[deliverable/linux.git] / arch / parisc / kernel / unwind.c

/*
 * 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/config.h>
#include <linux/kernel.h>
#include <linux/init.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;
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;
			unsigned long symsize, offset;

			kallsyms_lookup(info->ip, &symsize, &offset,
					&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 = (struct pt_regs *)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);
Commit	Line	Data
1da177e4 LT	1	/*
	2	* Kernel unwinding support
	3	*
	4	* (c) 2002-2004 Randolph Chung <tausq@debian.org>
	5	*
	6	* Derived partially from the IA64 implementation. The PA-RISC
	7	* Runtime Architecture Document is also a useful reference to
	8	* understand what is happening here
	9	*/
	10
	11	#include <linux/config.h>
	12	#include <linux/kernel.h>
	13	#include <linux/init.h>
	14	#include <linux/slab.h>
	15	#include <linux/kallsyms.h>
	16
	17	#include <asm/uaccess.h>
	18	#include <asm/assembly.h>
	19
	20	#include <asm/unwind.h>
	21
	22	/* #define DEBUG 1 */
	23	#ifdef DEBUG
	24	#define dbg(x...) printk(x)
	25	#else
	26	#define dbg(x...)
	27	#endif
	28
	29	extern struct unwind_table_entry __start___unwind[];
	30	extern struct unwind_table_entry __stop___unwind[];
	31
	32	static spinlock_t unwind_lock;
	33	/*
	34	* the kernel unwind block is not dynamically allocated so that
	35	* we can call unwind_init as early in the bootup process as
	36	* possible (before the slab allocator is initialized)
	37	*/
	38	static struct unwind_table kernel_unwind_table;
	39	static LIST_HEAD(unwind_tables);
	40
	41	static inline const struct unwind_table_entry *
	42	find_unwind_entry_in_table(const struct unwind_table *table, unsigned long addr)
	43	{
	44	const struct unwind_table_entry *e = NULL;
	45	unsigned long lo, hi, mid;
	46
	47	lo = 0;
	48	hi = table->length - 1;
	49
	50	while (lo <= hi) {
	51	mid = (hi - lo) / 2 + lo;
	52	e = &table->table[mid];
	53	if (addr < e->region_start)
	54	hi = mid - 1;
	55	else if (addr > e->region_end)
	56	lo = mid + 1;
	57	else
	58	return e;
	59	}
	60
	61	return NULL;
	62	}
	63
	64	static const struct unwind_table_entry *
65	find_unwind_entry(unsigned long addr)
66	{
67	struct unwind_table *table;
68	const struct unwind_table_entry *e = NULL;
69
70	if (addr >= kernel_unwind_table.start &&
71	addr <= kernel_unwind_table.end)
72	e = find_unwind_entry_in_table(&kernel_unwind_table, addr);
73	else
74	list_for_each_entry(table, &unwind_tables, list) {
75	if (addr >= table->start &&
76	addr <= table->end)
77	e = find_unwind_entry_in_table(table, addr);
78	if (e)
79	break;
80	}
81
82	return e;
83	}
84
85	static void
86	unwind_table_init(struct unwind_table table, const char name,
87	unsigned long base_addr, unsigned long gp,
88	void table_start, void table_end)
89	{
90	struct unwind_table_entry *start = table_start;
91	struct unwind_table_entry *end =
92	(struct unwind_table_entry *)table_end - 1;
93
94	table->name = name;
95	table->base_addr = base_addr;
96	table->gp = gp;
97	table->start = base_addr + start->region_start;
98	table->end = base_addr + end->region_end;
99	table->table = (struct unwind_table_entry *)table_start;
100	table->length = end - start + 1;
101	INIT_LIST_HEAD(&table->list);
102
103	for (; start <= end; start++) {
104	if (start < end &&
105	start->region_end > (start+1)->region_start) {
106	printk("WARNING: Out of order unwind entry! %p and %p\n", start, start+1);
107	}
108
109	start->region_start += base_addr;
110	start->region_end += base_addr;
111	}
112	}
113
114	static void
115	unwind_table_sort(struct unwind_table_entry *start,
