arch/arm64/mm/init.c

   1 /*
   2  * Based on arch/arm/mm/init.c
   3  *
   4  * Copyright (C) 1995-2005 Russell King
   5  * Copyright (C) 2012 ARM Ltd.
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <linux/kernel.h>
  21 #include <linux/export.h>
  22 #include <linux/errno.h>
  23 #include <linux/swap.h>
  24 #include <linux/init.h>
  25 #include <linux/bootmem.h>
  26 #include <linux/cache.h>
  27 #include <linux/mman.h>
  28 #include <linux/nodemask.h>
  29 #include <linux/initrd.h>
  30 #include <linux/gfp.h>
  31 #include <linux/memblock.h>
  32 #include <linux/sort.h>
  33 #include <linux/of.h>
  34 #include <linux/of_fdt.h>
  35 #include <linux/dma-mapping.h>
  36 #include <linux/dma-contiguous.h>
  37 #include <linux/efi.h>
  38 #include <linux/swiotlb.h>
  39 #include <linux/vmalloc.h>
  40 #include <linux/mm.h>
  41 #include <linux/kexec.h>
  42 #include <linux/crash_dump.h>
  43
  44 #include <asm/boot.h>
  45 #include <asm/fixmap.h>
  46 #include <asm/kasan.h>
  47 #include <asm/kernel-pgtable.h>
  48 #include <asm/memory.h>
  49 #include <asm/numa.h>
  50 #include <asm/sections.h>
  51 #include <asm/setup.h>
  52 #include <asm/sizes.h>
  53 #include <asm/tlb.h>
  54 #include <asm/alternative.h>
  55
  56 /*
  57  * We need to be able to catch inadvertent references to memstart_addr
  58  * that occur (potentially in generic code) before arm64_memblock_init()
  59  * executes, which assigns it its actual value. So use a default value
  60  * that cannot be mistaken for a real physical address.
  61  */
  62 s64 memstart_addr __ro_after_init = -1;
  63 phys_addr_t arm64_dma_phys_limit __ro_after_init;
  64
  65 #ifdef CONFIG_BLK_DEV_INITRD
  66 static int __init early_initrd(char *p)
  67 {
  68         unsigned long start, size;
  69         char *endp;
  70
  71         start = memparse(p, &endp);
  72         if (*endp == ',') {
  73                 size = memparse(endp + 1, NULL);
  74
  75                 initrd_start = start;
  76                 initrd_end = start + size;
  77         }
  78         return 0;
  79 }
  80 early_param("initrd", early_initrd);
  81 #endif
  82
  83 #ifdef CONFIG_KEXEC_CORE
  84 /*
  85  * reserve_crashkernel() - reserves memory for crash kernel
  86  *
  87  * This function reserves memory area given in "crashkernel=" kernel command
  88  * line parameter. The memory reserved is used by dump capture kernel when
  89  * primary kernel is crashing.
  90  */
  91 static void __init reserve_crashkernel(void)
  92 {
  93         unsigned long long crash_base, crash_size;
  94         int ret;
  95
  96         ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
  97                                 &crash_size, &crash_base);
  98         /* no crashkernel= or invalid value specified */
  99         if (ret || !crash_size)
 100                 return;
 101
 102         crash_size = PAGE_ALIGN(crash_size);
 103
 104         if (crash_base == 0) {
 105                 /* Current arm64 boot protocol requires 2MB alignment */
 106                 crash_base = memblock_find_in_range(0, ARCH_LOW_ADDRESS_LIMIT,
 107                                 crash_size, SZ_2M);
 108                 if (crash_base == 0) {
 109                         pr_warn("cannot allocate crashkernel (size:0x%llx)\n",
 110                                 crash_size);
 111                         return;
 112                 }
 113         } else {
 114                 /* User specifies base address explicitly. */
 115                 if (!memblock_is_region_memory(crash_base, crash_size)) {
 116                         pr_warn("cannot reserve crashkernel: region is not memory\n");
 117                         return;
 118                 }
 119
 120                 if (memblock_is_region_reserved(crash_base, crash_size)) {
 121                         pr_warn("cannot reserve crashkernel: region overlaps reserved memory\n");
 122                         return;
 123                 }
 124
 125                 if (!IS_ALIGNED(crash_base, SZ_2M)) {
 126                         pr_warn("cannot reserve crashkernel: base address is not 2MB aligned\n");
 127                         return;
 128                 }
 129         }
 130         memblock_reserve(crash_base, crash_size);
 131
 132         pr_info("crashkernel reserved: 0x%016llx - 0x%016llx (%lld MB)\n",
 133                 crash_base, crash_base + crash_size, crash_size >> 20);
 134
 135         crashk_res.start = crash_base;
 136         crashk_res.end = crash_base + crash_size - 1;
 137 }
 138
 139 static void __init kexec_reserve_crashkres_pages(void)
 140 {
 141 #ifdef CONFIG_HIBERNATION
 142         phys_addr_t addr;
 143         struct page *page;
 144
 145         if (!crashk_res.end)
 146                 return;
 147
 148         /*
 149          * To reduce the size of hibernation image, all the pages are
 150          * marked as Reserved initially.
