arch/arm64/mm/init.c

   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-direct.h>
  24 #include <linux/dma-mapping.h>
  25 #include <linux/dma-contiguous.h>
  26 #include <linux/efi.h>
  27 #include <linux/swiotlb.h>
  28 #include <linux/vmalloc.h>
  29 #include <linux/mm.h>
  30 #include <linux/kexec.h>
  31 #include <linux/crash_dump.h>
  32
  33 #include <asm/boot.h>
  34 #include <asm/fixmap.h>
  35 #include <asm/kasan.h>
  36 #include <asm/kernel-pgtable.h>
  37 #include <asm/memory.h>
  38 #include <asm/numa.h>
  39 #include <asm/sections.h>
  40 #include <asm/setup.h>
  41 #include <linux/sizes.h>
  42 #include <asm/tlb.h>
  43 #include <asm/alternative.h>
  44
  45 #define ARM64_ZONE_DMA_BITS     30
  46
  47 /*
  48  * We need to be able to catch inadvertent references to memstart_addr
  49  * that occur (potentially in generic code) before arm64_memblock_init()
  50  * executes, which assigns it its actual value. So use a default value
  51  * that cannot be mistaken for a real physical address.
  52  */
  53 s64 memstart_addr __ro_after_init = -1;
  54 EXPORT_SYMBOL(memstart_addr);
  55
  56 s64 physvirt_offset __ro_after_init;
  57 EXPORT_SYMBOL(physvirt_offset);
  58
  59 struct page *vmemmap __ro_after_init;
  60 EXPORT_SYMBOL(vmemmap);
  61
  62 /*
  63  * We create both ZONE_DMA and ZONE_DMA32. ZONE_DMA covers the first 1G of
  64  * memory as some devices, namely the Raspberry Pi 4, have peripherals with
  65  * this limited view of the memory. ZONE_DMA32 will cover the rest of the 32
  66  * bit addressable memory area.
  67  */
  68 phys_addr_t arm64_dma_phys_limit __ro_after_init;
  69 static phys_addr_t arm64_dma32_phys_limit __ro_after_init;
  70
  71 #ifdef CONFIG_KEXEC_CORE
  72 /*
  73  * reserve_crashkernel() - reserves memory for crash kernel
  74  *
  75  * This function reserves memory area given in "crashkernel=" kernel command
  76  * line parameter. The memory reserved is used by dump capture kernel when
  77  * primary kernel is crashing.
  78  */
  79 static void __init reserve_crashkernel(void)
  80 {
  81         unsigned long long crash_base, crash_size;
  82         int ret;
  83
  84         ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
  85                                 &crash_size, &crash_base);
  86         /* no crashkernel= or invalid value specified */
  87         if (ret || !crash_size)
  88                 return;
  89
  90         crash_size = PAGE_ALIGN(crash_size);
  91
  92         if (crash_base == 0) {
  93                 /* Current arm64 boot protocol requires 2MB alignment */
  94                 crash_base = memblock_find_in_range(0, arm64_dma32_phys_limit,
  95                                 crash_size, SZ_2M);
  96                 if (crash_base == 0) {
  97                         pr_warn("cannot allocate crashkernel (size:0x%llx)\n",
  98                                 crash_size);
  99                         return;
 100                 }
 101         } else {
 102                 /* User specifies base address explicitly. */
 103                 if (!memblock_is_region_memory(crash_base, crash_size)) {
 104                         pr_warn("cannot reserve crashkernel: region is not memory\n");
 105                         return;
 106                 }
 107
 108                 if (memblock_is_region_reserved(crash_base, crash_size)) {
 109                         pr_warn("cannot reserve crashkernel: region overlaps reserved memory\n");
 110                         return;
 111                 }
 112
 113                 if (!IS_ALIGNED(crash_base, SZ_2M)) {
 114                         pr_warn("cannot reserve crashkernel: base address is not 2MB aligned\n");
 115                         return;
 116                 }
 117         }
 118         memblock_reserve(crash_base, crash_size);
 119
