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bits 32
global syscall_isr
global quit_isr
global yield_isr
global _start_user_mode
extern syscall_table
extern active_task
extern delete_task
extern advance_active_task
n_syscalls equ 8
section .text
syscall_isr:
cmp eax, n_syscalls
jge .bad
mov eax, dword [syscall_table + eax * 4]
push edi
push esi
push edx
push ecx
push ebx
call eax
add esp, 20
iret
.bad:
mov eax, -1
iret
quit_isr:
push dword [active_task]
call delete_task
mov dword [esp], yield_isr.return_to_task
jmp advance_active_task
yield_isr:
mov eax, dword [active_task]
mov dword [eax + 8], ebx
mov dword [eax + 12], ecx
mov dword [eax + 16], edx
mov dword [eax + 20], esi
mov dword [eax + 24], edi
mov dword [eax + 28], ebp
mov edx, dword [esp]
mov dword [eax], edx
mov edx, cr3
mov dword [eax + 4], edx
mov edx, dword [esp + 12]
mov dword [eax + 4], edx
call advance_active_task
.return_to_task:
mov eax, dword [active_task]
mov edx, dword [eax]
mov dword [esp], edx
mov edx, dword [eax + 4]
mov cr3, edx
mov edx, dword [eax + 4]
mov dword [esp + 24], edx
mov ebx, dword [eax + 8]
mov ecx, dword [eax + 12]
mov edx, dword [eax + 16]
mov esi, dword [eax + 20]
mov edi, dword [eax + 24]
mov ebp, dword [eax + 28]
_before_start_task:
iret
_start_user_mode:
mov ax, 0x2b
mov ds, ax
push dword 0x2b
sub esp, 4
push dword 0x00000200;interrupt flag
push dword 0x23
sub esp, 4
jmp yield_isr.return_to_task
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