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/cputype.h>
  34 #include <asm/fixmap.h>
  35 #include <asm/kernel-pgtable.h>
  36 #include <asm/sections.h>
  37 #include <asm/setup.h>
  38 #include <asm/sizes.h>
  39 #include <asm/tlb.h>
  40 #include <asm/memblock.h>
  41 #include <asm/mmu_context.h>
  42
  43 #include "mm.h"
  44
  45 u64 idmap_t0sz = TCR_T0SZ(VA_BITS);
  46
  47 /*
  48  * Empty_zero_page is a special page that is used for zero-initialized data
  49  * and COW.
  50  */
  51 struct page *empty_zero_page;
  52 EXPORT_SYMBOL(empty_zero_page);
  53
  54 pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
  55                               unsigned long size, pgprot_t vma_prot)
  56 {
  57         if (!pfn_valid(pfn))
  58                 return pgprot_noncached(vma_prot);
  59         else if (file->f_flags & O_SYNC)
  60                 return pgprot_writecombine(vma_prot);
  61         return vma_prot;
  62 }
  63 EXPORT_SYMBOL(phys_mem_access_prot);
  64
  65 static void __init *early_alloc(unsigned long sz)
  66 {
  67         phys_addr_t phys;
  68         void *ptr;
  69
  70         phys = memblock_alloc(sz, sz);
  71         BUG_ON(!phys);
  72         ptr = __va(phys);
  73         memset(ptr, 0, sz);
  74         return ptr;
  75 }
  76
  77 /*
  78  * remap a PMD into pages
  79  */
  80 static void split_pmd(pmd_t *pmd, pte_t *pte)
  81 {
  82         unsigned long pfn = pmd_pfn(*pmd);
  83         int i = 0;
  84
  85         do {
  86                 /*
  87                  * Need to have the least restrictive permissions available
  88                  * permissions will be fixed up later
  89                  */
  90                 set_pte(pte, pfn_pte(pfn, PAGE_KERNEL_EXEC));
  91                 pfn++;
  92         } while (pte++, i++, i < PTRS_PER_PTE);
  93 }
  94
  95 static void alloc_init_pte(pmd_t *pmd, unsigned long addr,
  96                                   unsigned long end, unsigned long pfn,
  97                                   pgprot_t prot,
  98                                   void *(*alloc)(unsigned long size))
  99 {
 100         pte_t *pte;
 101
 102         if (pmd_none(*pmd) || pmd_sect(*pmd)) {
 103                 pte = alloc(PTRS_PER_PTE * sizeof(pte_t));
 104                 if (pmd_sect(*pmd))
 105                         split_pmd(pmd, pte);
 106                 __pmd_populate(pmd, __pa(pte), PMD_TYPE_TABLE);
 107                 flush_tlb_all();
 108         }
 109         BUG_ON(pmd_bad(*pmd));
 110
 111         pte = pte_offset_kernel(pmd, addr);
 112         do {
 113                 set_pte(pte, pfn_pte(pfn, prot));
 114                 pfn++;
 115         } while (pte++, addr += PAGE_SIZE, addr != end);
 116 }
 117
 118 static void split_pud(pud_t *old_pud, pmd_t *pmd)
 119 {
 120         unsigned long addr = pud_pfn(*old_pud) << PAGE_SHIFT;
 121         pgprot_t prot = __pgprot(pud_val(*old_pud) ^ addr);
 122         int i = 0;
 123
 124         do {
 125                 set_pmd(pmd, __pmd(addr | pgprot_val(prot)));
 126                 addr += PMD_SIZE;
 127         } while (pmd++, i++, i < PTRS_PER_PMD);
 128 }
 129
 130 static void alloc_init_pmd(struct mm_struct *mm, pud_t *pud,
 131                                   unsigned long addr, unsigned long end,
 132                                   phys_addr_t phys, pgprot_t prot,
 133                                   void *(*alloc)(unsigned long size))
 134 {
 135         pmd_t *pmd;
 136         unsigned long next;
 137
 138         /*
 139          * Check for initial section mappings in the pgd/pud and remove them.
