arch/x86/kernel/crash.c

   1 /*
   2  * Architecture specific (i386/x86_64) functions for kexec based crash dumps.
   3  *
   4  * Created by: Hariprasad Nellitheertha (hari@in.ibm.com)
   5  *
   6  * Copyright (C) IBM Corporation, 2004. All rights reserved.
   7  * Copyright (C) Red Hat Inc., 2014. All rights reserved.
   8  * Authors:
   9  *      Vivek Goyal <vgoyal@redhat.com>
  10  *
  11  */
  12
  13 #define pr_fmt(fmt)     "kexec: " fmt
  14
  15 #include <linux/types.h>
  16 #include <linux/kernel.h>
  17 #include <linux/smp.h>
  18 #include <linux/reboot.h>
  19 #include <linux/kexec.h>
  20 #include <linux/delay.h>
  21 #include <linux/elf.h>
  22 #include <linux/elfcore.h>
  23 #include <linux/module.h>
  24 #include <linux/slab.h>
  25
  26 #include <asm/processor.h>
  27 #include <asm/hardirq.h>
  28 #include <asm/nmi.h>
  29 #include <asm/hw_irq.h>
  30 #include <asm/apic.h>
  31 #include <asm/io_apic.h>
  32 #include <asm/hpet.h>
  33 #include <linux/kdebug.h>
  34 #include <asm/cpu.h>
  35 #include <asm/reboot.h>
  36 #include <asm/virtext.h>
  37
  38 /* Alignment required for elf header segment */
  39 #define ELF_CORE_HEADER_ALIGN   4096
  40
  41 /* This primarily represents number of split ranges due to exclusion */
  42 #define CRASH_MAX_RANGES        16
  43
  44 struct crash_mem_range {
  45         u64 start, end;
  46 };
  47
  48 struct crash_mem {
  49         unsigned int nr_ranges;
  50         struct crash_mem_range ranges[CRASH_MAX_RANGES];
  51 };
  52
  53 /* Misc data about ram ranges needed to prepare elf headers */
  54 struct crash_elf_data {
  55         struct kimage *image;
  56         /*
  57          * Total number of ram ranges we have after various adjustments for
  58          * GART, crash reserved region etc.
  59          */
  60         unsigned int max_nr_ranges;
  61         unsigned long gart_start, gart_end;
  62
  63         /* Pointer to elf header */
  64         void *ehdr;
  65         /* Pointer to next phdr */
  66         void *bufp;
  67         struct crash_mem mem;
  68 };
  69
  70 /* Used while preparing memory map entries for second kernel */
  71 struct crash_memmap_data {
  72         struct boot_params *params;
  73         /* Type of memory */
  74         unsigned int type;
  75 };
  76
  77 int in_crash_kexec;
  78
  79 /*
  80  * This is used to VMCLEAR all VMCSs loaded on the
  81  * processor. And when loading kvm_intel module, the
  82  * callback function pointer will be assigned.
  83  *
  84  * protected by rcu.
  85  */
  86 crash_vmclear_fn __rcu *crash_vmclear_loaded_vmcss = NULL;
  87 EXPORT_SYMBOL_GPL(crash_vmclear_loaded_vmcss);
  88 unsigned long crash_zero_bytes;
  89
  90 static inline void cpu_crash_vmclear_loaded_vmcss(void)
  91 {
  92         crash_vmclear_fn *do_vmclear_operation = NULL;
  93
  94         rcu_read_lock();
  95         do_vmclear_operation = rcu_dereference(crash_vmclear_loaded_vmcss);
  96         if (do_vmclear_operation)
  97                 do_vmclear_operation();
  98         rcu_read_unlock();
  99 }
 100
 101 #if defined(CONFIG_SMP) && defined(CONFIG_X86_LOCAL_APIC)
 102
 103 static void kdump_nmi_callback(int cpu, struct pt_regs *regs)
 104 {
 105 #ifdef CONFIG_X86_32
 106         struct pt_regs fixed_regs;
 107
 108         if (!user_mode(regs)) {
 109                 crash_fixup_ss_esp(&fixed_regs, regs);
 110                 regs = &fixed_regs;
 111         }
 112 #endif
 113         crash_save_cpu(regs, cpu);
 114
 115         /*
 116          * VMCLEAR VMCSs loaded on all cpus if needed.
