Merge "Libbase: NOLINT legacy unique_fd operator int"
diff --git a/fs_mgr/fs_mgr.cpp b/fs_mgr/fs_mgr.cpp
index 943fe10..9f6c550 100644
--- a/fs_mgr/fs_mgr.cpp
+++ b/fs_mgr/fs_mgr.cpp
@@ -523,13 +523,13 @@
}
// Mark the given block device as read-only, using the BLKROSET ioctl.
-bool fs_mgr_set_blk_ro(const std::string& blockdev) {
+bool fs_mgr_set_blk_ro(const std::string& blockdev, bool readonly) {
unique_fd fd(TEMP_FAILURE_RETRY(open(blockdev.c_str(), O_RDONLY | O_CLOEXEC)));
if (fd < 0) {
return false;
}
- int ON = 1;
+ int ON = readonly;
return ioctl(fd, BLKROSET, &ON) == 0;
}
diff --git a/fs_mgr/fs_mgr_overlayfs.cpp b/fs_mgr/fs_mgr_overlayfs.cpp
index 7dae7f1..6364ca9 100644
--- a/fs_mgr/fs_mgr_overlayfs.cpp
+++ b/fs_mgr/fs_mgr_overlayfs.cpp
@@ -277,6 +277,9 @@
// Don't check entries that are managed by vold.
if (entry->fs_mgr_flags.vold_managed || entry->fs_mgr_flags.recovery_only) return false;
+ // *_other doesn't want overlayfs.
+ if (entry->fs_mgr_flags.slot_select_other) return false;
+
// Only concerned with readonly partitions.
if (!(entry->flags & MS_RDONLY)) return false;
@@ -595,7 +598,11 @@
entry.mount_point = kScratchMountPoint;
entry.fs_type = mnt_type;
entry.flags = MS_RELATIME;
- if (readonly) entry.flags |= MS_RDONLY;
+ if (readonly) {
+ entry.flags |= MS_RDONLY;
+ } else {
+ fs_mgr_set_blk_ro(device_path, false);
+ }
auto save_errno = errno;
auto mounted = fs_mgr_do_mount_one(entry) == 0;
if (!mounted) {
@@ -653,6 +660,7 @@
return false;
}
command += " " + scratch_device;
+ fs_mgr_set_blk_ro(scratch_device, false);
auto ret = system(command.c_str());
if (ret) {
LERROR << "make " << mnt_type << " filesystem on " << scratch_device << " return=" << ret;
diff --git a/fs_mgr/fs_mgr_priv.h b/fs_mgr/fs_mgr_priv.h
index 7d1159b..7842ca2 100644
--- a/fs_mgr/fs_mgr_priv.h
+++ b/fs_mgr/fs_mgr_priv.h
@@ -134,7 +134,7 @@
const std::chrono::milliseconds relative_timeout,
FileWaitMode wait_mode = FileWaitMode::Exists);
-bool fs_mgr_set_blk_ro(const std::string& blockdev);
+bool fs_mgr_set_blk_ro(const std::string& blockdev, bool readonly = true);
bool fs_mgr_update_for_slotselect(Fstab* fstab);
bool fs_mgr_is_device_unlocked();
const std::string& get_android_dt_dir();
diff --git a/fs_mgr/liblp/utility.cpp b/fs_mgr/liblp/utility.cpp
index 9ccabe9..ecf94a4 100644
--- a/fs_mgr/liblp/utility.cpp
+++ b/fs_mgr/liblp/utility.cpp
@@ -19,6 +19,11 @@
#include <sys/stat.h>
#include <unistd.h>
+#if defined(__linux__)
+#include <linux/fs.h>
+#include <sys/ioctl.h>
+#endif
+
#include <android-base/file.h>
#include <ext4_utils/ext4_utils.h>
#include <openssl/sha.h>
@@ -155,5 +160,16 @@
return true;
}
+bool SetBlockReadonly(int fd, bool readonly) {
+#if defined(__linux__)
+ int val = readonly;
+ return ioctl(fd, BLKROSET, &val) == 0;
+#else
+ (void)fd;
+ (void)readonly;
+ return true;
+#endif
+}
+
} // namespace fs_mgr
} // namespace android
diff --git a/fs_mgr/liblp/utility.h b/fs_mgr/liblp/utility.h
index 8b70919..e8b2ca9 100644
--- a/fs_mgr/liblp/utility.h
+++ b/fs_mgr/liblp/utility.h
@@ -29,6 +29,7 @@
#define LWARN LOG(WARNING) << LP_TAG
#define LINFO LOG(INFO) << LP_TAG
#define LERROR LOG(ERROR) << LP_TAG
+#define PWARNING PLOG(WARNING) << LP_TAG
#define PERROR PLOG(ERROR) << LP_TAG
namespace android {
@@ -88,6 +89,9 @@
bool UpdateBlockDevicePartitionName(LpMetadataBlockDevice* device, const std::string& name);
bool UpdatePartitionGroupName(LpMetadataPartitionGroup* group, const std::string& name);
+// Call BLKROSET ioctl on fd so that fd is readonly / read-writable.