 140          */
 141         if (pud_none(*pud) || pud_sect(*pud)) {
 142                 pmd = alloc(PTRS_PER_PMD * sizeof(pmd_t));
 143                 if (pud_sect(*pud)) {
 144                         /*
 145                          * need to have the 1G of mappings continue to be
 146                          * present
 147                          */
 148                         split_pud(pud, pmd);
 149                 }
 150                 pud_populate(mm, pud, pmd);
 151                 flush_tlb_all();
 152         }
 153         BUG_ON(pud_bad(*pud));
 154
 155         pmd = pmd_offset(pud, addr);
 156         do {
 157                 next = pmd_addr_end(addr, end);
 158                 /* try section mapping first */
 159                 if (((addr | next | phys) & ~SECTION_MASK) == 0) {
 160                         pmd_t old_pmd =*pmd;
 161                         set_pmd(pmd, __pmd(phys |
 162                                            pgprot_val(mk_sect_prot(prot))));
 163                         /*
 164                          * Check for previous table entries created during
 165                          * boot (__create_page_tables) and flush them.
 166                          */
 167                         if (!pmd_none(old_pmd)) {
 168                                 flush_tlb_all();
 169                                 if (pmd_table(old_pmd)) {
 170                                         phys_addr_t table = __pa(pte_offset_map(&old_pmd, 0));
 171                                         if (!WARN_ON_ONCE(slab_is_available()))
 172                                                 memblock_free(table, PAGE_SIZE);
 173                                 }
 174                         }
 175                 } else {
 176                         alloc_init_pte(pmd, addr, next, __phys_to_pfn(phys),
 177                                        prot, alloc);
 178                 }
 179                 phys += next - addr;
 180         } while (pmd++, addr = next, addr != end);
 181 }
 182
 183 static inline bool use_1G_block(unsigned long addr, unsigned long next,
 184                         unsigned long phys)
 185 {
 186         if (PAGE_SHIFT != 12)
 187                 return false;
 188
 189         if (((addr | next | phys) & ~PUD_MASK) != 0)
 190                 return false;
 191
 192         return true;
 193 }
 194
 195 static void alloc_init_pud(struct mm_struct *mm, pgd_t *pgd,
 196                                   unsigned long addr, unsigned long end,
 197                                   phys_addr_t phys, pgprot_t prot,
 198                                   void *(*alloc)(unsigned long size))
 199 {
 200         pud_t *pud;
 201         unsigned long next;
 202
 203         if (pgd_none(*pgd)) {
 204                 pud = alloc(PTRS_PER_PUD * sizeof(pud_t));
 205                 pgd_populate(mm, pgd, pud);
 206         }
 207         BUG_ON(pgd_bad(*pgd));
 208
 209         pud = pud_offset(pgd, addr);
 210         do {
 211                 next = pud_addr_end(addr, end);
 212
 213                 /*
 214                  * For 4K granule only, attempt to put down a 1GB block
 215                  */
 216                 if (use_1G_block(addr, next, phys)) {
 217                         pud_t old_pud = *pud;
 218                         set_pud(pud, __pud(phys |
 219                                            pgprot_val(mk_sect_prot(prot))));
 220
 221                         /*
 222                          * If we have an old value for a pud, it will
 223                          * be pointing to a pmd table that we no longer
 224                          * need (from swapper_pg_dir).
 225                          *
 226                          * Look up the old pmd table and free it.
