arch/s390/kernel/crash_dump.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * S390 kdump implementation
   4  *
   5  * Copyright IBM Corp. 2011
   6  * Author(s): Michael Holzheu <holzheu@linux.vnet.ibm.com>
   7  */
   8
   9 #include <linux/crash_dump.h>
  10 #include <asm/lowcore.h>
  11 #include <linux/kernel.h>
  12 #include <linux/init.h>
  13 #include <linux/mm.h>
  14 #include <linux/gfp.h>
  15 #include <linux/slab.h>
  16 #include <linux/bootmem.h>
  17 #include <linux/elf.h>
  18 #include <asm/asm-offsets.h>
  19 #include <linux/memblock.h>
  20 #include <asm/os_info.h>
  21 #include <asm/elf.h>
  22 #include <asm/ipl.h>
  23 #include <asm/sclp.h>
  24
  25 #define PTR_ADD(x, y) (((char *) (x)) + ((unsigned long) (y)))
  26 #define PTR_SUB(x, y) (((char *) (x)) - ((unsigned long) (y)))
  27 #define PTR_DIFF(x, y) ((unsigned long)(((char *) (x)) - ((unsigned long) (y))))
  28
  29 static struct memblock_region oldmem_region;
  30
  31 static struct memblock_type oldmem_type = {
  32         .cnt = 1,
  33         .max = 1,
  34         .total_size = 0,
  35         .regions = &oldmem_region,
  36         .name = "oldmem",
  37 };
  38
  39 struct save_area {
  40         struct list_head list;
  41         u64 psw[2];
  42         u64 ctrs[16];
  43         u64 gprs[16];
  44         u32 acrs[16];
  45         u64 fprs[16];
  46         u32 fpc;
  47         u32 prefix;
  48         u64 todpreg;
  49         u64 timer;
  50         u64 todcmp;
  51         u64 vxrs_low[16];
  52         __vector128 vxrs_high[16];
  53 };
  54
  55 static LIST_HEAD(dump_save_areas);
  56
  57 /*
  58  * Allocate a save area
  59  */
  60 struct save_area * __init save_area_alloc(bool is_boot_cpu)
  61 {
  62         struct save_area *sa;
  63
  64         sa = (void *) memblock_alloc(sizeof(*sa), 8);
  65         if (is_boot_cpu)
  66                 list_add(&sa->list, &dump_save_areas);
  67         else
  68                 list_add_tail(&sa->list, &dump_save_areas);
  69         return sa;
  70 }
  71
  72 /*
  73  * Return the address of the save area for the boot CPU
  74  */
  75 struct save_area * __init save_area_boot_cpu(void)
  76 {
  77         return list_first_entry_or_null(&dump_save_areas, struct save_area, list);
  78 }
  79
  80 /*
  81  * Copy CPU registers into the save area
  82  */
  83 void __init save_area_add_regs(struct save_area *sa, void *regs)
  84 {
  85         struct lowcore *lc;
  86
  87         lc = (struct lowcore *)(regs - __LC_FPREGS_SAVE_AREA);
  88         memcpy(&sa->psw, &lc->psw_save_area, sizeof(sa->psw));
  89         memcpy(&sa->ctrs, &lc->cregs_save_area, sizeof(sa->ctrs));
  90         memcpy(&sa->gprs, &lc->gpregs_save_area, sizeof(sa->gprs));
  91         memcpy(&sa->acrs, &lc->access_regs_save_area, sizeof(sa->acrs));
  92         memcpy(&sa->fprs, &lc->floating_pt_save_area, sizeof(sa->fprs));
  93         memcpy(&sa->fpc, &lc->fpt_creg_save_area, sizeof(sa->fpc));
  94         memcpy(&sa->prefix, &lc->prefixreg_save_area, sizeof(sa->prefix));
  95         memcpy(&sa->todpreg, &lc->tod_progreg_save_area, sizeof(sa->todpreg));
  96         memcpy(&sa->timer, &lc->cpu_timer_save_area, sizeof(sa->timer));
  97         memcpy(&sa->todcmp, &lc->clock_comp_save_area, sizeof(sa->todcmp));
  98 }
  99
 100 /*
 101  * Copy vector registers into the save area
 102  */
 103 void __init save_area_add_vxrs(struct save_area *sa, __vector128 *vxrs)
 104 {
 105         int i;
 106
 107         /* Copy lower halves of vector registers 0-15 */
 108         for (i = 0; i < 16; i++)
 109                 memcpy(&sa->vxrs_low[i], &vxrs[i].u[2], 8);
 110         /* Copy vector registers 16-31 */
 111         memcpy(sa->vxrs_high, vxrs + 16, 16 * sizeof(__vector128));
