diff --git a/libc/bionic/stubs.cpp b/libc/bionic/stubs.cpp
index a539b34..1cab7d3 100644
--- a/libc/bionic/stubs.cpp
+++ b/libc/bionic/stubs.cpp
@@ -264,25 +264,30 @@
   return (unsigned)(appid + userid*AID_USER);
 }
 
-static void print_app_uid_name(uid_t  uid, char* buffer, int bufferlen) {
-  uid_t appid = uid % AID_USER;
-  uid_t userid = uid / AID_USER;
-
-  if (appid < AID_ISOLATED_START) {
-    if (appid < AID_APP) {
-      for (size_t n = 0; n < android_id_count; n++) {
-        if (android_ids[n].aid == appid) {
-          snprintf(buffer, bufferlen, "u%u_%s", userid, android_ids[n].name);
-          return;
-        }
+static void print_app_name_from_appid_userid(const uid_t appid,
+    const uid_t userid, char* buffer, const int bufferlen) {
+  if (appid >= AID_ISOLATED_START) {
+    snprintf(buffer, bufferlen, "u%u_i%u", userid, appid - AID_ISOLATED_START);
+  } else if (userid == 0 && appid >= AID_SHARED_GID_START) {
+    snprintf(buffer, bufferlen, "all_a%u", appid - AID_SHARED_GID_START);
+  } else if (appid < AID_APP) {
+    for (size_t n = 0; n < android_id_count; n++) {
+      if (android_ids[n].aid == appid) {
+        snprintf(buffer, bufferlen, "u%u_%s", userid, android_ids[n].name);
+        return;
       }
     }
-    snprintf(buffer, bufferlen, "u%u_a%u", userid, appid - AID_APP);
   } else {
-    snprintf(buffer, bufferlen, "u%u_i%u", userid, appid - AID_ISOLATED_START);
+    snprintf(buffer, bufferlen, "u%u_a%u", userid, appid - AID_APP);
   }
 }
 
+static void print_app_name_from_uid(const uid_t uid, char* buffer, const int bufferlen) {
+  const uid_t appid = uid % AID_USER;
+  const uid_t userid = uid / AID_USER;
+  return print_app_name_from_appid_userid(appid, userid, buffer, bufferlen);
+}
+
 // Translate a uid into the corresponding name.
 // 0 to AID_APP-1                   -> "system", "radio", etc.
 // AID_APP to AID_ISOLATED_START-1  -> u0_a1234
@@ -297,10 +302,18 @@
     return NULL;
   }
 
-  print_app_uid_name(uid, state->app_name_buffer_,
-                     sizeof(state->app_name_buffer_));
+  const uid_t appid = uid % AID_USER;
+  const uid_t userid = uid / AID_USER;
 
-  snprintf(state->dir_buffer_, sizeof(state->dir_buffer_), "/data");
+  print_app_name_from_appid_userid(appid, userid, state->app_name_buffer_,
+                                   sizeof(state->app_name_buffer_));
+
+  if (appid < AID_APP) {
+      snprintf(state->dir_buffer_, sizeof(state->dir_buffer_), "/");
+  } else {
+      snprintf(state->dir_buffer_, sizeof(state->dir_buffer_), "/data");
+  }
+
   snprintf(state->sh_buffer_, sizeof(state->sh_buffer_), "/system/bin/sh");
 
   pw->pw_name  = state->app_name_buffer_;
@@ -320,8 +333,8 @@
     return NULL;
   }
 
-  print_app_uid_name(gid, state->group_name_buffer_,
-                     sizeof(state->group_name_buffer_));
+  print_app_name_from_uid(gid, state->group_name_buffer_,
+                          sizeof(state->group_name_buffer_));
 
   group* gr = &state->group_;
   gr->gr_name   = state->group_name_buffer_;
diff --git a/tests/Android.mk b/tests/Android.mk
index 6d30ebb..be47585 100644
--- a/tests/Android.mk
+++ b/tests/Android.mk
@@ -23,6 +23,7 @@
     pthread_test.cpp \
     regex_test.cpp \
     string_test.cpp \
+    stubs_test.cpp \
 