 117          */
 118         cpu_crash_vmclear_loaded_vmcss();
 119
 120         /* Disable VMX or SVM if needed.
 121          *
 122          * We need to disable virtualization on all CPUs.
 123          * Having VMX or SVM enabled on any CPU may break rebooting
 124          * after the kdump kernel has finished its task.
 125          */
 126         cpu_emergency_vmxoff();
 127         cpu_emergency_svm_disable();
 128
 129         disable_local_APIC();
 130 }
 131
 132 static void kdump_nmi_shootdown_cpus(void)
 133 {
 134         in_crash_kexec = 1;
 135         nmi_shootdown_cpus(kdump_nmi_callback);
 136
 137         disable_local_APIC();
 138 }
 139
 140 #else
 141 static void kdump_nmi_shootdown_cpus(void)
 142 {
 143         /* There are no cpus to shootdown */
 144 }
 145 #endif
 146
 147 void native_machine_crash_shutdown(struct pt_regs *regs)
 148 {
 149         /* This function is only called after the system
 150          * has panicked or is otherwise in a critical state.
 151          * The minimum amount of code to allow a kexec'd kernel
 152          * to run successfully needs to happen here.
 153          *
 154          * In practice this means shooting down the other cpus in
 155          * an SMP system.
 156          */
 157         /* The kernel is broken so disable interrupts */
 158         local_irq_disable();
 159
 160         kdump_nmi_shootdown_cpus();
 161
 162         /*
 163          * VMCLEAR VMCSs loaded on this cpu if needed.
 164          */
 165         cpu_crash_vmclear_loaded_vmcss();
 166
 167         /* Booting kdump kernel with VMX or SVM enabled won't work,
 168          * because (among other limitations) we can't disable paging
 169          * with the virt flags.
 170          */
 171         cpu_emergency_vmxoff();
 172         cpu_emergency_svm_disable();
 173
 174 #ifdef CONFIG_X86_IO_APIC
 175         /* Prevent crash_kexec() from deadlocking on ioapic_lock. */
 176         ioapic_zap_locks();
 177         disable_IO_APIC();
 178 #endif
 179         lapic_shutdown();
 180 #ifdef CONFIG_HPET_TIMER
 181         hpet_disable();
 182 #endif
 183         crash_save_cpu(regs, safe_smp_processor_id());
 184 }
 185
 186 #ifdef CONFIG_KEXEC_FILE
 187 static int get_nr_ram_ranges_callback(unsigned long start_pfn,
 188                                 unsigned long nr_pfn, void *arg)
 189 {
 190         int *nr_ranges = arg;
 191
 192         (*nr_ranges)++;
 193         return 0;
 194 }
 195
 196 static int get_gart_ranges_callback(u64 start, u64 end, void *arg)
 197 {
 198         struct crash_elf_data *ced = arg;
 199
 200         ced->gart_start = start;
 201         ced->gart_end = end;
 202
 203         /* Not expecting more than 1 gart aperture */
 204         return 1;
 205 }
 206
 207
 208 /* Gather all the required information to prepare elf headers for ram regions */
 209 static void fill_up_crash_elf_data(struct crash_elf_data *ced,
 210                                    struct kimage *image)
 211 {
 212         unsigned int nr_ranges = 0;
 213
 214         ced->image = image;
 215
 216         walk_system_ram_range(0, -1, &nr_ranges,
 217                                 get_nr_ram_ranges_callback);
 218
 219         ced->max_nr_ranges = nr_ranges;
 220
 221         /*
 222          * We don't create ELF headers for GART aperture as an attempt
 223          * to dump this memory in second kernel leads to hang/crash.
