arch/s390/kernel/crash_dump.c

   1 /*
   2  * S390 kdump implementation
   3  *
   4  * Copyright IBM Corp. 2011
   5  * Author(s): Michael Holzheu <holzheu@linux.vnet.ibm.com>
   6  */
   7
   8 #include <linux/crash_dump.h>
   9 #include <asm/lowcore.h>
  10 #include <linux/kernel.h>
  11 #include <linux/module.h>
  12 #include <linux/gfp.h>
  13 #include <linux/slab.h>
  14 #include <linux/bootmem.h>
  15 #include <linux/elf.h>
  16 #include <asm/asm-offsets.h>
  17 #include <linux/memblock.h>
  18 #include <asm/os_info.h>
  19 #include <asm/elf.h>
  20 #include <asm/ipl.h>
  21 #include <asm/sclp.h>
  22
  23 #define PTR_ADD(x, y) (((char *) (x)) + ((unsigned long) (y)))
  24 #define PTR_SUB(x, y) (((char *) (x)) - ((unsigned long) (y)))
  25 #define PTR_DIFF(x, y) ((unsigned long)(((char *) (x)) - ((unsigned long) (y))))
  26
  27 static struct memblock_region oldmem_region;
  28
  29 static struct memblock_type oldmem_type = {
  30         .cnt = 1,
  31         .max = 1,
  32         .total_size = 0,
  33         .regions = &oldmem_region,
  34 };
  35
  36 struct save_area {
  37         struct list_head list;
  38         u64 psw[2];
  39         u64 ctrs[16];
  40         u64 gprs[16];
  41         u32 acrs[16];
  42         u64 fprs[16];
  43         u32 fpc;
  44         u32 prefix;
  45         u64 todpreg;
  46         u64 timer;
  47         u64 todcmp;
  48         u64 vxrs_low[16];
  49         __vector128 vxrs_high[16];
  50 };
  51
  52 static LIST_HEAD(dump_save_areas);
  53
  54 /*
  55  * Allocate a save area
  56  */
  57 struct save_area * __init save_area_alloc(bool is_boot_cpu)
  58 {
  59         struct save_area *sa;
  60
  61         sa = (void *) memblock_alloc(sizeof(*sa), 8);
  62         if (is_boot_cpu)
  63                 list_add(&sa->list, &dump_save_areas);
  64         else
  65                 list_add_tail(&sa->list, &dump_save_areas);
  66         return sa;
  67 }
  68
  69 /*
  70  * Return the address of the save area for the boot CPU
  71  */
  72 struct save_area * __init save_area_boot_cpu(void)
  73 {
  74         return list_first_entry_or_null(&dump_save_areas, struct save_area, list);
  75 }
  76
  77 /*
  78  * Copy CPU registers into the save area
  79  */
  80 void __init save_area_add_regs(struct save_area *sa, void *regs)
  81 {
  82         struct lowcore *lc;
  83
  84         lc = (struct lowcore *)(regs - __LC_FPREGS_SAVE_AREA);
  85         memcpy(&sa->psw, &lc->psw_save_area, sizeof(sa->psw));
  86         memcpy(&sa->ctrs, &lc->cregs_save_area, sizeof(sa->ctrs));
  87         memcpy(&sa->gprs, &lc->gpregs_save_area, sizeof(sa->gprs));
  88         memcpy(&sa->acrs, &lc->access_regs_save_area, sizeof(sa->acrs));
  89         memcpy(&sa->fprs, &lc->floating_pt_save_area, sizeof(sa->fprs));
  90         memcpy(&sa->fpc, &lc->fpt_creg_save_area, sizeof(sa->fpc));
  91         memcpy(&sa->prefix, &lc->prefixreg_save_area, sizeof(sa->prefix));
  92         memcpy(&sa->todpreg, &lc->tod_progreg_save_area, sizeof(sa->todpreg));
  93         memcpy(&sa->timer, &lc->cpu_timer_save_area, sizeof(sa->timer));
  94         memcpy(&sa->todcmp, &lc->clock_comp_save_area, sizeof(sa->todcmp));
  95 }
  96
  97 /*
  98  * Copy vector registers into the save area
  99  */
 100 void __init save_area_add_vxrs(struct save_area *sa, __vector128 *vxrs)
 101 {
 102         int i;
 103
 104         /* Copy lower halves of vector registers 0-15 */
 105         for (i = 0; i < 16; i++)
 106                 memcpy(&sa->vxrs_low[i], &vxrs[i].u[2], 8);
 107         /* Copy vector registers 16-31 */
 108         memcpy(sa->vxrs_high, vxrs + 16, 16 * sizeof(__vector128));
 109 }
 110
 111 /*
 112  * Return physical address for virtual address
 113  */
