fs/proc/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 #define CORE_STR "CORE"
  38
  39 #ifndef ELF_CORE_EFLAGS
  40 #define ELF_CORE_EFLAGS 0
  41 #endif
  42
  43 static struct proc_dir_entry *proc_root_kcore;
  44
  45
  46 #ifndef kc_vaddr_to_offset
  47 #define kc_vaddr_to_offset(v) ((v) - PAGE_OFFSET)
  48 #endif
  49 #ifndef kc_offset_to_vaddr
  50 #define kc_offset_to_vaddr(o) ((o) + PAGE_OFFSET)
  51 #endif
  52
  53 #ifndef kc_xlate_dev_mem_ptr
  54 #define kc_xlate_dev_mem_ptr kc_xlate_dev_mem_ptr
  55 static inline void *kc_xlate_dev_mem_ptr(phys_addr_t phys)
  56 {
  57         return __va(phys);
  58 }
  59 #endif
  60 #ifndef kc_unxlate_dev_mem_ptr
  61 #define kc_unxlate_dev_mem_ptr kc_unxlate_dev_mem_ptr
  62 static inline void kc_unxlate_dev_mem_ptr(phys_addr_t phys, void *virt)
  63 {
  64 }
  65 #endif
  66
  67 static LIST_HEAD(kclist_head);
  68 static DECLARE_RWSEM(kclist_lock);
  69 static int kcore_need_update = 1;
  70
  71 /*
  72  * Returns > 0 for RAM pages, 0 for non-RAM pages, < 0 on error
  73  * Same as oldmem_pfn_is_ram in vmcore
  74  */
  75 static int (*mem_pfn_is_ram)(unsigned long pfn);
  76
  77 int __init register_mem_pfn_is_ram(int (*fn)(unsigned long pfn))
  78 {
  79         if (mem_pfn_is_ram)
  80                 return -EBUSY;
  81         mem_pfn_is_ram = fn;
  82         return 0;
  83 }
  84
  85 static int pfn_is_ram(unsigned long pfn)
  86 {
  87         if (mem_pfn_is_ram)
  88                 return mem_pfn_is_ram(pfn);
  89         else
  90                 return 1;
  91 }
  92
  93 /* This doesn't grab kclist_lock, so it should only be used at init time. */
  94 void __init kclist_add(struct kcore_list *new, void *addr, size_t size,
  95                        int type)
  96 {
  97         new->addr = (unsigned long)addr;
  98         new->size = size;
  99         new->type = type;
 100
 101         list_add_tail(&new->list, &kclist_head);
 102 }
 103
 104 static size_t get_kcore_size(int *nphdr, size_t *phdrs_len, size_t *notes_len,
 105                              size_t *data_offset)
 106 {
 107         size_t try, size;
 108         struct kcore_list *m;
 109
 110         *nphdr = 1; /* PT_NOTE */
 111         size = 0;
 112
 113         list_for_each_entry(m, &kclist_head, list) {
 114                 try = kc_vaddr_to_offset((size_t)m->addr + m->size);
 115                 if (try > size)
 116                         size = try;
 117                 *nphdr = *nphdr + 1;
 118         }
 119
 120         *phdrs_len = *nphdr * sizeof(struct elf_phdr);
 121         *notes_len = (4 * sizeof(struct elf_note) +
 122                       3 * ALIGN(sizeof(CORE_STR), 4) +
 123                       VMCOREINFO_NOTE_NAME_BYTES +
 124                       ALIGN(sizeof(struct elf_prstatus), 4) +
 125                       ALIGN(sizeof(struct elf_prpsinfo), 4) +
 126                       ALIGN(arch_task_struct_size, 4) +
 127                       ALIGN(vmcoreinfo_size, 4));
 128         *data_offset = PAGE_ALIGN(sizeof(struct elfhdr) + *phdrs_len +
 129                                   *notes_len);
 130         return *data_offset + size;
 131 }
 132
 133 #ifdef CONFIG_HIGHMEM
 134 /*
 135  * If no highmem, we can assume [0...max_low_pfn) continuous range of memory
 136  * because memory hole is not as big as !HIGHMEM case.
