Android Studio for Platform (ASfP) is the version of the Android Studio IDE for Android Open Source Project (AOSP) platform developers who build with the Soong build system. ASfP includes the following features:
language
Multi-language Support
Edit C++, Kotlin, and Java programming languages in the same IDE.
settings
Project Setup Wizard
Configure your lunch target and platform modules.
Get started with ASfP
If you haven't already installed repo, follow the instructions at Installing Repo.
If you haven't already initialized and synced your Repo checkout, follow the instructions at Initializing a Repo client.
Download ASfP.
Install ASfP: sudo dpkg -i /path/to/asfp-2023.1.1.19-linux.deb.
Open ASfP from the command line: /opt/android-studio-for-platform/bin/studio.sh.
Import your project by pointing to your repo checkout directory, specifying a lunch target, and selecting which modules you want to build.
Click Finish and your project will begin syncing.
Request to join our external group for user support.
service servicemanager /system/bin/servicemanager classcore animation user system group system readproc critical onrestart restart apexd onrestart restart audioserver onrestart restart gatekeeperd onrestart class_restart main onrestart class_restart hal onrestart class_restart early_hal writepid /dev/cpuset/system-background/tasks shutdown critical
on early-init
...
mkdir /acct/uid
# 挂载linkerconfig（动态链接器）
mount none /linkerconfig/bootstrap /linkerconfig bind rec
# 启动ueventd(位于/system/bin/ueventd),ueventd是init启动的第一个进程
start ueventd
# memory.pressure_level used by lmkd
chown root system /dev/memcg/memory.pressure_level
chmod 0040 /dev/memcg/memory.pressure_level
# app mem cgroups, used by activity manager, lmkd and zygote
mkdir /dev/memcg/apps/ 0755 system system
mkdir /dev/memcg/system 0550 system system
mkdir /dev/net 0755 root root
symlink ../tun /dev/net/tun
...
# 挂载tracefs，可以通过指定方式到处trace日志，分析CPU和内存相关等问题
mount tracefs tracefs /sys/kernel/tracing gid=3012
# create sys dirctory
# 创建/sys目录并指定权限
mkdir /dev/sys 0755 system system
mkdir /dev/sys/fs 0755 system system
mkdir /dev/sys/block 0755 system system
int main(int argc, char* const argv[])
{
...
if (zygote) {
runtime.start("com.android.internal.os.ZygoteInit", args, zygote);
} else if (className) {
runtime.start("com.android.internal.os.RuntimeInit", args, zygote);
} else {
fprintf(stderr, "Error: no class name or --zygote supplied.\n");
app_usage();
LOG_ALWAYS_FATAL("app_process: no class name or --zygote supplied.");
}
}
if (auto result = WriteFile("/sys/fs/selinux/checkreqprot", "0"); !result.ok()) { LOG(FATAL) << "Unable to write to /sys/fs/selinux/checkreqprot: " << result.error(); } }
The Android Init Language consists of five broad classes of statements: Actions, Commands, Services, Options, and Imports.
All of these are line-oriented, consisting of tokens separated by whitespace. The c-style backslash escapes may be used to insert whitespace into a token. Double quotes may also be used to prevent whitespace from breaking text into multiple tokens. The backslash, when it is the last character on a line, may be used for line-folding.
Lines which start with a `#` (leading whitespace allowed) are comments.
System properties can be expanded using the syntax `${property.name}`. This also works in contexts where concatenation is required, such as `import /init.recovery.${ro.hardware}.rc`.
Actions and Services implicitly declare a new section. All commands or options belong to the section most recently declared. Commands or options before the first section are ignored.
Services have unique names. If a second Service is defined with the same name as an existing one, it is ignored and an error message is logged.
Init .rc Files -------------- The init language is used in plain text files that take the .rc file extension. There are typically multiple of these in multiple locations on the system, described below.
`/system/etc/init/hw/init.rc` is the primary .rc file and is loaded by the init executable at the beginning of its execution. It is responsible for the initial set up of the system.
Init loads all of the files contained within the `/{system,system_ext,vendor,odm,product}/etc/init/` directories immediately after loading the primary `/system/etc/init/hw/init.rc`. This is explained in more details in the [Imports](#imports) section of this file.
Legacy devices without the first stage mount mechanism previously were able to import init scripts during mount_all, however that is deprecated and not allowed for devices launching after Q.
The intention of these directories is:
1. /system/etc/init/ is for core system items such as SurfaceFlinger, MediaService, and logd. 2. /vendor/etc/init/ is for SoC vendor items such as actions or daemons needed for core SoC functionality. 3. /odm/etc/init/ is for device manufacturer items such as actions or daemons needed for motion sensor or other peripheral functionality.
All services whose binaries reside on the system, vendor, or odm partitions should have their service entries placed into a corresponding init .rc file, located in the /etc/init/ directory of the partition where they reside. There is a build system macro, LOCAL\_INIT\_RC, that handles this for developers. Each init .rc file should additionally contain any actions associated with its service.
An example is the userdebug logcatd.rc and Android.mk files located in the system/core/logcat directory. The LOCAL\_INIT\_RC macro in the Android.mk file places logcatd.rc in /system/etc/init/ during the build process. Init loads logcatd.rc during the mount\_all command and allows the service to be run and the action to be queued when appropriate.