 112 }
 113
 114 /*
 115  * Return physical address for virtual address
 116  */
 117 static inline void *load_real_addr(void *addr)
 118 {
 119         unsigned long real_addr;
 120
 121         asm volatile(
 122                    "    lra     %0,0(%1)\n"
 123                    "    jz      0f\n"
 124                    "    la      %0,0\n"
 125                    "0:"
 126                    : "=a" (real_addr) : "a" (addr) : "cc");
 127         return (void *)real_addr;
 128 }
 129
 130 /*
 131  * Copy memory of the old, dumped system to a kernel space virtual address
 132  */
 133 int copy_oldmem_kernel(void *dst, void *src, size_t count)
 134 {
 135         unsigned long from, len;
 136         void *ra;
 137         int rc;
 138
 139         while (count) {
 140                 from = __pa(src);
 141                 if (!OLDMEM_BASE && from < sclp.hsa_size) {
 142                         /* Copy from zfcpdump HSA area */
 143                         len = min(count, sclp.hsa_size - from);
 144                         rc = memcpy_hsa_kernel(dst, from, len);
 145                         if (rc)
 146                                 return rc;
 147                 } else {
 148                         /* Check for swapped kdump oldmem areas */
 149                         if (OLDMEM_BASE && from - OLDMEM_BASE < OLDMEM_SIZE) {
 150                                 from -= OLDMEM_BASE;
 151                                 len = min(count, OLDMEM_SIZE - from);
 152                         } else if (OLDMEM_BASE && from < OLDMEM_SIZE) {
 153                                 len = min(count, OLDMEM_SIZE - from);
 154                                 from += OLDMEM_BASE;
 155                         } else {
 156                                 len = count;
 157                         }
 158                         if (is_vmalloc_or_module_addr(dst)) {
 159                                 ra = load_real_addr(dst);
 160                                 len = min(PAGE_SIZE - offset_in_page(ra), len);
 161                         } else {
 162                                 ra = dst;
 163                         }
 164                         if (memcpy_real(ra, (void *) from, len))
 165                                 return -EFAULT;
 166                 }
 167                 dst += len;
 168                 src += len;
 169                 count -= len;
 170         }
 171         return 0;
 172 }
 173
 174 /*
 175  * Copy memory of the old, dumped system to a user space virtual address
 176  */
 177 static int copy_oldmem_user(void __user *dst, void *src, size_t count)
 178 {
 179         unsigned long from, len;
 180         int rc;
 181
 182         while (count) {
 183                 from = __pa(src);
 184                 if (!OLDMEM_BASE && from < sclp.hsa_size) {
 185                         /* Copy from zfcpdump HSA area */
 186                         len = min(count, sclp.hsa_size - from);
 187                         rc = memcpy_hsa_user(dst, from, len);
 188                         if (rc)
 189                                 return rc;
 190                 } else {
 191                         /* Check for swapped kdump oldmem areas */
 192                         if (OLDMEM_BASE && from - OLDMEM_BASE < OLDMEM_SIZE) {
 193                                 from -= OLDMEM_BASE;
 194                                 len = min(count, OLDMEM_SIZE - from);
 195                         } else if (OLDMEM_BASE && from < OLDMEM_SIZE) {
 196                                 len = min(count, OLDMEM_SIZE - from);
 197                                 from += OLDMEM_BASE;
 198                         } else {
 199                                 len = count;
 200                         }
