Index: test/asan/TestCases/Darwin/zone_enumeration/in_process/simple_enumeration.cc
===================================================================
--- /dev/null
+++ test/asan/TestCases/Darwin/zone_enumeration/in_process/simple_enumeration.cc
@@ -0,0 +1,153 @@
+// RUN: %clangxx_asan %s -o %t
+// RUN: %run %t
+
+// This simple test tries to perform in-process malloc zone enumeration.
+#include <cstdio>
+#include <cstdlib>
+#include <fcntl.h>
+#include <mach/mach_error.h>
+#include <mach/mach_init.h>
+#include <malloc/malloc.h>
+#include <string>
+#include <unistd.h>
+#include <unordered_map>
+
+static const int sleep_time = 5000;
+
+// This is a hack to gather the known allocations in this process.  We don't
+// use a std::unordered_map here because that would trigger calls to the
+// allocator inside the hook which we want to avoid.
+static const size_t kMaxAllocations = 50000;
+uintptr_t seen_malloc_addrs[kMaxAllocations];
+size_t seen_malloc_sizes[kMaxAllocations];
+uintptr_t seen_free_addrs[kMaxAllocations];
+bool hook_enabled = true;
+uint32_t current_malloc_index = 0;
+uint32_t current_free_index = 0;
+extern "C" void __sanitizer_malloc_hook(const volatile void *ptr, size_t size) {
+  if (!hook_enabled)
+    return;
+  if (current_malloc_index >= kMaxAllocations) {
+    // Can't record any more allocations
+    fprintf(stderr, "WARNING: Can't record any more allocations\n");
+    return;
+  }
+  seen_malloc_addrs[current_malloc_index] = reinterpret_cast<uintptr_t>(ptr);
+  seen_malloc_sizes[current_malloc_index] = size;
+  ++current_malloc_index;
+}
+extern "C" void __sanitizer_free_hook(const volatile void *ptr) {
+  if (!hook_enabled)
+    return;
+  if (current_free_index >= kMaxAllocations) {
+    // Can't record any more frees
+    fprintf(stderr, "WARNING: Can't record any more frees\n");
+    return;
+  }
+  seen_free_addrs[current_free_index] = reinterpret_cast<uintptr_t>(ptr);
+  ++current_free_index;
+}
+
+// Hack to record malloc zone allocations. We don't use
+// a `std::unordered_map` here because during enumeration
+// the allocator will be locked and `std::unordered_map` might call malloc.
+uintptr_t mz_recorded_allocation_addrs[kMaxAllocations];
+size_t mz_recorded_allocation_sizes[kMaxAllocations];
+uintptr_t current_mz_record_index = 0;
+
+int main(int argc, char **argv) {
+  printf("Started demo ASan application\n");
+
+  // Deliberately perform some allocations that we will check for later.
+  void *a = malloc(512); // Should be served by primary size class allocator
+  void *b =
+      malloc(1024 * 1024); // Should be served by secondary mmap based allocator
+  void *c = malloc(1);
+
+  // Stop recording allocations using the malloc hooks. Operating on
+  // `known_allocations` might trigger malloc/free so we don't want
+  // to record these.
+  hook_enabled = false;
+  std::unordered_map<uintptr_t, size_t> known_allocations;
+  // Populate map with observed mallocs
+  for (unsigned index = 0; index < current_malloc_index; ++index) {
+    known_allocations.insert(
+        {seen_malloc_addrs[index], seen_malloc_sizes[index]});
+  }
+  // Removed free'd allocations
+  for (unsigned index = 0; index < current_free_index; ++index) {
+    known_allocations.erase(seen_free_addrs[index]);
+  }
+  assert(known_allocations.find(reinterpret_cast<uintptr_t>(a)) !=
+         known_allocations.end());
+  assert(known_allocations.find(reinterpret_cast<uintptr_t>(b)) !=
+         known_allocations.end());
+  assert(known_allocations.find(reinterpret_cast<uintptr_t>(c)) !=
+         known_allocations.end());
+  if (known_allocations.size() < 3) {
+    fprintf(stderr, "known_allocations is too small\n");
+    return 1;
+  }
+
+  // Now perform enumeration via malloc zone.
