diff --git a/libc/Android.bp b/libc/Android.bp
index 07f5acb..13e17fe 100644
--- a/libc/Android.bp
+++ b/libc/Android.bp
@@ -1278,6 +1278,7 @@
         "bionic/getpriority.cpp",
         "bionic/gettid.cpp",
         "bionic/grp_pwd.cpp",
+        "bionic/grp_pwd_file.cpp",
         "bionic/iconv.cpp",
         "bionic/icu_wrappers.cpp",
         "bionic/ifaddrs.cpp",
diff --git a/libc/bionic/grp_pwd.cpp b/libc/bionic/grp_pwd.cpp
index 43a5032..952058f 100644
--- a/libc/bionic/grp_pwd.cpp
+++ b/libc/bionic/grp_pwd.cpp
@@ -44,6 +44,10 @@
 
 // Generated android_ids array
 #include "generated_android_ids.h"
+#include "grp_pwd_file.h"
+
+static PasswdFile vendor_passwd("/vendor/etc/passwd");
+static GroupFile vendor_group("/vendor/etc/group");
 
 // POSIX seems to envisage an implementation where the <pwd.h> functions are
 // implemented by brute-force searching with getpwent(3), and the <grp.h>
@@ -422,7 +426,11 @@
 
 static passwd* oem_id_to_passwd(uid_t uid, passwd_state_t* state) {
   if (!is_oem_id(uid)) {
-    return NULL;
+    return nullptr;
+  }
+
+  if (vendor_passwd.FindById(uid, state)) {
+    return &state->passwd_;
   }
 
   snprintf(state->name_buffer_, sizeof(state->name_buffer_), "oem_%u", uid);
@@ -440,7 +448,11 @@
 
 static group* oem_id_to_group(gid_t gid, group_state_t* state) {
   if (!is_oem_id(gid)) {
-    return NULL;
+    return nullptr;
+  }
+
+  if (vendor_group.FindById(gid, state)) {
+    return &state->group_;
   }
 
   snprintf(state->group_name_buffer_, sizeof(state->group_name_buffer_),
@@ -530,6 +542,13 @@
   if (pw != NULL) {
     return pw;
   }
+
+  if (vendor_passwd.FindByName(login, state)) {
+    if (is_oem_id(state->passwd_.pw_uid)) {
+      return &state->passwd_;
+    }
+  }
+
   // Handle OEM range.
   pw = oem_id_to_passwd(oem_id_from_name(login), state);
   if (pw != NULL) {
@@ -640,6 +659,13 @@
   if (grp != NULL) {
     return grp;
   }
+
+  if (vendor_group.FindByName(name, state)) {
+    if (is_oem_id(state->group_.gr_gid)) {
+      return &state->group_;
+    }
+  }
+
   // Handle OEM range.
   grp = oem_id_to_group(oem_id_from_name(name), state);
   if (grp != NULL) {
diff --git a/libc/bionic/grp_pwd_file.cpp b/libc/bionic/grp_pwd_file.cpp
new file mode 100644
index 0000000..911daea
--- /dev/null
+++ b/libc/bionic/grp_pwd_file.cpp
@@ -0,0 +1,326 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include "grp_pwd_file.h"
+
+#include <fcntl.h>
+#include <stdlib.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+
+#include "private/ErrnoRestorer.h"
+
+// This file mmap's /*/etc/passwd and /*/etc/group in order to return their contents without any
+// allocations.  Note that these files and the strings contained within them are explicitly not
+// null-terminated.  ':'s are used to deliminate fields and '\n's are used to deliminate lines.
+// There is a check that the file ends with '\n', such that terminating loops at '\n' ensures that
+// memory will be not ready before the mmap region.
