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 */
save_area_alloc(bool is_boot_cpu)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 */
save_area_boot_cpu(void)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 */
save_area_add_regs(struct save_area * sa,void * regs)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 */
save_area_add_vxrs(struct save_area * sa,__vector128 * vxrs)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 */
load_real_addr(void * addr)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 */
copy_oldmem_kernel(void * dst,void * src,size_t count)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 */
copy_oldmem_user(void __user * dst,void * src,size_t count)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 */
copy_oldmem_page(unsigned long pfn,char * buf,size_t csize,unsigned long offset,int userbuf)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 */
remap_oldmem_pfn_range_kdump(struct vm_area_struct * vma,unsigned long from,unsigned long pfn,unsigned long size,pgprot_t prot)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 */
remap_oldmem_pfn_range_zfcpdump(struct vm_area_struct * vma,unsigned long from,unsigned long pfn,unsigned long size,pgprot_t prot)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 */
remap_oldmem_pfn_range(struct vm_area_struct * vma,unsigned long from,unsigned long pfn,unsigned long size,pgprot_t prot)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 */
kzalloc_panic(int len)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 */
nt_init_name(void * buf,Elf64_Word type,void * desc,int d_len,const char * name)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
nt_init(void * buf,Elf64_Word type,void * desc,int d_len)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 */
fill_cpu_elf_notes(void * ptr,int cpu,struct save_area * sa)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 */
nt_prpsinfo(void * ptr)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 */
get_vmcoreinfo_old(unsigned long * size)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(¬e, 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") != 0)
405 return NULL;
406 vmcoreinfo = kzalloc_panic(note.n_descsz);
407 if (copy_oldmem_kernel(vmcoreinfo, addr + 24, note.n_descsz))
408 return NULL;
409 *size = note.n_descsz;
410 return vmcoreinfo;
411 }
412
413 /*
414 * Initialize vmcoreinfo note (new kernel)
415 */
nt_vmcoreinfo(void * ptr)416 static void *nt_vmcoreinfo(void *ptr)
417 {
418 unsigned long size;
419 void *vmcoreinfo;
420
421 vmcoreinfo = os_info_old_entry(OS_INFO_VMCOREINFO, &size);
422 if (!vmcoreinfo)
423 vmcoreinfo = get_vmcoreinfo_old(&size);
424 if (!vmcoreinfo)
425 return ptr;
426 return nt_init_name(ptr, 0, vmcoreinfo, size, "VMCOREINFO");
427 }
428
429 /*
430 * Initialize final note (needed for /proc/vmcore code)
431 */
nt_final(void * ptr)432 static void *nt_final(void *ptr)
433 {
434 Elf64_Nhdr *note;
435
436 note = (Elf64_Nhdr *) ptr;
437 note->n_namesz = 0;
438 note->n_descsz = 0;
439 note->n_type = 0;
440 return PTR_ADD(ptr, sizeof(Elf64_Nhdr));
441 }
442
443 /*
444 * Initialize ELF header (new kernel)
445 */
ehdr_init(Elf64_Ehdr * ehdr,int mem_chunk_cnt)446 static void *ehdr_init(Elf64_Ehdr *ehdr, int mem_chunk_cnt)
447 {
448 memset(ehdr, 0, sizeof(*ehdr));
449 memcpy(ehdr->e_ident, ELFMAG, SELFMAG);
450 ehdr->e_ident[EI_CLASS] = ELFCLASS64;
451 ehdr->e_ident[EI_DATA] = ELFDATA2MSB;
452 ehdr->e_ident[EI_VERSION] = EV_CURRENT;
453 memset(ehdr->e_ident + EI_PAD, 0, EI_NIDENT - EI_PAD);
454 ehdr->e_type = ET_CORE;
455 ehdr->e_machine = EM_S390;
456 ehdr->e_version = EV_CURRENT;
457 ehdr->e_phoff = sizeof(Elf64_Ehdr);
458 ehdr->e_ehsize = sizeof(Elf64_Ehdr);
459 ehdr->e_phentsize = sizeof(Elf64_Phdr);
460 ehdr->e_phnum = mem_chunk_cnt + 1;
461 return ehdr + 1;
462 }
463
464 /*
465 * Return CPU count for ELF header (new kernel)
466 */
get_cpu_cnt(void)467 static int get_cpu_cnt(void)
468 {
469 struct save_area *sa;
470 int cpus = 0;
471
472 list_for_each_entry(sa, &dump_save_areas, list)
473 if (sa->prefix != 0)
