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/memblock.h> 17 #include <linux/elf.h> 18 #include <linux/uio.h> 19 #include <asm/asm-offsets.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 static DEFINE_MUTEX(memcpy_real_mutex); 57 static char memcpy_real_buf[PAGE_SIZE]; 58 59 /* 60 * Allocate a save area 61 */ 62 struct save_area * __init save_area_alloc(bool is_boot_cpu) 63 { 64 struct save_area *sa; 65 66 sa = memblock_alloc(sizeof(*sa), 8); 67 if (!sa) 68 return NULL; 69 70 if (is_boot_cpu) 71 list_add(&sa->list, &dump_save_areas); 72 else 73 list_add_tail(&sa->list, &dump_save_areas); 74 return sa; 75 } 76 77 /* 78 * Return the address of the save area for the boot CPU 79 */ 80 struct save_area * __init save_area_boot_cpu(void) 81 { 82 return list_first_entry_or_null(&dump_save_areas, struct save_area, list); 83 } 84 85 /* 86 * Copy CPU registers into the save area 87 */ 88 void __init save_area_add_regs(struct save_area *sa, void *regs) 89 { 90 struct lowcore *lc; 91 92 lc = (struct lowcore *)(regs - __LC_FPREGS_SAVE_AREA); 93 memcpy(&sa->psw, &lc->psw_save_area, sizeof(sa->psw)); 94 memcpy(&sa->ctrs, &lc->cregs_save_area, sizeof(sa->ctrs)); 95 memcpy(&sa->gprs, &lc->gpregs_save_area, sizeof(sa->gprs)); 96 memcpy(&sa->acrs, &lc->access_regs_save_area, sizeof(sa->acrs)); 97 memcpy(&sa->fprs, &lc->floating_pt_save_area, sizeof(sa->fprs)); 98 memcpy(&sa->fpc, &lc->fpt_creg_save_area, sizeof(sa->fpc)); 99 memcpy(&sa->prefix, &lc->prefixreg_save_area, sizeof(sa->prefix)); 100 memcpy(&sa->todpreg, &lc->tod_progreg_save_area, sizeof(sa->todpreg)); 101 memcpy(&sa->timer, &lc->cpu_timer_save_area, sizeof(sa->timer)); 102 memcpy(&sa->todcmp, &lc->clock_comp_save_area, sizeof(sa->todcmp)); 103 } 104 105 /* 106 * Copy vector registers into the save area 107 */ 108 void __init save_area_add_vxrs(struct save_area *sa, __vector128 *vxrs) 109 { 110 int i; 111 112 /* Copy lower halves of vector registers 0-15 */ 113 for (i = 0; i < 16; i++) 114 memcpy(&sa->vxrs_low[i], &vxrs[i].u[2], 8); 115 /* Copy vector registers 16-31 */ 116 memcpy(sa->vxrs_high, vxrs + 16, 16 * sizeof(__vector128)); 117 } 118 119 static size_t copy_to_iter_real(struct iov_iter *iter, unsigned long src, size_t count) 120 { 121 size_t len, copied, res = 0; 122 123 mutex_lock(&memcpy_real_mutex); 124 while (count) { 125 len = min(PAGE_SIZE, count); 126 if (memcpy_real(memcpy_real_buf, src, len)) 127 break; 128 copied = copy_to_iter(memcpy_real_buf, len, iter); 129 count -= copied; 130 src += copied; 131 res += copied; 132 if (copied < len) 133 break; 134 } 135 mutex_unlock(&memcpy_real_mutex); 136 return res; 137 } 138 139 size_t copy_oldmem_iter(struct iov_iter *iter, unsigned long src, size_t count) 140 { 141 size_t len, copied, res = 0; 142 143 while (count) { 144 if (!oldmem_data.start && src < sclp.hsa_size) { 145 /* Copy from