 201                         rc = copy_to_user_real(dst, (void *) from, count);
 202                         if (rc)
 203                                 return rc;
 204                 }
 205                 dst += len;
 206                 src += len;
 207                 count -= len;
 208         }
 209         return 0;
 210 }
 211
 212 /*
 213  * Copy one page from "oldmem"
 214  */
 215 ssize_t copy_oldmem_page(unsigned long pfn, char *buf, size_t csize,
 216                          unsigned long offset, int userbuf)
 217 {
 218         void *src;
 219         int rc;
 220
 221         if (!csize)
 222                 return 0;
 223         src = (void *) (pfn << PAGE_SHIFT) + offset;
 224         if (userbuf)
 225                 rc = copy_oldmem_user((void __force __user *) buf, src, csize);
 226         else
 227                 rc = copy_oldmem_kernel((void *) buf, src, csize);
 228         return rc;
 229 }
 230
 231 /*
 232  * Remap "oldmem" for kdump
 233  *
 234  * For the kdump reserved memory this functions performs a swap operation:
 235  * [0 - OLDMEM_SIZE] is mapped to [OLDMEM_BASE - OLDMEM_BASE + OLDMEM_SIZE]
 236  */
 237 static int remap_oldmem_pfn_range_kdump(struct vm_area_struct *vma,
 238                                         unsigned long from, unsigned long pfn,
 239                                         unsigned long size, pgprot_t prot)
 240 {
 241         unsigned long size_old;
 242         int rc;
 243
 244         if (pfn < OLDMEM_SIZE >> PAGE_SHIFT) {
 245                 size_old = min(size, OLDMEM_SIZE - (pfn << PAGE_SHIFT));
 246                 rc = remap_pfn_range(vma, from,
 247                                      pfn + (OLDMEM_BASE >> PAGE_SHIFT),
 248                                      size_old, prot);
 249                 if (rc || size == size_old)
 250                         return rc;
 251                 size -= size_old;
 252                 from += size_old;
 253                 pfn += size_old >> PAGE_SHIFT;
 254         }
 255         return remap_pfn_range(vma, from, pfn, size, prot);
 256 }
 257
 258 /*
 259  * Remap "oldmem" for zfcpdump
 260  *
 261  * We only map available memory above HSA size. Memory below HSA size
 262  * is read on demand using the copy_oldmem_page() function.
 263  */
 264 static int remap_oldmem_pfn_range_zfcpdump(struct vm_area_struct *vma,
 265                                            unsigned long from,
 266                                            unsigned long pfn,
 267                                            unsigned long size, pgprot_t prot)
 268 {
 269         unsigned long hsa_end = sclp.hsa_size;
 270         unsigned long size_hsa;
 271
 272         if (pfn < hsa_end >> PAGE_SHIFT) {
 273                 size_hsa = min(size, hsa_end - (pfn << PAGE_SHIFT));
 274                 if (size == size_hsa)
 275                         return 0;
 276                 size -= size_hsa;
 277                 from += size_hsa;
 278                 pfn += size_hsa >> PAGE_SHIFT;
 279         }
 280         return remap_pfn_range(vma, from, pfn, size, prot);
 281 }
 282
 283 /*
 284  * Remap "oldmem" for kdump or zfcpdump
 285  */
 286 int remap_oldmem_pfn_range(struct vm_area_struct *vma, unsigned long from,
 287                            unsigned long pfn, unsigned long size, pgprot_t prot)
 288 {
 289         if (OLDMEM_BASE)
 290                 return remap_oldmem_pfn_range_kdump(vma, from, pfn, size, prot);
 291         else
 292                 return remap_oldmem_pfn_range_zfcpdump(vma, from, pfn, size,
 293                                                        prot);
 294 }
 295
 296 /*
 297  * Alloc memory and panic in case of ENOMEM
 298  */
 299 static void *kzalloc_panic(int len)