 227                          */
 228                         if (!pud_none(old_pud)) {
 229                                 flush_tlb_all();
 230                                 if (pud_table(old_pud)) {
 231                                         phys_addr_t table = __pa(pmd_offset(&old_pud, 0));
 232                                         if (!WARN_ON_ONCE(slab_is_available()))
 233                                                 memblock_free(table, PAGE_SIZE);
 234                                 }
 235                         }
 236                 } else {
 237                         alloc_init_pmd(mm, pud, addr, next, phys, prot, alloc);
 238                 }
 239                 phys += next - addr;
 240         } while (pud++, addr = next, addr != end);
 241 }
 242
 243 /*
 244  * Create the page directory entries and any necessary page tables for the
 245  * mapping specified by 'md'.
 246  */
 247 static void  __create_mapping(struct mm_struct *mm, pgd_t *pgd,
 248                                     phys_addr_t phys, unsigned long virt,
 249                                     phys_addr_t size, pgprot_t prot,
 250                                     void *(*alloc)(unsigned long size))
 251 {
 252         unsigned long addr, length, end, next;
 253
 254         /*
 255          * If the virtual and physical address don't have the same offset
 256          * within a page, we cannot map the region as the caller expects.
 257          */
 258         if (WARN_ON((phys ^ virt) & ~PAGE_MASK))
 259                 return;
 260
 261         phys &= PAGE_MASK;
 262         addr = virt & PAGE_MASK;
 263         length = PAGE_ALIGN(size + (virt & ~PAGE_MASK));
 264
 265         end = addr + length;
 266         do {
 267                 next = pgd_addr_end(addr, end);
 268                 alloc_init_pud(mm, pgd, addr, next, phys, prot, alloc);
 269                 phys += next - addr;
 270         } while (pgd++, addr = next, addr != end);
 271 }
 272
 273 static void *late_alloc(unsigned long size)
 274 {
 275         void *ptr;
 276
 277         BUG_ON(size > PAGE_SIZE);
 278         ptr = (void *)__get_free_page(PGALLOC_GFP);
 279         BUG_ON(!ptr);
 280         return ptr;
 281 }
 282
 283 static void __init create_mapping(phys_addr_t phys, unsigned long virt,
 284                                   phys_addr_t size, pgprot_t prot)
 285 {
 286         if (virt < VMALLOC_START) {
 287                 pr_warn("BUG: not creating mapping for %pa at 0x%016lx - outside kernel range\n",
 288                         &phys, virt);
 289                 return;
 290         }
 291         __create_mapping(&init_mm, pgd_offset_k(virt), phys, virt,
 292                          size, prot, early_alloc);
 293 }
 294
 295 void __init create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
 296                                unsigned long virt, phys_addr_t size,
 297                                pgprot_t prot)
 298 {
 299         __create_mapping(mm, pgd_offset(mm, virt), phys, virt, size, prot,
 300                                 late_alloc);
 301 }
 302
 303 static void create_mapping_late(phys_addr_t phys, unsigned long virt,
 304                                   phys_addr_t size, pgprot_t prot)
 305 {
 306         if (virt < VMALLOC_START) {
 307                 pr_warn("BUG: not creating mapping for %pa at 0x%016lx - outside kernel range\n",
 308                         &phys, virt);
 309                 return;
 310         }
 311
 312         return __create_mapping(&init_mm, pgd_offset_k(virt),
 313                                 phys, virt, size, prot, late_alloc);
 314 }
 315
 316 #ifdef CONFIG_DEBUG_RODATA
 317 static void __init __map_memblock(phys_addr_t start, phys_addr_t end)
 318 {
 319         /*
 320          * Set up the executable regions using the existing section mappings
 321          * for now. This will get more fine grained later once all memory
 322          * is mapped
 323          */
 324         unsigned long kernel_x_start = round_down(__pa(_stext), SWAPPER_BLOCK_SIZE);
 325         unsigned long kernel_x_end = round_up(__pa(__init_end), SWAPPER_BLOCK_SIZE);
 326
 327         if (end < kernel_x_start) {
 328                 create_mapping(start, __phys_to_virt(start),
 329                         end - start, PAGE_KERNEL);
 330         } else if (start >= kernel_x_end) {
 331                 create_mapping(start, __phys_to_virt(start),
 332                         end - start, PAGE_KERNEL);
 333         } else {
 334                 if (start < kernel_x_start)
 335                         create_mapping(start, __phys_to_virt(start),
 336                                 kernel_x_start - start,
 337                                 PAGE_KERNEL);
 338                 create_mapping(kernel_x_start,
 339                                 __phys_to_virt(kernel_x_start),
 340                                 kernel_x_end - kernel_x_start,
