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/export.h>
  12 #include <linux/ftrace.h>
  13
  14 #if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND)
  15 #include <linux/sched.h>
  16
  17 #include <asm/stacktrace.h>
  18
  19 struct return_address_data {
  20         unsigned int level;
  21         void *addr;
  22 };
  23
  24 static int save_return_addr(struct stackframe *frame, void *d)
  25 {
  26         struct return_address_data *data = d;
  27
  28         if (!data->level) {
  29                 data->addr = (void *)frame->pc;
  30
  31                 return 1;
  32         } else {
  33                 --data->level;
  34                 return 0;
  35         }
  36 }
  37
  38 void *return_address(unsigned int level)
  39 {
  40         struct return_address_data data;
  41         struct stackframe frame;
  42
  43         data.level = level + 2;
  44         data.addr = NULL;
  45
  46         frame.fp = (unsigned long)__builtin_frame_address(0);
  47         frame.sp = current_stack_pointer;
  48         frame.lr = (unsigned long)__builtin_return_address(0);
  49         frame.pc = (unsigned long)return_address;
  50
  51         walk_stackframe(&frame, save_return_addr, &data);
  52
  53         if (!data.level)
  54                 return data.addr;
  55         else
  56                 return NULL;
  57 }
  58
  59 #endif /* if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND) */
  60
  61 EXPORT_SYMBOL_GPL(return_address);