diff --git a/liblog/include/android/log.h b/liblog/include/android/log.h
index 7290789..39f885c 100644
--- a/liblog/include/android/log.h
+++ b/liblog/include/android/log.h
@@ -55,6 +55,7 @@
  */
 
 #include <stdarg.h>
+#include <stddef.h>
 
 #ifdef __cplusplus
 extern "C" {
@@ -152,6 +153,12 @@
 } log_id_t;
 
 /**
+ * Let the logging function choose the best log target.
+ * This is not part of the enum since adding either -1 or 0xFFFFFFFF forces the enum to be signed or
+ * unsigned, which breaks unfortunately common arithmetic against LOG_ID_MIN and LOG_ID_MAX. */
+#define LOG_ID_DEFAULT -1
+
+/**
  * Writes the constant string `text` to the log buffer `id`,
  * with priority `prio` and tag `tag`.
  *
@@ -170,6 +177,73 @@
 int __android_log_buf_print(int bufID, int prio, const char* tag, const char* fmt, ...)
     __attribute__((__format__(printf, 4, 5)));
 
+/**
+ * Logger data struct used for writing log messages to liblog via __android_log_write_logger_data()
+ * and sending log messages to user defined loggers specified in __android_log_set_logger().
+ */
+struct __android_logger_data {
+  size_t struct_size; /* Must be set to sizeof(__android_logger_data) and is used for versioning. */
+  int buffer_id;      /* log_id_t or -1 to represent 'default'. */
+  int priority;       /* android_LogPriority values. */
+  const char* tag;
+  const char* file;  /* Optional file name, may be set to nullptr. */
+  unsigned int line; /* Optional line number, ignore if file is nullptr. */
+};
+
+/**
+ * Writes the log message specified with logger_data and msg to the log.  logger_data includes
+ * additional file name and line number information that a logger may use.  logger_data is versioned
+ * for backwards compatibility.
+ */
+void __android_log_write_logger_data(struct __android_logger_data* logger_data, const char* msg);
+
+/**
+ * Prototype for the 'logger' function that is called for every log message.
+ */
+typedef void (*__android_logger_function)(const struct __android_logger_data* logger_data,
+                                          const char* message);
+
+/**
+ * Sets a user defined logger function.  All log messages sent to liblog will be set to the
+ * function pointer specified by logger for processing.
+ */
+void __android_log_set_logger(__android_logger_function logger);
+
+/**
+ * Writes the log message to logd.  This is an __android_logger_function and can be provided to
+ * __android_log_set_logger().  It is the default logger when running liblog on a device.
+ */
+void __android_log_logd_logger(const struct __android_logger_data* logger_data, const char* msg);
+
+/**
+ * Writes the log message to stderr.  This is an __android_logger_function and can be provided to
+ * __android_log_set_logger().  It is the default logger when running liblog on host.
+ */
+void __android_log_stderr_logger(const struct __android_logger_data* logger_data,
+                                 const char* message);
+
+/**
+ * Prototype for the 'abort' function that is called when liblog will abort due to
+ * __android_log_assert() failures.
+ */
+typedef void (*__android_aborter_function)(const char* abort_message);
+
+/**
+ * Sets a user defined aborter function that is called for __android_log_assert() failures.
+ */
+void __android_log_set_aborter(__android_aborter_function aborter);
+
+/**
+ * Calls the stored aborter function.  This allows for other logging libraries to use the same
+ * aborter function by calling this function in liblog.
+ */
+void __android_log_call_aborter(const char* abort_message);
+
+/**
+ * Sets android_set_abort_message() on device then aborts().  This is the default aborter.
+ */
+void __android_log_default_aborter(const char* abort_message);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/liblog/liblog.map.txt b/liblog/liblog.map.txt
index 65194ce..ae2a891 100644
--- a/liblog/liblog.map.txt
+++ b/liblog/liblog.map.txt
@@ -67,7 +67,14 @@
 
