Index: compiler-rt/lib/fuzzer/FuzzerDriver.cpp
===================================================================
--- compiler-rt/lib/fuzzer/FuzzerDriver.cpp
+++ compiler-rt/lib/fuzzer/FuzzerDriver.cpp
@@ -668,6 +668,7 @@
   Options.IgnoreTimeouts = Flags.ignore_timeouts;
   Options.IgnoreOOMs = Flags.ignore_ooms;
   Options.IgnoreCrashes = Flags.ignore_crashes;
+  Options.IgnoreRemoteExits = Flags.ignore_remote_exits;
   Options.MaxTotalTimeSec = Flags.max_total_time;
   Options.DoCrossOver = Flags.cross_over;
   Options.CrossOverUniformDist = Flags.cross_over_uniform_dist;
@@ -677,6 +678,7 @@
   Options.UseMemmem = Flags.use_memmem;
   Options.UseCmp = Flags.use_cmp;
   Options.UseValueProfile = Flags.use_value_profile;
+  Options.UseRemote = Flags.remote;
   Options.Shrink = Flags.shrink;
   Options.ReduceInputs = Flags.reduce_inputs;
   Options.ShuffleAtStartUp = Flags.shuffle;
Index: compiler-rt/lib/fuzzer/FuzzerExtFunctions.def
===================================================================
--- compiler-rt/lib/fuzzer/FuzzerExtFunctions.def
+++ compiler-rt/lib/fuzzer/FuzzerExtFunctions.def
@@ -27,6 +27,7 @@
 // Sanitizer functions
 EXT_FUNC(__lsan_enable, void, (), false);
 EXT_FUNC(__lsan_disable, void, (), false);
+EXT_FUNC(__lsan_do_leak_check, void, (), false);
 EXT_FUNC(__lsan_do_recoverable_leak_check, int, (), false);
 EXT_FUNC(__sanitizer_acquire_crash_state, int, (), true);
 EXT_FUNC(__sanitizer_install_malloc_and_free_hooks, int,
@@ -48,3 +49,14 @@
 EXT_FUNC(__msan_scoped_enable_interceptor_checks, void, (), false);
 EXT_FUNC(__msan_unpoison, void, (const volatile void *, size_t size), false);
 EXT_FUNC(__msan_unpoison_param, void, (size_t n), false);
+
+// IPC functions
+EXT_FUNC(FuzzerAcceptRemotes, void, (), false);
+EXT_FUNC(FuzzerShutdownRemotes, void, (), false);
+EXT_FUNC(FuzzerRemoteStartExecution, void, (unsigned long, uint32_t), false);
+EXT_FUNC(FuzzerRemoteFinishExecution, void, (unsigned long), false);
+EXT_FUNC(FuzzerRemotePrintPC, void, (unsigned long, const char *, const char *, uintptr_t), false);
+EXT_FUNC(FuzzerRemoteDescribePC, void, (unsigned long, const char *, uintptr_t, char *, size_t), false);
+EXT_FUNC(FuzzerRemotePrintStackTrace, void, (unsigned long), false);
+EXT_FUNC(FuzzerRemotePrintMemoryProfile, void, (unsigned long), false);
+EXT_FUNC(FuzzerRemoteDetectLeaksAtExit, void, (unsigned long), false);
Index: compiler-rt/lib/fuzzer/FuzzerFlags.def
===================================================================
--- compiler-rt/lib/fuzzer/FuzzerFlags.def
+++ compiler-rt/lib/fuzzer/FuzzerFlags.def
@@ -61,6 +61,7 @@
 FUZZER_FLAG_INT(ignore_timeouts, 1, "Ignore timeouts in fork mode")
 FUZZER_FLAG_INT(ignore_ooms, 1, "Ignore OOMs in fork mode")
 FUZZER_FLAG_INT(ignore_crashes, 0, "Ignore crashes in fork mode")
+FUZZER_FLAG_INT(ignore_remote_exits, 0, "Ignore remote processes exiting normally")
 FUZZER_FLAG_INT(merge, 0, "If 1, the 2-nd, 3-rd, etc corpora will be "
   "merged into the 1-st corpus. Only interesting units will be taken. "
   "This flag can be used to minimize a corpus.")
@@ -99,6 +100,9 @@
 FUZZER_FLAG_INT(use_value_profile, 0,
                 "Experimental. Use value profile to guide fuzzing.")
 FUZZER_FLAG_INT(use_cmp, 1, "Use CMP traces to guide mutations")
+FUZZER_FLAG_INT(remote, 0, "Experimental. Allow remote processes to connect and"
+                          " forward coverage information. Used to fuzz"
+                          " interprocess communication.")
 FUZZER_FLAG_INT(shrink, 0, "Experimental. Try to shrink corpus inputs.")
 FUZZER_FLAG_INT(reduce_inputs, 1,
   "Try to reduce the size of inputs while preserving their full feature sets")
Index: compiler-rt/lib/fuzzer/FuzzerOptions.h
===================================================================
--- compiler-rt/lib/fuzzer/FuzzerOptions.h
+++ compiler-rt/lib/fuzzer/FuzzerOptions.h
@@ -27,6 +27,7 @@
   bool IgnoreTimeouts = true;
   bool IgnoreOOMs = true;
   bool IgnoreCrashes = false;
+  bool IgnoreRemoteExits = false;
   int MaxTotalTimeSec = 0;
   int RssLimitMb = 0;
   int MallocLimitMb = 0;
@@ -38,6 +39,7 @@
   bool UseMemmem = true;
   bool UseCmp = false;
   int UseValueProfile = false;
+  bool UseRemote = false;
   bool Shrink = false;
   bool ReduceInputs = false;
   int ReloadIntervalSec = 1;
Index: compiler-rt/lib/fuzzer/tests/FuzzerTestUtil.h
===================================================================
--- compiler-rt/lib/fuzzer/tests/FuzzerTestUtil.h
+++ compiler-rt/lib/fuzzer/tests/FuzzerTestUtil.h
@@ -24,12 +24,24 @@
 // Helper environment to ensure that:
 // * The PRNG is seeded deterministically.
 // * The ExternalFunctions are allocated.
+// * No-op versions of the FuzzerRemote* methods are provided.
 class TestEnvironment : public testing::Environment {
 public:
   void SetUp() override {
     srand(0);
     ExtFuncs.reset(new ExternalFunctions());
     EF = ExtFuncs.get();
+    EF->FuzzerAcceptRemotes = []() {};
+    EF->FuzzerShutdownRemotes = []() {};
+    EF->FuzzerRemoteStartExecution = [](unsigned long PID, uint32_t Flags) {};
+    EF->FuzzerRemoteFinishExecution = [](unsigned long PID) {};
+    EF->FuzzerRemotePrintPC = [](unsigned long PID, const char *SymbolizedFMT,
+                                 const char *FallbackFMT, uintptr_t PC) {};
+    EF->FuzzerRemoteDescribePC = [](unsigned long PID,
+                                    const char *SymbolizedFMT, uintptr_t PC,
+                                    char *Out, size_t OutLen) {};
+    EF->FuzzerRemotePrintStackTrace = [](unsigned long PID) {};
+    EF->FuzzerRemotePrintMemoryProfile = [](unsigned long PID) {};
   }
 
   void TearDown() override { EF = nullptr; }