 224          * If gart aperture is present, one needs to exclude that region
 225          * and that could lead to need of extra phdr.
 226          */
 227         walk_iomem_res("GART", IORESOURCE_MEM, 0, -1,
 228                                 ced, get_gart_ranges_callback);
 229
 230         /*
 231          * If we have gart region, excluding that could potentially split
 232          * a memory range, resulting in extra header. Account for  that.
 233          */
 234         if (ced->gart_end)
 235                 ced->max_nr_ranges++;
 236
 237         /* Exclusion of crash region could split memory ranges */
 238         ced->max_nr_ranges++;
 239
 240         /* If crashk_low_res is not 0, another range split possible */
 241         if (crashk_low_res.end)
 242                 ced->max_nr_ranges++;
 243 }
 244
 245 static int exclude_mem_range(struct crash_mem *mem,
 246                 unsigned long long mstart, unsigned long long mend)
 247 {
 248         int i, j;
 249         unsigned long long start, end;
 250         struct crash_mem_range temp_range = {0, 0};
 251
 252         for (i = 0; i < mem->nr_ranges; i++) {
 253                 start = mem->ranges[i].start;
 254                 end = mem->ranges[i].end;
 255
 256                 if (mstart > end || mend < start)
 257                         continue;
 258
 259                 /* Truncate any area outside of range */
 260                 if (mstart < start)
 261                         mstart = start;
 262                 if (mend > end)
 263                         mend = end;
 264
 265                 /* Found completely overlapping range */
 266                 if (mstart == start && mend == end) {
 267                         mem->ranges[i].start = 0;
 268                         mem->ranges[i].end = 0;
 269                         if (i < mem->nr_ranges - 1) {
 270                                 /* Shift rest of the ranges to left */
 271                                 for (j = i; j < mem->nr_ranges - 1; j++) {
 272                                         mem->ranges[j].start =
 273                                                 mem->ranges[j+1].start;
 274                                         mem->ranges[j].end =
 275                                                         mem->ranges[j+1].end;
 276                                 }
 277                         }
 278                         mem->nr_ranges--;
 279                         return 0;
 280                 }
 281
 282                 if (mstart > start && mend < end) {
 283                         /* Split original range */
 284                         mem->ranges[i].end = mstart - 1;
 285                         temp_range.start = mend + 1;
 286                         temp_range.end = end;
 287                 } else if (mstart != start)
 288                         mem->ranges[i].end = mstart - 1;
 289                 else
 290                         mem->ranges[i].start = mend + 1;
 291                 break;
 292         }
 293
 294         /* If a split happend, add the split to array */
 295         if (!temp_range.end)
 296                 return 0;
 297
 298         /* Split happened */
 299         if (i == CRASH_MAX_RANGES - 1) {
 300                 pr_err("Too many crash ranges after split\n");
 301                 return -ENOMEM;
 302         }
 303
 304         /* Location where new range should go */
 305         j = i + 1;
 306         if (j < mem->nr_ranges) {
 307                 /* Move over all ranges one slot towards the end */
 308                 for (i = mem->nr_ranges - 1; i >= j; i--)
 309                         mem->ranges[i + 1] = mem->ranges[i];
 310         }
 311
 312         mem->ranges[j].start = temp_range.start;
 313         mem->ranges[j].end = temp_range.end;
 314         mem->nr_ranges++;
 315         return 0;
 316 }
 317
 318 /*
 319  * Look for any unwanted ranges between mstart, mend and remove them. This