 114 static inline void *load_real_addr(void *addr)
 115 {
 116         unsigned long real_addr;
 117
 118         asm volatile(
 119                    "    lra     %0,0(%1)\n"
 120                    "    jz      0f\n"
 121                    "    la      %0,0\n"
 122                    "0:"
 123                    : "=a" (real_addr) : "a" (addr) : "cc");
 124         return (void *)real_addr;
 125 }
 126
 127 /*
 128  * Copy memory of the old, dumped system to a kernel space virtual address
 129  */
 130 int copy_oldmem_kernel(void *dst, void *src, size_t count)
 131 {
 132         unsigned long from, len;
 133         void *ra;
 134         int rc;
 135
 136         while (count) {
 137                 from = __pa(src);
 138                 if (!OLDMEM_BASE && from < sclp.hsa_size) {
 139                         /* Copy from zfcpdump HSA area */
 140                         len = min(count, sclp.hsa_size - from);
 141                         rc = memcpy_hsa_kernel(dst, from, len);
 142                         if (rc)
 143                                 return rc;
 144                 } else {
 145                         /* Check for swapped kdump oldmem areas */
 146                         if (OLDMEM_BASE && from - OLDMEM_BASE < OLDMEM_SIZE) {
 147                                 from -= OLDMEM_BASE;
 148                                 len = min(count, OLDMEM_SIZE - from);
 149                         } else if (OLDMEM_BASE && from < OLDMEM_SIZE) {
 150                                 len = min(count, OLDMEM_SIZE - from);
 151                                 from += OLDMEM_BASE;
 152                         } else {
 153                                 len = count;
 154                         }
 155                         if (is_vmalloc_or_module_addr(dst)) {
 156                                 ra = load_real_addr(dst);
 157                                 len = min(PAGE_SIZE - offset_in_page(ra), len);
 158                         } else {
 159                                 ra = dst;
 160                         }
 161                         if (memcpy_real(ra, (void *) from, len))
 162                                 return -EFAULT;
 163                 }
 164                 dst += len;
 165                 src += len;
 166                 count -= len;
 167         }
 168         return 0;
 169 }
 170
 171 /*
 172  * Copy memory of the old, dumped system to a user space virtual address
 173  */
 174 static int copy_oldmem_user(void __user *dst, void *src, size_t count)
 175 {
 176         unsigned long from, len;
 177         int rc;
 178
 179         while (count) {
 180                 from = __pa(src);
 181                 if (!OLDMEM_BASE && from < sclp.hsa_size) {
 182                         /* Copy from zfcpdump HSA area */
 183                         len = min(count, sclp.hsa_size - from);
 184                         rc = memcpy_hsa_user(dst, from, len);
 185                         if (rc)
 186                                 return rc;
 187                 } else {
 188                         /* Check for swapped kdump oldmem areas */
 189                         if (OLDMEM_BASE && from - OLDMEM_BASE < OLDMEM_SIZE) {
 190                                 from -= OLDMEM_BASE;
 191                                 len = min(count, OLDMEM_SIZE - from);
 192                         } else if (OLDMEM_BASE && from < OLDMEM_SIZE) {
 193                                 len = min(count, OLDMEM_SIZE - from);
 194                                 from += OLDMEM_BASE;
 195                         } else {
 196                                 len = count;
 197                         }
 198                         rc = copy_to_user_real(dst, (void *) from, count);
 199                         if (rc)
