[thirdparty/linux.git] / mm / debug.c

// SPDX-License-Identifier: GPL-2.0
/*
 * mm/debug.c
 *
 * mm/ specific debug routines.
 *
 */

#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/trace_events.h>
#include <linux/memcontrol.h>
#include <trace/events/mmflags.h>
#include <linux/migrate.h>
#include <linux/page_owner.h>
#include <linux/ctype.h>

#include "internal.h"

const char *migrate_reason_names[MR_TYPES] = {
	"compaction",
	"memory_failure",
	"memory_hotplug",
	"syscall_or_cpuset",
	"mempolicy_mbind",
	"numa_misplaced",
	"cma",
};

const struct trace_print_flags pageflag_names[] = {
	__def_pageflag_names,
	{0, NULL}
};

const struct trace_print_flags gfpflag_names[] = {
	__def_gfpflag_names,
	{0, NULL}
};

const struct trace_print_flags vmaflag_names[] = {
	__def_vmaflag_names,
	{0, NULL}
};

void __dump_page(struct page *page, const char *reason)
{
	struct page *head = compound_head(page);
	struct address_space *mapping;
	bool page_poisoned = PagePoisoned(page);
	bool compound = PageCompound(page);
	/*
	 * Accessing the pageblock without the zone lock. It could change to
	 * "isolate" again in the meantime, but since we are just dumping the
	 * state for debugging, it should be fine to accept a bit of
	 * inaccuracy here due to racing.
	 */
	bool page_cma = is_migrate_cma_page(page);
	int mapcount;
	char *type = "";

	/*
	 * If struct page is poisoned don't access Page*() functions as that
	 * leads to recursive loop. Page*() check for poisoned pages, and calls
	 * dump_page() when detected.
	 */
	if (page_poisoned) {
		pr_warn("page:%px is uninitialized and poisoned", page);
		goto hex_only;
	}

	if (page < head || (page >= head + MAX_ORDER_NR_PAGES)) {
		/* Corrupt page, cannot call page_mapping */
		mapping = page->mapping;
		head = page;
		compound = false;
	} else {
		mapping = page_mapping(page);
	}

	/*
	 * Avoid VM_BUG_ON() in page_mapcount().
	 * page->_mapcount space in struct page is used by sl[aou]b pages to
	 * encode own info.
	 */
	mapcount = PageSlab(head) ? 0 : page_mapcount(page);

	if (compound)
		if (hpage_pincount_available(page)) {
			pr_warn("page:%px refcount:%d mapcount:%d mapping:%p "
				"index:%#lx head:%px order:%u "
				"compound_mapcount:%d compound_pincount:%d\n",
				page, page_ref_count(head), mapcount,
				mapping, page_to_pgoff(page), head,
				compound_order(head), compound_mapcount(page),
				compound_pincount(page));
		} else {
			pr_warn("page:%px refcount:%d mapcount:%d mapping:%p "
				"index:%#lx head:%px order:%u "
				"compound_mapcount:%d\n",
				page, page_ref_count(head), mapcount,
				mapping, page_to_pgoff(page), head,
				compound_order(head), compound_mapcount(page));
		}
	else
		pr_warn("page:%px refcount:%d mapcount:%d mapping:%p index:%#lx\n",
			page, page_ref_count(page), mapcount,
			mapping, page_to_pgoff(page));
	if (PageKsm(page))
		type = "ksm ";
	else if (PageAnon(page))
		type = "anon ";
	else if (mapping) {
		const struct inode *host;
		const struct address_space_operations *a_ops;
		const struct hlist_node *dentry_first;
		const struct dentry *dentry_ptr;
		struct dentry dentry;

		/*
		 * mapping can be invalid pointer and we don't want to crash
		 * accessing it, so probe everything depending on it carefully
		 */
		if (probe_kernel_read_strict(&host, &mapping->host,
						sizeof(struct inode *)) ||
		    probe_kernel_read_strict(&a_ops, &mapping->a_ops,
				sizeof(struct address_space_operations *))) {
			pr_warn("failed to read mapping->host or a_ops, mapping not a valid kernel address?\n");
			goto out_mapping;
		}

		if (!host) {
			pr_warn("mapping->a_ops:%ps\n", a_ops);
			goto out_mapping;
		}

		if (probe_kernel_read_strict(&dentry_first,
			&host->i_dentry.first, sizeof(struct hlist_node *))) {
			pr_warn("mapping->a_ops:%ps with invalid mapping->host inode address %px\n",
				a_ops, host);
			goto out_mapping;
		}

