arch/parisc/kernel/unwind.c - LeafOS-Devices/android_kernel_samsung_exynos9820 - Gitiles

 /*
  * Kernel unwinding support
  *
  * (c) 2002-2004 Randolph Chung <tausq@debian.org>
  *
  * Derived partially from the IA64 implementation. The PA-RISC
  * Runtime Architecture Document is also a useful reference to
  * understand what is happening here
  */

 #include <linux/kernel.h>
 #include <linux/init.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/kallsyms.h>

 #include <asm/uaccess.h>
 #include <asm/assembly.h>

 #include <asm/unwind.h>

 /* #define DEBUG 1 */
 #ifdef DEBUG
 #define dbg(x...) printk(x)
 #else
 #define dbg(x...)
 #endif

 extern struct unwind_table_entry __start___unwind[];
 extern struct unwind_table_entry __stop___unwind[];

 static spinlock_t unwind_lock;
 /*
  * the kernel unwind block is not dynamically allocated so that
  * we can call unwind_init as early in the bootup process as
  * possible (before the slab allocator is initialized)
  */
 static struct unwind_table kernel_unwind_table __read_mostly;
 static LIST_HEAD(unwind_tables);

 static inline const struct unwind_table_entry *
 find_unwind_entry_in_table(const struct unwind_table *table, unsigned long addr)
 {
 	const struct unwind_table_entry *e = NULL;
 	unsigned long lo, hi, mid;

 	lo = 0;
 	hi = table->length - 1;

 	while (lo <= hi) {
 		mid = (hi - lo) / 2 + lo;
 		e = &table->table[mid];
 		if (addr < e->region_start)
 			hi = mid - 1;
 		else if (addr > e->region_end)
 			lo = mid + 1;
 		else
 			return e;
 	}

 	return NULL;
 }

 static const struct unwind_table_entry *
 find_unwind_entry(unsigned long addr)
 {
 	struct unwind_table *table;
 	const struct unwind_table_entry *e = NULL;

 	if (addr >= kernel_unwind_table.start &&
 	    addr <= kernel_unwind_table.end)
 		e = find_unwind_entry_in_table(&kernel_unwind_table, addr);
 	else
 		list_for_each_entry(table, &unwind_tables, list) {
 			if (addr >= table->start &&
 			    addr <= table->end)
 				e = find_unwind_entry_in_table(table, addr);
 			if (e)
 				break;
 		}

 	return e;
 }

 static void
 unwind_table_init(struct unwind_table *table, const char *name,
 		  unsigned long base_addr, unsigned long gp,
 		  void *table_start, void *table_end)
 {
 	struct unwind_table_entry *start = table_start;
 	struct unwind_table_entry *end =
 		(struct unwind_table_entry *)table_end - 1;

 	table->name = name;
 	table->base_addr = base_addr;
 	table->gp = gp;
 	table->start = base_addr + start->region_start;
 	table->end = base_addr + end->region_end;
 	table->table = (struct unwind_table_entry *)table_start;
 	table->length = end - start + 1;
 	INIT_LIST_HEAD(&table->list);

 	for (; start <= end; start++) {
 		if (start < end &&
 		    start->region_end > (start+1)->region_start) {
 			printk("WARNING: Out of order unwind entry! %p and %p\n", start, start+1);
 		}

 		start->region_start += base_addr;
 		start->region_end += base_addr;
 	}
 }

 static void
 unwind_table_sort(struct unwind_table_entry *start,
 		  struct unwind_table_entry *finish)
 {
 	struct unwind_table_entry el, *p, *q;

 	for (p = start + 1; p < finish; ++p) {
 		if (p[0].region_start < p[-1].region_start) {
 			el = *p;
 			q = p;
 			do {
 				q[0] = q[-1];
 				--q;
 			} while (q > start &&
 				 el.region_start < q[-1].region_start);
 			*q = el;
 		}
 	}
 }

 struct unwind_table *
 unwind_table_add(const char *name, unsigned long base_addr,
 		 unsigned long gp,
                  void *start, void *end)
 {
 	struct unwind_table *table;
 	unsigned long flags;
 	struct unwind_table_entry *s = (struct unwind_table_entry *)start;
 	struct unwind_table_entry *e = (struct unwind_table_entry *)end;

 	unwind_table_sort(s, e);