 300 {
 301         void *rc;
 302
 303         rc = kzalloc(len, GFP_KERNEL);
 304         if (!rc)
 305                 panic("s390 kdump kzalloc (%d) failed", len);
 306         return rc;
 307 }
 308
 309 /*
 310  * Initialize ELF note
 311  */
 312 static void *nt_init_name(void *buf, Elf64_Word type, void *desc, int d_len,
 313                           const char *name)
 314 {
 315         Elf64_Nhdr *note;
 316         u64 len;
 317
 318         note = (Elf64_Nhdr *)buf;
 319         note->n_namesz = strlen(name) + 1;
 320         note->n_descsz = d_len;
 321         note->n_type = type;
 322         len = sizeof(Elf64_Nhdr);
 323
 324         memcpy(buf + len, name, note->n_namesz);
 325         len = roundup(len + note->n_namesz, 4);
 326
 327         memcpy(buf + len, desc, note->n_descsz);
 328         len = roundup(len + note->n_descsz, 4);
 329
 330         return PTR_ADD(buf, len);
 331 }
 332
 333 static inline void *nt_init(void *buf, Elf64_Word type, void *desc, int d_len)
 334 {
 335         const char *note_name = "LINUX";
 336
 337         if (type == NT_PRPSINFO || type == NT_PRSTATUS || type == NT_PRFPREG)
 338                 note_name = KEXEC_CORE_NOTE_NAME;
 339         return nt_init_name(buf, type, desc, d_len, note_name);
 340 }
 341
 342 /*
 343  * Fill ELF notes for one CPU with save area registers
 344  */
 345 static void *fill_cpu_elf_notes(void *ptr, int cpu, struct save_area *sa)
 346 {
 347         struct elf_prstatus nt_prstatus;
 348         elf_fpregset_t nt_fpregset;
 349
 350         /* Prepare prstatus note */
 351         memset(&nt_prstatus, 0, sizeof(nt_prstatus));
 352         memcpy(&nt_prstatus.pr_reg.gprs, sa->gprs, sizeof(sa->gprs));
 353         memcpy(&nt_prstatus.pr_reg.psw, sa->psw, sizeof(sa->psw));
 354         memcpy(&nt_prstatus.pr_reg.acrs, sa->acrs, sizeof(sa->acrs));
 355         nt_prstatus.pr_pid = cpu;
 356         /* Prepare fpregset (floating point) note */
 357         memset(&nt_fpregset, 0, sizeof(nt_fpregset));
 358         memcpy(&nt_fpregset.fpc, &sa->fpc, sizeof(sa->fpc));
 359         memcpy(&nt_fpregset.fprs, &sa->fprs, sizeof(sa->fprs));
 360         /* Create ELF notes for the CPU */
 361         ptr = nt_init(ptr, NT_PRSTATUS, &nt_prstatus, sizeof(nt_prstatus));
 362         ptr = nt_init(ptr, NT_PRFPREG, &nt_fpregset, sizeof(nt_fpregset));
 363         ptr = nt_init(ptr, NT_S390_TIMER, &sa->timer, sizeof(sa->timer));
 364         ptr = nt_init(ptr, NT_S390_TODCMP, &sa->todcmp, sizeof(sa->todcmp));
 365         ptr = nt_init(ptr, NT_S390_TODPREG, &sa->todpreg, sizeof(sa->todpreg));
 366         ptr = nt_init(ptr, NT_S390_CTRS, &sa->ctrs, sizeof(sa->ctrs));
 367         ptr = nt_init(ptr, NT_S390_PREFIX, &sa->prefix, sizeof(sa->prefix));
 368         if (MACHINE_HAS_VX) {
 369                 ptr = nt_init(ptr, NT_S390_VXRS_HIGH,
 370                               &sa->vxrs_high, sizeof(sa->vxrs_high));
 371                 ptr = nt_init(ptr, NT_S390_VXRS_LOW,
 372                               &sa->vxrs_low, sizeof(sa->vxrs_low));
 373         }
 374         return ptr;
 375 }
 376
 377 /*
 378  * Initialize prpsinfo note (new kernel)
 379  */
 380 static void *nt_prpsinfo(void *ptr)
 381 {
 382         struct elf_prpsinfo prpsinfo;
 383
 384         memset(&prpsinfo, 0, sizeof(prpsinfo));
 385         prpsinfo.pr_sname = 'R';
 386         strcpy(prpsinfo.pr_fname, "vmlinux");
 387         return nt_init(ptr, NT_PRPSINFO, &prpsinfo, sizeof(prpsinfo));
 388 }
 389
 390 /*
 391  * Get vmcoreinfo using lowcore->vmcore_info (new kernel)
 392  */
 393 static void *get_vmcoreinfo_old(unsigned long *size)
 394 {
 395         char nt_name[11], *vmcoreinfo;
 396         Elf64_Nhdr note;
