repository·main·Indexed 22 days ago
https://github.com/aosp-mirror/platform_system_coreCore system components and tools from the AOSP mirror, including bootstat for recording and logging boot event metrics, cli-test for command-line tool integration testing, and fastboot utilities such as the fastboot_fuzzer and Fuzzy Fastboot for automated conformance and penetration testing of device-side fastboot protocol implementations.
Android's command-line environment has evolved from using a custom toolbox binary to primarily using toybox for most utilities. The shell itself has used mksh since IceCreamSandwich.
Key components include:
mksh (since IceCreamSandwich).toybox provides the majority of command-line tools.bzip2 tools, awk (one-true-awk), and bc (Gavin Howard's bc).getevent, getprop, setprop, start, and stop are provided by the toolbox binary.The Android Init Language is a line-oriented configuration language used to define system behavior. It consists of five main classes of statements:
init process..rc files.\) to insert whitespace into a token or for line-folding (if \ is the last character on a line)."") to prevent whitespace from breaking text into multiple tokens.# (leading whitespace allowed) are comments.${property.name}. This is useful for concatenation, e.g., import /init.recovery.${ro.hardware}.rc.The Android Live-LocK Daemon (llkd) is a component designed to catch and mitigate kernel deadlocks. It provides a default standalone implementation, but developers can also integrate the llkd code into other services as part of a main loop or as a separate thread using the libllkd library.
llkd uses two primary detection scenarios:
llkd kills the process. If the process persists, it triggers a kernel panic to provide a detailed bug report.userdebug or eng builds only). Monitors threads for specific kernel symbols in their stack (via /proc/pid/stack). If a listed symbol persists longer than the timeout, llkd kills the process and may trigger a kernel panic.libfiemap is a library designed to create block devices backed by storage in read-write partitions. It is primarily used by gsid to manage Dynamic System Updates. The library works by using libfiemap_writer to allocate large files within a filesystem and then tracking their extents.
Key use cases include:
system_gsi image)./data is mounted.The fastboot protocol is a host-driven, synchronous mechanism for communicating with bootloaders over USB or Ethernet (TCP/UDP). It is designed to be straightforward to implement across various platforms including Linux, macOS, and Windows.
On devices using metadata encryption, /data is mounted from an intermediate dm-default-key device rather than directly from /dev/block/by-name/data. Because the underlying device is not marked as in-use, libfiemap can create new dm-linear devices on top of it.
In this scenario, the block device for an image consists of a single device-mapper device containing a dm-linear table entry for each extent in the backing file.
Actions are named sequences of commands triggered by an event. When a trigger matches, the action is added to a execution queue.
on <trigger> [&& <trigger>]*
<command>
<command>&&, all must be true at the moment of the trigger event.ro.property_service.async_persist_writes is true, there is no guaranteed ordering between persistent (persist.*) and non-persistent setprop commands within an action.on boot
setprop a 1
setprop b 2
on boot && property:true=true
setprop c 1
setprop d 2Triggers define when an action (a set of commands) should execute. They consist of event triggers and property triggers.
early-init, boot). Satisfied when init reaches that stage.property:<name>=<value>. Satisfied when a property matches a value. Use * as a wildcard.Multiple triggers can be combined using the && (AND) operator.
boot event finishes.property:a=b is checked whenever a is created or changed to b.property:a=b && property:c=d, the action triggers if:a becomes b while c is already d.c becomes d while a is already b.on property:a=b && post-fs only executes if post-fs is triggered while a is already b. It will NOT trigger if a becomes b after post-fs has already occurred.Services are programs that init launches and can optionally restart if they exit.
service <name> <pathname> [ <argument> ]*
<option>
<option>
...To prevent catastrophic data corruption (e.g., writing to a dm-linear device whose underlying blocks are no longer owned by the original file), libfiemap implements state tracking:
gsid.mapped_image.<name> is created and set to the path of the block device./metadata/gsi/<subdir>/<name>.status. Each line in this file denotes a dependency on either a device-mapper node or a loop device..status file to ensure all associated resources (loop devices or device-mapper nodes) are properly released.The Fastboot UDP protocol provides a reliable communication layer over UDP. The device listens on UDP port 5554. Communication is host-driven: the device only sends packets in response to a host packet. If the host does not receive a response within 500ms, it re-transmits.
Each UDP packet follows this format:
| Byte # | 0 | 1 | 2 - 3 | 4+ |
|---|---|---|---|---|
| Contents | ID | Flags | Seq # | Data |
0x00: Error0x01: Query0x02: Initialization0x03: FastbootC) is the continuation flag. If C=1, the data is too large and continues in the next packet. All other bits must be 0.