diff --git a/debuggerd/Android.mk b/debuggerd/Android.mk
index 607745d..e3bdd43 100644
--- a/debuggerd/Android.mk
+++ b/debuggerd/Android.mk
@@ -52,7 +52,7 @@
 
 include $(BUILD_EXECUTABLE)
 
-crasher_cppflags := $(common_cppflags) -fstack-protector-all -Wno-free-nonheap-object -Wno-date-time
+crasher_cppflags := $(common_cppflags) -O0 -fstack-protector-all -Wno-free-nonheap-object
 
 include $(CLEAR_VARS)
 LOCAL_SRC_FILES := crasher.cpp
@@ -65,7 +65,7 @@
 LOCAL_MODULE_PATH := $(TARGET_OUT_OPTIONAL_EXECUTABLES)
 LOCAL_MODULE_TAGS := optional
 LOCAL_CPPFLAGS := $(crasher_cppflags)
-LOCAL_SHARED_LIBRARIES := libcutils liblog
+LOCAL_SHARED_LIBRARIES := libbase liblog
 
 # The arm emulator has VFP but not VFPv3-D32.
 ifeq ($(ARCH_ARM_HAVE_VFP_D32),true)
@@ -91,7 +91,6 @@
 LOCAL_MODULE_TAGS := optional
 LOCAL_CPPFLAGS := $(crasher_cppflags) -DSTATIC_CRASHER
 LOCAL_FORCE_STATIC_EXECUTABLE := true
-LOCAL_SHARED_LIBRARIES := libcutils liblog
 
 # The arm emulator has VFP but not VFPv3-D32.
 ifeq ($(ARCH_ARM_HAVE_VFP_D32),true)
@@ -103,7 +102,7 @@
 LOCAL_MODULE_STEM_64 := static_crasher64
 LOCAL_MULTILIB := both
 
-LOCAL_STATIC_LIBRARIES := libdebuggerd_client libcutils liblog
+LOCAL_STATIC_LIBRARIES := libdebuggerd_client libbase liblog
 
 include $(BUILD_EXECUTABLE)
 
diff --git a/debuggerd/crasher.cpp b/debuggerd/crasher.cpp
index b0e8b17..e650f22 100644
--- a/debuggerd/crasher.cpp
+++ b/debuggerd/crasher.cpp
@@ -17,47 +17,43 @@
 #define LOG_TAG "crasher"
 
 #include <assert.h>
+#include <dirent.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <pthread.h>
-#include <sched.h>
 #include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <sys/cdefs.h>
 #include <sys/mman.h>
-#include <sys/ptrace.h>
-#include <sys/socket.h>
-#include <sys/wait.h>
 #include <unistd.h>
 
+// We test both kinds of logging.
 #include <android/log.h>
-#include <cutils/sockets.h>
+#include <android-base/logging.h>
 
 #if defined(STATIC_CRASHER)
 #include "debuggerd/client.h"
 #endif
 
-#ifndef __unused
-#define __unused __attribute__((__unused__))
-#endif
+#define noinline __attribute__((__noinline__))
 
-extern const char* __progname;
+// Avoid name mangling so that stacks are more readable.
+extern "C" {
 
-extern "C" void crash1(void);
-extern "C" void crashnostack(void);
+void crash1(void);
+void crashnostack(void);
 
-static int do_action(const char* arg);
+int do_action(const char* arg);
 
-static void maybe_abort() {
+noinline void maybe_abort() {
     if (time(0) != 42) {
         abort();
     }
 }
 
-static char* smash_stack_dummy_buf;
-__attribute__ ((noinline)) static void smash_stack_dummy_function(volatile int* plen) {
+char* smash_stack_dummy_buf;
+noinline void smash_stack_dummy_function(volatile int* plen) {
   smash_stack_dummy_buf[*plen] = 0;
 }
 
@@ -65,8 +61,8 @@
 // compiler generates the proper stack guards around this function.
 // Assign local array address to global variable to force stack guards.
 // Use another noinline function to corrupt the stack.
-__attribute__ ((noinline)) static int smash_stack(volatile int* plen) {
-    printf("%s: deliberately corrupting stack...\n", __progname);
+noinline int smash_stack(volatile int* plen) {
+    printf("%s: deliberately corrupting stack...\n", getprogname());
 
     char buf[128];
     smash_stack_dummy_buf = buf;
@@ -75,91 +71,107 @@
     return 0;
 }
 
-#if defined(__clang__)
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Winfinite-recursion"
-#endif
 
-static void* global = 0; // So GCC doesn't optimize the tail recursion out of overflow_stack.
+void* global = 0; // So GCC doesn't optimize the tail recursion out of overflow_stack.
 
