mohitmishra786 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.gitfor a feature or bug - Understanding how boot reaches
initand driverprobe - Tracing a syscall or interrupt through subsystems
- Onboarding before
skills/kernel-dev/platform-device-modelor 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
/* include/linux/init.h — order matters */
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
# Locate symbol
grep -rn "platform_driver_register" drivers/
# Trace config
./scripts/config --state CONFIG_FOO
# File hierarchy docs
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