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/stack_pointer.h> 16 #include <asm/stacktrace.h> 17 18 struct return_address_data { 19 unsigned int level; 20 void *addr; 21 }; 22 23 static int save_return_addr(struct stackframe *frame, void *d) 24 { 25 struct return_address_data *data = d; 26 27 if (!data->level) { 28 data->addr = (void *)frame->pc; 29 return 1; 30 } else { 31 --data->level; 32 return 0; 33 } 34 } 35 36 void *return_address(unsigned int level) 37 { 38 struct return_address_data data; 39 struct stackframe frame; 40 41 data.level = level + 2; 42 data.addr = NULL; 43 44 frame.fp = (unsigned long)__builtin_frame_address(0); 45 frame.pc = (unsigned long)return_address; /* dummy */ 46 #ifdef CONFIG_FUNCTION_GRAPH_TRACER 47 frame.graph = current->curr_ret_stack; 48 #endif 49 50 walk_stackframe(current, &frame, save_return_addr, &data); 51 52 if (!data.level) 53 return data.addr; 54 else 55 return NULL; 56 } 57 EXPORT_SYMBOL_GPL(return_address); 58