root/arch/arm64/mm/init.c

DEFINITIONS

1. reserve_crashkernel
2. reserve_crashkernel
3. early_init_dt_scan_elfcorehdr
4. reserve_elfcorehdr
5. reserve_elfcorehdr
6. max_zone_dma_phys
7. zone_sizes_init
8. zone_sizes_init
9. pfn_valid
10. early_mem
11. early_init_dt_scan_usablemem
12. fdt_enforce_memory_region
13. arm64_memblock_init
14. bootmem_init
15. free_memmap
16. free_unused_memmap
17. mem_init
18. free_initmem
19. free_initrd_mem
20. dump_mem_limit
21. register_mem_limit_dumper

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Based on arch/arm/mm/init.c
   4  *
   5  * Copyright (C) 1995-2005 Russell King
   6  * Copyright (C) 2012 ARM Ltd.
   7  */
   8 
   9 #include <linux/kernel.h>
  10 #include <linux/export.h>
  11 #include <linux/errno.h>
  12 #include <linux/swap.h>
  13 #include <linux/init.h>
  14 #include <linux/cache.h>
  15 #include <linux/mman.h>
  16 #include <linux/nodemask.h>
  17 #include <linux/initrd.h>
  18 #include <linux/gfp.h>
  19 #include <linux/memblock.h>
  20 #include <linux/sort.h>
  21 #include <linux/of.h>
  22 #include <linux/of_fdt.h>
  23 #include <linux/dma-mapping.h>
  24 #include <linux/dma-contiguous.h>
  25 #include <linux/efi.h>
  26 #include <linux/swiotlb.h>
  27 #include <linux/vmalloc.h>
  28 #include <linux/mm.h>
  29 #include <linux/kexec.h>
  30 #include <linux/crash_dump.h>
  31 
  32 #include <asm/boot.h>
  33 #include <asm/fixmap.h>
  34 #include <asm/kasan.h>
  35 #include <asm/kernel-pgtable.h>
  36 #include <asm/memory.h>
  37 #include <asm/numa.h>
  38 #include <asm/sections.h>
  39 #include <asm/setup.h>
  40 #include <linux/sizes.h>
  41 #include <asm/tlb.h>
  42 #include <asm/alternative.h>
  43 
  44 /*
  45  * We need to be able to catch inadvertent references to memstart_addr
  46  * that occur (potentially in generic code) before arm64_memblock_init()
  47  * executes, which assigns it its actual value. So use a default value
  48  * that cannot be mistaken for a real physical address.
  49  */
  50 s64 memstart_addr __ro_after_init = -1;
  51 EXPORT_SYMBOL(memstart_addr);
  52 
  53 s64 physvirt_offset __ro_after_init;
  54 EXPORT_SYMBOL(physvirt_offset);
  55 
  56 struct page *vmemmap __ro_after_init;
  57 EXPORT_SYMBOL(vmemmap);
  58 
  59 phys_addr_t arm64_dma_phys_limit __ro_after_init;
  60 
  61 #ifdef CONFIG_KEXEC_CORE
  62 /*
  63  * reserve_crashkernel() - reserves memory for crash kernel
  64  *
  65  * This function reserves memory area given in "crashkernel=" kernel command
  66  * line parameter. The memory reserved is used by dump capture kernel when
  67  * primary kernel is crashing.
