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/kasan.h>
  37 #include <asm/kernel-pgtable.h>
  38 #include <asm/sections.h>
  39 #include <asm/setup.h>
  40 #include <asm/sizes.h>
  41 #include <asm/tlb.h>
  42 #include <asm/memblock.h>
  43 #include <asm/mmu_context.h>
  44
  45 #include "mm.h"
  46
  47 u64 idmap_t0sz = TCR_T0SZ(VA_BITS);
  48
  49 /*
  50  * Empty_zero_page is a special page that is used for zero-initialized data
  51  * and COW.
  52  */
  53 unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss;
  54 EXPORT_SYMBOL(empty_zero_page);
  55
  56 pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
  57                               unsigned long size, pgprot_t vma_prot)
  58 {
  59         if (!pfn_valid(pfn))
  60                 return pgprot_noncached(vma_prot);
  61         else if (file->f_flags & O_SYNC)
  62                 return pgprot_writecombine(vma_prot);
  63         return vma_prot;
  64 }
  65 EXPORT_SYMBOL(phys_mem_access_prot);
  66
  67 static phys_addr_t __init early_pgtable_alloc(void)
  68 {
  69         phys_addr_t phys;
  70         void *ptr;
  71
  72         phys = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
  73         BUG_ON(!phys);
  74
  75         /*
  76          * The FIX_{PGD,PUD,PMD} slots may be in active use, but the FIX_PTE
  77          * slot will be free, so we can (ab)use the FIX_PTE slot to initialise
  78          * any level of table.
  79          */
  80         ptr = pte_set_fixmap(phys);
  81
  82         memset(ptr, 0, PAGE_SIZE);
  83
  84         /*
  85          * Implicit barriers also ensure the zeroed page is visible to the page
  86          * table walker
  87          */
  88         pte_clear_fixmap();
  89
  90         return phys;
  91 }
  92
  93 /*
  94  * remap a PMD into pages
  95  */
  96 static void split_pmd(pmd_t *pmd, pte_t *pte)
  97 {
  98         unsigned long pfn = pmd_pfn(*pmd);
  99         int i = 0;
 100
 101         do {
 102                 /*
 103                  * Need to have the least restrictive permissions available
 104                  * permissions will be fixed up later
 105                  */
 106                 set_pte(pte, pfn_pte(pfn, PAGE_KERNEL_EXEC));
 107                 pfn++;
 108         } while (pte++, i++, i < PTRS_PER_PTE);
 109 }
 110
 111 static void alloc_init_pte(pmd_t *pmd, unsigned long addr,
 112                                   unsigned long end, unsigned long pfn,
 113                                   pgprot_t prot,
 114                                   phys_addr_t (*pgtable_alloc)(void))
 115 {
 116         pte_t *pte;
 117
 118         if (pmd_none(*pmd) || pmd_sect(*pmd)) {
 119                 phys_addr_t pte_phys = pgtable_alloc();
 120                 pte = pte_set_fixmap(pte_phys);
 121                 if (pmd_sect(*pmd))
 122                         split_pmd(pmd, pte);
 123                 __pmd_populate(pmd, pte_phys, PMD_TYPE_TABLE);
 124                 flush_tlb_all();
 125                 pte_clear_fixmap();
 126         }
 127         BUG_ON(pmd_bad(*pmd));
 128
 129         pte = pte_set_fixmap_offset(pmd, addr);
 130         do {
 131                 set_pte(pte, pfn_pte(pfn, prot));
 132                 pfn++;
 133         } while (pte++, addr += PAGE_SIZE, addr != end);
 134
 135         pte_clear_fixmap();
 136 }
 137
 138 static void split_pud(pud_t *old_pud, pmd_t *pmd)
 139 {
 140         unsigned long addr = pud_pfn(*old_pud) << PAGE_SHIFT;
 141         pgprot_t prot = __pgprot(pud_val(*old_pud) ^ addr);
 142         int i = 0;
 143
 144         do {
 145                 set_pmd(pmd, __pmd(addr | pgprot_val(prot)));
 146                 addr += PMD_SIZE;
 147         } while (pmd++, i++, i < PTRS_PER_PMD);
 148 }
 149
 150 static void alloc_init_pmd(pud_t *pud, unsigned long addr, unsigned long end,
 151                                   phys_addr_t phys, pgprot_t prot,
 152                                   phys_addr_t (*pgtable_alloc)(void))
 153 {
 154         pmd_t *pmd;
 155         unsigned long next;
 156
 157         /*
 158          * Check for initial section mappings in the pgd/pud and remove them.