 151          */
 152         for (addr = crashk_res.start; addr < (crashk_res.end + 1);
 153                         addr += PAGE_SIZE) {
 154                 page = phys_to_page(addr);
 155                 SetPageReserved(page);
 156         }
 157 #endif
 158 }
 159 #else
 160 static void __init reserve_crashkernel(void)
 161 {
 162 }
 163
 164 static void __init kexec_reserve_crashkres_pages(void)
 165 {
 166 }
 167 #endif /* CONFIG_KEXEC_CORE */
 168
 169 #ifdef CONFIG_CRASH_DUMP
 170 static int __init early_init_dt_scan_elfcorehdr(unsigned long node,
 171                 const char *uname, int depth, void *data)
 172 {
 173         const __be32 *reg;
 174         int len;
 175
 176         if (depth != 1 || strcmp(uname, "chosen") != 0)
 177                 return 0;
 178
 179         reg = of_get_flat_dt_prop(node, "linux,elfcorehdr", &len);
 180         if (!reg || (len < (dt_root_addr_cells + dt_root_size_cells)))
 181                 return 1;
 182
 183         elfcorehdr_addr = dt_mem_next_cell(dt_root_addr_cells, &reg);
 184         elfcorehdr_size = dt_mem_next_cell(dt_root_size_cells, &reg);
 185
 186         return 1;
 187 }
 188
 189 /*
 190  * reserve_elfcorehdr() - reserves memory for elf core header
 191  *
 192  * This function reserves the memory occupied by an elf core header
 193  * described in the device tree. This region contains all the
 194  * information about primary kernel's core image and is used by a dump
 195  * capture kernel to access the system memory on primary kernel.
 196  */
 197 static void __init reserve_elfcorehdr(void)
 198 {
 199         of_scan_flat_dt(early_init_dt_scan_elfcorehdr, NULL);
 200
 201         if (!elfcorehdr_size)
 202                 return;
 203
 204         if (memblock_is_region_reserved(elfcorehdr_addr, elfcorehdr_size)) {
 205                 pr_warn("elfcorehdr is overlapped\n");
 206                 return;
 207         }
 208
 209         memblock_reserve(elfcorehdr_addr, elfcorehdr_size);
 210
 211         pr_info("Reserving %lldKB of memory at 0x%llx for elfcorehdr\n",
 212                 elfcorehdr_size >> 10, elfcorehdr_addr);
 213 }
 214 #else
 215 static void __init reserve_elfcorehdr(void)
 216 {
 217 }
 218 #endif /* CONFIG_CRASH_DUMP */
 219 /*
 220  * Return the maximum physical address for ZONE_DMA32 (DMA_BIT_MASK(32)). It
 221  * currently assumes that for memory starting above 4G, 32-bit devices will
 222  * use a DMA offset.
