kcore.c

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 *	fs/proc/kcore.c kernel ELF core dumper
  4 *
  5 *	Modelled on fs/exec.c:aout_core_dump()
  6 *	Jeremy Fitzhardinge <jeremy@sw.oz.au>
  7 *	ELF version written by David Howells <David.Howells@nexor.co.uk>
  8 *	Modified and incorporated into 2.3.x by Tigran Aivazian <tigran@veritas.com>
  9 *	Support to dump vmalloc'd areas (ELF only), Tigran Aivazian <tigran@veritas.com>
 10 *	Safe accesses to vmalloc/direct-mapped discontiguous areas, Kanoj Sarcar <kanoj@sgi.com>
 11 */
 12
 13#include <linux/vmcore_info.h>
 14#include <linux/mm.h>
 15#include <linux/proc_fs.h>
 16#include <linux/kcore.h>
 17#include <linux/user.h>
 18#include <linux/capability.h>
 19#include <linux/elf.h>
 20#include <linux/elfcore.h>
 21#include <linux/vmalloc.h>
 22#include <linux/highmem.h>
 23#include <linux/printk.h>
 24#include <linux/memblock.h>
 25#include <linux/init.h>
 26#include <linux/slab.h>
 27#include <linux/uio.h>
 28#include <asm/io.h>
 29#include <linux/list.h>
 30#include <linux/ioport.h>
 31#include <linux/memory.h>
 32#include <linux/sched/task.h>
 33#include <linux/security.h>
 34#include <asm/sections.h>
 35#include "internal.h"
 36
 37#ifndef ELF_CORE_EFLAGS
 38#define ELF_CORE_EFLAGS	0
 39#endif
 40
 41static struct proc_dir_entry *proc_root_kcore;
 42
 43
 44#ifndef kc_vaddr_to_offset
 45#define	kc_vaddr_to_offset(v) ((v) - PAGE_OFFSET)
 46#endif
 47#ifndef	kc_offset_to_vaddr
 48#define	kc_offset_to_vaddr(o) ((o) + PAGE_OFFSET)
 49#endif
 50
 51#ifndef kc_xlate_dev_mem_ptr
 52#define kc_xlate_dev_mem_ptr kc_xlate_dev_mem_ptr
 53static inline void *kc_xlate_dev_mem_ptr(phys_addr_t phys)
 54{
 55	return __va(phys);
 56}
 57#endif
 58#ifndef kc_unxlate_dev_mem_ptr
 59#define kc_unxlate_dev_mem_ptr kc_unxlate_dev_mem_ptr
 60static inline void kc_unxlate_dev_mem_ptr(phys_addr_t phys, void *virt)
 61{
 62}
 63#endif
 64
 65static LIST_HEAD(kclist_head);
 66static int kcore_nphdr;
 67static size_t kcore_phdrs_len;
 68static size_t kcore_notes_len;
 69static size_t kcore_data_offset;
 70DEFINE_STATIC_PERCPU_RWSEM(kclist_lock);
 71static int kcore_need_update = 1;
 72
 73/*
 74 * Returns > 0 for RAM pages, 0 for non-RAM pages, < 0 on error
 75 * Same as oldmem_pfn_is_ram in vmcore
 76 */
 77static int (*mem_pfn_is_ram)(unsigned long pfn);
 78
 79int __init register_mem_pfn_is_ram(int (*fn)(unsigned long pfn))
 80{
 81	if (mem_pfn_is_ram)
 82		return -EBUSY;
 83	mem_pfn_is_ram = fn;
 84	return 0;
 85}
 86
 87static int pfn_is_ram(unsigned long pfn)
 88{
 89	if (mem_pfn_is_ram)
 90		return mem_pfn_is_ram(pfn);
 91	else
 92		return 1;
 93}
 94
 95/* This doesn't grab kclist_lock, so it should only be used at init time. */
 96void __init kclist_add(struct kcore_list *new, void *addr, size_t size,
 97		       int type)
 98{
 99	new->addr = (unsigned long)addr;
100	new->size = size;
101	new->type = type;
102
103	list_add_tail(&new->list, &kclist_head);
104}
105
106static void update_kcore_size(void)
107{
108	size_t try, size;
109	struct kcore_list *m;
110
111	kcore_nphdr = 1; /* PT_NOTE */
112	size = 0;
113
114	list_for_each_entry(m, &kclist_head, list) {
115		try = kc_vaddr_to_offset((size_t)m->addr + m->size);
116		if (try > size)
117			size = try;
118		kcore_nphdr++;
119	}
120
121	kcore_phdrs_len = kcore_nphdr * sizeof(struct elf_phdr);
122	kcore_notes_len = (4 * sizeof(struct elf_note) +
123			   ALIGN(sizeof(NN_PRSTATUS), 4) +
124			   ALIGN(sizeof(NN_PRPSINFO), 4) +
125			   ALIGN(sizeof(NN_TASKSTRUCT), 4) +
126			   VMCOREINFO_NOTE_NAME_BYTES +
127			   ALIGN(sizeof(struct elf_prstatus), 4) +
128			   ALIGN(sizeof(struct elf_prpsinfo), 4) +
129			   ALIGN(arch_task_struct_size, 4) +
130			   ALIGN(vmcoreinfo_size, 4));
131	kcore_data_offset = PAGE_ALIGN(sizeof(struct elfhdr) + kcore_phdrs_len +
132				       kcore_notes_len);
133	proc_root_kcore->size = kcore_data_offset + size;
134}
135
136#ifdef CONFIG_HIGHMEM
137/*
138 * If no highmem, we can assume [0...max_low_pfn) continuous range of memory
139 * because memory hole is not as big as !HIGHMEM case.
