arch/arm64/mm/mmu.c

   1 /*
   2  * Based on arch/arm/mm/mmu.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/export.h>
  21 #include <linux/kernel.h>
  22 #include <linux/errno.h>
  23 #include <linux/init.h>
  24 #include <linux/libfdt.h>
  25 #include <linux/mman.h>
  26 #include <linux/nodemask.h>
  27 #include <linux/memblock.h>
  28 #include <linux/fs.h>
  29 #include <linux/io.h>
  30 #include <linux/slab.h>
  31 #include <linux/stop_machine.h>
  32
  33 #include <asm/barrier.h>
  34 #include <asm/cputype.h>
  35 #include <asm/fixmap.h>
  36 #include <asm/kernel-pgtable.h>
  37 #include <asm/sections.h>
  38 #include <asm/setup.h>
  39 #include <asm/sizes.h>
  40 #include <asm/tlb.h>
  41 #include <asm/memblock.h>
  42 #include <asm/mmu_context.h>
  43
  44 #include "mm.h"
  45
  46 u64 idmap_t0sz = TCR_T0SZ(VA_BITS);
  47
  48 /*
  49  * Empty_zero_page is a special page that is used for zero-initialized data
  50  * and COW.
  51  */
  52 unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss;
  53 EXPORT_SYMBOL(empty_zero_page);
  54
  55 pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
  56                               unsigned long size, pgprot_t vma_prot)
  57 {
  58         if (!pfn_valid(pfn))
  59                 return pgprot_noncached(vma_prot);
  60         else if (file->f_flags & O_SYNC)
  61                 return pgprot_writecombine(vma_prot);
  62         return vma_prot;
  63 }
  64 EXPORT_SYMBOL(phys_mem_access_prot);
  65
  66 static void __init *early_pgtable_alloc(void)
  67 {
  68         phys_addr_t phys;
  69         void *ptr;
  70
  71         phys = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
  72         BUG_ON(!phys);
  73         ptr = __va(phys);
  74         memset(ptr, 0, PAGE_SIZE);
  75
  76         /* Ensure the zeroed page is visible to the page table walker */
  77         dsb(ishst);
  78         return ptr;
  79 }
  80
  81 /*
  82  * remap a PMD into pages
  83  */
  84 static void split_pmd(pmd_t *pmd, pte_t *pte)
  85 {
  86         unsigned long pfn = pmd_pfn(*pmd);
  87         int i = 0;
  88
  89         do {
  90                 /*
  91                  * Need to have the least restrictive permissions available
  92                  * permissions will be fixed up later
  93                  */
  94                 set_pte(pte, pfn_pte(pfn, PAGE_KERNEL_EXEC));
  95                 pfn++;
  96         } while (pte++, i++, i < PTRS_PER_PTE);
  97 }
  98
  99 static void alloc_init_pte(pmd_t *pmd, unsigned long addr,
 100                                   unsigned long end, unsigned long pfn,
 101                                   pgprot_t prot,
 102                                   void *(*pgtable_alloc)(void))
 103 {
 104         pte_t *pte;
 105
 106         if (pmd_none(*pmd) || pmd_sect(*pmd)) {
 107                 pte = pgtable_alloc();
 108                 if (pmd_sect(*pmd))
 109                         split_pmd(pmd, pte);
 110                 __pmd_populate(pmd, __pa(pte), PMD_TYPE_TABLE);
 111                 flush_tlb_all();
 112         }
 113         BUG_ON(pmd_bad(*pmd));
 114
 115         pte = pte_offset_kernel(pmd, addr);
 116         do {
 117                 set_pte(pte, pfn_pte(pfn, prot));
 118                 pfn++;
 119         } while (pte++, addr += PAGE_SIZE, addr != end);
 120 }
 121
 122 static void split_pud(pud_t *old_pud, pmd_t *pmd)
 123 {
 124         unsigned long addr = pud_pfn(*old_pud) << PAGE_SHIFT;
 125         pgprot_t prot = __pgprot(pud_val(*old_pud) ^ addr);
 126         int i = 0;
 127
 128         do {
 129                 set_pmd(pmd, __pmd(addr | pgprot_val(prot)));
 130                 addr += PMD_SIZE;
 131         } while (pmd++, i++, i < PTRS_PER_PMD);
 132 }
 133
 134 static void alloc_init_pmd(struct mm_struct *mm, pud_t *pud,
 135                                   unsigned long addr, unsigned long end,
 136                                   phys_addr_t phys, pgprot_t prot,
 137                                   void *(*pgtable_alloc)(void))
 138 {
 139         pmd_t *pmd;
 140         unsigned long next;
 141
 142         /*
 143          * Check for initial section mappings in the pgd/pud and remove them.