  68  */
  69 static void __init reserve_crashkernel(void)
  70 {
  71         unsigned long long crash_base, crash_size;
  72         int ret;
  73 
  74         ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
  75                                 &crash_size, &crash_base);
  76         /* no crashkernel= or invalid value specified */
  77         if (ret || !crash_size)
  78                 return;
  79 
  80         crash_size = PAGE_ALIGN(crash_size);
  81 
  82         if (crash_base == 0) {
  83                 /* Current arm64 boot protocol requires 2MB alignment */
  84                 crash_base = memblock_find_in_range(0, ARCH_LOW_ADDRESS_LIMIT,
  85                                 crash_size, SZ_2M);
  86                 if (crash_base == 0) {
  87                         pr_warn("cannot allocate crashkernel (size:0x%llx)\n",
  88                                 crash_size);
  89                         return;
  90                 }
  91         } else {
  92                 /* User specifies base address explicitly. */
  93                 if (!memblock_is_region_memory(crash_base, crash_size)) {
  94                         pr_warn("cannot reserve crashkernel: region is not memory\n");
  95                         return;
  96                 }
  97 
  98                 if (memblock_is_region_reserved(crash_base, crash_size)) {
  99                         pr_warn("cannot reserve crashkernel: region overlaps reserved memory\n");
 100                         return;
 101                 }
 102 
 103                 if (!IS_ALIGNED(crash_base, SZ_2M)) {
 104                         pr_warn("cannot reserve crashkernel: base address is not 2MB aligned\n");
 105                         return;
 106                 }
 107         }
 108         memblock_reserve(crash_base, crash_size);
 109 
 110         pr_info("crashkernel reserved: 0x%016llx - 0x%016llx (%lld MB)\n",
 111                 crash_base, crash_base + crash_size, crash_size >> 20);
 112 
 113         crashk_res.start = crash_base;
 114         crashk_res.end = crash_base + crash_size - 1;
 115 }
 116 #else
 117 static void __init reserve_crashkernel(void)
 118 {
 119 }
 120 #endif /* CONFIG_KEXEC_CORE */
 121 
 122 #ifdef CONFIG_CRASH_DUMP
 123 static int __init early_init_dt_scan_elfcorehdr(unsigned long node,
 124                 const char *uname, int depth, void *data)
 125 {
 126         const __be32 *reg;
 127         int len;
 128 
 129         if (depth != 1 || strcmp(uname, "chosen") != 0)
 130                 return 0;
 131 
 132         reg = of_get_flat_dt_prop(node, "linux,elfcorehdr", &len);
 133         if (!reg || (len < (dt_root_addr_cells + dt_root_size_cells)))
 134                 return 1;
 135 
 136         elfcorehdr_addr = dt_mem_next_cell(dt_root_addr_cells, &reg);
 137         elfcorehdr_size = dt_mem_next_cell(dt_root_size_cells, &reg);
 138 
 139         return 1;
 140 }
 141 
 142 /*
 143  * reserve_elfcorehdr() - reserves memory for elf core header
 144  *
 145  * This function reserves the memory occupied by an elf core header
 146  * described in the device tree. This region contains all the
 147  * information about primary kernel's core image and is used by a dump
 148  * capture kernel to access the system memory on primary kernel.
 149  */
 150 static void __init reserve_elfcorehdr(void)
 151 {
 152         of_scan_flat_dt(early_init_dt_scan_elfcorehdr, NULL);
 153 
 154         if (!elfcorehdr_size)
 155                 return;
 156 
 157         if (memblock_is_region_reserved(elfcorehdr_addr, elfcorehdr_size)) {
 158                 pr_warn("elfcorehdr is overlapped\n");
 159                 return;
 160         }
 161 
 162         memblock_reserve(elfcorehdr_addr, elfcorehdr_size);
 163 
 164         pr_info("Reserving %lldKB of memory at 0x%llx for elfcorehdr\n",
 165                 elfcorehdr_size >> 10, elfcorehdr_addr);
 166 }
 167 #else
 168 static void __init reserve_elfcorehdr(void)
 169 {
 170 }
 171 #endif /* CONFIG_CRASH_DUMP */
 172 /*
 173  * Return the maximum physical address for ZONE_DMA32 (DMA_BIT_MASK(32)). It
 174  * currently assumes that for memory starting above 4G, 32-bit devices will
 175  * use a DMA offset.