 200                                 return rc;
 201                 }
 202                 dst += len;
 203                 src += len;
 204                 count -= len;
 205         }
 206         return 0;
 207 }
 208
 209 /*
 210  * Copy one page from "oldmem"
 211  */
 212 ssize_t copy_oldmem_page(unsigned long pfn, char *buf, size_t csize,
 213                          unsigned long offset, int userbuf)
 214 {
 215         void *src;
 216         int rc;
 217
 218         if (!csize)
 219                 return 0;
 220         src = (void *) (pfn << PAGE_SHIFT) + offset;
 221         if (userbuf)
 222                 rc = copy_oldmem_user((void __force __user *) buf, src, csize);
 223         else
 224                 rc = copy_oldmem_kernel((void *) buf, src, csize);
 225         return rc;
 226 }
 227
 228 /*
 229  * Remap "oldmem" for kdump
 230  *
 231  * For the kdump reserved memory this functions performs a swap operation:
 232  * [0 - OLDMEM_SIZE] is mapped to [OLDMEM_BASE - OLDMEM_BASE + OLDMEM_SIZE]
 233  */
 234 static int remap_oldmem_pfn_range_kdump(struct vm_area_struct *vma,
 235                                         unsigned long from, unsigned long pfn,
 236                                         unsigned long size, pgprot_t prot)
 237 {
 238         unsigned long size_old;
 239         int rc;
 240
 241         if (pfn < OLDMEM_SIZE >> PAGE_SHIFT) {
 242                 size_old = min(size, OLDMEM_SIZE - (pfn << PAGE_SHIFT));
 243                 rc = remap_pfn_range(vma, from,
 244                                      pfn + (OLDMEM_BASE >> PAGE_SHIFT),
 245                                      size_old, prot);
 246                 if (rc || size == size_old)
 247                         return rc;
 248                 size -= size_old;
 249                 from += size_old;
 250                 pfn += size_old >> PAGE_SHIFT;
 251         }
 252         return remap_pfn_range(vma, from, pfn, size, prot);
 253 }
 254
 255 /*
 256  * Remap "oldmem" for zfcpdump
 257  *
 258  * We only map available memory above HSA size. Memory below HSA size
 259  * is read on demand using the copy_oldmem_page() function.
 260  */
 261 static int remap_oldmem_pfn_range_zfcpdump(struct vm_area_struct *vma,
 262                                            unsigned long from,
 263                                            unsigned long pfn,
 264                                            unsigned long size, pgprot_t prot)
 265 {
 266         unsigned long hsa_end = sclp.hsa_size;
 267         unsigned long size_hsa;
 268
 269         if (pfn < hsa_end >> PAGE_SHIFT) {
 270                 size_hsa = min(size, hsa_end - (pfn << PAGE_SHIFT));
 271                 if (size == size_hsa)
 272                         return 0;
 273                 size -= size_hsa;
 274                 from += size_hsa;
 275                 pfn += size_hsa >> PAGE_SHIFT;
 276         }
 277         return remap_pfn_range(vma, from, pfn, size, prot);
 278 }
 279
 280 /*
 281  * Remap "oldmem" for kdump or zfcpdump
 282  */
 283 int remap_oldmem_pfn_range(struct vm_area_struct *vma, unsigned long from,
 284                            unsigned long pfn, unsigned long size, pgprot_t prot)
 285 {
 286         if (OLDMEM_BASE)
 287                 return remap_oldmem_pfn_range_kdump(vma, from, pfn, size, prot);
 288         else
 289                 return remap_oldmem_pfn_range_zfcpdump(vma, from, pfn, size,
 290                                                        prot);
 291 }
 292
 293 /*
 294  * Alloc memory and panic in case of ENOMEM
 295  */
 296 static void *kzalloc_panic(int len)
 297 {
 298         void *rc;
 299
 300         rc = kzalloc(len, GFP_KERNEL);
 301         if (!rc)
 302                 panic("s390 kdump kzalloc (%d) failed", len);
