syscalls: add chdir and getcwd syscalls, not tested yet

src/tasking/syscalls.c

@@ -230,6 +230,22 @@ int sys_close(TrapFrame *tf)
     return -1;
 }
 
+int sys_chdir(TrapFrame *tf)
+{
+    return fat_opendir(current->cwd, (const char*)tf->ebx);
+}
+
+int sys_getcwd(TrapFrame *tf)
+{
+    int len = tf->ecx;
+
+    if(len >= 260)
+        return (int)NULL;
+
+    memcpy((void*)tf->ebx, current->cwd->fat->name, current->cwd->fat->namelen);
+    return tf->ebx;
+}
+
 int sys_getpid(TrapFrame *tf)
 {
     return current->pid;
@@ -268,9 +284,18 @@ void handle_syscall(TrapFrame *tf)
             tf->eax = sys_close(tf);
             break;
         
+        case 12://chdir
+            tf->eax = sys_chdir(tf);
+            break;
+        
         case 20://getpid
             tf->eax = sys_getpid(tf);
             break;
+        
+        case 183://getcwd
+            tf->eax = sys_getcwd(tf);
+            break;
+
         default:
             debug_log("unknown syscall: %X\n", tf->eax);
             tf->eax = -1;