140 * (HIGHMEM is special because part of memory is _invisible_ from the kernel.)
141 */
142static int kcore_ram_list(struct list_head *head)
143{
144	struct kcore_list *ent;
145
146	ent = kmalloc(sizeof(*ent), GFP_KERNEL);
147	if (!ent)
148		return -ENOMEM;
149	ent->addr = (unsigned long)__va(0);
150	ent->size = max_low_pfn << PAGE_SHIFT;
151	ent->type = KCORE_RAM;
152	list_add(&ent->list, head);
153	return 0;
154}
155
156#else /* !CONFIG_HIGHMEM */
157
158#ifdef CONFIG_SPARSEMEM_VMEMMAP
159/* calculate vmemmap's address from given system ram pfn and register it */
160static int
161get_sparsemem_vmemmap_info(struct kcore_list *ent, struct list_head *head)
162{
163	unsigned long pfn = __pa(ent->addr) >> PAGE_SHIFT;
164	unsigned long nr_pages = ent->size >> PAGE_SHIFT;
165	unsigned long start, end;
166	struct kcore_list *vmm, *tmp;
167
168
169	start = ((unsigned long)pfn_to_page(pfn)) & PAGE_MASK;
170	end = ((unsigned long)pfn_to_page(pfn + nr_pages)) - 1;
171	end = PAGE_ALIGN(end);
172	/* overlap check (because we have to align page */
173	list_for_each_entry(tmp, head, list) {
174		if (tmp->type != KCORE_VMEMMAP)
175			continue;
176		if (start < tmp->addr + tmp->size)
177			if (end > tmp->addr)
178				end = tmp->addr;
179	}
180	if (start < end) {
181		vmm = kmalloc(sizeof(*vmm), GFP_KERNEL);
182		if (!vmm)
183			return 0;
184		vmm->addr = start;
185		vmm->size = end - start;
186		vmm->type = KCORE_VMEMMAP;
187		list_add_tail(&vmm->list, head);
188	}
189	return 1;
190
191}
192#else
193static int
194get_sparsemem_vmemmap_info(struct kcore_list *ent, struct list_head *head)
195{
196	return 1;
197}
198
199#endif
200
201static int
202kclist_add_private(unsigned long pfn, unsigned long nr_pages, void *arg)
203{
204	struct list_head *head = (struct list_head *)arg;
205	struct kcore_list *ent;
206	struct page *p;
207
208	if (!pfn_valid(pfn))
209		return 1;
210
211	p = pfn_to_page(pfn);
212
213	ent = kmalloc(sizeof(*ent), GFP_KERNEL);
214	if (!ent)
215		return -ENOMEM;
216	ent->addr = (unsigned long)page_to_virt(p);
217	ent->size = nr_pages << PAGE_SHIFT;
218
219	if (!virt_addr_valid((void *)ent->addr))
220		goto free_out;
221
222	/* cut not-mapped area. ....from ppc-32 code. */
223	if (ULONG_MAX - ent->addr < ent->size)
224		ent->size = ULONG_MAX - ent->addr;
225
226	/*
227	 * We've already checked virt_addr_valid so we know this address
228	 * is a valid pointer, therefore we can check against it to determine
229	 * if we need to trim
230	 */
231	if (VMALLOC_START > ent->addr) {
232		if (VMALLOC_START - ent->addr < ent->size)
233			ent->size = VMALLOC_START - ent->addr;
234	}
235
236	ent->type = KCORE_RAM;
237	list_add_tail(&ent->list, head);