 120         pr_info("crashkernel reserved: 0x%016llx - 0x%016llx (%lld MB)\n",
 121                 crash_base, crash_base + crash_size, crash_size >> 20);
 122
 123         crashk_res.start = crash_base;
 124         crashk_res.end = crash_base + crash_size - 1;
 125 }
 126 #else
 127 static void __init reserve_crashkernel(void)
 128 {
 129 }
 130 #endif /* CONFIG_KEXEC_CORE */
 131
 132 #ifdef CONFIG_CRASH_DUMP
 133 static int __init early_init_dt_scan_elfcorehdr(unsigned long node,
 134                 const char *uname, int depth, void *data)
 135 {
 136         const __be32 *reg;
 137         int len;
 138
 139         if (depth != 1 || strcmp(uname, "chosen") != 0)
 140                 return 0;
 141
 142         reg = of_get_flat_dt_prop(node, "linux,elfcorehdr", &len);
 143         if (!reg || (len < (dt_root_addr_cells + dt_root_size_cells)))
 144                 return 1;
 145
 146         elfcorehdr_addr = dt_mem_next_cell(dt_root_addr_cells, &reg);
 147         elfcorehdr_size = dt_mem_next_cell(dt_root_size_cells, &reg);
 148
 149         return 1;
 150 }
 151
 152 /*
 153  * reserve_elfcorehdr() - reserves memory for elf core header
 154  *
 155  * This function reserves the memory occupied by an elf core header
 156  * described in the device tree. This region contains all the
 157  * information about primary kernel's core image and is used by a dump
 158  * capture kernel to access the system memory on primary kernel.
 159  */
 160 static void __init reserve_elfcorehdr(void)
 161 {
 162         of_scan_flat_dt(early_init_dt_scan_elfcorehdr, NULL);
 163
 164         if (!elfcorehdr_size)
 165                 return;
 166
 167         if (memblock_is_region_reserved(elfcorehdr_addr, elfcorehdr_size)) {
 168                 pr_warn("elfcorehdr is overlapped\n");
 169                 return;
 170         }
 171
 172         memblock_reserve(elfcorehdr_addr, elfcorehdr_size);
 173
 174         pr_info("Reserving %lldKB of memory at 0x%llx for elfcorehdr\n",
 175                 elfcorehdr_size >> 10, elfcorehdr_addr);
 176 }
 177 #else
 178 static void __init reserve_elfcorehdr(void)
 179 {
 180 }
 181 #endif /* CONFIG_CRASH_DUMP */
 182
 183 /*
 184  * Return the maximum physical address for a zone with a given address size
 185  * limit. It currently assumes that for memory starting above 4G, 32-bit
 186  * devices will use a DMA offset.
 187  */
 188 static phys_addr_t __init max_zone_phys(unsigned int zone_bits)
 189 {
 190         phys_addr_t offset = memblock_start_of_DRAM() & GENMASK_ULL(63, zone_bits);
 191         return min(offset + (1ULL << zone_bits), memblock_end_of_DRAM());
 192 }
 193
 194 #ifdef CONFIG_NUMA
 195
 196 static void __init zone_sizes_init(unsigned long min, unsigned long max)
 197 {
 198         unsigned long max_zone_pfns[MAX_NR_ZONES]  = {0};
 199
 200 #ifdef CONFIG_ZONE_DMA
 201         max_zone_pfns[ZONE_DMA] = PFN_DOWN(arm64_dma_phys_limit);
 202 #endif
 203 #ifdef CONFIG_ZONE_DMA32
 204         max_zone_pfns[ZONE_DMA32] = PFN_DOWN(arm64_dma32_phys_limit);
 205 #endif
 206         max_zone_pfns[ZONE_NORMAL] = max;
 207
 208         free_area_init_nodes(max_zone_pfns);
 209 }
 210
 211 #else
 212
 213 static void __init zone_sizes_init(unsigned long min, unsigned long max)
 214 {
 215         struct memblock_region *reg;
 216         unsigned long zone_size[MAX_NR_ZONES], zhole_size[MAX_NR_ZONES];
 217         unsigned long __maybe_unused max_dma, max_dma32;
 218
 219         memset(zone_size, 0, sizeof(zone_size));
 220
 221         max_dma = max_dma32 = min;
 222 #ifdef CONFIG_ZONE_DMA
 223         max_dma = max_dma32 = PFN_DOWN(arm64_dma_phys_limit);
 224         zone_size[ZONE_DMA] = max_dma - min;
 225 #endif
 226 #ifdef CONFIG_ZONE_DMA32
 227         max_dma32 = PFN_DOWN(arm64_dma32_phys_limit);
 228         zone_size[ZONE_DMA32] = max_dma32 - max_dma;
 229 #endif