+
+namespace {
+
+void CopyFieldToString(char* dest, const char* source, size_t max) {
+  while (*source != ':' && *source != '\n' && max > 1) {
+    *dest++ = *source++;
+    --max;
+  }
+  *dest = '\0';
+}
+
+bool FieldToUid(const char* field, uid_t* uid) {
+  if (field == nullptr) {
+    return false;
+  }
+
+  char* end = nullptr;
+  errno = 0;
+  uid_t result = strtoul(field, &end, 0);
+  if (errno != 0 || field == end || *end != ':') {
+    return false;
+  }
+  *uid = result;
+  return true;
+}
+
+// Returns a pointer to one past the end of line.
+const char* ParseLine(const char* begin, const char* end, const char** fields, size_t num_fields) {
+  size_t fields_written = 0;
+  const char* position = begin;
+  fields[fields_written++] = position;
+
+  while (position < end && fields_written < num_fields) {
+    if (*position == '\n') {
+      return position + 1;
+    }
+    if (*position == ':') {
+      fields[fields_written++] = position + 1;
+    }
+    position++;
+  }
+
+  while (position < end && *position != '\n') {
+    position++;
+  }
+
+  return position + 1;
+}
+
+struct PasswdLine {
+  const char* name() const {
+    return fields[0];
+  }
+  // Password is not supported.
+  const char* uid() const {
+    return fields[2];
+  }
+  const char* gid() const {
+    return fields[3];
+  }
+  // User Info is not supported
+  const char* dir() const {
+    return fields[5];
+  }
+  const char* shell() const {
+    return fields[6];
+  }
+
+  bool ToPasswdState(passwd_state_t* passwd_state) {
+    if (name() == nullptr || dir() == nullptr || shell() == nullptr) {
+      return false;
+    }
+
+    uid_t uid;
+    if (!FieldToUid(this->uid(), &uid)) {
+      return false;
+    }
+
+    gid_t gid;
+    if (!FieldToUid(this->gid(), &gid)) {
+      return false;
+    }
+
+    passwd_state->passwd_.pw_uid = uid;
+    passwd_state->passwd_.pw_gid = gid;
+
+    CopyFieldToString(passwd_state->name_buffer_, name(), sizeof(passwd_state->name_buffer_));
+    passwd_state->passwd_.pw_name = passwd_state->name_buffer_;
+
+    passwd_state->passwd_.pw_passwd = nullptr;
+
+#ifdef __LP64__
+    passwd_state->passwd_.pw_gecos = nullptr;
+#endif
+
+    CopyFieldToString(passwd_state->dir_buffer_, dir(), sizeof(passwd_state->dir_buffer_));
+    passwd_state->passwd_.pw_dir = passwd_state->dir_buffer_;
+
+    CopyFieldToString(passwd_state->sh_buffer_, shell(), sizeof(passwd_state->sh_buffer_));
+    passwd_state->passwd_.pw_shell = passwd_state->sh_buffer_;
+
+    return true;
+  }
+
+  static constexpr size_t kNumFields = 7;
+  const char* fields[kNumFields] = {};
+};
+
+struct GroupLine {
+  const char* name() const {
+    return fields[0];
+  }
+  // Password is not supported.