-__attribute__((noinline)) static void overflow_stack(void* p) {
+noinline void overflow_stack(void* p) {
     void* buf[1];
     buf[0] = p;
     global = buf;
     overflow_stack(&buf);
 }
 
-#if defined(__clang__)
 #pragma clang diagnostic pop
-#endif
 
-static void *noisy(void *x)
-{
-    char c = (uintptr_t) x;
-    for(;;) {
-        usleep(250*1000);
-        write(2, &c, 1);
-        if(c == 'C') *((volatile unsigned*) 0) = 42;
-    }
-    return NULL;
+noinline void* thread_callback(void* raw_arg) {
+    const char* arg = reinterpret_cast<const char*>(raw_arg);
+    return reinterpret_cast<void*>(static_cast<uintptr_t>(do_action(arg)));
 }
 
-static int ctest()
-{
-    pthread_t thr;
-    pthread_attr_t attr;
-    pthread_attr_init(&attr);
-    pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
-    pthread_create(&thr, &attr, noisy, (void*) 'A');
-    pthread_create(&thr, &attr, noisy, (void*) 'B');
-    pthread_create(&thr, &attr, noisy, (void*) 'C');
-    for(;;) ;
-    return 0;
-}
-
-static void* thread_callback(void* raw_arg)
-{
-    return (void*) (uintptr_t) do_action((const char*) raw_arg);
-}
-
-static int do_action_on_thread(const char* arg)
-{
+noinline int do_action_on_thread(const char* arg) {
     pthread_t t;
-    pthread_create(&t, NULL, thread_callback, (void*) arg);
-    void* result = NULL;
+    pthread_create(&t, nullptr, thread_callback, const_cast<char*>(arg));
+    void* result = nullptr;
     pthread_join(t, &result);
-    return (int) (uintptr_t) result;
+    return reinterpret_cast<uintptr_t>(result);
 }
 
-__attribute__((noinline)) static int crash3(int a) {
-    *((int*) 0xdead) = a;
+noinline int crash3(int a) {
+    *reinterpret_cast<int*>(0xdead) = a;
     return a*4;
 }
 
-__attribute__((noinline)) static int crash2(int a) {
+noinline int crash2(int a) {
     a = crash3(a) + 2;
     return a*3;
 }
 
-__attribute__((noinline)) static int crash(int a) {
+noinline int crash(int a) {
     a = crash2(a) + 1;
     return a*2;
 }
 
-static void abuse_heap() {
+noinline void abuse_heap() {
     char buf[16];
-    free((void*) buf); // GCC is smart enough to warn about this, but we're doing it deliberately.
+    free(buf); // GCC is smart enough to warn about this, but we're doing it deliberately.
 }
 
-static void sigsegv_non_null() {
+noinline void sigsegv_non_null() {
     int* a = (int *)(&do_action);
     *a = 42;
 }
 
-static int do_action(const char* arg)
-{
-    fprintf(stderr, "%s: init pid=%d tid=%d\n", __progname, getpid(), gettid());
+noinline void fprintf_null() {
+    fprintf(nullptr, "oops");
+}
 