 230         zone_size[ZONE_NORMAL] = max - max_dma32;
 231
 232         memcpy(zhole_size, zone_size, sizeof(zhole_size));
 233
 234         for_each_memblock(memory, reg) {
 235                 unsigned long start = memblock_region_memory_base_pfn(reg);
 236                 unsigned long end = memblock_region_memory_end_pfn(reg);
 237
 238 #ifdef CONFIG_ZONE_DMA
 239                 if (start >= min && start < max_dma) {
 240                         unsigned long dma_end = min(end, max_dma);
 241                         zhole_size[ZONE_DMA] -= dma_end - start;
 242                         start = dma_end;
 243                 }
 244 #endif
 245 #ifdef CONFIG_ZONE_DMA32
 246                 if (start >= max_dma && start < max_dma32) {
 247                         unsigned long dma32_end = min(end, max_dma32);
 248                         zhole_size[ZONE_DMA32] -= dma32_end - start;
 249                         start = dma32_end;
 250                 }
 251 #endif
 252                 if (start >= max_dma32 && start < max) {
 253                         unsigned long normal_end = min(end, max);
 254                         zhole_size[ZONE_NORMAL] -= normal_end - start;
 255                 }
 256         }
 257
 258         free_area_init_node(0, zone_size, min, zhole_size);
 259 }
 260
 261 #endif /* CONFIG_NUMA */
 262
 263 int pfn_valid(unsigned long pfn)
 264 {
 265         phys_addr_t addr = pfn << PAGE_SHIFT;
 266
 267         if ((addr >> PAGE_SHIFT) != pfn)
 268                 return 0;
 269
 270 #ifdef CONFIG_SPARSEMEM
 271         if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
 272                 return 0;
 273
 274         if (!valid_section(__nr_to_section(pfn_to_section_nr(pfn))))
 275                 return 0;
 276 #endif
 277         return memblock_is_map_memory(addr);
 278 }
 279 EXPORT_SYMBOL(pfn_valid);
 280
 281 static phys_addr_t memory_limit = PHYS_ADDR_MAX;
 282
 283 /*
 284  * Limit the memory size that was specified via FDT.
 285  */
 286 static int __init early_mem(char *p)
 287 {
 288         if (!p)
 289                 return 1;
 290
 291         memory_limit = memparse(p, &p) & PAGE_MASK;
 292         pr_notice("Memory limited to %lldMB\n", memory_limit >> 20);
 293
 294         return 0;
 295 }
 296 early_param("mem", early_mem);
 297
 298 static int __init early_init_dt_scan_usablemem(unsigned long node,
 299                 const char *uname, int depth, void *data)
 300 {
 301         struct memblock_region *usablemem = data;
 302         const __be32 *reg;
 303         int len;
 304
 305         if (depth != 1 || strcmp(uname, "chosen") != 0)
 306                 return 0;
 307
 308         reg = of_get_flat_dt_prop(node, "linux,usable-memory-range", &len);
 309         if (!reg || (len < (dt_root_addr_cells + dt_root_size_cells)))
 310                 return 1;
 311
 312         usablemem->base = dt_mem_next_cell(dt_root_addr_cells, &reg);
 313         usablemem->size = dt_mem_next_cell(dt_root_size_cells, &reg);
 314
 315         return 1;
 316 }
 317
 318 static void __init fdt_enforce_memory_region(void)
 319 {
 320         struct memblock_region reg = {
 321                 .size = 0,
 322         };
 323
 324         of_scan_flat_dt(early_init_dt_scan_usablemem, &reg);
 325
 326         if (reg.size)
 327                 memblock_cap_memory_range(reg.base, reg.size);
 328 }
 329
 330 void __init arm64_memblock_init(void)
 331 {
 332         const s64 linear_region_size = BIT(vabits_actual - 1);
 333
 334         /* Handle linux,usable-memory-range property */
 335         fdt_enforce_memory_region();
 336
 337         /* Remove memory above our supported physical address size */
 338         memblock_remove(1ULL << PHYS_MASK_SHIFT, ULLONG_MAX);
 339
 340         /*
 341          * Select a suitable value for the base of physical memory.
