arch/arm64/kernel/return_address.c

   1 /*
   2  * arch/arm64/kernel/return_address.c
   3  *
   4  * Copyright (C) 2013 Linaro Limited
   5  * Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11
  12 #include <linux/export.h>
  13 #include <linux/ftrace.h>
  14
  15 #include <asm/stack_pointer.h>
  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->pc;
  29                 return 1;
  30         } else {
  31                 --data->level;
  32                 return 0;
  33         }
  34 }
  35
  36 void *return_address(unsigned int level)
  37 {
  38         struct return_address_data data;
  39         struct stackframe frame;
  40
  41         data.level = level + 2;
  42         data.addr = NULL;
  43
  44         frame.fp = (unsigned long)__builtin_frame_address(0);
  45         frame.pc = (unsigned long)return_address; /* dummy */
  46 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
  47         frame.graph = 0;
  48 #endif
  49
  50         walk_stackframe(current, &frame, save_return_addr, &data);
  51
  52         if (!data.level)
  53                 return data.addr;
  54         else
  55                 return NULL;
  56 }
  57 EXPORT_SYMBOL_GPL(return_address);