+  malloc_zone_t *mz = malloc_default_zone();
+  malloc_introspection_t *mi = mz->introspect;
+  auto reader_fn = [](task_t remote_task, vm_address_t remote_address,
+                      vm_size_t, void **local_memory) -> kern_return_t {
+    // Local read so nothing to do
+    assert(remote_task == mach_task_self());
+    *local_memory = reinterpret_cast<void *>(remote_address);
+    return KERN_SUCCESS;
+  };
+  auto recorder_fn = [](task_t remote_task, void *context, unsigned type,
+                        vm_range_t *beg, unsigned num) -> void {
+    assert(remote_task == mach_task_self());
+    assert(type == MALLOC_PTR_IN_USE_RANGE_TYPE);
+    assert(num > 0);
+    for (int index = 0; index < num; ++index) {
+      vm_range_t entry = beg[index];
+      mz_recorded_allocation_addrs[current_mz_record_index] = entry.address;
+      mz_recorded_allocation_sizes[current_mz_record_index] = entry.size;
+      ++current_mz_record_index;
+    }
+  };
+  kern_return_t result =
+      mi->enumerator(/*task=*/mach_task_self(), /*context=*/nullptr,
+                     /*type_mask=*/MALLOC_PTR_IN_USE_RANGE_TYPE,
+                     /*zone_address=*/reinterpret_cast<vm_address_t>(mz),
+                     /*reader=*/reader_fn,
+                     /*recorder=*/recorder_fn);
+  if (result != KERN_SUCCESS) {
+    fprintf(stderr, "Failed to enumerate zone: %s\n",
+            mach_error_string(result));
+    return 1;
+  }
+  std::unordered_map<uintptr_t, size_t> enumerated_allocations;
+  // Populate map with enumerated live allocations
+  for (unsigned index = 0; index < current_mz_record_index; ++index) {
+    auto pair =
+        enumerated_allocations.insert({mz_recorded_allocation_addrs[index],
+                                       mz_recorded_allocation_sizes[index]});
+    assert(pair.second && "key already inserted");
+  }
+  assert(enumerated_allocations.size() > 0);
+  // Now make sure that every allocation in `known_allocation` was enumerated
+  for (const auto &pair : known_allocations) {
+    auto addr = pair.first;
+    auto size = pair.second;
+    auto it = enumerated_allocations.find(addr);
+    if (it == enumerated_allocations.end()) {
+      fprintf(stderr, "Failed to find %p\n", reinterpret_cast<void *>(addr));
+      return 1;
+    }
+    if (size != it->second) {
+      fprintf(stderr, "size mismatch %lu != %lu\n", size, it->second);
+      return 1;
+    }
+    printf("Found %p (size %lu) from `known_allocations` in "
+           "`enumerated_allocations`\n",
+           reinterpret_cast<void *>(addr), size);
+  }
+  printf("DONE\n");
+  return 0;
+}
Index: test/asan/TestCases/Darwin/zone_enumeration/out_of_process/analysis_prog.cc
===================================================================
--- /dev/null
+++ test/asan/TestCases/Darwin/zone_enumeration/out_of_process/analysis_prog.cc
@@ -0,0 +1,734 @@
+// This process is the "analysis" portion of the test.
+//
+// The test
+// * Launches an ASan target process
+// * Waits for the target process the address of its malloc zone and
+//   and a list of allocations it knowns about.
+// * Freezes to target process.
+// * Load the ASan dylib and calls the malloc enumeration function,
+//   telling it to examine the ASan target process.
+// * Compares the allocations reported by the malloc enumeration function
+//   and the allocation list that was sent by the ASan target process.
+//
+#include "protocol.h"
+#include <cassert>
+#include <cstdio>
+#include <cstdlib>
+#include <dlfcn.h>
+#include <functional>
+#include <inttypes.h>
+#include <mach/mach.h>
+#include <mach/mach_init.h>
+#include <mach/mach_traps.h>
+#include <mach/mach_vm.h>
+#include <malloc/malloc.h>
+#include <map>
+#include <memory>
+#include <signal.h>
+#include <spawn.h>
+#include <stdarg.h>
+#include <string>
+#include <sys/errno.h>
+#include <sys/mman.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <unordered_map>
+
+extern "C" char **environ;
+
+struct ScopedPosixSpawnFileActions {
+  typedef posix_spawn_file_actions_t dataTy;
+  dataTy actions;
+  ScopedPosixSpawnFileActions() {
+    int failure = posix_spawn_file_actions_init(&actions);
+    assert(failure == 0);
+  }
+  ~ScopedPosixSpawnFileActions() {
+    int failure = posix_spawn_file_actions_destroy(&actions);
+    assert(failure == 0);
+  }
+  void add_close(int fd) {
+    int failure = posix_spawn_file_actions_addclose(&actions, fd);
+    assert(failure == 0);
+  }
+};
+
+void usage_message(const char *name) {
+  printf("%s <asan_dylib_path> <asan_program>\n", name);
+  exit(1);
+}
+
+kern_return_t simple_memory_reader(task_t remote_task,
+                                   vm_address_t remote_address, vm_size_t size,
+                                   void **local_memory);
+
+void vm_range_recorder(task_t, void *context, unsigned type,
+                       vm_range_t *range_begin, unsigned num_ranges);
+
+struct Range {
+  uintptr_t start;
+  size_t size;
+  Range(uintptr_t start, size_t size) : start(start), size(size) {}
+  bool operator==(const Range &other) const {
+    return start == other.start && size == other.size;
+  }
+  uintptr_t end_byte() const { return (start + size - 1); }
+
+  bool overlaps(const Range &other) const {
+    // This starts before other and this's
+    // tail overlaps other
+    if (start < other.start) {
+      if (end_byte() >= other.start) {
+        return true;
+      }
+    }
+
+    // This starts after other and other's
+    // tail overlaps this.
+    if (start > other.start) {
+      if (other.end_byte() >= start) {
+        return true;
+      }
+    }
+    if (*this == other) {
+      // The same ranges overlap
+      return true;
+    }
+    return false;
+  }
+
+  bool contains(const Range &other) const {
+    if (*this == other)
+      return true;
+
+    if (start <= other.start) {
+      if (end_byte() >= other.end_byte()) {
+        return true;
+      }
+    }
+    return false;
+  }
+};
+
+struct VMRegionCache {
+  struct RangeCompare {
+    bool operator()(const Range &a, const Range &b) const {
+      if (a.overlaps(b)) {
+        // Ranges that overlap are consider incomparable.
+        // This should mean that when do a search for a range
+        // than contained within a stored range then it will
+        // be returned.
+        return false;
+      }
+      // If there's no overlap then order by the start address.
+      return a.start < b.start;
+    }
+  };
+  using RegionMap = std::multimap<Range, uintptr_t, RangeCompare>;
+
+private:
+  // Maps VM regions in target process to VM regions in local process.
+  RegionMap regions;
+
+public:
+  VMRegionCache() {}
+
+  ~VMRegionCache() {
+    // Free regions
+    for (const auto &region_pair : regions) {
+      int result = munmap(reinterpret_cast<void *>(region_pair.second),
+                          region_pair.first.size);
+      assert(result == 0);
+    }
+  }
+  // Don't copy by accident.