		if (!dentry_first) {
			pr_warn("mapping->a_ops:%ps\n", a_ops);
			goto out_mapping;
		}

		dentry_ptr = container_of(dentry_first, struct dentry, d_u.d_alias);
		if (probe_kernel_read_strict(&dentry, dentry_ptr,
							sizeof(struct dentry))) {
			pr_warn("mapping->aops:%ps with invalid mapping->host->i_dentry.first %px\n",
				a_ops, dentry_ptr);
		} else {
			/*
			 * if dentry is corrupted, the %pd handler may still
			 * crash, but it's unlikely that we reach here with a
			 * corrupted struct page
			 */
			pr_warn("mapping->aops:%ps dentry name:\"%pd\"\n",
								a_ops, &dentry);
		}
	}
out_mapping:
	BUILD_BUG_ON(ARRAY_SIZE(pageflag_names) != __NR_PAGEFLAGS + 1);

	pr_warn("%sflags: %#lx(%pGp)%s\n", type, page->flags, &page->flags,
		page_cma ? " CMA" : "");

hex_only:
	print_hex_dump(KERN_WARNING, "raw: ", DUMP_PREFIX_NONE, 32,
			sizeof(unsigned long), page,
			sizeof(struct page), false);
	if (head != page)
		print_hex_dump(KERN_WARNING, "head: ", DUMP_PREFIX_NONE, 32,
			sizeof(unsigned long), head,
			sizeof(struct page), false);

	if (reason)
		pr_warn("page dumped because: %s\n", reason);

#ifdef CONFIG_MEMCG
	if (!page_poisoned && page->mem_cgroup)
		pr_warn("page->mem_cgroup:%px\n", page->mem_cgroup);
#endif
}

void dump_page(struct page *page, const char *reason)
{
	__dump_page(page, reason);
	dump_page_owner(page);
}
EXPORT_SYMBOL(dump_page);

#ifdef CONFIG_DEBUG_VM

void dump_vma(const struct vm_area_struct *vma)
{
	pr_emerg("vma %px start %px end %px\n"
		"next %px prev %px mm %px\n"
		"prot %lx anon_vma %px vm_ops %px\n"
		"pgoff %lx file %px private_data %px\n"
		"flags: %#lx(%pGv)\n",
		vma, (void *)vma->vm_start, (void *)vma->vm_end, vma->vm_next,
		vma->vm_prev, vma->vm_mm,
		(unsigned long)pgprot_val(vma->vm_page_prot),
		vma->anon_vma, vma->vm_ops, vma->vm_pgoff,
		vma->vm_file, vma->vm_private_data,
		vma->vm_flags, &vma->vm_flags);
}
EXPORT_SYMBOL(dump_vma);

void dump_mm(const struct mm_struct *mm)
{
	pr_emerg("mm %px mmap %px seqnum %llu task_size %lu\n"
#ifdef CONFIG_MMU
		"get_unmapped_area %px\n"
#endif
		"mmap_base %lu mmap_legacy_base %lu highest_vm_end %lu\n"
		"pgd %px mm_users %d mm_count %d pgtables_bytes %lu map_count %d\n"
		"hiwater_rss %lx hiwater_vm %lx total_vm %lx locked_vm %lx\n"
		"pinned_vm %llx data_vm %lx exec_vm %lx stack_vm %lx\n"
		"start_code %lx end_code %lx start_data %lx end_data %lx\n"
		"start_brk %lx brk %lx start_stack %lx\n"
		"arg_start %lx arg_end %lx env_start %lx env_end %lx\n"
		"binfmt %px flags %lx core_state %px\n"
#ifdef CONFIG_AIO
		"ioctx_table %px\n"
#endif
#ifdef CONFIG_MEMCG
		"owner %px "
#endif
		"exe_file %px\n"
#ifdef CONFIG_MMU_NOTIFIER
		"notifier_subscriptions %px\n"
#endif
#ifdef CONFIG_NUMA_BALANCING
		"numa_next_scan %lu numa_scan_offset %lu numa_scan_seq %d\n"
#endif
		"tlb_flush_pending %d\n"
		"def_flags: %#lx(%pGv)\n",