474 cpus++;
475 return cpus;
476 }
477
478 /*
479 * Return memory chunk count for ELF header (new kernel)
480 */
get_mem_chunk_cnt(void)481 static int get_mem_chunk_cnt(void)
482 {
483 int cnt = 0;
484 u64 idx;
485
486 for_each_mem_range(idx, &memblock.physmem, &oldmem_type, NUMA_NO_NODE,
487 MEMBLOCK_NONE, NULL, NULL, NULL)
488 cnt++;
489 return cnt;
490 }
491
492 /*
493 * Initialize ELF loads (new kernel)
494 */
loads_init(Elf64_Phdr * phdr,u64 loads_offset)495 static void loads_init(Elf64_Phdr *phdr, u64 loads_offset)
496 {
497 phys_addr_t start, end;
498 u64 idx;
499
500 for_each_mem_range(idx, &memblock.physmem, &oldmem_type, NUMA_NO_NODE,
501 MEMBLOCK_NONE, &start, &end, NULL) {
502 phdr->p_filesz = end - start;
503 phdr->p_type = PT_LOAD;
504 phdr->p_offset = start;
505 phdr->p_vaddr = start;
506 phdr->p_paddr = start;
507 phdr->p_memsz = end - start;
508 phdr->p_flags = PF_R | PF_W | PF_X;
509 phdr->p_align = PAGE_SIZE;
510 phdr++;
511 }
512 }
513
514 /*
515 * Initialize notes (new kernel)
516 */
notes_init(Elf64_Phdr * phdr,void * ptr,u64 notes_offset)517 static void *notes_init(Elf64_Phdr *phdr, void *ptr, u64 notes_offset)
518 {
519 struct save_area *sa;
520 void *ptr_start = ptr;
521 int cpu;
522
523 ptr = nt_prpsinfo(ptr);
524
525 cpu = 1;
526 list_for_each_entry(sa, &dump_save_areas, list)
527 if (sa->prefix != 0)
528 ptr = fill_cpu_elf_notes(ptr, cpu++, sa);
529 ptr = nt_vmcoreinfo(ptr);
530 ptr = nt_final(ptr);
531 memset(phdr, 0, sizeof(*phdr));
532 phdr->p_type = PT_NOTE;
533 phdr->p_offset = notes_offset;
534 phdr->p_filesz = (unsigned long) PTR_SUB(ptr, ptr_start);
535 phdr->p_memsz = phdr->p_filesz;
536 return ptr;
537 }
538
539 /*
540 * Create ELF core header (new kernel)
541 */
elfcorehdr_alloc(unsigned long long * addr,unsigned long long * size)542 int elfcorehdr_alloc(unsigned long long *addr, unsigned long long *size)
543 {
544 Elf64_Phdr *phdr_notes, *phdr_loads;
545 int mem_chunk_cnt;
546 void *ptr, *hdr;
547 u32 alloc_size;
548 u64 hdr_off;
549
550 /* If we are not in kdump or zfcpdump mode return */
551 if (!OLDMEM_BASE && ipl_info.type != IPL_TYPE_FCP_DUMP)
552 return 0;
553 /* If we cannot get HSA size for zfcpdump return error */
554 if (ipl_info.type == IPL_TYPE_FCP_DUMP && !sclp.hsa_size)
555 return -ENODEV;
556
557 /* For kdump, exclude previous crashkernel memory */
558 if (OLDMEM_BASE) {
559 oldmem_region.base = OLDMEM_BASE;
560 oldmem_region.size = OLDMEM_SIZE;
561 oldmem_type.total_size = OLDMEM_SIZE;
562 }
563
564 mem_chunk_cnt = get_mem_chunk_cnt();
565
566 alloc_size = 0x1000 + get_cpu_cnt() * 0x4a0 +
567 mem_chunk_cnt * sizeof(Elf64_Phdr);
568 hdr = kzalloc_panic(alloc_size);
569 /* Init elf header */
570 ptr = ehdr_init(hdr, mem_chunk_cnt);
571 /* Init program headers */
572 phdr_notes = ptr;
573 ptr = PTR_ADD(ptr, sizeof(Elf64_Phdr));
574 phdr_loads = ptr;
575 ptr = PTR_ADD(ptr, sizeof(Elf64_Phdr) * mem_chunk_cnt);
576 /* Init notes */
577 hdr_off = PTR_DIFF(ptr, hdr);
578 ptr = notes_init(phdr_notes, ptr, ((unsigned long) hdr) + hdr_off);
579 /* Init loads */
580 hdr_off = PTR_DIFF(ptr, hdr);
581 loads_init(phdr_loads, hdr_off);
582 *addr = (unsigned long long) hdr;
583 *size = (unsigned long long) hdr_off;
584 BUG_ON(elfcorehdr_size > alloc_size);
585 return 0;
586 }
587
588 /*
589 * Free ELF core header (new kernel)
590 */
elfcorehdr_free(unsigned long long addr)591 void elfcorehdr_free(unsigned long long addr)
592 {
593 kfree((void *)(unsigned long)addr);
594 }
595
596 /*
597 * Read from ELF header
598 */
elfcorehdr_read(char * buf,size_t count,u64 * ppos)599 ssize_t elfcorehdr_read(char *buf, size_t count, u64 *ppos)
600 {
601 void *src = (void *)(unsigned long)*ppos;
602
603 memcpy(buf, src, count);
604 *ppos += count;
605 return count;
606 }
607
608 /*
609 * Read from ELF notes data
610 */
elfcorehdr_read_notes(char * buf,size_t count,u64 * ppos)611 ssize_t elfcorehdr_read_notes(char *buf, size_t count, u64 *ppos)
612 {
613 void *src = (void *)(unsigned long)*ppos;
614
615 memcpy(buf, src, count);
616 *ppos += count;
617 return count;
618 }
619