[thirdparty/kernel/stable.git] / kernel / stacktrace.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * kernel/stacktrace.c
 *
 * Stack trace management functions
 *
 *  Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 */
#include <linux/sched/task_stack.h>
#include <linux/sched/debug.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/kallsyms.h>
#include <linux/stacktrace.h>

/**
 * stack_trace_print - Print the entries in the stack trace
 * @entries:	Pointer to storage array
 * @nr_entries:	Number of entries in the storage array
 * @spaces:	Number of leading spaces to print
 */
void stack_trace_print(unsigned long *entries, unsigned int nr_entries,
		       int spaces)
{
	unsigned int i;

	if (WARN_ON(!entries))
		return;

	for (i = 0; i < nr_entries; i++)
		printk("%*c%pS\n", 1 + spaces, ' ', (void *)entries[i]);
}
EXPORT_SYMBOL_GPL(stack_trace_print);

/**
 * stack_trace_snprint - Print the entries in the stack trace into a buffer
 * @buf:	Pointer to the print buffer
 * @size:	Size of the print buffer
 * @entries:	Pointer to storage array
 * @nr_entries:	Number of entries in the storage array
 * @spaces:	Number of leading spaces to print
 *
 * Return: Number of bytes printed.
 */
int stack_trace_snprint(char *buf, size_t size, unsigned long *entries,
			unsigned int nr_entries, int spaces)
{
	unsigned int generated, i, total = 0;

	if (WARN_ON(!entries))
		return 0;

	for (i = 0; i < nr_entries && size; i++) {
		generated = snprintf(buf, size, "%*c%pS\n", 1 + spaces, ' ',
				     (void *)entries[i]);

		total += generated;
		if (generated >= size) {
			buf += size;
			size = 0;
		} else {
			buf += generated;
			size -= generated;
		}
	}

	return total;
}
EXPORT_SYMBOL_GPL(stack_trace_snprint);

#ifdef CONFIG_ARCH_STACKWALK

struct stacktrace_cookie {
	unsigned long	*store;
	unsigned int	size;
	unsigned int	skip;
	unsigned int	len;
};

static bool stack_trace_consume_entry(void *cookie, unsigned long addr,
				      bool reliable)
{
	struct stacktrace_cookie *c = cookie;

	if (c->len >= c->size)
		return false;

	if (c->skip > 0) {
		c->skip--;
		return true;
	}
	c->store[c->len++] = addr;
	return c->len < c->size;
}

static bool stack_trace_consume_entry_nosched(void *cookie, unsigned long addr,
					      bool reliable)
{
	if (in_sched_functions(addr))
		return true;
	return stack_trace_consume_entry(cookie, addr, reliable);
}

/**
 * stack_trace_save - Save a stack trace into a storage array
 * @store:	Pointer to storage array
 * @size:	Size of the storage array
 * @skipnr:	Number of entries to skip at the start of the stack trace
 *
 * Return: Number of trace entries stored.
 */
unsigned int stack_trace_save(unsigned long *store, unsigned int size,
			      unsigned int skipnr)
{
	stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
	struct stacktrace_cookie c = {
		.store	= store,
		.size	= size,
		.skip	= skipnr + 1,
	};

	arch_stack_walk(consume_entry, &c, current, NULL);
	return c.len;
}
EXPORT_SYMBOL_GPL(stack_trace_save);

/**
 * stack_trace_save_tsk - Save a task stack trace into a storage array
 * @task:	The task to examine
 * @store:	Pointer to storage array
 * @size:	Size of the storage array
 * @skipnr:	Number of entries to skip at the start of the stack trace
 *
 * Return: Number of trace entries stored.
 */
unsigned int stack_trace_save_tsk(struct task_struct *tsk, unsigned long *store,
				  unsigned int size, unsigned int skipnr)
{
	stack_trace_consume_fn consume_entry = stack_trace_consume_entry_nosched;
	struct stacktrace_cookie c = {
		.store	= store,
		.size	= size,
		.skip	= skipnr + 1,
	};

	if (!try_get_task_stack(tsk))
		return 0;

	arch_stack_walk(consume_entry, &c, tsk, NULL);
	put_task_stack(tsk);
	return c.len;
}