 320  * might lead to split and split ranges are put in ced->mem.ranges[] array
 321  */
 322 static int elf_header_exclude_ranges(struct crash_elf_data *ced,
 323                 unsigned long long mstart, unsigned long long mend)
 324 {
 325         struct crash_mem *cmem = &ced->mem;
 326         int ret = 0;
 327
 328         memset(cmem->ranges, 0, sizeof(cmem->ranges));
 329
 330         cmem->ranges[0].start = mstart;
 331         cmem->ranges[0].end = mend;
 332         cmem->nr_ranges = 1;
 333
 334         /* Exclude crashkernel region */
 335         ret = exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
 336         if (ret)
 337                 return ret;
 338
 339         if (crashk_low_res.end) {
 340                 ret = exclude_mem_range(cmem, crashk_low_res.start, crashk_low_res.end);
 341                 if (ret)
 342                         return ret;
 343         }
 344
 345         /* Exclude GART region */
 346         if (ced->gart_end) {
 347                 ret = exclude_mem_range(cmem, ced->gart_start, ced->gart_end);
 348                 if (ret)
 349                         return ret;
 350         }
 351
 352         return ret;
 353 }
 354
 355 static int prepare_elf64_ram_headers_callback(u64 start, u64 end, void *arg)
 356 {
 357         struct crash_elf_data *ced = arg;
 358         Elf64_Ehdr *ehdr;
 359         Elf64_Phdr *phdr;
 360         unsigned long mstart, mend;
 361         struct kimage *image = ced->image;
 362         struct crash_mem *cmem;
 363         int ret, i;
 364
 365         ehdr = ced->ehdr;
 366
 367         /* Exclude unwanted mem ranges */
 368         ret = elf_header_exclude_ranges(ced, start, end);
 369         if (ret)
 370                 return ret;
 371
 372         /* Go through all the ranges in ced->mem.ranges[] and prepare phdr */
 373         cmem = &ced->mem;
 374
 375         for (i = 0; i < cmem->nr_ranges; i++) {
 376                 mstart = cmem->ranges[i].start;
 377                 mend = cmem->ranges[i].end;
 378
 379                 phdr = ced->bufp;
 380                 ced->bufp += sizeof(Elf64_Phdr);
 381
 382                 phdr->p_type = PT_LOAD;
 383                 phdr->p_flags = PF_R|PF_W|PF_X;
 384                 phdr->p_offset  = mstart;
 385
 386                 /*
 387                  * If a range matches backup region, adjust offset to backup
 388                  * segment.
 389                  */
 390                 if (mstart == image->arch.backup_src_start &&
 391                     (mend - mstart + 1) == image->arch.backup_src_sz)
 392                         phdr->p_offset = image->arch.backup_load_addr;
 393
 394                 phdr->p_paddr = mstart;
 395                 phdr->p_vaddr = (unsigned long long) __va(mstart);
 396                 phdr->p_filesz = phdr->p_memsz = mend - mstart + 1;
 397                 phdr->p_align = 0;
 398                 ehdr->e_phnum++;
 399                 pr_debug("Crash PT_LOAD elf header. phdr=%p vaddr=0x%llx, paddr=0x%llx, sz=0x%llx e_phnum=%d p_offset=0x%llx\n",
 400                         phdr, phdr->p_vaddr, phdr->p_paddr, phdr->p_filesz,
 401                         ehdr->e_phnum, phdr->p_offset);
 402         }
 403
 404         return ret;
 405 }
 406
 407 static int prepare_elf64_headers(struct crash_elf_data *ced,
 408                 void **addr, unsigned long *sz)
 409 {
 410         Elf64_Ehdr *ehdr;
 411         Elf64_Phdr *phdr;
 412         unsigned long nr_cpus = num_possible_cpus(), nr_phdr, elf_sz;
 413         unsigned char *buf, *bufp;
 414         unsigned int cpu;
 415         unsigned long long notes_addr;
 416         int ret;
 417
 418         /* extra phdr for vmcoreinfo elf note */
 419         nr_phdr = nr_cpus + 1;
 420         nr_phdr += ced->max_nr_ranges;
 421
 422         /*
 423          * kexec-tools creates an extra PT_LOAD phdr for kernel text mapping
 424          * area on x86_64 (ffffffff80000000 - ffffffffa0000000).
