[mirror_ubuntu-jammy-kernel.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",
	"contig_range",
	"longterm_pin",
	"demotion",
};

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}
};

static void __dump_page(struct page *page)
{
	struct page *head = compound_head(page);
	struct address_space *mapping;
	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 (page < head || (page >= head + MAX_ORDER_NR_PAGES)) {
		/*
		 * Corrupt page, so we cannot call page_mapping. Instead, do a
		 * safe subset of the steps that page_mapping() does. Caution:
		 * this will be misleading for tail pages, PageSwapCache pages,
		 * and potentially other situations. (See the page_mapping()
		 * implementation for what's missing here.)
		 */
		unsigned long tmp = (unsigned long)page->mapping;

		if (tmp & PAGE_MAPPING_ANON)
			mapping = NULL;
		else
			mapping = (void *)(tmp & ~PAGE_MAPPING_FLAGS);
		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);

	pr_warn("page:%p refcount:%d mapcount:%d mapping:%p index:%#lx pfn:%#lx\n",
			page, page_ref_count(head), mapcount, mapping,
			page_to_pgoff(page), page_to_pfn(page));
	if (compound) {
		if (hpage_pincount_available(page)) {
			pr_warn("head:%p order:%u compound_mapcount:%d compound_pincount:%d\n",
					head, compound_order(head),
					head_compound_mapcount(head),
					head_compound_pincount(head));
		} else {
			pr_warn("head:%p order:%u compound_mapcount:%d\n",
					head, compound_order(head),
					head_compound_mapcount(head));
		}
	}

#ifdef CONFIG_MEMCG
	if (head->memcg_data)
		pr_warn("memcg:%lx\n", head->memcg_data);
#endif
	if (PageKsm(page))
		type = "ksm ";
	else if (PageAnon(page))
		type = "anon ";
	else if (mapping) {
		struct inode *host;
		const struct address_space_operations *a_ops;
		struct hlist_node *dentry_first;
		struct dentry *dentry_ptr;
		struct dentry dentry;
		unsigned long ino;

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

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

		if (get_kernel_nofault(dentry_first, &host->i_dentry.first) ||
		    get_kernel_nofault(ino, &host->i_ino)) {
			pr_warn("aops:%ps with invalid host inode %px\n",
					a_ops, host);
			goto out_mapping;
		}

		if (!dentry_first) {
			pr_warn("aops:%ps ino:%lx\n", a_ops, ino);
			goto out_mapping;
		}

		dentry_ptr = container_of(dentry_first, struct dentry, d_u.d_alias);
		if (get_kernel_nofault(dentry, dentry_ptr)) {
			pr_warn("aops:%ps ino:%lx with invalid dentry %px\n",
					a_ops, ino, 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("aops:%ps ino:%lx dentry name:\"%pd\"\n",
					a_ops, ino, &dentry);
		}
	}
out_mapping:
	BUILD_BUG_ON(ARRAY_SIZE(pageflag_names) != __NR_PAGEFLAGS + 1);