+noinline void readdir_null() {
+    readdir(nullptr);
+}
+
+noinline int strlen_null() {
+    char* sneaky_null = nullptr;
+    return strlen(sneaky_null);
+}
+
+static int usage() {
+    fprintf(stderr, "usage: %s KIND\n", getprogname());
+    fprintf(stderr, "\n");
+    fprintf(stderr, "where KIND is:\n");
+    fprintf(stderr, "  smash-stack           overwrite a -fstack-protector guard\n");
+    fprintf(stderr, "  stack-overflow        recurse until the stack overflows\n");
+    fprintf(stderr, "  heap-corruption       cause a libc abort by corrupting the heap\n");
+    fprintf(stderr, "  heap-usage            cause a libc abort by abusing a heap function\n");
+    fprintf(stderr, "  nostack               crash with a NULL stack pointer\n");
+    fprintf(stderr, "  abort                 call abort()\n");
+    fprintf(stderr, "  assert                call assert() without a function\n");
+    fprintf(stderr, "  assert2               call assert() with a function\n");
+    fprintf(stderr, "  exit                  call exit(1)\n");
+    fprintf(stderr, "  fortify               fail a _FORTIFY_SOURCE check\n");
+    fprintf(stderr, "  LOG_ALWAYS_FATAL      call liblog LOG_ALWAYS_FATAL\n");
+    fprintf(stderr, "  LOG_ALWAYS_FATAL_IF   call liblog LOG_ALWAYS_FATAL_IF\n");
+    fprintf(stderr, "  LOG-FATAL             call libbase LOG(FATAL)\n");
+    fprintf(stderr, "  SIGFPE                cause a SIGFPE\n");
+    fprintf(stderr, "  SIGSEGV               cause a SIGSEGV at address 0x0 (synonym: crash)\n");
+    fprintf(stderr, "  SIGSEGV-non-null      cause a SIGSEGV at a non-zero address\n");
+    fprintf(stderr, "  SIGSEGV-unmapped      mmap/munmap a region of memory and then attempt to access it\n");
+    fprintf(stderr, "  SIGTRAP               cause a SIGTRAP\n");
+    fprintf(stderr, "  fprintf-NULL          pass a null pointer to fprintf\n");
+    fprintf(stderr, "  readdir-NULL          pass a null pointer to readdir\n");
+    fprintf(stderr, "  strlen-NULL           pass a null pointer to strlen\n");
+    fprintf(stderr, "\n");
+    fprintf(stderr, "prefix any of the above with 'thread-' to run on a new thread\n");
+    fprintf(stderr, "prefix any of the above with 'exhaustfd-' to exhaust\n");
+    fprintf(stderr, "all available file descriptors before crashing.\n");
+    fprintf(stderr, "prefix any of the above with 'wait-' to wait until input is received on stdin\n");
+
+    return EXIT_FAILURE;
+}
+
+noinline int do_action(const char* arg) {
+    // Prefixes.
     if (!strncmp(arg, "wait-", strlen("wait-"))) {
       char buf[1];
       TEMP_FAILURE_RETRY(read(STDIN_FILENO, buf, sizeof(buf)));
@@ -172,82 +184,66 @@
       return do_action(arg + strlen("exhaustfd-"));
     } else if (!strncmp(arg, "thread-", strlen("thread-"))) {
         return do_action_on_thread(arg + strlen("thread-"));
-    } else if (!strcmp(arg, "SIGSEGV-non-null")) {
+    }
+
+    // Actions.
+    if (!strcasecmp(arg, "SIGSEGV-non-null")) {
         sigsegv_non_null();
-    } else if (!strcmp(arg, "smash-stack")) {
+    } else if (!strcasecmp(arg, "smash-stack")) {
         volatile int len = 128;
         return smash_stack(&len);
-    } else if (!strcmp(arg, "stack-overflow")) {
-        overflow_stack(NULL);
-    } else if (!strcmp(arg, "nostack")) {
+    } else if (!strcasecmp(arg, "stack-overflow")) {
+        overflow_stack(nullptr);
+    } else if (!strcasecmp(arg, "nostack")) {
         crashnostack();
-    } else if (!strcmp(arg, "ctest")) {
-        return ctest();
-    } else if (!strcmp(arg, "exit")) {
+    } else if (!strcasecmp(arg, "exit")) {
         exit(1);
-    } else if (!strcmp(arg, "crash") || !strcmp(arg, "SIGSEGV")) {
+    } else if (!strcasecmp(arg, "crash") || !strcmp(arg, "SIGSEGV")) {
         return crash(42);
-    } else if (!strcmp(arg, "abort")) {
+    } else if (!strcasecmp(arg, "abort")) {
         maybe_abort();
-    } else if (!strcmp(arg, "assert")) {
+    } else if (!strcasecmp(arg, "assert")) {
         __assert("some_file.c", 123, "false");
-    } else if (!strcmp(arg, "assert2")) {
+    } else if (!strcasecmp(arg, "assert2")) {
         __assert2("some_file.c", 123, "some_function", "false");
-    } else if (!strcmp(arg, "fortify")) {
+    } else if (!strcasecmp(arg, "fortify")) {
         char buf[10];
         __read_chk(-1, buf, 32, 10);
         while (true) pause();
-    } else if (!strcmp(arg, "LOG_ALWAYS_FATAL")) {
+    } else if (!strcasecmp(arg, "LOG(FATAL)")) {
+        LOG(FATAL) << "hello " << 123;
+    } else if (!strcasecmp(arg, "LOG_ALWAYS_FATAL")) {
         LOG_ALWAYS_FATAL("hello %s", "world");
-    } else if (!strcmp(arg, "LOG_ALWAYS_FATAL_IF")) {
+    } else if (!strcasecmp(arg, "LOG_ALWAYS_FATAL_IF")) {
         LOG_ALWAYS_FATAL_IF(true, "hello %s", "world");
-    } else if (!strcmp(arg, "SIGFPE")) {
+    } else if (!strcasecmp(arg, "SIGFPE")) {
         raise(SIGFPE);
         return EXIT_SUCCESS;
-    } else if (!strcmp(arg, "SIGTRAP")) {
+    } else if (!strcasecmp(arg, "SIGTRAP")) {
         raise(SIGTRAP);
         return EXIT_SUCCESS;
-    } else if (!strcmp(arg, "heap-usage")) {
+    } else if (!strcasecmp(arg, "fprintf-NULL")) {
+        fprintf_null();
+    } else if (!strcasecmp(arg, "readdir-NULL")) {
+        readdir_null();
+    } else if (!strcasecmp(arg, "strlen-NULL")) {
+        return strlen_null();
+    } else if (!strcasecmp(arg, "heap-usage")) {
         abuse_heap();
-    } else if (!strcmp(arg, "SIGSEGV-unmapped")) {
-        char* map = reinterpret_cast<char*>(mmap(NULL, sizeof(int), PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0));
+    } else if (!strcasecmp(arg, "SIGSEGV-unmapped")) {
+        char* map = reinterpret_cast<char*>(mmap(nullptr, sizeof(int), PROT_READ | PROT_WRITE,
+                                                 MAP_SHARED | MAP_ANONYMOUS, -1, 0));
         munmap(map, sizeof(int));
         map[0] = '8';
+    } else {
+        return usage();
     }
 