 144          */
 145         if (pud_none(*pud) || pud_sect(*pud)) {
 146                 pmd = pgtable_alloc();
 147                 if (pud_sect(*pud)) {
 148                         /*
 149                          * need to have the 1G of mappings continue to be
 150                          * present
 151                          */
 152                         split_pud(pud, pmd);
 153                 }
 154                 pud_populate(mm, pud, pmd);
 155                 flush_tlb_all();
 156         }
 157         BUG_ON(pud_bad(*pud));
 158
 159         pmd = pmd_offset(pud, addr);
 160         do {
 161                 next = pmd_addr_end(addr, end);
 162                 /* try section mapping first */
 163                 if (((addr | next | phys) & ~SECTION_MASK) == 0) {
 164                         pmd_t old_pmd =*pmd;
 165                         set_pmd(pmd, __pmd(phys |
 166                                            pgprot_val(mk_sect_prot(prot))));
 167                         /*
 168                          * Check for previous table entries created during
 169                          * boot (__create_page_tables) and flush them.
 170                          */
 171                         if (!pmd_none(old_pmd)) {
 172                                 flush_tlb_all();
 173                                 if (pmd_table(old_pmd)) {
 174                                         phys_addr_t table = __pa(pte_offset_map(&old_pmd, 0));
 175                                         if (!WARN_ON_ONCE(slab_is_available()))
 176                                                 memblock_free(table, PAGE_SIZE);
 177                                 }
 178                         }
 179                 } else {
 180                         alloc_init_pte(pmd, addr, next, __phys_to_pfn(phys),
 181                                        prot, pgtable_alloc);
 182                 }
 183                 phys += next - addr;
 184         } while (pmd++, addr = next, addr != end);
 185 }
 186
 187 static inline bool use_1G_block(unsigned long addr, unsigned long next,
 188                         unsigned long phys)
 189 {
 190         if (PAGE_SHIFT != 12)
 191                 return false;
 192
 193         if (((addr | next | phys) & ~PUD_MASK) != 0)
 194                 return false;
 195
 196         return true;
 197 }
 198
 199 static void alloc_init_pud(struct mm_struct *mm, pgd_t *pgd,
 200                                   unsigned long addr, unsigned long end,
 201                                   phys_addr_t phys, pgprot_t prot,
 202                                   void *(*pgtable_alloc)(void))
 203 {
 204         pud_t *pud;
 205         unsigned long next;
 206
 207         if (pgd_none(*pgd)) {
 208                 pud = pgtable_alloc();
 209                 pgd_populate(mm, pgd, pud);
 210         }
 211         BUG_ON(pgd_bad(*pgd));
 212
 213         pud = pud_offset(pgd, addr);
 214         do {
 215                 next = pud_addr_end(addr, end);
 216
 217                 /*
 218                  * For 4K granule only, attempt to put down a 1GB block
 219                  */
 220                 if (use_1G_block(addr, next, phys)) {
 221                         pud_t old_pud = *pud;
 222                         set_pud(pud, __pud(phys |
 223                                            pgprot_val(mk_sect_prot(prot))));
 224
 225                         /*
 226                          * If we have an old value for a pud, it will
 227                          * be pointing to a pmd table that we no longer
 228                          * need (from swapper_pg_dir).
