/*
 * arch/arm/kernel/unwind.c
 *
 * Copyright (C) 2008 ARM Limited
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 *
 * Stack unwinding support for ARM
 *
 * An ARM EABI version of gcc is required to generate the unwind
 * tables. For information about the structure of the unwind tables,
 * see "Exception Handling ABI for the ARM Architecture" at:
 *
 * http://infocenter.arm.com/help/topic/com.arm.doc.subset.swdev.abi/index.html
 */

#ifndef __CHECKER__
#if !defined (__ARM_EABI__)
#warning Your compiler does not have EABI support.
#warning    ARM unwind is known to compile only with EABI compilers.
#warning    Change compiler or disable ARM_UNWIND option.
#elif (__GNUC__ == 4 && __GNUC_MINOR__ <= 2)
#warning Your compiler is too buggy; it is known to not compile ARM unwind support.
#warning    Change compiler or disable ARM_UNWIND option.
#endif
#endif /* __CHECKER__ */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/export.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/list.h>

#include <asm/stacktrace.h>
#include <asm/traps.h>
#include <asm/unwind.h>

/* Dummy functions to avoid linker complaints */
void __aeabi_unwind_cpp_pr0(void)
{
};
EXPORT_SYMBOL(__aeabi_unwind_cpp_pr0);

void __aeabi_unwind_cpp_pr1(void)
{
};
EXPORT_SYMBOL(__aeabi_unwind_cpp_pr1);

void __aeabi_unwind_cpp_pr2(void)
{
};
EXPORT_SYMBOL(__aeabi_unwind_cpp_pr2);

struct unwind_ctrl_block {
	unsigned long vrs[16];		/* virtual register set */
	const unsigned long *insn;	/* pointer to the current instructions word */
	int entries;			/* number of entries left to interpret */
	int byte;			/* current byte number in the instructions word */
};

enum regs {
#ifdef CONFIG_THUMB2_KERNEL
	FP = 7,
#else
	FP = 11,
#endif
	SP = 13,
	LR = 14,
	PC = 15
};

extern const struct unwind_idx __start_unwind_idx[];
static const struct unwind_idx *__origin_unwind_idx;
extern const struct unwind_idx __stop_unwind_idx[];

static DEFINE_SPINLOCK(unwind_lock);
static LIST_HEAD(unwind_tables);

/* Convert a prel31 symbol to an absolute address */
#define prel31_to_addr(ptr)				\
({							\
	/* sign-extend to 32 bits */			\
	long offset = (((long)*(ptr)) << 1) >> 1;	\
	(unsigned long)(ptr) + offset;			\
})

/*
 * Binary search in the unwind index. The entries are
 * guaranteed to be sorted in ascending order by the linker.
 *
 * start = first entry
 * origin = first entry with positive offset (or stop if there is no such entry)
 * stop - 1 = last entry
 */
static const struct unwind_idx *search_index(unsigned long addr,
				       const struct unwind_idx *start,
				       const struct unwind_idx *origin,
				       const struct unwind_idx *stop)
{
	unsigned long addr_prel31;

	pr_debug("%s(%08lx, %p, %p, %p)\n",
			__func__, addr, start, origin, stop);

	/*
	 * only search in the section with the matching sign. This way the
	 * prel31 numbers can be compared as unsigned longs.
	 */
	if (addr < (unsigned long)start)
		/* negative offsets: [start; origin) */
		stop = origin;
	else
		/* positive offsets: [origin; stop) */
		start = origin;

	/* prel31 for address relavive to start */
	addr_prel31 = (addr - (unsigned long)start) & 0x7fffffff;

	while (start < stop - 1) {
		const struct unwind_idx *mid = start + ((stop - start) >> 1);

		/*
		 * As addr_prel31 is relative to start an offset is needed to
		 * make it relative to mid.
		 */
		if (addr_prel31 - ((unsigned long)mid - (unsigned long)start) <
				mid->addr_offset)
			stop = mid;
		else {
			/* keep addr_prel31 relative to start */
			addr_prel31 -= ((unsigned long)mid -
					(unsigned long)start);
			start = mid;
		}
	}