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/crash_core.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/notifier.h>
  22 #include <linux/vmalloc.h>
  23 #include <linux/highmem.h>
  24 #include <linux/printk.h>
  25 #include <linux/memblock.h>
  26 #include <linux/init.h>
  27 #include <linux/slab.h>
  28 #include <linux/uaccess.h>
  29 #include <asm/io.h>
  30 #include <linux/list.h>
  31 #include <linux/ioport.h>
  32 #include <linux/memory.h>
  33 #include <linux/sched/task.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 static LIST_HEAD(kclist_head);
  54 static DECLARE_RWSEM(kclist_lock);
  55 static int kcore_need_update = 1;
  56
  57 /* This doesn't grab kclist_lock, so it should only be used at init time. */
  58 void __init kclist_add(struct kcore_list *new, void *addr, size_t size,
  59                        int type)
  60 {
  61         new->addr = (unsigned long)addr;
  62         new->size = size;
  63         new->type = type;
  64
  65         list_add_tail(&new->list, &kclist_head);
  66 }
  67
  68 static size_t get_kcore_size(int *nphdr, size_t *phdrs_len, size_t *notes_len,
  69                              size_t *data_offset)
  70 {
  71         size_t try, size;
  72         struct kcore_list *m;
  73
  74         *nphdr = 1; /* PT_NOTE */
  75         size = 0;
  76
  77         list_for_each_entry(m, &kclist_head, list) {
  78                 try = kc_vaddr_to_offset((size_t)m->addr + m->size);
  79                 if (try > size)
  80                         size = try;
  81                 *nphdr = *nphdr + 1;
  82         }
  83
  84         *phdrs_len = *nphdr * sizeof(struct elf_phdr);
  85         *notes_len = (4 * sizeof(struct elf_note) +
  86                       3 * ALIGN(sizeof(CORE_STR), 4) +
  87                       VMCOREINFO_NOTE_NAME_BYTES +
  88                       ALIGN(sizeof(struct elf_prstatus), 4) +
  89                       ALIGN(sizeof(struct elf_prpsinfo), 4) +
  90                       ALIGN(arch_task_struct_size, 4) +
  91                       ALIGN(vmcoreinfo_size, 4));
  92         *data_offset = PAGE_ALIGN(sizeof(struct elfhdr) + *phdrs_len +
  93                                   *notes_len);
  94         return *data_offset + size;
  95 }
  96
  97 #ifdef CONFIG_HIGHMEM
  98 /*
  99  * If no highmem, we can assume [0...max_low_pfn) continuous range of memory
 100  * because memory hole is not as big as !HIGHMEM case.
 101  * (HIGHMEM is special because part of memory is _invisible_ from the kernel.)
 102  */
 103 static int kcore_ram_list(struct list_head *head)
 104 {
 105         struct kcore_list *ent;
 106
 107         ent = kmalloc(sizeof(*ent), GFP_KERNEL);
 108         if (!ent)
 109                 return -ENOMEM;
 110         ent->addr = (unsigned long)__va(0);
 111         ent->size = max_low_pfn << PAGE_SHIFT;
 112         ent->type = KCORE_RAM;
 113         list_add(&ent->list, head);
 114         return 0;
 115 }
 116
 117 #else /* !CONFIG_HIGHMEM */
 118
 119 #ifdef CONFIG_SPARSEMEM_VMEMMAP
 120 /* calculate vmemmap's address from given system ram pfn and register it */
 121 static int
 122 get_sparsemem_vmemmap_info(struct kcore_list *ent, struct list_head *head)
 123 {
 124         unsigned long pfn = __pa(ent->addr) >> PAGE_SHIFT;
 125         unsigned long nr_pages = ent->size >> PAGE_SHIFT;
 126         unsigned long start, end;
 127         struct kcore_list *vmm, *tmp;
 128
 129
 130         start = ((unsigned long)pfn_to_page(pfn)) & PAGE_MASK;
 131         end = ((unsigned long)pfn_to_page(pfn + nr_pages)) - 1;
 132         end = PAGE_ALIGN(end);
 133         /* overlap check (because we have to align page */
 134         list_for_each_entry(tmp, head, list) {
 135                 if (tmp->type != KCORE_VMEMMAP)
 136                         continue;
 137                 if (start < tmp->addr + tmp->size)
 138                         if (end > tmp->addr)
 139                                 end = tmp->addr;
 140         }
 141         if (start < end) {
 142                 vmm = kmalloc(sizeof(*vmm), GFP_KERNEL);
 143                 if (!vmm)
 144                         return 0;
 145                 vmm->addr = start;
 146                 vmm->size = end - start;
 147                 vmm->type = KCORE_VMEMMAP;
 148                 list_add_tail(&vmm->list, head);
 149         }
 150         return 1;
 151
 152 }
 153 #else
 154 static int
 155 get_sparsemem_vmemmap_info(struct kcore_list *ent, struct list_head *head)
 156 {