 	table = kmalloc(sizeof(struct unwind_table), GFP_USER);
 	if (table == NULL)
 		return NULL;
 	unwind_table_init(table, name, base_addr, gp, start, end);
 	spin_lock_irqsave(&unwind_lock, flags);
 	list_add_tail(&table->list, &unwind_tables);
 	spin_unlock_irqrestore(&unwind_lock, flags);

 	return table;
 }

 void unwind_table_remove(struct unwind_table *table)
 {
 	unsigned long flags;

 	spin_lock_irqsave(&unwind_lock, flags);
 	list_del(&table->list);
 	spin_unlock_irqrestore(&unwind_lock, flags);

 	kfree(table);
 }

 /* Called from setup_arch to import the kernel unwind info */
 static int unwind_init(void)
 {
 	long start, stop;
 	register unsigned long gp __asm__ ("r27");

 	start = (long)&__start___unwind[0];
 	stop = (long)&__stop___unwind[0];

 	spin_lock_init(&unwind_lock);

 	printk("unwind_init: start = 0x%lx, end = 0x%lx, entries = %lu\n",
 	    start, stop,
 	    (stop - start) / sizeof(struct unwind_table_entry));

 	unwind_table_init(&kernel_unwind_table, "kernel", KERNEL_START,
 			  gp,
 			  &__start___unwind[0], &__stop___unwind[0]);
 #if 0
 	{
 		int i;
 		for (i = 0; i < 10; i++)
 		{
 			printk("region 0x%x-0x%x\n",
 				__start___unwind[i].region_start,
 				__start___unwind[i].region_end);
 		}
 	}
 #endif
 	return 0;
 }

 static void unwind_frame_regs(struct unwind_frame_info *info)
 {
 	const struct unwind_table_entry *e;
 	unsigned long npc;
 	unsigned int insn;
 	long frame_size = 0;
 	int looking_for_rp, rpoffset = 0;

 	e = find_unwind_entry(info->ip);
 	if (e == NULL) {
 		unsigned long sp;
 		extern char _stext[], _etext[];

 		dbg("Cannot find unwind entry for 0x%lx; forced unwinding\n", info->ip);

 #ifdef CONFIG_KALLSYMS
 		/* Handle some frequent special cases.... */
 		{
 			char symname[KSYM_NAME_LEN+1];
 			char *modname;

 			kallsyms_lookup(info->ip, NULL, NULL, &modname,
 				symname);

 			dbg("info->ip = 0x%lx, name = %s\n", info->ip, symname);

 			if (strcmp(symname, "_switch_to_ret") == 0) {
 				info->prev_sp = info->sp - CALLEE_SAVE_FRAME_SIZE;
 				info->prev_ip = *(unsigned long *)(info->prev_sp - RP_OFFSET);
 				dbg("_switch_to_ret @ %lx - setting "
 				    "prev_sp=%lx prev_ip=%lx\n",
 				    info->ip, info->prev_sp,
 				    info->prev_ip);
 				return;
 			} else if (strcmp(symname, "ret_from_kernel_thread") == 0 ||
 				   strcmp(symname, "syscall_exit") == 0) {
 				info->prev_ip = info->prev_sp = 0;
 				return;
 			}
 		}
 #endif

 		/* Since we are doing the unwinding blind, we don't know if
 		   we are adjusting the stack correctly or extracting the rp
 		   correctly. The rp is checked to see if it belongs to the
 		   kernel text section, if not we assume we don't have a
 		   correct stack frame and we continue to unwind the stack.
 		   This is not quite correct, and will fail for loadable
 		   modules. */
 		sp = info->sp & ~63;
 		do {
 			unsigned long tmp;

 			info->prev_sp = sp - 64;
 			info->prev_ip = 0;
 			if (get_user(tmp, (unsigned long *)(info->prev_sp - RP_OFFSET)))
 				break;
 			info->prev_ip = tmp;
 			sp = info->prev_sp;
 		} while (info->prev_ip < (unsigned long)_stext ||
 			 info->prev_ip > (unsigned long)_etext);

 		info->rp = 0;

 		dbg("analyzing func @ %lx with no unwind info, setting "
 		    "prev_sp=%lx prev_ip=%lx\n", info->ip,
 		    info->prev_sp, info->prev_ip);
 	} else {
 		dbg("e->start = 0x%x, e->end = 0x%x, Save_SP = %d, "
 		    "Save_RP = %d, Millicode = %d size = %u\n",
 		    e->region_start, e->region_end, e->Save_SP, e->Save_RP,
 		    e->Millicode, e->Total_frame_size);