-    fprintf(stderr, "%s OP\n", __progname);
-    fprintf(stderr, "where OP is:\n");
-    fprintf(stderr, "  smash-stack           overwrite a stack-guard canary\n");
-    fprintf(stderr, "  stack-overflow        recurse until the stack overflows\n");
-    fprintf(stderr, "  heap-corruption       cause a libc abort by corrupting the heap\n");
-    fprintf(stderr, "  heap-usage            cause a libc abort by abusing a heap function\n");
-    fprintf(stderr, "  nostack               crash with a NULL stack pointer\n");
-    fprintf(stderr, "  ctest                 (obsoleted by thread-crash?)\n");
-    fprintf(stderr, "  exit                  call exit(1)\n");
-    fprintf(stderr, "  abort                 call abort()\n");
-    fprintf(stderr, "  assert                call assert() without a function\n");
-    fprintf(stderr, "  assert2               call assert() with a function\n");
-    fprintf(stderr, "  fortify               fail a _FORTIFY_SOURCE check\n");
-    fprintf(stderr, "  LOG_ALWAYS_FATAL      call LOG_ALWAYS_FATAL\n");
-    fprintf(stderr, "  LOG_ALWAYS_FATAL_IF   call LOG_ALWAYS_FATAL\n");
-    fprintf(stderr, "  SIGFPE                cause a SIGFPE\n");
-    fprintf(stderr, "  SIGSEGV               cause a SIGSEGV at address 0x0 (synonym: crash)\n");
-    fprintf(stderr, "  SIGSEGV-non-null      cause a SIGSEGV at a non-zero address\n");
-    fprintf(stderr, "  SIGSEGV-unmapped      mmap/munmap a region of memory and then attempt to access it\n");
-    fprintf(stderr, "  SIGTRAP               cause a SIGTRAP\n");
-    fprintf(stderr, "prefix any of the above with 'thread-' to not run\n");
-    fprintf(stderr, "on the process' main thread.\n");
-    fprintf(stderr, "prefix any of the above with 'exhaustfd-' to exhaust\n");
-    fprintf(stderr, "all available file descriptors before crashing.\n");
-    fprintf(stderr, "prefix any of the above with 'wait-' to wait until input is received on stdin\n");
-
+    fprintf(stderr, "%s: exiting normally!\n", getprogname());
     return EXIT_SUCCESS;
 }
 
