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 #include <linux/kprobes.h>
  15
  16 #include <asm/stack_pointer.h>
  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                 return 1;
  31         } else {
  32                 --data->level;
  33                 return 0;
  34         }
  35 }
  36 NOKPROBE_SYMBOL(save_return_addr);
  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.pc = (unsigned long)return_address; /* dummy */
  48 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
  49         frame.graph = current->curr_ret_stack;
  50 #endif
  51
  52         walk_stackframe(current, &frame, save_return_addr, &data);
  53
  54         if (!data.level)
  55                 return data.addr;
  56         else
  57                 return NULL;
  58 }
  59 EXPORT_SYMBOL_GPL(return_address);
  60 NOKPROBE_SYMBOL(return_address);