 159          */
 160         if (pud_none(*pud) || pud_sect(*pud)) {
 161                 phys_addr_t pmd_phys = pgtable_alloc();
 162                 pmd = pmd_set_fixmap(pmd_phys);
 163                 if (pud_sect(*pud)) {
 164                         /*
 165                          * need to have the 1G of mappings continue to be
 166                          * present
 167                          */
 168                         split_pud(pud, pmd);
 169                 }
 170                 __pud_populate(pud, pmd_phys, PUD_TYPE_TABLE);
 171                 flush_tlb_all();
 172                 pmd_clear_fixmap();
 173         }
 174         BUG_ON(pud_bad(*pud));
 175
 176         pmd = pmd_set_fixmap_offset(pud, addr);
 177         do {
 178                 next = pmd_addr_end(addr, end);
 179                 /* try section mapping first */
 180                 if (((addr | next | phys) & ~SECTION_MASK) == 0) {
 181                         pmd_t old_pmd =*pmd;
 182                         set_pmd(pmd, __pmd(phys |
 183                                            pgprot_val(mk_sect_prot(prot))));
 184                         /*
 185                          * Check for previous table entries created during
 186                          * boot (__create_page_tables) and flush them.
 187                          */
 188                         if (!pmd_none(old_pmd)) {
 189                                 flush_tlb_all();
 190                                 if (pmd_table(old_pmd)) {
 191                                         phys_addr_t table = pmd_page_paddr(old_pmd);
 192                                         if (!WARN_ON_ONCE(slab_is_available()))
 193                                                 memblock_free(table, PAGE_SIZE);
 194                                 }
 195                         }
 196                 } else {
 197                         alloc_init_pte(pmd, addr, next, __phys_to_pfn(phys),
 198                                        prot, pgtable_alloc);
 199                 }
 200                 phys += next - addr;
 201         } while (pmd++, addr = next, addr != end);
 202
 203         pmd_clear_fixmap();
 204 }
 205
 206 static inline bool use_1G_block(unsigned long addr, unsigned long next,
 207                         unsigned long phys)
 208 {
 209         if (PAGE_SHIFT != 12)
 210                 return false;
 211
 212         if (((addr | next | phys) & ~PUD_MASK) != 0)
 213                 return false;
 214
 215         return true;
 216 }
 217
 218 static void alloc_init_pud(pgd_t *pgd, unsigned long addr, unsigned long end,
 219                                   phys_addr_t phys, pgprot_t prot,
 220                                   phys_addr_t (*pgtable_alloc)(void))
 221 {
 222         pud_t *pud;
 223         unsigned long next;
 224
 225         if (pgd_none(*pgd)) {
 226                 phys_addr_t pud_phys = pgtable_alloc();
 227                 __pgd_populate(pgd, pud_phys, PUD_TYPE_TABLE);
 228         }
 229         BUG_ON(pgd_bad(*pgd));
 230
 231         pud = pud_set_fixmap_offset(pgd, addr);
 232         do {
 233                 next = pud_addr_end(addr, end);
 234
 235                 /*
 236                  * For 4K granule only, attempt to put down a 1GB block
 237                  */
 238                 if (use_1G_block(addr, next, phys)) {
 239                         pud_t old_pud = *pud;
 240                         set_pud(pud, __pud(phys |
 241                                            pgprot_val(mk_sect_prot(prot))));
 242
 243                         /*
 244                          * If we have an old value for a pud, it will
 245                          * be pointing to a pmd table that we no longer
 246                          * need (from swapper_pg_dir).
 247                          *
 248                          * Look up the old pmd table and free it.
 249                          */
 250                         if (!pud_none(old_pud)) {
 251                                 flush_tlb_all();
 252                                 if (pud_table(old_pud)) {
 253                                         phys_addr_t table = pud_page_paddr(old_pud);
 254                                         if (!WARN_ON_ONCE(slab_is_available()))
 255                                                 memblock_free(table, PAGE_SIZE);
 256                                 }
 257                         }
 258                 } else {
 259                         alloc_init_pmd(pud, addr, next, phys, prot,
 260                                        pgtable_alloc);
 261                 }
 262                 phys += next - addr;
 263         } while (pud++, addr = next, addr != end);
 264
 265         pud_clear_fixmap();
 266 }
 267
 268 /*
 269  * Create the page directory entries and any necessary page tables for the
 270  * mapping specified by 'md'.
