1 files changed, 58 insertions, 0 deletions
diff --git a/src/kernel/core/context_switch.s b/src/kernel/core/context_switch.s
new file mode 100644
index 0000000..6738a03
--- /dev/null
+++ b/src/kernel/core/context_switch.s
@@ -0,0 +1,58 @@
+[EXTERN kernel_stack_top]
+[EXTERN run_scheduler]
+
+[GLOBAL save_context_and_enter_scheduler]
+; void save_context_and_enter_scheduler(struct saved_context *ctx);
+save_context_and_enter_scheduler:
+	pushf
+	cli
+	pusha					; Pushes edi,esi,ebp,esp,ebx,edx,ecx,eax
+
+	mov eax, cr3
+	push eax
+
+	mov eax, [esp+44]		; get address of saved_context structure
+	mov [eax], esp			; save esp
+	mov dword [eax+4], resume_saved_context		; save eip
+
+	mov esp, kernel_stack_top
+	jmp run_scheduler
+
+resume_saved_context:
+	pop eax
+	mov cr3, eax
+
+	popa
+	popf
+	ret
+
+[GLOBAL irq0_save_context_and_enter_scheduler]
+; meant to be called on IRQ0
+; general registers already saved by IRQ handler stub
+; flags already saved by interruption and interruptions disabled
+; only saves CR3
+irq0_save_context_and_enter_scheduler:
+	mov eax, cr3
+	push eax
+
+	mov eax, [esp+8]		; get address of saved_context structure
+	mov [eax], esp			; save esp
+	mov dword [eax+4], resume_saved_irq0_context		; save eip
+
+	mov esp, kernel_stack_top
+	jmp run_scheduler
+
+resume_saved_irq0_context:
+	pop eax
+	mov cr3, eax
+	ret
+
+
+[GLOBAL resume_context]
+resume_context:
+	mov eax, [esp+4]		; get address of saved context
+	mov esp, [eax]			; resume esp
+	mov ecx, [eax+4]		; jump to specified eip
+	jmp ecx
+
+; vim: set ts=4 sw=4 tw=0 noet :