/**
 * stack_trace_save_regs - Save a stack trace based on pt_regs into a storage array
 * @regs:	Pointer to pt_regs to examine
 * @store:	Pointer to storage array
 * @size:	Size of the storage array
 * @skipnr:	Number of entries to skip at the start of the stack trace
 *
 * Return: Number of trace entries stored.
 */
unsigned int stack_trace_save_regs(struct pt_regs *regs, unsigned long *store,
				   unsigned int size, unsigned int skipnr)
{
	stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
	struct stacktrace_cookie c = {
		.store	= store,
		.size	= size,
		.skip	= skipnr,
	};

	arch_stack_walk(consume_entry, &c, current, regs);
	return c.len;
}

#ifdef CONFIG_HAVE_RELIABLE_STACKTRACE
/**
 * stack_trace_save_tsk_reliable - Save task stack with verification
 * @tsk:	Pointer to the task to examine
 * @store:	Pointer to storage array
 * @size:	Size of the storage array
 *
 * Return:	An error if it detects any unreliable features of the
 *		stack. Otherwise it guarantees that the stack trace is
 *		reliable and returns the number of entries stored.
 *
 * If the task is not 'current', the caller *must* ensure the task is inactive.
 */
int stack_trace_save_tsk_reliable(struct task_struct *tsk, unsigned long *store,
				  unsigned int size)
{
	stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
	struct stacktrace_cookie c = {
		.store	= store,
		.size	= size,
	};
	int ret;

	/*
	 * If the task doesn't have a stack (e.g., a zombie), the stack is
	 * "reliably" empty.
	 */
	if (!try_get_task_stack(tsk))
		return 0;

	ret = arch_stack_walk_reliable(consume_entry, &c, tsk);
	put_task_stack(tsk);
	return ret ? ret : c.len;
}
#endif

#ifdef CONFIG_USER_STACKTRACE_SUPPORT
/**
 * stack_trace_save_user - Save a user space stack trace into a storage array
 * @store:	Pointer to storage array
 * @size:	Size of the storage array
 *
 * Return: Number of trace entries stored.
 */
unsigned int stack_trace_save_user(unsigned long *store, unsigned int size)
{
	stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
	struct stacktrace_cookie c = {
		.store	= store,
		.size	= size,
	};

	/* Trace user stack if not a kernel thread */
	if (!current->mm)
		return 0;

	arch_stack_walk_user(consume_entry, &c, task_pt_regs(current));
	return c.len;
}
#endif

#else /* CONFIG_ARCH_STACKWALK */

/*
 * Architectures that do not implement save_stack_trace_*()
 * get these weak aliases and once-per-bootup warnings
 * (whenever this facility is utilized - for example by procfs):
 */
__weak void
save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
{
	WARN_ONCE(1, KERN_INFO "save_stack_trace_tsk() not implemented yet.\n");
}

__weak void
save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
{
	WARN_ONCE(1, KERN_INFO "save_stack_trace_regs() not implemented yet.\n");
}

__weak int
save_stack_trace_tsk_reliable(struct task_struct *tsk,
			      struct stack_trace *trace)
{
	WARN_ONCE(1, KERN_INFO "save_stack_tsk_reliable() not implemented yet.\n");
	return -ENOSYS;
}

/**
 * stack_trace_save - Save a stack trace into a storage array
 * @store:	Pointer to storage array
 * @size:	Size of the storage array
 * @skipnr:	Number of entries to skip at the start of the stack trace
 *
 * Return: Number of trace entries stored
 */
unsigned int stack_trace_save(unsigned long *store, unsigned int size,
			      unsigned int skipnr)
{
	struct stack_trace trace = {
		.entries	= store,
		.max_entries	= size,
		.skip		= skipnr + 1,
	};

	save_stack_trace(&trace);
	return trace.nr_entries;
}
EXPORT_SYMBOL_GPL(stack_trace_save);