 397         void *addr;
 398
 399         if (copy_oldmem_kernel(&addr, &S390_lowcore.vmcore_info, sizeof(addr)))
 400                 return NULL;
 401         memset(nt_name, 0, sizeof(nt_name));
 402         if (copy_oldmem_kernel(&note, addr, sizeof(note)))
 403                 return NULL;
 404         if (copy_oldmem_kernel(nt_name, addr + sizeof(note),
 405                                sizeof(nt_name) - 1))
 406                 return NULL;
 407         if (strcmp(nt_name, "VMCOREINFO") != 0)
 408                 return NULL;
 409         vmcoreinfo = kzalloc_panic(note.n_descsz);
 410         if (copy_oldmem_kernel(vmcoreinfo, addr + 24, note.n_descsz))
 411                 return NULL;
 412         *size = note.n_descsz;
 413         return vmcoreinfo;
 414 }
 415
 416 /*
 417  * Initialize vmcoreinfo note (new kernel)
 418  */
 419 static void *nt_vmcoreinfo(void *ptr)
 420 {
 421         unsigned long size;
 422         void *vmcoreinfo;
 423
 424         vmcoreinfo = os_info_old_entry(OS_INFO_VMCOREINFO, &size);
 425         if (!vmcoreinfo)
 426                 vmcoreinfo = get_vmcoreinfo_old(&size);
 427         if (!vmcoreinfo)
 428                 return ptr;
 429         return nt_init_name(ptr, 0, vmcoreinfo, size, "VMCOREINFO");
 430 }
 431
 432 /*
 433  * Initialize final note (needed for /proc/vmcore code)
 434  */
 435 static void *nt_final(void *ptr)
 436 {
 437         Elf64_Nhdr *note;
 438
 439         note = (Elf64_Nhdr *) ptr;
 440         note->n_namesz = 0;
 441         note->n_descsz = 0;
 442         note->n_type = 0;
 443         return PTR_ADD(ptr, sizeof(Elf64_Nhdr));
 444 }
 445
 446 /*
 447  * Initialize ELF header (new kernel)
 448  */
 449 static void *ehdr_init(Elf64_Ehdr *ehdr, int mem_chunk_cnt)
 450 {
 451         memset(ehdr, 0, sizeof(*ehdr));
 452         memcpy(ehdr->e_ident, ELFMAG, SELFMAG);
 453         ehdr->e_ident[EI_CLASS] = ELFCLASS64;
 454         ehdr->e_ident[EI_DATA] = ELFDATA2MSB;
 455         ehdr->e_ident[EI_VERSION] = EV_CURRENT;
 456         memset(ehdr->e_ident + EI_PAD, 0, EI_NIDENT - EI_PAD);
 457         ehdr->e_type = ET_CORE;
 458         ehdr->e_machine = EM_S390;
 459         ehdr->e_version = EV_CURRENT;
 460         ehdr->e_phoff = sizeof(Elf64_Ehdr);
 461         ehdr->e_ehsize = sizeof(Elf64_Ehdr);
 462         ehdr->e_phentsize = sizeof(Elf64_Phdr);
 463         ehdr->e_phnum = mem_chunk_cnt + 1;
 464         return ehdr + 1;
 465 }
 466
 467 /*
 468  * Return CPU count for ELF header (new kernel)
 469  */
 470 static int get_cpu_cnt(void)
 471 {
 472         struct save_area *sa;
 473         int cpus = 0;
 474
 475         list_for_each_entry(sa, &dump_save_areas, list)
 476                 if (sa->prefix != 0)
 477                         cpus++;
 478         return cpus;
 479 }
 480
 481 /*
 482  * Return memory chunk count for ELF header (new kernel)
 483  */
 484 static int get_mem_chunk_cnt(void)
 485 {
 486         int cnt = 0;
 487         u64 idx;
 488
 489         for_each_mem_range(idx, &memblock.physmem, &oldmem_type, NUMA_NO_NODE,
 490                            MEMBLOCK_NONE, NULL, NULL, NULL)
 491                 cnt++;
 492         return cnt;
 493 }
 494
 495 /*
 496  * Initialize ELF loads (new kernel)
 497  */
 498 static void loads_init(Elf64_Phdr *phdr, u64 loads_offset)
 499 {
 500         phys_addr_t start, end;
 501         u64 idx;
 502
 503         for_each_mem_range(idx, &memblock.physmem, &oldmem_type, NUMA_NO_NODE,
 504                            MEMBLOCK_NONE, &start, &end, NULL) {
 505                 phdr->p_filesz = end - start;
 506                 phdr->p_type = PT_LOAD;
 507                 phdr->p_offset = start;
 508                 phdr->p_vaddr = start;
