arch/sh/kernel/return_address.c

   1 /*
   2  * arch/sh/kernel/return_address.c
   3  *
   4  * Copyright (C) 2009  Matt Fleming
   5  * Copyright (C) 2009  Paul Mundt
   6  *
   7  * This file is subject to the terms and conditions of the GNU General Public
   8  * License.  See the file "COPYING" in the main directory of this archive
   9  * for more details.
  10  */
  11 #include <linux/kernel.h>
  12 #include <linux/module.h>
  13 #include <asm/dwarf.h>
  14
  15 #ifdef CONFIG_DWARF_UNWINDER
  16
  17 void *return_address(unsigned int depth)
  18 {
  19         struct dwarf_frame *frame;
  20         unsigned long ra;
  21         int i;
  22
  23         for (i = 0, frame = NULL, ra = 0; i <= depth; i++) {
  24                 struct dwarf_frame *tmp;
  25
  26                 tmp = dwarf_unwind_stack(ra, frame);
  27                 if (!tmp)
  28                         return NULL;
  29
  30                 if (frame)
  31                         dwarf_free_frame(frame);
  32
  33                 frame = tmp;
  34
  35                 if (!frame || !frame->return_addr)
  36                         break;
  37
  38                 ra = frame->return_addr;
  39         }
  40
  41         /* Failed to unwind the stack to the specified depth. */
  42         WARN_ON(i != depth + 1);
  43
  44         if (frame)
  45                 dwarf_free_frame(frame);
  46
  47         return (void *)ra;
  48 }
  49
  50 #else
  51
  52 void *return_address(unsigned int depth)
  53 {
  54         return NULL;
  55 }
  56
  57 #endif
  58
  59 EXPORT_SYMBOL_GPL(return_address);