 137  * (HIGHMEM is special because part of memory is _invisible_ from the kernel.)
 138  */
 139 static int kcore_ram_list(struct list_head *head)
 140 {
 141         struct kcore_list *ent;
 142
 143         ent = kmalloc(sizeof(*ent), GFP_KERNEL);
 144         if (!ent)
 145                 return -ENOMEM;
 146         ent->addr = (unsigned long)__va(0);
 147         ent->size = max_low_pfn << PAGE_SHIFT;
 148         ent->type = KCORE_RAM;
 149         list_add(&ent->list, head);
 150         return 0;
 151 }
 152
 153 #else /* !CONFIG_HIGHMEM */
 154
 155 #ifdef CONFIG_SPARSEMEM_VMEMMAP
 156 /* calculate vmemmap's address from given system ram pfn and register it */
 157 static int
 158 get_sparsemem_vmemmap_info(struct kcore_list *ent, struct list_head *head)
 159 {
 160         unsigned long pfn = __pa(ent->addr) >> PAGE_SHIFT;
 161         unsigned long nr_pages = ent->size >> PAGE_SHIFT;
 162         unsigned long start, end;
 163         struct kcore_list *vmm, *tmp;
 164
 165
 166         start = ((unsigned long)pfn_to_page(pfn)) & PAGE_MASK;
 167         end = ((unsigned long)pfn_to_page(pfn + nr_pages)) - 1;
 168         end = PAGE_ALIGN(end);
 169         /* overlap check (because we have to align page */
 170         list_for_each_entry(tmp, head, list) {
 171                 if (tmp->type != KCORE_VMEMMAP)
 172                         continue;
 173                 if (start < tmp->addr + tmp->size)
 174                         if (end > tmp->addr)
 175                                 end = tmp->addr;
 176         }
 177         if (start < end) {
 178                 vmm = kmalloc(sizeof(*vmm), GFP_KERNEL);
 179                 if (!vmm)
 180                         return 0;
 181                 vmm->addr = start;
 182                 vmm->size = end - start;
 183                 vmm->type = KCORE_VMEMMAP;
 184                 list_add_tail(&vmm->list, head);
 185         }
 186         return 1;
 187
 188 }
 189 #else
 190 static int
 191 get_sparsemem_vmemmap_info(struct kcore_list *ent, struct list_head *head)
 192 {
 193         return 1;
 194 }
 195
 196 #endif
 197
 198 static int
 199 kclist_add_private(unsigned long pfn, unsigned long nr_pages, void *arg)
 200 {
 201         struct list_head *head = (struct list_head *)arg;
 202         struct kcore_list *ent;
 203         struct page *p;
 204
 205         if (!pfn_valid(pfn))
 206                 return 1;
 207
 208         p = pfn_to_page(pfn);
 209
 210         ent = kmalloc(sizeof(*ent), GFP_KERNEL);
 211         if (!ent)
 212                 return -ENOMEM;
 213         ent->addr = (unsigned long)page_to_virt(p);
 214         ent->size = nr_pages << PAGE_SHIFT;
 215
 216         if (!virt_addr_valid((void *)ent->addr))
 217                 goto free_out;
 218
 219         /* cut not-mapped area. ....from ppc-32 code. */
 220         if (ULONG_MAX - ent->addr < ent->size)
 221                 ent->size = ULONG_MAX - ent->addr;
 222
 223         /*
 224          * We've already checked virt_addr_valid so we know this address
 225          * is a valid pointer, therefore we can check against it to determine
 226          * if we need to trim