+  const char* gid() const {
+    return fields[2];
+  }
+  // User list is not supported (returns simply name)
+
+  bool ToGroupState(group_state_t* group_state) {
+    if (name() == nullptr || gid() == nullptr) {
+      return false;
+    }
+
+    gid_t gid;
+    if (!FieldToUid(this->gid(), &gid)) {
+      return false;
+    }
+
+    group_state->group_.gr_gid = gid;
+
+    CopyFieldToString(group_state->group_name_buffer_, name(),
+                      sizeof(group_state->group_name_buffer_));
+    group_state->group_.gr_name = group_state->group_name_buffer_;
+
+    group_state->group_.gr_passwd = nullptr;
+
+    group_state->group_.gr_mem = group_state->group_members_;
+    group_state->group_.gr_mem[0] = group_state->group_.gr_name;
+    group_state->group_.gr_mem[1] = nullptr;
+
+    return true;
+  }
+
+  static constexpr size_t kNumFields = 4;
+  const char* fields[kNumFields] = {};
+};
+
+}  // namespace
+
+MmapFile::MmapFile(const char* filename) : filename_(filename) {
+  lock_.init(false);
+}
+
+MmapFile::~MmapFile() {
+  if (status_ == FileStatus::Initialized) {
+    size_t size = end_ - start_ + 1;
+    munmap(const_cast<char*>(start_), size);
+  }
+}
+
+bool MmapFile::GetFile(const char** start, const char** end) {
+  LockGuard guard(lock_);
+  if (status_ == FileStatus::Initialized) {
+    *start = start_;
+    *end = end_;
+    return true;
+  }
+  if (status_ == FileStatus::Error) {
+    return false;
+  }
+
+  if (!DoMmap()) {
+    status_ = FileStatus::Error;
+    return false;
+  }
+
+  status_ = FileStatus::Initialized;
+  *start = start_;
+  *end = end_;
+  return true;
+}
+
+bool MmapFile::DoMmap() {
+  int fd = open(filename_, O_CLOEXEC | O_NOFOLLOW | O_RDONLY);
+
+  struct stat fd_stat;
+  if (fstat(fd, &fd_stat) == -1) {
+    close(fd);
+    return false;
+  }
+
+  auto mmap_size = fd_stat.st_size;
+
+  const void* map_result = mmap(nullptr, mmap_size, PROT_READ, MAP_SHARED, fd, 0);
+  close(fd);
+
+  if (map_result == MAP_FAILED) {
+    return false;
+  }
+
+  start_ = static_cast<const char*>(map_result);
+  end_ = start_ + mmap_size - 1;
+
+  return *end_ == '\n';
+}
+
+template <typename Line, typename Predicate>
+bool MmapFile::Find(Line* line, Predicate predicate) {
+  const char* start;
+  const char* end;
+  if (!GetFile(&start, &end)) {
+    return false;
+  }
+
+  const char* line_beginning = start;
+
+  while (line_beginning < end) {
+    line_beginning = ParseLine(line_beginning, end, line->fields, line->kNumFields);
+    if (predicate(line)) return true;
+  }
+
+  return false;
+}
+
+template <typename Line>
+bool MmapFile::FindById(uid_t uid, Line* line) {
+  return Find(line, [uid](const auto& line) {
+    uid_t line_id;
+    if (!FieldToUid(line->fields[2], &line_id)) {
+      return false;
+    }
+
+    return line_id == uid;
+  });
+}
+
+template <typename Line>
+bool MmapFile::FindByName(const char* name, Line* line) {
+  return Find(line, [name](const auto& line) {
+    const char* line_name = line->fields[0];
+    if (line_name == nullptr) {
+      return false;
+    }
+
+    const char* match_name = name;
