core/syscall.c

@@ -0,0 +1,27 @@
+#include "klibc.h"
+#include "stdarg.h"
+#include "syscall.h"
+#include "thread.h"
+
+int syscallExecute(int syscallId, const struct cpu_state *user_ctx){
+
+    int ret;
+
+    switch (syscallId) {
+        case SYSCALL_ID_EXIT:
+            uint status;
+            ret = syscallGet1arg(user_ctx, &status);
+            if(ret != 0)
+                break;
+            threadExit();
+            assert(0);
+            break;
+        case SYSCALL_ID_WRITE:
+            ret = printf("YOLO FROM USERSPACE\n");
+            break;
+        default:
+           printf("Unknon syscall id %d\n", syscallId); 
+           ret = -ENOENT;
+    }
+    return ret;
+}

core/syscall.h

@@ -0,0 +1,9 @@
+#pragma once
+
+#include "cpu_context.h" 
+
+
+#define SYSCALL_ID_EXIT 1
+#define SYSCALL_ID_WRITE 2
+
+int syscallExecute(int syscallId, const struct cpu_state *user_ctx);

core/thread.c

@@ -132,10 +132,13 @@ struct cpu_state *threadSwitch(struct cpu_state *prevCpu)
     disable_IRQs(flags);
 
     nextThread              = threadSelectNext();
-    currentThread->cpuState = prevCpu;
+    if (nextThread != currentThread) {
-    currentThread->state    = READY;
+        currentThread->cpuState = prevCpu;
-    currentThread           = nextThread;
+        currentThread->state    = READY;
-    currentThread->state    = RUNNING;
+        currentThread           = nextThread;
+        currentThread->state    = RUNNING;
+        threadPrepareContext(nextThread);
+    }
 
     restore_IRQs(flags);