 341                                 PAGE_KERNEL_EXEC);
 342                 if (kernel_x_end < end)
 343                         create_mapping(kernel_x_end,
 344                                 __phys_to_virt(kernel_x_end),
 345                                 end - kernel_x_end,
 346                                 PAGE_KERNEL);
 347         }
 348
 349 }
 350 #else
 351 static void __init __map_memblock(phys_addr_t start, phys_addr_t end)
 352 {
 353         create_mapping(start, __phys_to_virt(start), end - start,
 354                         PAGE_KERNEL_EXEC);
 355 }
 356 #endif
 357
 358 static void __init map_mem(void)
 359 {
 360         struct memblock_region *reg;
 361         phys_addr_t limit;
 362
 363         /*
 364          * Temporarily limit the memblock range. We need to do this as
 365          * create_mapping requires puds, pmds and ptes to be allocated from
 366          * memory addressable from the initial direct kernel mapping.
 367          *
 368          * The initial direct kernel mapping, located at swapper_pg_dir, gives
 369          * us PUD_SIZE (with SECTION maps) or PMD_SIZE (without SECTION maps,
 370          * memory starting from PHYS_OFFSET (which must be aligned to 2MB as
 371          * per Documentation/arm64/booting.txt).
 372          */
 373         limit = PHYS_OFFSET + SWAPPER_INIT_MAP_SIZE;
 374         memblock_set_current_limit(limit);
 375
 376         /* map all the memory banks */
 377         for_each_memblock(memory, reg) {
 378                 phys_addr_t start = reg->base;
 379                 phys_addr_t end = start + reg->size;
 380
 381                 if (start >= end)
 382                         break;
 383                 if (memblock_is_nomap(reg))
 384                         continue;
 385
 386                 if (ARM64_SWAPPER_USES_SECTION_MAPS) {
 387                         /*
 388                          * For the first memory bank align the start address and
 389                          * current memblock limit to prevent create_mapping() from
 390                          * allocating pte page tables from unmapped memory. With
 391                          * the section maps, if the first block doesn't end on section
 392                          * size boundary, create_mapping() will try to allocate a pte
 393                          * page, which may be returned from an unmapped area.
 394                          * When section maps are not used, the pte page table for the
 395                          * current limit is already present in swapper_pg_dir.
 396                          */
 397                         if (start < limit)
 398                                 start = ALIGN(start, SECTION_SIZE);
 399                         if (end < limit) {
 400                                 limit = end & SECTION_MASK;
 401                                 memblock_set_current_limit(limit);
 402                         }
 403                 }
 404                 __map_memblock(start, end);
 405         }
 406
 407         /* Limit no longer required. */
 408         memblock_set_current_limit(MEMBLOCK_ALLOC_ANYWHERE);
 409 }
 410
 411 static void __init fixup_executable(void)
 412 {
 413 #ifdef CONFIG_DEBUG_RODATA
 414         /* now that we are actually fully mapped, make the start/end more fine grained */
 415         if (!IS_ALIGNED((unsigned long)_stext, SWAPPER_BLOCK_SIZE)) {
 416                 unsigned long aligned_start = round_down(__pa(_stext),
 417                                                          SWAPPER_BLOCK_SIZE);
 418
 419                 create_mapping(aligned_start, __phys_to_virt(aligned_start),
 420                                 __pa(_stext) - aligned_start,
 421                                 PAGE_KERNEL);
 422         }
 423
 424         if (!IS_ALIGNED((unsigned long)__init_end, SWAPPER_BLOCK_SIZE)) {
 425                 unsigned long aligned_end = round_up(__pa(__init_end),
 426                                                           SWAPPER_BLOCK_SIZE);
 427                 create_mapping(__pa(__init_end), (unsigned long)__init_end,
 428                                 aligned_end - __pa(__init_end),
 429                                 PAGE_KERNEL);
 430         }
 431 #endif
 432 }
 433
 434 #ifdef CONFIG_DEBUG_RODATA
 435 void mark_rodata_ro(void)
 436 {
 437         create_mapping_late(__pa(_stext), (unsigned long)_stext,
 438                                 (unsigned long)_etext - (unsigned long)_stext,
 439                                 PAGE_KERNEL_ROX);
 440
 441 }
 442 #endif
 443
 444 void fixup_init(void)
 445 {
 446         create_mapping_late(__pa(__init_begin), (unsigned long)__init_begin,
 447                         (unsigned long)__init_end - (unsigned long)__init_begin,
 448                         PAGE_KERNEL);
 449 }
 450
 451 /*
 452  * paging_init() sets up the page tables, initialises the zone memory
 453  * maps and sets up the zero page.