zfcp/nvme dump HSA area */ 146 len = min(count, sclp.hsa_size - src); 147 copied = memcpy_hsa_iter(iter, src, len); 148 } else { 149 /* Check for swapped kdump oldmem areas */ 150 if (oldmem_data.start && src - oldmem_data.start < oldmem_data.size) { 151 src -= oldmem_data.start; 152 len = min(count, oldmem_data.size - src); 153 } else if (oldmem_data.start && src < oldmem_data.size) { 154 len = min(count, oldmem_data.size - src); 155 src += oldmem_data.start; 156 } else { 157 len = count; 158 } 159 copied = copy_to_iter_real(iter, src, len); 160 } 161 count -= copied; 162 src += copied; 163 res += copied; 164 if (copied < len) 165 break; 166 } 167 return res; 168 } 169 170 /* 171 * Copy one page from "oldmem" 172 */ 173 ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn, size_t csize, 174 unsigned long offset) 175 { 176 unsigned long src; 177 178 src = pfn_to_phys(pfn) + offset; 179 return copy_oldmem_iter(iter, src, csize); 180 } 181 182 /* 183 * Remap "oldmem" for kdump 184 * 185 * For the kdump reserved memory this functions performs a swap operation: 186 * [0 - OLDMEM_SIZE] is mapped to [OLDMEM_BASE - OLDMEM_BASE + OLDMEM_SIZE] 187 */ 188 static int remap_oldmem_pfn_range_kdump(struct vm_area_struct *vma, 189 unsigned long from, unsigned long pfn, 190 unsigned long size, pgprot_t prot) 191 { 192 unsigned long size_old; 193 int rc; 194 195 if (pfn < oldmem_data.size >> PAGE_SHIFT) { 196 size_old = min(size, oldmem_data.size - (pfn << PAGE_SHIFT)); 197 rc = remap_pfn_range(vma, from, 198 pfn + (oldmem_data.start >> PAGE_SHIFT), 199 size_old, prot); 200 if (rc || size == size_old) 201 return rc; 202 size -= size_old; 203 from += size_old; 204 pfn += size_old >> PAGE_SHIFT; 205 } 206 return remap_pfn_range(vma, from, pfn, size, prot); 207 } 208 209 /* 210 * Remap "oldmem" for zfcp/nvme dump 211 * 212 * We only map available memory above HSA size. Memory below HSA size 213 * is read on demand using the copy_oldmem_page() function. 214 */ 215 static int remap_oldmem_pfn_range_zfcpdump(struct vm_area_struct *vma, 216 unsigned long from, 217 unsigned long pfn, 218 unsigned long size, pgprot_t prot) 219 { 220 unsigned long hsa_end = sclp.hsa_size; 221 unsigned long size_hsa; 222 223 if (pfn < hsa_end >> PAGE_SHIFT) { 224 size_hsa = min(size, hsa_end - (pfn << PAGE_SHIFT)); 225 if (size == size_hsa) 226 return 0; 227 size -= size_hsa; 228 from += size_hsa; 229 pfn += size_hsa >> PAGE_SHIFT; 230 } 231 return remap_pfn_range(vma, from, pfn, size, prot); 232 } 233 234 /* 235 * Remap "oldmem" for kdump or zfcp/nvme dump 236 */ 237 int remap_oldmem_pfn_range(struct vm_area_struct *vma, unsigned long from, 238 unsigned long pfn, unsigned long size, pgprot_t prot) 239 { 240 if (oldmem_data.start) 241 return remap_oldmem_pfn_range_kdump(vma, from, pfn, size, prot); 242 else 243 return remap_oldmem_pfn_range_zfcpdump(vma, from, pfn, size, 