238
239	if (!get_sparsemem_vmemmap_info(ent, head)) {
240		list_del(&ent->list);
241		goto free_out;
242	}
243
244	return 0;
245free_out:
246	kfree(ent);
247	return 1;
248}
249
250static int kcore_ram_list(struct list_head *list)
251{
252	int nid, ret;
253	unsigned long end_pfn;
254
255	/* Not initialized....update now */
256	/* find out "max pfn" */
257	end_pfn = 0;
258	for_each_node_state(nid, N_MEMORY) {
259		unsigned long node_end;
260		node_end = node_end_pfn(nid);
261		if (end_pfn < node_end)
262			end_pfn = node_end;
263	}
264	/* scan 0 to max_pfn */
265	ret = walk_system_ram_range(0, end_pfn, list, kclist_add_private);
266	if (ret)
267		return -ENOMEM;
268	return 0;
269}
270#endif /* CONFIG_HIGHMEM */
271
272static int kcore_update_ram(void)
273{
274	LIST_HEAD(list);
275	LIST_HEAD(garbage);
276	struct kcore_list *tmp, *pos;
277	int ret = 0;
278
279	percpu_down_write(&kclist_lock);
280	if (!xchg(&kcore_need_update, 0))
281		goto out;
282
283	ret = kcore_ram_list(&list);
284	if (ret) {
285		/* Couldn't get the RAM list, try again next time. */
286		WRITE_ONCE(kcore_need_update, 1);
287		list_splice_tail(&list, &garbage);
288		goto out;
289	}
290
291	list_for_each_entry_safe(pos, tmp, &kclist_head, list) {
292		if (pos->type == KCORE_RAM || pos->type == KCORE_VMEMMAP)
293			list_move(&pos->list, &garbage);
294	}
295	list_splice_tail(&list, &kclist_head);
296
297	update_kcore_size();
298
299out:
300	percpu_up_write(&kclist_lock);
301	list_for_each_entry_safe(pos, tmp, &garbage, list) {
302		list_del(&pos->list);
303		kfree(pos);
304	}
305	return ret;
306}
307
308static void append_kcore_note(char *notes, size_t *i, const char *name,
309			      unsigned int type, const void *desc,
310			      size_t descsz)
311{
312	struct elf_note *note = (struct elf_note *)&notes[*i];
313
314	note->n_namesz = strlen(name) + 1;
315	note->n_descsz = descsz;
316	note->n_type = type;
317	*i += sizeof(*note);
318	memcpy(&notes[*i], name, note->n_namesz);
319	*i = ALIGN(*i + note->n_namesz, 4);
320	memcpy(&notes[*i], desc, descsz);
321	*i = ALIGN(*i + descsz, 4);
322}
323
324static ssize_t read_kcore_iter(struct kiocb *iocb, struct iov_iter *iter)
325{
326	struct file *file = iocb->ki_filp;
327	char *buf = file->private_data;
328	loff_t *fpos = &iocb->ki_pos;
329	size_t phdrs_offset, notes_offset;
330	size_t page_offline_frozen = 1;
331	struct kcore_list *m;
332	size_t tsz;
333	unsigned long start;
334	size_t buflen = iov_iter_count(iter);
335	size_t orig_buflen = buflen;
336	int ret = 0;
337
338	percpu_down_read(&kclist_lock);
339	/*
340	 * Don't race against drivers that set PageOffline() and expect no
341	 * further page access.
