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         /*
 260          * If the virtual and physical address don't have the same offset
 261          * within a page, we cannot map the region as the caller expects.
 262          */
 263         if (WARN_ON((phys ^ virt) & ~PAGE_MASK))
 264                 return;
 265
 266         phys &= PAGE_MASK;
 267         addr = virt & PAGE_MASK;
 268         length = PAGE_ALIGN(size + (virt & ~PAGE_MASK));
 269
 270         end = addr + length;
 271         do {
 272                 next = pgd_addr_end(addr, end);
 273                 alloc_init_pud(mm, pgd, addr, next, phys, prot, pgtable_alloc);
 274                 phys += next - addr;
 275         } while (pgd++, addr = next, addr != end);
 276 }
 277
 278 static void *late_pgtable_alloc(void)
 279 {
 280         void *ptr = (void *)__get_free_page(PGALLOC_GFP);
 281         BUG_ON(!ptr);
 282
 283         /* Ensure the zeroed page is visible to the page table walker */
 284         dsb(ishst);
 285         return ptr;
 286 }
 287
 288 static void __init create_mapping(phys_addr_t phys, unsigned long virt,
 289                                   phys_addr_t size, pgprot_t prot)
 290 {
 291         if (virt < VMALLOC_START) {
 292                 pr_warn("BUG: not creating mapping for %pa at 0x%016lx - outside kernel range\n",
 293                         &phys, virt);
 294                 return;
 295         }
 296         __create_mapping(&init_mm, pgd_offset_k(virt), phys, virt,
 297                          size, prot, early_pgtable_alloc);
 298 }
 299
 300 void __init create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
 301                                unsigned long virt, phys_addr_t size,
 302                                pgprot_t prot)
 303 {
 304         __create_mapping(mm, pgd_offset(mm, virt), phys, virt, size, prot,
 305                                 late_pgtable_alloc);
 306 }
 307
 308 static void create_mapping_late(phys_addr_t phys, unsigned long virt,
 309                                   phys_addr_t size, pgprot_t prot)
 310 {
 311         if (virt < VMALLOC_START) {
 312                 pr_warn("BUG: not creating mapping for %pa at 0x%016lx - outside kernel range\n",
 313                         &phys, virt);
 314                 return;
 315         }
 316
 317         return __create_mapping(&init_mm, pgd_offset_k(virt),
 318                                 phys, virt, size, prot, late_pgtable_alloc);
 319 }
 320
 321 #ifdef CONFIG_DEBUG_RODATA
 322 static void __init __map_memblock(phys_addr_t start, phys_addr_t end)
 323 {
 324         /*
 325          * Set up the executable regions using the existing section mappings
 326          * for now. This will get more fine grained later once all memory
 327          * is mapped
 328          */
 329         unsigned long kernel_x_start = round_down(__pa(_stext), SWAPPER_BLOCK_SIZE);
 330         unsigned long kernel_x_end = round_up(__pa(__init_end), SWAPPER_BLOCK_SIZE);
 331
 332         if (end < kernel_x_start) {
 333                 create_mapping(start, __phys_to_virt(start),
 334                         end - start, PAGE_KERNEL);
 335         } else if (start >= kernel_x_end) {
 336                 create_mapping(start, __phys_to_virt(start),
 337                         end - start, PAGE_KERNEL);
 338         } else {
 339                 if (start < kernel_x_start)
 340                         create_mapping(start, __phys_to_virt(start),
 341                                 kernel_x_start - start,
 342                                 PAGE_KERNEL);
 343                 create_mapping(kernel_x_start,
 344                                 __phys_to_virt(kernel_x_start),
 345                                 kernel_x_end - kernel_x_start,
 346                                 PAGE_KERNEL_EXEC);
 347                 if (kernel_x_end < end)
 348                         create_mapping(kernel_x_end,
 349                                 __phys_to_virt(kernel_x_end),
 350                                 end - kernel_x_end,
 351                                 PAGE_KERNEL);
 352         }
 353
 354 }
 355 #else
 356 static void __init __map_memblock(phys_addr_t start, phys_addr_t end)
 357 {
 358         create_mapping(start, __phys_to_virt(start), end - start,
 359                         PAGE_KERNEL_EXEC);
 360 }
 361 #endif
 362
 363 static void __init map_mem(void)
 364 {
 365         struct memblock_region *reg;
 366         phys_addr_t limit;
 367
 368         /*
 369          * Temporarily limit the memblock range. We need to do this as
 370          * create_mapping requires puds, pmds and ptes to be allocated from
 371          * memory addressable from the initial direct kernel mapping.