 176  */
 177 static phys_addr_t __init max_zone_dma_phys(void)
 178 {
 179         phys_addr_t offset = memblock_start_of_DRAM() & GENMASK_ULL(63, 32);
 180         return min(offset + (1ULL << 32), memblock_end_of_DRAM());
 181 }
 182 
 183 #ifdef CONFIG_NUMA
 184 
 185 static void __init zone_sizes_init(unsigned long min, unsigned long max)
 186 {
 187         unsigned long max_zone_pfns[MAX_NR_ZONES]  = {0};
 188 
 189 #ifdef CONFIG_ZONE_DMA32
 190         max_zone_pfns[ZONE_DMA32] = PFN_DOWN(max_zone_dma_phys());
 191 #endif
 192         max_zone_pfns[ZONE_NORMAL] = max;
 193 
 194         free_area_init_nodes(max_zone_pfns);
 195 }
 196 
 197 #else
 198 
 199 static void __init zone_sizes_init(unsigned long min, unsigned long max)
 200 {
 201         struct memblock_region *reg;
 202         unsigned long zone_size[MAX_NR_ZONES], zhole_size[MAX_NR_ZONES];
 203         unsigned long max_dma = min;
 204 
 205         memset(zone_size, 0, sizeof(zone_size));
 206 
 207         /* 4GB maximum for 32-bit only capable devices */
 208 #ifdef CONFIG_ZONE_DMA32
 209         max_dma = PFN_DOWN(arm64_dma_phys_limit);
 210         zone_size[ZONE_DMA32] = max_dma - min;
 211 #endif
 212         zone_size[ZONE_NORMAL] = max - max_dma;
 213 
 214         memcpy(zhole_size, zone_size, sizeof(zhole_size));
 215 
 216         for_each_memblock(memory, reg) {
 217                 unsigned long start = memblock_region_memory_base_pfn(reg);
 218                 unsigned long end = memblock_region_memory_end_pfn(reg);
 219 
 220                 if (start >= max)
 221                         continue;
 222 
 223 #ifdef CONFIG_ZONE_DMA32
 224                 if (start < max_dma) {
 225                         unsigned long dma_end = min(end, max_dma);
 226                         zhole_size[ZONE_DMA32] -= dma_end - start;
 227                 }
 228 #endif
 229                 if (end > max_dma) {
 230                         unsigned long normal_end = min(end, max);
 231                         unsigned long normal_start = max(start, max_dma);
 232                         zhole_size[ZONE_NORMAL] -= normal_end - normal_start;
 233                 }
 234         }
 235 
 236         free_area_init_node(0, zone_size, min, zhole_size);
 237 }
 238 
 239 #endif /* CONFIG_NUMA */
 240 
 241 int pfn_valid(unsigned long pfn)
 242 {
 243         phys_addr_t addr = pfn << PAGE_SHIFT;
 244 
 245         if ((addr >> PAGE_SHIFT) != pfn)
 246                 return 0;
 247 
 248 #ifdef CONFIG_SPARSEMEM
 249         if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
 250                 return 0;
 251 
 252         if (!valid_section(__nr_to_section(pfn_to_section_nr(pfn))))
 253                 return 0;
 254 #endif
 255         return memblock_is_map_memory(addr);
 256 }
 257 EXPORT_SYMBOL(pfn_valid);
 258 
 259 static phys_addr_t memory_limit = PHYS_ADDR_MAX;
 260 
 261 /*
 262  * Limit the memory size that was specified via FDT.
 263  */
 264 static int __init early_mem(char *p)
 265 {
 266         if (!p)
 267                 return 1;
 268 
 269         memory_limit = memparse(p, &p) & PAGE_MASK;
 270         pr_notice("Memory limited to %lldMB\n", memory_limit >> 20);
 271 
 272         return 0;
 273 }
 274 early_param("mem", early_mem);
 275 
 276 static int __init early_init_dt_scan_usablemem(unsigned long node,
 277                 const char *uname, int depth, void *data)
 278 {
 279         struct memblock_region *usablemem = data;
 280         const __be32 *reg;
 281         int len;
 282 
 283         if (depth != 1 || strcmp(uname, "chosen") != 0)
 284                 return 0;
 285 
 286         reg = of_get_flat_dt_prop(node, "linux,usable-memory-range", &len);
 287         if (!reg || (len < (dt_root_addr_cells + dt_root_size_cells)))
 288                 return 1;
 289 
 290         usablemem->base = dt_mem_next_cell(dt_root_addr_cells, &reg);
 291         usablemem->size = dt_mem_next_cell(dt_root_size_cells, &reg);
 292 
 293         return 1;
 294 }
 295 
 296 static void __init fdt_enforce_memory_region(void)
 297 {
 298         struct memblock_region reg = {
 299                 .size = 0,
 300         };
 301 
 302         of_scan_flat_dt(early_init_dt_scan_usablemem, &reg);
 303 
 304         if (reg.size)
 305                 memblock_cap_memory_range(reg.base, reg.size);
 306 }
 307 
 308 void __init arm64_memblock_init(void)
 309 {
 310         const s64 linear_region_size = BIT(vabits_actual - 1);
 311 
 312         /* Handle linux,usable-memory-range property */
 313         fdt_enforce_memory_region();
 314 
 315         /* Remove memory above our supported physical address size */
 316         memblock_remove(1ULL << PHYS_MASK_SHIFT, ULLONG_MAX);
 317 
 318         /*
 319          * Select a suitable value for the base of physical memory.