 229                          *
 230                          * Look up the old pmd table and free it.
 231                          */
 232                         if (!pud_none(old_pud)) {
 233                                 flush_tlb_all();
 234                                 if (pud_table(old_pud)) {
 235                                         phys_addr_t table = __pa(pmd_offset(&old_pud, 0));
 236                                         if (!WARN_ON_ONCE(slab_is_available()))
 237                                                 memblock_free(table, PAGE_SIZE);
 238                                 }
 239                         }
 240                 } else {
 241                         alloc_init_pmd(mm, pud, addr, next, phys, prot,
 242                                        pgtable_alloc);
 243                 }
 244                 phys += next - addr;
 245         } while (pud++, addr = next, addr != end);
 246 }
 247
 248 /*
 249  * Create the page directory entries and any necessary page tables for the
 250  * mapping specified by 'md'.
 251  */
 252 static void  __create_mapping(struct mm_struct *mm, pgd_t *pgd,
 253                                     phys_addr_t phys, unsigned long virt,
 254                                     phys_addr_t size, pgprot_t prot,
 255                                     void *(*pgtable_alloc)(void))
 256 {
 257         unsigned long addr, length, end, next;
 258
 259         addr = virt & PAGE_MASK;
 260         length = PAGE_ALIGN(size + (virt & ~PAGE_MASK));
 261
 262         end = addr + length;
 263         do {
 264                 next = pgd_addr_end(addr, end);
 265                 alloc_init_pud(mm, pgd, addr, next, phys, prot, pgtable_alloc);
 266                 phys += next - addr;
 267         } while (pgd++, addr = next, addr != end);
 268 }
 269
 270 static void *late_pgtable_alloc(void)
 271 {
 272         void *ptr = (void *)__get_free_page(PGALLOC_GFP);
 273         BUG_ON(!ptr);
 274
 275         /* Ensure the zeroed page is visible to the page table walker */
 276         dsb(ishst);
 277         return ptr;
 278 }
 279
 280 static void __init create_mapping(phys_addr_t phys, unsigned long virt,
 281                                   phys_addr_t size, pgprot_t prot)
 282 {
 283         if (virt < VMALLOC_START) {
 284                 pr_warn("BUG: not creating mapping for %pa at 0x%016lx - outside kernel range\n",
 285                         &phys, virt);
 286                 return;
 287         }
 288         __create_mapping(&init_mm, pgd_offset_k(virt), phys, virt,
 289                          size, prot, early_pgtable_alloc);
 290 }
 291
 292 void __init create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
 293                                unsigned long virt, phys_addr_t size,
 294                                pgprot_t prot)
 295 {
 296         __create_mapping(mm, pgd_offset(mm, virt), phys, virt, size, prot,
 297                                 late_pgtable_alloc);
 298 }
 299
 300 static void create_mapping_late(phys_addr_t phys, unsigned long virt,
 301                                   phys_addr_t size, pgprot_t prot)
 302 {
 303         if (virt < VMALLOC_START) {
 304                 pr_warn("BUG: not creating mapping for %pa at 0x%016lx - outside kernel range\n",
 305                         &phys, virt);
 306                 return;
 307         }
 308
 309         return __create_mapping(&init_mm, pgd_offset_k(virt),
 310                                 phys, virt, size, prot, late_pgtable_alloc);
 311 }
 312
 313 #ifdef CONFIG_DEBUG_RODATA
 314 static void __init __map_memblock(phys_addr_t start, phys_addr_t end)
 315 {