This break up of init .rc files according to their daemon is preferred to the previously used monolithic init .rc files. This approach ensures that the only service entries that init reads and the only actions that init performs correspond to services whose binaries are in fact present on the file system, which was not the case with the monolithic init .rc files. This additionally will aid in merge conflict resolution when multiple services are added to the system, as each one will go into a separate file.
Versioned RC files within APEXs -------------------------------
With the arrival of mainline on Android Q, the individual mainline modules carry their own init.rc files within their boundaries. Init processes these files according to the naming pattern `/apex/*/etc/*rc`.
Because APEX modules must run on more than one release of Android, they may require different parameters as part of the services they define. This is achieved, starting in Android T, by incorporating the SDK version information in the name of the init file. The suffix is changed from `.rc` to `.#rc` where # is the first SDK where that RC file is accepted. An init file specific to SDK=31 might be named `init.31rc`. With this scheme, an APEX may include multiple init files. An example is appropriate.
For an APEX module with the following files in /apex/sample-module/apex/etc/:
1. init.rc 2. init.32rc 4. init.35rc
The selection rule chooses the highest `.#rc` value that does not exceed the SDK of the currently running system. The unadorned `.rc` is interpreted as sdk=0.
When this APEX is installed on a device with SDK <=31, the system will process init.rc. When installed on a device running SDK 32, 33, or 34, it will use init.32rc. When installed on a device running SDKs >= 35, it will choose init.35rc
This versioning scheme is used only for the init files within APEX modules; it does not apply to the init files stored in /system/etc/init, /vendor/etc/init, or other directories.
This naming scheme is available after Android S.
Actions ------- Actions are named sequences of commands. Actions have a trigger which is used to determine when the action is executed. When an event occurs which matches an action's trigger, that action is added to the tail of a to-be-executed queue (unless it is already on the queue).
Each action in the queue is dequeued in sequence and each command in that action is executed in sequence. Init handles other activities (device creation/destruction, property setting, process restarting) "between" the execution of the commands in activities.
Actions take the form of:
on <trigger> [&& <trigger>]* <command> <command> <command>
Actions are added to the queue and executed based on the order that the file that contains them was parsed (see the Imports section), then sequentially within an individual file.
For example if a file contains:
on boot setprop a 1 setprop b 2
on boot && property:true=true setprop c 1 setprop d 2
on boot setprop e 1 setprop f 2
Then when the `boot` trigger occurs and assuming the property `true` equals `true`, then the order of the commands executed will be:
setprop a 1 setprop b 2 setprop c 1 setprop d 2 setprop e 1 setprop f 2
Services -------- Services are programs which init launches and (optionally) restarts when they exit. Services take the form of:
service <name> <pathname> [ <argument> ]* <option> <option> ...
Options ------- Options are modifiers to services. They affect how and when init runs the service.
`capabilities [ <capability>\* ]` > Set capabilities when exec'ing this service. 'capability' should be a Linux capability without the "CAP\_" prefix, like "NET\_ADMIN" or "SETPCAP". See http://man7.org/linux/man-pages/man7/capabilities.7.html for a list of Linux capabilities. If no capabilities are provided, then all capabilities are removed from this service, even if it runs as root.
`class <name> [ <name>\* ]` > Specify class names for the service. All services in a named class may be started or stopped together. A service is in the class "default" if one is not specified via the class option. Additional classnames beyond the (required) first one are used to group services. The `animation` class should include all services necessary for both boot animation and shutdown animation. As these services can be launched very early during bootup and can run until the last stage of shutdown, access to /data partition is not guaranteed. These services can check files under /data but it should not keep files opened and should work when /data is not available.
`console [<console>]` > This service needs a console. The optional second parameter chooses a specific console instead of the default. The default "/dev/console" can be changed by setting the "androidboot.console" kernel parameter. In all cases the leading "/dev/" should be omitted, so "/dev/tty0" would be specified as just "console tty0". This option connects stdin, stdout, and stderr to the console. It is mutually exclusive with the stdio_to_kmsg option, which only connects stdout and stderr to kmsg.
`critical [window=<fatal crash window mins>] [target=<fatal reboot target>]` > This is a device-critical service. If it exits more than four times in _fatal crash window mins_ minutes or before boot completes, the device will reboot into _fatal reboot target_. The default value of _fatal crash window mins_ is 4, and default value of _fatal reboot target_ is 'bootloader'. For tests, the fatal reboot can be skipped by setting property `init.svc_debug.no_fatal.<service-name>` to `true` for specified critical service.
`disabled` > This service will not automatically start with its class. It must be explicitly started by name or by interface name.
`enter_namespace <type> <path>` > Enters the namespace of type _type_ located at _path_. Only network namespaces are supported with _type_ set to "net". Note that only one namespace of a given _type_ may be entered.
`file <path> <type>` > Open a file path and pass its fd to the launched process. _type_ must be "r", "w" or "rw". For native executables see libcutils android\_get\_control\_file().
`group <groupname> [ <groupname>\* ]` > Change to 'groupname' before exec'ing this service. Additional groupnames beyond the (required) first one are used to set the supplemental groups of the process (via setgroups()). Currently defaults to root. (??? probably should default to nobody)
`interface <interface name> <instance name>` > Associates this service with a list of the AIDL or HIDL services that it provides. The interface name must be a fully-qualified name and not a value name. For instance, this is used to allow servicemanager or hwservicemanager to lazily start services. When multiple interfaces are served, this tag should be used multiple times. An example of an entry for a HIDL interface is `interface vendor.foo.bar@1.0::IBaz default`. For an AIDL interface, use `interface aidl <instance name>`. The instance name for an AIDL interface is whatever is registered with servicemanager, and these can be listed with `adb shell dumpsys -l`.