 454  */
 455 void __init paging_init(void)
 456 {
 457         void *zero_page;
 458
 459         map_mem();
 460         fixup_executable();
 461
 462         /* allocate the zero page. */
 463         zero_page = early_alloc(PAGE_SIZE);
 464
 465         bootmem_init();
 466
 467         empty_zero_page = virt_to_page(zero_page);
 468
 469         /* Ensure the zero page is visible to the page table walker */
 470         dsb(ishst);
 471
 472         /*
 473          * TTBR0 is only used for the identity mapping at this stage. Make it
 474          * point to zero page to avoid speculatively fetching new entries.
 475          */
 476         cpu_set_reserved_ttbr0();
 477         local_flush_tlb_all();
 478         cpu_set_default_tcr_t0sz();
 479 }
 480
 481 /*
 482  * Check whether a kernel address is valid (derived from arch/x86/).
 483  */
 484 int kern_addr_valid(unsigned long addr)
 485 {
 486         pgd_t *pgd;
 487         pud_t *pud;
 488         pmd_t *pmd;
 489         pte_t *pte;
 490
 491         if ((((long)addr) >> VA_BITS) != -1UL)
 492                 return 0;
 493
 494         pgd = pgd_offset_k(addr);
 495         if (pgd_none(*pgd))
 496                 return 0;
 497
 498         pud = pud_offset(pgd, addr);
 499         if (pud_none(*pud))
 500                 return 0;
 501
 502         if (pud_sect(*pud))
 503                 return pfn_valid(pud_pfn(*pud));
 504
 505         pmd = pmd_offset(pud, addr);
 506         if (pmd_none(*pmd))
 507                 return 0;
 508
 509         if (pmd_sect(*pmd))
 510                 return pfn_valid(pmd_pfn(*pmd));
 511
 512         pte = pte_offset_kernel(pmd, addr);
 513         if (pte_none(*pte))
 514                 return 0;
 515
 516         return pfn_valid(pte_pfn(*pte));
 517 }
 518 #ifdef CONFIG_SPARSEMEM_VMEMMAP
 519 #if !ARM64_SWAPPER_USES_SECTION_MAPS
 520 int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
 521 {
 522         return vmemmap_populate_basepages(start, end, node);
 523 }
 524 #else   /* !ARM64_SWAPPER_USES_SECTION_MAPS */
 525 int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
 526 {
 527         unsigned long addr = start;
 528         unsigned long next;
 529         pgd_t *pgd;
 530         pud_t *pud;
 531         pmd_t *pmd;
 532
 533         do {
 534                 next = pmd_addr_end(addr, end);
 535
 536                 pgd = vmemmap_pgd_populate(addr, node);
 537                 if (!pgd)
 538                         return -ENOMEM;
 539
 540                 pud = vmemmap_pud_populate(pgd, addr, node);
 541                 if (!pud)
 542                         return -ENOMEM;
 543
 544                 pmd = pmd_offset(pud, addr);
 545                 if (pmd_none(*pmd)) {
 546                         void *p = NULL;
 547
 548                         p = vmemmap_alloc_block_buf(PMD_SIZE, node);
 549                         if (!p)
 550                                 return -ENOMEM;
 551