 316         /*
 317          * Set up the executable regions using the existing section mappings
 318          * for now. This will get more fine grained later once all memory
 319          * is mapped
 320          */
 321         unsigned long kernel_x_start = round_down(__pa(_stext), SWAPPER_BLOCK_SIZE);
 322         unsigned long kernel_x_end = round_up(__pa(__init_end), SWAPPER_BLOCK_SIZE);
 323
 324         if (end < kernel_x_start) {
 325                 create_mapping(start, __phys_to_virt(start),
 326                         end - start, PAGE_KERNEL);
 327         } else if (start >= kernel_x_end) {
 328                 create_mapping(start, __phys_to_virt(start),
 329                         end - start, PAGE_KERNEL);
 330         } else {
 331                 if (start < kernel_x_start)
 332                         create_mapping(start, __phys_to_virt(start),
 333                                 kernel_x_start - start,
 334                                 PAGE_KERNEL);
 335                 create_mapping(kernel_x_start,
 336                                 __phys_to_virt(kernel_x_start),
 337                                 kernel_x_end - kernel_x_start,
 338                                 PAGE_KERNEL_EXEC);
 339                 if (kernel_x_end < end)
 340                         create_mapping(kernel_x_end,
 341                                 __phys_to_virt(kernel_x_end),
 342                                 end - kernel_x_end,
 343                                 PAGE_KERNEL);
 344         }
 345
 346 }
 347 #else
 348 static void __init __map_memblock(phys_addr_t start, phys_addr_t end)
 349 {
 350         create_mapping(start, __phys_to_virt(start), end - start,
 351                         PAGE_KERNEL_EXEC);
 352 }
 353 #endif
 354
 355 static void __init map_mem(void)
 356 {
 357         struct memblock_region *reg;
 358         phys_addr_t limit;
 359
 360         /*
 361          * Temporarily limit the memblock range. We need to do this as
 362          * create_mapping requires puds, pmds and ptes to be allocated from
 363          * memory addressable from the initial direct kernel mapping.
 364          *
 365          * The initial direct kernel mapping, located at swapper_pg_dir, gives
 366          * us PUD_SIZE (with SECTION maps) or PMD_SIZE (without SECTION maps,
 367          * memory starting from PHYS_OFFSET (which must be aligned to 2MB as
 368          * per Documentation/arm64/booting.txt).
 369          */
 370         limit = PHYS_OFFSET + SWAPPER_INIT_MAP_SIZE;
 371         memblock_set_current_limit(limit);
 372
 373         /* map all the memory banks */
 374         for_each_memblock(memory, reg) {
 375                 phys_addr_t start = reg->base;
 376                 phys_addr_t end = start + reg->size;
 377
 378                 if (start >= end)
 379                         break;
 380
 381                 if (ARM64_SWAPPER_USES_SECTION_MAPS) {
 382                         /*
 383                          * For the first memory bank align the start address and
 384                          * current memblock limit to prevent create_mapping() from
 385                          * allocating pte page tables from unmapped memory. With
 386                          * the section maps, if the first block doesn't end on section
 387                          * size boundary, create_mapping() will try to allocate a pte
 388                          * page, which may be returned from an unmapped area.
 389                          * When section maps are not used, the pte page table for the
 390                          * current limit is already present in swapper_pg_dir.