 227          */
 228         if (VMALLOC_START > ent->addr) {
 229                 if (VMALLOC_START - ent->addr < ent->size)
 230                         ent->size = VMALLOC_START - ent->addr;
 231         }
 232
 233         ent->type = KCORE_RAM;
 234         list_add_tail(&ent->list, head);
 235
 236         if (!get_sparsemem_vmemmap_info(ent, head)) {
 237                 list_del(&ent->list);
 238                 goto free_out;
 239         }
 240
 241         return 0;
 242 free_out:
 243         kfree(ent);
 244         return 1;
 245 }
 246
 247 static int kcore_ram_list(struct list_head *list)
 248 {
 249         int nid, ret;
 250         unsigned long end_pfn;
 251
 252         /* Not initialized....update now */
 253         /* find out "max pfn" */
 254         end_pfn = 0;
 255         for_each_node_state(nid, N_MEMORY) {
 256                 unsigned long node_end;
 257                 node_end = node_end_pfn(nid);
 258                 if (end_pfn < node_end)
 259                         end_pfn = node_end;
 260         }
 261         /* scan 0 to max_pfn */
 262         ret = walk_system_ram_range(0, end_pfn, list, kclist_add_private);
 263         if (ret)
 264                 return -ENOMEM;
 265         return 0;
 266 }
 267 #endif /* CONFIG_HIGHMEM */
 268
 269 static int kcore_update_ram(void)
 270 {
 271         LIST_HEAD(list);
 272         LIST_HEAD(garbage);
 273         int nphdr;
 274         size_t phdrs_len, notes_len, data_offset;
 275         struct kcore_list *tmp, *pos;
 276         int ret = 0;
 277
 278         down_write(&kclist_lock);
 279         if (!xchg(&kcore_need_update, 0))
 280                 goto out;
 281
 282         ret = kcore_ram_list(&list);
 283         if (ret) {
 284                 /* Couldn't get the RAM list, try again next time. */
 285                 WRITE_ONCE(kcore_need_update, 1);
 286                 list_splice_tail(&list, &garbage);
 287                 goto out;
 288         }
 289
 290         list_for_each_entry_safe(pos, tmp, &kclist_head, list) {
 291                 if (pos->type == KCORE_RAM || pos->type == KCORE_VMEMMAP)
 292                         list_move(&pos->list, &garbage);
 293         }
 294         list_splice_tail(&list, &kclist_head);
 295
 296         proc_root_kcore->size = get_kcore_size(&nphdr, &phdrs_len, &notes_len,
 297                                                &data_offset);
 298
 299 out:
 300         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
 308 static 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
 324 static 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, data_offset;
 330         size_t page_offline_frozen = 1;
 331         size_t phdrs_len, notes_len;
 332         struct kcore_list *m;
 333         size_t tsz;
 334         int nphdr;
 335         unsigned long start;
 336         size_t buflen = iov_iter_count(iter);
 337         size_t orig_buflen = buflen;
 338         int ret = 0;
 339
 340         down_read(&kclist_lock);
 341         /*
 342          * Don't race against drivers that set PageOffline() and expect no
 343          * further page access.