-int main(int argc, char **argv)
-{
-    fprintf(stderr, "%s: built at " __TIME__ "!@\n", __progname);
-
+int main(int argc, char** argv) {
 #if defined(STATIC_CRASHER)
     debuggerd_callbacks_t callbacks = {
       .get_abort_message = []() {
@@ -265,11 +261,10 @@
     debuggerd_init(&callbacks);
 #endif
 
-    if (argc > 1) {
-        return do_action(argv[1]);
-    } else {
-        crash1();
-    }
+    if (argc == 1) crash1();
+    else if (argc == 2) return do_action(argv[1]);
 
-    return 0;
+    return usage();
 }
+
+};
diff --git a/include/cutils/multiuser.h b/include/cutils/multiuser.h
index 7e7f815..4f23776 100644
--- a/include/cutils/multiuser.h
+++ b/include/cutils/multiuser.h
@@ -23,19 +23,19 @@
 extern "C" {
 #endif
 
-// NOTE: keep in sync with android.os.UserId
-
-#define MULTIUSER_APP_PER_USER_RANGE 100000
-#define MULTIUSER_FIRST_SHARED_APPLICATION_GID 50000
-#define MULTIUSER_FIRST_APPLICATION_UID 10000
-
 typedef uid_t userid_t;
 typedef uid_t appid_t;
 
 extern userid_t multiuser_get_user_id(uid_t uid);
 extern appid_t multiuser_get_app_id(uid_t uid);
-extern uid_t multiuser_get_uid(userid_t userId, appid_t appId);
-extern appid_t multiuser_get_shared_app_gid(uid_t uid);
+
+extern uid_t multiuser_get_uid(userid_t user_id, appid_t app_id);
+
+extern gid_t multiuser_get_cache_gid(userid_t user_id, appid_t app_id);
+extern gid_t multiuser_get_shared_gid(userid_t user_id, appid_t app_id);
+
+/* TODO: switch callers over to multiuser_get_shared_gid() */
+extern gid_t multiuser_get_shared_app_gid(uid_t uid);
 
 #ifdef __cplusplus
 }
diff --git a/include/private/android_filesystem_config.h b/include/private/android_filesystem_config.h
index 3031562..f7cf9b8 100644
--- a/include/private/android_filesystem_config.h
+++ b/include/private/android_filesystem_config.h
@@ -157,15 +157,21 @@
 #define AID_MISC          9998  /* access to misc storage */
 #define AID_NOBODY        9999
 
-#define AID_APP          10000  /* first app user */
+#define AID_APP              10000 /* TODO: switch users over to AID_APP_START */
+#define AID_APP_START        10000 /* first app user */
+#define AID_APP_END          19999 /* last app user */
 
-#define AID_ISOLATED_START 99000 /* start of uids for fully isolated sandboxed processes */
-#define AID_ISOLATED_END   99999 /* end of uids for fully isolated sandboxed processes */
-
-#define AID_USER        100000  /* offset for uid ranges for each user */
+#define AID_CACHE_GID_START  20000 /* start of gids for apps to mark cached data */
+#define AID_CACHE_GID_END    29999 /* end of gids for apps to mark cached data */
 