 		looking_for_rp = e->Save_RP;

 		for (npc = e->region_start;
 		     (frame_size < (e->Total_frame_size << 3) ||
 		      looking_for_rp) &&
 		     npc < info->ip;
 		     npc += 4) {

 			insn = *(unsigned int *)npc;

 			if ((insn & 0xffffc000) == 0x37de0000 ||
 			    (insn & 0xffe00000) == 0x6fc00000) {
 				/* ldo X(sp), sp, or stwm X,D(sp) */
 				frame_size += (insn & 0x1 ? -1 << 13 : 0) |
 					((insn & 0x3fff) >> 1);
 				dbg("analyzing func @ %lx, insn=%08x @ "
 				    "%lx, frame_size = %ld\n", info->ip,
 				    insn, npc, frame_size);
 			} else if ((insn & 0xffe00008) == 0x73c00008) {
 				/* std,ma X,D(sp) */
 				frame_size += (insn & 0x1 ? -1 << 13 : 0) |
 					(((insn >> 4) & 0x3ff) << 3);
 				dbg("analyzing func @ %lx, insn=%08x @ "
 				    "%lx, frame_size = %ld\n", info->ip,
 				    insn, npc, frame_size);
 			} else if (insn == 0x6bc23fd9) {
 				/* stw rp,-20(sp) */
 				rpoffset = 20;
 				looking_for_rp = 0;
 				dbg("analyzing func @ %lx, insn=stw rp,"
 				    "-20(sp) @ %lx\n", info->ip, npc);
 			} else if (insn == 0x0fc212c1) {
 				/* std rp,-16(sr0,sp) */
 				rpoffset = 16;
 				looking_for_rp = 0;
 				dbg("analyzing func @ %lx, insn=std rp,"
 				    "-16(sp) @ %lx\n", info->ip, npc);
 			}
 		}

 		info->prev_sp = info->sp - frame_size;
 		if (e->Millicode)
 			info->rp = info->r31;
 		else if (rpoffset)
 			info->rp = *(unsigned long *)(info->prev_sp - rpoffset);
 		info->prev_ip = info->rp;
 		info->rp = 0;

 		dbg("analyzing func @ %lx, setting prev_sp=%lx "
 		    "prev_ip=%lx npc=%lx\n", info->ip, info->prev_sp,
 		    info->prev_ip, npc);
 	}
 }

 void unwind_frame_init(struct unwind_frame_info *info, struct task_struct *t,
 		       struct pt_regs *regs)
 {
 	memset(info, 0, sizeof(struct unwind_frame_info));
 	info->t = t;
 	info->sp = regs->gr[30];
 	info->ip = regs->iaoq[0];
 	info->rp = regs->gr[2];
 	info->r31 = regs->gr[31];

 	dbg("(%d) Start unwind from sp=%08lx ip=%08lx\n",
 	    t ? (int)t->pid : -1, info->sp, info->ip);
 }

 void unwind_frame_init_from_blocked_task(struct unwind_frame_info *info, struct task_struct *t)
 {
 	struct pt_regs *r = &t->thread.regs;
 	struct pt_regs *r2;

 	r2 = kmalloc(sizeof(struct pt_regs), GFP_KERNEL);
 	if (!r2)
 		return;
 	*r2 = *r;
 	r2->gr[30] = r->ksp;
 	r2->iaoq[0] = r->kpc;
 	unwind_frame_init(info, t, r2);
 	kfree(r2);
 }

 void unwind_frame_init_running(struct unwind_frame_info *info, struct pt_regs *regs)
 {
 	unwind_frame_init(info, current, regs);
 }

 int unwind_once(struct unwind_frame_info *next_frame)
 {
 	unwind_frame_regs(next_frame);

 	if (next_frame->prev_sp == 0 ||
 	    next_frame->prev_ip == 0)
 		return -1;

 	next_frame->sp = next_frame->prev_sp;
 	next_frame->ip = next_frame->prev_ip;
 	next_frame->prev_sp = 0;
 	next_frame->prev_ip = 0;