 223  */
 224 static phys_addr_t __init max_zone_dma_phys(void)
 225 {
 226         phys_addr_t offset = memblock_start_of_DRAM() & GENMASK_ULL(63, 32);
 227         return min(offset + (1ULL << 32), memblock_end_of_DRAM());
 228 }
 229
 230 #ifdef CONFIG_NUMA
 231
 232 static void __init zone_sizes_init(unsigned long min, unsigned long max)
 233 {
 234         unsigned long max_zone_pfns[MAX_NR_ZONES]  = {0};
 235
 236         if (IS_ENABLED(CONFIG_ZONE_DMA32))
 237                 max_zone_pfns[ZONE_DMA32] = PFN_DOWN(max_zone_dma_phys());
 238         max_zone_pfns[ZONE_NORMAL] = max;
 239
 240         free_area_init_nodes(max_zone_pfns);
 241 }
 242
 243 #else
 244
 245 static void __init zone_sizes_init(unsigned long min, unsigned long max)
 246 {
 247         struct memblock_region *reg;
 248         unsigned long zone_size[MAX_NR_ZONES], zhole_size[MAX_NR_ZONES];
 249         unsigned long max_dma = min;
 250
 251         memset(zone_size, 0, sizeof(zone_size));
 252
 253         /* 4GB maximum for 32-bit only capable devices */
 254 #ifdef CONFIG_ZONE_DMA32
 255         max_dma = PFN_DOWN(arm64_dma_phys_limit);
 256         zone_size[ZONE_DMA32] = max_dma - min;
 257 #endif
 258         zone_size[ZONE_NORMAL] = max - max_dma;
 259
 260         memcpy(zhole_size, zone_size, sizeof(zhole_size));
 261
 262         for_each_memblock(memory, reg) {
 263                 unsigned long start = memblock_region_memory_base_pfn(reg);
 264                 unsigned long end = memblock_region_memory_end_pfn(reg);
 265
 266                 if (start >= max)
 267                         continue;
 268
 269 #ifdef CONFIG_ZONE_DMA32
 270                 if (start < max_dma) {
 271                         unsigned long dma_end = min(end, max_dma);
 272                         zhole_size[ZONE_DMA32] -= dma_end - start;
 273                 }
 274 #endif
 275                 if (end > max_dma) {
 276                         unsigned long normal_end = min(end, max);
 277                         unsigned long normal_start = max(start, max_dma);
 278                         zhole_size[ZONE_NORMAL] -= normal_end - normal_start;
 279                 }
 280         }
 281
 282         free_area_init_node(0, zone_size, min, zhole_size);
 283 }
 284
 285 #endif /* CONFIG_NUMA */
 286
 287 #ifdef CONFIG_HAVE_ARCH_PFN_VALID
 288 int pfn_valid(unsigned long pfn)
 289 {
 290         return memblock_is_map_memory(pfn << PAGE_SHIFT);
 291 }
 292 EXPORT_SYMBOL(pfn_valid);
 293 #endif
 294
 295 #ifndef CONFIG_SPARSEMEM
 296 static void __init arm64_memory_present(void)
 297 {
 298 }
 299 #else
 300 static void __init arm64_memory_present(void)
 301 {
 302         struct memblock_region *reg;
 303
 304         for_each_memblock(memory, reg) {
 305                 int nid = memblock_get_region_node(reg);
 306
 307                 memory_present(nid, memblock_region_memory_base_pfn(reg),
 308                                 memblock_region_memory_end_pfn(reg));
 309         }
 310 }
 311 #endif
 312
 313 static phys_addr_t memory_limit = (phys_addr_t)ULLONG_MAX;
 314
 315 /*
 316  * Limit the memory size that was specified via FDT.
 317  */
 318 static int __init early_mem(char *p)
 319 {
 320         if (!p)
 321                 return 1;
 322
 323         memory_limit = memparse(p, &p) & PAGE_MASK;
 324         pr_notice("Memory limited to %lldMB\n", memory_limit >> 20);
 325
 326         return 0;
 327 }
 328 early_param("mem", early_mem);
 329
 330 static int __init early_init_dt_scan_usablemem(unsigned long node,
 331                 const char *uname, int depth, void *data)
 332 {
 333         struct memblock_region *usablemem = data;
 334         const __be32 *reg;
 335         int len;
 336
 337         if (depth != 1 || strcmp(uname, "chosen") != 0)
 338                 return 0;
 339
 340         reg = of_get_flat_dt_prop(node, "linux,usable-memory-range", &len);
 341         if (!reg || (len < (dt_root_addr_cells + dt_root_size_cells)))
 342                 return 1;
 343
 344         usablemem->base = dt_mem_next_cell(dt_root_addr_cells, &reg);
 345         usablemem->size = dt_mem_next_cell(dt_root_size_cells, &reg);
 346
 347         return 1;
 348 }
 349
 350 static void __init fdt_enforce_memory_region(void)
 351 {
 352         struct memblock_region reg = {
 353                 .size = 0,
 354         };
 355
 356         of_scan_flat_dt(early_init_dt_scan_usablemem, &reg);
 357
 358         if (reg.size)
 359                 memblock_cap_memory_range(reg.base, reg.size);
 360 }
 361
 362 void __init arm64_memblock_init(void)
 363 {
 364         const s64 linear_region_size = -(s64)PAGE_OFFSET;
 365
 366         /* Handle linux,usable-memory-range property */
 367         fdt_enforce_memory_region();
 368
 369         /* Remove memory above our supported physical address size */
 370         memblock_remove(1ULL << PHYS_MASK_SHIFT, ULLONG_MAX);
 371
 372         /*
 373          * Ensure that the linear region takes up exactly half of the kernel
 374          * virtual address space. This way, we can distinguish a linear address
 375          * from a kernel/module/vmalloc address by testing a single bit.