 #define AID_SHARED_GID_START 50000 /* start of gids for apps in each user to share */
-#define AID_SHARED_GID_END   59999 /* start of gids for apps in each user to share */
+#define AID_SHARED_GID_END   59999 /* end of gids for apps in each user to share */
+
+#define AID_ISOLATED_START   99000 /* start of uids for fully isolated sandboxed processes */
+#define AID_ISOLATED_END     99999 /* end of uids for fully isolated sandboxed processes */
+
+#define AID_USER            100000 /* TODO: switch users over to AID_USER_OFFSET */
+#define AID_USER_OFFSET     100000 /* offset for uid ranges for each user */
 
 #if !defined(EXCLUDE_FS_CONFIG_STRUCTURES)
 /*
diff --git a/libcutils/multiuser.c b/libcutils/multiuser.c
index 0f4427b..0ef337d 100644
--- a/libcutils/multiuser.c
+++ b/libcutils/multiuser.c
@@ -15,21 +15,36 @@
  */
 
 #include <cutils/multiuser.h>
+#include <private/android_filesystem_config.h>
 
 userid_t multiuser_get_user_id(uid_t uid) {
-    return uid / MULTIUSER_APP_PER_USER_RANGE;
+    return uid / AID_USER_OFFSET;
 }
 
 appid_t multiuser_get_app_id(uid_t uid) {
-    return uid % MULTIUSER_APP_PER_USER_RANGE;
+    return uid % AID_USER_OFFSET;
 }
 
-uid_t multiuser_get_uid(userid_t userId, appid_t appId) {
-    return userId * MULTIUSER_APP_PER_USER_RANGE + (appId % MULTIUSER_APP_PER_USER_RANGE);
+uid_t multiuser_get_uid(userid_t user_id, appid_t app_id) {
+    return (user_id * AID_USER_OFFSET) + (app_id % AID_USER_OFFSET);
 }
 
-appid_t multiuser_get_shared_app_gid(uid_t id) {
-  return MULTIUSER_FIRST_SHARED_APPLICATION_GID + (id % MULTIUSER_APP_PER_USER_RANGE)
-          - MULTIUSER_FIRST_APPLICATION_UID;
+gid_t multiuser_get_cache_gid(userid_t user_id, appid_t app_id) {
+    if (app_id >= AID_APP_START && app_id <= AID_APP_END) {
+        return multiuser_get_uid(user_id, (app_id - AID_APP_START) + AID_CACHE_GID_START);
+    } else {
+        return -1;
+    }
+}
 
+gid_t multiuser_get_shared_gid(userid_t user_id, appid_t app_id) {
+    if (app_id >= AID_APP_START && app_id <= AID_APP_END) {
+        return multiuser_get_uid(user_id, (app_id - AID_APP_START) + AID_SHARED_GID_START);
+    } else {
+        return -1;
+    }
+}
+
+gid_t multiuser_get_shared_app_gid(uid_t uid) {
+    return multiuser_get_shared_gid(multiuser_get_user_id(uid), multiuser_get_app_id(uid));
 }
diff --git a/libcutils/tests/Android.bp b/libcutils/tests/Android.bp
index abe3c21..0b0dc09 100644
--- a/libcutils/tests/Android.bp
+++ b/libcutils/tests/Android.bp
@@ -26,7 +26,8 @@
                 "trace-dev_test.cpp",
                 "test_str_parms.cpp",
                 "android_get_control_socket_test.cpp",
-                "android_get_control_file_test.cpp"
+                "android_get_control_file_test.cpp",
+                "multiuser_test.cpp"
             ],
         },
 