 342          */
 343         memstart_addr = round_down(memblock_start_of_DRAM(),
 344                                    ARM64_MEMSTART_ALIGN);
 345
 346         physvirt_offset = PHYS_OFFSET - PAGE_OFFSET;
 347
 348         vmemmap = ((struct page *)VMEMMAP_START - (memstart_addr >> PAGE_SHIFT));
 349
 350         /*
 351          * If we are running with a 52-bit kernel VA config on a system that
 352          * does not support it, we have to offset our vmemmap and physvirt_offset
 353          * s.t. we avoid the 52-bit portion of the direct linear map
 354          */
 355         if (IS_ENABLED(CONFIG_ARM64_VA_BITS_52) && (vabits_actual != 52)) {
 356                 vmemmap += (_PAGE_OFFSET(48) - _PAGE_OFFSET(52)) >> PAGE_SHIFT;
 357                 physvirt_offset = PHYS_OFFSET - _PAGE_OFFSET(48);
 358         }
 359
 360         /*
 361          * Remove the memory that we will not be able to cover with the
 362          * linear mapping. Take care not to clip the kernel which may be
 363          * high in memory.
 364          */
 365         memblock_remove(max_t(u64, memstart_addr + linear_region_size,
 366                         __pa_symbol(_end)), ULLONG_MAX);
 367         if (memstart_addr + linear_region_size < memblock_end_of_DRAM()) {
 368                 /* ensure that memstart_addr remains sufficiently aligned */
 369                 memstart_addr = round_up(memblock_end_of_DRAM() - linear_region_size,
 370                                          ARM64_MEMSTART_ALIGN);
 371                 memblock_remove(0, memstart_addr);
 372         }
 373
 374         /*
 375          * Apply the memory limit if it was set. Since the kernel may be loaded
 376          * high up in memory, add back the kernel region that must be accessible
 377          * via the linear mapping.
 378          */
 379         if (memory_limit != PHYS_ADDR_MAX) {
 380                 memblock_mem_limit_remove_map(memory_limit);
 381                 memblock_add(__pa_symbol(_text), (u64)(_end - _text));
 382         }
 383
 384         if (IS_ENABLED(CONFIG_BLK_DEV_INITRD) && phys_initrd_size) {
 385                 /*
 386                  * Add back the memory we just removed if it results in the
 387                  * initrd to become inaccessible via the linear mapping.
 388                  * Otherwise, this is a no-op
 389                  */
 390                 u64 base = phys_initrd_start & PAGE_MASK;
 391                 u64 size = PAGE_ALIGN(phys_initrd_start + phys_initrd_size) - base;
 392
 393                 /*
 394                  * We can only add back the initrd memory if we don't end up
 395                  * with more memory than we can address via the linear mapping.
 396                  * It is up to the bootloader to position the kernel and the
 397                  * initrd reasonably close to each other (i.e., within 32 GB of
 398                  * each other) so that all granule/#levels combinations can
 399                  * always access both.
 400                  */
 401                 if (WARN(base < memblock_start_of_DRAM() ||
 402                          base + size > memblock_start_of_DRAM() +
 403                                        linear_region_size,
 404                         "initrd not fully accessible via the linear mapping -- please check your bootloader ...\n")) {
 405                         phys_initrd_size = 0;
 406                 } else {
 407                         memblock_remove(base, size); /* clear MEMBLOCK_ flags */
 408                         memblock_add(base, size);
 409                         memblock_reserve(base, size);
 410                 }
 411         }
 412
 413         if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
 414                 extern u16 memstart_offset_seed;
 415                 u64 range = linear_region_size -
 416                             (memblock_end_of_DRAM() - memblock_start_of_DRAM());
 417
 418                 /*
 419                  * If the size of the linear region exceeds, by a sufficient
 420                  * margin, the size of the region that the available physical
 421                  * memory spans, randomize the linear region as well.