+bool SetBlockReadonly(int fd, bool readonly);
+
} // namespace fs_mgr
} // namespace android
diff --git a/fs_mgr/liblp/writer.cpp b/fs_mgr/liblp/writer.cpp
index 454258b..54a1883 100644
--- a/fs_mgr/liblp/writer.cpp
+++ b/fs_mgr/liblp/writer.cpp
@@ -259,6 +259,12 @@
return false;
}
+ // On retrofit devices, super_partition is system_other and might be set to readonly by
+ // fs_mgr_set_blk_ro(). Unset readonly so that fd can be written to.
+ if (!SetBlockReadonly(fd.get(), false)) {
+ PWARNING << __PRETTY_FUNCTION__ << " BLKROSET 0 failed: " << super_partition;
+ }
+
// Write zeroes to the first block.
std::string zeroes(LP_PARTITION_RESERVED_BYTES, 0);
if (SeekFile64(fd, 0, SEEK_SET) < 0) {
diff --git a/init/main.cpp b/init/main.cpp
index 868c409..2ce46ef 100644
--- a/init/main.cpp
+++ b/init/main.cpp
@@ -57,27 +57,22 @@
return ueventd_main(argc, argv);
}
- if (argc < 2) {
- return FirstStageMain(argc, argv);
+ if (argc > 1) {
+ if (!strcmp(argv[1], "subcontext")) {
+ android::base::InitLogging(argv, &android::base::KernelLogger);
+ const BuiltinFunctionMap function_map;
+
+ return SubcontextMain(argc, argv, &function_map);
+ }
+
+ if (!strcmp(argv[1], "selinux_setup")) {
+ return SetupSelinux(argv);
+ }
+
+ if (!strcmp(argv[1], "second_stage")) {
+ return SecondStageMain(argc, argv);
+ }
}
- if (!strcmp(argv[1], "subcontext")) {
- android::base::InitLogging(argv, &android::base::KernelLogger);
- const BuiltinFunctionMap function_map;
-
- return SubcontextMain(argc, argv, &function_map);
- }
-
- if (!strcmp(argv[1], "selinux_setup")) {
- return SetupSelinux(argv);
- }
-
- if (!strcmp(argv[1], "second_stage")) {
- return SecondStageMain(argc, argv);
- }
-
- android::base::InitLogging(argv, &android::base::KernelLogger);
-
- LOG(ERROR) << "Unknown argument passed to init '" << argv[1] << "'";
- return 1;
+ return FirstStageMain(argc, argv);
}
diff --git a/init/selinux.cpp b/init/selinux.cpp
index 04ca207..e4da52c 100644
--- a/init/selinux.cpp
+++ b/init/selinux.cpp
@@ -432,24 +432,6 @@
selinux_android_restorecon("/dev/urandom", 0);
selinux_android_restorecon("/dev/__properties__", 0);
- selinux_android_restorecon("/plat_file_contexts", 0);
- selinux_android_restorecon("/nonplat_file_contexts", 0);
- selinux_android_restorecon("/vendor_file_contexts", 0);
- selinux_android_restorecon("/plat_property_contexts", 0);
- selinux_android_restorecon("/nonplat_property_contexts", 0);
- selinux_android_restorecon("/vendor_property_contexts", 0);
- selinux_android_restorecon("/plat_seapp_contexts", 0);
- selinux_android_restorecon("/nonplat_seapp_contexts", 0);