 425          * I think this is required by tools like gdb. So same physical
 426          * memory will be mapped in two elf headers. One will contain kernel
 427          * text virtual addresses and other will have __va(physical) addresses.
 428          */
 429
 430         nr_phdr++;
 431         elf_sz = sizeof(Elf64_Ehdr) + nr_phdr * sizeof(Elf64_Phdr);
 432         elf_sz = ALIGN(elf_sz, ELF_CORE_HEADER_ALIGN);
 433
 434         buf = vzalloc(elf_sz);
 435         if (!buf)
 436                 return -ENOMEM;
 437
 438         bufp = buf;
 439         ehdr = (Elf64_Ehdr *)bufp;
 440         bufp += sizeof(Elf64_Ehdr);
 441         memcpy(ehdr->e_ident, ELFMAG, SELFMAG);
 442         ehdr->e_ident[EI_CLASS] = ELFCLASS64;
 443         ehdr->e_ident[EI_DATA] = ELFDATA2LSB;
 444         ehdr->e_ident[EI_VERSION] = EV_CURRENT;
 445         ehdr->e_ident[EI_OSABI] = ELF_OSABI;
 446         memset(ehdr->e_ident + EI_PAD, 0, EI_NIDENT - EI_PAD);
 447         ehdr->e_type = ET_CORE;
 448         ehdr->e_machine = ELF_ARCH;
 449         ehdr->e_version = EV_CURRENT;
 450         ehdr->e_phoff = sizeof(Elf64_Ehdr);
 451         ehdr->e_ehsize = sizeof(Elf64_Ehdr);
 452         ehdr->e_phentsize = sizeof(Elf64_Phdr);
 453
 454         /* Prepare one phdr of type PT_NOTE for each present cpu */
 455         for_each_present_cpu(cpu) {
 456                 phdr = (Elf64_Phdr *)bufp;
 457                 bufp += sizeof(Elf64_Phdr);
 458                 phdr->p_type = PT_NOTE;
 459                 notes_addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpu));
 460                 phdr->p_offset = phdr->p_paddr = notes_addr;
 461                 phdr->p_filesz = phdr->p_memsz = sizeof(note_buf_t);
 462                 (ehdr->e_phnum)++;
 463         }
 464
 465         /* Prepare one PT_NOTE header for vmcoreinfo */
 466         phdr = (Elf64_Phdr *)bufp;
 467         bufp += sizeof(Elf64_Phdr);
 468         phdr->p_type = PT_NOTE;
 469         phdr->p_offset = phdr->p_paddr = paddr_vmcoreinfo_note();
 470         phdr->p_filesz = phdr->p_memsz = sizeof(vmcoreinfo_note);
 471         (ehdr->e_phnum)++;
 472
 473 #ifdef CONFIG_X86_64
 474         /* Prepare PT_LOAD type program header for kernel text region */
 475         phdr = (Elf64_Phdr *)bufp;
 476         bufp += sizeof(Elf64_Phdr);
 477         phdr->p_type = PT_LOAD;
 478         phdr->p_flags = PF_R|PF_W|PF_X;
 479         phdr->p_vaddr = (Elf64_Addr)_text;
 480         phdr->p_filesz = phdr->p_memsz = _end - _text;
 481         phdr->p_offset = phdr->p_paddr = __pa_symbol(_text);
 482         (ehdr->e_phnum)++;
 483 #endif
 484
 485         /* Prepare PT_LOAD headers for system ram chunks. */
 486         ced->ehdr = ehdr;
 487         ced->bufp = bufp;
 488         ret = walk_system_ram_res(0, -1, ced,
 489                         prepare_elf64_ram_headers_callback);
 490         if (ret < 0)
 491                 return ret;
 492
 493         *addr = buf;
 494         *sz = elf_sz;
 495         return 0;
 496 }
 497
 498 /* Prepare elf headers. Return addr and size */
 499 static int prepare_elf_headers(struct kimage *image, void **addr,
 500                                         unsigned long *sz)
 501 {
 502         struct crash_elf_data *ced;
 503         int ret;
 504
 505         ced = kzalloc(sizeof(*ced), GFP_KERNEL);
 506         if (!ced)
 507                 return -ENOMEM;
 508
 509         fill_up_crash_elf_data(ced, image);
 510
 511         /* By default prepare 64bit headers */