/**
 * stack_trace_save_tsk - Save a task stack trace into a storage array
 * @task:	The task to examine
 * @store:	Pointer to storage array
 * @size:	Size of the storage array
 * @skipnr:	Number of entries to skip at the start of the stack trace
 *
 * Return: Number of trace entries stored
 */
unsigned int stack_trace_save_tsk(struct task_struct *task,
				  unsigned long *store, unsigned int size,
				  unsigned int skipnr)
{
	struct stack_trace trace = {
		.entries	= store,
		.max_entries	= size,
		.skip		= skipnr + 1,
	};

	save_stack_trace_tsk(task, &trace);
	return trace.nr_entries;
}

/**
 * stack_trace_save_regs - Save a stack trace based on pt_regs into a storage array
 * @regs:	Pointer to pt_regs to examine
 * @store:	Pointer to storage array
 * @size:	Size of the storage array
 * @skipnr:	Number of entries to skip at the start of the stack trace
 *
 * Return: Number of trace entries stored
 */
unsigned int stack_trace_save_regs(struct pt_regs *regs, unsigned long *store,
				   unsigned int size, unsigned int skipnr)
{
	struct stack_trace trace = {
		.entries	= store,
		.max_entries	= size,
		.skip		= skipnr,
	};

	save_stack_trace_regs(regs, &trace);
	return trace.nr_entries;
}

#ifdef CONFIG_HAVE_RELIABLE_STACKTRACE
/**
 * stack_trace_save_tsk_reliable - Save task stack with verification
 * @tsk:	Pointer to the task to examine
 * @store:	Pointer to storage array
 * @size:	Size of the storage array
 *
 * Return:	An error if it detects any unreliable features of the
 *		stack. Otherwise it guarantees that the stack trace is
 *		reliable and returns the number of entries stored.
 *
 * If the task is not 'current', the caller *must* ensure the task is inactive.
 */
int stack_trace_save_tsk_reliable(struct task_struct *tsk, unsigned long *store,
				  unsigned int size)
{
	struct stack_trace trace = {
		.entries	= store,
		.max_entries	= size,
	};
	int ret = save_stack_trace_tsk_reliable(tsk, &trace);

	return ret ? ret : trace.nr_entries;
}
#endif

#ifdef CONFIG_USER_STACKTRACE_SUPPORT
/**
 * stack_trace_save_user - Save a user space stack trace into a storage array
 * @store:	Pointer to storage array
 * @size:	Size of the storage array
 *
 * Return: Number of trace entries stored
 */
unsigned int stack_trace_save_user(unsigned long *store, unsigned int size)
{
	struct stack_trace trace = {
		.entries	= store,
		.max_entries	= size,
	};

	save_stack_trace_user(&trace);
	return trace.nr_entries;
}
#endif /* CONFIG_USER_STACKTRACE_SUPPORT */