`ioprio <class> <priority>` > Sets the IO priority and IO priority class for this service via the SYS_ioprio_set syscall. _class_ must be one of "rt", "be", or "idle". _priority_ must be an integer in the range 0 - 7.
`keycodes <keycode> [ <keycode>\* ]` > Sets the keycodes that will trigger this service. If all of the keys corresponding to the passed keycodes are pressed at once, the service will start. This is typically used to start the bugreport service.
> This option may take a property instead of a list of keycodes. In this case, only one option is provided: the property name in the typical property expansion format. The property must contain a comma separated list of keycode values or the text 'none' to indicate that this service does not respond to keycodes.
> For example, `keycodes ${some.property.name:-none}` where some.property.name expands to "123,124,125". Since keycodes are handled very early in init, only PRODUCT_DEFAULT_PROPERTY_OVERRIDES properties can be used.
`memcg.limit_in_bytes <value>` and `memcg.limit_percent <value>` > Sets the child's memory.limit_in_bytes to the minimum of `limit_in_bytes` bytes and `limit_percent` which is interpreted as a percentage of the size of the device's physical memory (only if memcg is mounted). Values must be equal or greater than 0.
`memcg.limit_property <value>` > Sets the child's memory.limit_in_bytes to the value of the specified property (only if memcg is mounted). This property will override the values specified via `memcg.limit_in_bytes` and `memcg.limit_percent`.
`memcg.soft_limit_in_bytes <value>` > Sets the child's memory.soft_limit_in_bytes to the specified value (only if memcg is mounted), which must be equal or greater than 0.
`memcg.swappiness <value>` > Sets the child's memory.swappiness to the specified value (only if memcg is mounted), which must be equal or greater than 0.
`namespace <pid|mnt>` > Enter a new PID or mount namespace when forking the service.
`oneshot` > Do not restart the service when it exits.
`onrestart` > Execute a Command (see below) when service restarts.
`oom_score_adjust <value>` > Sets the child's /proc/self/oom\_score\_adj to the specified value, which must range from -1000 to 1000.
`override` > Indicates that this service definition is meant to override a previous definition for a service with the same name. This is typically meant for services on /odm to override those defined on /vendor. The last service definition that init parses with this keyword is the service definition will use for this service. Pay close attention to the order in which init.rc files are parsed, since it has some peculiarities for backwards compatibility reasons. The 'imports' section of this file has more details on the order.
`priority <priority>` > Scheduling priority of the service process. This value has to be in range -20 to 19. Default priority is 0. Priority is set via setpriority().
`reboot_on_failure <target>` > If this process cannot be started or if the process terminates with an exit code other than CLD_EXITED or an status other than '0', reboot the system with the target specified in _target_. _target_ takes the same format as the parameter to sys.powerctl. This is particularly intended to be used with the `exec_start` builtin for any must-have checks during boot.
`restart_period <seconds>` > If a non-oneshot service exits, it will be restarted at its start time plus this period. It defaults to 5s to rate limit crashing services. This can be increased for services that are meant to run periodically. For example, it may be set to 3600 to indicate that the service should run every hour or 86400 to indicate that the service should run every day.
`rlimit <resource> <cur> <max>` > This applies the given rlimit to the service. rlimits are inherited by child processes, so this effectively applies the given rlimit to the process tree started by this service. It is parsed similarly to the setrlimit command specified below.
`seclabel <seclabel>` > Change to 'seclabel' before exec'ing this service. Primarily for use by services run from the rootfs, e.g. ueventd, adbd. Services on the system partition can instead use policy-defined transitions based on their file security context. If not specified and no transition is defined in policy, defaults to the init context.
`setenv <name> <value>` > Set the environment variable _name_ to _value_ in the launched process.
`shutdown <shutdown_behavior>` > Set shutdown behavior of the service process. When this is not specified, the service is killed during shutdown process by using SIGTERM and SIGKILL. The service with shutdown_behavior of "critical" is not killed during shutdown until shutdown times out. When shutdown times out, even services tagged with "shutdown critical" will be killed. When the service tagged with "shutdown critical" is not running when shut down starts, it will be started.
`sigstop` > Send SIGSTOP to the service immediately before exec is called. This is intended for debugging. See the below section on debugging for how this can be used.
`socket <name> <type> <perm> [ <user> [ <group> [ <seclabel> ] ] ]` > Create a UNIX domain socket named /dev/socket/_name_ and pass its fd to the launched process. _type_ must be "dgram", "stream" or "seqpacket". _type_ may end with "+passcred" to enable SO_PASSCRED on the socket. User and group default to 0. 'seclabel' is the SELinux security context for the socket. It defaults to the service security context, as specified by seclabel or computed based on the service executable file security context. For native executables see libcutils android\_get\_control\_socket().
`stdio_to_kmsg` > Redirect stdout and stderr to /dev/kmsg_debug. This is useful for services that do not use native Android logging during early boot and whose logs messages we want to capture. This is only enabled when /dev/kmsg_debug is enabled, which is only enabled on userdebug and eng builds. This is mutually exclusive with the console option, which additionally connects stdin to the given console.