 512         ret =  prepare_elf64_headers(ced, addr, sz);
 513         kfree(ced);
 514         return ret;
 515 }
 516
 517 static int add_e820_entry(struct boot_params *params, struct e820entry *entry)
 518 {
 519         unsigned int nr_e820_entries;
 520
 521         nr_e820_entries = params->e820_entries;
 522         if (nr_e820_entries >= E820MAX)
 523                 return 1;
 524
 525         memcpy(&params->e820_map[nr_e820_entries], entry,
 526                         sizeof(struct e820entry));
 527         params->e820_entries++;
 528         return 0;
 529 }
 530
 531 static int memmap_entry_callback(u64 start, u64 end, void *arg)
 532 {
 533         struct crash_memmap_data *cmd = arg;
 534         struct boot_params *params = cmd->params;
 535         struct e820entry ei;
 536
 537         ei.addr = start;
 538         ei.size = end - start + 1;
 539         ei.type = cmd->type;
 540         add_e820_entry(params, &ei);
 541
 542         return 0;
 543 }
 544
 545 static int memmap_exclude_ranges(struct kimage *image, struct crash_mem *cmem,
 546                                  unsigned long long mstart,
 547                                  unsigned long long mend)
 548 {
 549         unsigned long start, end;
 550         int ret = 0;
 551
 552         cmem->ranges[0].start = mstart;
 553         cmem->ranges[0].end = mend;
 554         cmem->nr_ranges = 1;
 555
 556         /* Exclude Backup region */
 557         start = image->arch.backup_load_addr;
 558         end = start + image->arch.backup_src_sz - 1;
 559         ret = exclude_mem_range(cmem, start, end);
 560         if (ret)
 561                 return ret;
 562
 563         /* Exclude elf header region */
 564         start = image->arch.elf_load_addr;
 565         end = start + image->arch.elf_headers_sz - 1;
 566         return exclude_mem_range(cmem, start, end);
 567 }
 568
 569 /* Prepare memory map for crash dump kernel */
 570 int crash_setup_memmap_entries(struct kimage *image, struct boot_params *params)
 571 {
 572         int i, ret = 0;
 573         unsigned long flags;
 574         struct e820entry ei;
 575         struct crash_memmap_data cmd;
 576         struct crash_mem *cmem;
 577
 578         cmem = vzalloc(sizeof(struct crash_mem));
 579         if (!cmem)
 580                 return -ENOMEM;
 581
 582         memset(&cmd, 0, sizeof(struct crash_memmap_data));
 583         cmd.params = params;
 584
 585         /* Add first 640K segment */
 586         ei.addr = image->arch.backup_src_start;
 587         ei.size = image->arch.backup_src_sz;
 588         ei.type = E820_RAM;
 589         add_e820_entry(params, &ei);
 590
 591         /* Add ACPI tables */
 592         cmd.type = E820_ACPI;
 593         flags = IORESOURCE_MEM | IORESOURCE_BUSY;
 594         walk_iomem_res("ACPI Tables", flags, 0, -1, &cmd,
 595                        memmap_entry_callback);
 596
 597         /* Add ACPI Non-volatile Storage */
 598         cmd.type = E820_NVS;
 599         walk_iomem_res("ACPI Non-volatile Storage", flags, 0, -1, &cmd,
 600                         memmap_entry_callback);
 601
 602         /* Add crashk_low_res region */
 603         if (crashk_low_res.end) {
 604                 ei.addr = crashk_low_res.start;
 605                 ei.size = crashk_low_res.end - crashk_low_res.start + 1;
 606                 ei.type = E820_RAM;
 607                 add_e820_entry(params, &ei);
 608         }
 609
 610         /* Exclude some ranges from crashk_res and add rest to memmap */