 376          */
 377         BUILD_BUG_ON(linear_region_size != BIT(VA_BITS - 1));
 378
 379         /*
 380          * Select a suitable value for the base of physical memory.
 381          */
 382         memstart_addr = round_down(memblock_start_of_DRAM(),
 383                                    ARM64_MEMSTART_ALIGN);
 384
 385         /*
 386          * Remove the memory that we will not be able to cover with the
 387          * linear mapping. Take care not to clip the kernel which may be
 388          * high in memory.
 389          */
 390         memblock_remove(max_t(u64, memstart_addr + linear_region_size,
 391                         __pa_symbol(_end)), ULLONG_MAX);
 392         if (memstart_addr + linear_region_size < memblock_end_of_DRAM()) {
 393                 /* ensure that memstart_addr remains sufficiently aligned */
 394                 memstart_addr = round_up(memblock_end_of_DRAM() - linear_region_size,
 395                                          ARM64_MEMSTART_ALIGN);
 396                 memblock_remove(0, memstart_addr);
 397         }
 398
 399         /*
 400          * Apply the memory limit if it was set. Since the kernel may be loaded
 401          * high up in memory, add back the kernel region that must be accessible
 402          * via the linear mapping.
 403          */
 404         if (memory_limit != (phys_addr_t)ULLONG_MAX) {
 405                 memblock_mem_limit_remove_map(memory_limit);
 406                 memblock_add(__pa_symbol(_text), (u64)(_end - _text));
 407         }
 408
 409         if (IS_ENABLED(CONFIG_BLK_DEV_INITRD) && initrd_start) {
 410                 /*
 411                  * Add back the memory we just removed if it results in the
 412                  * initrd to become inaccessible via the linear mapping.
 413                  * Otherwise, this is a no-op
 414                  */
 415                 u64 base = initrd_start & PAGE_MASK;
 416                 u64 size = PAGE_ALIGN(initrd_end) - base;
 417
 418                 /*
 419                  * We can only add back the initrd memory if we don't end up
 420                  * with more memory than we can address via the linear mapping.
 421                  * It is up to the bootloader to position the kernel and the
 422                  * initrd reasonably close to each other (i.e., within 32 GB of
 423                  * each other) so that all granule/#levels combinations can
 424                  * always access both.
 425                  */
 426                 if (WARN(base < memblock_start_of_DRAM() ||
 427                          base + size > memblock_start_of_DRAM() +
 428                                        linear_region_size,
 429                         "initrd not fully accessible via the linear mapping -- please check your bootloader ...\n")) {
 430                         initrd_start = 0;
 431                 } else {
 432                         memblock_remove(base, size); /* clear MEMBLOCK_ flags */
 433                         memblock_add(base, size);
 434                         memblock_reserve(base, size);
 435                 }
 436         }
 437
 438         if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
 439                 extern u16 memstart_offset_seed;
 440                 u64 range = linear_region_size -
 441                             (memblock_end_of_DRAM() - memblock_start_of_DRAM());
 442
 443                 /*
 444                  * If the size of the linear region exceeds, by a sufficient
 445                  * margin, the size of the region that the available physical
 446                  * memory spans, randomize the linear region as well.
 447                  */
 448                 if (memstart_offset_seed > 0 && range >= ARM64_MEMSTART_ALIGN) {
 449                         range = range / ARM64_MEMSTART_ALIGN + 1;
 450                         memstart_addr -= ARM64_MEMSTART_ALIGN *
 451                                          ((range * memstart_offset_seed) >> 16);
 452                 }
 453         }
 454
 455         /*
 456          * Register the kernel text, kernel data, initrd, and initial
 457          * pagetables with memblock.