- selinux_android_restorecon("/vendor_seapp_contexts", 0);
- selinux_android_restorecon("/plat_service_contexts", 0);
- selinux_android_restorecon("/nonplat_service_contexts", 0);
- selinux_android_restorecon("/vendor_service_contexts", 0);
- selinux_android_restorecon("/plat_hwservice_contexts", 0);
- selinux_android_restorecon("/nonplat_hwservice_contexts", 0);
- selinux_android_restorecon("/vendor_hwservice_contexts", 0);
- selinux_android_restorecon("/sepolicy", 0);
- selinux_android_restorecon("/vndservice_contexts", 0);
-
selinux_android_restorecon("/dev/block", SELINUX_ANDROID_RESTORECON_RECURSE);
selinux_android_restorecon("/dev/device-mapper", 0);
diff --git a/liblog/.clang-format b/liblog/.clang-format
deleted file mode 100644
index 9db87a8..0000000
--- a/liblog/.clang-format
+++ /dev/null
@@ -1,9 +0,0 @@
-BasedOnStyle: Google
-AllowShortFunctionsOnASingleLine: false
-
-CommentPragmas: NOLINT:.*
-DerivePointerAlignment: false
-PointerAlignment: Left
-PenaltyExcessCharacter: 32
-
-Cpp11BracedListStyle: false
diff --git a/liblog/.clang-format b/liblog/.clang-format
new file mode 120000
index 0000000..fd0645f
--- /dev/null
+++ b/liblog/.clang-format
@@ -0,0 +1 @@
+../.clang-format-2
\ No newline at end of file
diff --git a/liblog/README b/liblog/README
deleted file mode 100644
index 5a845be..0000000
--- a/liblog/README
+++ /dev/null
@@ -1,209 +0,0 @@
-LIBLOG(3) Android Internal NDK Programming Manual LIBLOG(3)
-
-
-
-NAME
- liblog - Android Internal NDK logger interfaces
-
-SYNOPSIS
- /*
- * Please limit to 24 characters for runtime is loggable,
- * 16 characters for persist is loggable, and logcat pretty
- * alignment with limit of 7 characters.
- */
- #define LOG_TAG "yourtag"
- #include <log/log.h>
-
- ALOG(android_priority, tag, format, ...)
- IF_ALOG(android_priority, tag)
- LOG_PRI(priority, tag, format, ...)
- LOG_PRI_VA(priority, tag, format, args)
- #define LOG_TAG NULL
- ALOGV(format, ...)
- SLOGV(format, ...)
- RLOGV(format, ...)
- ALOGV_IF(cond, format, ...)
- SLOGV_IF(cond, format, ...)
- RLOGV_IF(cond, format, ...)
- IF_ALOGC()
- ALOGD(format, ...)
- SLOGD(format, ...)
- RLOGD(format, ...)
- ALOGD_IF(cond, format, ...)
- SLOGD_IF(cond, format, ...)
- RLOGD_IF(cond, format, ...)
- IF_ALOGD()
- ALOGI(format, ...)
- SLOGI(format, ...)
- RLOGI(format, ...)
- ALOGI_IF(cond, format, ...)
- SLOGI_IF(cond, format, ...)
- RLOGI_IF(cond, format, ...)
- IF_ALOGI()
- ALOGW(format, ...)
- SLOGW(format, ...)
- RLOGW(format, ...)
- ALOGW_IF(cond, format, ...)
- SLOGW_IF(cond, format, ...)
- RLOGW_IF(cond, format, ...)
- IF_ALOGW()
- ALOGE(format, ...)
- SLOGE(format, ...)
- RLOGE(format, ...)