 	dbg("(%d) Continue unwind to sp=%08lx ip=%08lx\n",
 	    next_frame->t ? (int)next_frame->t->pid : -1,
 	    next_frame->sp, next_frame->ip);

 	return 0;
 }

 int unwind_to_user(struct unwind_frame_info *info)
 {
 	int ret;

 	do {
 		ret = unwind_once(info);
 	} while (!ret && !(info->ip & 3));

 	return ret;
 }

 module_init(unwind_init);
	/*
	* Kernel unwinding support
	*
	* (c) 2002-2004 Randolph Chung <tausq@debian.org>
	*
	* Derived partially from the IA64 implementation. The PA-RISC
	* Runtime Architecture Document is also a useful reference to
	* understand what is happening here
	*/

	#include <linux/kernel.h>
	#include <linux/init.h>
	#include <linux/sched.h>
	#include <linux/slab.h>
	#include <linux/kallsyms.h>

	#include <asm/uaccess.h>
	#include <asm/assembly.h>

	#include <asm/unwind.h>

	/* #define DEBUG 1 */
	#ifdef DEBUG
	#define dbg(x...) printk(x)
	#else
	#define dbg(x...)
	#endif

	extern struct unwind_table_entry __start___unwind[];
	extern struct unwind_table_entry __stop___unwind[];

	static spinlock_t unwind_lock;
	/*
	* the kernel unwind block is not dynamically allocated so that
	* we can call unwind_init as early in the bootup process as
	* possible (before the slab allocator is initialized)
	*/
	static struct unwind_table kernel_unwind_table __read_mostly;
	static LIST_HEAD(unwind_tables);

	static inline const struct unwind_table_entry *
	find_unwind_entry_in_table(const struct unwind_table *table, unsigned long addr)
	{
	const struct unwind_table_entry *e = NULL;
	unsigned long lo, hi, mid;

	lo = 0;
	hi = table->length - 1;

	while (lo <= hi) {
	mid = (hi - lo) / 2 + lo;
	e = &table->table[mid];
	if (addr < e->region_start)
	hi = mid - 1;
	else if (addr > e->region_end)
	lo = mid + 1;
	else
	return e;
	}

	return NULL;
	}

	static const struct unwind_table_entry *
	find_unwind_entry(unsigned long addr)
	{
	struct unwind_table *table;
	const struct unwind_table_entry *e = NULL;

	if (addr >= kernel_unwind_table.start &&
	addr <= kernel_unwind_table.end)
	e = find_unwind_entry_in_table(&kernel_unwind_table, addr);
	else
	list_for_each_entry(table, &unwind_tables, list) {
	if (addr >= table->start &&
	addr <= table->end)
	e = find_unwind_entry_in_table(table, addr);
	if (e)
	break;
	}

	return e;
	}

	static void
	unwind_table_init(struct unwind_table table, const char name,
	unsigned long base_addr, unsigned long gp,
	void table_start, void table_end)
	{
	struct unwind_table_entry *start = table_start;
	struct unwind_table_entry *end =
	(struct unwind_table_entry *)table_end - 1;

	table->name = name;
	table->base_addr = base_addr;
	table->gp = gp;
	table->start = base_addr + start->region_start;
	table->end = base_addr + end->region_end;
	table->table = (struct unwind_table_entry *)table_start;
	table->length = end - start + 1;
	INIT_LIST_HEAD(&table->list);

	for (; start <= end; start++) {
	if (start < end &&
	start->region_end > (start+1)->region_start) {
	printk("WARNING: Out of order unwind entry! %p and %p\n", start, start+1);
	}

	start->region_start += base_addr;
	start->region_end += base_addr;
	}
	}

	static void
	unwind_table_sort(struct unwind_table_entry *start,
	struct unwind_table_entry *finish)
	{
	struct unwind_table_entry el, p, q;

	for (p = start + 1; p < finish; ++p) {
	if (p[0].region_start < p[-1].region_start) {
	el = *p;
	q = p;
	do {
	q[0] = q[-1];
	--q;
	} while (q > start &&
	el.region_start < q[-1].region_start);
	*q = el;
	}
	}
	}

	struct unwind_table *
	unwind_table_add(const char *name, unsigned long base_addr,
	unsigned long gp,
	void start, void end)
	{
	struct unwind_table *table;
	unsigned long flags;
	struct unwind_table_entry s = (struct unwind_table_entry )start;
	struct unwind_table_entry e = (struct unwind_table_entry )end;

