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
  12 #include <asm/stack_pointer.h>
  13 #include <asm/stacktrace.h>
  14
  15 struct return_address_data {
  16         unsigned int level;
  17         void *addr;
  18 };
  19
  20 static int save_return_addr(struct stackframe *frame, void *d)
  21 {
  22         struct return_address_data *data = d;
  23
  24         if (!data->level) {
  25                 data->addr = (void *)frame->pc;
  26                 return 1;
  27         } else {
  28                 --data->level;
  29                 return 0;
  30         }
  31 }
  32
  33 void *return_address(unsigned int level)
  34 {
  35         struct return_address_data data;
  36         struct stackframe frame;
  37
  38         data.level = level + 2;
  39         data.addr = NULL;
  40
  41         frame.fp = (unsigned long)__builtin_frame_address(0);
  42         frame.pc = (unsigned long)return_address; /* dummy */
  43 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
  44         frame.graph = 0;
  45 #endif
  46
  47         walk_stackframe(current, &frame, save_return_addr, &data);
  48
  49         if (!data.level)
  50                 return data.addr;
  51         else
  52                 return NULL;
  53 }
  54 EXPORT_SYMBOL_GPL(return_address);