#endif /* !CONFIG_ARCH_STACKWALK */
Commit	Line	Data
457c8996	1	// SPDX-License-Identifier: GPL-2.0-only
8637c099 IM	2	/*
	3	* kernel/stacktrace.c
	4	*
	5	* Stack trace management functions
	6	*
	7	* Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
	8	*/
214d8ca6 TG	9	#include <linux/sched/task_stack.h>
214d8ca6 TG	10	#include <linux/sched/debug.h>
8637c099	11	#include <linux/sched.h>
9212ddb5	12	#include <linux/kernel.h>
9984de1a	13	#include <linux/export.h>
8637c099 IM	14	#include <linux/kallsyms.h>
	15	#include <linux/stacktrace.h>
	16
e9b98e16 TG	17	/**
	18	* stack_trace_print - Print the entries in the stack trace
	19	* @entries: Pointer to storage array
	20	* @nr_entries: Number of entries in the storage array
	21	* @spaces: Number of leading spaces to print
	22	*/
	23	void stack_trace_print(unsigned long *entries, unsigned int nr_entries,
	24	int spaces)
8637c099	25	{
e9b98e16	26	unsigned int i;
8637c099	27
e9b98e16	28	if (WARN_ON(!entries))
bfeeeeb9 JB	29	return;
bfeeeeb9 JB	30
e9b98e16 TG	31	for (i = 0; i < nr_entries; i++)
	32	printk("%c%pS\n", 1 + spaces, ' ', (void )entries[i]);
	33	}
	34	EXPORT_SYMBOL_GPL(stack_trace_print);
	35
e9b98e16 TG	36	/**
	37	* stack_trace_snprint - Print the entries in the stack trace into a buffer
	38	* @buf: Pointer to the print buffer
	39	* @size: Size of the print buffer
	40	* @entries: Pointer to storage array
	41	* @nr_entries: Number of entries in the storage array
	42	* @spaces: Number of leading spaces to print
	43	*
	44	* Return: Number of bytes printed.
	45	*/
	46	int stack_trace_snprint(char buf, size_t size, unsigned long entries,
	47	unsigned int nr_entries, int spaces)
9a92a6ce	48	{
e9b98e16	49	unsigned int generated, i, total = 0;
9a92a6ce	50
e9b98e16	51	if (WARN_ON(!entries))
9a92a6ce JK	52	return 0;
9a92a6ce JK	53
e9b98e16	54	for (i = 0; i < nr_entries && size; i++) {
bfeda41d	55	generated = snprintf(buf, size, "%*c%pS\n", 1 + spaces, ' ',
e9b98e16	56	(void *)entries[i]);
9a92a6ce JK	57
9a92a6ce JK	58	total += generated;
9a92a6ce JK	59	if (generated >= size) {
	60	buf += size;
	61	size = 0;
	62	} else {
	63	buf += generated;
	64	size -= generated;
	65	}
	66	}
	67
	68	return total;
	69	}
e9b98e16 TG	70	EXPORT_SYMBOL_GPL(stack_trace_snprint);
e9b98e16 TG	71
214d8ca6 TG	72	#ifdef CONFIG_ARCH_STACKWALK
	73
	74	struct stacktrace_cookie {
	75	unsigned long *store;
	76	unsigned int size;
	77	unsigned int skip;
	78	unsigned int len;
	79	};
	80
	81	static bool stack_trace_consume_entry(void *cookie, unsigned long addr,
	82	bool reliable)
	83	{
	84	struct stacktrace_cookie *c = cookie;
	85
	86	if (c->len >= c->size)
	87	return false;
	88
	89	if (c->skip > 0) {
	90	c->skip--;
	91	return true;
	92	}
	93	c->store[c->len++] = addr;
	94	return c->len < c->size;
	95	}
	96
	97	static bool stack_trace_consume_entry_nosched(void *cookie, unsigned long addr,
	98	bool reliable)
	99	{
	100	if (in_sched_functions(addr))
	101	return true;
	102	return stack_trace_consume_entry(cookie, addr, reliable);
	103	}
	104
	105	/**
	106	* stack_trace_save - Save a stack trace into a storage array
	107	* @store: Pointer to storage array
	108	* @size: Size of the storage array
	109	* @skipnr: Number of entries to skip at the start of the stack trace
	110	*
	111	* Return: Number of trace entries stored.
	112	*/
	113	unsigned int stack_trace_save(unsigned long *store, unsigned int size,
	114	unsigned int skipnr)
	115	{
	116	stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
	117	struct stacktrace_cookie c = {
	118	.store = store,
	119	.size = size,
	120	.skip = skipnr + 1,
	121	};
	122
	123	arch_stack_walk(consume_entry, &c, current, NULL);
	124	return c.len;
	125	}
	126	EXPORT_SYMBOL_GPL(stack_trace_save);
	127
	128	/**
	129	* stack_trace_save_tsk - Save a task stack trace into a storage array
	130	* @task: The task to examine