342	 */
343	page_offline_freeze();
344
345	phdrs_offset = sizeof(struct elfhdr);
346	notes_offset = phdrs_offset + kcore_phdrs_len;
347
348	/* ELF file header. */
349	if (buflen && *fpos < sizeof(struct elfhdr)) {
350		struct elfhdr ehdr = {
351			.e_ident = {
352				[EI_MAG0] = ELFMAG0,
353				[EI_MAG1] = ELFMAG1,
354				[EI_MAG2] = ELFMAG2,
355				[EI_MAG3] = ELFMAG3,
356				[EI_CLASS] = ELF_CLASS,
357				[EI_DATA] = ELF_DATA,
358				[EI_VERSION] = EV_CURRENT,
359				[EI_OSABI] = ELF_OSABI,
360			},
361			.e_type = ET_CORE,
362			.e_machine = ELF_ARCH,
363			.e_version = EV_CURRENT,
364			.e_phoff = sizeof(struct elfhdr),
365			.e_flags = ELF_CORE_EFLAGS,
366			.e_ehsize = sizeof(struct elfhdr),
367			.e_phentsize = sizeof(struct elf_phdr),
368			.e_phnum = kcore_nphdr,
369		};
370
371		tsz = min_t(size_t, buflen, sizeof(struct elfhdr) - *fpos);
372		if (copy_to_iter((char *)&ehdr + *fpos, tsz, iter) != tsz) {
373			ret = -EFAULT;
374			goto out;
375		}
376
377		buflen -= tsz;
378		*fpos += tsz;
379	}
380
381	/* ELF program headers. */
382	if (buflen && *fpos < phdrs_offset + kcore_phdrs_len) {
383		struct elf_phdr *phdrs, *phdr;
384
385		phdrs = kzalloc(kcore_phdrs_len, GFP_KERNEL);
386		if (!phdrs) {
387			ret = -ENOMEM;
388			goto out;
389		}
390
391		phdrs[0].p_type = PT_NOTE;
392		phdrs[0].p_offset = notes_offset;
393		phdrs[0].p_filesz = kcore_notes_len;
394
395		phdr = &phdrs[1];
396		list_for_each_entry(m, &kclist_head, list) {
397			phdr->p_type = PT_LOAD;
398			phdr->p_flags = PF_R | PF_W | PF_X;
399			phdr->p_offset = kc_vaddr_to_offset(m->addr)
400					 + kcore_data_offset;
401			phdr->p_vaddr = (size_t)m->addr;
402			if (m->type == KCORE_RAM)
403				phdr->p_paddr = __pa(m->addr);
404			else if (m->type == KCORE_TEXT)
405				phdr->p_paddr = __pa_symbol(m->addr);
406			else
407				phdr->p_paddr = (elf_addr_t)-1;
408			phdr->p_filesz = phdr->p_memsz = m->size;
409			phdr->p_align = PAGE_SIZE;
410			phdr++;
411		}
412
413		tsz = min_t(size_t, buflen,
414			    phdrs_offset + kcore_phdrs_len - *fpos);
415		if (copy_to_iter((char *)phdrs + *fpos - phdrs_offset, tsz,
416				 iter) != tsz) {
417			kfree(phdrs);
418			ret = -EFAULT;
419			goto out;
420		}
421		kfree(phdrs);
422
423		buflen -= tsz;
424		*fpos += tsz;
425	}
426
427	/* ELF note segment. */
428	if (buflen && *fpos < notes_offset + kcore_notes_len) {
429		struct elf_prstatus prstatus = {};
430		struct elf_prpsinfo prpsinfo = {
431			.pr_sname = 'R',
432			.pr_fname = "vmlinux",
433		};
434		char *notes;
435		size_t i = 0;
436
437		strscpy(prpsinfo.pr_psargs, saved_command_line,
438			sizeof(prpsinfo.pr_psargs));
439
440		notes = kzalloc(kcore_notes_len, GFP_KERNEL);
441		if (!notes) {
442			ret = -ENOMEM;
443			goto out;
444		}
445
446		append_kcore_note(notes, &i, NN_PRSTATUS, NT_PRSTATUS, &prstatus,
447				  sizeof(prstatus));
448		append_kcore_note(notes, &i, NN_PRPSINFO, NT_PRPSINFO, &prpsinfo,
449				  sizeof(prpsinfo));
450		append_kcore_note(notes, &i, NN_TASKSTRUCT, NT_TASKSTRUCT, current,
451				  arch_task_struct_size);
452		/*
453		 * vmcoreinfo_size is mostly constant after init time, but it
454		 * can be changed by crash_save_vmcoreinfo(). Racing here with a
455		 * panic on another CPU before the machine goes down is insanely
456		 * unlikely, but it's better to not leave potential buffer
457		 * overflows lying around, regardless.