 458          */
 459         memblock_reserve(__pa_symbol(_text), _end - _text);
 460 #ifdef CONFIG_BLK_DEV_INITRD
 461         if (initrd_start) {
 462                 memblock_reserve(initrd_start, initrd_end - initrd_start);
 463
 464                 /* the generic initrd code expects virtual addresses */
 465                 initrd_start = __phys_to_virt(initrd_start);
 466                 initrd_end = __phys_to_virt(initrd_end);
 467         }
 468 #endif
 469
 470         early_init_fdt_scan_reserved_mem();
 471
 472         /* 4GB maximum for 32-bit only capable devices */
 473         if (IS_ENABLED(CONFIG_ZONE_DMA32))
 474                 arm64_dma_phys_limit = max_zone_dma_phys();
 475         else
 476                 arm64_dma_phys_limit = PHYS_MASK + 1;
 477
 478         reserve_crashkernel();
 479
 480         reserve_elfcorehdr();
 481
 482         high_memory = __va(memblock_end_of_DRAM() - 1) + 1;
 483
 484         dma_contiguous_reserve(arm64_dma_phys_limit);
 485
 486         memblock_allow_resize();
 487 }
 488
 489 void __init bootmem_init(void)
 490 {
 491         unsigned long min, max;
 492
 493         min = PFN_UP(memblock_start_of_DRAM());
 494         max = PFN_DOWN(memblock_end_of_DRAM());
 495
 496         early_memtest(min << PAGE_SHIFT, max << PAGE_SHIFT);
 497
 498         max_pfn = max_low_pfn = max;
 499
 500         arm64_numa_init();
 501         /*
 502          * Sparsemem tries to allocate bootmem in memory_present(), so must be
 503          * done after the fixed reservations.
 504          */
 505         arm64_memory_present();
 506
 507         sparse_init();
 508         zone_sizes_init(min, max);
 509
 510         memblock_dump_all();
 511 }
 512
 513 #ifndef CONFIG_SPARSEMEM_VMEMMAP
 514 static inline void free_memmap(unsigned long start_pfn, unsigned long end_pfn)
 515 {
 516         struct page *start_pg, *end_pg;
 517         unsigned long pg, pgend;
 518
 519         /*
 520          * Convert start_pfn/end_pfn to a struct page pointer.
 521          */
 522         start_pg = pfn_to_page(start_pfn - 1) + 1;
 523         end_pg = pfn_to_page(end_pfn - 1) + 1;
 524
 525         /*
 526          * Convert to physical addresses, and round start upwards and end
 527          * downwards.
 528          */
 529         pg = (unsigned long)PAGE_ALIGN(__pa(start_pg));
 530         pgend = (unsigned long)__pa(end_pg) & PAGE_MASK;
 531
 532         /*
 533          * If there are free pages between these, free the section of the
 534          * memmap array.
 535          */
 536         if (pg < pgend)
 537                 free_bootmem(pg, pgend - pg);
 538 }
 539
 540 /*
 541  * The mem_map array can get very big. Free the unused area of the memory map.
 542  */
 543 static void __init free_unused_memmap(void)
 544 {
 545         unsigned long start, prev_end = 0;
 546         struct memblock_region *reg;
 547
 548         for_each_memblock(memory, reg) {
 549                 start = __phys_to_pfn(reg->base);
 550
 551 #ifdef CONFIG_SPARSEMEM
 552                 /*
 553                  * Take care not to free memmap entries that don't exist due
 554                  * to SPARSEMEM sections which aren't present.
 555                  */
 556                 start = min(start, ALIGN(prev_end, PAGES_PER_SECTION));
 557 #endif
 558                 /*
 559                  * If we had a previous bank, and there is a space between the
 560                  * current bank and the previous, free it.
 561                  */
 562                 if (prev_end && prev_end < start)
 563                         free_memmap(prev_end, start);
 564
 565                 /*
 566                  * Align up here since the VM subsystem insists that the
 567                  * memmap entries are valid from the bank end aligned to
 568                  * MAX_ORDER_NR_PAGES.