 391                          */
 392                         if (start < limit)
 393                                 start = ALIGN(start, SECTION_SIZE);
 394                         if (end < limit) {
 395                                 limit = end & SECTION_MASK;
 396                                 memblock_set_current_limit(limit);
 397                         }
 398                 }
 399                 __map_memblock(start, end);
 400         }
 401
 402         /* Limit no longer required. */
 403         memblock_set_current_limit(MEMBLOCK_ALLOC_ANYWHERE);
 404 }
 405
 406 static void __init fixup_executable(void)
 407 {
 408 #ifdef CONFIG_DEBUG_RODATA
 409         /* now that we are actually fully mapped, make the start/end more fine grained */
 410         if (!IS_ALIGNED((unsigned long)_stext, SWAPPER_BLOCK_SIZE)) {
 411                 unsigned long aligned_start = round_down(__pa(_stext),
 412                                                          SWAPPER_BLOCK_SIZE);
 413
 414                 create_mapping(aligned_start, __phys_to_virt(aligned_start),
 415                                 __pa(_stext) - aligned_start,
 416                                 PAGE_KERNEL);
 417         }
 418
 419         if (!IS_ALIGNED((unsigned long)__init_end, SWAPPER_BLOCK_SIZE)) {
 420                 unsigned long aligned_end = round_up(__pa(__init_end),
 421                                                           SWAPPER_BLOCK_SIZE);
 422                 create_mapping(__pa(__init_end), (unsigned long)__init_end,
 423                                 aligned_end - __pa(__init_end),
 424                                 PAGE_KERNEL);
 425         }
 426 #endif
 427 }
 428
 429 #ifdef CONFIG_DEBUG_RODATA
 430 void mark_rodata_ro(void)
 431 {
 432         create_mapping_late(__pa(_stext), (unsigned long)_stext,
 433                                 (unsigned long)_etext - (unsigned long)_stext,
 434                                 PAGE_KERNEL_ROX);
 435
 436 }
 437 #endif
 438
 439 void fixup_init(void)
 440 {
 441         create_mapping_late(__pa(__init_begin), (unsigned long)__init_begin,
 442                         (unsigned long)__init_end - (unsigned long)__init_begin,
 443                         PAGE_KERNEL);
 444 }
 445
 446 /*
 447  * paging_init() sets up the page tables, initialises the zone memory
 448  * maps and sets up the zero page.
 449  */
 450 void __init paging_init(void)
 451 {
 452         map_mem();
 453         fixup_executable();
 454
 455         bootmem_init();
 456
 457         /*
 458          * TTBR0 is only used for the identity mapping at this stage. Make it
 459          * point to zero page to avoid speculatively fetching new entries.
 460          */
 461         cpu_set_reserved_ttbr0();
 462         local_flush_tlb_all();
 463         cpu_set_default_tcr_t0sz();
 464 }
 465
 466 /*
 467  * Check whether a kernel address is valid (derived from arch/x86/).
 468  */
 469 int kern_addr_valid(unsigned long addr)
 470 {
 471         pgd_t *pgd;
 472         pud_t *pud;
 473         pmd_t *pmd;
 474         pte_t *pte;
 475
 476         if ((((long)addr) >> VA_BITS) != -1UL)
 477                 return 0;
 478
 479         pgd = pgd_offset_k(addr);
 480         if (pgd_none(*pgd))
 481                 return 0;
 482
 483         pud = pud_offset(pgd, addr);
 484         if (pud_none(*pud))
 485                 return 0;
 486
 487         if (pud_sect(*pud))
 488                 return pfn_valid(pud_pfn(*pud));
 489
 490         pmd = pmd_offset(pud, addr);
 491         if (pmd_none(*pmd))
 492                 return 0;
 493
 494         if (pmd_sect(*pmd))