 303         return rc;
 304 }
 305
 306 /*
 307  * Initialize ELF note
 308  */
 309 static void *nt_init_name(void *buf, Elf64_Word type, void *desc, int d_len,
 310                           const char *name)
 311 {
 312         Elf64_Nhdr *note;
 313         u64 len;
 314
 315         note = (Elf64_Nhdr *)buf;
 316         note->n_namesz = strlen(name) + 1;
 317         note->n_descsz = d_len;
 318         note->n_type = type;
 319         len = sizeof(Elf64_Nhdr);
 320
 321         memcpy(buf + len, name, note->n_namesz);
 322         len = roundup(len + note->n_namesz, 4);
 323
 324         memcpy(buf + len, desc, note->n_descsz);
 325         len = roundup(len + note->n_descsz, 4);
 326
 327         return PTR_ADD(buf, len);
 328 }
 329
 330 static inline void *nt_init(void *buf, Elf64_Word type, void *desc, int d_len)
 331 {
 332         const char *note_name = "LINUX";
 333
 334         if (type == NT_PRPSINFO || type == NT_PRSTATUS || type == NT_PRFPREG)
 335                 note_name = KEXEC_CORE_NOTE_NAME;
 336         return nt_init_name(buf, type, desc, d_len, note_name);
 337 }
 338
 339 /*
 340  * Fill ELF notes for one CPU with save area registers
 341  */
 342 static void *fill_cpu_elf_notes(void *ptr, int cpu, struct save_area *sa)
 343 {
 344         struct elf_prstatus nt_prstatus;
 345         elf_fpregset_t nt_fpregset;
 346
 347         /* Prepare prstatus note */
 348         memset(&nt_prstatus, 0, sizeof(nt_prstatus));
 349         memcpy(&nt_prstatus.pr_reg.gprs, sa->gprs, sizeof(sa->gprs));
 350         memcpy(&nt_prstatus.pr_reg.psw, sa->psw, sizeof(sa->psw));
 351         memcpy(&nt_prstatus.pr_reg.acrs, sa->acrs, sizeof(sa->acrs));
 352         nt_prstatus.pr_pid = cpu;
 353         /* Prepare fpregset (floating point) note */
 354         memset(&nt_fpregset, 0, sizeof(nt_fpregset));
 355         memcpy(&nt_fpregset.fpc, &sa->fpc, sizeof(sa->fpc));
 356         memcpy(&nt_fpregset.fprs, &sa->fprs, sizeof(sa->fprs));
 357         /* Create ELF notes for the CPU */
 358         ptr = nt_init(ptr, NT_PRSTATUS, &nt_prstatus, sizeof(nt_prstatus));
 359         ptr = nt_init(ptr, NT_PRFPREG, &nt_fpregset, sizeof(nt_fpregset));
 360         ptr = nt_init(ptr, NT_S390_TIMER, &sa->timer, sizeof(sa->timer));
 361         ptr = nt_init(ptr, NT_S390_TODCMP, &sa->todcmp, sizeof(sa->todcmp));
 362         ptr = nt_init(ptr, NT_S390_TODPREG, &sa->todpreg, sizeof(sa->todpreg));
 363         ptr = nt_init(ptr, NT_S390_CTRS, &sa->ctrs, sizeof(sa->ctrs));
 364         ptr = nt_init(ptr, NT_S390_PREFIX, &sa->prefix, sizeof(sa->prefix));
 365         if (MACHINE_HAS_VX) {
 366                 ptr = nt_init(ptr, NT_S390_VXRS_HIGH,
 367                               &sa->vxrs_high, sizeof(sa->vxrs_high));
 368                 ptr = nt_init(ptr, NT_S390_VXRS_LOW,
 369                               &sa->vxrs_low, sizeof(sa->vxrs_low));
 370         }
 371         return ptr;
 372 }
 373
 374 /*
 375  * Initialize prpsinfo note (new kernel)
 376  */
 377 static void *nt_prpsinfo(void *ptr)
 378 {
 379         struct elf_prpsinfo prpsinfo;
 380
 381         memset(&prpsinfo, 0, sizeof(prpsinfo));
 382         prpsinfo.pr_sname = 'R';
 383         strcpy(prpsinfo.pr_fname, "vmlinux");
 384         return nt_init(ptr, NT_PRPSINFO, &prpsinfo, sizeof(prpsinfo));
 385 }
 386
 387 /*
 388  * Get vmcoreinfo using lowcore->vmcore_info (new kernel)
 389  */
 390 static void *get_vmcoreinfo_old(unsigned long *size)
 391 {
 392         char nt_name[11], *vmcoreinfo;
 393         Elf64_Nhdr note;
 394         void *addr;
 395
 396         if (copy_oldmem_kernel(&addr, &S390_lowcore.vmcore_info, sizeof(addr)))
 397                 return NULL;
 398         memset(nt_name, 0, sizeof(nt_name));