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

void dump_page(struct page *page, const char *reason)
{
	if (PagePoisoned(page))
		pr_warn("page:%p is uninitialized and poisoned", page);
	else
		__dump_page(page);
	if (reason)
		pr_warn("page dumped because: %s\n", 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",
a4ce7391 WO	27	"contig_range",
a4ce7391 WO	28	"longterm_pin",
57ed7b43	29	"demotion",
7cd12b4a VB	30	};
7cd12b4a VB	31
edf14cdb VB	32	const struct trace_print_flags pageflag_names[] = {
	33	__def_pageflag_names,
	34	{0, NULL}
	35	};
	36
	37	const struct trace_print_flags gfpflag_names[] = {
	38	__def_gfpflag_names,
	39	{0, NULL}
420adbe9 VB	40	};
420adbe9 VB	41
edf14cdb VB	42	const struct trace_print_flags vmaflag_names[] = {
	43	__def_vmaflag_names,
	44	{0, NULL}
82742a3a SL	45	};
82742a3a SL	46
be7c701f	47	static void __dump_page(struct page *page)
82742a3a	48	{
6197ab98	49	struct page *head = compound_head(page);
311ade0e	50	struct address_space *mapping;
6197ab98	51	bool compound = PageCompound(page);
4a55c047 QC	52	/*
	53	* Accessing the pageblock without the zone lock. It could change to
	54	* "isolate" again in the meantime, but since we are just dumping the
	55	* state for debugging, it should be fine to accept a bit of
	56	* inaccuracy here due to racing.
	57	*/
	58	bool page_cma = is_migrate_cma_page(page);
fc36def9	59	int mapcount;
5b57b8f2	60	char *type = "";
fc36def9	61
6197ab98	62	if (page < head \|\| (page >= head + MAX_ORDER_NR_PAGES)) {
e1ab96f8 MWO	63	/*
	64	* Corrupt page, so we cannot call page_mapping. Instead, do a
	65	* safe subset of the steps that page_mapping() does. Caution:
	66	* this will be misleading for tail pages, PageSwapCache pages,
	67	* and potentially other situations. (See the page_mapping()
	68	* implementation for what's missing here.)
	69	*/
	70	unsigned long tmp = (unsigned long)page->mapping;
	71
	72	if (tmp & PAGE_MAPPING_ANON)
	73	mapping = NULL;
	74	else
	75	mapping = (void *)(tmp & ~PAGE_MAPPING_FLAGS);
6197ab98 MWO	76	head = page;
	77	compound = false;
	78	} else {
	79	mapping = page_mapping(page);
	80	}
311ade0e	81
9996f05e KS	82	/*
	83	* Avoid VM_BUG_ON() in page_mapcount().
	84	* page->_mapcount space in struct page is used by sl[aou]b pages to
	85	* encode own info.
	86	*/
6197ab98 MWO	87	mapcount = PageSlab(head) ? 0 : page_mapcount(page);
6197ab98 MWO	88
54a75157	89	pr_warn("page:%p refcount:%d mapcount:%d mapping:%p index:%#lx pfn:%#lx\n",
452b557c	90	page, page_ref_count(head), mapcount, mapping,
54a75157	91	page_to_pgoff(page), page_to_pfn(page));
452b557c	92	if (compound) {
dc8fb2f2	93	if (hpage_pincount_available(page)) {
54a75157	94	pr_warn("head:%p order:%u compound_mapcount:%d compound_pincount:%d\n",
452b557c	95	head, compound_order(head),
bac3cf4d JH	96	head_compound_mapcount(head),
bac3cf4d JH	97	head_compound_pincount(head));
dc8fb2f2	98	} else {
54a75157	99	pr_warn("head:%p order:%u compound_mapcount:%d\n",
452b557c	100	head, compound_order(head),
bac3cf4d	101	head_compound_mapcount(head));
dc8fb2f2	102	}
452b557c	103	}
91f5345a MWO	104
	105	#ifdef CONFIG_MEMCG
	106	if (head->memcg_data)
	107	pr_warn("memcg:%lx\n", head->memcg_data);
	108	#endif
6855ac4a	109	if (PageKsm(page))
5b57b8f2	110	type = "ksm ";
6855ac4a	111	else if (PageAnon(page))
5b57b8f2	112	type = "anon ";
1c6fb1d8	113	else if (mapping) {
9ad38265	114	struct inode *host;
002ae705	115	const struct address_space_operations *a_ops;
9ad38265 MWO	116	struct hlist_node *dentry_first;