 422                  */
 423                 if (memstart_offset_seed > 0 && range >= ARM64_MEMSTART_ALIGN) {
 424                         range /= ARM64_MEMSTART_ALIGN;
 425                         memstart_addr -= ARM64_MEMSTART_ALIGN *
 426                                          ((range * memstart_offset_seed) >> 16);
 427                 }
 428         }
 429
 430         /*
 431          * Register the kernel text, kernel data, initrd, and initial
 432          * pagetables with memblock.
 433          */
 434         memblock_reserve(__pa_symbol(_text), _end - _text);
 435         if (IS_ENABLED(CONFIG_BLK_DEV_INITRD) && phys_initrd_size) {
 436                 /* the generic initrd code expects virtual addresses */
 437                 initrd_start = __phys_to_virt(phys_initrd_start);
 438                 initrd_end = initrd_start + phys_initrd_size;
 439         }
 440
 441         early_init_fdt_scan_reserved_mem();
 442
 443         if (IS_ENABLED(CONFIG_ZONE_DMA)) {
 444                 zone_dma_bits = ARM64_ZONE_DMA_BITS;
 445                 arm64_dma_phys_limit = max_zone_phys(ARM64_ZONE_DMA_BITS);
 446         }
 447
 448         if (IS_ENABLED(CONFIG_ZONE_DMA32))
 449                 arm64_dma32_phys_limit = max_zone_phys(32);
 450         else
 451                 arm64_dma32_phys_limit = PHYS_MASK + 1;
 452
 453         reserve_crashkernel();
 454
 455         reserve_elfcorehdr();
 456
 457         high_memory = __va(memblock_end_of_DRAM() - 1) + 1;
 458
 459         dma_contiguous_reserve(arm64_dma32_phys_limit);
 460 }
 461
 462 void __init bootmem_init(void)
 463 {
 464         unsigned long min, max;
 465
 466         min = PFN_UP(memblock_start_of_DRAM());
 467         max = PFN_DOWN(memblock_end_of_DRAM());
 468
 469         early_memtest(min << PAGE_SHIFT, max << PAGE_SHIFT);
 470
 471         max_pfn = max_low_pfn = max;
 472         min_low_pfn = min;
 473
 474         arm64_numa_init();
 475         /*
 476          * Sparsemem tries to allocate bootmem in memory_present(), so must be
 477          * done after the fixed reservations.
 478          */
 479         memblocks_present();
 480
 481         sparse_init();
 482         zone_sizes_init(min, max);
 483
 484         memblock_dump_all();
 485 }
 486
 487 #ifndef CONFIG_SPARSEMEM_VMEMMAP
 488 static inline void free_memmap(unsigned long start_pfn, unsigned long end_pfn)
 489 {
 490         struct page *start_pg, *end_pg;
 491         unsigned long pg, pgend;
 492
 493         /*
 494          * Convert start_pfn/end_pfn to a struct page pointer.
 495          */
 496         start_pg = pfn_to_page(start_pfn - 1) + 1;
 497         end_pg = pfn_to_page(end_pfn - 1) + 1;
 498
 499         /*
 500          * Convert to physical addresses, and round start upwards and end
 501          * downwards.
 502          */
 503         pg = (unsigned long)PAGE_ALIGN(__pa(start_pg));
 504         pgend = (unsigned long)__pa(end_pg) & PAGE_MASK;
 505
 506         /*
 507          * If there are free pages between these, free the section of the
 508          * memmap array.
 509          */
 510         if (pg < pgend)
 511                 memblock_free(pg, pgend - pg);
 512 }
 513
 514 /*
 515  * The mem_map array can get very big. Free the unused area of the memory map.
 516  */
 517 static void __init free_unused_memmap(void)
 518 {
 519         unsigned long start, prev_end = 0;
 520         struct memblock_region *reg;
 521
 522         for_each_memblock(memory, reg) {
 523                 start = __phys_to_pfn(reg->base);
 524
 525 #ifdef CONFIG_SPARSEMEM
 526                 /*
 527                  * Take care not to free memmap entries that don't exist due
 528                  * to SPARSEMEM sections which aren't present.