244 prot); 245 } 246 247 static const char *nt_name(Elf64_Word type) 248 { 249 const char *name = "LINUX"; 250 251 if (type == NT_PRPSINFO || type == NT_PRSTATUS || type == NT_PRFPREG) 252 name = KEXEC_CORE_NOTE_NAME; 253 return name; 254 } 255 256 /* 257 * Initialize ELF note 258 */ 259 static void *nt_init_name(void *buf, Elf64_Word type, void *desc, int d_len, 260 const char *name) 261 { 262 Elf64_Nhdr *note; 263 u64 len; 264 265 note = (Elf64_Nhdr *)buf; 266 note->n_namesz = strlen(name) + 1; 267 note->n_descsz = d_len; 268 note->n_type = type; 269 len = sizeof(Elf64_Nhdr); 270 271 memcpy(buf + len, name, note->n_namesz); 272 len = roundup(len + note->n_namesz, 4); 273 274 memcpy(buf + len, desc, note->n_descsz); 275 len = roundup(len + note->n_descsz, 4); 276 277 return PTR_ADD(buf, len); 278 } 279 280 static inline void *nt_init(void *buf, Elf64_Word type, void *desc, int d_len) 281 { 282 return nt_init_name(buf, type, desc, d_len, nt_name(type)); 283 } 284 285 /* 286 * Calculate the size of ELF note 287 */ 288 static size_t nt_size_name(int d_len, const char *name) 289 { 290 size_t size; 291 292 size = sizeof(Elf64_Nhdr); 293 size += roundup(strlen(name) + 1, 4); 294 size += roundup(d_len, 4); 295 296 return size; 297 } 298 299 static inline size_t nt_size(Elf64_Word type, int d_len) 300 { 301 return nt_size_name(d_len, nt_name(type)); 302 } 303 304 /* 305 * Fill ELF notes for one CPU with save area registers 306 */ 307 static void *fill_cpu_elf_notes(void *ptr, int cpu, struct save_area *sa) 308 { 309 struct elf_prstatus nt_prstatus; 310 elf_fpregset_t nt_fpregset; 311 312 /* Prepare prstatus note */ 313 memset(&nt_prstatus, 0, sizeof(nt_prstatus)); 314 memcpy(&nt_prstatus.pr_reg.gprs, sa->gprs, sizeof(sa->gprs)); 315 memcpy(&nt_prstatus.pr_reg.psw, sa->psw, sizeof(sa->psw)); 316 memcpy(&nt_prstatus.pr_reg.acrs, sa->acrs, sizeof(sa->acrs)); 317 nt_prstatus.common.pr_pid = cpu; 318 /* Prepare fpregset (floating point) note */ 319 memset(&nt_fpregset, 0, sizeof(nt_fpregset)); 320 memcpy(&nt_fpregset.fpc, &sa->fpc, sizeof(sa->fpc)); 321 memcpy(&nt_fpregset.fprs, &sa->fprs, sizeof(sa->fprs)); 322 /* Create ELF notes for the CPU */ 323 ptr = nt_init(ptr, NT_PRSTATUS, &nt_prstatus, sizeof(nt_prstatus)); 324 ptr = nt_init(ptr, NT_PRFPREG, &nt_fpregset, sizeof(nt_fpregset)); 325 ptr = nt_init(ptr, NT_S390_TIMER, &sa->timer, sizeof(sa->timer)); 326 ptr = nt_init(ptr, NT_S390_TODCMP, &sa->todcmp, sizeof(sa->todcmp)); 327 ptr = nt_init(ptr, NT_S390_TODPREG, &sa->todpreg, sizeof(sa->todpreg)); 328 ptr = nt_init(ptr, NT_S390_CTRS, &sa->ctrs, sizeof(sa->ctrs)); 329 ptr = nt_init(ptr, NT_S390_PREFIX, &sa->prefix, sizeof(sa->prefix)); 330 if (MACHINE_HAS_VX) { 331 ptr = nt_init(ptr, NT_S390_VXRS_HIGH, 332 &sa->vxrs_high, sizeof(sa->vxrs_high)); 333 ptr = nt_init(ptr, NT_S390_VXRS_LOW, 