- ALOGE_IF(cond, format, ...)
- SLOGE_IF(cond, format, ...)
- RLOGE_IF(cond, format, ...)
- IF_ALOGE()
- LOG_FATAL(format, ...)
- LOG_ALWAYS_FATAL(format, ...)
- LOG_FATAL_IF(cond, format, ...)
- LOG_ALWAYS_FATAL_IF(cond, format, ...)
- ALOG_ASSERT(cond, format, ...)
- LOG_EVENT_INT(tag, value)
- LOG_EVENT_LONG(tag, value)
-
- clockid_t android_log_clockid()
-
- log_id_t android_logger_get_id(struct logger *logger)
- int android_logger_clear(struct logger *logger)
- int android_logger_get_log_size(struct logger *logger)
- int android_logger_get_log_readable_size(struct logger *logger)
- int android_logger_get_log_version(struct logger *logger)
-
- struct logger_list *android_logger_list_alloc(int mode,
- unsigned int tail,
- pid_t pid)
- struct logger *android_logger_open(struct logger_list *logger_list,
- log_id_t id)
- struct logger_list *android_logger_list_open(log_id_t id, int mode,
- unsigned int tail,
- pid_t pid)
- int android_logger_list_read(struct logger_list *logger_list,
- struct log_msg *log_msg)
- void android_logger_list_free(struct logger_list *logger_list)
-
- log_id_t android_name_to_log_id(const char *logName)
- const char *android_log_id_to_name(log_id_t log_id)
-
- android_log_context create_android_logger(uint32_t tag)
-
- int android_log_write_list_begin(android_log_context ctx)
- int android_log_write_list_end(android_log_context ctx)
-
- int android_log_write_int32(android_log_context ctx, int32_t value)
- int android_log_write_int64(android_log_context ctx, int64_t value)
- int android_log_write_string8(android_log_context ctx,
- const char *value)
- int android_log_write_string8_len(android_log_context ctx,
- const char *value, size_t maxlen)
- int android_log_write_float32(android_log_context ctx, float value)
-
- int android_log_write_list(android_log_context ctx,
- log_id_t id = LOG_ID_EVENTS)
-
- android_log_context create_android_log_parser(const char *msg,
- size_t len)
- android_log_list_element android_log_read_next(android_log_context ctx)
- android_log_list_element android_log_peek_next(android_log_context ctx)
-
- int android_log_destroy(android_log_context *ctx)
-
- #include <log/log_transport.h>
-
- int android_set_log_transport(int transport_flag)
- int android_get_log_transport()
-
- Link with -llog
-
-DESCRIPTION
- liblog represents an interface to the volatile Android Logging system
- for NDK (Native) applications and libraries. Interfaces for either
- writing or reading logs. The log buffers are divided up in Main, Sys‐
- tem, Radio and Events sub-logs.
-
- The logging interfaces are a series of macros, all of which can be
- overridden individually in order to control the verbosity of the appli‐
- cation or library. [ASR]LOG[VDIWE] calls are used to log to BAsic,
- System or Radio sub-logs in either the Verbose, Debug, Info, Warning or
- Error priorities. [ASR]LOG[VDIWE]_IF calls are used to perform thus
- based on a condition being true. IF_ALOG[VDIWE] calls are true if the
- current LOG_TAG is enabled at the specified priority. LOG_ALWAYS_FATAL
- is used to ALOG a message, then kill the process. LOG_FATAL call is a
- variant of LOG_ALWAYS_FATAL, only enabled in engineering, and not
- release builds. ALOG_ASSERT is used to ALOG a message if the condition
- is false; the condition is part of the logged message.
- LOG_EVENT_(INT|LONG) is used to drop binary content into the Events
- sub-log.