 test_dynamic_ldflags = -Wl,--export-dynamic -Wl,-u,DlSymTestFunction
 test_dynamic_src_files = \
diff --git a/tests/stubs_test.cpp b/tests/stubs_test.cpp
new file mode 100644
index 0000000..d2d0ad8
--- /dev/null
+++ b/tests/stubs_test.cpp
@@ -0,0 +1,108 @@
+/*
+ * Copyright (C) 2012 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 <gtest/gtest.h>
+
+#include <sys/types.h>
+#include <sys/cdefs.h>
+#include <pwd.h>
+#include <errno.h>
+#include <limits.h>
+#include <unistd.h>
+
+#if __BIONIC__
+
+#define CHECK_GETPWNAM_FOR(username, uid, uid_type) \
+    SCOPED_TRACE(username); \
+    ASSERT_NO_FATAL_FAILURE(check_getpwnam(username, uid, uid_type));
+
+typedef enum {
+  TYPE_SYSTEM,
+  TYPE_APP
+} uid_type_t;
+
+static void check_getpwnam(const char* username, int uid, uid_type_t uid_type) {
+  errno = 0;
+  passwd* pwd = getpwuid(uid);
+  ASSERT_TRUE(pwd != NULL);
+  ASSERT_EQ(errno, 0);
+  EXPECT_STREQ(username, pwd->pw_name);
+  EXPECT_EQ(uid, pwd->pw_uid);
+  EXPECT_EQ(uid, pwd->pw_gid);
+
+  if (uid_type == TYPE_SYSTEM) {
+    EXPECT_STREQ("/", pwd->pw_dir);
+  } else if (uid_type == TYPE_APP) {
+    EXPECT_STREQ("/data", pwd->pw_dir);
+  }
+
+  EXPECT_STREQ("/system/bin/sh", pwd->pw_shell);
+}
+
+TEST(getpwnam, system_id_root) {
+  CHECK_GETPWNAM_FOR("root", 0, TYPE_SYSTEM);
+}
+
+TEST(getpwnam, system_id_system) {
+  CHECK_GETPWNAM_FOR("system", 1000, TYPE_SYSTEM);
+}
+
+TEST(getpwnam, app_id_radio) {
+  CHECK_GETPWNAM_FOR("radio", 1001, TYPE_SYSTEM);
+}
+
+TEST(getpwnam, app_id_nobody) {
+  CHECK_GETPWNAM_FOR("nobody", 9999, TYPE_SYSTEM);
+}
+
+TEST(getpwnam, app_id_all_a0) {
+  CHECK_GETPWNAM_FOR("all_a0", 50000, TYPE_APP);
+}
+
+TEST(getpwnam, app_id_u1_a40000) {
+  CHECK_GETPWNAM_FOR("u1_a40000", 150000, TYPE_APP);
+}
+
+TEST(getpwnam, app_id_u0_a0) {
+  CHECK_GETPWNAM_FOR("u0_a0", 10000, TYPE_APP);
+}
+
+TEST(getpwnam, app_id_u0_a1234) {
+  CHECK_GETPWNAM_FOR("u0_a1234", 11234, TYPE_APP);
+}
+
+TEST(getpwnam, app_id_u0_a9999) {
+  CHECK_GETPWNAM_FOR("u0_a9999", 19999, TYPE_APP);
+}
+
+// nonsensical, but expected
+TEST(getpwnam, app_id_u1_root) {
+  CHECK_GETPWNAM_FOR("u1_root", 100000, TYPE_SYSTEM);
+}
+
+TEST(getpwnam, app_id_u1_radio) {
+  CHECK_GETPWNAM_FOR("u1_radio", 101001, TYPE_SYSTEM);
+}
+
+TEST(getpwnam, app_id_u1_a0) {
+  CHECK_GETPWNAM_FOR("u1_a0", 110000, TYPE_APP);
+}
+
+TEST(getpwnam, app_id_u1_i0) {
+  CHECK_GETPWNAM_FOR("u1_i0", 199000, TYPE_APP);
+}
+
+#endif /* __BIONIC__ */