 271  */
 272 static void init_pgd(pgd_t *pgd, phys_addr_t phys, unsigned long virt,
 273                                     phys_addr_t size, pgprot_t prot,
 274                                     phys_addr_t (*pgtable_alloc)(void))
 275 {
 276         unsigned long addr, length, end, next;
 277
 278         addr = virt & PAGE_MASK;
 279         length = PAGE_ALIGN(size + (virt & ~PAGE_MASK));
 280
 281         end = addr + length;
 282         do {
 283                 next = pgd_addr_end(addr, end);
 284                 alloc_init_pud(pgd, addr, next, phys, prot, pgtable_alloc);
 285                 phys += next - addr;
 286         } while (pgd++, addr = next, addr != end);
 287 }
 288
 289 static phys_addr_t late_pgtable_alloc(void)
 290 {
 291         void *ptr = (void *)__get_free_page(PGALLOC_GFP);
 292         BUG_ON(!ptr);
 293
 294         /* Ensure the zeroed page is visible to the page table walker */
 295         dsb(ishst);
 296         return __pa(ptr);
 297 }
 298
 299 static void __create_pgd_mapping(pgd_t *pgdir, phys_addr_t phys,
 300                                  unsigned long virt, phys_addr_t size,
 301                                  pgprot_t prot,
 302                                  phys_addr_t (*alloc)(void))
 303 {
 304         init_pgd(pgd_offset_raw(pgdir, virt), phys, virt, size, prot, alloc);
 305 }
 306
 307 static void __init create_mapping(phys_addr_t phys, unsigned long virt,
 308                                   phys_addr_t size, pgprot_t prot)
 309 {
 310         if (virt < VMALLOC_START) {
 311                 pr_warn("BUG: not creating mapping for %pa at 0x%016lx - outside kernel range\n",
 312                         &phys, virt);
 313                 return;
 314         }
 315         __create_pgd_mapping(init_mm.pgd, phys, virt, size, prot,
 316                              early_pgtable_alloc);
 317 }
 318
 319 void __init create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
 320                                unsigned long virt, phys_addr_t size,
 321                                pgprot_t prot)
 322 {
 323         __create_pgd_mapping(mm->pgd, phys, virt, size, prot,
 324                              late_pgtable_alloc);
 325 }
 326
 327 static void create_mapping_late(phys_addr_t phys, unsigned long virt,
 328                                   phys_addr_t size, pgprot_t prot)
 329 {
 330         if (virt < VMALLOC_START) {
 331                 pr_warn("BUG: not creating mapping for %pa at 0x%016lx - outside kernel range\n",
 332                         &phys, virt);
 333                 return;
 334         }
 335
 336         __create_pgd_mapping(init_mm.pgd, phys, virt, size, prot,
 337                              late_pgtable_alloc);
 338 }
 339
 340 static void __init __map_memblock(pgd_t *pgd, phys_addr_t start, phys_addr_t end)
 341 {
 342
 343         unsigned long kernel_start = __pa(_stext);
 344         unsigned long kernel_end = __pa(_end);
 345
 346         /*
 347          * The kernel itself is mapped at page granularity. Map all other
 348          * memory, making sure we don't overwrite the existing kernel mappings.
 349          */
 350
 351         /* No overlap with the kernel. */
 352         if (end < kernel_start || start >= kernel_end) {
 353                 __create_pgd_mapping(pgd, start, __phys_to_virt(start),
 354                                      end - start, PAGE_KERNEL,
 355                                      early_pgtable_alloc);
 356                 return;
 357         }
 358
 359         /*
 360          * This block overlaps the kernel mapping. Map the portion(s) which
 361          * don't overlap.