-
- The log reading interfaces permit opening the logs either singly or
- multiply, retrieving a log entry at a time in time sorted order,
- optionally limited to a specific pid and tail of the log(s) and finally
- a call closing the logs. A single log can be opened with android_log‐
- ger_list_open; or multiple logs can be opened with android_log‐
- ger_list_alloc, calling in turn the android_logger_open for each log
- id. Each entry can be retrieved with android_logger_list_read. The
- log(s) can be closed with android_logger_list_free. The logs should be
- opened with an ANDROID_LOG_RDONLY mode. ANDROID_LOG_NONBLOCK mode
- will report when the log reading is done with an EAGAIN error return
- code, otherwise the android_logger_list_read call will block for new
- entries.
-
- The ANDROID_LOG_WRAP mode flag to the android_logger_list_alloc_time
- signals logd to quiesce the reader until the buffer is about to prune
- at the start time then proceed to dumping content.
-
- The ANDROID_LOG_PSTORE mode flag to the android_logger_open is used to
- switch from the active logs to the persistent logs from before the last
- reboot.
-
- The value returned by android_logger_open can be used as a parameter to
- the android_logger_clear function to empty the sub-log. It is recom‐
- mended to only open log ANDROID_LOG_WRONLY in that case.
-
- The value returned by android_logger_open can be used as a parameter to
- the android_logger_get_log_(size|readable_size|version) to retrieve the
- sub-log maximum size, readable size and log buffer format protocol ver‐
- sion respectively. android_logger_get_id returns the id that was used
- when opening the sub-log. It is recommended to open the log
- ANDROID_LOG_RDONLY in these cases.
-
- android_set_log_transport() selects transport filters. Argument is
- either LOGGER_DEFAULT, LOGGER_LOGD, LOGGER_NULL or LOGGER_LOCAL. Log to
- logger daemon for default or logd, drop contents on floor, or log into
- local memory respectively. Both android_set_log_transport()
- and android_get_log_transport() return the current transport mask, or
- a negative errno for any problems.
-
-ERRORS
- If messages fail, a negative error code will be returned to the caller.
-
- The -ENOTCONN return code indicates that the logger daemon is stopped.
-
- The -EBADF return code indicates that the log access point can not be
- opened, or the log buffer id is out of range.
-
- For the -EAGAIN return code, this means that the logging message was
- temporarily backed-up either because of Denial Of Service (DOS) logging
- pressure from some chatty application or service in the Android system,
- or if too small of a value is set in /proc/sys/net/unix/max_dgram_qlen.
- To aid in diagnosing the occurence of this, a binary event from liblog
- will be sent to the log daemon once a new message can get through
- indicating how many messages were dropped as a result. Please take
- action to resolve the structural problems at the source.
-
- It is generally not advised for the caller to retry the -EAGAIN return
- code as this will only make the problem(s) worse and cause your
- application to temporarily drop to the logger daemon priority, BATCH
- scheduling policy and background task cgroup. If you require a group of
- messages to be passed atomically, merge them into one message with
- embedded newlines to the maximum length LOGGER_ENTRY_MAX_PAYLOAD.
-
- Other return codes from writing operation can be returned. Since the
- library retries on EINTR, -EINTR should never be returned.
-
-SEE ALSO
- syslogd(8), klogd, auditd(8)
-
-
-
- 08 Feb 2017 LIBLOG(3)
diff --git a/liblog/README.md b/liblog/README.md
new file mode 100644
index 0000000..886fe25
--- /dev/null
+++ b/liblog/README.md
@@ -0,0 +1,177 @@
+Android liblog
+--------------
+
+Public Functions and Macros
+---------------------------
+
+ /*
+ * Please limit to 24 characters for runtime is loggable,
+ * 16 characters for persist is loggable, and logcat pretty
+ * alignment with limit of 7 characters.
+ */
+ #define LOG_TAG "yourtag"
+ #include <log/log.h>
+
+ ALOG(android_priority, tag, format, ...)
+ IF_ALOG(android_priority, tag)
+ LOG_PRI(priority, tag, format, ...)
+ LOG_PRI_VA(priority, tag, format, args)
+ #define LOG_TAG NULL
+ ALOGV(format, ...)
+ SLOGV(format, ...)
+ RLOGV(format, ...)
+ ALOGV_IF(cond, format, ...)
+ SLOGV_IF(cond, format, ...)
+ RLOGV_IF(cond, format, ...)