 320          */
 321         memstart_addr = round_down(memblock_start_of_DRAM(),
 322                                    ARM64_MEMSTART_ALIGN);
 323 
 324         physvirt_offset = PHYS_OFFSET - PAGE_OFFSET;
 325 
 326         vmemmap = ((struct page *)VMEMMAP_START - (memstart_addr >> PAGE_SHIFT));
 327 
 328         /*
 329          * If we are running with a 52-bit kernel VA config on a system that
 330          * does not support it, we have to offset our vmemmap and physvirt_offset
 331          * s.t. we avoid the 52-bit portion of the direct linear map
 332          */
 333         if (IS_ENABLED(CONFIG_ARM64_VA_BITS_52) && (vabits_actual != 52)) {
 334                 vmemmap += (_PAGE_OFFSET(48) - _PAGE_OFFSET(52)) >> PAGE_SHIFT;
 335                 physvirt_offset = PHYS_OFFSET - _PAGE_OFFSET(48);
 336         }
 337 
 338         /*
 339          * Remove the memory that we will not be able to cover with the
 340          * linear mapping. Take care not to clip the kernel which may be
 341          * high in memory.
 342          */
 343         memblock_remove(max_t(u64, memstart_addr + linear_region_size,
 344                         __pa_symbol(_end)), ULLONG_MAX);
 345         if (memstart_addr + linear_region_size < memblock_end_of_DRAM()) {
 346                 /* ensure that memstart_addr remains sufficiently aligned */
 347                 memstart_addr = round_up(memblock_end_of_DRAM() - linear_region_size,
 348                                          ARM64_MEMSTART_ALIGN);
 349                 memblock_remove(0, memstart_addr);
 350         }
 351 
 352         /*
 353          * Apply the memory limit if it was set. Since the kernel may be loaded
 354          * high up in memory, add back the kernel region that must be accessible
 355          * via the linear mapping.
 356          */
 357         if (memory_limit != PHYS_ADDR_MAX) {
 358                 memblock_mem_limit_remove_map(memory_limit);
 359                 memblock_add(__pa_symbol(_text), (u64)(_end - _text));
 360         }
 361 
 362         if (IS_ENABLED(CONFIG_BLK_DEV_INITRD) && phys_initrd_size) {
 363                 /*
 364                  * Add back the memory we just removed if it results in the
 365                  * initrd to become inaccessible via the linear mapping.
 366                  * Otherwise, this is a no-op
 367                  */
 368                 u64 base = phys_initrd_start & PAGE_MASK;
 369                 u64 size = PAGE_ALIGN(phys_initrd_start + phys_initrd_size) - base;
 370 
 371                 /*
 372                  * We can only add back the initrd memory if we don't end up
 373                  * with more memory than we can address via the linear mapping.
 374                  * It is up to the bootloader to position the kernel and the
 375                  * initrd reasonably close to each other (i.e., within 32 GB of
 376                  * each other) so that all granule/#levels combinations can
 377                  * always access both.
 378                  */
 379                 if (WARN(base < memblock_start_of_DRAM() ||
 380                          base + size > memblock_start_of_DRAM() +
 381                                        linear_region_size,
 382                         "initrd not fully accessible via the linear mapping -- please check your bootloader ...\n")) {
 383                         phys_initrd_size = 0;
 384                 } else {
 385                         memblock_remove(base, size); /* clear MEMBLOCK_ flags */
 386                         memblock_add(base, size);
 387                         memblock_reserve(base, size);
 388                 }
 389         }
 390 
 391         if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
 392                 extern u16 memstart_offset_seed;
 393                 u64 range = linear_region_size -
 394                             (memblock_end_of_DRAM() - memblock_start_of_DRAM());
 395 
 396                 /*
 397                  * If the size of the linear region exceeds, by a sufficient
 398                  * margin, the size of the region that the available physical
 399                  * memory spans, randomize the linear region as well.