 344          */
 345         page_offline_freeze();
 346
 347         get_kcore_size(&nphdr, &phdrs_len, &notes_len, &data_offset);
 348         phdrs_offset = sizeof(struct elfhdr);
 349         notes_offset = phdrs_offset + phdrs_len;
 350
 351         /* ELF file header. */
 352         if (buflen && *fpos < sizeof(struct elfhdr)) {
 353                 struct elfhdr ehdr = {
 354                         .e_ident = {
 355                                 [EI_MAG0] = ELFMAG0,
 356                                 [EI_MAG1] = ELFMAG1,
 357                                 [EI_MAG2] = ELFMAG2,
 358                                 [EI_MAG3] = ELFMAG3,
 359                                 [EI_CLASS] = ELF_CLASS,
 360                                 [EI_DATA] = ELF_DATA,
 361                                 [EI_VERSION] = EV_CURRENT,
 362                                 [EI_OSABI] = ELF_OSABI,
 363                         },
 364                         .e_type = ET_CORE,
 365                         .e_machine = ELF_ARCH,
 366                         .e_version = EV_CURRENT,
 367                         .e_phoff = sizeof(struct elfhdr),
 368                         .e_flags = ELF_CORE_EFLAGS,
 369                         .e_ehsize = sizeof(struct elfhdr),
 370                         .e_phentsize = sizeof(struct elf_phdr),
 371                         .e_phnum = nphdr,
 372                 };
 373
 374                 tsz = min_t(size_t, buflen, sizeof(struct elfhdr) - *fpos);
 375                 if (copy_to_iter((char *)&ehdr + *fpos, tsz, iter) != tsz) {
 376                         ret = -EFAULT;
 377                         goto out;
 378                 }
 379
 380                 buflen -= tsz;
 381                 *fpos += tsz;
 382         }
 383
 384         /* ELF program headers. */
 385         if (buflen && *fpos < phdrs_offset + phdrs_len) {
 386                 struct elf_phdr *phdrs, *phdr;
 387
 388                 phdrs = kzalloc(phdrs_len, GFP_KERNEL);
 389                 if (!phdrs) {
 390                         ret = -ENOMEM;
 391                         goto out;
 392                 }
 393
 394                 phdrs[0].p_type = PT_NOTE;
 395                 phdrs[0].p_offset = notes_offset;
 396                 phdrs[0].p_filesz = notes_len;
 397
 398                 phdr = &phdrs[1];
 399                 list_for_each_entry(m, &kclist_head, list) {
 400                         phdr->p_type = PT_LOAD;
 401                         phdr->p_flags = PF_R | PF_W | PF_X;
 402                         phdr->p_offset = kc_vaddr_to_offset(m->addr) + data_offset;
 403                         phdr->p_vaddr = (size_t)m->addr;
 404                         if (m->type == KCORE_RAM)
 405                                 phdr->p_paddr = __pa(m->addr);
 406                         else if (m->type == KCORE_TEXT)
 407                                 phdr->p_paddr = __pa_symbol(m->addr);
 408                         else
 409                                 phdr->p_paddr = (elf_addr_t)-1;
 410                         phdr->p_filesz = phdr->p_memsz = m->size;
 411                         phdr->p_align = PAGE_SIZE;
 412                         phdr++;
 413                 }
 414
 415                 tsz = min_t(size_t, buflen, phdrs_offset + phdrs_len - *fpos);
 416                 if (copy_to_iter((char *)phdrs + *fpos - phdrs_offset, tsz,
 417                                  iter) != tsz) {
 418                         kfree(phdrs);
 419                         ret = -EFAULT;
 420                         goto out;
 421                 }
 422                 kfree(phdrs);
 423
 424                 buflen -= tsz;
 425                 *fpos += tsz;
 426         }
 427
 428         /* ELF note segment. */
 429         if (buflen && *fpos < notes_offset + notes_len) {
 430                 struct elf_prstatus prstatus = {};
 431                 struct elf_prpsinfo prpsinfo = {
 432                         .pr_sname = 'R',
 433                         .pr_fname = "vmlinux",
 434                 };
 435                 char *notes;
 436                 size_t i = 0;
 437
 438                 strscpy(prpsinfo.pr_psargs, saved_command_line,
 439                         sizeof(prpsinfo.pr_psargs));
 440
 441                 notes = kzalloc(notes_len, GFP_KERNEL);
 442                 if (!notes) {
 443                         ret = -ENOMEM;
 444                         goto out;
 445                 }
 446
 447                 append_kcore_note(notes, &i, CORE_STR, NT_PRSTATUS, &prstatus,
 448                                   sizeof(prstatus));
 449                 append_kcore_note(notes, &i, CORE_STR, NT_PRPSINFO, &prpsinfo,
 450                                   sizeof(prpsinfo));
 451                 append_kcore_note(notes, &i, CORE_STR, NT_TASKSTRUCT, current,
 452                                   arch_task_struct_size);
 453                 /*
 454                  * vmcoreinfo_size is mostly constant after init time, but it
 455                  * can be changed by crash_save_vmcoreinfo(). Racing here with a
 456                  * panic on another CPU before the machine goes down is insanely
 457                  * unlikely, but it's better to not leave potential buffer
 458                  * overflows lying around, regardless.