diff --git a/libcutils/tests/multiuser_test.cpp b/libcutils/tests/multiuser_test.cpp
new file mode 100644
index 0000000..2307ea8
--- /dev/null
+++ b/libcutils/tests/multiuser_test.cpp
@@ -0,0 +1,67 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <cutils/multiuser.h>
+#include <gtest/gtest.h>
+
+TEST(MultiuserTest, TestMerge) {
+    EXPECT_EQ(0, multiuser_get_uid(0, 0));
+    EXPECT_EQ(1000, multiuser_get_uid(0, 1000));
+    EXPECT_EQ(10000, multiuser_get_uid(0, 10000));
+    EXPECT_EQ(50000, multiuser_get_uid(0, 50000));
+    EXPECT_EQ(1000000, multiuser_get_uid(10, 0));
+    EXPECT_EQ(1001000, multiuser_get_uid(10, 1000));
+    EXPECT_EQ(1010000, multiuser_get_uid(10, 10000));
+    EXPECT_EQ(1050000, multiuser_get_uid(10, 50000));
+}
+
+TEST(MultiuserTest, TestSplitUser) {
+    EXPECT_EQ(0, multiuser_get_user_id(0));
+    EXPECT_EQ(0, multiuser_get_user_id(1000));
+    EXPECT_EQ(0, multiuser_get_user_id(10000));
+    EXPECT_EQ(0, multiuser_get_user_id(50000));
+    EXPECT_EQ(10, multiuser_get_user_id(1000000));
+    EXPECT_EQ(10, multiuser_get_user_id(1001000));
+    EXPECT_EQ(10, multiuser_get_user_id(1010000));
+    EXPECT_EQ(10, multiuser_get_user_id(1050000));
+}
+
+TEST(MultiuserTest, TestSplitApp) {
+    EXPECT_EQ(0, multiuser_get_app_id(0));
+    EXPECT_EQ(1000, multiuser_get_app_id(1000));
+    EXPECT_EQ(10000, multiuser_get_app_id(10000));
+    EXPECT_EQ(50000, multiuser_get_app_id(50000));
+    EXPECT_EQ(0, multiuser_get_app_id(1000000));
+    EXPECT_EQ(1000, multiuser_get_app_id(1001000));
+    EXPECT_EQ(10000, multiuser_get_app_id(1010000));
+    EXPECT_EQ(50000, multiuser_get_app_id(1050000));
+}
+
+TEST(MultiuserTest, TestCache) {
+    EXPECT_EQ(-1, multiuser_get_cache_gid(0, 0));
+    EXPECT_EQ(-1, multiuser_get_cache_gid(0, 1000));
+    EXPECT_EQ(20000, multiuser_get_cache_gid(0, 10000));
+    EXPECT_EQ(-1, multiuser_get_cache_gid(0, 50000));
+    EXPECT_EQ(1020000, multiuser_get_cache_gid(10, 10000));
+}
+
+TEST(MultiuserTest, TestShared) {
+    EXPECT_EQ(-1, multiuser_get_shared_gid(0, 0));
+    EXPECT_EQ(-1, multiuser_get_shared_gid(0, 1000));
+    EXPECT_EQ(50000, multiuser_get_shared_gid(0, 10000));
+    EXPECT_EQ(-1, multiuser_get_shared_gid(0, 50000));
+    EXPECT_EQ(1050000, multiuser_get_shared_gid(10, 10000));
+}
diff --git a/logd/LogStatistics.cpp b/logd/LogStatistics.cpp
index bab87ba..3c8bd75 100644
--- a/logd/LogStatistics.cpp
+++ b/logd/LogStatistics.cpp
@@ -182,7 +182,7 @@
     }
 
     // Parse /data/system/packages.list
-    uid_t userId = uid % AID_USER;
+    uid_t userId = uid % AID_USER_OFFSET;
     const char *name = android::uidToName(userId);
     if (!name && (userId > (AID_SHARED_GID_START - AID_APP))) {
         name = android::uidToName(userId - (AID_SHARED_GID_START - AID_APP));
diff --git a/run-as/run-as.cpp b/run-as/run-as.cpp
index aec51f4..e7b8cc2 100644
--- a/run-as/run-as.cpp
+++ b/run-as/run-as.cpp
@@ -165,12 +165,12 @@
   if (setegid(old_egid) == -1) error(1, errno, "couldn't restore egid");
 
   // Verify that user id is not too big.
-  if ((UID_MAX - info.uid) / AID_USER < (uid_t)userId) {
+  if ((UID_MAX - info.uid) / AID_USER_OFFSET < (uid_t)userId) {
     error(1, 0, "user id too big: %d", userId);
   }
 
   // Calculate user app ID.
-  uid_t userAppId = (AID_USER * userId) + info.uid;
+  uid_t userAppId = (AID_USER_OFFSET * userId) + info.uid;
 
   // Reject system packages.
   if (userAppId < AID_APP) {