4. Linux Startup
We start the Linux kernel first from C code executed from ''startup_32:'' asm label:
|startup_32:
|start_kernel
|lock_kernel
|trap_init
|init_IRQ
|sched_init
|softirq_init
|time_init
|console_init
|#ifdef CONFIG_MODULES
|init_modules
|#endif
|kmem_cache_init
|sti
|calibrate_delay
|mem_init
|kmem_cache_sizes_init
|pgtable_cache_init
|fork_init
|proc_caches_init
|vfs_caches_init
|buffer_init
|page_cache_init
|signals_init
|#ifdef CONFIG_PROC_FS
|proc_root_init
|#endif
|#if defined(CONFIG_SYSVIPC)
|ipc_init
|#endif
|check_bugs
|smp_init
|rest_init
|kernel_thread
|unlock_kernel
|cpu_idle
- startup_32 [arch/i386/kernel/head.S]
- start_kernel [init/main.c]
- lock_kernel [include/asm/smplock.h]
- trap_init [arch/i386/kernel/traps.c]
- init_IRQ [arch/i386/kernel/i8259.c]
- sched_init [kernel/sched.c]
- softirq_init [kernel/softirq.c]
- time_init [arch/i386/kernel/time.c]
- console_init [drivers/char/tty_io.c]
- init_modules [kernel/module.c]
- kmem_cache_init [mm/slab.c]
- sti [include/asm/system.h]
- calibrate_delay [init/main.c]
- mem_init [arch/i386/mm/init.c]
- kmem_cache_sizes_init [mm/slab.c]
- pgtable_cache_init [arch/i386/mm/init.c]
- fork_init [kernel/fork.c]
- proc_caches_init
- vfs_caches_init [fs/dcache.c]
- buffer_init [fs/buffer.c]
- page_cache_init [mm/filemap.c]
- signals_init [kernel/signal.c]
- proc_root_init [fs/proc/root.c]
- ipc_init [ipc/util.c]
- check_bugs [include/asm/bugs.h]
- smp_init [init/main.c]
- rest_init
- kernel_thread [arch/i386/kernel/process.c]
- unlock_kernel [include/asm/smplock.h]
- cpu_idle [arch/i386/kernel/process.c]
The last function ''rest_init'' does the following:
- launches the kernel thread ''init''
- calls unlock_kernel
- makes the kernel run cpu_idle routine, that will be the idle loop executing when nothing is scheduled
In fact the start_kernel procedure never ends. It will execute cpu_idle routine endlessly.
Follows ''init'' description, which is the first Kernel Thread:
|init
|lock_kernel
|do_basic_setup
|mtrr_init
|sysctl_init
|pci_init
|sock_init
|start_context_thread
|do_init_calls
|(*call())-> kswapd_init
|prepare_namespace
|free_initmem
|unlock_kernel
|execve
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