 LIGLOG_R { # introduced=30
   global:
+    __android_log_call_aborter;
+    __android_log_default_aborter;
+    __android_log_logd_logger;
     __android_log_security_bswrite; # apex
+    __android_log_set_aborter;
+    __android_log_set_logger;
+    __android_log_stderr_logger;
+    __android_log_write_logger_data;
 };
 
 LIBLOG_PRIVATE {
diff --git a/liblog/logger_write.cpp b/liblog/logger_write.cpp
index d6ef951..abc24ce 100644
--- a/liblog/logger_write.cpp
+++ b/liblog/logger_write.cpp
@@ -15,6 +15,7 @@
  */
 
 #include <errno.h>
+#include <inttypes.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/time.h>
@@ -23,11 +24,15 @@
 #include <android/set_abort_message.h>
 #endif
 
+#include <shared_mutex>
+
 #include <android-base/macros.h>
 #include <private/android_filesystem_config.h>
 #include <private/android_logger.h>
 
+#include "android/log.h"
 #include "logger.h"
+#include "rwlock.h"
 #include "uio.h"
 
 #if (FAKE_LOG_DEVICE == 0)
@@ -37,6 +42,14 @@
 #include "fake_log_device.h"
 #endif
 
+#if defined(__APPLE__)
+#include <pthread.h>
+#elif defined(__linux__) && !defined(__ANDROID__)
+#include <syscall.h>
+#elif defined(_WIN32)
+#include <windows.h>
+#endif
+
 #define LOG_BUF_SIZE 1024
 
 #if defined(__ANDROID__)
@@ -93,6 +106,41 @@
 #endif
 }
 
+#ifdef __ANDROID__
+static __android_logger_function logger_function = __android_log_logd_logger;
+#else
+static __android_logger_function logger_function = __android_log_stderr_logger;
+#endif
+static RwLock logger_function_lock;
+
+void __android_log_set_logger(__android_logger_function logger) {
+  auto lock = std::unique_lock{logger_function_lock};
+  logger_function = logger;
+}
+
+void __android_log_default_aborter(const char* abort_message) {
+#ifdef __ANDROID__
+  android_set_abort_message(abort_message);
+#else
+  UNUSED(abort_message);
+#endif
+  abort();
+}
+
+static __android_aborter_function aborter_function = __android_log_default_aborter;
+static RwLock aborter_function_lock;
+
+void __android_log_set_aborter(__android_aborter_function aborter) {
+  auto lock = std::unique_lock{aborter_function_lock};
+  aborter_function = aborter;
+}
+
+void __android_log_call_aborter(const char* abort_message) {
+  auto lock = std::shared_lock{aborter_function_lock};
+  aborter_function(abort_message);
+}
+
+#ifdef __ANDROID__
 static int write_to_log(log_id_t log_id, struct iovec* vec, size_t nr) {
   int ret, save_errno;
   struct timespec ts;
@@ -103,7 +151,6 @@
     return -EINVAL;
   }
 
-#if defined(__ANDROID__)
   clock_gettime(android_log_clockid(), &ts);
 
   if (log_id == LOG_ID_SECURITY) {
@@ -137,51 +184,106 @@
       return -EPERM;
     }
   }
-#else
-  /* simulate clock_gettime(CLOCK_REALTIME, &ts); */
-  {
-    struct timeval tv;
-    gettimeofday(&tv, NULL);
-    ts.tv_sec = tv.tv_sec;
-    ts.tv_nsec = tv.tv_usec * 1000;
-  }
-#endif
 
-  ret = 0;
-
-#if (FAKE_LOG_DEVICE == 0)
   ret = LogdWrite(log_id, &ts, vec, nr);
   PmsgWrite(log_id, &ts, vec, nr);
-#else
-  ret = FakeWrite(log_id, &ts, vec, nr);
-#endif
 