 157         return 1;
 158 }
 159
 160 #endif
 161
 162 static int
 163 kclist_add_private(unsigned long pfn, unsigned long nr_pages, void *arg)
 164 {
 165         struct list_head *head = (struct list_head *)arg;
 166         struct kcore_list *ent;
 167         struct page *p;
 168
 169         if (!pfn_valid(pfn))
 170                 return 1;
 171
 172         p = pfn_to_page(pfn);
 173         if (!memmap_valid_within(pfn, p, page_zone(p)))
 174                 return 1;
 175
 176         ent = kmalloc(sizeof(*ent), GFP_KERNEL);
 177         if (!ent)
 178                 return -ENOMEM;
 179         ent->addr = (unsigned long)page_to_virt(p);
 180         ent->size = nr_pages << PAGE_SHIFT;
 181
 182         if (!virt_addr_valid(ent->addr))
 183                 goto free_out;
 184
 185         /* cut not-mapped area. ....from ppc-32 code. */
 186         if (ULONG_MAX - ent->addr < ent->size)
 187                 ent->size = ULONG_MAX - ent->addr;
 188
 189         /*
 190          * We've already checked virt_addr_valid so we know this address
 191          * is a valid pointer, therefore we can check against it to determine
 192          * if we need to trim
 193          */
 194         if (VMALLOC_START > ent->addr) {
 195                 if (VMALLOC_START - ent->addr < ent->size)
 196                         ent->size = VMALLOC_START - ent->addr;
 197         }
 198
 199         ent->type = KCORE_RAM;
 200         list_add_tail(&ent->list, head);
 201
 202         if (!get_sparsemem_vmemmap_info(ent, head)) {
 203                 list_del(&ent->list);
 204                 goto free_out;
 205         }
 206
 207         return 0;
 208 free_out:
 209         kfree(ent);
 210         return 1;
 211 }
 212
 213 static int kcore_ram_list(struct list_head *list)
 214 {
 215         int nid, ret;
 216         unsigned long end_pfn;
 217
 218         /* Not inialized....update now */
 219         /* find out "max pfn" */
 220         end_pfn = 0;
 221         for_each_node_state(nid, N_MEMORY) {
 222                 unsigned long node_end;
 223                 node_end = node_end_pfn(nid);
 224                 if (end_pfn < node_end)
 225                         end_pfn = node_end;
 226         }
 227         /* scan 0 to max_pfn */
 228         ret = walk_system_ram_range(0, end_pfn, list, kclist_add_private);
 229         if (ret)
 230                 return -ENOMEM;
 231         return 0;
 232 }
 233 #endif /* CONFIG_HIGHMEM */
 234
 235 static int kcore_update_ram(void)
 236 {
 237         LIST_HEAD(list);
 238         LIST_HEAD(garbage);
 239         int nphdr;
 240         size_t phdrs_len, notes_len, data_offset;
 241         struct kcore_list *tmp, *pos;
 242         int ret = 0;
 243
 244         down_write(&kclist_lock);
 245         if (!xchg(&kcore_need_update, 0))
 246                 goto out;
 247
 248         ret = kcore_ram_list(&list);
 249         if (ret) {
 250                 /* Couldn't get the RAM list, try again next time. */
 251                 WRITE_ONCE(kcore_need_update, 1);
 252                 list_splice_tail(&list, &garbage);
 253                 goto out;
 254         }
 255
 256         list_for_each_entry_safe(pos, tmp, &kclist_head, list) {
 257                 if (pos->type == KCORE_RAM || pos->type == KCORE_VMEMMAP)
 258                         list_move(&pos->list, &garbage);
 259         }
 260         list_splice_tail(&list, &kclist_head);
 261
 262         proc_root_kcore->size = get_kcore_size(&nphdr, &phdrs_len, &notes_len,
 263                                                &data_offset);
 264
 265 out:
 266         up_write(&kclist_lock);
 267         list_for_each_entry_safe(pos, tmp, &garbage, list) {
 268                 list_del(&pos->list);
 269                 kfree(pos);
 270         }
 271         return ret;
 272 }
 273
 274 static void append_kcore_note(char *notes, size_t *i, const char *name,
 275                               unsigned int type, const void *desc,
 276                               size_t descsz)
 277 {
 278         struct elf_note *note = (struct elf_note *)&notes[*i];
 279
 280         note->n_namesz = strlen(name) + 1;
 281         note->n_descsz = descsz;
 282         note->n_type = type;
 283         *i += sizeof(*note);
 284         memcpy(&notes[*i], name, note->n_namesz);
 285         *i = ALIGN(*i + note->n_namesz, 4);
 286         memcpy(&notes[*i], desc, descsz);
 287         *i = ALIGN(*i + descsz, 4);
 288 }
 289
 290 static ssize_t
