release/src-rt-6.x.4708/linux/linux-2.6.36/arch/arm/kernel/return_address.c

   1 /*
   2  * arch/arm/kernel/return_address.c
   3  *
   4  * Copyright (C) 2009 Uwe Kleine-Koenig <u.kleine-koenig@pengutronix.de>
   5  * for Pengutronix
   6  *
   7  * This program is free software; you can redistribute it and/or modify it
   8  * under the terms of the GNU General Public License version 2 as published by
   9  * the Free Software Foundation.
  10  */
  11 #include <linux/module.h>
  12
  13 #if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND)
  14 #include <linux/sched.h>
  15
  16 #include <asm/stacktrace.h>
  17
  18 struct return_address_data {
  19         unsigned int level;
  20         void *addr;
  21 };
  22
  23 static int save_return_addr(struct stackframe *frame, void *d)
  24 {
  25         struct return_address_data *data = d;
  26
  27         if (!data->level) {
  28                 data->addr = (void *)frame->lr;
  29
  30                 return 1;
  31         } else {
  32                 --data->level;
  33                 return 0;
  34         }
  35 }
  36
  37 void *return_address(unsigned int level)
  38 {
  39         struct return_address_data data;
  40         struct stackframe frame;
  41         register unsigned long current_sp asm ("sp");
  42
  43         data.level = level + 1;
  44
  45         frame.fp = (unsigned long)__builtin_frame_address(0);
  46         frame.sp = current_sp;
  47         frame.lr = (unsigned long)__builtin_return_address(0);
  48         frame.pc = (unsigned long)return_address;
  49
  50         walk_stackframe(&frame, save_return_addr, &data);
  51
  52         if (!data.level)
  53                 return data.addr;
  54         else
  55                 return NULL;
  56 }
  57
  58 #else /* if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND) */
  59
  60 #if defined(CONFIG_ARM_UNWIND)
  61 #warning "TODO: return_address should use unwind tables"
  62 #endif
  63
  64 void *return_address(unsigned int level)
  65 {
  66         return NULL;
  67 }
  68
  69 #endif /* if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND) / else */
  70
  71 EXPORT_SYMBOL_GPL(return_address);