`task_profiles <profile> [ <profile>\* ]` > Set task profiles for the process when it forks. This is designed to replace the use of writepid option for moving a process into a cgroup.
`timeout_period <seconds>` > Provide a timeout after which point the service will be killed. The oneshot keyword is respected here, so oneshot services do not automatically restart, however all other services will. This is particularly useful for creating a periodic service combined with the restart_period option described above.
`updatable` > Mark that the service can be overridden (via the 'override' option) later in the boot sequence by APEXes. When a service with updatable option is started before APEXes are all activated, the execution is delayed until the activation is finished. A service that is not marked as updatable cannot be overridden by APEXes.
`user <username>` > Change to 'username' before exec'ing this service. Currently defaults to root. (??? probably should default to nobody) As of Android M, processes should use this option even if they require Linux capabilities. Previously, to acquire Linux capabilities, a process would need to run as root, request the capabilities, then drop to its desired uid. There is a new mechanism through fs\_config that allows device manufacturers to add Linux capabilities to specific binaries on a file system that should be used instead. This mechanism is described on <http://source.android.com/devices/tech/config/filesystem.html>. When using this new mechanism, processes can use the user option to select their desired uid without ever running as root. As of Android O, processes can also request capabilities directly in their .rc files. See the "capabilities" option below.
`writepid <file> [ <file>\* ]` > Write the child's pid to the given files when it forks. Meant for cgroup/cpuset usage. If no files under /dev/cpuset/ are specified, but the system property 'ro.cpuset.default' is set to a non-empty cpuset name (e.g. '/foreground'), then the pid is written to file /dev/cpuset/_cpuset\_name_/tasks. The use of this option for moving a process into a cgroup is obsolete. Please use task_profiles option instead.
Triggers -------- Triggers are strings which can be used to match certain kinds of events and used to cause an action to occur.
Triggers are subdivided into event triggers and property triggers.
Event triggers are strings triggered by the 'trigger' command or by the QueueEventTrigger() function within the init executable. These take the form of a simple string such as 'boot' or 'late-init'.
Property triggers are strings triggered when a named property changes value to a given new value or when a named property changes value to any new value. These take the form of 'property:<name>=<value>' and 'property:<name>=\*' respectively. Property triggers are additionally evaluated and triggered accordingly during the initial boot phase of init.
An Action can have multiple property triggers but may only have one event trigger.
For example: `on boot && property:a=b` defines an action that is only executed when the 'boot' event trigger happens and the property a equals b.
`on property:a=b && property:c=d` defines an action that is executed at three times:
1. During initial boot if property a=b and property c=d. 2. Any time that property a transitions to value b, while property c already equals d. 3. Any time that property c transitions to value d, while property a already equals b.
Trigger Sequence ----------------
Init uses the following sequence of triggers during early boot. These are the built-in triggers defined in init.cpp.
1. `early-init` - The first in the sequence, triggered after cgroups has been configured but before ueventd's coldboot is complete. 2. `init` - Triggered after coldboot is complete. 3. `charger` - Triggered if `ro.bootmode == "charger"`. 4. `late-init` - Triggered if `ro.bootmode != "charger"`, or via healthd triggering a boot from charging mode.
Remaining triggers are configured in `init.rc` and are not built-in. The default sequence for these is specified under the "on late-init" event in `init.rc`. Actions internal to `init.rc` have been omitted.
1. `early-fs` - Start vold. 2. `fs` - Vold is up. Mount partitions not marked as first-stage or latemounted. 3. `post-fs` - Configure anything dependent on early mounts. 4. `late-fs` - Mount partitions marked as latemounted. 5. `post-fs-data` - Mount and configure `/data`; set up encryption. `/metadata` is reformatted here if it couldn't mount in first-stage init. 6. `zygote-start` - Start the zygote. 7. `early-boot` - After zygote has started. 8. `boot` - After `early-boot` actions have completed.
Commands --------
`bootchart [start|stop]` > Start/stop bootcharting. These are present in the default init.rc files, but bootcharting is only active if the file /data/bootchart/enabled exists; otherwise bootchart start/stop are no-ops.
`chown <owner> <group> <path>` > Change file owner and group.
`class_start <serviceclass>` > Start all services of the specified class if they are not already running. See the start entry for more information on starting services.
`class_stop <serviceclass>` > Stop and disable all services of the specified class if they are currently running.
`class_reset <serviceclass>` > Stop all services of the specified class if they are currently running, without disabling them. They can be restarted later using `class_start`.
`class_restart [--only-enabled] <serviceclass>` > Restarts all services of the specified class. If `--only-enabled` is specified, then disabled services are skipped.
`copy <src> <dst>` > Copies a file. Similar to write, but useful for binary/large amounts of data. Regarding to the src file, copying from symbolic link file and world-writable or group-writable files are not allowed. Regarding to the dst file, the default mode created is 0600 if it does not exist. And it will be truncated if dst file is a normal regular file and already exists.
`copy_per_line <src> <dst>` > Copies a file line by line. Similar to copy, but useful for dst is a sysfs node that doesn't handle multiple lines of data.
`domainname <name>` > Set the domain name.