+ IF_ALOGC()
+ ALOGD(format, ...)
+ SLOGD(format, ...)
+ RLOGD(format, ...)
+ ALOGD_IF(cond, format, ...)
+ SLOGD_IF(cond, format, ...)
+ RLOGD_IF(cond, format, ...)
+ IF_ALOGD()
+ ALOGI(format, ...)
+ SLOGI(format, ...)
+ RLOGI(format, ...)
+ ALOGI_IF(cond, format, ...)
+ SLOGI_IF(cond, format, ...)
+ RLOGI_IF(cond, format, ...)
+ IF_ALOGI()
+ ALOGW(format, ...)
+ SLOGW(format, ...)
+ RLOGW(format, ...)
+ ALOGW_IF(cond, format, ...)
+ SLOGW_IF(cond, format, ...)
+ RLOGW_IF(cond, format, ...)
+ IF_ALOGW()
+ ALOGE(format, ...)
+ SLOGE(format, ...)
+ RLOGE(format, ...)
+ ALOGE_IF(cond, format, ...)
+ SLOGE_IF(cond, format, ...)
+ RLOGE_IF(cond, format, ...)
+ IF_ALOGE()
+ LOG_FATAL(format, ...)
+ LOG_ALWAYS_FATAL(format, ...)
+ LOG_FATAL_IF(cond, format, ...)
+ LOG_ALWAYS_FATAL_IF(cond, format, ...)
+ ALOG_ASSERT(cond, format, ...)
+ LOG_EVENT_INT(tag, value)
+ LOG_EVENT_LONG(tag, value)
+
+ clockid_t android_log_clockid()
+
+ log_id_t android_logger_get_id(struct logger *logger)
+ int android_logger_clear(struct logger *logger)
+ int android_logger_get_log_size(struct logger *logger)
+ int android_logger_get_log_readable_size(struct logger *logger)
+ int android_logger_get_log_version(struct logger *logger)
+
+ struct logger_list *android_logger_list_alloc(int mode, unsigned int tail, pid_t pid)
+ struct logger *android_logger_open(struct logger_list *logger_list, log_id_t id)
+ struct logger_list *android_logger_list_open(log_id_t id, int mode, unsigned int tail, pid_t pid)
+ int android_logger_list_read(struct logger_list *logger_list, struct log_msg *log_msg)
+ void android_logger_list_free(struct logger_list *logger_list)
+
+ log_id_t android_name_to_log_id(const char *logName)
+ const char *android_log_id_to_name(log_id_t log_id)
+
+ android_log_context create_android_logger(uint32_t tag)
+
+ int android_log_write_list_begin(android_log_context ctx)
+ int android_log_write_list_end(android_log_context ctx)
+
+ int android_log_write_int32(android_log_context ctx, int32_t value)
+ int android_log_write_int64(android_log_context ctx, int64_t value)
+ int android_log_write_string8(android_log_context ctx, const char *value)
+ int android_log_write_string8_len(android_log_context ctx, const char *value, size_t maxlen)
+ int android_log_write_float32(android_log_context ctx, float value)
+
+ int android_log_write_list(android_log_context ctx, log_id_t id = LOG_ID_EVENTS)
+
+ android_log_context create_android_log_parser(const char *msg, size_t len)
+ android_log_list_element android_log_read_next(android_log_context ctx)
+ android_log_list_element android_log_peek_next(android_log_context ctx)
+
+ int android_log_destroy(android_log_context *ctx)
+
+ #include <log/log_transport.h>
+
+ int android_set_log_transport(int transport_flag)
+ int android_get_log_transport()
+
+Description
+-----------
+
+liblog represents an interface to the volatile Android Logging system for NDK (Native) applications
+and libraries. Interfaces for either writing or reading logs. The log buffers are divided up in
+Main, System, Radio and Events sub-logs.
+
+The logging interfaces are a series of macros, all of which can be overridden individually in order
+to control the verbosity of the application or library. `[ASR]LOG[VDIWE]` calls are used to log to
+BAsic, System or Radio sub-logs in either the Verbose, Debug, Info, Warning or Error priorities.