		mm, mm->mmap, (long long) mm->vmacache_seqnum, mm->task_size,
#ifdef CONFIG_MMU
		mm->get_unmapped_area,
#endif
		mm->mmap_base, mm->mmap_legacy_base, mm->highest_vm_end,
		mm->pgd, atomic_read(&mm->mm_users),
		atomic_read(&mm->mm_count),
		mm_pgtables_bytes(mm),
		mm->map_count,
		mm->hiwater_rss, mm->hiwater_vm, mm->total_vm, mm->locked_vm,
		(u64)atomic64_read(&mm->pinned_vm),
		mm->data_vm, mm->exec_vm, mm->stack_vm,
		mm->start_code, mm->end_code, mm->start_data, mm->end_data,
		mm->start_brk, mm->brk, mm->start_stack,
		mm->arg_start, mm->arg_end, mm->env_start, mm->env_end,
		mm->binfmt, mm->flags, mm->core_state,
#ifdef CONFIG_AIO
		mm->ioctx_table,
#endif
#ifdef CONFIG_MEMCG
		mm->owner,
#endif
		mm->exe_file,
#ifdef CONFIG_MMU_NOTIFIER
		mm->notifier_subscriptions,
#endif
#ifdef CONFIG_NUMA_BALANCING
		mm->numa_next_scan, mm->numa_scan_offset, mm->numa_scan_seq,
#endif
		atomic_read(&mm->tlb_flush_pending),
		mm->def_flags, &mm->def_flags
	);
}

static bool page_init_poisoning __read_mostly = true;

static int __init setup_vm_debug(char *str)
{
	bool __page_init_poisoning = true;

	/*
	 * Calling vm_debug with no arguments is equivalent to requesting
	 * to enable all debugging options we can control.
	 */
	if (*str++ != '=' || !*str)
		goto out;

	__page_init_poisoning = false;
	if (*str == '-')
		goto out;

	while (*str) {
		switch (tolower(*str)) {
		case'p':
			__page_init_poisoning = true;
			break;
		default:
			pr_err("vm_debug option '%c' unknown. skipped\n",
			       *str);
		}

		str++;
	}
out:
	if (page_init_poisoning && !__page_init_poisoning)
		pr_warn("Page struct poisoning disabled by kernel command line option 'vm_debug'\n");

	page_init_poisoning = __page_init_poisoning;

	return 1;
}
__setup("vm_debug", setup_vm_debug);

