arch/s390/kernel/crash_dump.c

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