src/frame.c

   1 /*
   2  * Copyright (C) 2003, 2004, 2005, 2006, 2007
   3  * Robert Lougher <rob@lougher.org.uk>.
   4  *
   5  * This file is part of JamVM.
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License
   9  * as published by the Free Software Foundation; either version 2,
  10  * or (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  20  */
  21
  22 #include <stddef.h>
  23 #include "jam.h"
  24
  25 /* The function getCallerFrame() is used in the code that does
  26    security related stack-walking.  It guards against invocation
  27    via reflection.  These frames must be skipped, else it will
  28    appear that the caller was loaded by the boot loader. */
  29
  30 Frame *getCallerFrame(Frame *last) {
  31
  32 loop:
  33     /* Skip the top frame, and check if the
  34        previous is a dummy frame */
  35     if((last = last->prev)->mb == NULL) {
  36
  37         /* Skip the dummy frame, and check if
  38          * we're at the top of the stack */
  39         if((last = last->prev)->prev == NULL)
  40             return NULL;
  41
  42         /* Check if we were invoked via reflection */
  43         if(last->mb->class == getReflectMethodClass()) {
  44
  45             /* There will be two frames for invoke.  Skip
  46                the first, and jump back.  This also handles
  47                recursive invocation via reflection. */
  48
  49             last = last->prev;
  50             goto loop;
  51         }
  52     }
  53     return last;
  54 }
  55
  56 Class *getCallerCallerClass() {
  57     Frame *last = getExecEnv()->last_frame->prev;
  58
  59     if((last->mb == NULL && (last = last->prev)->prev == NULL) ||
  60              (last = getCallerFrame(last)) == NULL)
  61         return NULL;
  62
  63     return last->mb->class;
  64 }
  65