4 files changed, 27 insertions, 11 deletions
diff --git a/asm/syscall.h b/asm/syscall.h
new file mode 100644
index 0000000..2cadce4
--- /dev/null
+++ b/asm/syscall.h
@@ -0,0 +1,11 @@
+/* 
+ * Issue a System Call from Ring 3 / User Space 
+ *
+ * Accepts up to 3 parameters.
+ * Check syscalls.h for details.
+ */
+
+uint32_t syscall(uint32_t code,
+                 uint32_t param_1, 
+                 uint32_t param_2, 
+                 uint32_t param_3);
diff --git a/asm/syscall.s b/asm/syscall.s
index 8860d89..388b6fa 100644
--- a/asm/syscall.s
+++ b/asm/syscall.s
@@ -1,10 +1,5 @@
 .global syscall
 
-// call from c with 4 x 32bit params
-// syscall number, p1,p2,p3,p4
-
-// TODO: push stack frame?
-
 syscall:
 
 	push %ebx // preserve (sysV abi convnetion)
diff --git a/asm/usermode.h b/asm/usermode.h
new file mode 100644
index 0000000..9b76db3
--- /dev/null
+++ b/asm/usermode.h
@@ -0,0 +1,7 @@
+/*
+ * Switch to User Mode and returin to function given by pointer
+ * provide the address of a void func() that will be called without
+ * any params.
+ */
+
+void usermode(uint32_t func);
diff --git a/asm/usermode.s b/asm/usermode.s
index acf4b04..67eca04 100644
--- a/asm/usermode.s
+++ b/asm/usermode.s
@@ -1,8 +1,9 @@
-.global asm_usermode
-.extern userfunc
+.global usermode
 
-# pass address to func to exec (TODO)
-asm_usermode:
+usermode:
+
+	mov 0x4(%esp),%edx    //get adress of passed : void func()
+			      //to be called in ring 3
 
 	// 0x23 is user data segment (|2 low bits)
 	// 0x1b is user code segment (|2 low bits)
@@ -13,6 +14,7 @@ asm_usermode:
         mov %ax, %es
         mov %ax, %fs
         mov %ax, %gs
+
 	// ss is handled by iret
                  
         mov %esp, %eax
@@ -25,10 +27,11 @@ asm_usermode:
         //mov $0x200, %eax
 	//push %eax	    // eflags image
         pushl $0x1B	    // return code segment selector
-        push $userfunc	    // return instruction pointer
+        push %edx	   // return instruction pointer
+
         iret
 
-	jmp . // will never be reached?
+	jmp . // never to be reached