 399         if (copy_oldmem_kernel(&note, addr, sizeof(note)))
 400                 return NULL;
 401         if (copy_oldmem_kernel(nt_name, addr + sizeof(note),
 402                                sizeof(nt_name) - 1))
 403                 return NULL;
 404         if (strcmp(nt_name, VMCOREINFO_NOTE_NAME) != 0)
 405                 return NULL;
 406         vmcoreinfo = kzalloc_panic(note.n_descsz);
 407         if (copy_oldmem_kernel(vmcoreinfo, addr + 24, note.n_descsz)) {
 408                 kfree(vmcoreinfo);
 409                 return NULL;
 410         }
 411         *size = note.n_descsz;
 412         return vmcoreinfo;
 413 }
 414
 415 /*
 416  * Initialize vmcoreinfo note (new kernel)
 417  */
 418 static void *nt_vmcoreinfo(void *ptr)
 419 {
 420         const char *name = VMCOREINFO_NOTE_NAME;
 421         unsigned long size;
 422         void *vmcoreinfo;
 423
 424         vmcoreinfo = os_info_old_entry(OS_INFO_VMCOREINFO, &size);
 425         if (vmcoreinfo)
 426                 return nt_init_name(ptr, 0, vmcoreinfo, size, name);
 427
 428         vmcoreinfo = get_vmcoreinfo_old(&size);
 429         if (!vmcoreinfo)
 430                 return ptr;
 431         ptr = nt_init_name(ptr, 0, vmcoreinfo, size, name);
 432         kfree(vmcoreinfo);
 433         return ptr;
 434 }
 435
 436 /*
 437  * Initialize final note (needed for /proc/vmcore code)
 438  */
 439 static void *nt_final(void *ptr)
 440 {
 441         Elf64_Nhdr *note;
 442
 443         note = (Elf64_Nhdr *) ptr;
 444         note->n_namesz = 0;
 445         note->n_descsz = 0;
 446         note->n_type = 0;
 447         return PTR_ADD(ptr, sizeof(Elf64_Nhdr));
 448 }
 449
 450 /*
 451  * Initialize ELF header (new kernel)
 452  */
 453 static void *ehdr_init(Elf64_Ehdr *ehdr, int mem_chunk_cnt)
 454 {
 455         memset(ehdr, 0, sizeof(*ehdr));
 456         memcpy(ehdr->e_ident, ELFMAG, SELFMAG);
 457         ehdr->e_ident[EI_CLASS] = ELFCLASS64;
 458         ehdr->e_ident[EI_DATA] = ELFDATA2MSB;
 459         ehdr->e_ident[EI_VERSION] = EV_CURRENT;
 460         memset(ehdr->e_ident + EI_PAD, 0, EI_NIDENT - EI_PAD);
 461         ehdr->e_type = ET_CORE;
 462         ehdr->e_machine = EM_S390;
 463         ehdr->e_version = EV_CURRENT;
 464         ehdr->e_phoff = sizeof(Elf64_Ehdr);
 465         ehdr->e_ehsize = sizeof(Elf64_Ehdr);
 466         ehdr->e_phentsize = sizeof(Elf64_Phdr);
 467         ehdr->e_phnum = mem_chunk_cnt + 1;
 468         return ehdr + 1;
 469 }
 470
 471 /*
 472  * Return CPU count for ELF header (new kernel)
 473  */
 474 static int get_cpu_cnt(void)
 475 {
 476         struct save_area *sa;
 477         int cpus = 0;
 478
 479         list_for_each_entry(sa, &dump_save_areas, list)
 480                 if (sa->prefix != 0)
 481                         cpus++;
 482         return cpus;
 483 }
 484
 485 /*
 486  * Return memory chunk count for ELF header (new kernel)
 487  */
 488 static int get_mem_chunk_cnt(void)
 489 {
 490         int cnt = 0;
 491         u64 idx;
 492
 493         for_each_mem_range(idx, &memblock.physmem, &oldmem_type, NUMA_NO_NODE,
 494                            MEMBLOCK_NONE, NULL, NULL, NULL)
 495                 cnt++;
 496         return cnt;
 497 }
 498
 499 /*
 500  * Initialize ELF loads (new kernel)
 501  */
 502 static void loads_init(Elf64_Phdr *phdr, u64 loads_offset)
 503 {
 504         phys_addr_t start, end;
 505         u64 idx;
 506
 507         for_each_mem_range(idx, &memblock.physmem, &oldmem_type, NUMA_NO_NODE,
 508                            MEMBLOCK_NONE, &start, &end, NULL) {
 509                 phdr->p_filesz = end - start;
 510                 phdr->p_type = PT_LOAD;
 511                 phdr->p_offset = start;
 512                 phdr->p_vaddr = start;