 611         ret = memmap_exclude_ranges(image, cmem, crashk_res.start,
 612                                                 crashk_res.end);
 613         if (ret)
 614                 goto out;
 615
 616         for (i = 0; i < cmem->nr_ranges; i++) {
 617                 ei.size = cmem->ranges[i].end - cmem->ranges[i].start + 1;
 618
 619                 /* If entry is less than a page, skip it */
 620                 if (ei.size < PAGE_SIZE)
 621                         continue;
 622                 ei.addr = cmem->ranges[i].start;
 623                 ei.type = E820_RAM;
 624                 add_e820_entry(params, &ei);
 625         }
 626
 627 out:
 628         vfree(cmem);
 629         return ret;
 630 }
 631
 632 static int determine_backup_region(u64 start, u64 end, void *arg)
 633 {
 634         struct kimage *image = arg;
 635
 636         image->arch.backup_src_start = start;
 637         image->arch.backup_src_sz = end - start + 1;
 638
 639         /* Expecting only one range for backup region */
 640         return 1;
 641 }
 642
 643 int crash_load_segments(struct kimage *image)
 644 {
 645         unsigned long src_start, src_sz, elf_sz;
 646         void *elf_addr;
 647         int ret;
 648
 649         /*
 650          * Determine and load a segment for backup area. First 640K RAM
 651          * region is backup source
 652          */
 653
 654         ret = walk_system_ram_res(KEXEC_BACKUP_SRC_START, KEXEC_BACKUP_SRC_END,
 655                                 image, determine_backup_region);
 656
 657         /* Zero or postive return values are ok */
 658         if (ret < 0)
 659                 return ret;
 660
 661         src_start = image->arch.backup_src_start;
 662         src_sz = image->arch.backup_src_sz;
 663
 664         /* Add backup segment. */
 665         if (src_sz) {
 666                 /*
 667                  * Ideally there is no source for backup segment. This is
 668                  * copied in purgatory after crash. Just add a zero filled
 669                  * segment for now to make sure checksum logic works fine.
 670                  */
 671                 ret = kexec_add_buffer(image, (char *)&crash_zero_bytes,
 672                                        sizeof(crash_zero_bytes), src_sz,
 673                                        PAGE_SIZE, 0, -1, 0,
 674                                        &image->arch.backup_load_addr);
 675                 if (ret)
 676                         return ret;
 677                 pr_debug("Loaded backup region at 0x%lx backup_start=0x%lx memsz=0x%lx\n",
 678                          image->arch.backup_load_addr, src_start, src_sz);
 679         }
 680
 681         /* Prepare elf headers and add a segment */
 682         ret = prepare_elf_headers(image, &elf_addr, &elf_sz);
 683         if (ret)
 684                 return ret;
 685
 686         image->arch.elf_headers = elf_addr;
 687         image->arch.elf_headers_sz = elf_sz;
 688
 689         ret = kexec_add_buffer(image, (char *)elf_addr, elf_sz, elf_sz,
 690                         ELF_CORE_HEADER_ALIGN, 0, -1, 0,
 691                         &image->arch.elf_load_addr);
 692         if (ret) {
 693                 vfree((void *)image->arch.elf_headers);
 694                 return ret;
 695         }
 696         pr_debug("Loaded ELF headers at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
 697                  image->arch.elf_load_addr, elf_sz, elf_sz);
 698
 699         return ret;
 700 }
 701 #endif /* CONFIG_KEXEC_FILE */