458		 */
459		append_kcore_note(notes, &i, VMCOREINFO_NOTE_NAME, 0,
460				  vmcoreinfo_data,
461				  min(vmcoreinfo_size, kcore_notes_len - i));
462
463		tsz = min_t(size_t, buflen,
464			    notes_offset + kcore_notes_len - *fpos);
465		if (copy_to_iter(notes + *fpos - notes_offset, tsz, iter) != tsz) {
466			kfree(notes);
467			ret = -EFAULT;
468			goto out;
469		}
470		kfree(notes);
471
472		buflen -= tsz;
473		*fpos += tsz;
474	}
475
476	/*
477	 * Check to see if our file offset matches with any of
478	 * the addresses in the elf_phdr on our list.
479	 */
480	start = kc_offset_to_vaddr(*fpos - kcore_data_offset);
481	if ((tsz = (PAGE_SIZE - (start & ~PAGE_MASK))) > buflen)
482		tsz = buflen;
483
484	m = NULL;
485	while (buflen) {
486		struct page *page;
487		unsigned long pfn;
488		phys_addr_t phys;
489		void *__start;
490
491		/*
492		 * If this is the first iteration or the address is not within
493		 * the previous entry, search for a matching entry.
494		 */
495		if (!m || start < m->addr || start >= m->addr + m->size) {
496			struct kcore_list *pos;
497
498			m = NULL;
499			list_for_each_entry(pos, &kclist_head, list) {
500				if (start >= pos->addr &&
501				    start < pos->addr + pos->size) {
502					m = pos;
503					break;
504				}
505			}
506		}
507
508		if (page_offline_frozen++ % MAX_ORDER_NR_PAGES == 0) {
509			page_offline_thaw();
510			cond_resched();
511			page_offline_freeze();
512		}
513
514		if (!m) {
515			if (iov_iter_zero(tsz, iter) != tsz) {
516				ret = -EFAULT;
517				goto out;
518			}
519			goto skip;
520		}
521
522		switch (m->type) {
523		case KCORE_VMALLOC:
524		{
525			const char *src = (char *)start;
526			size_t read = 0, left = tsz;
527
528			/*
529			 * vmalloc uses spinlocks, so we optimistically try to
530			 * read memory. If this fails, fault pages in and try
531			 * again until we are done.
532			 */
533			while (true) {
534				read += vread_iter(iter, src, left);
535				if (read == tsz)
536					break;
537
538				src += read;
539				left -= read;
540
541				if (fault_in_iov_iter_writeable(iter, left)) {
542					ret = -EFAULT;
543					goto out;
544				}
545			}
546			break;
547		}
548		case KCORE_USER:
549			/* User page is handled prior to normal kernel page: */
550			if (copy_to_iter((char *)start, tsz, iter) != tsz) {
551				ret = -EFAULT;
552				goto out;
553			}
554			break;
555		case KCORE_RAM:
556			phys = __pa(start);
557			pfn =  phys >> PAGE_SHIFT;
558			page = pfn_to_online_page(pfn);
559
560			/*
561			 * Don't read offline sections, logically offline pages
562			 * (e.g., inflated in a balloon), hwpoisoned pages,
563			 * and explicitly excluded physical ranges.
564			 */
565			if (!page || PageOffline(page) ||
566			    is_page_hwpoison(page) || !pfn_is_ram(pfn) ||
567			    pfn_is_unaccepted_memory(pfn)) {
568				if (iov_iter_zero(tsz, iter) != tsz) {
569					ret = -EFAULT;
570					goto out;
571				}
572				break;
573			}
574			fallthrough;
575		case KCORE_VMEMMAP:
576		case KCORE_TEXT:
577			if (m->type == KCORE_RAM) {
578				__start = kc_xlate_dev_mem_ptr(phys);
579				if (!__start) {
580					ret = -ENOMEM;
581					if (iov_iter_zero(tsz, iter) != tsz)
582						ret = -EFAULT;
583					goto out;
584				}
585			} else {
586				__start = (void *)start;
587			}
588
589			/*
590			 * Sadly we must use a bounce buffer here to be able to
591			 * make use of copy_from_kernel_nofault(), as these
592			 * memory regions might not always be mapped on all
593			 * architectures.
594			 */
595			ret = copy_from_kernel_nofault(buf, __start, tsz);
596			if (m->type == KCORE_RAM)
597				kc_unxlate_dev_mem_ptr(phys, __start);
598			if (ret) {
599				if (iov_iter_zero(tsz, iter) != tsz) {
600					ret = -EFAULT;
601					goto out;
602				}
603				ret = 0;
604			/*
605			 * We know the bounce buffer is safe to copy from, so
606			 * use _copy_to_iter() directly.