 529                  */
 530                 start = min(start, ALIGN(prev_end, PAGES_PER_SECTION));
 531 #endif
 532                 /*
 533                  * If we had a previous bank, and there is a space between the
 534                  * current bank and the previous, free it.
 535                  */
 536                 if (prev_end && prev_end < start)
 537                         free_memmap(prev_end, start);
 538
 539                 /*
 540                  * Align up here since the VM subsystem insists that the
 541                  * memmap entries are valid from the bank end aligned to
 542                  * MAX_ORDER_NR_PAGES.
 543                  */
 544                 prev_end = ALIGN(__phys_to_pfn(reg->base + reg->size),
 545                                  MAX_ORDER_NR_PAGES);
 546         }
 547
 548 #ifdef CONFIG_SPARSEMEM
 549         if (!IS_ALIGNED(prev_end, PAGES_PER_SECTION))
 550                 free_memmap(prev_end, ALIGN(prev_end, PAGES_PER_SECTION));
 551 #endif
 552 }
 553 #endif  /* !CONFIG_SPARSEMEM_VMEMMAP */
 554
 555 /*
 556  * mem_init() marks the free areas in the mem_map and tells us how much memory
 557  * is free.  This is done after various parts of the system have claimed their
 558  * memory after the kernel image.
 559  */
 560 void __init mem_init(void)
 561 {
 562         if (swiotlb_force == SWIOTLB_FORCE ||
 563             max_pfn > PFN_DOWN(arm64_dma_phys_limit ? : arm64_dma32_phys_limit))
 564                 swiotlb_init(1);
 565         else
 566                 swiotlb_force = SWIOTLB_NO_FORCE;
 567
 568         set_max_mapnr(max_pfn - PHYS_PFN_OFFSET);
 569
 570 #ifndef CONFIG_SPARSEMEM_VMEMMAP
 571         free_unused_memmap();
 572 #endif
 573         /* this will put all unused low memory onto the freelists */
 574         memblock_free_all();
 575
 576         mem_init_print_info(NULL);
 577
 578         /*
 579          * Check boundaries twice: Some fundamental inconsistencies can be
 580          * detected at build time already.
 581          */
 582 #ifdef CONFIG_COMPAT
 583         BUILD_BUG_ON(TASK_SIZE_32 > DEFAULT_MAP_WINDOW_64);
 584 #endif
 585
 586         if (PAGE_SIZE >= 16384 && get_num_physpages() <= 128) {
 587                 extern int sysctl_overcommit_memory;
 588                 /*
 589                  * On a machine this small we won't get anywhere without
 590                  * overcommit, so turn it on by default.
 591                  */
 592                 sysctl_overcommit_memory = OVERCOMMIT_ALWAYS;
 593         }
 594 }
 595
 596 void free_initmem(void)
 597 {
 598         free_reserved_area(lm_alias(__init_begin),
 599                            lm_alias(__init_end),
 600                            POISON_FREE_INITMEM, "unused kernel");
 601         /*
 602          * Unmap the __init region but leave the VM area in place. This
 603          * prevents the region from being reused for kernel modules, which
 604          * is not supported by kallsyms.
 605          */
 606         unmap_kernel_range((u64)__init_begin, (u64)(__init_end - __init_begin));
 607 }
 608
 609 /*
 610  * Dump out memory limit information on panic.
 611  */
 612 static int dump_mem_limit(struct notifier_block *self, unsigned long v, void *p)
 613 {
 614         if (memory_limit != PHYS_ADDR_MAX) {
 615                 pr_emerg("Memory Limit: %llu MB\n", memory_limit >> 20);
 616         } else {
 617                 pr_emerg("Memory Limit: none\n");
 618         }
 619         return 0;
 620 }
 621
 622 static struct notifier_block mem_limit_notifier = {
 623         .notifier_call = dump_mem_limit,
 624 };
 625
 626 static int __init register_mem_limit_dumper(void)
 627 {
 628         atomic_notifier_chain_register(&panic_notifier_list,
 629                                        &mem_limit_notifier);
 630         return 0;
 631 }
 632 __initcall(register_mem_limit_dumper);