 552                         set_pmd(pmd, __pmd(__pa(p) | PROT_SECT_NORMAL));
 553                 } else
 554                         vmemmap_verify((pte_t *)pmd, node, addr, next);
 555         } while (addr = next, addr != end);
 556
 557         return 0;
 558 }
 559 #endif  /* CONFIG_ARM64_64K_PAGES */
 560 void vmemmap_free(unsigned long start, unsigned long end)
 561 {
 562 }
 563 #endif  /* CONFIG_SPARSEMEM_VMEMMAP */
 564
 565 static pte_t bm_pte[PTRS_PER_PTE] __page_aligned_bss;
 566 #if CONFIG_PGTABLE_LEVELS > 2
 567 static pmd_t bm_pmd[PTRS_PER_PMD] __page_aligned_bss;
 568 #endif
 569 #if CONFIG_PGTABLE_LEVELS > 3
 570 static pud_t bm_pud[PTRS_PER_PUD] __page_aligned_bss;
 571 #endif
 572
 573 static inline pud_t * fixmap_pud(unsigned long addr)
 574 {
 575         pgd_t *pgd = pgd_offset_k(addr);
 576
 577         BUG_ON(pgd_none(*pgd) || pgd_bad(*pgd));
 578
 579         return pud_offset(pgd, addr);
 580 }
 581
 582 static inline pmd_t * fixmap_pmd(unsigned long addr)
 583 {
 584         pud_t *pud = fixmap_pud(addr);
 585
 586         BUG_ON(pud_none(*pud) || pud_bad(*pud));
 587
 588         return pmd_offset(pud, addr);
 589 }
 590
 591 static inline pte_t * fixmap_pte(unsigned long addr)
 592 {
 593         pmd_t *pmd = fixmap_pmd(addr);
 594
 595         BUG_ON(pmd_none(*pmd) || pmd_bad(*pmd));
 596
 597         return pte_offset_kernel(pmd, addr);
 598 }
 599
 600 void __init early_fixmap_init(void)
 601 {
 602         pgd_t *pgd;
 603         pud_t *pud;
 604         pmd_t *pmd;
 605         unsigned long addr = FIXADDR_START;
 606
 607         pgd = pgd_offset_k(addr);
 608         pgd_populate(&init_mm, pgd, bm_pud);
 609         pud = pud_offset(pgd, addr);
 610         pud_populate(&init_mm, pud, bm_pmd);
 611         pmd = pmd_offset(pud, addr);
 612         pmd_populate_kernel(&init_mm, pmd, bm_pte);
 613
 614         /*
 615          * The boot-ioremap range spans multiple pmds, for which
 616          * we are not preparted:
 617          */
 618         BUILD_BUG_ON((__fix_to_virt(FIX_BTMAP_BEGIN) >> PMD_SHIFT)
 619                      != (__fix_to_virt(FIX_BTMAP_END) >> PMD_SHIFT));
 620
 621         if ((pmd != fixmap_pmd(fix_to_virt(FIX_BTMAP_BEGIN)))
 622              || pmd != fixmap_pmd(fix_to_virt(FIX_BTMAP_END))) {
 623                 WARN_ON(1);
 624                 pr_warn("pmd %p != %p, %p\n",
 625                         pmd, fixmap_pmd(fix_to_virt(FIX_BTMAP_BEGIN)),
 626                         fixmap_pmd(fix_to_virt(FIX_BTMAP_END)));
 627                 pr_warn("fix_to_virt(FIX_BTMAP_BEGIN): %08lx\n",
 628                         fix_to_virt(FIX_BTMAP_BEGIN));
 629                 pr_warn("fix_to_virt(FIX_BTMAP_END):   %08lx\n",
 630                         fix_to_virt(FIX_BTMAP_END));
 631
 632                 pr_warn("FIX_BTMAP_END:       %d\n", FIX_BTMAP_END);
 633                 pr_warn("FIX_BTMAP_BEGIN:     %d\n", FIX_BTMAP_BEGIN);
 634         }
 635 }
 636