+  VMRegionCache(const VMRegionCache &) = delete;
+  VMRegionCache(VMRegionCache &&) = delete;
+  VMRegionCache &operator=(const VMRegionCache &) = delete;
+  VMRegionCache &operator=(VMRegionCache &&) = delete;
+
+  std::pair<RegionMap::iterator, RegionMap::iterator>
+  find_vm_regions_for(Range &r) {
+    return regions.equal_range(r);
+  }
+
+  RegionMap::iterator insert_vm_region(Range &remote_region_range,
+                                       uintptr_t local_region_start) {
+    auto it = regions.insert({remote_region_range, local_region_start});
+    return it;
+  }
+};
+
+void custom_signal_handler(int sig_num, siginfo_t *info, void *uap);
+
+struct Analyzer {
+  std::string dylib_path;
+  std::string target_program;
+  pid_t pid_for_target = 0;
+  task_t task_for_target;
+  task_suspension_token_t task_suspension_token;
+  int pipe_fds[2];
+  int read_fd() { return pipe_fds[0]; }
+  int write_fd() { return pipe_fds[1]; }
+  bool target_is_frozen = false;
+  bool failure = false;
+  size_t page_size;
+  bool print_enumerator_allocations = false;
+  VMRegionCache vm_cache;
+
+  // From target
+  uintptr_t target_zone_addr = 0;
+  std::unordered_map<uintptr_t, size_t> known_allocations;
+
+  // From enumerator
+  std::unordered_map<uintptr_t, size_t> enumerator_reported_allocations;
+
+  // From ASan dylib
+  malloc_introspection_t *dylib_introspection_data;
+  // Function pointer to malloc zone enumerator in ASan dylib
+  kern_return_t (*enumerator)(task_t task, void *, unsigned type_mask,
+                              vm_address_t zone_address, memory_reader_t reader,
+                              vm_range_recorder_t recorder);
+
+  Analyzer(const char *dylib_path, const char *program_name) {
+    this->dylib_path = dylib_path;
+    this->target_program = program_name;
+    this->page_size = getpagesize();
+    if (getenv("ASAN_LEAKS_DEBUG") != 0) {
+      print_enumerator_allocations = true;
+    }
+  }
+
+  bool target_started() { return pid_for_target != 0; }
+
+#ifdef __LP64__
+#define IF_64_ELSE(VALUE_64, VALUE_ELSE) VALUE_64
+#else
+#define IF_64_ELSE(VALUE_64, VALUE_ELSE) VALUE_ELSE
+#endif
+
+  bool record_range_from_enumerator(vm_range_t range) {
+    auto pair =
+        enumerator_reported_allocations.insert({range.address, range.size});
+    if (!pair.second) {
+      log_failure("Attempted to insert range (address:%p, size : % p) which is "
+                  "already stored\n",
+                  range.address, range.size);
+    }
+    if (print_enumerator_allocations) {
+      printf("Target allocation at %p with size %" IF_64_ELSE("lu",
+                                                              "u") " bytes\n",
+             reinterpret_cast<void *>(range.address), range.size);
+    }
+    return pair.second;
+  }
+
+  void log_failure(const char *format_str, ...) {
+    va_list args;
+    va_start(args, format_str);
+    vfprintf(stderr, format_str, args);
+    failure = true;
+    va_end(args);
+  }
+
+  bool failed() const { return failure; }
+
+  uintptr_t round_down_to_page_addr(uintptr_t addr) {
+    return (addr / page_size) * page_size;
+  }
+
+  uintptr_t get_page_number(uintptr_t addr) { return addr / page_size; }
+
+  bool launch_target() {
+    if (target_started())
+      return false;
+    int failure = 0;
+
+    // Set up pipe for communication from child.
+    // After spawn, parent needs to close write end
+    // and child needs to close read end.
+    failure = pipe(pipe_fds);
+    if (failure != 0) {
+      log_failure("Failed to create pipe.\n");
+      perror("");
+      return false;
+    }
+
+    // Make child close the read end of pipe
+    ScopedPosixSpawnFileActions file_actions;
+    file_actions.add_close(read_fd());
+
+    std::string fd_for_child = std::to_string(write_fd());
+    char *const argv[3] = {const_cast<char *>(target_program.c_str()),
+                           const_cast<char *>(fd_for_child.c_str()), nullptr};
+
+    // It's necessary to pass `environ` so that in the iOS simulator
+    // the child process is also launced as a simulator process.
+    failure =
+        posix_spawn(&pid_for_target, target_program.c_str(),
+                    /*file_actions=*/&(file_actions.actions), /*attrp=*/nullptr,
+                    /*argv=*/argv, /*envp=*/environ);
+    if (failure != 0) {
+      log_failure("Failed to launch %s due to \n", target_program.c_str());
+      perror("");
+      return false;
+    }
+    // Close the write end of the pipe in the parent.
+    failure = close(write_fd());
+    assert(failure == 0);
+
+    printf("Launched %s with PID: %d\n", target_program.c_str(),
+           pid_for_target);
+
+    // Set up a custom signal handler so that if we crash
+    // we will kill the child process first.