void page_init_poison(struct page *page, size_t size)
{
	if (page_init_poisoning)
		memset(page, PAGE_POISON_PATTERN, size);
}
EXPORT_SYMBOL_GPL(page_init_poison);
#endif		/* CONFIG_DEBUG_VM */
Commit	Line	Data
b2441318	1	// SPDX-License-Identifier: GPL-2.0
31c9afa6 SL	2	/*
	3	* mm/debug.c
	4	*
	5	* mm/ specific debug routines.
	6	*
	7	*/
	8
82742a3a SL	9	#include <linux/kernel.h>
82742a3a SL	10	#include <linux/mm.h>
af658dca	11	#include <linux/trace_events.h>
82742a3a	12	#include <linux/memcontrol.h>
420adbe9	13	#include <trace/events/mmflags.h>
7cd12b4a	14	#include <linux/migrate.h>
4e462112	15	#include <linux/page_owner.h>
f682a97a	16	#include <linux/ctype.h>
82742a3a	17
edf14cdb VB	18	#include "internal.h"
edf14cdb VB	19
9a2f45ff	20	const char *migrate_reason_names[MR_TYPES] = {
7cd12b4a VB	21	"compaction",
	22	"memory_failure",
	23	"memory_hotplug",
	24	"syscall_or_cpuset",
	25	"mempolicy_mbind",
	26	"numa_misplaced",
	27	"cma",
	28	};
	29
edf14cdb VB	30	const struct trace_print_flags pageflag_names[] = {
	31	__def_pageflag_names,
	32	{0, NULL}
	33	};
	34
	35	const struct trace_print_flags gfpflag_names[] = {
	36	__def_gfpflag_names,
	37	{0, NULL}
420adbe9 VB	38	};
420adbe9 VB	39
edf14cdb VB	40	const struct trace_print_flags vmaflag_names[] = {
	41	__def_vmaflag_names,
	42	{0, NULL}
82742a3a SL	43	};
82742a3a SL	44
ff8e8116	45	void __dump_page(struct page page, const char reason)
82742a3a	46	{
6197ab98	47	struct page *head = compound_head(page);
311ade0e	48	struct address_space *mapping;
fc36def9	49	bool page_poisoned = PagePoisoned(page);
6197ab98	50	bool compound = PageCompound(page);
4a55c047 QC	51	/*
	52	* Accessing the pageblock without the zone lock. It could change to
	53	* "isolate" again in the meantime, but since we are just dumping the
	54	* state for debugging, it should be fine to accept a bit of
	55	* inaccuracy here due to racing.
	56	*/
	57	bool page_cma = is_migrate_cma_page(page);
fc36def9	58	int mapcount;
5b57b8f2	59	char *type = "";
fc36def9 PT	60
	61	/*
	62	* If struct page is poisoned don't access Page*() functions as that
	63	* leads to recursive loop. Page*() check for poisoned pages, and calls
	64	* dump_page() when detected.
	65	*/
	66	if (page_poisoned) {
e0392cf7	67	pr_warn("page:%px is uninitialized and poisoned", page);
fc36def9 PT	68	goto hex_only;
	69	}
	70
6197ab98 MWO	71	if (page < head \|\| (page >= head + MAX_ORDER_NR_PAGES)) {
	72	/* Corrupt page, cannot call page_mapping */
	73	mapping = page->mapping;
	74	head = page;
	75	compound = false;
	76	} else {
	77	mapping = page_mapping(page);
	78	}
311ade0e	79
9996f05e KS	80	/*
	81	* Avoid VM_BUG_ON() in page_mapcount().
	82	* page->_mapcount space in struct page is used by sl[aou]b pages to
	83	* encode own info.
	84	*/
6197ab98 MWO	85	mapcount = PageSlab(head) ? 0 : page_mapcount(page);
	86
	87	if (compound)
dc8fb2f2 JH	88	if (hpage_pincount_available(page)) {
	89	pr_warn("page:%px refcount:%d mapcount:%d mapping:%p "
	90	"index:%#lx head:%px order:%u "
	91	"compound_mapcount:%d compound_pincount:%d\n",
	92	page, page_ref_count(head), mapcount,
	93	mapping, page_to_pgoff(page), head,
	94	compound_order(head), compound_mapcount(page),
	95	compound_pincount(page));
	96	} else {
	97	pr_warn("page:%px refcount:%d mapcount:%d mapping:%p "
	98	"index:%#lx head:%px order:%u "
	99	"compound_mapcount:%d\n",
	100	page, page_ref_count(head), mapcount,
	101	mapping, page_to_pgoff(page), head,
	102	compound_order(head), compound_mapcount(page));
	103	}
76a1850e	104	else
6197ab98	105	pr_warn("page:%px refcount:%d mapcount:%d mapping:%p index:%#lx\n",
76a1850e	106	page, page_ref_count(page), mapcount,
6197ab98	107	mapping, page_to_pgoff(page));