 459                  */
 460                 append_kcore_note(notes, &i, VMCOREINFO_NOTE_NAME, 0,
 461                                   vmcoreinfo_data,
 462                                   min(vmcoreinfo_size, notes_len - i));
 463
 464                 tsz = min_t(size_t, buflen, notes_offset + 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 - 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                 }
 620 skip:
 621                 buflen -= tsz;
 622                 *fpos += tsz;
 623                 start += tsz;
 624                 tsz = (buflen > PAGE_SIZE ? PAGE_SIZE : buflen);
 625         }
 626
 627 out:
 628         page_offline_thaw();
 629         up_read(&kclist_lock);
 630         if (ret)
 631                 return ret;
 632         return orig_buflen - buflen;
 633 }
 634
 635 static 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
 659 static int release_kcore(struct inode *inode, struct file *file)
 660 {
 661         kfree(file->private_data);
 662         return 0;
 663 }
 664
 665 static const struct proc_ops kcore_proc_ops = {
 666         .proc_read_iter = read_kcore_iter,
 667         .proc_open      = open_kcore,
 668         .proc_release   = release_kcore,
 669         .proc_lseek     = default_llseek,
 670 };
 671
 672 /* just remember that we have to update kcore */
 673 static int __meminit kcore_callback(struct notifier_block *self,
 674                                     unsigned long action, void *arg)
 675 {
 676         switch (action) {
 677         case MEM_ONLINE:
 678         case MEM_OFFLINE:
 679                 kcore_need_update = 1;
 680                 break;
 681         }
 682         return NOTIFY_OK;
 683 }
 684
 685
 686 static struct kcore_list kcore_vmalloc;
 687
 688 #ifdef CONFIG_ARCH_PROC_KCORE_TEXT
 689 static struct kcore_list kcore_text;
 690 /*
 691  * If defined, special segment is used for mapping kernel text instead of
 692  * direct-map area. We need to create special TEXT section.
 693  */
 694 static void __init proc_kcore_text_init(void)
 695 {
 696         kclist_add(&kcore_text, _text, _end - _text, KCORE_TEXT);
 697 }
 698 #else
 699 static void __init proc_kcore_text_init(void)
 700 {
 701 }
 702 #endif
 703
 704 #if defined(CONFIG_MODULES) && defined(MODULES_VADDR)
 705 /*
 706  * MODULES_VADDR has no intersection with VMALLOC_ADDR.
 707  */
 708 static struct kcore_list kcore_modules;
 709 static void __init add_modules_range(void)
 710 {
 711         if (MODULES_VADDR != VMALLOC_START && MODULES_END != VMALLOC_END) {
 712                 kclist_add(&kcore_modules, (void *)MODULES_VADDR,
 713                         MODULES_END - MODULES_VADDR, KCORE_VMALLOC);
 714         }
 715 }
 716 #else
 717 static void __init add_modules_range(void)
 718 {
 719 }
 720 #endif
 721
 722 static int __init proc_kcore_init(void)
 723 {
 724         proc_root_kcore = proc_create("kcore", S_IRUSR, NULL, &kcore_proc_ops);
 725         if (!proc_root_kcore) {
 726                 pr_err("couldn't create /proc/kcore\n");
 727                 return 0; /* Always returns 0. */
 728         }
 729         /* Store text area if it's special */
 730         proc_kcore_text_init();
 731         /* Store vmalloc area */
 732         kclist_add(&kcore_vmalloc, (void *)VMALLOC_START,
 733                 VMALLOC_END - VMALLOC_START, KCORE_VMALLOC);
 734         add_modules_range();
 735         /* Store direct-map area from physical memory map */
 736         kcore_update_ram();
 737         hotplug_memory_notifier(kcore_callback, DEFAULT_CALLBACK_PRI);
 738
 739         return 0;
 740 }
 741 fs_initcall(proc_kcore_init);