 291 read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
 292 {
 293         char *buf = file->private_data;
 294         size_t phdrs_offset, notes_offset, data_offset;
 295         size_t phdrs_len, notes_len;
 296         struct kcore_list *m;
 297         size_t tsz;
 298         int nphdr;
 299         unsigned long start;
 300         size_t orig_buflen = buflen;
 301         int ret = 0;
 302
 303         down_read(&kclist_lock);
 304
 305         get_kcore_size(&nphdr, &phdrs_len, &notes_len, &data_offset);
 306         phdrs_offset = sizeof(struct elfhdr);
 307         notes_offset = phdrs_offset + phdrs_len;
 308
 309         /* ELF file header. */
 310         if (buflen && *fpos < sizeof(struct elfhdr)) {
 311                 struct elfhdr ehdr = {
 312                         .e_ident = {
 313                                 [EI_MAG0] = ELFMAG0,
 314                                 [EI_MAG1] = ELFMAG1,
 315                                 [EI_MAG2] = ELFMAG2,
 316                                 [EI_MAG3] = ELFMAG3,
 317                                 [EI_CLASS] = ELF_CLASS,
 318                                 [EI_DATA] = ELF_DATA,
 319                                 [EI_VERSION] = EV_CURRENT,
 320                                 [EI_OSABI] = ELF_OSABI,
 321                         },
 322                         .e_type = ET_CORE,
 323                         .e_machine = ELF_ARCH,
 324                         .e_version = EV_CURRENT,
 325                         .e_phoff = sizeof(struct elfhdr),
 326                         .e_flags = ELF_CORE_EFLAGS,
 327                         .e_ehsize = sizeof(struct elfhdr),
 328                         .e_phentsize = sizeof(struct elf_phdr),
 329                         .e_phnum = nphdr,
 330                 };
 331
 332                 tsz = min_t(size_t, buflen, sizeof(struct elfhdr) - *fpos);
 333                 if (copy_to_user(buffer, (char *)&ehdr + *fpos, tsz)) {
 334                         ret = -EFAULT;
 335                         goto out;
 336                 }
 337
 338                 buffer += tsz;
 339                 buflen -= tsz;
 340                 *fpos += tsz;
 341         }
 342
 343         /* ELF program headers. */
 344         if (buflen && *fpos < phdrs_offset + phdrs_len) {
 345                 struct elf_phdr *phdrs, *phdr;
 346
 347                 phdrs = kzalloc(phdrs_len, GFP_KERNEL);
 348                 if (!phdrs) {
 349                         ret = -ENOMEM;
 350                         goto out;
 351                 }
 352
 353                 phdrs[0].p_type = PT_NOTE;
 354                 phdrs[0].p_offset = notes_offset;
 355                 phdrs[0].p_filesz = notes_len;
 356
 357                 phdr = &phdrs[1];
 358                 list_for_each_entry(m, &kclist_head, list) {
 359                         phdr->p_type = PT_LOAD;
 360                         phdr->p_flags = PF_R | PF_W | PF_X;
 361                         phdr->p_offset = kc_vaddr_to_offset(m->addr) + data_offset;
 362                         if (m->type == KCORE_REMAP)
 363                                 phdr->p_vaddr = (size_t)m->vaddr;
 364                         else
 365                                 phdr->p_vaddr = (size_t)m->addr;
 366                         if (m->type == KCORE_RAM || m->type == KCORE_REMAP)
 367                                 phdr->p_paddr = __pa(m->addr);
 368                         else if (m->type == KCORE_TEXT)
 369                                 phdr->p_paddr = __pa_symbol(m->addr);
 370                         else
 371                                 phdr->p_paddr = (elf_addr_t)-1;
 372                         phdr->p_filesz = phdr->p_memsz = m->size;
 373                         phdr->p_align = PAGE_SIZE;
 374                         phdr++;
 375                 }
 376
 377                 tsz = min_t(size_t, buflen, phdrs_offset + phdrs_len - *fpos);
 378                 if (copy_to_user(buffer, (char *)phdrs + *fpos - phdrs_offset,
 379                                  tsz)) {
 380                         kfree(phdrs);
 381                         ret = -EFAULT;
 382                         goto out;
 383                 }
 384                 kfree(phdrs);
 385
 386                 buffer += tsz;
 387                 buflen -= tsz;
 388                 *fpos += tsz;
 389         }
 390
 391         /* ELF note segment. */
 392         if (buflen && *fpos < notes_offset + notes_len) {
 393                 struct elf_prstatus prstatus = {};