6855ac4a	108	if (PageKsm(page))
5b57b8f2	109	type = "ksm ";
6855ac4a	110	else if (PageAnon(page))
5b57b8f2	111	type = "anon ";
1c6fb1d8	112	else if (mapping) {
002ae705 VB	113	const struct inode *host;
	114	const struct address_space_operations *a_ops;
	115	const struct hlist_node *dentry_first;
	116	const struct dentry *dentry_ptr;
	117	struct dentry dentry;
	118
	119	/*
	120	* mapping can be invalid pointer and we don't want to crash
	121	* accessing it, so probe everything depending on it carefully
	122	*/
	123	if (probe_kernel_read_strict(&host, &mapping->host,
	124	sizeof(struct inode *)) \|\|
	125	probe_kernel_read_strict(&a_ops, &mapping->a_ops,
	126	sizeof(struct address_space_operations *))) {
	127	pr_warn("failed to read mapping->host or a_ops, mapping not a valid kernel address?\n");
	128	goto out_mapping;
	129	}
	130
	131	if (!host) {
	132	pr_warn("mapping->a_ops:%ps\n", a_ops);
	133	goto out_mapping;
	134	}
	135
	136	if (probe_kernel_read_strict(&dentry_first,
	137	&host->i_dentry.first, sizeof(struct hlist_node *))) {
	138	pr_warn("mapping->a_ops:%ps with invalid mapping->host inode address %px\n",
	139	a_ops, host);
	140	goto out_mapping;
	141	}
	142
	143	if (!dentry_first) {
	144	pr_warn("mapping->a_ops:%ps\n", a_ops);
	145	goto out_mapping;
	146	}
	147
	148	dentry_ptr = container_of(dentry_first, struct dentry, d_u.d_alias);
	149	if (probe_kernel_read_strict(&dentry, dentry_ptr,
	150	sizeof(struct dentry))) {
	151	pr_warn("mapping->aops:%ps with invalid mapping->host->i_dentry.first %px\n",
	152	a_ops, dentry_ptr);
	153	} else {
	154	/*
	155	* if dentry is corrupted, the %pd handler may still
	156	* crash, but it's unlikely that we reach here with a
	157	* corrupted struct page
	158	*/
	159	pr_warn("mapping->aops:%ps dentry name:\"%pd\"\n",
	160	a_ops, &dentry);
	161	}
1c6fb1d8	162	}
002ae705	163	out_mapping:
edf14cdb	164	BUILD_BUG_ON(ARRAY_SIZE(pageflag_names) != __NR_PAGEFLAGS + 1);
ff8e8116	165
4a55c047 QC	166	pr_warn("%sflags: %#lx(%pGp)%s\n", type, page->flags, &page->flags,
4a55c047 QC	167	page_cma ? " CMA" : "");
5b57b8f2	168
fc36def9	169	hex_only:
e0392cf7	170	print_hex_dump(KERN_WARNING, "raw: ", DUMP_PREFIX_NONE, 32,
46e8a3a0 VB	171	sizeof(unsigned long), page,
46e8a3a0 VB	172	sizeof(struct page), false);
6197ab98 MWO	173	if (head != page)
	174	print_hex_dump(KERN_WARNING, "head: ", DUMP_PREFIX_NONE, 32,
	175	sizeof(unsigned long), head,
	176	sizeof(struct page), false);
46e8a3a0	177
82742a3a	178	if (reason)
e0392cf7	179	pr_warn("page dumped because: %s\n", reason);
b8eceeb9	180
9edad6ea	181	#ifdef CONFIG_MEMCG
fc36def9	182	if (!page_poisoned && page->mem_cgroup)
e0392cf7	183	pr_warn("page->mem_cgroup:%px\n", page->mem_cgroup);
9edad6ea	184	#endif
82742a3a SL	185	}
	186
	187	void dump_page(struct page page, const char reason)
	188	{
ff8e8116	189	__dump_page(page, reason);
4e462112	190	dump_page_owner(page);
82742a3a SL	191	}
	192	EXPORT_SYMBOL(dump_page);
	193
	194	#ifdef CONFIG_DEBUG_VM
	195
82742a3a SL	196	void dump_vma(const struct vm_area_struct *vma)
82742a3a SL	197	{
152a2d19 MW	198	pr_emerg("vma %px start %px end %px\n"
	199	"next %px prev %px mm %px\n"
	200	"prot %lx anon_vma %px vm_ops %px\n"
	201	"pgoff %lx file %px private_data %px\n"
b8eceeb9	202	"flags: %#lx(%pGv)\n",
82742a3a SL	203	vma, (void )vma->vm_start, (void )vma->vm_end, vma->vm_next,
	204	vma->vm_prev, vma->vm_mm,
	205	(unsigned long)pgprot_val(vma->vm_page_prot),
	206	vma->anon_vma, vma->vm_ops, vma->vm_pgoff,
b8eceeb9 VB	207	vma->vm_file, vma->vm_private_data,
b8eceeb9 VB	208	vma->vm_flags, &vma->vm_flags);
82742a3a SL	209	}
	210	EXPORT_SYMBOL(dump_vma);
	211
31c9afa6 SL	212	void dump_mm(const struct mm_struct *mm)
