arch/arm/kernel/return_address.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * arch/arm/kernel/return_address.c
   4  *
   5  * Copyright (C) 2009 Uwe Kleine-Koenig <u.kleine-koenig@pengutronix.de>
   6  * for Pengutronix
   7  */
   8 #include <linux/export.h>
   9 #include <linux/ftrace.h>
  10
  11 #if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND)
  12 #include <linux/sched.h>
  13
  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
  28                 return 1;
  29         } else {
  30                 --data->level;
  31                 return 0;
  32         }
  33 }
  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         frame.fp = (unsigned long)__builtin_frame_address(0);
  44         frame.sp = current_stack_pointer;
  45         frame.lr = (unsigned long)__builtin_return_address(0);
  46         frame.pc = (unsigned long)return_address;
  47
  48         walk_stackframe(&frame, save_return_addr, &data);
  49
  50         if (!data.level)
  51                 return data.addr;
  52         else
  53                 return NULL;
  54 }
  55
  56 #endif /* if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND) */
  57
  58 EXPORT_SYMBOL_GPL(return_address);