+    struct sigaction new_action;
+    sigemptyset(&(new_action.sa_mask));
+    new_action.sa_flags = SA_SIGINFO;
+    new_action.sa_sigaction = custom_signal_handler;
+    int signals_to_handle[] = {SIGINT, SIGQUIT, SIGABRT,
+                               SIGBUS, SIGSEGV, SIGFPE};
+    for (int index = 0;
+         index < (sizeof(signals_to_handle) / sizeof(signals_to_handle[0]));
+         ++index) {
+      int signal_to_handle = signals_to_handle[index];
+      printf("Setting up signal handler for signal %d\n", signal_to_handle);
+      failure = sigaction(signal_to_handle, &new_action, /*oact=*/nullptr);
+      if (failure != 0) {
+        log_failure("Failed to set up signal handler for signal %d\n",
+                    signal_to_handle);
+        halt_target();
+        return false;
+      }
+    }
+
+    // Get task port for child process
+    kern_return_t err = task_for_pid(/*target_tport=*/mach_task_self(),
+                                     /*pid=*/pid_for_target,
+                                     /*t=*/&task_for_target);
+    if (err != KERN_SUCCESS) {
+      log_failure("Failed call to task_for_pid with err: %s\n",
+                  mach_error_string(err));
+      halt_target();
+      return false;
+    }
+    printf("Got task port for PID %d\n", pid_for_target);
+    return true;
+  }
+
+  bool halt_target() {
+    assert(target_started());
+    printf("Halting PID %d\n", pid_for_target);
+    kill(pid_for_target, SIGTERM);
+    sleep(2);
+    kill(pid_for_target, SIGKILL);
+    int status = 0;
+    pid_t pid = waitpid(pid_for_target, /*stat_loc=*/&status, /*options=*/0);
+    if (pid != pid_for_target) {
+      perror("Failed waiting for target process to halt");
+      return false;
+    }
+    if (!WIFSIGNALED(status)) {
+      log_failure("Expected process to be killed by a signal\n");
+    } else {
+      // Should be SIGTERM or SIGKILL
+      auto exit_signal = WTERMSIG(status);
+      if (exit_signal != SIGTERM && exit_signal != SIGKILL) {
+        log_failure("Target died with unexpected signal: %d\n", exit_signal);
+      }
+    }
+    target_is_frozen = false;
+    pid_for_target = 0;
+    return true;
+  }
+
+  bool freeze_target() {
+    if (target_is_frozen)
+      return true;
+    auto error = task_suspend2(task_for_target, &task_suspension_token);
+    if (error != KERN_SUCCESS) {
+      log_failure("Failed to freeze process: %s\n", mach_error_string(error));
+      return false;
+    }
+    target_is_frozen = true;
+    return true;
+  }
+
+  bool unfreeze_target() {
+    if (!target_is_frozen) {
+      return true;
+    }
+    auto error = task_resume2(task_suspension_token);
+    if (error != KERN_SUCCESS) {
+      log_failure("Failed to unfreeze process: %s\n", mach_error_string(error));
+      return false;
+    }
+    target_is_frozen = false;
+    return true;
+  }
+
+  bool read_payload() {
+    if (!target_started()) {
+      return false;
+    }
+
+    PayloadHolder ph;
+    bool success = ph.readFromFd(read_fd());
+    if (!success) {
+      log_failure("Failed to read payload\n");
+      return false;
+    }
+
+    // Read payload.
+    // We expect the child to tell us the address of its
+    // malloc zone (which we assume is an ASan malloc zone)
+    // followed by a list of allocations that the child
+    // knows it has.
+    assert(ph.size() >= 1);
+    bool hit_first = false;
+    for (auto &payload : ph) {
+      if (!hit_first) {
+        target_zone_addr = payload.ptr;
+        hit_first = true;
+        continue;
+      }
+      auto pair = known_allocations.insert({payload.ptr, payload.size});
+      assert(pair.second); // Insertion should have happened
+    }
+    printf("Target process malloc zone is at 0x%lx" PRIxMAX "\n",
+           target_zone_addr);
+    printf("Target process reported the following allocations:\n");
+    for (auto &pair : known_allocations) {
+      printf("Target process ptr 0x%lx size: %lu\n", pair.first, pair.second);
+    }
+    return true;
+  }
+
+  typedef malloc_zone_t *(*get_default_zone_fn_ptr_ty)(void);
+
+  bool load_asan_dylib() {
+    // We have to set an environment variable to tell the ASan dylib to
+    // do init differently.
+    int success = setenv("APPLE_ASAN_INIT_FOR_DLOPEN", "1", /*overwrite=*/1);
+    if (success != 0) {
+      perror("Failed to set env");
+      return false;
+    }
+    void *dlh = dlopen(dylib_path.c_str(), RTLD_LAZY);
+    if (!dlh) {
+      log_failure("dlopen of %s failed: %s\n", dylib_path.c_str(),
+                  strerror(errno));
+      return false;
+    }
+
+    // Try to find and call `__sanitizer_mz_default_zone()` function
+    // which will tell us where ASan's malloc zone lives in the dylib.
+    void *fn_ptr = dlsym(dlh, "__sanitizer_mz_default_zone");
+    if (fn_ptr == nullptr) {
+      log_failure("dlsym failed:");
+      if (const char *error_msg = dlerror()) {
+        log_failure("%s", error_msg);
+      }
+      log_failure("\n");
+      return false;
+    }
+    auto get_default_zone =
+        reinterpret_cast<get_default_zone_fn_ptr_ty>(fn_ptr);
+    malloc_zone_t *asan_dylib_zone = get_default_zone();
+    printf("Found ASan malloc zone in asan dylib at:%p\n", asan_dylib_zone);
+    enumerator = asan_dylib_zone->introspect->enumerator;
+    printf("Found ASan malloc zone enumerator in asan dylib at:%p\n",
+           enumerator);
+    // Unset so that child processes don't also disable ASan.
+    success = unsetenv("APPLE_ASAN_INIT_FOR_DLOPEN");
+    if (success != 0) {
+      perror("Failed to set env");
+      return false;
+    }
+    return true;
+  }
+
+  bool sanity_check_result() {
+    printf("%lu allocations were found in the target\n",
+           enumerator_reported_allocations.size());
+
+    // We should have at least one allocation reported by the enumerator.