116	struct unwind_table_entry *finish)
117	{
118	struct unwind_table_entry el, p, q;
119
120	for (p = start + 1; p < finish; ++p) {
121	if (p[0].region_start < p[-1].region_start) {
122	el = *p;
123	q = p;
124	do {
125	q[0] = q[-1];
126	--q;
127	} while (q > start &&
128	el.region_start < q[-1].region_start);
129	*q = el;
130	}
131	}
132	}
133
134	struct unwind_table *
135	unwind_table_add(const char *name, unsigned long base_addr,
136	unsigned long gp,
137	void start, void end)
138	{
139	struct unwind_table *table;
140	unsigned long flags;
141	struct unwind_table_entry s = (struct unwind_table_entry )start;
142	struct unwind_table_entry e = (struct unwind_table_entry )end;
143
144	unwind_table_sort(s, e);
145
146	table = kmalloc(sizeof(struct unwind_table), GFP_USER);
147	if (table == NULL)
148	return NULL;
149	unwind_table_init(table, name, base_addr, gp, start, end);
150	spin_lock_irqsave(&unwind_lock, flags);
151	list_add_tail(&table->list, &unwind_tables);
152	spin_unlock_irqrestore(&unwind_lock, flags);
153
154	return table;
155	}
156
157	void unwind_table_remove(struct unwind_table *table)
158	{
159	unsigned long flags;
160
161	spin_lock_irqsave(&unwind_lock, flags);
162	list_del(&table->list);
163	spin_unlock_irqrestore(&unwind_lock, flags);
164
165	kfree(table);
166	}
167
168	/* Called from setup_arch to import the kernel unwind info */
169	static int unwind_init(void)
170	{
171	long start, stop;
172	register unsigned long gp __asm__ ("r27");
173
174	start = (long)&__start___unwind[0];
175	stop = (long)&__stop___unwind[0];
176
177	spin_lock_init(&unwind_lock);
178
179	printk("unwind_init: start = 0x%lx, end = 0x%lx, entries = %lu\n",
180	start, stop,
181	(stop - start) / sizeof(struct unwind_table_entry));
182
183	unwind_table_init(&kernel_unwind_table, "kernel", KERNEL_START,
184	gp,
185	&__start___unwind[0], &__stop___unwind[0]);
186	#if 0
187	{
188	int i;
189	for (i = 0; i < 10; i++)
190	{
191	printk("region 0x%x-0x%x\n",
192	__start___unwind[i].region_start,
193	__start___unwind[i].region_end);
194	}
195	}
196	#endif
197	return 0;
198	}
199
200	static void unwind_frame_regs(struct unwind_frame_info *info)
201	{
202	const struct unwind_table_entry *e;
203	unsigned long npc;
204	unsigned int insn;
205	long frame_size = 0;
206	int looking_for_rp, rpoffset = 0;
207
208	e = find_unwind_entry(info->ip);
209	if (e == NULL) {
210	unsigned long sp;
211	extern char _stext[], _etext[];
212
213	dbg("Cannot find unwind entry for 0x%lx; forced unwinding\n", info->ip);
214
215	#ifdef CONFIG_KALLSYMS
216	/* Handle some frequent special cases.... */
217	{
218	char symname[KSYM_NAME_LEN+1];
219	char *modname;
220	unsigned long symsize, offset;
221
222	kallsyms_lookup(info->ip, &symsize, &offset,
223	&modname, symname);
224
225	dbg("info->ip = 0x%lx, name = %s\n", info->ip, symname);
226
227	if (strcmp(symname, "_switch_to_ret") == 0) {
228	info->prev_sp = info->sp - CALLEE_SAVE_FRAME_SIZE;
229	info->prev_ip = (unsigned long )(info->prev_sp - RP_OFFSET);
230	dbg("_switch_to_ret @ %lx - setting "
231	"prev_sp=%lx prev_ip=%lx\n",
232	info->ip, info->prev_sp,
233	info->prev_ip);
234	return;
235	} else if (strcmp(symname, "ret_from_kernel_thread") == 0 \|\|
236	strcmp(symname, "syscall_exit") == 0) {
237	info->prev_ip = info->prev_sp = 0;
238	return;
239	}
240	}
241	#endif
242
243	/* Since we are doing the unwinding blind, we don't know if
244	we are adjusting the stack correctly or extracting the rp
245	correctly. The rp is checked to see if it belongs to the
246	kernel text section, if not we assume we don't have a
247	correct stack frame and we continue to unwind the stack.