607			 */
608			} else if (_copy_to_iter(buf, tsz, iter) != tsz) {
609				ret = -EFAULT;
610				goto out;
611			}
612			break;
613		default:
614			pr_warn_once("Unhandled KCORE type: %d\n", m->type);
615			if (iov_iter_zero(tsz, iter) != tsz) {
616				ret = -EFAULT;
617				goto out;
618			}
619		}
620skip:
621		buflen -= tsz;
622		*fpos += tsz;
623		start += tsz;
624		tsz = (buflen > PAGE_SIZE ? PAGE_SIZE : buflen);
625	}
626
627out:
628	page_offline_thaw();
629	percpu_up_read(&kclist_lock);
630	if (ret)
631		return ret;
632	return orig_buflen - buflen;
633}
634
635static int open_kcore(struct inode *inode, struct file *filp)
636{
637	int ret = security_locked_down(LOCKDOWN_KCORE);
638
639	if (!capable(CAP_SYS_RAWIO))
640		return -EPERM;
641
642	if (ret)
643		return ret;
644
645	filp->private_data = kmalloc(PAGE_SIZE, GFP_KERNEL);
646	if (!filp->private_data)
647		return -ENOMEM;
648
649	if (kcore_need_update)
650		kcore_update_ram();
651	if (i_size_read(inode) != proc_root_kcore->size) {
652		inode_lock(inode);
653		i_size_write(inode, proc_root_kcore->size);
654		inode_unlock(inode);
655	}
656	return 0;
657}
658
659static int release_kcore(struct inode *inode, struct file *file)
660{
661	kfree(file->private_data);
662	return 0;
663}
664
665static const struct proc_ops kcore_proc_ops = {
666	.proc_flags	= PROC_ENTRY_PERMANENT,
667	.proc_read_iter	= read_kcore_iter,
668	.proc_open	= open_kcore,
669	.proc_release	= release_kcore,
670	.proc_lseek	= default_llseek,
671};
672
673/* just remember that we have to update kcore */
674static int __meminit kcore_callback(struct notifier_block *self,
675				    unsigned long action, void *arg)
676{
677	switch (action) {
678	case MEM_ONLINE:
679	case MEM_OFFLINE:
680		kcore_need_update = 1;
681		break;
682	}
683	return NOTIFY_OK;
684}
685
686
687static struct kcore_list kcore_vmalloc;
688
689#ifdef CONFIG_ARCH_PROC_KCORE_TEXT
690static struct kcore_list kcore_text;
691/*
692 * If defined, special segment is used for mapping kernel text instead of
693 * direct-map area. We need to create special TEXT section.
694 */
695static void __init proc_kcore_text_init(void)
696{
697	kclist_add(&kcore_text, _text, _end - _text, KCORE_TEXT);
698}
699#else
700static void __init proc_kcore_text_init(void)
701{
702}
703#endif
704
705#if defined(CONFIG_MODULES) && defined(MODULES_VADDR)
706/*
707 * MODULES_VADDR has no intersection with VMALLOC_ADDR.
708 */
709static struct kcore_list kcore_modules;
710static void __init add_modules_range(void)
711{
712	if (MODULES_VADDR != VMALLOC_START && MODULES_END != VMALLOC_END) {
713		kclist_add(&kcore_modules, (void *)MODULES_VADDR,
714			MODULES_END - MODULES_VADDR, KCORE_VMALLOC);
715	}
716}
717#else
718static void __init add_modules_range(void)
719{
720}
721#endif
722
723static int __init proc_kcore_init(void)
724{
725	proc_root_kcore = proc_create("kcore", S_IRUSR, NULL, &kcore_proc_ops);
726	if (!proc_root_kcore) {
727		pr_err("couldn't create /proc/kcore\n");
728		return 0; /* Always returns 0. */
729	}
730	/* Store text area if it's special */
731	proc_kcore_text_init();
732	/* Store vmalloc area */
733	kclist_add(&kcore_vmalloc, (void *)VMALLOC_START,
734		VMALLOC_END - VMALLOC_START, KCORE_VMALLOC);
735	add_modules_range();
736	/* Store direct-map area from physical memory map */
737	kcore_update_ram();
738	hotplug_memory_notifier(kcore_callback, DEFAULT_CALLBACK_PRI);
739
740	return 0;
741}
742fs_initcall(proc_kcore_init);