   errno = save_errno;
   return ret;
 }
+#else
+static int write_to_log(log_id_t, struct iovec*, size_t) {
+  // Non-Android text logs should go to __android_log_stderr_logger, not here.
+  // Non-Android binary logs are always dropped.
+  return 1;
+}
+#endif
+
+// Copied from base/threads.cpp
+static uint64_t GetThreadId() {
+#if defined(__BIONIC__)
+  return gettid();
+#elif defined(__APPLE__)
+  uint64_t tid;
+  pthread_threadid_np(NULL, &tid);
+  return tid;
+#elif defined(__linux__)
+  return syscall(__NR_gettid);
+#elif defined(_WIN32)
+  return GetCurrentThreadId();
+#endif
+}
+
+void __android_log_stderr_logger(const struct __android_logger_data* logger_data,
+                                 const char* message) {
+  struct tm now;
+  time_t t = time(nullptr);
+
+#if defined(_WIN32)
+  localtime_s(&now, &t);
+#else
+  localtime_r(&t, &now);
+#endif
+
+  char timestamp[32];
+  strftime(timestamp, sizeof(timestamp), "%m-%d %H:%M:%S", &now);
+
+  static const char log_characters[] = "XXVDIWEF";
+  static_assert(arraysize(log_characters) - 1 == ANDROID_LOG_SILENT,
+                "Mismatch in size of log_characters and values in android_LogPriority");
+  int priority =
+      logger_data->priority > ANDROID_LOG_SILENT ? ANDROID_LOG_FATAL : logger_data->priority;
+  char priority_char = log_characters[priority];
+  uint64_t tid = GetThreadId();
+
+  if (logger_data->file != nullptr) {
+    fprintf(stderr, "%s %c %s %5d %5" PRIu64 " %s:%u] %s\n",
+            logger_data->tag ? logger_data->tag : "nullptr", priority_char, timestamp, getpid(),
+            tid, logger_data->file, logger_data->line, message);
+  } else {
+    fprintf(stderr, "%s %c %s %5d %5" PRIu64 " %s\n",
+            logger_data->tag ? logger_data->tag : "nullptr", priority_char, timestamp, getpid(),
+            tid, message);
+  }
+}
+
+void __android_log_logd_logger(const struct __android_logger_data* logger_data,
+                               const char* message) {
+  int buffer_id = logger_data->buffer_id == LOG_ID_DEFAULT ? LOG_ID_MAIN : logger_data->buffer_id;
+
+  struct iovec vec[3];
+  vec[0].iov_base =
+      const_cast<unsigned char*>(reinterpret_cast<const unsigned char*>(&logger_data->priority));
+  vec[0].iov_len = 1;
+  vec[1].iov_base = const_cast<void*>(static_cast<const void*>(logger_data->tag));
+  vec[1].iov_len = strlen(logger_data->tag) + 1;
+  vec[2].iov_base = const_cast<void*>(static_cast<const void*>(message));
+  vec[2].iov_len = strlen(message) + 1;
+
+  write_to_log(static_cast<log_id_t>(buffer_id), vec, 3);
+}
 
 int __android_log_write(int prio, const char* tag, const char* msg) {
   return __android_log_buf_write(LOG_ID_MAIN, prio, tag, msg);
 }
 
-int __android_log_buf_write(int bufID, int prio, const char* tag, const char* msg) {
-  if (!tag) tag = "";
+void __android_log_write_logger_data(__android_logger_data* logger_data, const char* msg) {
+  if (logger_data->tag == nullptr) logger_data->tag = "";
 
 #if __BIONIC__
-  if (prio == ANDROID_LOG_FATAL) {
+  if (logger_data->priority == ANDROID_LOG_FATAL) {
     android_set_abort_message(msg);
   }
 #endif
 
-  struct iovec vec[3];
-  vec[0].iov_base = (unsigned char*)&prio;
-  vec[0].iov_len = 1;
-  vec[1].iov_base = (void*)tag;
-  vec[1].iov_len = strlen(tag) + 1;
-  vec[2].iov_base = (void*)msg;
-  vec[2].iov_len = strlen(msg) + 1;
+  auto lock = std::shared_lock{logger_function_lock};
+  logger_function(logger_data, msg);
+}
 
