diff options
Diffstat (limited to 'src/boot.s')
| -rw-r--r-- | src/boot.s | 80 |
1 files changed, 80 insertions, 0 deletions
diff --git a/src/boot.s b/src/boot.s new file mode 100644 index 0000000..71017ff --- /dev/null +++ b/src/boot.s @@ -0,0 +1,80 @@ +/* Parameters for the multiboot header */ +.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 + + +/* Allocate room for stack */ +.section bss +.align 16 +stack_bottom: +.skip 16384 /* 16 KiB */ +stack_top: + +.section .data + +.intel_syntax noprefix +gdt: + null_gdt: /* null descriptor */ + .quad 0x00 + + code_gdt: + .word 0xFFFF /* limit */ + .word 0x0000 /* base */ + .byte 0x00 /* base */ + .byte 0x9A /* type flag (access) */ + .byte 0b11001111 /* limit */ + .byte 0x00 /* base */ + + data_gdt: + .word 0xFFFF /* limit */ + .word 0x0000 /* base */ + .byte 0x00 /* base */ + .byte 0x92 /* type flag (access) */ + .byte 0b11001111 /* limit */ + .byte 0x00 /* base */ + + end_gdt: + + gdt_desc: + .word end_gdt - gdt - 1 + .int gdt + +.att_syntax + +.section .text +.global _start +.type _start, @function +_start: + mov $stack_top, %esp + + cli + +.intel_syntax noprefix + lgdt [gdt_desc] /* load GDT */ + mov ax, 0x10 + mov ds, ax + mov ss, ax + mov es, ax + mov fs, ax + mov gs, ax + jmp 0x08:continue +.att_syntax + +continue: + call kernel_main + + cli +1: hlt + jmp 1b + +/* The size of the _start symbol is the current location '.' minus its start. */ +.size _start, . - _start |