+    while (*line_name != '\n' && *line_name != ':' && *match_name != '\0') {
+      if (*line_name++ != *match_name++) {
+        return false;
+      }
+    }
+
+    return *line_name == ':' && *match_name == '\0';
+  });
+}
+
+PasswdFile::PasswdFile(const char* filename) : mmap_file_(filename) {
+}
+
+bool PasswdFile::FindById(uid_t id, passwd_state_t* passwd_state) {
+  ErrnoRestorer errno_restorer;
+  PasswdLine passwd_line;
+  return mmap_file_.FindById(id, &passwd_line) && passwd_line.ToPasswdState(passwd_state);
+}
+
+bool PasswdFile::FindByName(const char* name, passwd_state_t* passwd_state) {
+  ErrnoRestorer errno_restorer;
+  PasswdLine passwd_line;
+  return mmap_file_.FindByName(name, &passwd_line) && passwd_line.ToPasswdState(passwd_state);
+}
+
+GroupFile::GroupFile(const char* filename) : mmap_file_(filename) {
+}
+
+bool GroupFile::FindById(gid_t id, group_state_t* group_state) {
+  ErrnoRestorer errno_restorer;
+  GroupLine group_line;
+  return mmap_file_.FindById(id, &group_line) && group_line.ToGroupState(group_state);
+}
+
+bool GroupFile::FindByName(const char* name, group_state_t* group_state) {
+  ErrnoRestorer errno_restorer;
+  GroupLine group_line;
+  return mmap_file_.FindByName(name, &group_line) && group_line.ToGroupState(group_state);
+}
diff --git a/libc/bionic/grp_pwd_file.h b/libc/bionic/grp_pwd_file.h
new file mode 100644
index 0000000..ae8cd98
--- /dev/null
+++ b/libc/bionic/grp_pwd_file.h
@@ -0,0 +1,97 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef GRP_PWD_FILE_H
+#define GRP_PWD_FILE_H
+
+#include <grp.h>
+#include <pwd.h>
+
+#include "private/bionic_lock.h"
+#include "private/bionic_macros.h"
+#include "private/grp_pwd.h"
+
+class MmapFile {
+ public:
+  MmapFile(const char* filename);
+  ~MmapFile();
+
+  template <typename Line>
+  bool FindById(uid_t uid, Line* line);
+  template <typename Line>
+  bool FindByName(const char* name, Line* line);
+
+  DISALLOW_COPY_AND_ASSIGN(MmapFile);
+
+ private:
+  enum class FileStatus {
+    Uninitialized,
+    Initialized,
+    Error,
+  };
+
+  bool GetFile(const char** start, const char** end);
+  bool DoMmap();
+
+  template <typename Line, typename Predicate>
+  bool Find(Line* line, Predicate predicate);
+
+  FileStatus status_ = FileStatus::Uninitialized;
+  Lock lock_;
+  const char* filename_ = nullptr;
+  const char* start_ = nullptr;
+  const char* end_ = nullptr;
+};
+
+class PasswdFile {
+ public:
+  PasswdFile(const char* filename);
+
+  bool FindById(uid_t id, passwd_state_t* passwd_state);
+  bool FindByName(const char* name, passwd_state_t* passwd_state);
+
+  DISALLOW_COPY_AND_ASSIGN(PasswdFile);
+
+ private:
+  MmapFile mmap_file_;
+};
+
+class GroupFile {
+ public:
+  GroupFile(const char* filename);
+
+  bool FindById(gid_t id, group_state_t* group_state);
+  bool FindByName(const char* name, group_state_t* group_state);
+
+  DISALLOW_COPY_AND_ASSIGN(GroupFile);
+
+ private:
+  MmapFile mmap_file_;
+};
+
+#endif
diff --git a/libc/private/bionic_lock.h b/libc/private/bionic_lock.h
index b389247..54168d3 100644
--- a/libc/private/bionic_lock.h
+++ b/libc/private/bionic_lock.h
@@ -76,4 +76,19 @@
   }
 };
 
+class LockGuard {