248	This is not quite correct, and will fail for loadable
249	modules. */
250	sp = info->sp & ~63;
251	do {
252	unsigned long tmp;
253
254	info->prev_sp = sp - 64;
255	info->prev_ip = 0;
256	if (get_user(tmp, (unsigned long *)(info->prev_sp - RP_OFFSET)))
257	break;
258	info->prev_ip = tmp;
259	sp = info->prev_sp;
260	} while (info->prev_ip < (unsigned long)_stext \|\|
261	info->prev_ip > (unsigned long)_etext);
262
263	info->rp = 0;
264
265	dbg("analyzing func @ %lx with no unwind info, setting "
266	"prev_sp=%lx prev_ip=%lx\n", info->ip,
267	info->prev_sp, info->prev_ip);
268	} else {
269	dbg("e->start = 0x%x, e->end = 0x%x, Save_SP = %d, "
270	"Save_RP = %d, Millicode = %d size = %u\n",
271	e->region_start, e->region_end, e->Save_SP, e->Save_RP,
272	e->Millicode, e->Total_frame_size);
273
274	looking_for_rp = e->Save_RP;
275
276	for (npc = e->region_start;
277	(frame_size < (e->Total_frame_size << 3) \|\|
278	looking_for_rp) &&
279	npc < info->ip;
280	npc += 4) {
281
282	insn = (unsigned int )npc;
283
284	if ((insn & 0xffffc000) == 0x37de0000 \|\|
285	(insn & 0xffe00000) == 0x6fc00000) {
286	/* ldo X(sp), sp, or stwm X,D(sp) */
287	frame_size += (insn & 0x1 ? -1 << 13 : 0) \|
288	((insn & 0x3fff) >> 1);
289	dbg("analyzing func @ %lx, insn=%08x @ "
290	"%lx, frame_size = %ld\n", info->ip,
291	insn, npc, frame_size);
292	} else if ((insn & 0xffe00008) == 0x73c00008) {
293	/* std,ma X,D(sp) */
294	frame_size += (insn & 0x1 ? -1 << 13 : 0) \|
295	(((insn >> 4) & 0x3ff) << 3);
296	dbg("analyzing func @ %lx, insn=%08x @ "
297	"%lx, frame_size = %ld\n", info->ip,
298	insn, npc, frame_size);
299	} else if (insn == 0x6bc23fd9) {
300	/* stw rp,-20(sp) */
301	rpoffset = 20;
302	looking_for_rp = 0;
303	dbg("analyzing func @ %lx, insn=stw rp,"
304	"-20(sp) @ %lx\n", info->ip, npc);
305	} else if (insn == 0x0fc212c1) {
306	/* std rp,-16(sr0,sp) */
307	rpoffset = 16;
308	looking_for_rp = 0;
309	dbg("analyzing func @ %lx, insn=std rp,"
310	"-16(sp) @ %lx\n", info->ip, npc);
311	}
312	}
313
314	info->prev_sp = info->sp - frame_size;
315	if (e->Millicode)
316	info->rp = info->r31;
317	else if (rpoffset)
318	info->rp = (unsigned long )(info->prev_sp - rpoffset);
319	info->prev_ip = info->rp;
320	info->rp = 0;
321
322	dbg("analyzing func @ %lx, setting prev_sp=%lx "
323	"prev_ip=%lx npc=%lx\n", info->ip, info->prev_sp,
324	info->prev_ip, npc);
325	}
326	}
327
328	void unwind_frame_init(struct unwind_frame_info info, struct task_struct t,
329	struct pt_regs *regs)
330	{
331	memset(info, 0, sizeof(struct unwind_frame_info));
332	info->t = t;
333	info->sp = regs->gr[30];
334	info->ip = regs->iaoq[0];
335	info->rp = regs->gr[2];
336	info->r31 = regs->gr[31];
337
338	dbg("(%d) Start unwind from sp=%08lx ip=%08lx\n",
339	t ? (int)t->pid : -1, info->sp, info->ip);
340	}
341
342	void unwind_frame_init_from_blocked_task(struct unwind_frame_info info, struct task_struct t)
343	{
344	struct pt_regs *r = &t->thread.regs;
345	struct pt_regs *r2;
346
347	r2 = (struct pt_regs *)kmalloc(sizeof(struct pt_regs), GFP_KERNEL);
348	if (!r2)
349	return;
350	r2 = r;
351	r2->gr[30] = r->ksp;
352	r2->iaoq[0] = r->kpc;
353	unwind_frame_init(info, t, r2);
354	kfree(r2);
355	}
356
357	void unwind_frame_init_running(struct unwind_frame_info info, struct pt_regs regs)
358	{
359	unwind_frame_init(info, current, regs);
360	}
361
362	int unwind_once(struct unwind_frame_info *next_frame)
363	{
364	unwind_frame_regs(next_frame);
365
366	if (next_frame->prev_sp == 0 \|\|
367	next_frame->prev_ip == 0)
368	return -1;
369
370	next_frame->sp = next_frame->prev_sp;
371	next_frame->ip = next_frame->prev_ip;
372	next_frame->prev_sp = 0;
373	next_frame->prev_ip = 0;
374
375	dbg("(%d) Continue unwind to sp=%08lx ip=%08lx\n",
376	next_frame->t ? (int)next_frame->t->pid : -1,
377	next_frame->sp, next_frame->ip);
378
379	return 0;
380	}
381
382	int unwind_to_user(struct unwind_frame_info *info)
383	{
384	int ret;
385
386	do {
387	ret = unwind_once(info);
388	} while (!ret && !(info->ip & 3));
389
390	return ret;
391	}
392
393	module_init(unwind_init);