 362          */
 363         if (start < kernel_start)
 364                 __create_pgd_mapping(pgd, start,
 365                                      __phys_to_virt(start),
 366                                      kernel_start - start, PAGE_KERNEL,
 367                                      early_pgtable_alloc);
 368         if (kernel_end < end)
 369                 __create_pgd_mapping(pgd, kernel_end,
 370                                      __phys_to_virt(kernel_end),
 371                                      end - kernel_end, PAGE_KERNEL,
 372                                      early_pgtable_alloc);
 373 }
 374
 375 static void __init map_mem(pgd_t *pgd)
 376 {
 377         struct memblock_region *reg;
 378
 379         /* map all the memory banks */
 380         for_each_memblock(memory, reg) {
 381                 phys_addr_t start = reg->base;
 382                 phys_addr_t end = start + reg->size;
 383
 384                 if (start >= end)
 385                         break;
 386
 387                 __map_memblock(pgd, start, end);
 388         }
 389 }
 390
 391 #ifdef CONFIG_DEBUG_RODATA
 392 void mark_rodata_ro(void)
 393 {
 394         create_mapping_late(__pa(_stext), (unsigned long)_stext,
 395                                 (unsigned long)_etext - (unsigned long)_stext,
 396                                 PAGE_KERNEL_ROX);
 397
 398 }
 399 #endif
 400
 401 void fixup_init(void)
 402 {
 403         create_mapping_late(__pa(__init_begin), (unsigned long)__init_begin,
 404                         (unsigned long)__init_end - (unsigned long)__init_begin,
 405                         PAGE_KERNEL);
 406 }
 407
 408 static void __init map_kernel_chunk(pgd_t *pgd, void *va_start, void *va_end,
 409                                     pgprot_t prot)
 410 {
 411         phys_addr_t pa_start = __pa(va_start);
 412         unsigned long size = va_end - va_start;
 413
 414         BUG_ON(!PAGE_ALIGNED(pa_start));
 415         BUG_ON(!PAGE_ALIGNED(size));
 416
 417         __create_pgd_mapping(pgd, pa_start, (unsigned long)va_start, size, prot,
 418                              early_pgtable_alloc);
 419 }
 420
 421 /*
 422  * Create fine-grained mappings for the kernel.
 423  */
 424 static void __init map_kernel(pgd_t *pgd)
 425 {
 426
 427         map_kernel_chunk(pgd, _stext, _etext, PAGE_KERNEL_EXEC);
 428         map_kernel_chunk(pgd, __init_begin, __init_end, PAGE_KERNEL_EXEC);
 429         map_kernel_chunk(pgd, _data, _end, PAGE_KERNEL);
 430
 431         /*
 432          * The fixmap falls in a separate pgd to the kernel, and doesn't live
 433          * in the carveout for the swapper_pg_dir. We can simply re-use the
 434          * existing dir for the fixmap.
 435          */
 436         set_pgd(pgd_offset_raw(pgd, FIXADDR_START), *pgd_offset_k(FIXADDR_START));
 437
 438         kasan_copy_shadow(pgd);
 439 }
 440
 441 /*
 442  * paging_init() sets up the page tables, initialises the zone memory
 443  * maps and sets up the zero page.
 444  */
 445 void __init paging_init(void)
 446 {
 447         phys_addr_t pgd_phys = early_pgtable_alloc();
 448         pgd_t *pgd = pgd_set_fixmap(pgd_phys);
 449
 450         map_kernel(pgd);
 451         map_mem(pgd);
 452
 453         /*
 454          * We want to reuse the original swapper_pg_dir so we don't have to
 455          * communicate the new address to non-coherent secondaries in
 456          * secondary_entry, and so cpu_switch_mm can generate the address with
 457          * adrp+add rather than a load from some global variable.
 458          *
 459          * To do this we need to go via a temporary pgd.
 460          */
 461         cpu_replace_ttbr1(__va(pgd_phys));
 462         memcpy(swapper_pg_dir, pgd, PAGE_SIZE);
 463         cpu_replace_ttbr1(swapper_pg_dir);
 464
 465         pgd_clear_fixmap();
 466         memblock_free(pgd_phys, PAGE_SIZE);
 467
 468         /*
 469          * We only reuse the PGD from the swapper_pg_dir, not the pud + pmd
 470          * allocated with it.
 471          */
 472         memblock_free(__pa(swapper_pg_dir) + PAGE_SIZE,
 473                       SWAPPER_DIR_SIZE - PAGE_SIZE);
 474
 475         bootmem_init();
 476 }
 477
 478 /*
 479  * Check whether a kernel address is valid (derived from arch/x86/).