 637 void __set_fixmap(enum fixed_addresses idx,
 638                                phys_addr_t phys, pgprot_t flags)
 639 {
 640         unsigned long addr = __fix_to_virt(idx);
 641         pte_t *pte;
 642
 643         BUG_ON(idx <= FIX_HOLE || idx >= __end_of_fixed_addresses);
 644
 645         pte = fixmap_pte(addr);
 646
 647         if (pgprot_val(flags)) {
 648                 set_pte(pte, pfn_pte(phys >> PAGE_SHIFT, flags));
 649         } else {
 650                 pte_clear(&init_mm, addr, pte);
 651                 flush_tlb_kernel_range(addr, addr+PAGE_SIZE);
 652         }
 653 }
 654
 655 void *__init fixmap_remap_fdt(phys_addr_t dt_phys)
 656 {
 657         const u64 dt_virt_base = __fix_to_virt(FIX_FDT);
 658         pgprot_t prot = PAGE_KERNEL_RO;
 659         int size, offset;
 660         void *dt_virt;
 661
 662         /*
 663          * Check whether the physical FDT address is set and meets the minimum
 664          * alignment requirement. Since we are relying on MIN_FDT_ALIGN to be
 665          * at least 8 bytes so that we can always access the size field of the
 666          * FDT header after mapping the first chunk, double check here if that
 667          * is indeed the case.
 668          */
 669         BUILD_BUG_ON(MIN_FDT_ALIGN < 8);
 670         if (!dt_phys || dt_phys % MIN_FDT_ALIGN)
 671                 return NULL;
 672
 673         /*
 674          * Make sure that the FDT region can be mapped without the need to
 675          * allocate additional translation table pages, so that it is safe
 676          * to call create_mapping() this early.
 677          *
 678          * On 64k pages, the FDT will be mapped using PTEs, so we need to
 679          * be in the same PMD as the rest of the fixmap.
 680          * On 4k pages, we'll use section mappings for the FDT so we only
 681          * have to be in the same PUD.
 682          */
 683         BUILD_BUG_ON(dt_virt_base % SZ_2M);
 684
 685         BUILD_BUG_ON(__fix_to_virt(FIX_FDT_END) >> SWAPPER_TABLE_SHIFT !=
 686                      __fix_to_virt(FIX_BTMAP_BEGIN) >> SWAPPER_TABLE_SHIFT);
 687
 688         offset = dt_phys % SWAPPER_BLOCK_SIZE;
 689         dt_virt = (void *)dt_virt_base + offset;
 690
 691         /* map the first chunk so we can read the size from the header */
 692         create_mapping(round_down(dt_phys, SWAPPER_BLOCK_SIZE), dt_virt_base,
 693                        SWAPPER_BLOCK_SIZE, prot);
 694
 695         if (fdt_check_header(dt_virt) != 0)
 696                 return NULL;
 697
 698         size = fdt_totalsize(dt_virt);
 699         if (size > MAX_FDT_SIZE)
 700                 return NULL;
 701
 702         if (offset + size > SWAPPER_BLOCK_SIZE)
 703                 create_mapping(round_down(dt_phys, SWAPPER_BLOCK_SIZE), dt_virt_base,
 704                                round_up(offset + size, SWAPPER_BLOCK_SIZE), prot);
 705
 706         memblock_reserve(dt_phys, size);
 707
 708         return dt_virt;
 709 }