| name | linux-kernel-architecture |
| description | Linux kernel architecture skill for subsystem overview. Use when navigating kernel source, understanding boot flow, initcalls, or major subsystems (VFS, scheduler, MM). Activates on queries about kernel architecture, boot process, initcall levels, subsystem layout, or where code lives in linux.git. |
Linux Kernel Architecture
Purpose
Provide a mental map of the Linux kernel: boot sequence, major subsystems, key data structures, and where to look in source — complementing skills/kernel/kernel-internals with architecture-level navigation for driver and subsystem work.
When to Use
- First time exploring
linux.git for a feature or bug
- Understanding how boot reaches
init and driver probe
- Tracing a syscall or interrupt through subsystems
- Onboarding before
skills/kernel-dev/platform-device-model or driver skills
Workflow
1. Boot flow (x86/ARM64 simplified)
firmware/UEFI
├── arch/*/boot — decompress kernel, early setup
├── start_kernel() — mm, scheduler, timers, IRQ subsys
├── rest_init() → kernel_init → run_init_process
└── userspace init (systemd)
Driver module_init / device_initcall run during start_kernel before init.
2. Major subsystems
| Subsystem | Path (typical) | Key structs |
|---|
| Scheduler | kernel/sched/ | task_struct, sched_entity |
| Memory | mm/ | struct page, mm_struct, vm_area_struct |
| VFS | fs/ | inode, dentry, file, super_block |
| Block | block/ | request_queue, gendisk |
| Net | net/ | sk_buff, net_device |
| Drivers | drivers/ | device, device_driver |
| Syscalls | kernel/, fs/, mm/ | SYSCALL_DEFINE* |
3. Initcall levels
early_initcall → core_initcall → postcore_initcall
→ arch_initcall → subsys_initcall → fs_initcall
→ device_initcall → late_initcall
Platform drivers usually register at subsys_initcall or via module_init.
4. Finding code
grep -rn "platform_driver_register" drivers/
./scripts/config --state CONFIG_FOO
ls Documentation/admin-guide/
5. Agent usage
/linux-kernel-architecture Where does page fault handling live and what calls it?
Common Problems
| Symptom | Cause | Fix |
|---|
| Driver probes too early | Initcall vs DT ordering | Defer with deferred_probe |
| Symbol missing | Built as module | modprobe or built-in CONFIG_* |
| Wrong subsystem | Similar names in drivers/ | Follow struct bus_type |
| Boot hang | Early printk disabled | earlyprintk, initcall_debug |
Related Skills
skills/kernel/kernel-internals — scheduler, SLUB, VFS depthskills/kernel-dev/kernel-memory-management — mm/ detailsskills/kernel-dev/platform-device-model — driver modelskills/kernel-dev/device-tree — hardware descriptionskills/low-level-programming/linux-kernel-modules — LKM basics