 372          *
 373          * The initial direct kernel mapping, located at swapper_pg_dir, gives
 374          * us PUD_SIZE (with SECTION maps) or PMD_SIZE (without SECTION maps,
 375          * memory starting from PHYS_OFFSET (which must be aligned to 2MB as
 376          * per Documentation/arm64/booting.txt).
 377          */
 378         limit = PHYS_OFFSET + SWAPPER_INIT_MAP_SIZE;
 379         memblock_set_current_limit(limit);
 380
 381         /* map all the memory banks */
 382         for_each_memblock(memory, reg) {
 383                 phys_addr_t start = reg->base;
 384                 phys_addr_t end = start + reg->size;
 385
 386                 if (start >= end)
 387                         break;
 388                 if (memblock_is_nomap(reg))
 389                         continue;
 390
 391                 if (ARM64_SWAPPER_USES_SECTION_MAPS) {
 392                         /*
 393                          * For the first memory bank align the start address and
 394                          * current memblock limit to prevent create_mapping() from
 395                          * allocating pte page tables from unmapped memory. With
 396                          * the section maps, if the first block doesn't end on section
 397                          * size boundary, create_mapping() will try to allocate a pte
 398                          * page, which may be returned from an unmapped area.
 399                          * When section maps are not used, the pte page table for the
 400                          * current limit is already present in swapper_pg_dir.
 401                          */
 402                         if (start < limit)
 403                                 start = ALIGN(start, SECTION_SIZE);
 404                         if (end < limit) {
 405                                 limit = end & SECTION_MASK;
 406                                 memblock_set_current_limit(limit);
 407                         }
 408                 }
 409                 __map_memblock(start, end);
 410         }
 411
 412         /* Limit no longer required. */
 413         memblock_set_current_limit(MEMBLOCK_ALLOC_ANYWHERE);
 414 }
 415
 416 static void __init fixup_executable(void)
 417 {
 418 #ifdef CONFIG_DEBUG_RODATA
 419         /* now that we are actually fully mapped, make the start/end more fine grained */
 420         if (!IS_ALIGNED((unsigned long)_stext, SWAPPER_BLOCK_SIZE)) {
 421                 unsigned long aligned_start = round_down(__pa(_stext),
 422                                                          SWAPPER_BLOCK_SIZE);
 423
 424                 create_mapping(aligned_start, __phys_to_virt(aligned_start),
 425                                 __pa(_stext) - aligned_start,
 426                                 PAGE_KERNEL);
 427         }
 428
 429         if (!IS_ALIGNED((unsigned long)__init_end, SWAPPER_BLOCK_SIZE)) {
 430                 unsigned long aligned_end = round_up(__pa(__init_end),
 431                                                           SWAPPER_BLOCK_SIZE);
 432                 create_mapping(__pa(__init_end), (unsigned long)__init_end,
 433                                 aligned_end - __pa(__init_end),
 434                                 PAGE_KERNEL);
 435         }
 436 #endif
 437 }
 438
 439 #ifdef CONFIG_DEBUG_RODATA
 440 void mark_rodata_ro(void)
 441 {
 442         create_mapping_late(__pa(_stext), (unsigned long)_stext,
 443                                 (unsigned long)_etext - (unsigned long)_stext,
 444                                 PAGE_KERNEL_ROX);
 445
 446 }
 447 #endif
 448
 449 void fixup_init(void)
 450 {
 451         create_mapping_late(__pa(__init_begin), (unsigned long)__init_begin,
 452                         (unsigned long)__init_end - (unsigned long)__init_begin,
 453                         PAGE_KERNEL);
 454 }
 455
 456 /*
 457  * paging_init() sets up the page tables, initialises the zone memory
 458  * maps and sets up the zero page.
 459  */
 460 void __init paging_init(void)
 461 {
 462         map_mem();
 463         fixup_executable();
 464
 465         bootmem_init();
 466
 467         /*
 468          * TTBR0 is only used for the identity mapping at this stage. Make it
 469          * point to zero page to avoid speculatively fetching new entries.
 470          */
 471         cpu_set_reserved_ttbr0();
 472         local_flush_tlb_all();
 473         cpu_set_default_tcr_t0sz();
 474 }
 475
 476 /*
 477  * Check whether a kernel address is valid (derived from arch/x86/).