 394                 struct elf_prpsinfo prpsinfo = {
 395                         .pr_sname = 'R',
 396                         .pr_fname = "vmlinux",
 397                 };
 398                 char *notes;
 399                 size_t i = 0;
 400
 401                 strlcpy(prpsinfo.pr_psargs, saved_command_line,
 402                         sizeof(prpsinfo.pr_psargs));
 403
 404                 notes = kzalloc(notes_len, GFP_KERNEL);
 405                 if (!notes) {
 406                         ret = -ENOMEM;
 407                         goto out;
 408                 }
 409
 410                 append_kcore_note(notes, &i, CORE_STR, NT_PRSTATUS, &prstatus,
 411                                   sizeof(prstatus));
 412                 append_kcore_note(notes, &i, CORE_STR, NT_PRPSINFO, &prpsinfo,
 413                                   sizeof(prpsinfo));
 414                 append_kcore_note(notes, &i, CORE_STR, NT_TASKSTRUCT, current,
 415                                   arch_task_struct_size);
 416                 /*
 417                  * vmcoreinfo_size is mostly constant after init time, but it
 418                  * can be changed by crash_save_vmcoreinfo(). Racing here with a
 419                  * panic on another CPU before the machine goes down is insanely
 420                  * unlikely, but it's better to not leave potential buffer
 421                  * overflows lying around, regardless.
 422                  */
 423                 append_kcore_note(notes, &i, VMCOREINFO_NOTE_NAME, 0,
 424                                   vmcoreinfo_data,
 425                                   min(vmcoreinfo_size, notes_len - i));
 426
 427                 tsz = min_t(size_t, buflen, notes_offset + notes_len - *fpos);
 428                 if (copy_to_user(buffer, notes + *fpos - notes_offset, tsz)) {
 429                         kfree(notes);
 430                         ret = -EFAULT;
 431                         goto out;
 432                 }
 433                 kfree(notes);
 434
 435                 buffer += tsz;
 436                 buflen -= tsz;
 437                 *fpos += tsz;
 438         }
 439
 440         /*
 441          * Check to see if our file offset matches with any of
 442          * the addresses in the elf_phdr on our list.
 443          */
 444         start = kc_offset_to_vaddr(*fpos - data_offset);
 445         if ((tsz = (PAGE_SIZE - (start & ~PAGE_MASK))) > buflen)
 446                 tsz = buflen;
 447
 448         m = NULL;
 449         while (buflen) {
 450                 /*
 451                  * If this is the first iteration or the address is not within
 452                  * the previous entry, search for a matching entry.
 453                  */
 454                 if (!m || start < m->addr || start >= m->addr + m->size) {
 455                         list_for_each_entry(m, &kclist_head, list) {
 456                                 if (start >= m->addr &&
 457                                     start < m->addr + m->size)
 458                                         break;
 459                         }
 460                 }
 461
 462                 if (&m->list == &kclist_head) {
 463                         if (clear_user(buffer, tsz)) {
 464                                 ret = -EFAULT;
 465                                 goto out;
 466                         }
 467                         m = NULL;       /* skip the list anchor */
 468                 } else if (m->type == KCORE_VMALLOC) {
 469                         vread(buf, (char *)start, tsz);
 470                         /* we have to zero-fill user buffer even if no read */
 471                         if (copy_to_user(buffer, buf, tsz)) {
 472                                 ret = -EFAULT;
 473                                 goto out;
 474                         }
 475                 } else if (m->type == KCORE_USER) {
 476                         /* User page is handled prior to normal kernel page: */
 477                         if (copy_to_user(buffer, (char *)start, tsz)) {
 478                                 ret = -EFAULT;
 479                                 goto out;
 480                         }
 481                 } else {
 482                         if (kern_addr_valid(start)) {
 483                                 /*
 484                                  * Using bounce buffer to bypass the
 485                                  * hardened user copy kernel text checks.