+ public:
+  LockGuard(Lock& lock) : lock_(lock) {
+    lock_.lock();
+  }
+  ~LockGuard() {
+    lock_.unlock();
+  }
+
+  DISALLOW_COPY_AND_ASSIGN(LockGuard);
+
+ private:
+  Lock& lock_;
+};
+
 #endif  // _BIONIC_LOCK_H
diff --git a/tests/Android.bp b/tests/Android.bp
index 56a4722..5483b6a 100644
--- a/tests/Android.bp
+++ b/tests/Android.bp
@@ -75,6 +75,7 @@
         "getcwd_test.cpp",
         "glob_test.cpp",
         "grp_pwd_test.cpp",
+        "grp_pwd_file_test.cpp",
         "iconv_test.cpp",
         "ifaddrs_test.cpp",
         "inttypes_test.cpp",
diff --git a/tests/grp_pwd_file_test.cpp b/tests/grp_pwd_file_test.cpp
new file mode 100644
index 0000000..79f9a10
--- /dev/null
+++ b/tests/grp_pwd_file_test.cpp
@@ -0,0 +1,185 @@
+/*
+ * Copyright (C) 2018 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 <unistd.h>
+
+#include <gtest/gtest.h>
+
+#include "TemporaryFile.h"
+
+#if defined(__BIONIC__)
+#include "../libc/bionic/grp_pwd_file.cpp"
+
+void FindAndCheckPasswdEntry(PasswdFile* file, const char* name, uid_t uid, gid_t gid,
+                             const char* dir, const char* shell) {
+  passwd_state_t name_passwd_state;
+  ASSERT_TRUE(file->FindByName(name, &name_passwd_state)) << name;
+
+  passwd& name_passwd = name_passwd_state.passwd_;
+  EXPECT_STREQ(name, name_passwd.pw_name);
+  EXPECT_EQ(nullptr, name_passwd.pw_passwd);
+  EXPECT_EQ(uid, name_passwd.pw_uid);
+  EXPECT_EQ(gid, name_passwd.pw_gid);
+  EXPECT_EQ(nullptr, name_passwd.pw_gecos);
+  EXPECT_STREQ(dir, name_passwd.pw_dir);
+  EXPECT_STREQ(shell, name_passwd.pw_shell);
+
+  passwd_state_t id_passwd_state;
+  ASSERT_TRUE(file->FindById(uid, &id_passwd_state)) << uid;
+
+  passwd& id_passwd = id_passwd_state.passwd_;
+  EXPECT_STREQ(name, id_passwd.pw_name);
+  EXPECT_EQ(nullptr, id_passwd.pw_passwd);
+  EXPECT_EQ(uid, id_passwd.pw_uid);
+  EXPECT_EQ(gid, id_passwd.pw_gid);
+  EXPECT_EQ(nullptr, id_passwd.pw_gecos);
+  EXPECT_STREQ(dir, id_passwd.pw_dir);
+  EXPECT_STREQ(shell, id_passwd.pw_shell);
+}
+
+void FindAndCheckGroupEntry(GroupFile* file, const char* name, gid_t gid) {
+  group_state_t name_group_state;
+  ASSERT_TRUE(file->FindByName(name, &name_group_state)) << name;
+
+  group& name_group = name_group_state.group_;
+  EXPECT_STREQ(name, name_group.gr_name);
+  EXPECT_EQ(nullptr, name_group.gr_passwd);
+  EXPECT_EQ(gid, name_group.gr_gid);
+  EXPECT_EQ(name_group.gr_name, name_group.gr_mem[0]);
+  EXPECT_EQ(nullptr, name_group.gr_mem[1]);
+
+  group_state_t id_group_state;
+  ASSERT_TRUE(file->FindById(gid, &id_group_state)) << gid;
+
+  group& id_group = id_group_state.group_;
+  EXPECT_STREQ(name, id_group.gr_name);
+  EXPECT_EQ(nullptr, id_group.gr_passwd);
+  EXPECT_EQ(gid, id_group.gr_gid);
+  EXPECT_EQ(id_group.gr_name, id_group.gr_mem[0]);
+  EXPECT_EQ(nullptr, id_group.gr_mem[1]);
+}
+
+#endif  // __BIONIC__
+
+TEST(grp_pwd_file, passwd_file_one_entry) {
+#if defined(__BIONIC__)
+  TemporaryFile file;
+  ASSERT_NE(-1, file.fd);
+  static const char test_string[] = "name:password:1:2:user_info:dir:shell\n";
+  write(file.fd, test_string, sizeof(test_string) - 1);
+