-  return write_to_log(static_cast<log_id_t>(bufID), vec, 3);
+int __android_log_buf_write(int bufID, int prio, const char* tag, const char* msg) {
+  __android_logger_data logger_data = {sizeof(__android_logger_data), bufID, prio, tag, nullptr, 0};
+  __android_log_write_logger_data(&logger_data, msg);
+  return 1;
 }
 
 int __android_log_vprint(int prio, const char* tag, const char* fmt, va_list ap) {
@@ -239,8 +341,8 @@
   TEMP_FAILURE_RETRY(write(2, "\n", 1));
 
   __android_log_write(ANDROID_LOG_FATAL, tag, buf);
-  abort(); /* abort so we have a chance to debug the situation */
-           /* NOTREACHED */
+  __android_log_call_aborter(buf);
+  abort();
 }
 
 int __android_log_bwrite(int32_t tag, const void* payload, size_t len) {
diff --git a/liblog/tests/Android.bp b/liblog/tests/Android.bp
index f58c524..3288954 100644
--- a/liblog/tests/Android.bp
+++ b/liblog/tests/Android.bp
@@ -54,6 +54,7 @@
     ],
     srcs: [
         "libc_test.cpp",
+        "liblog_global_state.cpp",
         "liblog_test.cpp",
         "log_id_test.cpp",
         "log_radio_test.cpp",
diff --git a/liblog/tests/liblog_global_state.cpp b/liblog/tests/liblog_global_state.cpp
new file mode 100644
index 0000000..23e8758
--- /dev/null
+++ b/liblog/tests/liblog_global_state.cpp
@@ -0,0 +1,155 @@
+/*
+ * Copyright (C) 2020 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.
+ */
+
+#define LOG_TAG "global_state_test_tag"
+
+#include <android-base/file.h>
+#include <android-base/logging.h>
+#include <android/log.h>
+
+#include <gtest/gtest.h>
+
+TEST(liblog_global_state, libbase_logs_with_libbase_SetLogger) {
+  using namespace android::base;
+  bool message_seen = false;
+  LogSeverity expected_severity = WARNING;
+  std::string expected_file = Basename(__FILE__);
+  unsigned int expected_line;
+  std::string expected_message = "libbase test message";
+
+  auto LoggerFunction = [&](LogId log_id, LogSeverity severity, const char* tag, const char* file,
+                            unsigned int line, const char* message) {
+    message_seen = true;
+    EXPECT_EQ(DEFAULT, log_id);
+    EXPECT_EQ(expected_severity, severity);
+    EXPECT_STREQ(LOG_TAG, tag);
+    EXPECT_EQ(expected_file, file);
+    EXPECT_EQ(expected_line, line);
+    EXPECT_EQ(expected_message, message);
+  };
+
+  SetLogger(LoggerFunction);
+
+  expected_line = __LINE__ + 1;
+  LOG(expected_severity) << expected_message;
+  EXPECT_TRUE(message_seen);
+}
+
+TEST(liblog_global_state, libbase_logs_with_liblog_set_logger) {
+  using namespace android::base;
+  // These must be static since they're used by the liblog logger function, which only accepts
+  // lambdas without captures.  The items used by the libbase logger are explicitly not static, to
+  // ensure that lambdas with captures do work there.
+  static bool message_seen = false;
+  static std::string expected_file = Basename(__FILE__);
+  static unsigned int expected_line;
+  static std::string expected_message = "libbase test message";
+
+  auto liblog_logger_function = [](const struct __android_logger_data* logger_data,
+                                   const char* message) {
+    message_seen = true;
+    EXPECT_EQ(sizeof(__android_logger_data), logger_data->struct_size);
+    EXPECT_EQ(LOG_ID_DEFAULT, logger_data->buffer_id);
+    EXPECT_EQ(ANDROID_LOG_WARN, logger_data->priority);
+    EXPECT_STREQ(LOG_TAG, logger_data->tag);
+    EXPECT_EQ(expected_file, logger_data->file);
+    EXPECT_EQ(expected_line, logger_data->line);