+    if (enumerator_reported_allocations.size() < 1) {
+      log_failure("Zero allocations found in target\n");
+      return false;
+    }
+
+    // known_allocations should be a subset of enumerator_reported_allocations
+    assert(known_allocations.size() > 0);
+    for (const auto &allocation_pair : known_allocations) {
+      auto addr = allocation_pair.first;
+      auto size = allocation_pair.second;
+      auto it_in_enumerator_reported_allocations =
+          enumerator_reported_allocations.find(addr);
+      if (it_in_enumerator_reported_allocations ==
+          enumerator_reported_allocations.end()) {
+        log_failure("A 'known allocation' (%p with size %" PRIdMAX
+                    " ) was not reported by the enumerator\n",
+                    addr, size);
+        return false;
+      }
+      size_t enumerator_reported_size =
+          it_in_enumerator_reported_allocations->second;
+      if (enumerator_reported_size != size) {
+        log_failure(
+            "Allocation size mismatch. The 'known allocation' was %" PRIdMAX
+            " bytes but the enumerator reported %" PRIdMAX " bytes\n",
+            size, enumerator_reported_size);
+        return false;
+      }
+    }
+    printf("All known %lu known allocations were reported by the enumerator\n ",
+           known_allocations.size());
+
+    // There should be no zero sized allocations or allocations in the zero-th
+    // page.
+    for (const auto &allocation_pair : enumerator_reported_allocations) {
+      auto addr = allocation_pair.first;
+      auto size = allocation_pair.second;
+      if (get_page_number(addr) == 0) {
+        log_failure("Enumerator reported allocation in zero-th page\n");
+        return false;
+      }
+      if (size == 0) {
+        log_failure("Enumerator reported zero size allocation\n");
+        return false;
+      }
+    }
+
+    // enumerator_reported_allocations should contain no overlapping
+    // allocations. O(N^2)
+    for (const auto &allocation_pair : enumerator_reported_allocations) {
+      for (const auto &other_allocation_pair :
+           enumerator_reported_allocations) {
+        Range first_range(allocation_pair.first, allocation_pair.second);
+        Range second_range(other_allocation_pair.first,
+                           other_allocation_pair.second);
+        if (first_range == second_range) {
+          // Skip the same element
+          continue;
+        }
+        if (first_range.overlaps(second_range)) {
+          log_failure("Detected overlap\n");
+          return false;
+        }
+      }
+    }
+    return true;
+  }
+
+  bool analyze() {
+    printf("Starting analysis in PID: %d\n", getpid());
+    if (!load_asan_dylib()) {
+      return false;
+    }
+
+    if (!launch_target()) {
+      return false;
+    }
+    bool success;
+
+    success = read_payload();
+    if (!success) {
+      return false;
+    }
+
+    // Freeze process at this point
+    success = freeze_target();
+    if (!success) {
+      halt_target();
+      return false;
+    }
+
+    // Call the enumerator making sure we see the known allocations
+    // that we were told about by the child.
+    //
+    // We ask for all range types so we can check we only report
+    // MALLOC_PTR_IN_USE_RANGE_TYPE regions.
+    assert(!failed());
+    assert(enumerator_reported_allocations.size() == 0);
+    auto error =
+        enumerator(task_for_target, (void *)this,
+                   MALLOC_PTR_IN_USE_RANGE_TYPE | MALLOC_PTR_REGION_RANGE_TYPE |
+                       MALLOC_ADMIN_REGION_RANGE_TYPE,
+                   target_zone_addr, simple_memory_reader, vm_range_recorder);
+    if (error != KERN_SUCCESS) {
+      log_failure("Failed to invoke enumerator: %s\n",
+                  mach_error_string(error));
+      halt_target();
+      return false;
+    }
+    if (failed()) {
+      log_failure("Detected failures\n");
+      halt_target();
+      return false;
+    }
+
+    success = sanity_check_result();
+    if (!success) {
+      log_failure("Sanity check failed\n");
+      halt_target();
+      return false;
+    }
+
+    // Unfreeze the process
+    success = unfreeze_target();
+    if (!success) {
+      halt_target();
+      return false;
+    }
+
+    halt_target();
+    return true;
+  }
+
+  kern_return_t map_memory(task_t remote_task, uintptr_t first_page_addr,
+                           size_t num_pages, uintptr_t &local_address,
+                           bool read_only = true) {
+    assert(num_pages > 0);
+    mach_msg_type_number_t mapped_size = 0; // size in bytes
+    vm_offset_t ptr_to_first_local_page = 0;
+    auto error = mach_vm_read(
+        /*target_task=*/remote_task,
+        /*address=*/first_page_addr,
+        /*size=*/num_pages * page_size,
+        /*data=*/&ptr_to_first_local_page,
+        /*dataCnt=*/&mapped_size);
+    if (error != KERN_SUCCESS) {
+      log_failure("Failed mach_vm_read: %s\n", mach_error_string(error));
+      return KERN_FAILURE;
+    }
+    assert(mapped_size == (num_pages * page_size));
+    static_assert(sizeof(local_address) == sizeof(ptr_to_first_local_page),
+                  "size mismatch");
+    local_address = ptr_to_first_local_page;
+    int page_flags = PROT_READ;
+    if (!read_only) {
+      page_flags |= PROT_WRITE;
+    }
+    error = mprotect(reinterpret_cast<void *>(ptr_to_first_local_page),
+                     page_size * num_pages, page_flags);
+    if (error != 0) {
+      log_failure("Failed to mprotect() allocated pages starting at %p: %s",
+                  ptr_to_first_local_page, strerror(errno));
+      return KERN_FAILURE;
+    }
+    return KERN_SUCCESS;
+  }
+
+  kern_return_t memory_reader(task_t remote_task, vm_address_t remote_address,
+                              vm_size_t size, void **local_memory) {
+    // Create region to represent the memory we want
+    auto object_range = Range(remote_address, size);
+
+    // Calculate the first page we want and how many we need
+    uintptr_t first_page_addr = round_down_to_page_addr(remote_address);
+    uintptr_t last_byte_addr = remote_address + size - 1;
+    assert(last_byte_addr >= first_page_addr);
+    size_t num_pages =
+        (get_page_number(last_byte_addr) - get_page_number(first_page_addr)) +
+        1;
+    assert(num_pages > 0);
+    size_t read_offset_from_first_page = remote_address - first_page_addr;
+    assert(read_offset_from_first_page < page_size);
+    uintptr_t ptr_to_first_local_page = 0;
+
+    // See if already have any overlapping pages already cached.
