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 15 #include <asm/stacktrace.h> 16 17 struct return_address_data { 18 unsigned int level; 19 void *addr; 20 }; 21 22 static int save_return_addr(struct stackframe *frame, void *d) 23 { 24 struct return_address_data *data = d; 25 26 if (!data->level) { 27 data->addr = (void *)frame->pc; 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.pc = (unsigned long)return_address; /* dummy */ 46 47 walk_stackframe(&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); 55