arch/arm64/kernel/return_address.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * arch/arm64/kernel/return_address.c
   4  *
   5  * Copyright (C) 2013 Linaro Limited
   6  * Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
   7  */
   8
   9 #include <linux/export.h>
  10 #include <linux/ftrace.h>
  11 #include <linux/kprobes.h>
  12
  13 #include <asm/stack_pointer.h>
  14 #include <asm/stacktrace.h>
  15
  16 struct return_address_data {
  17         unsigned int level;
  18         void *addr;
  19 };
  20
  21 static int save_return_addr(struct stackframe *frame, void *d)
  22 {
  23         struct return_address_data *data = d;
  24
  25         if (!data->level) {
  26                 data->addr = (void *)frame->pc;
  27                 return 1;
  28         } else {
  29                 --data->level;
  30                 return 0;
  31         }
  32 }
  33 NOKPROBE_SYMBOL(save_return_addr);
  34
  35 void *return_address(unsigned int level)
  36 {
  37         struct return_address_data data;
  38         struct stackframe frame;
  39
  40         data.level = level + 2;
  41         data.addr = NULL;
  42
  43         start_backtrace(&frame,
  44                         (unsigned long)__builtin_frame_address(0),
  45                         (unsigned long)return_address);
  46         walk_stackframe(current, &frame, save_return_addr, &data);
  47
  48         if (!data.level)
  49                 return data.addr;
  50         else
  51                 return NULL;
  52 }
  53 EXPORT_SYMBOL_GPL(return_address);
  54 NOKPROBE_SYMBOL(return_address);