+    Range range_for_vm_region = Range(0, 0);
+    auto matching_regions = vm_cache.find_vm_regions_for(object_range);
+    for (auto it = matching_regions.first, ie = matching_regions.second;
+         it != ie; ++it) {
+      // See if Region fully encompasses object
+      if (it->first.contains(object_range)) {
+        range_for_vm_region = it->first;
+        ptr_to_first_local_page = it->second;
+        break;
+      }
+    }
+    if (range_for_vm_region.start == 0) {
+      // Didn't find a cached VM region. Allocate a new one
+      range_for_vm_region = Range(first_page_addr, num_pages * page_size);
+      auto success = map_memory(remote_task, first_page_addr, num_pages,
+                                ptr_to_first_local_page, /*read_only=*/false);
+      if (success != KERN_SUCCESS) {
+        *local_memory = 0;
+        return success;
+      }
+      assert(ptr_to_first_local_page);
+      // Cache the VM region
+      vm_cache.insert_vm_region(range_for_vm_region, ptr_to_first_local_page);
+    }
+    // Check the object is inside the VM region we got back.
+    assert(range_for_vm_region.contains(object_range));
+
+    // Compute the offset from the beginning of the VM region to the page we
+    // want
+    assert(first_page_addr >= range_for_vm_region.start);
+    size_t offset_from_vm_region_begin =
+        first_page_addr - range_for_vm_region.start;
+
+    uintptr_t local_object_addr = ptr_to_first_local_page +
+                                  offset_from_vm_region_begin +
+                                  read_offset_from_first_page;
+    assert(local_memory);
+    *local_memory = reinterpret_cast<void *>(local_object_addr);
+    return KERN_SUCCESS;
+  }
+};
+
+// This is global so that `simple_memory_reader` can get
+// at the analyzer.
+std::unique_ptr<Analyzer> globalAnalyzer;
+
+void custom_signal_handler(int sig_num, siginfo_t *info, void *uap) {
+  printf("Received signal: %d\n", sig_num);
+  if (globalAnalyzer) {
+    // We need to stop the target process if we're about to crash
+    // otherwise we'll leave a zombie process lying around.
+    printf("Trying to halt target process\n");
+    globalAnalyzer->halt_target();
+  }
+  printf("Exiting with failure.\n");
+  exit(1);
+}
+
+kern_return_t simple_memory_reader(task_t remote_task,
+                                   vm_address_t remote_address, vm_size_t size,
+                                   void **local_memory) {
+  return globalAnalyzer->memory_reader(remote_task, remote_address, size,
+                                       local_memory);
+}
+
+void vm_range_recorder(task_t, void *context, unsigned type,
+                       vm_range_t *range_begin, unsigned num_ranges) {
+  auto analyzer = reinterpret_cast<Analyzer *>(context);
+  if (type != MALLOC_PTR_IN_USE_RANGE_TYPE) {
+    // We should only see MALLOC_PTR_IN_USE_RANGE_TYPE ranges.
+    analyzer->log_failure("Saw unsupported range type %d\n", type);
+    return;
+  }
+  if (num_ranges == 0) {
+    analyzer->log_failure("num_ranges cannot be 0\n");
+    return;
+  }
+  for (unsigned index = 0; index < num_ranges; ++index) {
+    vm_range_t range = range_begin[index];
+    analyzer->record_range_from_enumerator(range);
+  }
+}
+
+int main(int argc, char **argv) {
+  if (argc != 3) {
+    usage_message(argv[0]);
+  }
+  globalAnalyzer.reset(new Analyzer(argv[1], argv[2]));
+  bool success = globalAnalyzer->analyze();
+  if (!success) {
+    fprintf(stderr, "Failure\n");
+  }
+  return !success;
+}
Index: test/asan/TestCases/Darwin/zone_enumeration/out_of_process/analyzer_entitlements.plist
===================================================================
--- /dev/null
+++ test/asan/TestCases/Darwin/zone_enumeration/out_of_process/analyzer_entitlements.plist
@@ -0,0 +1,11 @@
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+  <!-- On macOS Mojave and newer this entitlement is required to use
+  `task_for_pid()`. Normally it triggers a GUI prompt asking the user to
+  confirm this is okay. However the target process is codesigned to avoid this
+  (see `asan_prog_entitlements.plist`).  -->
+  <key>com.apple.security.cs.debugger</key>
+  <true/>
+</dict>
+</plist>
Index: test/asan/TestCases/Darwin/zone_enumeration/out_of_process/asan_prog.cc
===================================================================
--- /dev/null
+++ test/asan/TestCases/Darwin/zone_enumeration/out_of_process/asan_prog.cc
@@ -0,0 +1,155 @@
+// This process is the "target" porition of the test.