	unwind_table_sort(s, e);

	table = kmalloc(sizeof(struct unwind_table), GFP_USER);
	if (table == NULL)
	return NULL;
	unwind_table_init(table, name, base_addr, gp, start, end);
	spin_lock_irqsave(&unwind_lock, flags);
	list_add_tail(&table->list, &unwind_tables);
	spin_unlock_irqrestore(&unwind_lock, flags);

	return table;
	}

	void unwind_table_remove(struct unwind_table *table)
	{
	unsigned long flags;

	spin_lock_irqsave(&unwind_lock, flags);
	list_del(&table->list);
	spin_unlock_irqrestore(&unwind_lock, flags);

	kfree(table);
	}

	/* Called from setup_arch to import the kernel unwind info */
	static int unwind_init(void)
	{
	long start, stop;
	register unsigned long gp __asm__ ("r27");

	start = (long)&__start___unwind[0];
	stop = (long)&__stop___unwind[0];

	spin_lock_init(&unwind_lock);

	printk("unwind_init: start = 0x%lx, end = 0x%lx, entries = %lu\n",
	start, stop,
	(stop - start) / sizeof(struct unwind_table_entry));

	unwind_table_init(&kernel_unwind_table, "kernel", KERNEL_START,
	gp,
	&__start___unwind[0], &__stop___unwind[0]);
	#if 0
	{
	int i;
	for (i = 0; i < 10; i++)
	{
	printk("region 0x%x-0x%x\n",
	__start___unwind[i].region_start,
	__start___unwind[i].region_end);
	}
	}
	#endif
	return 0;
	}

	static void unwind_frame_regs(struct unwind_frame_info *info)
	{
	const struct unwind_table_entry *e;
	unsigned long npc;
	unsigned int insn;
	long frame_size = 0;
	int looking_for_rp, rpoffset = 0;

	e = find_unwind_entry(info->ip);
	if (e == NULL) {
	unsigned long sp;
	extern char _stext[], _etext[];

	dbg("Cannot find unwind entry for 0x%lx; forced unwinding\n", info->ip);

	#ifdef CONFIG_KALLSYMS
	/* Handle some frequent special cases.... */
	{
	char symname[KSYM_NAME_LEN+1];
	char *modname;

	kallsyms_lookup(info->ip, NULL, NULL, &modname,
	symname);

	dbg("info->ip = 0x%lx, name = %s\n", info->ip, symname);

	if (strcmp(symname, "_switch_to_ret") == 0) {
	info->prev_sp = info->sp - CALLEE_SAVE_FRAME_SIZE;
	info->prev_ip = (unsigned long )(info->prev_sp - RP_OFFSET);
	dbg("_switch_to_ret @ %lx - setting "
	"prev_sp=%lx prev_ip=%lx\n",
	info->ip, info->prev_sp,
	info->prev_ip);
	return;
	} else if (strcmp(symname, "ret_from_kernel_thread") == 0 \|\|
	strcmp(symname, "syscall_exit") == 0) {
	info->prev_ip = info->prev_sp = 0;
	return;
	}
	}
	#endif

	/* Since we are doing the unwinding blind, we don't know if
	we are adjusting the stack correctly or extracting the rp
	correctly. The rp is checked to see if it belongs to the
	kernel text section, if not we assume we don't have a
	correct stack frame and we continue to unwind the stack.
	This is not quite correct, and will fail for loadable
	modules. */
	sp = info->sp & ~63;
	do {
	unsigned long tmp;

	info->prev_sp = sp - 64;
	info->prev_ip = 0;
	if (get_user(tmp, (unsigned long *)(info->prev_sp - RP_OFFSET)))
	break;
	info->prev_ip = tmp;
	sp = info->prev_sp;
	} while (info->prev_ip < (unsigned long)_stext \|\|
	info->prev_ip > (unsigned long)_etext);

	info->rp = 0;

	dbg("analyzing func @ %lx with no unwind info, setting "
	"prev_sp=%lx prev_ip=%lx\n", info->ip,
	info->prev_sp, info->prev_ip);
	} else {
	dbg("e->start = 0x%x, e->end = 0x%x, Save_SP = %d, "
	"Save_RP = %d, Millicode = %d size = %u\n",
	e->region_start, e->region_end, e->Save_SP, e->Save_RP,
	e->Millicode, e->Total_frame_size);

