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         register unsigned long current_sp asm ("sp");
  43
  44         data.level = level + 2;
  45         data.addr = NULL;
  46
  47         frame.fp = (unsigned long)__builtin_frame_address(0);
  48         frame.sp = current_sp;
  49         frame.lr = (unsigned long)__builtin_return_address(0);
  50         frame.pc = (unsigned long)return_address;
  51
  52         walk_stackframe(&frame, save_return_addr, &data);
  53
  54         if (!data.level)
  55                 return data.addr;
  56         else
  57                 return NULL;
  58 }
  59
  60 #else /* if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND) */
  61
  62 #if defined(CONFIG_ARM_UNWIND)
  63 #warning "TODO: return_address should use unwind tables"
  64 #endif
  65
  66 void *return_address(unsigned int level)
  67 {
  68         return NULL;
  69 }
  70
  71 #endif /* if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND) / else */
  72
  73 EXPORT_SYMBOL_GPL(return_address);