 513                 phdr->p_paddr = start;
 514                 phdr->p_memsz = end - start;
 515                 phdr->p_flags = PF_R | PF_W | PF_X;
 516                 phdr->p_align = PAGE_SIZE;
 517                 phdr++;
 518         }
 519 }
 520
 521 /*
 522  * Initialize notes (new kernel)
 523  */
 524 static void *notes_init(Elf64_Phdr *phdr, void *ptr, u64 notes_offset)
 525 {
 526         struct save_area *sa;
 527         void *ptr_start = ptr;
 528         int cpu;
 529
 530         ptr = nt_prpsinfo(ptr);
 531
 532         cpu = 1;
 533         list_for_each_entry(sa, &dump_save_areas, list)
 534                 if (sa->prefix != 0)
 535                         ptr = fill_cpu_elf_notes(ptr, cpu++, sa);
 536         ptr = nt_vmcoreinfo(ptr);
 537         ptr = nt_final(ptr);
 538         memset(phdr, 0, sizeof(*phdr));
 539         phdr->p_type = PT_NOTE;
 540         phdr->p_offset = notes_offset;
 541         phdr->p_filesz = (unsigned long) PTR_SUB(ptr, ptr_start);
 542         phdr->p_memsz = phdr->p_filesz;
 543         return ptr;
 544 }
 545
 546 /*
 547  * Create ELF core header (new kernel)
 548  */
 549 int elfcorehdr_alloc(unsigned long long *addr, unsigned long long *size)
 550 {
 551         Elf64_Phdr *phdr_notes, *phdr_loads;
 552         int mem_chunk_cnt;
 553         void *ptr, *hdr;
 554         u32 alloc_size;
 555         u64 hdr_off;
 556
 557         /* If we are not in kdump or zfcpdump mode return */
 558         if (!OLDMEM_BASE && ipl_info.type != IPL_TYPE_FCP_DUMP)
 559                 return 0;
 560         /* If we cannot get HSA size for zfcpdump return error */
 561         if (ipl_info.type == IPL_TYPE_FCP_DUMP && !sclp.hsa_size)
 562                 return -ENODEV;
 563
 564         /* For kdump, exclude previous crashkernel memory */
 565         if (OLDMEM_BASE) {
 566                 oldmem_region.base = OLDMEM_BASE;
 567                 oldmem_region.size = OLDMEM_SIZE;
 568                 oldmem_type.total_size = OLDMEM_SIZE;
 569         }
 570
 571         mem_chunk_cnt = get_mem_chunk_cnt();
 572
 573         alloc_size = 0x1000 + get_cpu_cnt() * 0x4a0 +
 574                 mem_chunk_cnt * sizeof(Elf64_Phdr);
 575         hdr = kzalloc_panic(alloc_size);
 576         /* Init elf header */
 577         ptr = ehdr_init(hdr, mem_chunk_cnt);
 578         /* Init program headers */
 579         phdr_notes = ptr;
 580         ptr = PTR_ADD(ptr, sizeof(Elf64_Phdr));
 581         phdr_loads = ptr;
 582         ptr = PTR_ADD(ptr, sizeof(Elf64_Phdr) * mem_chunk_cnt);
 583         /* Init notes */
 584         hdr_off = PTR_DIFF(ptr, hdr);
 585         ptr = notes_init(phdr_notes, ptr, ((unsigned long) hdr) + hdr_off);
 586         /* Init loads */
 587         hdr_off = PTR_DIFF(ptr, hdr);
 588         loads_init(phdr_loads, hdr_off);
 589         *addr = (unsigned long long) hdr;
 590         *size = (unsigned long long) hdr_off;
 591         BUG_ON(elfcorehdr_size > alloc_size);
 592         return 0;
 593 }
 594
 595 /*
 596  * Free ELF core header (new kernel)
 597  */
 598 void elfcorehdr_free(unsigned long long addr)
 599 {
 600         kfree((void *)(unsigned long)addr);
 601 }
 602
 603 /*
 604  * Read from ELF header
 605  */
 606 ssize_t elfcorehdr_read(char *buf, size_t count, u64 *ppos)
 607 {
 608         void *src = (void *)(unsigned long)*ppos;
 609
 610         memcpy(buf, src, count);
 611         *ppos += count;
 612         return count;
 613 }
 614
 615 /*
 616  * Read from ELF notes data
 617  */
 618 ssize_t elfcorehdr_read_notes(char *buf, size_t count, u64 *ppos)
 619 {
 620         void *src = (void *)(unsigned long)*ppos;
 621
 622         memcpy(buf, src, count);
 623         *ppos += count;
 624         return count;
 625 }