init

boot.s

@@ -16,74 +16,16 @@ stack_bottom:
 .skip 16384 # 16 KiB
 stack_top:
 
-/*
-The linker script specifies _start as the entry point to the kernel and the
-bootloader will jump to this position once the kernel has been loaded. It
-doesn't make sense to return from this function as the bootloader is gone.
-*/
 .section .text
 .global _start
 .type _start, @function
 _start:
-	/*
-	The bootloader has loaded us into 32-bit protected mode on a x86
-	machine. Interrupts are disabled. Paging is disabled. The processor
-	state is as defined in the multiboot standard. The kernel has full
-	control of the CPU. The kernel can only make use of hardware features
-	and any code it provides as part of itself. There's no printf
-	function, unless the kernel provides its own <stdio.h> header and a
-	printf implementation. There are no security restrictions, no
-	safeguards, no debugging mechanisms, only what the kernel provides
-	itself. It has absolute and complete power over the
-	machine.
-	*/
-
-	/*
-	To set up a stack, we set the esp register to point to the top of the
-	stack (as it grows downwards on x86 systems). This is necessarily done
-	in assembly as languages such as C cannot function without a stack.
-	*/
 	mov $stack_top, %esp
 
-	/*
-	This is a good place to initialize crucial processor state before the
-	high-level kernel is entered. It's best to minimize the early
-	environment where crucial features are offline. Note that the
-	processor is not fully initialized yet: Features such as floating
-	point instructions and instruction set extensions are not initialized
-	yet. The GDT should be loaded here. Paging should be enabled here.
-	C++ features such as global constructors and exceptions will require
-	runtime support to work as well.
-	*/
-
-	/*
-	Enter the high-level kernel. The ABI requires the stack is 16-byte
-	aligned at the time of the call instruction (which afterwards pushes
-	the return pointer of size 4 bytes). The stack was originally 16-byte
-	aligned above and we've pushed a multiple of 16 bytes to the
-	stack since (pushed 0 bytes so far), so the alignment has thus been
-	preserved and the call is well defined.
-	*/
 	call kernel_main
 
-	/*
-	If the system has nothing more to do, put the computer into an
-	infinite loop. To do that:
-	1) Disable interrupts with cli (clear interrupt enable in eflags).
-	   They are already disabled by the bootloader, so this is not needed.
-	   Mind that you might later enable interrupts and return from
-	   kernel_main (which is sort of nonsensical to do).
-	2) Wait for the next interrupt to arrive with hlt (halt instruction).
-	   Since they are disabled, this will lock up the computer.
-	3) Jump to the hlt instruction if it ever wakes up due to a
-	   non-maskable interrupt occurring or due to system management mode.
-	*/
 	cli
 1:	hlt
 	jmp 1b
 
-/*
-Set the size of the _start symbol to the current location '.' minus its start.
-This is useful when debugging or when you implement call tracing.
-*/
 .size _start, . - _start