`enable <servicename>` > Turns a disabled service into an enabled one as if the service did not specify disabled. If the service is supposed to be running, it will be started now. Typically used when the bootloader sets a variable that indicates a specific service should be started when needed. E.g.
on property:ro.boot.myfancyhardware=1 enable my_fancy_service_for_my_fancy_hardware
`exec [ <seclabel> [ <user> [ <group>\* ] ] ] -- <command> [ <argument>\* ]` > Fork and execute command with the given arguments. The command starts after "--" so that an optional security context, user, and supplementary groups can be provided. No other commands will be run until this one finishes. _seclabel_ can be a - to denote default. Properties are expanded within _argument_. Init halts executing commands until the forked process exits.
`exec_background [ <seclabel> [ <user> [ <group>\* ] ] ] -- <command> [ <argument>\* ]` > Fork and execute command with the given arguments. This is handled similarly to the `exec` command. The difference is that init does not halt executing commands until the process exits for `exec_background`.
`exec_start <service>` > Start a given service and halt the processing of additional init commands until it returns. The command functions similarly to the `exec` command, but uses an existing service definition in place of the exec argument vector.
`export <name> <value>` > Set the environment variable _name_ equal to _value_ in the global environment (which will be inherited by all processes started after this command is executed)
`hostname <name>` > Set the host name.
`ifup <interface>` > Bring the network interface _interface_ online.
`insmod [-f] <path> [<options>]` > Install the module at _path_ with the specified options. -f: force installation of the module even if the version of the running kernel and the version of the kernel for which the module was compiled do not match.
`interface_start <name>` \ `interface_restart <name>` \ `interface_stop <name>` > Find the service that provides the interface _name_ if it exists and run the `start`, `restart`, or `stop` commands on it respectively. _name_ may be either a fully qualified HIDL name, in which case it is specified as `<interface>/<instance>`, or an AIDL name, in which case it is specified as `aidl/<interface>` for example `android.hardware.secure_element@1.1::ISecureElement/eSE1` or `aidl/aidl_lazy_test_1`.
> Note that these commands only act on interfaces specified by the `interface` service option, not on interfaces registered at runtime.
> Example usage of these commands: \ `interface_start android.hardware.secure_element@1.1::ISecureElement/eSE1` will start the HIDL Service that provides the `android.hardware.secure_element@1.1` and `eSI1` instance. \ `interface_start aidl/aidl_lazy_test_1` will start the AIDL service that provides the `aidl_lazy_test_1` interface.
`load_exports <path>` > Open the file at _path_ and export global environment variables declared there. Each line must be in the format `export <name> <value>`, as described above.
`load_system_props` > (This action is deprecated and no-op.)
`load_persist_props` > Loads persistent properties when /data has been decrypted. This is included in the default init.rc.
`loglevel <level>` > Sets init's log level to the integer level, from 7 (all logging) to 0 (fatal logging only). The numeric values correspond to the kernel log levels, but this command does not affect the kernel log level. Use the `write` command to write to `/proc/sys/kernel/printk` to change that. Properties are expanded within _level_.
`mark_post_data` > Used to mark the point right after /data is mounted.
`mkdir <path> [<mode>] [<owner>] [<group>] [encryption=<action>] [key=<key>]` > Create a directory at _path_, optionally with the given mode, owner, and group. If not provided, the directory is created with permissions 755 and owned by the root user and root group. If provided, the mode, owner and group will be updated if the directory exists already.
> _action_ can be one of: * `None`: take no encryption action; directory will be encrypted if parent is. * `Require`: encrypt directory, abort boot process if encryption fails * `Attempt`: try to set an encryption policy, but continue if it fails * `DeleteIfNecessary`: recursively delete directory if necessary to set encryption policy.
> _key_ can be one of: * `ref`: use the systemwide DE key * `per_boot_ref`: use the key freshly generated on each boot.
`mount_all [ <fstab> ] [--<option>]` > Calls fs\_mgr\_mount\_all on the given fs\_mgr-format fstab with optional options "early" and "late". With "--early" set, the init executable will skip mounting entries with "latemount" flag and triggering fs encryption state event. With "--late" set, init executable will only mount entries with "latemount" flag. By default, no option is set, and mount\_all will process all entries in the given fstab. If the fstab parameter is not specified, fstab.${ro.boot.fstab_suffix}, fstab.${ro.hardware} or fstab.${ro.hardware.platform} will be scanned for under /odm/etc, /vendor/etc, or / at runtime, in that order.
`mount <type> <device> <dir> [ <flag>\* ] [<options>]` > Attempt to mount the named device at the directory _dir_ _flag_s include "ro", "rw", "remount", "noatime", ... _options_ include "barrier=1", "noauto\_da\_alloc", "discard", ... as a comma separated string, e.g. barrier=1,noauto\_da\_alloc
`perform_apex_config` > Performs tasks after APEXes are mounted. For example, creates data directories for the mounted APEXes, parses config file(s) from them, and updates linker configurations. Intended to be used only once when apexd notifies the mount event by setting `apexd.status` to ready.
`restart [--only-if-running] <service>` > Stops and restarts a running service, does nothing if the service is currently restarting, otherwise, it just starts the service. If "--only-if-running" is specified, the service is only restarted if it is already running.
`restorecon <path> [ <path>\* ]` > Restore the file named by _path_ to the security context specified in the file\_contexts configuration. Not required for directories created by the init.rc as these are automatically labeled correctly by init.
`restorecon_recursive <path> [ <path>\* ]` > Recursively restore the directory tree named by _path_ to the security contexts specified in the file\_contexts configuration.
`rm <path>` > Calls unlink(2) on the given path. You might want to use "exec -- rm ..." instead (provided the system partition is already mounted).