 478  */
 479 int kern_addr_valid(unsigned long addr)
 480 {
 481         pgd_t *pgd;
 482         pud_t *pud;
 483         pmd_t *pmd;
 484         pte_t *pte;
 485
 486         if ((((long)addr) >> VA_BITS) != -1UL)
 487                 return 0;
 488
 489         pgd = pgd_offset_k(addr);
 490         if (pgd_none(*pgd))
 491                 return 0;
 492
 493         pud = pud_offset(pgd, addr);
 494         if (pud_none(*pud))
 495                 return 0;
 496
 497         if (pud_sect(*pud))
 498                 return pfn_valid(pud_pfn(*pud));
 499
 500         pmd = pmd_offset(pud, addr);
 501         if (pmd_none(*pmd))
 502                 return 0;
 503
 504         if (pmd_sect(*pmd))
 505                 return pfn_valid(pmd_pfn(*pmd));
 506
 507         pte = pte_offset_kernel(pmd, addr);
 508         if (pte_none(*pte))
 509                 return 0;
 510
 511         return pfn_valid(pte_pfn(*pte));
 512 }
 513 #ifdef CONFIG_SPARSEMEM_VMEMMAP
 514 #if !ARM64_SWAPPER_USES_SECTION_MAPS
 515 int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
 516 {
 517         return vmemmap_populate_basepages(start, end, node);
 518 }
 519 #else   /* !ARM64_SWAPPER_USES_SECTION_MAPS */
 520 int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
 521 {
 522         unsigned long addr = start;
 523         unsigned long next;
 524         pgd_t *pgd;
 525         pud_t *pud;
 526         pmd_t *pmd;
 527
 528         do {
 529                 next = pmd_addr_end(addr, end);
 530
 531                 pgd = vmemmap_pgd_populate(addr, node);
 532                 if (!pgd)
 533                         return -ENOMEM;
 534
 535                 pud = vmemmap_pud_populate(pgd, addr, node);
 536                 if (!pud)
 537                         return -ENOMEM;
 538
 539                 pmd = pmd_offset(pud, addr);
 540                 if (pmd_none(*pmd)) {
 541                         void *p = NULL;
 542
 543                         p = vmemmap_alloc_block_buf(PMD_SIZE, node);
 544                         if (!p)
 545                                 return -ENOMEM;
 546
 547                         set_pmd(pmd, __pmd(__pa(p) | PROT_SECT_NORMAL));
 548                 } else
 549                         vmemmap_verify((pte_t *)pmd, node, addr, next);
 550         } while (addr = next, addr != end);
 551
 552         return 0;
 553 }
 554 #endif  /* CONFIG_ARM64_64K_PAGES */
 555 void vmemmap_free(unsigned long start, unsigned long end)
 556 {
 557 }
 558 #endif  /* CONFIG_SPARSEMEM_VMEMMAP */
 559
 560 static pte_t bm_pte[PTRS_PER_PTE] __page_aligned_bss;
 561 #if CONFIG_PGTABLE_LEVELS > 2
 562 static pmd_t bm_pmd[PTRS_PER_PMD] __page_aligned_bss;
 563 #endif
 564 #if CONFIG_PGTABLE_LEVELS > 3
 565 static pud_t bm_pud[PTRS_PER_PUD] __page_aligned_bss;
 566 #endif
 567
 568 static inline pud_t * fixmap_pud(unsigned long addr)
 569 {
 570         pgd_t *pgd = pgd_offset_k(addr);
 571
 572         BUG_ON(pgd_none(*pgd) || pgd_bad(*pgd));
 573
 574         return pud_offset(pgd, addr);
 575 }
 576
 577 static inline pmd_t * fixmap_pmd(unsigned long addr)
 578 {
 579         pud_t *pud = fixmap_pud(addr);
 580
 581         BUG_ON(pud_none(*pud) || pud_bad(*pud));
 582
 583         return pmd_offset(pud, addr);
 584 }
 585
 586 static inline pte_t * fixmap_pte(unsigned long addr)
 587 {
 588         pmd_t *pmd = fixmap_pmd(addr);
 589
 590         BUG_ON(pmd_none(*pmd) || pmd_bad(*pmd));
 591
 592         return pte_offset_kernel(pmd, addr);
 593 }
 594
 595 void __init early_fixmap_init(void)
 596 {
 597         pgd_t *pgd;
 598         pud_t *pud;
 599         pmd_t *pmd;
 600         unsigned long addr = FIXADDR_START;
 601
 602         pgd = pgd_offset_k(addr);
 603         pgd_populate(&init_mm, pgd, bm_pud);
 604         pud = pud_offset(pgd, addr);
 605         pud_populate(&init_mm, pud, bm_pmd);
 606         pmd = pmd_offset(pud, addr);
 607         pmd_populate_kernel(&init_mm, pmd, bm_pte);
 608
 609         /*
 610          * The boot-ioremap range spans multiple pmds, for which