 400                  */
 401                 if (memstart_offset_seed > 0 && range >= ARM64_MEMSTART_ALIGN) {
 402                         range /= ARM64_MEMSTART_ALIGN;
 403                         memstart_addr -= ARM64_MEMSTART_ALIGN *
 404                                          ((range * memstart_offset_seed) >> 16);
 405                 }
 406         }
 407 
 408         /*
 409          * Register the kernel text, kernel data, initrd, and initial
 410          * pagetables with memblock.
 411          */
 412         memblock_reserve(__pa_symbol(_text), _end - _text);
 413         if (IS_ENABLED(CONFIG_BLK_DEV_INITRD) && phys_initrd_size) {
 414                 /* the generic initrd code expects virtual addresses */
 415                 initrd_start = __phys_to_virt(phys_initrd_start);
 416                 initrd_end = initrd_start + phys_initrd_size;
 417         }
 418 
 419         early_init_fdt_scan_reserved_mem();
 420 
 421         /* 4GB maximum for 32-bit only capable devices */
 422         if (IS_ENABLED(CONFIG_ZONE_DMA32))
 423                 arm64_dma_phys_limit = max_zone_dma_phys();
 424         else
 425                 arm64_dma_phys_limit = PHYS_MASK + 1;
 426 
 427         reserve_crashkernel();
 428 
 429         reserve_elfcorehdr();
 430 
 431         high_memory = __va(memblock_end_of_DRAM() - 1) + 1;
 432 
 433         dma_contiguous_reserve(arm64_dma_phys_limit);
 434 }
 435 
 436 void __init bootmem_init(void)
 437 {
 438         unsigned long min, max;
 439 
 440         min = PFN_UP(memblock_start_of_DRAM());
 441         max = PFN_DOWN(memblock_end_of_DRAM());
 442 
 443         early_memtest(min << PAGE_SHIFT, max << PAGE_SHIFT);
 444 
 445         max_pfn = max_low_pfn = max;
 446         min_low_pfn = min;
 447 
 448         arm64_numa_init();
 449         /*
 450          * Sparsemem tries to allocate bootmem in memory_present(), so must be
 451          * done after the fixed reservations.
 452          */
 453         memblocks_present();
 454 
 455         sparse_init();
 456         zone_sizes_init(min, max);
 457 
 458         memblock_dump_all();
 459 }
 460 
 461 #ifndef CONFIG_SPARSEMEM_VMEMMAP
 462 static inline void free_memmap(unsigned long start_pfn, unsigned long end_pfn)
 463 {
 464         struct page *start_pg, *end_pg;
 465         unsigned long pg, pgend;
 466 
 467         /*
 468          * Convert start_pfn/end_pfn to a struct page pointer.
 469          */
 470         start_pg = pfn_to_page(start_pfn - 1) + 1;
 471         end_pg = pfn_to_page(end_pfn - 1) + 1;
 472 
 473         /*
 474          * Convert to physical addresses, and round start upwards and end
 475          * downwards.
 476          */
 477         pg = (unsigned long)PAGE_ALIGN(__pa(start_pg));
 478         pgend = (unsigned long)__pa(end_pg) & PAGE_MASK;
 479 
 480         /*
 481          * If there are free pages between these, free the section of the
 482          * memmap array.
 483          */
 484         if (pg < pgend)
 485                 memblock_free(pg, pgend - pg);
 486 }
 487 
 488 /*
 489  * The mem_map array can get very big. Free the unused area of the memory map.
 490  */
 491 static void __init free_unused_memmap(void)
 492 {
 493         unsigned long start, prev_end = 0;
 494         struct memblock_region *reg;
 495 
 496         for_each_memblock(memory, reg) {
 497                 start = __phys_to_pfn(reg->base);
 498 
 499 #ifdef CONFIG_SPARSEMEM
 500                 /*
 501                  * Take care not to free memmap entries that don't exist due
 502                  * to SPARSEMEM sections which aren't present.
 503                  */
 504                 start = min(start, ALIGN(prev_end, PAGES_PER_SECTION));
 505 #endif
 506                 /*
 507                  * If we had a previous bank, and there is a space between the
 508                  * current bank and the previous, free it.