 569                  */
 570                 prev_end = ALIGN(__phys_to_pfn(reg->base + reg->size),
 571                                  MAX_ORDER_NR_PAGES);
 572         }
 573
 574 #ifdef CONFIG_SPARSEMEM
 575         if (!IS_ALIGNED(prev_end, PAGES_PER_SECTION))
 576                 free_memmap(prev_end, ALIGN(prev_end, PAGES_PER_SECTION));
 577 #endif
 578 }
 579 #endif  /* !CONFIG_SPARSEMEM_VMEMMAP */
 580
 581 /*
 582  * mem_init() marks the free areas in the mem_map and tells us how much memory
 583  * is free.  This is done after various parts of the system have claimed their
 584  * memory after the kernel image.
 585  */
 586 void __init mem_init(void)
 587 {
 588         if (swiotlb_force == SWIOTLB_FORCE ||
 589             max_pfn > (arm64_dma_phys_limit >> PAGE_SHIFT))
 590                 swiotlb_init(1);
 591         else
 592                 swiotlb_force = SWIOTLB_NO_FORCE;
 593
 594         set_max_mapnr(pfn_to_page(max_pfn) - mem_map);
 595
 596 #ifndef CONFIG_SPARSEMEM_VMEMMAP
 597         free_unused_memmap();
 598 #endif
 599         /* this will put all unused low memory onto the freelists */
 600         free_all_bootmem();
 601
 602         kexec_reserve_crashkres_pages();
 603
 604         mem_init_print_info(NULL);
 605
 606         /*
 607          * Check boundaries twice: Some fundamental inconsistencies can be
 608          * detected at build time already.
 609          */
 610 #ifdef CONFIG_COMPAT
 611         BUILD_BUG_ON(TASK_SIZE_32                       > TASK_SIZE_64);
 612 #endif
 613
 614         /*
 615          * Make sure we chose the upper bound of sizeof(struct page)
 616          * correctly.
 617          */
 618         BUILD_BUG_ON(sizeof(struct page) > (1 << STRUCT_PAGE_MAX_SHIFT));
 619
 620         if (PAGE_SIZE >= 16384 && get_num_physpages() <= 128) {
 621                 extern int sysctl_overcommit_memory;
 622                 /*
 623                  * On a machine this small we won't get anywhere without
 624                  * overcommit, so turn it on by default.
 625                  */
 626                 sysctl_overcommit_memory = OVERCOMMIT_ALWAYS;
 627         }
 628 }
 629
 630 void free_initmem(void)
 631 {
 632         free_reserved_area(lm_alias(__init_begin),
 633                            lm_alias(__init_end),
 634                            0, "unused kernel");
 635         /*
 636          * Unmap the __init region but leave the VM area in place. This
 637          * prevents the region from being reused for kernel modules, which
 638          * is not supported by kallsyms.
 639          */
 640         unmap_kernel_range((u64)__init_begin, (u64)(__init_end - __init_begin));
 641 }
 642
 643 #ifdef CONFIG_BLK_DEV_INITRD
 644
 645 static int keep_initrd __initdata;
 646
 647 void __init free_initrd_mem(unsigned long start, unsigned long end)
 648 {
 649         if (!keep_initrd)
 650                 free_reserved_area((void *)start, (void *)end, 0, "initrd");
 651 }
 652
 653 static int __init keepinitrd_setup(char *__unused)
 654 {
 655         keep_initrd = 1;
 656         return 1;
 657 }
 658
 659 __setup("keepinitrd", keepinitrd_setup);
 660 #endif
 661
 662 /*
 663  * Dump out memory limit information on panic.
 664  */
 665 static int dump_mem_limit(struct notifier_block *self, unsigned long v, void *p)
 666 {
 667         if (memory_limit != (phys_addr_t)ULLONG_MAX) {
 668                 pr_emerg("Memory Limit: %llu MB\n", memory_limit >> 20);
 669         } else {
 670                 pr_emerg("Memory Limit: none\n");
 671         }
 672         return 0;
 673 }
 674
 675 static struct notifier_block mem_limit_notifier = {
 676         .notifier_call = dump_mem_limit,
 677 };
 678
 679 static int __init register_mem_limit_dumper(void)
 680 {
 681         atomic_notifier_chain_register(&panic_notifier_list,
 682                                        &mem_limit_notifier);
 683         return 0;
 684 }
 685 __initcall(register_mem_limit_dumper);