1 /* 2 * arch/arm/kernel/return_address.c 3 * 4 * Copyright (C) 2009 Uwe Kleine-Koenig <u.kleine-koenig@pengutronix.de> 5 * for Pengutronix 6 * 7 * This program is free software; you can redistribute it and/or modify it 8 * under the terms of the GNU General Public License version 2 as published by 9 * the Free Software Foundation. 10 */ 11 #include <linux/export.h> 12 #include <linux/ftrace.h> 13 14 #if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND) 15 #include <linux/sched.h> 16 17 #include <asm/stacktrace.h> 18 19 struct return_address_data { 20 unsigned int level; 21 void *addr; 22 }; 23 24 static int save_return_addr(struct stackframe *frame, void *d) 25 { 26 struct return_address_data *data = d; 27 28 if (!data->level) { 29 data->addr = (void *)frame->pc; 30 31 return 1; 32 } else { 33 --data->level; 34 return 0; 35 } 36 } 37 38 void *return_address(unsigned int level) 39 { 40 struct return_address_data data; 41 struct stackframe frame; 42 register unsigned long current_sp asm ("sp"); 43 44 data.level = level + 2; 45 data.addr = NULL; 46 47 frame.fp = (unsigned long)__builtin_frame_address(0); 48 frame.sp = current_sp; 49 frame.lr = (unsigned long)__builtin_return_address(0); 50 frame.pc = (unsigned long)return_address; 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 #else /* if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND) */ 61 62 #if defined(CONFIG_ARM_UNWIND) 63 #warning "TODO: return_address should use unwind tables" 64 #endif 65 66 void *return_address(unsigned int level) 67 { 68 return NULL; 69 } 70 71 #endif /* if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND) / else */ 72 73 EXPORT_SYMBOL_GPL(return_address); 74