`rmdir <path>` > Calls rmdir(2) on the given path.
`readahead <file|dir> [--fully]` > Calls readahead(2) on the file or files within given directory. Use option --fully to read the full file content.
`setprop <name> <value>` > Set system property _name_ to _value_. Properties are expanded within _value_.
`setrlimit <resource> <cur> <max>` > Set the rlimit for a resource. This applies to all processes launched after the limit is set. It is intended to be set early in init and applied globally. _resource_ is best specified using its text representation ('cpu', 'rtio', etc or 'RLIM_CPU', 'RLIM_RTIO', etc). It also may be specified as the int value that the resource enum corresponds to. _cur_ and _max_ can be 'unlimited' or '-1' to indicate an infinite rlimit.
`start <service>` > Start a service running if it is not already running. Note that this is _not_ synchronous, and even if it were, there is no guarantee that the operating system's scheduler will execute the service sufficiently to guarantee anything about the service's status. See the `exec_start` command for a synchronous version of `start`.
> This creates an important consequence that if the service offers functionality to other services, such as providing a communication channel, simply starting this service before those services is _not_ sufficient to guarantee that the channel has been set up before those services ask for it. There must be a separate mechanism to make any such guarantees.
`stop <service>` > Stop a service from running if it is currently running.
`swapon_all [ <fstab> ]` > Calls fs\_mgr\_swapon\_all on the given fstab file. If the fstab parameter is not specified, fstab.${ro.boot.fstab_suffix}, fstab.${ro.hardware} or fstab.${ro.hardware.platform} will be scanned for under /odm/etc, /vendor/etc, or / at runtime, in that order.
`symlink <target> <path>` > Create a symbolic link at _path_ with the value _target_
`sysclktz <minutes_west_of_gmt>` > Set the system clock base (0 if system clock ticks in GMT)
`trigger <event>` > Trigger an event. Used to queue an action from another action.
`umount <path>` > Unmount the filesystem mounted at that path.
`umount_all [ <fstab> ]` > Calls fs\_mgr\_umount\_all on the given fstab file. If the fstab parameter is not specified, fstab.${ro.boot.fstab_suffix}, fstab.${ro.hardware} or fstab.${ro.hardware.platform} will be scanned for under /odm/etc, /vendor/etc, or / at runtime, in that order.
`verity_update_state` > Internal implementation detail used to update dm-verity state and set the partition._mount-point_.verified properties used by adb remount because fs\_mgr can't set them directly itself. This is required since Android 12, because CtsNativeVerifiedBootTestCases will read property "partition.${partition}.verified.hash_alg" to check that sha1 is not used. See https://r.android.com/1546980 for more details.
`wait <path> [ <timeout> ]` > Poll for the existence of the given file and return when found, or the timeout has been reached. If timeout is not specified it currently defaults to five seconds. The timeout value can be fractional seconds, specified in floating point notation.
`wait_for_prop <name> <value>` > Wait for system property _name_ to be _value_. Properties are expanded within _value_. If property _name_ is already set to _value_, continue immediately.
`write <path> <content>` > Open the file at _path_ and write a string to it with write(2). If the file does not exist, it will be created. If it does exist, it will be truncated. Properties are expanded within _content_.
Imports ------- `import <path>` > Parse an init config file, extending the current configuration. If _path_ is a directory, each file in the directory is parsed as a config file. It is not recursive, nested directories will not be parsed.
The import keyword is not a command, but rather its own section, meaning that it does not happen as part of an Action, but rather, imports are handled as a file is being parsed and follow the below logic.
There are only three times where the init executable imports .rc files:
1. When it imports `/system/etc/init/hw/init.rc` or the script indicated by the property `ro.boot.init_rc` during initial boot. 2. When it imports `/{system,system_ext,vendor,odm,product}/etc/init/` immediately after importing `/system/etc/init/hw/init.rc`. 3. (Deprecated) When it imports /{system,vendor,odm}/etc/init/ or .rc files at specified paths during mount_all, not allowed for devices launching after Q.
The order that files are imported is a bit complex for legacy reasons. The below is guaranteed:
1. `/system/etc/init/hw/init.rc` is parsed then recursively each of its imports are parsed. 2. The contents of `/system/etc/init/` are alphabetized and parsed sequentially, with imports happening recursively after each file is parsed. 3. Step 2 is repeated for `/system_ext/etc/init`, `/vendor/etc/init`, `/odm/etc/init`, `/product/etc/init`
The below pseudocode may explain this more clearly:
fn Import(file) Parse(file) for (import : file.imports) Import(import)
Import(/system/etc/init/hw/init.rc) Directories = [/system/etc/init, /system_ext/etc/init, /vendor/etc/init, /odm/etc/init, /product/etc/init] for (directory : Directories) files = <Alphabetical order of directory's contents> for (file : files) Import(file)
Actions are executed in the order that they are parsed. For example the `post-fs-data` action(s) in `/system/etc/init/hw/init.rc` are always the first `post-fs-data` action(s) to be executed in order of how they appear in that file. Then the `post-fs-data` actions of the imports of `/system/etc/init/hw/init.rc` in the order that they're imported, etc.
Properties ---------- Init provides state information with the following properties.
