1 files changed, 94 insertions, 0 deletions
diff --git a/src/kernel/isrs.asm b/src/kernel/isrs.asm
new file mode 100644
index 0000000..163ddbe
--- /dev/null
+++ b/src/kernel/isrs.asm
@@ -0,0 +1,94 @@
+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
+  push 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:
+  push dword 0x2b
+  sub esp, 4
+  push dword 0x00000200;interrupt flag
+  push dword 0x23
+  sub esp, 4
+  jmp yield_isr.return_to_task
+\ No newline at end of file