From 4f94ccdc9912f0b21792dabca652dba4b2550f02 Mon Sep 17 00:00:00 2001
From: Christoph Urlacher <christoph.urlacher@protonmail.com>
Date: Mon, 23 May 2022 09:11:59 +0200
Subject: [PATCH] implement asm coroutine

---
 c_os/kernel/corouts/Coroutine.asm | 68 +++++++++++++++++++++++++++++--
 1 file changed, 64 insertions(+), 4 deletions(-)

diff --git a/c_os/kernel/corouts/Coroutine.asm b/c_os/kernel/corouts/Coroutine.asm
index 07ceb56..2e38a75 100755
--- a/c_os/kernel/corouts/Coroutine.asm
+++ b/c_os/kernel/corouts/Coroutine.asm
@@ -27,25 +27,85 @@
 ;
 ; C Prototyp: void Coroutine_start (struct CoroutineState* regs);
 
+;; Coroutine_start is called with one arg: CoroutineState* regs, so the main stack looks like this:
+;; == High address ==
+;;      *REGS
+;; SP:  RET ADDR
+;; == Low address ==
 Coroutine_start:
-
 ; *
 ; * Hier muss Code eingefuegt werden
 ; *
 
+    ;; Set eax to the address where the CoroutineState struct is in memory:
+    mov eax, [esp + 0x4]
+
+    ;; Now eax points to the beginning of CoroutineState:
+    ;; struct CoroutineState {
+    ;; == Low address ==
+    ;; EAX: void *ebx;
+    ;;      void *esi;
+    ;;      void *edi;
+    ;;      void *ebp;
+    ;;      void *esp;
+    ;; == High address ==
+    ;; };
+
+    ;; Load the contents of CoroutineState to the registers
+    mov esp, [eax + esp_offset]
+
+    ;; The stackpointer now points to the coroutine stack
+    ;; struct CoroutineState {
+    ;; == High address ==
+    ;;     *OBJECT
+    ;;     0x13115
+    ;; SP: *KICKOFF
+    ;; == Low address ==
+    ;; };
+
+    ;; Return to kickoff
+    ret
+
 
 ; COROUTINE_SWITCH : Coroutinenumschaltung. Der aktuelle Registersatz wird
 ;                    gesichert und der Registersatz der neuen Coroutine
 ;                    wird in den Prozessor eingelesen.
 ;
-; C Prototyp: void Coroutine_switch (struct CoroutineState* regs_now,
-;                                    struct CoroutineState* reg_then);
+; C Prototyp: void Coroutine_switch (struct CoroutineState* regs_now, struct CoroutineState* reg_then);
 ;
 ; Achtung: Die Parameter werden von rechts nach links uebergeben.
 ;
+;; == High address ==
+;;        *REGS_THEN
+;;        *REGS_NOW
+;; SP --> RET ADDR
+;; == Low address ==
 Coroutine_switch:
-
 ; *
 ; * Hier muss Code eingefuegt werden
 ; *
 
+    ;; Make eax point to beginning of regs_now in memory
+    mov eax, [esp + 0x4]
+
+    ;; Save current coroutine registers
+    mov [eax + ebx_offset], ebx
+    mov [eax + esi_offset], esi
+    mov [eax + edi_offset], edi
+    mov [eax + ebp_offset], ebp
+    mov [eax + esp_offset], esp
+
+    ;; Make eax point to beginning of regs_then in memory
+    mov eax, [esp + 0x8]
+
+    ;; Load next coroutine registers
+    mov ebx, [eax + ebx_offset]
+    mov esi, [eax + esi_offset]
+    mov edi, [eax + edi_offset]
+    mov ebp, [eax + ebp_offset]
+    mov esp, [eax + esp_offset]
+
+    ;; Stackpointer now points to kickoff address, ret jumps there
+    ;; NOTE: The stackpointer only points to kickoff if the next coroutine was just initialized.
+    ;;       Otherwise it just points somewhere in the next coroutines stack
+    ret