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 <[email protected]>
   6  * for Pengutronix
   7  */
   8 #include <linux/export.h>
   9 #include <linux/ftrace.h>
  10 #include <linux/sched.h>
  11
  12 #include <asm/stacktrace.h>
  13
  14 struct return_address_data {
  15         unsigned int level;
  16         void *addr;
  17 };
  18
  19 static bool save_return_addr(void *d, unsigned long pc)
  20 {
  21         struct return_address_data *data = d;
  22
  23         if (!data->level) {
  24                 data->addr = (void *)pc;
  25
  26                 return false;
  27         } else {
  28                 --data->level;
  29                 return true;
  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.sp = current_stack_pointer;
  43         frame.lr = (unsigned long)__builtin_return_address(0);
  44 here:
  45         frame.pc = (unsigned long)&&here;
  46 #ifdef CONFIG_KRETPROBES
  47         frame.kr_cur = NULL;
  48         frame.tsk = current;
  49 #endif
  50         frame.ex_frame = false;
  51
  52         walk_stackframe(&frame, save_return_addr, &data);
  53
  54         if (!data.level)
  55                 return data.addr;
  56         else
  57                 return NULL;
  58 }
  59
  60 EXPORT_SYMBOL_GPL(return_address);