 495                 return pfn_valid(pmd_pfn(*pmd));
 496
 497         pte = pte_offset_kernel(pmd, addr);
 498         if (pte_none(*pte))
 499                 return 0;
 500
 501         return pfn_valid(pte_pfn(*pte));
 502 }
 503 #ifdef CONFIG_SPARSEMEM_VMEMMAP
 504 #if !ARM64_SWAPPER_USES_SECTION_MAPS
 505 int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
 506 {
 507         return vmemmap_populate_basepages(start, end, node);
 508 }
 509 #else   /* !ARM64_SWAPPER_USES_SECTION_MAPS */
 510 int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
 511 {
 512         unsigned long addr = start;
 513         unsigned long next;
 514         pgd_t *pgd;
 515         pud_t *pud;
 516         pmd_t *pmd;
 517
 518         do {
 519                 next = pmd_addr_end(addr, end);
 520
 521                 pgd = vmemmap_pgd_populate(addr, node);
 522                 if (!pgd)
 523                         return -ENOMEM;
 524
 525                 pud = vmemmap_pud_populate(pgd, addr, node);
 526                 if (!pud)
 527                         return -ENOMEM;
 528
 529                 pmd = pmd_offset(pud, addr);
 530                 if (pmd_none(*pmd)) {
 531                         void *p = NULL;
 532
 533                         p = vmemmap_alloc_block_buf(PMD_SIZE, node);
 534                         if (!p)
 535                                 return -ENOMEM;
 536
 537                         set_pmd(pmd, __pmd(__pa(p) | PROT_SECT_NORMAL));
 538                 } else
 539                         vmemmap_verify((pte_t *)pmd, node, addr, next);
 540         } while (addr = next, addr != end);
 541
 542         return 0;
 543 }
 544 #endif  /* CONFIG_ARM64_64K_PAGES */
 545 void vmemmap_free(unsigned long start, unsigned long end)
 546 {
 547 }
 548 #endif  /* CONFIG_SPARSEMEM_VMEMMAP */
 549
 550 static pte_t bm_pte[PTRS_PER_PTE] __page_aligned_bss;
 551 #if CONFIG_PGTABLE_LEVELS > 2
 552 static pmd_t bm_pmd[PTRS_PER_PMD] __page_aligned_bss;
 553 #endif
 554 #if CONFIG_PGTABLE_LEVELS > 3
 555 static pud_t bm_pud[PTRS_PER_PUD] __page_aligned_bss;
 556 #endif
 557
 558 static inline pud_t * fixmap_pud(unsigned long addr)
 559 {
 560         pgd_t *pgd = pgd_offset_k(addr);
 561
 562         BUG_ON(pgd_none(*pgd) || pgd_bad(*pgd));
 563
 564         return pud_offset(pgd, addr);
 565 }
 566
 567 static inline pmd_t * fixmap_pmd(unsigned long addr)
 568 {
 569         pud_t *pud = fixmap_pud(addr);
 570
 571         BUG_ON(pud_none(*pud) || pud_bad(*pud));
 572
 573         return pmd_offset(pud, addr);
 574 }
 575
 576 static inline pte_t * fixmap_pte(unsigned long addr)
 577 {
 578         pmd_t *pmd = fixmap_pmd(addr);
 579
 580         BUG_ON(pmd_none(*pmd) || pmd_bad(*pmd));
 581
 582         return pte_offset_kernel(pmd, addr);
 583 }
 584
 585 void __init early_fixmap_init(void)
 586 {
 587         pgd_t *pgd;
 588         pud_t *pud;
 589         pmd_t *pmd;
 590         unsigned long addr = FIXADDR_START;
 591
 592         pgd = pgd_offset_k(addr);
 593         pgd_populate(&init_mm, pgd, bm_pud);
 594         pud = pud_offset(pgd, addr);
 595         pud_populate(&init_mm, pud, bm_pmd);
 596         pmd = pmd_offset(pud, addr);
 597         pmd_populate_kernel(&init_mm, pmd, bm_pte);
 598
 599         /*
 600          * The boot-ioremap range spans multiple pmds, for which
 601          * we are not preparted:
 602          */
 603         BUILD_BUG_ON((__fix_to_virt(FIX_BTMAP_BEGIN) >> PMD_SHIFT)
 604                      != (__fix_to_virt(FIX_BTMAP_END) >> PMD_SHIFT));
 605
 606         if ((pmd != fixmap_pmd(fix_to_virt(FIX_BTMAP_BEGIN)))
 607              || pmd != fixmap_pmd(fix_to_virt(FIX_BTMAP_END))) {
