init/main.c

start_kernel() performs most of the kernel setup:

• interrupts
• memory management
• device initialization
• drivers

start_kernel() also prints (pr_notice()) the value of linux_banner (defined in init/version.c and init/version-timestamp.c).

At least in my current Linux environment, this is the first message visible to dmesg.

The last function that start_kernel calls is arch_call_rest_init() which in turn calls rest_init() which apparently does not return.

start_kernel is defined with asmlinkage and declared in include/linux/start_kernel.h.

Compare with x86_64_start_kernel() (defined in arch/x86/kernel/head64.c)

This function is called when the machine is initialized and the CPU subsystem is started.

None of the devices have been touched at this moment.

This function opens, among others, /dev/console.

boot process