+    EXPECT_EQ(expected_message, message);
+  };
+
+  __android_log_set_logger(liblog_logger_function);
+
+  expected_line = __LINE__ + 1;
+  LOG(WARNING) << expected_message;
+  EXPECT_TRUE(message_seen);
+}
+
+TEST(liblog_global_state, liblog_logs_with_libbase_SetLogger) {
+  using namespace android::base;
+  bool message_seen = false;
+  std::string expected_message = "libbase test message";
+
+  auto LoggerFunction = [&](LogId log_id, LogSeverity severity, const char* tag, const char* file,
+                            unsigned int line, const char* message) {
+    message_seen = true;
+    EXPECT_EQ(MAIN, log_id);
+    EXPECT_EQ(WARNING, severity);
+    EXPECT_STREQ(LOG_TAG, tag);
+    EXPECT_EQ(nullptr, file);
+    EXPECT_EQ(0U, line);
+    EXPECT_EQ(expected_message, message);
+  };
+
+  SetLogger(LoggerFunction);
+
+  __android_log_buf_write(LOG_ID_MAIN, ANDROID_LOG_WARN, LOG_TAG, expected_message.c_str());
+  EXPECT_TRUE(message_seen);
+  message_seen = false;
+}
+
+TEST(liblog_global_state, liblog_logs_with_liblog_set_logger) {
+  using namespace android::base;
+  // These must be static since they're used by the liblog logger function, which only accepts
+  // lambdas without captures.  The items used by the libbase logger are explicitly not static, to
+  // ensure that lambdas with captures do work there.
+  static bool message_seen = false;
+  static int expected_buffer_id = LOG_ID_MAIN;
+  static int expected_priority = ANDROID_LOG_WARN;
+  static std::string expected_message = "libbase test message";
+
+  auto liblog_logger_function = [](const struct __android_logger_data* logger_data,
+                                   const char* message) {
+    message_seen = true;
+    EXPECT_EQ(sizeof(__android_logger_data), logger_data->struct_size);
+    EXPECT_EQ(expected_buffer_id, logger_data->buffer_id);
+    EXPECT_EQ(expected_priority, logger_data->priority);
+    EXPECT_STREQ(LOG_TAG, logger_data->tag);
+    EXPECT_STREQ(nullptr, logger_data->file);
+    EXPECT_EQ(0U, logger_data->line);
+    EXPECT_EQ(expected_message, message);
+  };
+
+  __android_log_set_logger(liblog_logger_function);
+
+  __android_log_buf_write(expected_buffer_id, expected_priority, LOG_TAG, expected_message.c_str());
+  EXPECT_TRUE(message_seen);
+}
+
+TEST(liblog_global_state, SetAborter_with_liblog) {
+  using namespace android::base;
+
+  std::string expected_message = "libbase test message";
+  static bool message_seen = false;
+  auto aborter_function = [&](const char* message) {
+    message_seen = true;
+    EXPECT_EQ(expected_message, message);
+  };
+
+  SetAborter(aborter_function);
+  LOG(FATAL) << expected_message;
+  EXPECT_TRUE(message_seen);
+  message_seen = false;
+
+  static std::string expected_message_static = "libbase test message";
+  auto liblog_aborter_function = [](const char* message) {
+    message_seen = true;
+    EXPECT_EQ(expected_message_static, message);
+  };
+  __android_log_set_aborter(liblog_aborter_function);
+  LOG(FATAL) << expected_message_static;
+  EXPECT_TRUE(message_seen);
+  message_seen = false;
+}
diff --git a/liblog/tests/liblog_test.cpp b/liblog/tests/liblog_test.cpp
index c402e20..9cae702 100644
--- a/liblog/tests/liblog_test.cpp
+++ b/liblog/tests/liblog_test.cpp
@@ -1074,7 +1074,6 @@
 
     // Once we've found our expected entry, break.
     if (len == LOGGER_ENTRY_MAX_PAYLOAD - sizeof(big_payload_tag)) {
-      EXPECT_EQ(ret, len + static_cast<ssize_t>(sizeof(big_payload_tag)));
       *found = true;
     }
   };