kernel/kernel.asm at master · menyet/kernel · GitHub

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;;kernel.asm

;nasm directive - 32 bit
bits 32
section .text
        ;multiboot spec
        align 4
        dd 0x1BADB002            ;magic
        dd 0x00                  ;flags
        dd - (0x1BADB002 + 0x00) ;checksum. m+f+c should be zero

global start
extern kmain	        ;kmain is defined in the c file

start:
  cli 			;block interrupts
  call kmain
  hlt		 	;halt the CPU

[GLOBAL idt_flush]    ; Allows the C code to call idt_flush().

idt_flush:
   mov eax, [esp+4]  ; Get the pointer to the IDT, passed as a parameter.
   lidt [eax]        ; Load the IDT pointer.
   ret

 ; In isr.c
[EXTERN isr_handler]

; This is our common ISR stub. It saves the processor state, sets
; up for kernel mode segments, calls the C-level fault handler,
; and finally restores the stack frame.
isr_common_stub:
   pusha                    ; Pushes edi,esi,ebp,esp,ebx,edx,ecx,eax

   mov ax, ds               ; Lower 16-bits of eax = ds.
   push eax                 ; save the data segment descriptor

   mov ax, 0x10  ; load the kernel data segment descriptor
   mov ds, ax
   mov es, ax
   mov fs, ax
   mov gs, ax

   call isr_handler

   pop eax        ; reload the original data segment descriptor
   mov ds, ax
   mov es, ax
   mov fs, ax
   mov gs, ax

   popa                     ; Pops edi,esi,ebp...
   add esp, 8     ; Cleans up the pushed error code and pushed ISR number
   sti
   iret           ; pops 5 things at once: CS, EIP, EFLAGS, SS, and ESP


%macro ISR_NOERRCODE 1  ; define a macro, taking one parameter
  [GLOBAL isr%1]        ; %1 accesses the first parameter.
  isr%1:
    cli
    push byte 0
    push byte %1
    jmp isr_common_stub
%endmacro

%macro ISR_ERRCODE 1
  [GLOBAL isr%1]
  isr%1:
    cli
    push byte %1
    jmp isr_common_stub
%endmacro

ISR_NOERRCODE 0
ISR_NOERRCODE 1
ISR_NOERRCODE 2
ISR_NOERRCODE 3
ISR_NOERRCODE 4
ISR_NOERRCODE 5
ISR_NOERRCODE 6
ISR_NOERRCODE 7
ISR_NOERRCODE 8
ISR_NOERRCODE 9
ISR_NOERRCODE 10
ISR_NOERRCODE 11
ISR_NOERRCODE 12
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ISR_NOERRCODE 14
ISR_NOERRCODE 15
ISR_NOERRCODE 16
ISR_NOERRCODE 17
ISR_NOERRCODE 18
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ISR_NOERRCODE 20
ISR_NOERRCODE 21
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ISR_NOERRCODE 23
ISR_NOERRCODE 24
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ISR_NOERRCODE 31