334 &sa->vxrs_low, sizeof(sa->vxrs_low)); 335 } 336 return ptr; 337 } 338 339 /* 340 * Calculate size of ELF notes per cpu 341 */ 342 static size_t get_cpu_elf_notes_size(void) 343 { 344 struct save_area *sa = NULL; 345 size_t size; 346 347 size = nt_size(NT_PRSTATUS, sizeof(struct elf_prstatus)); 348 size += nt_size(NT_PRFPREG, sizeof(elf_fpregset_t)); 349 size += nt_size(NT_S390_TIMER, sizeof(sa->timer)); 350 size += nt_size(NT_S390_TODCMP, sizeof(sa->todcmp)); 351 size += nt_size(NT_S390_TODPREG, sizeof(sa->todpreg)); 352 size += nt_size(NT_S390_CTRS, sizeof(sa->ctrs)); 353 size += nt_size(NT_S390_PREFIX, sizeof(sa->prefix)); 354 if (MACHINE_HAS_VX) { 355 size += nt_size(NT_S390_VXRS_HIGH, sizeof(sa->vxrs_high)); 356 size += nt_size(NT_S390_VXRS_LOW, sizeof(sa->vxrs_low)); 357 } 358 359 return size; 360 } 361 362 /* 363 * Initialize prpsinfo note (new kernel) 364 */ 365 static void *nt_prpsinfo(void *ptr) 366 { 367 struct elf_prpsinfo prpsinfo; 368 369 memset(&prpsinfo, 0, sizeof(prpsinfo)); 370 prpsinfo.pr_sname = 'R'; 371 strcpy(prpsinfo.pr_fname, "vmlinux"); 372 return nt_init(ptr, NT_PRPSINFO, &prpsinfo, sizeof(prpsinfo)); 373 } 374 375 /* 376 * Get vmcoreinfo using lowcore->vmcore_info (new kernel) 377 */ 378 static void *get_vmcoreinfo_old(unsigned long *size) 379 { 380 char nt_name[11], *vmcoreinfo; 381 unsigned long addr; 382 Elf64_Nhdr note; 383 384 if (copy_oldmem_kernel(&addr, __LC_VMCORE_INFO, sizeof(addr))) 385 return NULL; 386 memset(nt_name, 0, sizeof(nt_name)); 387 if (copy_oldmem_kernel(¬e, addr, sizeof(note))) 388 return NULL; 389 if (copy_oldmem_kernel(nt_name, addr + sizeof(note), 390 sizeof(nt_name) - 1)) 391 return NULL; 392 if (strcmp(nt_name, VMCOREINFO_NOTE_NAME) != 0) 393 return NULL; 394 vmcoreinfo = kzalloc(note.n_descsz, GFP_KERNEL); 395 if (!vmcoreinfo) 396 return NULL; 397 if (copy_oldmem_kernel(vmcoreinfo, addr + 24, note.n_descsz)) { 398 kfree(vmcoreinfo); 399 return NULL; 400 } 401 *size = note.n_descsz; 402 return vmcoreinfo; 403 } 404 405 /* 406 * Initialize vmcoreinfo note (new kernel) 407 */ 408 static void *nt_vmcoreinfo(void *ptr) 409 { 410 const char *name = VMCOREINFO_NOTE_NAME; 411 unsigned long size; 412 void *vmcoreinfo; 413 414 vmcoreinfo = os_info_old_entry(OS_INFO_VMCOREINFO, &size); 415 if (vmcoreinfo) 416 return nt_init_name(ptr, 0, vmcoreinfo, size, name); 417 418 vmcoreinfo = get_vmcoreinfo_old(&size); 419 if (!vmcoreinfo) 420 return ptr; 421 ptr = nt_init_name(ptr, 0, vmcoreinfo, size, name); 422 kfree(vmcoreinfo); 423 return ptr; 424 } 425 426 static size_t nt_vmcoreinfo_size(void) 427 { 428 const char *name = VMCOREINFO_NOTE_NAME; 429 unsigned long size; 430 void *vmcoreinfo; 431 432 vmcoreinfo = os_info_old_entry(OS_INFO_VMCOREINFO, &size); 433 if (vmcoreinfo) 434 return nt_size_name(size, name); 435 436 vmcoreinfo = get_vmcoreinfo_old(&size); 437 