31c9afa6 SL	213	{
7a9cdebd	214	pr_emerg("mm %px mmap %px seqnum %llu task_size %lu\n"
31c9afa6	215	#ifdef CONFIG_MMU
152a2d19	216	"get_unmapped_area %px\n"
31c9afa6 SL	217	#endif
31c9afa6 SL	218	"mmap_base %lu mmap_legacy_base %lu highest_vm_end %lu\n"
152a2d19	219	"pgd %px mm_users %d mm_count %d pgtables_bytes %lu map_count %d\n"
31c9afa6	220	"hiwater_rss %lx hiwater_vm %lx total_vm %lx locked_vm %lx\n"
70f8a3ca	221	"pinned_vm %llx data_vm %lx exec_vm %lx stack_vm %lx\n"
31c9afa6 SL	222	"start_code %lx end_code %lx start_data %lx end_data %lx\n"
	223	"start_brk %lx brk %lx start_stack %lx\n"
	224	"arg_start %lx arg_end %lx env_start %lx env_end %lx\n"
152a2d19	225	"binfmt %px flags %lx core_state %px\n"
31c9afa6	226	#ifdef CONFIG_AIO
152a2d19	227	"ioctx_table %px\n"
31c9afa6 SL	228	#endif
31c9afa6 SL	229	#ifdef CONFIG_MEMCG
152a2d19	230	"owner %px "
31c9afa6	231	#endif
152a2d19	232	"exe_file %px\n"
31c9afa6	233	#ifdef CONFIG_MMU_NOTIFIER
984cfe4e	234	"notifier_subscriptions %px\n"
31c9afa6 SL	235	#endif
	236	#ifdef CONFIG_NUMA_BALANCING
	237	"numa_next_scan %lu numa_scan_offset %lu numa_scan_seq %d\n"
	238	#endif
31c9afa6	239	"tlb_flush_pending %d\n"
b8eceeb9	240	"def_flags: %#lx(%pGv)\n",
31c9afa6	241
7a9cdebd	242	mm, mm->mmap, (long long) mm->vmacache_seqnum, mm->task_size,
31c9afa6 SL	243	#ifdef CONFIG_MMU
	244	mm->get_unmapped_area,
	245	#endif
	246	mm->mmap_base, mm->mmap_legacy_base, mm->highest_vm_end,
	247	mm->pgd, atomic_read(&mm->mm_users),
	248	atomic_read(&mm->mm_count),
af5b0f6a	249	mm_pgtables_bytes(mm),
31c9afa6 SL	250	mm->map_count,
31c9afa6 SL	251	mm->hiwater_rss, mm->hiwater_vm, mm->total_vm, mm->locked_vm,
44dc1b1f	252	(u64)atomic64_read(&mm->pinned_vm),
70f8a3ca	253	mm->data_vm, mm->exec_vm, mm->stack_vm,
31c9afa6 SL	254	mm->start_code, mm->end_code, mm->start_data, mm->end_data,
	255	mm->start_brk, mm->brk, mm->start_stack,
	256	mm->arg_start, mm->arg_end, mm->env_start, mm->env_end,
	257	mm->binfmt, mm->flags, mm->core_state,
	258	#ifdef CONFIG_AIO
	259	mm->ioctx_table,
	260	#endif
	261	#ifdef CONFIG_MEMCG
	262	mm->owner,
	263	#endif
	264	mm->exe_file,
	265	#ifdef CONFIG_MMU_NOTIFIER
984cfe4e	266	mm->notifier_subscriptions,
31c9afa6 SL	267	#endif
	268	#ifdef CONFIG_NUMA_BALANCING
	269	mm->numa_next_scan, mm->numa_scan_offset, mm->numa_scan_seq,
	270	#endif
16af97dc	271	atomic_read(&mm->tlb_flush_pending),
b8eceeb9 VB	272	mm->def_flags, &mm->def_flags
b8eceeb9 VB	273	);
31c9afa6 SL	274	}
31c9afa6 SL	275
f682a97a AD	276	static bool page_init_poisoning __read_mostly = true;
	277
	278	static int __init setup_vm_debug(char *str)
	279	{
	280	bool __page_init_poisoning = true;
	281
	282	/*
	283	* Calling vm_debug with no arguments is equivalent to requesting
	284	* to enable all debugging options we can control.
	285	*/
	286	if (str++ != '=' \|\| !str)
	287	goto out;
	288
	289	__page_init_poisoning = false;
	290	if (*str == '-')
	291	goto out;
	292
	293	while (*str) {
	294	switch (tolower(*str)) {
	295	case'p':
	296	__page_init_poisoning = true;
	297	break;
	298	default:
	299	pr_err("vm_debug option '%c' unknown. skipped\n",
	300	*str);
	301	}
	302
	303	str++;
	304	}
	305	out:
	306	if (page_init_poisoning && !__page_init_poisoning)
	307	pr_warn("Page struct poisoning disabled by kernel command line option 'vm_debug'\n");
	308
	309	page_init_poisoning = __page_init_poisoning;
	310
	311	return 1;
	312	}
	313	__setup("vm_debug", setup_vm_debug);
	314
	315	void page_init_poison(struct page *page, size_t size)
	316	{
	317	if (page_init_poisoning)
	318	memset(page, PAGE_POISON_PATTERN, size);
	319	}
	320	EXPORT_SYMBOL_GPL(page_init_poison);
82742a3a	321	#endif /* CONFIG_DEBUG_VM */