 486                                  */
 487                                 if (probe_kernel_read(buf, (void *) start, tsz)) {
 488                                         if (clear_user(buffer, tsz)) {
 489                                                 ret = -EFAULT;
 490                                                 goto out;
 491                                         }
 492                                 } else {
 493                                         if (copy_to_user(buffer, buf, tsz)) {
 494                                                 ret = -EFAULT;
 495                                                 goto out;
 496                                         }
 497                                 }
 498                         } else {
 499                                 if (clear_user(buffer, tsz)) {
 500                                         ret = -EFAULT;
 501                                         goto out;
 502                                 }
 503                         }
 504                 }
 505                 buflen -= tsz;
 506                 *fpos += tsz;
 507                 buffer += tsz;
 508                 start += tsz;
 509                 tsz = (buflen > PAGE_SIZE ? PAGE_SIZE : buflen);
 510         }
 511
 512 out:
 513         up_read(&kclist_lock);
 514         if (ret)
 515                 return ret;
 516         return orig_buflen - buflen;
 517 }
 518
 519 static int open_kcore(struct inode *inode, struct file *filp)
 520 {
 521         if (!capable(CAP_SYS_RAWIO))
 522                 return -EPERM;
 523
 524         filp->private_data = kmalloc(PAGE_SIZE, GFP_KERNEL);
 525         if (!filp->private_data)
 526                 return -ENOMEM;
 527
 528         if (kcore_need_update)
 529                 kcore_update_ram();
 530         if (i_size_read(inode) != proc_root_kcore->size) {
 531                 inode_lock(inode);
 532                 i_size_write(inode, proc_root_kcore->size);
 533                 inode_unlock(inode);
 534         }
 535         return 0;
 536 }
 537
 538 static int release_kcore(struct inode *inode, struct file *file)
 539 {
 540         kfree(file->private_data);
 541         return 0;
 542 }
 543
 544 static const struct file_operations proc_kcore_operations = {
 545         .read           = read_kcore,
 546         .open           = open_kcore,
 547         .release        = release_kcore,
 548         .llseek         = default_llseek,
 549 };
 550
 551 /* just remember that we have to update kcore */
 552 static int __meminit kcore_callback(struct notifier_block *self,
 553                                     unsigned long action, void *arg)
 554 {
 555         switch (action) {
 556         case MEM_ONLINE:
 557         case MEM_OFFLINE:
 558                 kcore_need_update = 1;
 559                 break;
 560         }
 561         return NOTIFY_OK;
 562 }
 563
 564 static struct notifier_block kcore_callback_nb __meminitdata = {
 565         .notifier_call = kcore_callback,
 566         .priority = 0,
 567 };
 568
 569 static struct kcore_list kcore_vmalloc;
 570
 571 #ifdef CONFIG_ARCH_PROC_KCORE_TEXT
 572 static struct kcore_list kcore_text;
 573 /*
 574  * If defined, special segment is used for mapping kernel text instead of
 575  * direct-map area. We need to create special TEXT section.
 576  */
 577 static void __init proc_kcore_text_init(void)
 578 {
 579         kclist_add(&kcore_text, _text, _end - _text, KCORE_TEXT);
 580 }
 581 #else
 582 static void __init proc_kcore_text_init(void)
 583 {
 584 }
 585 #endif
 586
 587 #if defined(CONFIG_MODULES) && defined(MODULES_VADDR)
 588 /*
 589  * MODULES_VADDR has no intersection with VMALLOC_ADDR.
 590  */
 591 struct kcore_list kcore_modules;
 592 static void __init add_modules_range(void)
 593 {
 594         if (MODULES_VADDR != VMALLOC_START && MODULES_END != VMALLOC_END) {
 595                 kclist_add(&kcore_modules, (void *)MODULES_VADDR,
 596                         MODULES_END - MODULES_VADDR, KCORE_VMALLOC);
 597         }
 598 }
 599 #else
 600 static void __init add_modules_range(void)
 601 {
 602 }
 603 #endif
 604
 605 static int __init proc_kcore_init(void)
 606 {
 607         proc_root_kcore = proc_create("kcore", S_IRUSR, NULL,
 608                                       &proc_kcore_operations);
 609         if (!proc_root_kcore) {
 610                 pr_err("couldn't create /proc/kcore\n");
 611                 return 0; /* Always returns 0. */
 612         }
 613         /* Store text area if it's special */
 614         proc_kcore_text_init();
 615         /* Store vmalloc area */
 616         kclist_add(&kcore_vmalloc, (void *)VMALLOC_START,
 617                 VMALLOC_END - VMALLOC_START, KCORE_VMALLOC);
 618         add_modules_range();
 619         /* Store direct-map area from physical memory map */
 620         kcore_update_ram();
 621         register_hotmemory_notifier(&kcore_callback_nb);
 622
 623         return 0;
 624 }
 625 fs_initcall(proc_kcore_init);