeFunctions.insert(
       DFSanMemOriginTransferFn.getCallee()->stripPointerCasts());
   DFSanRuntimeFunctions.insert(
       DFSanMaybeStoreOriginFn.getCallee()->stripPointerCasts());
 }
 
 // Initializes event callback functions and declare them in the module
 void DataFlowSanitizer::initializeCallbackFunctions(Module &M) {
   DFSanLoadCallbackFn = Mod->getOrInsertFunction("__dfsan_load_callback",
                                                  DFSanLoadStoreCallbackFnTy);
   DFSanStoreCallbackFn = Mod->getOrInsertFunction("__dfsan_store_callback",
                                                   DFSanLoadStoreCallbackFnTy);
   DFSanMemTransferCallbackFn = Mod->getOrInsertFunction(
       "__dfsan_mem_transfer_callback", DFSanMemTransferCallbackFnTy);
   DFSanCmpCallbackFn =
       Mod->getOrInsertFunction("__dfsan_cmp_callback", DFSanCmpCallbackFnTy);
+
+  DFSanConditionalCallbackFn = Mod->getOrInsertFunction(
+      "__dfsan_conditional_callback", DFSanConditionalCallbackFnTy);
+  DFSanConditionalCallbackOriginFn =
+      Mod->getOrInsertFunction("__dfsan_conditional_callback_origin",
+                               DFSanConditionalCallbackOriginFnTy);
 }
 
 void DataFlowSanitizer::injectMetadataGlobals(Module &M) {
   // These variables can be used:
   // - by the runtime (to discover what the shadow width was, during
   //   compilation)
   // - in testing (to avoid hardcoding the shadow width and type but instead
   //   extract them by pattern matching)
void DFSanVisitor::visitSelectInst(SelectInst &I) {
   const bool ShouldTrackOrigins = DFSF.DFS.shouldTrackOrigins();
   std::vector<Value *> Shadows;
   std::vector<Value *> Origins;
   Value *TrueOrigin =
       ShouldTrackOrigins ? DFSF.getOrigin(I.getTrueValue()) : nullptr;
   Value *FalseOrigin =
       ShouldTrackOrigins ? DFSF.getOrigin(I.getFalseValue()) : nullptr;
 
+  DFSF.addConditionalCallbacksIfEnabled(I, I.getCondition());
+
   if (isa<VectorType>(I.getCondition()->getType())) {
     ShadowSel = DFSF.combineShadowsThenConvert(I.getType(), TrueShadow,
                                                FalseShadow, &I);
     if (ShouldTrackOrigins) {
       Shadows.push_back(TrueShadow);
       Shadows.push_back(FalseShadow);
       Origins.push_back(TrueOrigin);
       Origins.push_back(FalseOrigin);
void DFSanVisitor::visitMemTransferInst(MemTransferInst &I) {
   }
   if (ClEventCallbacks) {
     IRB.CreateCall(DFSF.DFS.DFSanMemTransferCallbackFn,
                    {RawDestShadow,
                     IRB.CreateZExtOrTrunc(I.getLength(), DFSF.DFS.IntptrTy)});
   }
 }
 
+void DFSanVisitor::visitBranchInst(BranchInst &BR) {
+  if (!BR.isConditional())
+    return;
+
+  DFSF.addConditionalCallbacksIfEnabled(BR, BR.getCondition());
+}
+
+void DFSanVisitor::visitSwitchInst(SwitchInst &SW) {
+  DFSF.addConditionalCallbacksIfEnabled(SW, SW.getCondition());
+}
+
 static bool isAMustTailRetVal(Value *RetVal) {
   // Tail call may have a bitcast between return.
   if (auto *I = dyn_cast<BitCastInst>(RetVal)) {
     RetVal = I->getOperand(0);
   }
   if (auto *I = dyn_cast<CallInst>(RetVal)) {
     return I->isMustTailCall();
   }