+//
+// This program is built with ASan and is the program
+// that will be examined by the "analysis" process.
+//
+// It detects (a reasonable subset of) live allocations in its self and finds
+// the address of its malloc zone and sends them to the "analysis" process and
+// then sleeps, awaiting examination by the "analysis" process.
+#include "protocol.h"
+#include <cstdio>
+#include <cstdlib>
+#include <fcntl.h>
+#include <malloc/malloc.h>
+#include <sanitizer/asan_interface.h>
+#include <string>
+#include <unistd.h>
+#include <unordered_map>
+
+static const int sleep_time = 5000;
+
+// This is a hack to gather the known allocations in this process.  We don't
+// use a std::unordered_map here because that would trigger calls to the
+// allocator inside the hook which we want to avoid.
+static const size_t kMaxAllocations = 50000;
+uintptr_t seen_malloc_addrs[kMaxAllocations];
+size_t seen_malloc_sizes[kMaxAllocations];
+uintptr_t seen_free_addrs[kMaxAllocations];
+bool hook_enabled = true;
+uint32_t current_malloc_index = 0;
+uint32_t current_free_index = 0;
+extern "C" void __sanitizer_malloc_hook(const volatile void *ptr, size_t size) {
+  if (!hook_enabled)
+    return;
+  if (current_malloc_index >= kMaxAllocations) {
+    // Can't record any more allocations
+    fprintf(stderr, "WARNING: Can't record any more allocations\n");
+    return;
+  }
+  seen_malloc_addrs[current_malloc_index] = reinterpret_cast<uintptr_t>(ptr);
+  seen_malloc_sizes[current_malloc_index] = size;
+  ++current_malloc_index;
+}
+extern "C" void __sanitizer_free_hook(const volatile void *ptr) {
+  if (!hook_enabled)
+    return;
+  if (current_free_index >= kMaxAllocations) {
+    // Can't record any more frees
+    fprintf(stderr, "WARNING: Can't record any more frees\n");
+    return;
+  }
+  seen_free_addrs[current_free_index] = reinterpret_cast<uintptr_t>(ptr);
+  ++current_free_index;
+}
+
+int main(int argc, char **argv) {
+  if (argc != 2) {
+    fprintf(stderr, "Must have 1 argument");
+    return 1;
+  }
+  printf("Started demo ASan application\n");
+  int write_fd = std::stoi(argv[1]);
+  printf("Write FD is %d\n", write_fd);
+
+  // Make sure we mark this file descriptor as close-on-exec.
+  // If we don't then when we fork (e.g. ASan spawning a symbolizer)
+  // then we might cause parent to hang because `close()` being called
+  // in this process doesn't actually send EOF to the parent.
+  if (fcntl(write_fd, F_SETFD, FD_CLOEXEC) == -1) {
+    fprintf(stderr, "Failed to set FD_CLOEXEC on fd\n");
+    return 1;
+  }
+
+  PayloadHolder ph;
+
+  // First find the ASan malloc zone
+  // and tell the parent about it.
+  auto mz = malloc_default_zone();
+  printf("Malloc Zone is at: %p\n", mz);
+  ph.push_back({reinterpret_cast<uintptr_t>(mz), 0});
+
+  // Deliberately perform some allocations that we will inform the parent about.
+  void *a = malloc(512); // Should be served by primary size class allocator
+  void *b =
+      malloc(1024 * 1024); // Should be served by secondary mmap based allocator
+  void *c = malloc(1);
+
+  // Stop recording allocations using the malloc hooks. Operating on
+  // `known_allocations` might trigger malloc/free so we don't want
+  // to record these.
+  hook_enabled = false;
+  std::unordered_map<uintptr_t, size_t> known_allocations;
+  // Populate map with observed mallocs
+  for (unsigned index = 0; index < current_malloc_index; ++index) {
+    known_allocations.insert(
+        {seen_malloc_addrs[index], seen_malloc_sizes[index]});
+  }
+  // Removed free'd allocations
+  for (unsigned index = 0; index < current_free_index; ++index) {
+    known_allocations.erase(seen_free_addrs[index]);
+  }
+  assert(known_allocations.find(reinterpret_cast<uintptr_t>(a)) !=
+         known_allocations.end());
+  assert(known_allocations.find(reinterpret_cast<uintptr_t>(b)) !=
+         known_allocations.end());
+  assert(known_allocations.find(reinterpret_cast<uintptr_t>(c)) !=
+         known_allocations.end());
+  if (known_allocations.size() < 3) {
+    fprintf(stderr, "known_allocations is too small\n");
+    return 1;
+  }
+
+  // FIXME(dliew): `__asan_describe_address` spawns the symbolizer and that can
+  // lead to hangs in llvm-lit if our parent process (analysis process)
+  // crashes. This is probably due to the Darwin symbolizer code giving the
+  // stderr filedescriptor to the symbolizer process which will prevent
+  // the underlying file object from being properly closed and EOF
+  // being sent to llvm-lit.
+  printf("First allocation:\n");
+  // __asan_describe_address(a);
+  printf("Second allocation:\n");
+  // __asan_describe_address(b);
+
+  // Now report the allocations to the parent
+  for (const auto &allocation : known_allocations) {
+    ph.push_back({allocation.first, allocation.second});
+  }
+
+  bool write_success = ph.writeToFd(write_fd);
+  if (!write_success) {
+    fprintf(stderr, "Failed to write to fd\n");
+    return 1;
+  }
+  // End communication with parent
+  int close_success = close(write_fd);
+  if (close_success != 0) {
+    fprintf(stderr, "Failed to close fd\n");
+  }
+
+  // Close stdout/stderr before going to sleep.