+  PasswdFile passwd_file(file.filename);
+
+  FindAndCheckPasswdEntry(&passwd_file, "name", 1, 2, "dir", "shell");
+
+  EXPECT_FALSE(passwd_file.FindByName("not_name", nullptr));
+  EXPECT_FALSE(passwd_file.FindById(3, nullptr));
+
+#else   // __BIONIC__
+  GTEST_LOG_(INFO) << "This test does nothing.\n";
+#endif  // __BIONIC__
+}
+
+TEST(grp_pwd_file, group_file_one_entry) {
+#if defined(__BIONIC__)
+  TemporaryFile file;
+  ASSERT_NE(-1, file.fd);
+  static const char test_string[] = "name:password:1:one,two,three\n";
+  write(file.fd, test_string, sizeof(test_string) - 1);
+
+  GroupFile group_file(file.filename);
+
+  FindAndCheckGroupEntry(&group_file, "name", 1);
+
+  EXPECT_FALSE(group_file.FindByName("not_name", nullptr));
+  EXPECT_FALSE(group_file.FindById(3, nullptr));
+
+#else   // __BIONIC__
+  GTEST_LOG_(INFO) << "This test does nothing.\n";
+#endif  // __BIONIC__
+}
+
+TEST(grp_pwd_file, passwd_file_many_entries) {
+#if defined(__BIONIC__)
+  TemporaryFile file;
+  ASSERT_NE(-1, file.fd);
+  static const char test_string[] =
+      "first:x:1:2::dir:shell\n"
+      "abc1::3:4::def:abc\n"
+      "abc2::5:4:abc::abc\n"
+      "abc3::7:4:abc:def:\n"
+      "abc4::9:4:::abc\n"
+      "abc5::11:4:abc:def:abc\n"
+      "middle-ish::13:4::/:/system/bin/sh\n"
+      "abc7::15:4:abc::\n"
+      "abc8::17:4:::\n"
+      "abc9::19:4:abc:def:abc\n"
+      "abc10::21:4:abc:def:abc\n"
+      "abc11::23:4:abc:def:abc\n"
+      "abc12::25:4:abc:def:abc\n"
+      "abc13::27:4:abc:def:abc\n"
+      "last::29:4::last_user_dir:last_user_shell\n";
+
+  write(file.fd, test_string, sizeof(test_string) - 1);
+
+  PasswdFile passwd_file(file.filename);
+
+  FindAndCheckPasswdEntry(&passwd_file, "first", 1, 2, "dir", "shell");
+  FindAndCheckPasswdEntry(&passwd_file, "middle-ish", 13, 4, "/", "/system/bin/sh");
+  FindAndCheckPasswdEntry(&passwd_file, "last", 29, 4, "last_user_dir", "last_user_shell");
+
+  EXPECT_FALSE(passwd_file.FindByName("not_name", nullptr));
+  EXPECT_FALSE(passwd_file.FindById(50, nullptr));
+
+#else   // __BIONIC__
+  GTEST_LOG_(INFO) << "This test does nothing.\n";
+#endif  // __BIONIC__
+}
+
+TEST(grp_pwd_file, group_file_many_entries) {
+#if defined(__BIONIC__)
+  TemporaryFile file;
+  ASSERT_NE(-1, file.fd);
+  static const char test_string[] =
+      "first:password:1:one,two,three\n"
+      "abc:def:2:group1,group2,group3\n"
+      "abc:def:3:\n"
+      "abc:def:4:\n"
+      "abc:def:5:\n"
+      "middle-ish:def_a_password_that_is_over_32_characters_long:6:\n"
+      "abc:def:7:\n"
+      "abc:def:8:\n"
+      "abc:def:20:\n"
+      "abc:def:25:\n"
+      "abc:def:27:\n"
+      "abc:def:52:\n"
+      "last::800:\n";
+
+  write(file.fd, test_string, sizeof(test_string) - 1);
+
+  GroupFile group_file(file.filename);
+
+  FindAndCheckGroupEntry(&group_file, "first", 1);
+  FindAndCheckGroupEntry(&group_file, "middle-ish", 6);
+  FindAndCheckGroupEntry(&group_file, "last", 800);
+
+  EXPECT_FALSE(group_file.FindByName("not_name", nullptr));
+  EXPECT_FALSE(group_file.FindById(799, nullptr));
+
+#else   // __BIONIC__
+  GTEST_LOG_(INFO) << "This test does nothing.\n";
+#endif  // __BIONIC__
+}