9ad38265 MWO	117	struct dentry *dentry_ptr;
002ae705	118	struct dentry dentry;
853322a6	119	unsigned long ino;
002ae705 VB	120
	121	/*
	122	* mapping can be invalid pointer and we don't want to crash
	123	* accessing it, so probe everything depending on it carefully
	124	*/
9ad38265 MWO	125	if (get_kernel_nofault(host, &mapping->host) \|\|
	126	get_kernel_nofault(a_ops, &mapping->a_ops)) {
	127	pr_warn("failed to read mapping contents, not a valid kernel address?\n");
002ae705 VB	128	goto out_mapping;
	129	}
	130
	131	if (!host) {
9ad38265	132	pr_warn("aops:%ps\n", a_ops);
002ae705 VB	133	goto out_mapping;
	134	}
	135
853322a6 MWO	136	if (get_kernel_nofault(dentry_first, &host->i_dentry.first) \|\|
853322a6 MWO	137	get_kernel_nofault(ino, &host->i_ino)) {
9ad38265 MWO	138	pr_warn("aops:%ps with invalid host inode %px\n",
9ad38265 MWO	139	a_ops, host);
002ae705 VB	140	goto out_mapping;
	141	}
	142
	143	if (!dentry_first) {
853322a6	144	pr_warn("aops:%ps ino:%lx\n", a_ops, ino);
002ae705 VB	145	goto out_mapping;
	146	}
	147
	148	dentry_ptr = container_of(dentry_first, struct dentry, d_u.d_alias);
9ad38265	149	if (get_kernel_nofault(dentry, dentry_ptr)) {
853322a6 MWO	150	pr_warn("aops:%ps ino:%lx with invalid dentry %px\n",
853322a6 MWO	151	a_ops, ino, dentry_ptr);
002ae705 VB	152	} else {
	153	/*
	154	* if dentry is corrupted, the %pd handler may still
	155	* crash, but it's unlikely that we reach here with a
	156	* corrupted struct page
	157	*/
9bdaf2cc	158	pr_warn("aops:%ps ino:%lx dentry name:\"%pd\"\n",
853322a6	159	a_ops, ino, &dentry);
002ae705	160	}
1c6fb1d8	161	}
002ae705	162	out_mapping:
edf14cdb	163	BUILD_BUG_ON(ARRAY_SIZE(pageflag_names) != __NR_PAGEFLAGS + 1);
ff8e8116	164
0b93d59e	165	pr_warn("%sflags: %#lx(%pGp)%s\n", type, head->flags, &head->flags,
4a55c047	166	page_cma ? " CMA" : "");
e0392cf7	167	print_hex_dump(KERN_WARNING, "raw: ", DUMP_PREFIX_NONE, 32,
46e8a3a0 VB	168	sizeof(unsigned long), page,
46e8a3a0 VB	169	sizeof(struct page), false);
6197ab98 MWO	170	if (head != page)
	171	print_hex_dump(KERN_WARNING, "head: ", DUMP_PREFIX_NONE, 32,
	172	sizeof(unsigned long), head,
	173	sizeof(struct page), false);
82742a3a SL	174	}
	175
	176	void dump_page(struct page page, const char reason)
	177	{
be7c701f MWO	178	if (PagePoisoned(page))
	179	pr_warn("page:%p is uninitialized and poisoned", page);
	180	else
	181	__dump_page(page);
	182	if (reason)
	183	pr_warn("page dumped because: %s\n", reason);
4e462112	184	dump_page_owner(page);
82742a3a SL	185	}
	186	EXPORT_SYMBOL(dump_page);
	187
	188	#ifdef CONFIG_DEBUG_VM
	189
82742a3a SL	190	void dump_vma(const struct vm_area_struct *vma)
82742a3a SL	191	{
152a2d19 MW	192	pr_emerg("vma %px start %px end %px\n"
	193	"next %px prev %px mm %px\n"
	194	"prot %lx anon_vma %px vm_ops %px\n"
	195	"pgoff %lx file %px private_data %px\n"
b8eceeb9	196	"flags: %#lx(%pGv)\n",
82742a3a SL	197	vma, (void )vma->vm_start, (void )vma->vm_end, vma->vm_next,
	198	vma->vm_prev, vma->vm_mm,
	199	(unsigned long)pgprot_val(vma->vm_page_prot),
	200	vma->anon_vma, vma->vm_ops, vma->vm_pgoff,
b8eceeb9 VB	201	vma->vm_file, vma->vm_private_data,
b8eceeb9 VB	202	vma->vm_flags, &vma->vm_flags);
82742a3a SL	203	}
	204	EXPORT_SYMBOL(dump_vma);
	205
31c9afa6 SL	206	void dump_mm(const struct mm_struct *mm)
31c9afa6 SL	207	{
7a9cdebd	208	pr_emerg("mm %px mmap %px seqnum %llu task_size %lu\n"
31c9afa6	209	#ifdef CONFIG_MMU
152a2d19	210	"get_unmapped_area %px\n"
31c9afa6 SL	211	#endif