 509                 phdr->p_paddr = start;
 510                 phdr->p_memsz = end - start;
 511                 phdr->p_flags = PF_R | PF_W | PF_X;
 512                 phdr->p_align = PAGE_SIZE;
 513                 phdr++;
 514         }
 515 }
 516
 517 /*
 518  * Initialize notes (new kernel)
 519  */
 520 static void *notes_init(Elf64_Phdr *phdr, void *ptr, u64 notes_offset)
 521 {
 522         struct save_area *sa;
 523         void *ptr_start = ptr;
 524         int cpu;
 525
 526         ptr = nt_prpsinfo(ptr);
 527
 528         cpu = 1;
 529         list_for_each_entry(sa, &dump_save_areas, list)
 530                 if (sa->prefix != 0)
 531                         ptr = fill_cpu_elf_notes(ptr, cpu++, sa);
 532         ptr = nt_vmcoreinfo(ptr);
 533         ptr = nt_final(ptr);
 534         memset(phdr, 0, sizeof(*phdr));
 535         phdr->p_type = PT_NOTE;
 536         phdr->p_offset = notes_offset;
 537         phdr->p_filesz = (unsigned long) PTR_SUB(ptr, ptr_start);
 538         phdr->p_memsz = phdr->p_filesz;
 539         return ptr;
 540 }
 541
 542 /*
 543  * Create ELF core header (new kernel)
 544  */
 545 int elfcorehdr_alloc(unsigned long long *addr, unsigned long long *size)
 546 {
 547         Elf64_Phdr *phdr_notes, *phdr_loads;
 548         int mem_chunk_cnt;
 549         void *ptr, *hdr;
 550         u32 alloc_size;
 551         u64 hdr_off;
 552
 553         /* If we are not in kdump or zfcpdump mode return */
 554         if (!OLDMEM_BASE && ipl_info.type != IPL_TYPE_FCP_DUMP)
 555                 return 0;
 556         /* If we cannot get HSA size for zfcpdump return error */
 557         if (ipl_info.type == IPL_TYPE_FCP_DUMP && !sclp.hsa_size)
 558                 return -ENODEV;
 559
 560         /* For kdump, exclude previous crashkernel memory */
 561         if (OLDMEM_BASE) {
 562                 oldmem_region.base = OLDMEM_BASE;
 563                 oldmem_region.size = OLDMEM_SIZE;
 564                 oldmem_type.total_size = OLDMEM_SIZE;
 565         }
 566
 567         mem_chunk_cnt = get_mem_chunk_cnt();
 568
 569         alloc_size = 0x1000 + get_cpu_cnt() * 0x4a0 +
 570                 mem_chunk_cnt * sizeof(Elf64_Phdr);
 571         hdr = kzalloc_panic(alloc_size);
 572         /* Init elf header */
 573         ptr = ehdr_init(hdr, mem_chunk_cnt);
 574         /* Init program headers */
 575         phdr_notes = ptr;
 576         ptr = PTR_ADD(ptr, sizeof(Elf64_Phdr));
 577         phdr_loads = ptr;
 578         ptr = PTR_ADD(ptr, sizeof(Elf64_Phdr) * mem_chunk_cnt);
 579         /* Init notes */
 580         hdr_off = PTR_DIFF(ptr, hdr);
 581         ptr = notes_init(phdr_notes, ptr, ((unsigned long) hdr) + hdr_off);
 582         /* Init loads */
 583         hdr_off = PTR_DIFF(ptr, hdr);
 584         loads_init(phdr_loads, hdr_off);
 585         *addr = (unsigned long long) hdr;
 586         *size = (unsigned long long) hdr_off;
 587         BUG_ON(elfcorehdr_size > alloc_size);
 588         return 0;
 589 }
 590
 591 /*
 592  * Free ELF core header (new kernel)
 593  */
 594 void elfcorehdr_free(unsigned long long addr)
 595 {
 596         kfree((void *)(unsigned long)addr);
 597 }
 598
 599 /*
 600  * Read from ELF header
 601  */
 602 ssize_t elfcorehdr_read(char *buf, size_t count, u64 *ppos)
 603 {
 604         void *src = (void *)(unsigned long)*ppos;
 605
 606         memcpy(buf, src, count);
 607         *ppos += count;
 608         return count;
 609 }
 610
 611 /*
 612  * Read from ELF notes data
 613  */
 614 ssize_t elfcorehdr_read_notes(char *buf, size_t count, u64 *ppos)
 615 {
 616         void *src = (void *)(unsigned long)*ppos;
 617
 618         memcpy(buf, src, count);
 619         *ppos += count;
 620         return count;
 621 }