 480  */
 481 int kern_addr_valid(unsigned long addr)
 482 {
 483         pgd_t *pgd;
 484         pud_t *pud;
 485         pmd_t *pmd;
 486         pte_t *pte;
 487
 488         if ((((long)addr) >> VA_BITS) != -1UL)
 489                 return 0;
 490
 491         pgd = pgd_offset_k(addr);
 492         if (pgd_none(*pgd))
 493                 return 0;
 494
 495         pud = pud_offset(pgd, addr);
 496         if (pud_none(*pud))
 497                 return 0;
 498
 499         if (pud_sect(*pud))
 500                 return pfn_valid(pud_pfn(*pud));
 501
 502         pmd = pmd_offset(pud, addr);
 503         if (pmd_none(*pmd))
 504                 return 0;
 505
 506         if (pmd_sect(*pmd))
 507                 return pfn_valid(pmd_pfn(*pmd));
 508
 509         pte = pte_offset_kernel(pmd, addr);
 510         if (pte_none(*pte))
 511                 return 0;
 512
 513         return pfn_valid(pte_pfn(*pte));
 514 }
 515 #ifdef CONFIG_SPARSEMEM_VMEMMAP
 516 #if !ARM64_SWAPPER_USES_SECTION_MAPS
 517 int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
 518 {
 519         return vmemmap_populate_basepages(start, end, node);
 520 }
 521 #else   /* !ARM64_SWAPPER_USES_SECTION_MAPS */
 522 int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
 523 {
 524         unsigned long addr = start;
 525         unsigned long next;
 526         pgd_t *pgd;
 527         pud_t *pud;
 528         pmd_t *pmd;
 529
 530         do {
 531                 next = pmd_addr_end(addr, end);
 532
 533                 pgd = vmemmap_pgd_populate(addr, node);
 534                 if (!pgd)
 535                         return -ENOMEM;
 536
 537                 pud = vmemmap_pud_populate(pgd, addr, node);
 538                 if (!pud)
 539                         return -ENOMEM;
 540
 541                 pmd = pmd_offset(pud, addr);
 542                 if (pmd_none(*pmd)) {
 543                         void *p = NULL;
 544
 545                         p = vmemmap_alloc_block_buf(PMD_SIZE, node);
 546                         if (!p)
 547                                 return -ENOMEM;
 548
 549                         set_pmd(pmd, __pmd(__pa(p) | PROT_SECT_NORMAL));
 550                 } else
 551                         vmemmap_verify((pte_t *)pmd, node, addr, next);
 552         } while (addr = next, addr != end);
 553
 554         return 0;
 555 }
 556 #endif  /* CONFIG_ARM64_64K_PAGES */
 557 void vmemmap_free(unsigned long start, unsigned long end)
 558 {
 559 }
 560 #endif  /* CONFIG_SPARSEMEM_VMEMMAP */
 561
 562 static pte_t bm_pte[PTRS_PER_PTE] __page_aligned_bss;
 563 #if CONFIG_PGTABLE_LEVELS > 2
 564 static pmd_t bm_pmd[PTRS_PER_PMD] __page_aligned_bss;
 565 #endif
 566 #if CONFIG_PGTABLE_LEVELS > 3
 567 static pud_t bm_pud[PTRS_PER_PUD] __page_aligned_bss;
 568 #endif
 569
 570 static inline pud_t * fixmap_pud(unsigned long addr)
 571 {
 572         pgd_t *pgd = pgd_offset_k(addr);
 573
 574         BUG_ON(pgd_none(*pgd) || pgd_bad(*pgd));
 575
 576         return pud_offset(pgd, addr);
 577 }
 578
 579 static inline pmd_t * fixmap_pmd(unsigned long addr)
 580 {
 581         pud_t *pud = fixmap_pud(addr);
 582
 583         BUG_ON(pud_none(*pud) || pud_bad(*pud));
 584
 585         return pmd_offset(pud, addr);
 586 }
 587
 588 static inline pte_t * fixmap_pte(unsigned long addr)
 589 {
 590         pmd_t *pmd = fixmap_pmd(addr);
 591
 592         BUG_ON(pmd_none(*pmd) || pmd_bad(*pmd));
 593
 594         return pte_offset_kernel(pmd, addr);
 595 }
 596
 597 void __init early_fixmap_init(void)
 598 {
 599         pgd_t *pgd;
 600         pud_t *pud;
 601         pmd_t *pmd;
 602         unsigned long addr = FIXADDR_START;
 603
 604         pgd = pgd_offset_k(addr);
 605         pgd_populate(&init_mm, pgd, bm_pud);
 606         pud = pud_offset(pgd, addr);
 607         pud_populate(&init_mm, pud, bm_pmd);
 608         pmd = pmd_offset(pud, addr);
 609         pmd_populate_kernel(&init_mm, pmd, bm_pte);
 610
 611         /*
 612          * The boot-ioremap range spans multiple pmds, for which
