1. 根目录:
2. arch
3. arm
4. kernel
5. return_address.c

/*
 * arch/arm/kernel/return_address.c
 *
 * Copyright (C) 2009 Uwe Kleine-Koenig <u.kleine-koenig@pengutronix.de>
 * for Pengutronix
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 */
#include <linux/export.h>
#include <linux/ftrace.h>

#if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND)
#include <linux/sched.h>

#include <asm/stacktrace.h>

struct return_address_data {
	unsigned int level;
	void *addr;
};

static int save_return_addr(struct stackframe *frame, void *d)
{
	struct return_address_data *data = d;

	if (!data->level) {
		data->addr = (void *)frame->pc;

		return 1;
	} else {
		--data->level;
		return 0;
	}
}

void *return_address(unsigned int level)
{
	struct return_address_data data;
	struct stackframe frame;
	register unsigned long current_sp asm ("sp");

	data.level = level + 2;
	data.addr = NULL;

	frame.fp = (unsigned long)__builtin_frame_address(0);
	frame.sp = current_sp;
	frame.lr = (unsigned long)__builtin_return_address(0);
	frame.pc = (unsigned long)return_address;

	walk_stackframe(&frame, save_return_addr, &data);

	if (!data.level)
		return data.addr;
	else
		return NULL;
}

#else /* if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND) */

#if defined(CONFIG_ARM_UNWIND)
#warning "TODO: return_address should use unwind tables"
#endif

void *return_address(unsigned int level)
{
	return NULL;
}

#endif /* if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND) / else */

EXPORT_SYMBOL_GPL(return_address);