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Linux/arch/arm64/mm/mmu.c

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  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 }
710 

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