Create Makefile (yes i know it doesnt work yet) and boot.s

1 files changed, 57 insertions, 0 deletions

diff --git a/boot.s b/boot.s
new file mode 100644
index 0000000..592ba46
--- /dev/null
+++ b/boot.s
@@ -0,0 +1,57 @@
+/* Multiboot header dark magic, do not touch */
+.set ALIGN, 1<<0
+.set MEMINFO, 1<<1
+.set FLAGS, ALIGN | MEMINFO
+.set MAGIC, 0x1BADB002
+.set CHECKSUM, -(MAGIC + FLAGS)
+
+.section .multiboot 
+.align 4
+.long MAGIC
+.long FLAGS
+.long CHECKSUM
+
+/* Multiboot does not define the esp/stack, create the stack ourselves */
+.section bss
+/* Stack on x86 must be 16-byte aligned by the System V ABI standard */
+.align 16
+/* Create a symbol at the bottom, allocate 16KiB, then finally create a symbol at the top */
+stack_bottom:
+.skip 16384
+stack_top:
+
+/* _start is the entrypoint */
+.section text
+.global _start
+.type _start, @function
+_start:
+	/* we are in 32bit protected mode
+	interrupts disabled, paging disabled
+	kernel has full control over cpu */
+
+	/* setup the stack, point to the top becausei t grows downwrad on x86 for som e reason */
+	mov $stack_top, %esp
+
+	/* here we need to init crucial processor state.
+	load the gdt, enable pages, init isa extensions/floating point instructions and stuff
+	for now just dont do anything we'll add that later */
+
+	/* enter the high level kernel
+	ABI says we need 16-byte alignment here, we aligned that before and pushed a multiple of 16 bits (zero) so we fine
+	but i will realign for good measure anyway */
+	.align 16 
+	call kernel_main
+
+	/* if nothing left then just infinite loop */
+	/*
+	1. disable interrupts with cli/clear interrupts 
+	2. wait for next interrupt with hlt. because they disabled this will just lockup the ocmputer
+	3. justincase it wakes up just jmp back to the hlt instruction
+	*/
+	cli
+1:	hlt
+	jmp 1b
+
+/* set the size of the _start symbol to the current location (.) minus it's _start 
+for debugging stuff */
+.size _start, . - _start