	131	* @store: Pointer to storage array
	132	* @size: Size of the storage array
	133	* @skipnr: Number of entries to skip at the start of the stack trace
	134	*
	135	* Return: Number of trace entries stored.
136	*/
137	unsigned int stack_trace_save_tsk(struct task_struct tsk, unsigned long store,
138	unsigned int size, unsigned int skipnr)
139	{
140	stack_trace_consume_fn consume_entry = stack_trace_consume_entry_nosched;
141	struct stacktrace_cookie c = {
142	.store = store,
143	.size = size,
144	.skip = skipnr + 1,
145	};
146
147	if (!try_get_task_stack(tsk))
148	return 0;
149
150	arch_stack_walk(consume_entry, &c, tsk, NULL);
151	put_task_stack(tsk);
152	return c.len;
153	}
154
155	/**
156	* stack_trace_save_regs - Save a stack trace based on pt_regs into a storage array
157	* @regs: Pointer to pt_regs to examine
158	* @store: Pointer to storage array
159	* @size: Size of the storage array
160	* @skipnr: Number of entries to skip at the start of the stack trace
161	*
162	* Return: Number of trace entries stored.
163	*/
164	unsigned int stack_trace_save_regs(struct pt_regs regs, unsigned long store,
165	unsigned int size, unsigned int skipnr)
166	{
167	stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
168	struct stacktrace_cookie c = {
169	.store = store,
170	.size = size,
171	.skip = skipnr,
172	};
173
174	arch_stack_walk(consume_entry, &c, current, regs);
175	return c.len;
176	}
177
178	#ifdef CONFIG_HAVE_RELIABLE_STACKTRACE
179	/**
180	* stack_trace_save_tsk_reliable - Save task stack with verification
181	* @tsk: Pointer to the task to examine
182	* @store: Pointer to storage array
183	* @size: Size of the storage array
184	*
185	* Return: An error if it detects any unreliable features of the
186	* stack. Otherwise it guarantees that the stack trace is
187	* reliable and returns the number of entries stored.
188	*
189	* If the task is not 'current', the caller must ensure the task is inactive.
190	*/
191	int stack_trace_save_tsk_reliable(struct task_struct tsk, unsigned long store,
192	unsigned int size)
193	{
194	stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
195	struct stacktrace_cookie c = {
196	.store = store,
197	.size = size,
198	};
199	int ret;
200
201	/*
202	* If the task doesn't have a stack (e.g., a zombie), the stack is
203	* "reliably" empty.
204	*/
205	if (!try_get_task_stack(tsk))
206	return 0;
207
208	ret = arch_stack_walk_reliable(consume_entry, &c, tsk);
209	put_task_stack(tsk);
7eaf51a2	210	return ret ? ret : c.len;
214d8ca6 TG	211	}
	212	#endif
	213
	214	#ifdef CONFIG_USER_STACKTRACE_SUPPORT
	215	/**
	216	* stack_trace_save_user - Save a user space stack trace into a storage array
	217	* @store: Pointer to storage array
	218	* @size: Size of the storage array
	219	*
	220	* Return: Number of trace entries stored.
	221	*/
	222	unsigned int stack_trace_save_user(unsigned long *store, unsigned int size)
	223	{
	224	stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
	225	struct stacktrace_cookie c = {
	226	.store = store,
	227	.size = size,
	228	};
	229
	230	/* Trace user stack if not a kernel thread */
	231	if (!current->mm)
	232	return 0;
	233
	234	arch_stack_walk_user(consume_entry, &c, task_pt_regs(current));
	235	return c.len;
	236	}
	237	#endif
	238
	239	#else /* CONFIG_ARCH_STACKWALK */
	240
9212ddb5	241	/*
af085d90 JP	242	* Architectures that do not implement save_stack_trace_*()
af085d90 JP	243	* get these weak aliases and once-per-bootup warnings
c624d33f	244	* (whenever this facility is utilized - for example by procfs):
9212ddb5 IM	245	*/
	246	__weak void
	247	save_stack_trace_tsk(struct task_struct tsk, struct stack_trace trace)
	248	{
	249	WARN_ONCE(1, KERN_INFO "save_stack_trace_tsk() not implemented yet.\n");
	250	}
c624d33f MH	251
	252	__weak void
	253	save_stack_trace_regs(struct pt_regs regs, struct stack_trace trace)