 608                 WARN_ON(1);
 609                 pr_warn("pmd %p != %p, %p\n",
 610                         pmd, fixmap_pmd(fix_to_virt(FIX_BTMAP_BEGIN)),
 611                         fixmap_pmd(fix_to_virt(FIX_BTMAP_END)));
 612                 pr_warn("fix_to_virt(FIX_BTMAP_BEGIN): %08lx\n",
 613                         fix_to_virt(FIX_BTMAP_BEGIN));
 614                 pr_warn("fix_to_virt(FIX_BTMAP_END):   %08lx\n",
 615                         fix_to_virt(FIX_BTMAP_END));
 616
 617                 pr_warn("FIX_BTMAP_END:       %d\n", FIX_BTMAP_END);
 618                 pr_warn("FIX_BTMAP_BEGIN:     %d\n", FIX_BTMAP_BEGIN);
 619         }
 620 }
 621
 622 void __set_fixmap(enum fixed_addresses idx,
 623                                phys_addr_t phys, pgprot_t flags)
 624 {
 625         unsigned long addr = __fix_to_virt(idx);
 626         pte_t *pte;
 627
 628         BUG_ON(idx <= FIX_HOLE || idx >= __end_of_fixed_addresses);
 629
 630         pte = fixmap_pte(addr);
 631
 632         if (pgprot_val(flags)) {
 633                 set_pte(pte, pfn_pte(phys >> PAGE_SHIFT, flags));
 634         } else {
 635                 pte_clear(&init_mm, addr, pte);
 636                 flush_tlb_kernel_range(addr, addr+PAGE_SIZE);
 637         }
 638 }
 639
 640 void *__init fixmap_remap_fdt(phys_addr_t dt_phys)
 641 {
 642         const u64 dt_virt_base = __fix_to_virt(FIX_FDT);
 643         pgprot_t prot = PAGE_KERNEL_RO;
 644         int size, offset;
 645         void *dt_virt;
 646
 647         /*
 648          * Check whether the physical FDT address is set and meets the minimum
 649          * alignment requirement. Since we are relying on MIN_FDT_ALIGN to be
 650          * at least 8 bytes so that we can always access the magic and size
 651          * fields of the FDT header after mapping the first chunk, double check
 652          * here if that is indeed the case.
 653          */
 654         BUILD_BUG_ON(MIN_FDT_ALIGN < 8);
 655         if (!dt_phys || dt_phys % MIN_FDT_ALIGN)
 656                 return NULL;
 657
 658         /*
 659          * Make sure that the FDT region can be mapped without the need to
 660          * allocate additional translation table pages, so that it is safe
 661          * to call create_mapping() this early.
 662          *
 663          * On 64k pages, the FDT will be mapped using PTEs, so we need to
 664          * be in the same PMD as the rest of the fixmap.
 665          * On 4k pages, we'll use section mappings for the FDT so we only
 666          * have to be in the same PUD.
 667          */
 668         BUILD_BUG_ON(dt_virt_base % SZ_2M);
 669
 670         BUILD_BUG_ON(__fix_to_virt(FIX_FDT_END) >> SWAPPER_TABLE_SHIFT !=
 671                      __fix_to_virt(FIX_BTMAP_BEGIN) >> SWAPPER_TABLE_SHIFT);
 672
 673         offset = dt_phys % SWAPPER_BLOCK_SIZE;
 674         dt_virt = (void *)dt_virt_base + offset;
 675
 676         /* map the first chunk so we can read the size from the header */
 677         create_mapping(round_down(dt_phys, SWAPPER_BLOCK_SIZE), dt_virt_base,
 678                        SWAPPER_BLOCK_SIZE, prot);
 679
 680         if (fdt_magic(dt_virt) != FDT_MAGIC)
 681                 return NULL;
 682
 683         size = fdt_totalsize(dt_virt);
 684         if (size > MAX_FDT_SIZE)
 685                 return NULL;
 686
 687         if (offset + size > SWAPPER_BLOCK_SIZE)
 688                 create_mapping(round_down(dt_phys, SWAPPER_BLOCK_SIZE), dt_virt_base,
 689                                round_up(offset + size, SWAPPER_BLOCK_SIZE), prot);
 690
 691         memblock_reserve(dt_phys, size);
 692
 693         return dt_virt;
 694 }