`init.svc.<name>` > State of a named service ("stopped", "stopping", "running", "restarting")
`dev.mnt.dev.<mount_point>`, `dev.mnt.blk.<mount_point>`, `dev.mnt.rootdisk.<mount_point>` > Block device base name associated with a *mount_point*. The *mount_point* has / replaced by . and if referencing the root mount point "/", it will use "/root". `dev.mnt.dev.<mount_point>` indicates a block device attached to filesystems. (e.g., dm-N or sdaN/mmcblk0pN to access `/sys/fs/ext4/${dev.mnt.dev.<mount_point>}/`)
`dev.mnt.blk.<mount_point>` indicates the disk partition to the above block device. (e.g., sdaN / mmcblk0pN to access `/sys/class/block/${dev.mnt.blk.<mount_point>}/`)
`dev.mnt.rootdisk.<mount_point>` indicates the root disk to contain the above disk partition. (e.g., sda / mmcblk0 to access `/sys/class/block/${dev.mnt.rootdisk.<mount_point>}/queue`)
Init responds to properties that begin with `ctl.`. These properties take the format of `ctl.[<target>_]<command>` and the _value_ of the system property is used as a parameter. The _target_ is optional and specifies the service option that _value_ is meant to match with. There is only one option for _target_, `interface` which indicates that _value_ will refer to an interface that a service provides and not the service name itself.
For example:
`SetProperty("ctl.start", "logd")` will run the `start` command on `logd`.
`SetProperty("ctl.interface_start", "aidl/aidl_lazy_test_1")` will run the `start` command on the service that exposes the `aidl aidl_lazy_test_1` interface.
Note that these properties are only settable; they will have no value when read.
The _commands_ are listed below.
`start` \ `restart` \ `stop` \ These are equivalent to using the `start`, `restart`, and `stop` commands on the service specified by the _value_ of the property.
`oneshot_on` and `oneshot_off` will turn on or off the _oneshot_ flag for the service specified by the _value_ of the property. This is particularly intended for services that are conditionally lazy HALs. When they are lazy HALs, oneshot must be on, otherwise oneshot should be off.
`sigstop_on` and `sigstop_off` will turn on or off the _sigstop_ feature for the service specified by the _value_ of the property. See the _Debugging init_ section below for more details about this feature.
Boot timing ----------- Init records some boot timing information in system properties.
`ro.boottime.init` > Time after boot in ns (via the CLOCK\_BOOTTIME clock) at which the first stage of init started.
`ro.boottime.init.first_stage` > How long in ns it took to run first stage.
`ro.boottime.init.selinux` > How long in ns it took to run SELinux stage.
`ro.boottime.init.modules` > How long in ms it took to load kernel modules.
`ro.boottime.init.cold_boot_wait` > How long init waited for ueventd's coldboot phase to end.
`ro.boottime.<service-name>` > Time after boot in ns (via the CLOCK\_BOOTTIME clock) that the service was first started.
Bootcharting ------------ This version of init contains code to perform "bootcharting": generating log files that can be later processed by the tools provided by <http://www.bootchart.org/>.
On the emulator, use the -bootchart _timeout_ option to boot with bootcharting activated for _timeout_ seconds.
On a device:
adb shell 'touch /data/bootchart/enabled'
Don't forget to delete this file when you're done collecting data!
The log files are written to /data/bootchart/. A script is provided to retrieve them and create a bootchart.tgz file that can be used with the bootchart command-line utility:
One thing to watch for is that the bootchart will show init as if it started running at 0s. You'll have to look at dmesg to work out when the kernel actually started init.
Comparing two bootcharts ------------------------ A handy script named compare-bootcharts.py can be used to compare the start/end time of selected processes. The aforementioned grab-bootchart.sh will leave a bootchart tarball named bootchart.tgz at /tmp/android-bootchart. If two such tarballs are preserved on the host machine under different directories, the script can list the timestamps differences. For example:
process: baseline experiment (delta) - Unit is ms (a jiffy is 10 ms on the system) ------------------------------------ /init: 50 40 (-10) /system/bin/surfaceflinger: 4320 4470 (+150) /system/bin/bootanimation: 6980 6990 (+10) zygote64: 10410 10640 (+230) zygote: 10410 10640 (+230) system_server: 15350 15150 (-200) bootanimation ends at: 33790 31230 (-2560)
Systrace -------- Systrace (<http://developer.android.com/tools/help/systrace.html>) can be used for obtaining performance analysis reports during boot time on userdebug or eng builds.
Here is an example of trace events of "wm" and "am" categories:
$ANDROID_BUILD_TOP/external/chromium-trace/systrace.py \ wm am --boot
This command will cause the device to reboot. After the device is rebooted and the boot sequence has finished, the trace report is obtained from the device and written as trace.html on the host by hitting Ctrl+C.
Limitation: recording trace events is started after persistent properties are loaded, so the trace events that are emitted before that are not recorded. Several services such as vold, surfaceflinger, and servicemanager are affected by this limitation since they are started before persistent properties are loaded. Zygote initialization and the processes that are forked from the zygote are not affected.
Debugging init -------------- When a service starts from init, it may fail to `execv()` the service. This is not typical, and may point to an error happening in the linker as the new service is started. The linker in Android prints its logs to `logd` and `stderr`, so they are visible in `logcat`. If the error is encountered before it is possible to access `logcat`, the `stdio_to_kmsg` service option may be used to direct the logs that the linker prints to `stderr` to `kmsg`, where they can be read via a serial port.