	254	{
	255	WARN_ONCE(1, KERN_INFO "save_stack_trace_regs() not implemented yet.\n");
	256	}
af085d90 JP	257
	258	__weak int
	259	save_stack_trace_tsk_reliable(struct task_struct *tsk,
	260	struct stack_trace *trace)
	261	{
	262	WARN_ONCE(1, KERN_INFO "save_stack_tsk_reliable() not implemented yet.\n");
	263	return -ENOSYS;
	264	}
e9b98e16 TG	265
	266	/**
	267	* stack_trace_save - Save a stack trace into a storage array
	268	* @store: Pointer to storage array
	269	* @size: Size of the storage array
	270	* @skipnr: Number of entries to skip at the start of the stack trace
	271	*
	272	* Return: Number of trace entries stored
	273	*/
	274	unsigned int stack_trace_save(unsigned long *store, unsigned int size,
	275	unsigned int skipnr)
	276	{
	277	struct stack_trace trace = {
	278	.entries = store,
	279	.max_entries = size,
	280	.skip = skipnr + 1,
	281	};
	282
	283	save_stack_trace(&trace);
	284	return trace.nr_entries;
	285	}
	286	EXPORT_SYMBOL_GPL(stack_trace_save);
	287
	288	/**
	289	* stack_trace_save_tsk - Save a task stack trace into a storage array
	290	* @task: The task to examine
	291	* @store: Pointer to storage array
	292	* @size: Size of the storage array
	293	* @skipnr: Number of entries to skip at the start of the stack trace
	294	*
	295	* Return: Number of trace entries stored
	296	*/
	297	unsigned int stack_trace_save_tsk(struct task_struct *task,
	298	unsigned long *store, unsigned int size,
	299	unsigned int skipnr)
	300	{
	301	struct stack_trace trace = {
	302	.entries = store,
	303	.max_entries = size,
	304	.skip = skipnr + 1,
	305	};
	306
	307	save_stack_trace_tsk(task, &trace);
	308	return trace.nr_entries;
	309	}
	310
	311	/**
	312	* stack_trace_save_regs - Save a stack trace based on pt_regs into a storage array
	313	* @regs: Pointer to pt_regs to examine
	314	* @store: Pointer to storage array
	315	* @size: Size of the storage array
	316	* @skipnr: Number of entries to skip at the start of the stack trace
	317	*
	318	* Return: Number of trace entries stored
	319	*/
	320	unsigned int stack_trace_save_regs(struct pt_regs regs, unsigned long store,
	321	unsigned int size, unsigned int skipnr)
	322	{
	323	struct stack_trace trace = {
	324	.entries = store,
	325	.max_entries = size,
	326	.skip = skipnr,
	327	};
	328
329	save_stack_trace_regs(regs, &trace);
330	return trace.nr_entries;
331	}
332
333	#ifdef CONFIG_HAVE_RELIABLE_STACKTRACE
334	/**
335	* stack_trace_save_tsk_reliable - Save task stack with verification
336	* @tsk: Pointer to the task to examine
337	* @store: Pointer to storage array
338	* @size: Size of the storage array
339	*
340	* Return: An error if it detects any unreliable features of the
341	* stack. Otherwise it guarantees that the stack trace is
342	* reliable and returns the number of entries stored.
343	*
344	* If the task is not 'current', the caller must ensure the task is inactive.
345	*/
346	int stack_trace_save_tsk_reliable(struct task_struct tsk, unsigned long store,
347	unsigned int size)
348	{
349	struct stack_trace trace = {
350	.entries = store,
351	.max_entries = size,
352	};
353	int ret = save_stack_trace_tsk_reliable(tsk, &trace);
354
355	return ret ? ret : trace.nr_entries;
356	}
357	#endif
358
359	#ifdef CONFIG_USER_STACKTRACE_SUPPORT
360	/**
361	* stack_trace_save_user - Save a user space stack trace into a storage array
362	* @store: Pointer to storage array
363	* @size: Size of the storage array
364	*
365	* Return: Number of trace entries stored
366	*/
367	unsigned int stack_trace_save_user(unsigned long *store, unsigned int size)
368	{
369	struct stack_trace trace = {
370	.entries = store,
371	.max_entries = size,
372	};
373
374	save_stack_trace_user(&trace);
375	return trace.nr_entries;
376	}
377	#endif /* CONFIG_USER_STACKTRACE_SUPPORT */
214d8ca6 TG	378
214d8ca6 TG	379	#endif /* !CONFIG_ARCH_STACKWALK */