 613          * we are not preparted:
 614          */
 615         BUILD_BUG_ON((__fix_to_virt(FIX_BTMAP_BEGIN) >> PMD_SHIFT)
 616                      != (__fix_to_virt(FIX_BTMAP_END) >> PMD_SHIFT));
 617
 618         if ((pmd != fixmap_pmd(fix_to_virt(FIX_BTMAP_BEGIN)))
 619              || pmd != fixmap_pmd(fix_to_virt(FIX_BTMAP_END))) {
 620                 WARN_ON(1);
 621                 pr_warn("pmd %p != %p, %p\n",
 622                         pmd, fixmap_pmd(fix_to_virt(FIX_BTMAP_BEGIN)),
 623                         fixmap_pmd(fix_to_virt(FIX_BTMAP_END)));
 624                 pr_warn("fix_to_virt(FIX_BTMAP_BEGIN): %08lx\n",
 625                         fix_to_virt(FIX_BTMAP_BEGIN));
 626                 pr_warn("fix_to_virt(FIX_BTMAP_END):   %08lx\n",
 627                         fix_to_virt(FIX_BTMAP_END));
 628
 629                 pr_warn("FIX_BTMAP_END:       %d\n", FIX_BTMAP_END);
 630                 pr_warn("FIX_BTMAP_BEGIN:     %d\n", FIX_BTMAP_BEGIN);
 631         }
 632 }
 633
 634 void __set_fixmap(enum fixed_addresses idx,
 635                                phys_addr_t phys, pgprot_t flags)
 636 {
 637         unsigned long addr = __fix_to_virt(idx);
 638         pte_t *pte;
 639
 640         BUG_ON(idx <= FIX_HOLE || idx >= __end_of_fixed_addresses);
 641
 642         pte = fixmap_pte(addr);
 643
 644         if (pgprot_val(flags)) {
 645                 set_pte(pte, pfn_pte(phys >> PAGE_SHIFT, flags));
 646         } else {
 647                 pte_clear(&init_mm, addr, pte);
 648                 flush_tlb_kernel_range(addr, addr+PAGE_SIZE);
 649         }
 650 }
 651
 652 void *__init fixmap_remap_fdt(phys_addr_t dt_phys)
 653 {
 654         const u64 dt_virt_base = __fix_to_virt(FIX_FDT);
 655         pgprot_t prot = PAGE_KERNEL_RO;
 656         int size, offset;
 657         void *dt_virt;
 658
 659         /*
 660          * Check whether the physical FDT address is set and meets the minimum
 661          * alignment requirement. Since we are relying on MIN_FDT_ALIGN to be
 662          * at least 8 bytes so that we can always access the magic and size
 663          * fields of the FDT header after mapping the first chunk, double check
 664          * here if that is indeed the case.
 665          */
 666         BUILD_BUG_ON(MIN_FDT_ALIGN < 8);
 667         if (!dt_phys || dt_phys % MIN_FDT_ALIGN)
 668                 return NULL;
 669
 670         /*
 671          * Make sure that the FDT region can be mapped without the need to
 672          * allocate additional translation table pages, so that it is safe
 673          * to call create_mapping() this early.
 674          *
 675          * On 64k pages, the FDT will be mapped using PTEs, so we need to
 676          * be in the same PMD as the rest of the fixmap.
 677          * On 4k pages, we'll use section mappings for the FDT so we only
 678          * have to be in the same PUD.
 679          */
 680         BUILD_BUG_ON(dt_virt_base % SZ_2M);
 681
 682         BUILD_BUG_ON(__fix_to_virt(FIX_FDT_END) >> SWAPPER_TABLE_SHIFT !=
 683                      __fix_to_virt(FIX_BTMAP_BEGIN) >> SWAPPER_TABLE_SHIFT);
 684
 685         offset = dt_phys % SWAPPER_BLOCK_SIZE;
 686         dt_virt = (void *)dt_virt_base + offset;
 687
 688         /* map the first chunk so we can read the size from the header */
 689         create_mapping(round_down(dt_phys, SWAPPER_BLOCK_SIZE), dt_virt_base,
 690                        SWAPPER_BLOCK_SIZE, prot);
 691
 692         if (fdt_magic(dt_virt) != FDT_MAGIC)
 693                 return NULL;
 694
 695         size = fdt_totalsize(dt_virt);
 696         if (size > MAX_FDT_SIZE)
 697                 return NULL;
 698
 699         if (offset + size > SWAPPER_BLOCK_SIZE)
 700                 create_mapping(round_down(dt_phys, SWAPPER_BLOCK_SIZE), dt_virt_base,
 701                                round_up(offset + size, SWAPPER_BLOCK_SIZE), prot);
 702
 703         memblock_reserve(dt_phys, size);
 704
 705         return dt_virt;
 706 }