31c9afa6 SL	212	"mmap_base %lu mmap_legacy_base %lu highest_vm_end %lu\n"
152a2d19	213	"pgd %px mm_users %d mm_count %d pgtables_bytes %lu map_count %d\n"
31c9afa6	214	"hiwater_rss %lx hiwater_vm %lx total_vm %lx locked_vm %lx\n"
70f8a3ca	215	"pinned_vm %llx data_vm %lx exec_vm %lx stack_vm %lx\n"
31c9afa6 SL	216	"start_code %lx end_code %lx start_data %lx end_data %lx\n"
	217	"start_brk %lx brk %lx start_stack %lx\n"
	218	"arg_start %lx arg_end %lx env_start %lx env_end %lx\n"
152a2d19	219	"binfmt %px flags %lx core_state %px\n"
31c9afa6	220	#ifdef CONFIG_AIO
152a2d19	221	"ioctx_table %px\n"
31c9afa6 SL	222	#endif
31c9afa6 SL	223	#ifdef CONFIG_MEMCG
152a2d19	224	"owner %px "
31c9afa6	225	#endif
152a2d19	226	"exe_file %px\n"
31c9afa6	227	#ifdef CONFIG_MMU_NOTIFIER
984cfe4e	228	"notifier_subscriptions %px\n"
31c9afa6 SL	229	#endif
	230	#ifdef CONFIG_NUMA_BALANCING
	231	"numa_next_scan %lu numa_scan_offset %lu numa_scan_seq %d\n"
	232	#endif
31c9afa6	233	"tlb_flush_pending %d\n"
b8eceeb9	234	"def_flags: %#lx(%pGv)\n",
31c9afa6	235
7a9cdebd	236	mm, mm->mmap, (long long) mm->vmacache_seqnum, mm->task_size,
31c9afa6 SL	237	#ifdef CONFIG_MMU
	238	mm->get_unmapped_area,
	239	#endif
	240	mm->mmap_base, mm->mmap_legacy_base, mm->highest_vm_end,
	241	mm->pgd, atomic_read(&mm->mm_users),
	242	atomic_read(&mm->mm_count),
af5b0f6a	243	mm_pgtables_bytes(mm),
31c9afa6 SL	244	mm->map_count,
31c9afa6 SL	245	mm->hiwater_rss, mm->hiwater_vm, mm->total_vm, mm->locked_vm,
44dc1b1f	246	(u64)atomic64_read(&mm->pinned_vm),
70f8a3ca	247	mm->data_vm, mm->exec_vm, mm->stack_vm,
31c9afa6 SL	248	mm->start_code, mm->end_code, mm->start_data, mm->end_data,
	249	mm->start_brk, mm->brk, mm->start_stack,
	250	mm->arg_start, mm->arg_end, mm->env_start, mm->env_end,
	251	mm->binfmt, mm->flags, mm->core_state,
	252	#ifdef CONFIG_AIO
	253	mm->ioctx_table,
	254	#endif
	255	#ifdef CONFIG_MEMCG
	256	mm->owner,
	257	#endif
	258	mm->exe_file,
	259	#ifdef CONFIG_MMU_NOTIFIER
984cfe4e	260	mm->notifier_subscriptions,
31c9afa6 SL	261	#endif
	262	#ifdef CONFIG_NUMA_BALANCING
	263	mm->numa_next_scan, mm->numa_scan_offset, mm->numa_scan_seq,
	264	#endif
16af97dc	265	atomic_read(&mm->tlb_flush_pending),
b8eceeb9 VB	266	mm->def_flags, &mm->def_flags
b8eceeb9 VB	267	);
31c9afa6 SL	268	}
31c9afa6 SL	269
f682a97a AD	270	static bool page_init_poisoning __read_mostly = true;
	271
	272	static int __init setup_vm_debug(char *str)
	273	{
	274	bool __page_init_poisoning = true;
	275
	276	/*
	277	* Calling vm_debug with no arguments is equivalent to requesting
	278	* to enable all debugging options we can control.
	279	*/
	280	if (str++ != '=' \|\| !str)
	281	goto out;
	282
	283	__page_init_poisoning = false;
	284	if (*str == '-')
	285	goto out;
	286
	287	while (*str) {
	288	switch (tolower(*str)) {
	289	case'p':
	290	__page_init_poisoning = true;
	291	break;
	292	default:
	293	pr_err("vm_debug option '%c' unknown. skipped\n",
	294	*str);
	295	}
	296
	297	str++;
	298	}
	299	out:
	300	if (page_init_poisoning && !__page_init_poisoning)
	301	pr_warn("Page struct poisoning disabled by kernel command line option 'vm_debug'\n");
	302
	303	page_init_poisoning = __page_init_poisoning;
	304
	305	return 1;
	306	}
	307	__setup("vm_debug", setup_vm_debug);
	308
	309	void page_init_poison(struct page *page, size_t size)
	310	{
	311	if (page_init_poisoning)
	312	memset(page, PAGE_POISON_PATTERN, size);
	313	}
	314	EXPORT_SYMBOL_GPL(page_init_poison);
82742a3a	315	#endif /* CONFIG_DEBUG_VM */