 509                  */
 510                 if (prev_end && prev_end < start)
 511                         free_memmap(prev_end, start);
 512 
 513                 /*
 514                  * Align up here since the VM subsystem insists that the
 515                  * memmap entries are valid from the bank end aligned to
 516                  * MAX_ORDER_NR_PAGES.
 517                  */
 518                 prev_end = ALIGN(__phys_to_pfn(reg->base + reg->size),
 519                                  MAX_ORDER_NR_PAGES);
 520         }
 521 
 522 #ifdef CONFIG_SPARSEMEM
 523         if (!IS_ALIGNED(prev_end, PAGES_PER_SECTION))
 524                 free_memmap(prev_end, ALIGN(prev_end, PAGES_PER_SECTION));
 525 #endif
 526 }
 527 #endif  /* !CONFIG_SPARSEMEM_VMEMMAP */
 528 
 529 /*
 530  * mem_init() marks the free areas in the mem_map and tells us how much memory
 531  * is free.  This is done after various parts of the system have claimed their
 532  * memory after the kernel image.
 533  */
 534 void __init mem_init(void)
 535 {
 536         if (swiotlb_force == SWIOTLB_FORCE ||
 537             max_pfn > (arm64_dma_phys_limit >> PAGE_SHIFT))
 538                 swiotlb_init(1);
 539         else
 540                 swiotlb_force = SWIOTLB_NO_FORCE;
 541 
 542         set_max_mapnr(max_pfn - PHYS_PFN_OFFSET);
 543 
 544 #ifndef CONFIG_SPARSEMEM_VMEMMAP
 545         free_unused_memmap();
 546 #endif
 547         /* this will put all unused low memory onto the freelists */
 548         memblock_free_all();
 549 
 550         mem_init_print_info(NULL);
 551 
 552         /*
 553          * Check boundaries twice: Some fundamental inconsistencies can be
 554          * detected at build time already.
 555          */
 556 #ifdef CONFIG_COMPAT
 557         BUILD_BUG_ON(TASK_SIZE_32 > DEFAULT_MAP_WINDOW_64);
 558 #endif
 559 
 560         if (PAGE_SIZE >= 16384 && get_num_physpages() <= 128) {
 561                 extern int sysctl_overcommit_memory;
 562                 /*
 563                  * On a machine this small we won't get anywhere without
 564                  * overcommit, so turn it on by default.
 565                  */
 566                 sysctl_overcommit_memory = OVERCOMMIT_ALWAYS;
 567         }
 568 }
 569 
 570 void free_initmem(void)
 571 {
 572         free_reserved_area(lm_alias(__init_begin),
 573                            lm_alias(__init_end),
 574                            0, "unused kernel");
 575         /*
 576          * Unmap the __init region but leave the VM area in place. This
 577          * prevents the region from being reused for kernel modules, which
 578          * is not supported by kallsyms.
 579          */
 580         unmap_kernel_range((u64)__init_begin, (u64)(__init_end - __init_begin));
 581 }
 582 
 583 #ifdef CONFIG_BLK_DEV_INITRD
 584 void __init free_initrd_mem(unsigned long start, unsigned long end)
 585 {
 586         unsigned long aligned_start, aligned_end;
 587 
 588         aligned_start = __virt_to_phys(start) & PAGE_MASK;
 589         aligned_end = PAGE_ALIGN(__virt_to_phys(end));
 590         memblock_free(aligned_start, aligned_end - aligned_start);
 591         free_reserved_area((void *)start, (void *)end, 0, "initrd");
 592 }
 593 #endif
 594 
 595 /*
 596  * Dump out memory limit information on panic.
 597  */
 598 static int dump_mem_limit(struct notifier_block *self, unsigned long v, void *p)
 599 {
 600         if (memory_limit != PHYS_ADDR_MAX) {
 601                 pr_emerg("Memory Limit: %llu MB\n", memory_limit >> 20);
 602         } else {
 603                 pr_emerg("Memory Limit: none\n");
 604         }
 605         return 0;
 606 }
 607 
 608 static struct notifier_block mem_limit_notifier = {
 609         .notifier_call = dump_mem_limit,
 610 };
 611 
 612 static int __init register_mem_limit_dumper(void)
 613 {
 614         atomic_notifier_chain_register(&panic_notifier_list,
 615                                        &mem_limit_notifier);
 616         return 0;
 617 }
 618 __initcall(register_mem_limit_dumper);