+  // If we don't do this, then if our parent crashes
+  // at this point then llvm-lit can hang because we still hold
+  // on to the stdout/stderr file descriptor it has
+  // (one end of a pipe in llvm-lit).
+  close(STDOUT_FILENO);
+  close(STDERR_FILENO);
+
+  // Sleep to give the parent time to freeze this process.
+  unsigned remaining = sleep_time;
+  unsigned taken = 0;
+  do {
+    taken = sleep(remaining);
+    remaining = (taken > remaining) ? 0 : (remaining - taken);
+  } while (remaining > 0);
+  return 0;
+}
Index: test/asan/TestCases/Darwin/zone_enumeration/out_of_process/asan_prog_entitlements.plist
===================================================================
--- /dev/null
+++ test/asan/TestCases/Darwin/zone_enumeration/out_of_process/asan_prog_entitlements.plist
@@ -0,0 +1,10 @@
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+  <!-- Bypasses the GUI prompt that is normally triggered by
+  `com.apple.security.cs.debugger` entitlement in analysis process.  This is
+  necessary for running the test on build bots.  -->
+  <key>com.apple.security.get-task-allow</key>
+  <true/>
+</dict>
+</plist>
Index: test/asan/TestCases/Darwin/zone_enumeration/out_of_process/enumerate_full_dylib.test
===================================================================
--- /dev/null
+++ test/asan/TestCases/Darwin/zone_enumeration/out_of_process/enumerate_full_dylib.test
@@ -0,0 +1,16 @@
+// This test performs out-of-process enumeration of an ASan process's
+// malloc zone.
+
+RUN: %clangxx -g %S/analysis_prog.cc -o %t-analyzer
+
+// FIXME: This is only needed for macos. It works by accident for ios like devices
+// because we copy to the device during the compile and the signed binary doesn't
+// actually end up on the device.
+RUN: codesign --force --entitlements %S/analyzer_entitlements.plist -s - %t-analyzer
+
+RUN: %clangxx_asan %S/asan_prog.cc -o %t-target
+
+// FIXME: This is only needed for macos.
+RUN: codesign --force --entitlements %S/asan_prog_entitlements.plist -s - %t-target
+
+RUN: %run %t-analyzer %shared_libasan %t-target
Index: test/asan/TestCases/Darwin/zone_enumeration/out_of_process/lit.local.cfg
===================================================================
--- /dev/null
+++ test/asan/TestCases/Darwin/zone_enumeration/out_of_process/lit.local.cfg
@@ -0,0 +1 @@
+config.suffixes = ['.test']
Index: test/asan/TestCases/Darwin/zone_enumeration/out_of_process/protocol.h
===================================================================
--- /dev/null
+++ test/asan/TestCases/Darwin/zone_enumeration/out_of_process/protocol.h
@@ -0,0 +1,90 @@
+#ifndef TEST_PROTOCOL_H
+#define TEST_PROTOCOL_H
+#include <inttypes.h>
+#include <list>
+#include <sstream>
+#include <stdint.h>
+#include <unistd.h>
+
+struct Payload {
+  uintptr_t ptr;
+  size_t size;
+  std::string to_str() const {
+    std::stringstream ss;
+    ss << "ptr: 0x" << std::hex << ptr << " size: " << std::dec << size;
+    return ss.str();
+  }
+};
+
+class PayloadHolder {
+  using DataTy = std::list<Payload>;
+  DataTy payloads;
+  bool debug = false;
+
+public:
+  PayloadHolder() {
+    if (getenv("ASAN_LEAKS_DEBUG")) {
+      debug = true;
+    }
+  }
+  using iterator = DataTy::iterator;
+  iterator begin() { return payloads.begin(); }
+  iterator end() { return payloads.end(); }
+
+  void push_back(Payload &&v) { payloads.push_back(v); }
+  void push_back(Payload &v) { payloads.push_back(v); }
+  size_t size() const { return payloads.size(); }
+
+  bool writeToFd(int fd) const {
+    if (debug)
+      printf("Sending %lu payloads\n", payloads.size());
+    for (auto &payload : payloads) {
+      ssize_t bytes_left_to_write = sizeof(Payload);
+      size_t ptr_offset = 0;
+      do {
+        auto bytes_written =
+            write(fd, reinterpret_cast<const uint8_t *>(&payload) + ptr_offset,
+                  bytes_left_to_write);
+        if (bytes_written == -1) {
+          return false;
+        }
+        bytes_left_to_write -= bytes_written;
+        ptr_offset += bytes_written;
+      } while (bytes_left_to_write > 0);
+    }
+    if (debug)
+      printf("Finished sending payload.\n");
+    return true;
+  }
+
+  bool readFromFd(int fd) {
+    assert(payloads.size() == 0);
+    while (true) {
+      Payload temp;
+      ssize_t bytes_left_to_read = sizeof(Payload);
+      size_t ptr_offset = 0;
+      do {
+        if (debug)
+          printf("Reading %ld bytes...", bytes_left_to_read);
+        auto bytes_read =
+            read(fd,
+                 reinterpret_cast<void *>(reinterpret_cast<uint8_t *>(&temp) +
+                                          ptr_offset),
+                 bytes_left_to_read);
+        if (debug)
+          printf("%ld\n", bytes_read);
+        if (bytes_read == -1)
+          return false;
+        if (bytes_read == 0)
+          return true; // EOF
+        bytes_left_to_read -= bytes_read;
+        ptr_offset += bytes_read;
+      } while (bytes_left_to_read > 0);
+      push_back(temp);
+      if (debug)
+        printf("%lu Payload received: %s\n", payloads.size(),
+               temp.to_str().c_str());
+    }
+  }
+};
+#endif