+`[ASR]LOG[VDIWE]_IF` calls are used to perform thus based on a condition being true.
+`IF_ALOG[VDIWE]` calls are true if the current `LOG_TAG` is enabled at the specified priority.
+`LOG_ALWAYS_FATAL` is used to `ALOG` a message, then kill the process. `LOG_FATAL` call is a
+variant of `LOG_ALWAYS_FATAL`, only enabled in engineering, and not release builds. `ALOG_ASSERT`
+is used to `ALOG` a message if the condition is false; the condition is part of the logged message.
+`LOG_EVENT_(INT|LONG)` is used to drop binary content into the Events sub-log.
+
+The log reading interfaces permit opening the logs either singly or multiply, retrieving a log entry
+at a time in time sorted order, optionally limited to a specific pid and tail of the log(s) and
+finally a call closing the logs. A single log can be opened with `android_logger_list_open()`; or
+multiple logs can be opened with `android_logger_list_alloc()`, calling in turn the
+`android_logger_open()` for each log id. Each entry can be retrieved with
+`android_logger_list_read()`. The log(s) can be closed with `android_logger_list_free()`. The logs
+should be opened with an `ANDROID_LOG_RDONLY` mode. `ANDROID_LOG_NONBLOCK` mode will report when
+the log reading is done with an `EAGAIN` error return code, otherwise the
+`android_logger_list_read()` call will block for new entries.
+
+The `ANDROID_LOG_WRAP` mode flag to the `android_logger_list_alloc_time()` signals logd to quiesce
+the reader until the buffer is about to prune at the start time then proceed to dumping content.
+
+The `ANDROID_LOG_PSTORE` mode flag to the `android_logger_open()` is used to switch from the active
+logs to the persistent logs from before the last reboot.
+
+The value returned by `android_logger_open()` can be used as a parameter to the
+`android_logger_clear()` function to empty the sub-log. It is recommended to only open log
+`ANDROID_LOG_WRONLY` in that case.
+
+The value returned by `android_logger_open()` can be used as a parameter to the
+`android_logger_get_log_(size|readable_size|version)` to retrieve the sub-log maximum size, readable
+size and log buffer format protocol version respectively. `android_logger_get_id()` returns the id
+that was used when opening the sub-log. It is recommended to open the log `ANDROID_LOG_RDONLY` in
+these cases.
+
+`android_set_log_transport()` selects transport filters. Argument is either `LOGGER_DEFAULT`,
+`LOGGER_LOGD`, `LOGGER_NULL` or `LOGGER_LOCAL`. Log to logger daemon for default or logd, drop
+contents on floor, or log into local memory respectively. `Both android_set_log_transport()` and
+`android_get_log_transport()` return the current transport mask, or a negative errno for any
+problems.
+
+Errors
+------
+
+If messages fail, a negative error code will be returned to the caller.
+
+The `-ENOTCONN` return code indicates that the logger daemon is stopped.
+
+The `-EBADF` return code indicates that the log access point can not be opened, or the log buffer id
+is out of range.
+
+For the `-EAGAIN` return code, this means that the logging message was temporarily backed-up either
+because of Denial Of Service (DOS) logging pressure from some chatty application or service in the
+Android system, or if too small of a value is set in /proc/sys/net/unix/max_dgram_qlen. To aid in
+diagnosing the occurence of this, a binary event from liblog will be sent to the log daemon once a
+new message can get through indicating how many messages were dropped as a result. Please take
+action to resolve the structural problems at the source.
+
+It is generally not advised for the caller to retry the `-EAGAIN` return code as this will only make
+the problem(s) worse and cause your application to temporarily drop to the logger daemon priority,
+BATCH scheduling policy and background task cgroup. If you require a group of messages to be passed
+atomically, merge them into one message with embedded newlines to the maximum length
+`LOGGER_ENTRY_MAX_PAYLOAD`.
+
+Other return codes from writing operation can be returned. Since the library retries on `EINTR`,
+`-EINTR` should never be returned.