 611          * we are not preparted:
 612          */
 613         BUILD_BUG_ON((__fix_to_virt(FIX_BTMAP_BEGIN) >> PMD_SHIFT)
 614                      != (__fix_to_virt(FIX_BTMAP_END) >> PMD_SHIFT));
 615
 616         if ((pmd != fixmap_pmd(fix_to_virt(FIX_BTMAP_BEGIN)))
 617              || pmd != fixmap_pmd(fix_to_virt(FIX_BTMAP_END))) {
 618                 WARN_ON(1);
 619                 pr_warn("pmd %p != %p, %p\n",
 620                         pmd, fixmap_pmd(fix_to_virt(FIX_BTMAP_BEGIN)),
 621                         fixmap_pmd(fix_to_virt(FIX_BTMAP_END)));
 622                 pr_warn("fix_to_virt(FIX_BTMAP_BEGIN): %08lx\n",
 623                         fix_to_virt(FIX_BTMAP_BEGIN));
 624                 pr_warn("fix_to_virt(FIX_BTMAP_END):   %08lx\n",
 625                         fix_to_virt(FIX_BTMAP_END));
 626
 627                 pr_warn("FIX_BTMAP_END:       %d\n", FIX_BTMAP_END);
 628                 pr_warn("FIX_BTMAP_BEGIN:     %d\n", FIX_BTMAP_BEGIN);
 629         }
 630 }
 631
 632 void __set_fixmap(enum fixed_addresses idx,
 633                                phys_addr_t phys, pgprot_t flags)
 634 {
 635         unsigned long addr = __fix_to_virt(idx);
 636         pte_t *pte;
 637
 638         BUG_ON(idx <= FIX_HOLE || idx >= __end_of_fixed_addresses);
 639
 640         pte = fixmap_pte(addr);
 641
 642         if (pgprot_val(flags)) {
 643                 set_pte(pte, pfn_pte(phys >> PAGE_SHIFT, flags));
 644         } else {
 645                 pte_clear(&init_mm, addr, pte);
 646                 flush_tlb_kernel_range(addr, addr+PAGE_SIZE);
 647         }
 648 }
 649
 650 void *__init fixmap_remap_fdt(phys_addr_t dt_phys)
 651 {
 652         const u64 dt_virt_base = __fix_to_virt(FIX_FDT);
 653         pgprot_t prot = PAGE_KERNEL_RO;
 654         int size, offset;
 655         void *dt_virt;
 656
 657         /*
 658          * Check whether the physical FDT address is set and meets the minimum
 659          * alignment requirement. Since we are relying on MIN_FDT_ALIGN to be
 660          * at least 8 bytes so that we can always access the size field of the
 661          * FDT header after mapping the first chunk, double check here if that
 662          * is indeed the case.
 663          */
 664         BUILD_BUG_ON(MIN_FDT_ALIGN < 8);
 665         if (!dt_phys || dt_phys % MIN_FDT_ALIGN)
 666                 return NULL;
 667
 668         /*
 669          * Make sure that the FDT region can be mapped without the need to
 670          * allocate additional translation table pages, so that it is safe
 671          * to call create_mapping() this early.
 672          *
 673          * On 64k pages, the FDT will be mapped using PTEs, so we need to
 674          * be in the same PMD as the rest of the fixmap.
 675          * On 4k pages, we'll use section mappings for the FDT so we only
 676          * have to be in the same PUD.
 677          */
 678         BUILD_BUG_ON(dt_virt_base % SZ_2M);
 679
 680         BUILD_BUG_ON(__fix_to_virt(FIX_FDT_END) >> SWAPPER_TABLE_SHIFT !=
 681                      __fix_to_virt(FIX_BTMAP_BEGIN) >> SWAPPER_TABLE_SHIFT);
 682
 683         offset = dt_phys % SWAPPER_BLOCK_SIZE;
 684         dt_virt = (void *)dt_virt_base + offset;
 685
 686         /* map the first chunk so we can read the size from the header */
 687         create_mapping(round_down(dt_phys, SWAPPER_BLOCK_SIZE), dt_virt_base,
 688                        SWAPPER_BLOCK_SIZE, prot);
 689
 690         if (fdt_check_header(dt_virt) != 0)
 691                 return NULL;
 692
 693         size = fdt_totalsize(dt_virt);
 694         if (size > MAX_FDT_SIZE)
 695                 return NULL;
 696
 697         if (offset + size > SWAPPER_BLOCK_SIZE)
 698                 create_mapping(round_down(dt_phys, SWAPPER_BLOCK_SIZE), dt_virt_base,
 699                                round_up(offset + size, SWAPPER_BLOCK_SIZE), prot);
 700
 701         memblock_reserve(dt_phys, size);
 702
 703         return dt_virt;
 704 }