	looking_for_rp = e->Save_RP;

	for (npc = e->region_start;
	(frame_size < (e->Total_frame_size << 3) \|\|
	looking_for_rp) &&
	npc < info->ip;
	npc += 4) {

	insn = (unsigned int )npc;

	if ((insn & 0xffffc000) == 0x37de0000 \|\|
	(insn & 0xffe00000) == 0x6fc00000) {
	/* ldo X(sp), sp, or stwm X,D(sp) */
	frame_size += (insn & 0x1 ? -1 << 13 : 0) \|
	((insn & 0x3fff) >> 1);
	dbg("analyzing func @ %lx, insn=%08x @ "
	"%lx, frame_size = %ld\n", info->ip,
	insn, npc, frame_size);
	} else if ((insn & 0xffe00008) == 0x73c00008) {
	/* std,ma X,D(sp) */
	frame_size += (insn & 0x1 ? -1 << 13 : 0) \|
	(((insn >> 4) & 0x3ff) << 3);
	dbg("analyzing func @ %lx, insn=%08x @ "
	"%lx, frame_size = %ld\n", info->ip,
	insn, npc, frame_size);
	} else if (insn == 0x6bc23fd9) {
	/* stw rp,-20(sp) */
	rpoffset = 20;
	looking_for_rp = 0;
	dbg("analyzing func @ %lx, insn=stw rp,"
	"-20(sp) @ %lx\n", info->ip, npc);
	} else if (insn == 0x0fc212c1) {
	/* std rp,-16(sr0,sp) */
	rpoffset = 16;
	looking_for_rp = 0;
	dbg("analyzing func @ %lx, insn=std rp,"
	"-16(sp) @ %lx\n", info->ip, npc);
	}
	}

	info->prev_sp = info->sp - frame_size;
	if (e->Millicode)
	info->rp = info->r31;
	else if (rpoffset)
	info->rp = (unsigned long )(info->prev_sp - rpoffset);
	info->prev_ip = info->rp;
	info->rp = 0;

	dbg("analyzing func @ %lx, setting prev_sp=%lx "
	"prev_ip=%lx npc=%lx\n", info->ip, info->prev_sp,
	info->prev_ip, npc);
	}
	}

	void unwind_frame_init(struct unwind_frame_info info, struct task_struct t,
	struct pt_regs *regs)
	{
	memset(info, 0, sizeof(struct unwind_frame_info));
	info->t = t;
	info->sp = regs->gr[30];
	info->ip = regs->iaoq[0];
	info->rp = regs->gr[2];
	info->r31 = regs->gr[31];

	dbg("(%d) Start unwind from sp=%08lx ip=%08lx\n",
	t ? (int)t->pid : -1, info->sp, info->ip);
	}

	void unwind_frame_init_from_blocked_task(struct unwind_frame_info info, struct task_struct t)
	{
	struct pt_regs *r = &t->thread.regs;
	struct pt_regs *r2;

	r2 = kmalloc(sizeof(struct pt_regs), GFP_KERNEL);
	if (!r2)
	return;
	r2 = r;
	r2->gr[30] = r->ksp;
	r2->iaoq[0] = r->kpc;
	unwind_frame_init(info, t, r2);
	kfree(r2);
	}

	void unwind_frame_init_running(struct unwind_frame_info info, struct pt_regs regs)
	{
	unwind_frame_init(info, current, regs);
	}

	int unwind_once(struct unwind_frame_info *next_frame)
	{
	unwind_frame_regs(next_frame);

	if (next_frame->prev_sp == 0 \|\|
	next_frame->prev_ip == 0)
	return -1;

	next_frame->sp = next_frame->prev_sp;
	next_frame->ip = next_frame->prev_ip;
	next_frame->prev_sp = 0;
	next_frame->prev_ip = 0;

	dbg("(%d) Continue unwind to sp=%08lx ip=%08lx\n",
	next_frame->t ? (int)next_frame->t->pid : -1,
	next_frame->sp, next_frame->ip);

	return 0;
	}

	int unwind_to_user(struct unwind_frame_info *info)
	{
	int ret;

	do {
	ret = unwind_once(info);
	} while (!ret && !(info->ip & 3));

	return ret;
	}

	module_init(unwind_init);