openharmony/kernel_liteos_a

Purpose and build surface

OpenHarmony LiteOS Cortex-A is a C/C++ embedded OS kernel for ARM Cortex-A/Hi3516D V300-class targets, providing POSIX-facing process, memory, IPC, filesystem, networking, driver, and security services. Builds are selected through GN/Make/Kconfig layers: BUILD.gn, Kconfig, build.sh, and liteos.gni.

Boot and execution entry points

ARM reset vectors establish CPU execution, then common kernel startup initializes core subsystems and launches user initialization. Key entry points are arch/arm/arm/src/startup/reset_vector_up.S, kernel/common/main.c, kernel/common/los_init.c, and kernel/user/src/los_user_init.c. The configured init application is apps/init/src/init.c; interactive shell implementations live in shell/full/src/base/shcmd.c and apps/shell/src/main.c.

Architecture and hardware boundary

The ARM port owns exceptions, interrupts, MMU/ASID handling, tick timing, SMP, and context dispatch. Hardware-specific code is isolated below kernel APIs in arch/arm/arm/src/los_arch_mmu.c, arch/arm/arm/src/los_hwi.c, arch/arm/arm/src/los_dispatch.S, and GIC drivers arch/arm/gic/gic_v2.c / arch/arm/gic/gic_v3.c. Platform/linker integration is supplied by platform/board.ld.S and platform/bsp.mk.

Kernel core: scheduling, processes, memory, IPC

The core kernel manages tasks/processes, priority/deadline scheduling, timers, physical/virtual memory, and synchronization. Primary paths are kernel/base/core/los_task.c, kernel/base/core/los_process.c, kernel/base/sched/los_sched.c, kernel/base/mem/tlsf/los_memory.c, and kernel/base/vm/los_vm_map.c. IPC objects—events, queues, mutexes, semaphores, futexes, signals—are kernel-resident in kernel/base/ipc/los_event.c, kernel/base/ipc/los_queue.c, and kernel/base/ipc/los_signal.c.

User/kernel ABI and compatibility

Applications reach privileged services through syscall dispatch and POSIX adaptation rather than directly through kernel internals. The syscall boundary is defined by syscall/los_syscall.c, syscall/syscall_lookup.h, and domain handlers such as syscall/fs_syscall.c. POSIX APIs map onto LiteOS primitives in compat/posix/src/pthread.c, compat/posix/src/socket.c, and compat/posix/src/mqueue.c; libc options include musl/newlib under lib/libc/.

Storage, filesystems, and devices

The VFS provides pathname, mount, vnode, descriptor, polling, and filesystem-operation abstractions over FAT, JFFS2, procfs, ramfs, rootfs, NFS, and other enabled filesystems. Its central boundary is fs/vfs/vnode.c, fs/vfs/mount.c, and fs/vfs/operation/vfs_init.c; root filesystem setup is fs/rootfs/los_rootfs.c. Block/MTD and character drivers feed this layer through drivers/block/disk/src/disk.c, drivers/mtd/multi_partition/src/mtd_partition.c, and device drivers under drivers/char/.

Networking, USB, and external stacks

Networking is based on lwIP 2.1, ported to LiteOS scheduling, driver interfaces, and sockets through net/lwip-2.1/porting/src/sys_arch.c, net/lwip-2.1/porting/src/driverif.c, and net/lwip-2.1/porting/src/sockets.c. Telnet and TFTP are optional user-facing network services in net/telnet/src/telnet_loop.c and apps/tftp/src/tftpc.c. USB is a FreeBSD-derived subsystem with EHCI/XHCI controllers and class drivers, centered on bsd/dev/usb/usb_core.c, bsd/dev/usb/implementation/usb_init.c, and bsd/dev/usb/controller/xhci.c.

Extended facilities and security

Optional kernel extensions add ELF dynamic loading, vDSO, lightweight IPC, containers/resource limits, tracing, performance monitoring, power management, and diagnostics. Architecturally significant paths include kernel/extended/dynload/src/los_exec_elf.c, kernel/extended/liteipc/hm_liteipc.c, kernel/extended/container/los_container.c, kernel/extended/trace/los_trace.c, and kernel/extended/perf/los_perf.c. Capability and virtual-ID security enforcement reside in security/cap/capability.c and security/vid/vid.c; mbedTLS, zlib, and BSD crypto are bundled libraries under lib/libmbedtls/, lib/zlib/, and bsd/crypto/.