if (!vmcoreinfo) 438 return 0; 439 440 kfree(vmcoreinfo); 441 return nt_size_name(size, name); 442 } 443 444 /* 445 * Initialize final note (needed for /proc/vmcore code) 446 */ 447 static void *nt_final(void *ptr) 448 { 449 Elf64_Nhdr *note; 450 451 note = (Elf64_Nhdr *) ptr; 452 note->n_namesz = 0; 453 note->n_descsz = 0; 454 note->n_type = 0; 455 return PTR_ADD(ptr, sizeof(Elf64_Nhdr)); 456 } 457 458 /* 459 * Initialize ELF header (new kernel) 460 */ 461 static void *ehdr_init(Elf64_Ehdr *ehdr, int mem_chunk_cnt) 462 { 463 memset(ehdr, 0, sizeof(*ehdr)); 464 memcpy(ehdr->e_ident, ELFMAG, SELFMAG); 465 ehdr->e_ident[EI_CLASS] = ELFCLASS64; 466 ehdr->e_ident[EI_DATA] = ELFDATA2MSB; 467 ehdr->e_ident[EI_VERSION] = EV_CURRENT; 468 memset(ehdr->e_ident + EI_PAD, 0, EI_NIDENT - EI_PAD); 469 ehdr->e_type = ET_CORE; 470 ehdr->e_machine = EM_S390; 471 ehdr->e_version = EV_CURRENT; 472 ehdr->e_phoff = sizeof(Elf64_Ehdr); 473 ehdr->e_ehsize = sizeof(Elf64_Ehdr); 474 ehdr->e_phentsize = sizeof(Elf64_Phdr); 475 ehdr->e_phnum = mem_chunk_cnt + 1; 476 return ehdr + 1; 477 } 478 479 /* 480 * Return CPU count for ELF header (new kernel) 481 */ 482 static int get_cpu_cnt(void) 483 { 484 struct save_area *sa; 485 int cpus = 0; 486 487 list_for_each_entry(sa, &dump_save_areas, list) 488 if (sa->prefix != 0) 489 cpus++; 490 return cpus; 491 } 492 493 /* 494 * Return memory chunk count for ELF header (new kernel) 495 */ 496 static int get_mem_chunk_cnt(void) 497 { 498 int cnt = 0; 499 u64 idx; 500 501 for_each_physmem_range(idx, &oldmem_type, NULL, NULL) 502 cnt++; 503 return cnt; 504 } 505 506 /* 507 * Initialize ELF loads (new kernel) 508 */ 509 static void loads_init(Elf64_Phdr *phdr, u64 loads_offset) 510 { 511 phys_addr_t start, end; 512 u64 idx; 513 514 for_each_physmem_range(idx, &oldmem_type, &start, &end) { 515 phdr->p_filesz = end - start; 516 phdr->p_type = PT_LOAD; 517 phdr->p_offset = start; 518 phdr->p_vaddr = start; 519 phdr->p_paddr = start; 520 phdr->p_memsz = end - start; 521 phdr->p_flags = PF_R | PF_W | PF_X; 522 phdr->p_align = PAGE_SIZE; 523 phdr++; 524 } 525 } 526 527 /* 528 * Initialize notes (new kernel) 529 */ 530 static void *notes_init(Elf64_Phdr *phdr, void *ptr, u64 notes_offset) 531 { 532 struct save_area *sa; 533 void *ptr_start = ptr; 534 int cpu; 535 536 ptr = nt_prpsinfo(ptr); 537 538 cpu = 1; 539 list_for_each_entry(sa, &dump_save_areas, list) 540 if (sa->prefix != 0) 541 ptr = fill_cpu_elf_notes(ptr, cpu++, sa); 542 ptr = nt_vmcoreinfo(ptr); 543 ptr = nt_final(ptr); 544 memset(phdr, 0, sizeof(*phdr)); 545 phdr->p_type = PT_NOTE; 546 phdr->p_offset = notes_offset; 547 phdr->p_filesz = (unsigned long) PTR_SUB(ptr, ptr_start); 548 phdr->p_memsz = phdr->p_filesz; 549 return ptr; 550 } 551 552 static size_t get_elfcorehdr_size(int mem_chunk_cnt) 553 { 554 size_t size; 555 556 size = sizeof(Elf64_Ehdr); 557 /* PT_NOTES */ 558 size += sizeof(Elf64_Phdr); 559 /* nt_prpsinfo */ 560 size += nt_size(NT_PRPSINFO, sizeof(struct elf_prpsinfo)); 561 /* regsets */ 562 size += get_cpu_cnt() * get_cpu_elf_notes_size(); 563 /* nt_vmcoreinfo */ 564 size += nt_vmcoreinfo_size(); 565 /* nt_final */ 566 size += sizeof(Elf64_Nhdr); 567 /* PT_LOADS */ 568 size += mem_chunk_cnt * sizeof(Elf64_Phdr); 569 570 return size; 571 } 572 573 /* 574 * Create ELF core header (new kernel) 575 */ 576 int elfcorehdr_alloc(unsigned long long *addr, unsigned long long *size) 577 { 578 Elf64_Phdr *phdr_notes, *phdr_loads; 579 int mem_chunk_cnt; 580 void *ptr, *hdr; 581 u32 alloc_size; 582 u64 hdr_off; 583 584 /* If we are not in kdump or zfcp/nvme dump mode return */ 585 if (!oldmem_data.start && !is_ipl_type_dump()) 586 return 0; 587 /* If we cannot get HSA size for zfcp/nvme dump return error */ 588 if (is_ipl_type_dump() && !sclp.hsa_size) 589 return -ENODEV; 590 591 /* For kdump, exclude previous crashkernel memory */ 592 if (oldmem_data.start) { 593 oldmem_region.base = oldmem_data.start; 594 oldmem_region.size = oldmem_data.size; 595 oldmem_type.total_size = oldmem_data.size; 596 } 597 598 mem_chunk_cnt = get_mem_chunk_cnt(); 599 600 alloc_size = get_elfcorehdr_size(mem_chunk_cnt); 601 602 hdr = kzalloc(alloc_size, GFP_KERNEL); 603 604 /* Without elfcorehdr /proc/vmcore cannot be created. Thus creating 605 * a dump with this crash kernel will fail. Panic now to allow other 606 * dump mechanisms to take over. 607 */ 608 if (!hdr) 609 panic("s390 kdump allocating elfcorehdr failed"); 610 611 /* Init elf header */ 612 ptr = ehdr_init(hdr, mem_chunk_cnt); 613 /* Init program headers */ 614 phdr_notes = ptr; 615 ptr = PTR_ADD(ptr, sizeof(Elf64_Phdr)); 616 phdr_loads = ptr; 617 ptr = PTR_ADD(ptr, sizeof(Elf64_Phdr) * mem_chunk_cnt); 618 /* Init notes */ 619 hdr_off = PTR_DIFF(ptr, hdr); 620 ptr = notes_init(phdr_notes, ptr, ((unsigned long) hdr) + hdr_off); 621 /* Init loads */ 622 hdr_off = PTR_DIFF(ptr, hdr); 623 loads_init(phdr_loads, hdr_off); 624 *addr = (unsigned long long) hdr; 625 *size = (unsigned long long) hdr_off; 626 BUG_ON(elfcorehdr_size > alloc_size); 627 return 0; 628 } 629 630 /* 631 * Free ELF core header (new kernel) 632 */ 633 void elfcorehdr_free(unsigned long long addr) 634 { 635 kfree((void *)(unsigned long)addr); 636 } 637 638 /* 639 * Read from ELF header 640 */ 641 ssize_t elfcorehdr_read(char *buf, size_t count, u64 *ppos) 642 { 643 void *src = (void *)(unsigned long)*ppos; 644 645 memcpy(buf, src, count); 646 *ppos += count; 647 return count; 648 } 649 650 /* 651 * Read from ELF notes data 652 */ 653 ssize_t elfcorehdr_read_notes(char *buf, size_t count, u64 *ppos) 654 { 655 void *src = (void *)(unsigned long)*ppos; 656 657 memcpy(buf, src, count); 658 *ppos += count; 659 return count; 660 } 661