| 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/module.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->lr; |
| 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 + 1; |
| 45 | |
| 46 | frame.fp = (unsigned long)__builtin_frame_address(0); |
| 47 | frame.sp = current_sp; |
| 48 | frame.lr = (unsigned long)__builtin_return_address(0); |
| 49 | frame.pc = (unsigned long)return_address; |
| 50 | |
| 51 | walk_stackframe(&frame, save_return_addr, &data); |
| 52 | |
| 53 | if (!data.level) |
| 54 | return data.addr; |
| 55 | else |
| 56 | return NULL; |
| 57 | } |
| 58 | |
| 59 | #else /* if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND) */ |
| 60 | |
| 61 | #if defined(CONFIG_ARM_UNWIND) |
| 62 | #warning "TODO: return_address should use unwind tables" |
| 63 | #endif |
| 64 | |
| 65 | void *return_address(unsigned int level) |
| 66 | { |
| 67 | return NULL; |
| 68 | } |
| 69 | |
| 70 | #endif /* if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND) / else */ |
| 71 | |
| 72 | EXPORT_SYMBOL_GPL(return_address); |