Launching init services without init is not recommended as init sets up a significant amount of environment (user, groups, security label, capabilities, etc) that is hard to replicate manually.
If it is required to debug a service from its very start, the `sigstop` service option is added. This option will send SIGSTOP to a service immediately before calling exec. This gives a window where developers can attach a debugger, strace, etc before continuing the service with SIGCONT.
This flag can also be dynamically controlled via the ctl.sigstop_on and ctl.sigstop_off properties.
Below is an example of dynamically debugging logd via the above:
stop logd setprop ctl.sigstop_on logd start logd ps -e | grep logd > logd 4343 1 18156 1684 do_signal_stop 538280 T init gdbclient.py -p 4343 b main c c c > Breakpoint 1, main (argc=1, argv=0x7ff8c9a488) at system/core/logd/main.cpp:427
Below is an example of doing the same but with strace
Init scripts are checked for correctness during build time. Specifically the below is checked.
1) Well formatted action, service and import sections, e.g. no actions without a preceding 'on' line, and no extraneous lines after an 'import' statement. 2) All commands map to a valid keyword and the argument count is within the correct range. 3) All service options are valid. This is stricter than how commands are checked as the service options' arguments are fully parsed, e.g. UIDs and GIDs must resolve.
There are other parts of init scripts that are only parsed at runtime and therefore not checked during build time, among them are the below.
1) The validity of the arguments of commands, e.g. no checking if file paths actually exist, if SELinux would permit the operation, or if the UIDs and GIDs resolve. 2) No checking if a service exists or has a valid SELinux domain defined 3) No checking if a service has not been previously defined in a different init script.
Early Init Boot Sequence ------------------------ The early init boot sequence is broken up into three stages: first stage init, SELinux setup, and second stage init.
First stage init is responsible for setting up the bare minimum requirements to load the rest of the system. Specifically this includes mounting /dev, /proc, mounting 'early mount' partitions (which needs to include all partitions that contain system code, for example system and vendor), and moving the system.img mount to / for devices with a ramdisk.
Note that in Android Q, system.img always contains TARGET_ROOT_OUT and always is mounted at / by the time first stage init finishes. Android Q will also require dynamic partitions and therefore will require using a ramdisk to boot Android. The recovery ramdisk can be used to boot to Android instead of a dedicated ramdisk as well.
First stage init has three variations depending on the device configuration: 1) For system-as-root devices, first stage init is part of /system/bin/init and a symlink at /init points to /system/bin/init for backwards compatibility. These devices do not need to do anything to mount system.img, since it is by definition already mounted as the rootfs by the kernel.
2) For devices with a ramdisk, first stage init is a static executable located at /init. These devices mount system.img as /system then perform a switch root operation to move the mount at /system to /. The contents of the ramdisk are freed after mounting has completed.
3) For devices that use recovery as a ramdisk, first stage init it contained within the shared init located at /init within the recovery ramdisk. These devices first switch root to /first_stage_ramdisk to remove the recovery components from the environment, then proceed the same as 2). Note that the decision to boot normally into Android instead of booting into recovery mode is made if androidboot.force_normal_boot=1 is present in the kernel commandline, or in bootconfig with Android S and later.
Once first stage init finishes it execs /system/bin/init with the "selinux_setup" argument. This phase is where SELinux is optionally compiled and loaded onto the system. selinux.cpp contains more information on the specifics of this process.
Lastly once that phase finishes, it execs /system/bin/init again with the "second_stage" argument. At this point the main phase of init runs and continues the boot process via the init.rc scripts.
stop logd setprop ctl.sigstop_on logd start logd ps -e | grep logd > logd 4343 1 18156 1684 do_signal_stop 538280 T init gdbclient.py -p 4343 b main c c c > Breakpoint 1, main (argc=1, argv=0x7ff8c9a488) at system/core/logd/main.cpp:427
class Test { public Test(){} public int show(String msg, int number) { System.out.println("msg: " + msg); System.out.println("number: " + number); return 0; } }
07-12 14:57:07.443 26623-26623/com.afei.jnidemo D/FaceAPI: ============ 07-12 14:57:07.443 26623-26623/com.afei.jnidemo W/System.err: java.lang.NullPointerException: MainActivity NullPointerException at com.afei.jnidemo.MainActivity.callNullPointerException(MainActivity.java:34) at com.afei.jnidemo.MainActivity.test(Native Method) at com.afei.jnidemo.MainActivity.onCreate(MainActivity.java:25) at android.app.Activity.performCreate(Activity.java:6857) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1125) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2702) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2810) at android.app.ActivityThread.-wrap12(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1532) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:181) at android.app.ActivityThread.main(ActivityThread.java:6288) at java.lang.reflect.Method.invoke(Native Method) 07-12 14:57:07.443 26623-26623/com.afei.jnidemo W/System.err: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:900) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:790) 07-12 14:57:07.443 26623-26623/com.afei.jnidemo D/FaceAPI: ============ 07-12 14:57:07.444 26623-26623/com.afei.jnidemo E/MainActivity: onCreate: java.lang.IllegalArgumentException: throw from JNI
可以看出来第一列是分区挂载的位置，第二列是哪个分区，第三列属于分区格式
super分区除了包含
可以看到该设备使用的是tmpfs文件系统，以及可以看到属于tmpfs文件系统的分区，大小信息等,还有一个命令也可以查看，比较简约
可以观察到vendor.img镜像被挂载到了/vendor分区上，使用的设备文件是
