text: /*
   * Based on arch/arm/mm/mmu.c
   *
   * Copyright (C) 1995-2005 Russell King
   * Copyright (C) 2012 ARM Ltd.
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program.  If not, see <http://www.gnu.org/licenses/>.
   */
  
  #include <linux/cache.h>
  #include <linux/export.h>
  #include <linux/kernel.h>
  #include <linux/errno.h>
  #include <linux/init.h>
  #include <linux/ioport.h>
  #include <linux/kexec.h>
  #include <linux/libfdt.h>
  #include <linux/mman.h>
  #include <linux/nodemask.h>
  #include <linux/memblock.h>
  #include <linux/fs.h>
  #include <linux/io.h>
  #include <linux/mm.h>
  #include <linux/vmalloc.h>
  
  #include <asm/barrier.h>
  #include <asm/cputype.h>
  #include <asm/fixmap.h>
  #include <asm/kasan.h>
  #include <asm/kernel-pgtable.h>
  #include <asm/sections.h>
  #include <asm/setup.h>
  #include <asm/sizes.h>
  #include <asm/tlb.h>
  #include <asm/memblock.h>
  #include <asm/mmu_context.h>
  #include <asm/ptdump.h>
  #include <asm/tlbflush.h>
  
  #define NO_BLOCK_MAPPINGS	BIT(0)
  #define NO_CONT_MAPPINGS	BIT(1)
  
  u64 idmap_t0sz = TCR_T0SZ(VA_BITS);
  u64 idmap_ptrs_per_pgd = PTRS_PER_PGD;
  
  u64 kimage_voffset __ro_after_init;
  EXPORT_SYMBOL(kimage_voffset);
  
  /*
   * Empty_zero_page is a special page that is used for zero-initialized data
   * and COW.
   */
  unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss;
  EXPORT_SYMBOL(empty_zero_page);
  
  static pte_t bm_pte[PTRS_PER_PTE] __page_aligned_bss;
  static pmd_t bm_pmd[PTRS_PER_PMD] __page_aligned_bss __maybe_unused;
  static pud_t bm_pud[PTRS_PER_PUD] __page_aligned_bss __maybe_unused;
  
  static DEFINE_SPINLOCK(swapper_pgdir_lock);
  
  void set_swapper_pgd(pgd_t *pgdp, pgd_t pgd)
  {
  	pgd_t *fixmap_pgdp;
  
  	spin_lock(&swapper_pgdir_lock);
  	fixmap_pgdp = pgd_set_fixmap(__pa_symbol(pgdp));
  	WRITE_ONCE(*fixmap_pgdp, pgd);
  	/*
  	 * We need dsb(ishst) here to ensure the page-table-walker sees
  	 * our new entry before set_p?d() returns. The fixmap's
  	 * flush_tlb_kernel_range() via clear_fixmap() does this for us.
  	 */
  	pgd_clear_fixmap();
  	spin_unlock(&swapper_pgdir_lock);
  }
  
  pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
  			      unsigned long size, pgprot_t vma_prot)
  {
  	if (!pfn_valid(pfn))
  		return pgprot_noncached(vma_prot);
  	else if (file->f_flags & O_SYNC)
  		return pgprot_writecombine(vma_prot);
  	return vma_prot;
  }
  EXPORT_SYMBOL(phys_mem_access_prot);
  
  static phys_addr_t __init early_pgtable_alloc(void)
  {
  	phys_addr_t phys;
  	void *ptr;
  
  	phys = memblock_phys_alloc(PAGE_SIZE, PAGE_SIZE);
  
  	/*
  	 * The FIX_{PGD,PUD,PMD} slots may be in active use, but the FIX_PTE
  	 * slot will be free, so we can (ab)use the FIX_PTE slot to initialise
  	 * any level of table.
  	 */
  	ptr = pte_set_fixmap(phys);
  
  	memset(ptr, 0, PAGE_SIZE);
  
  	/*
  	 * Implicit barriers also ensure the zeroed page is visible to the page
  	 * table walker
  	 */
  	pte_clear_fixmap();
  
  	return phys;
  }
  
  static bool pgattr_change_is_safe(u64 old, u64 new)
  {
  	/*
  	 * The following mapping attributes may be updated in live
  	 * kernel mappings without the need for break-before-make.
  	 */
  	static const pteval_t mask = PTE_PXN | PTE_RDONLY | PTE_WRITE | PTE_NG;
  
  	/* creating or taking down mappings is always safe */
  	if (old == 0 || new == 0)
  		return true;
  
  	/* live contiguous mappings may not be manipulated at all */
  	if ((old | new) & PTE_CONT)
  		return false;
  
  	/* Transitioning from Non-Global to Global is unsafe */
  	if (old & ~new & PTE_NG)
  		return false;
  
  	return ((old ^ new) & ~mask) == 0;
  }
  
  static void init_pte(pmd_t *pmdp, unsigned long addr, unsigned long end,
  		     phys_addr_t phys, pgprot_t prot)
  {
  	pte_t *ptep;
  
  	ptep = pte_set_fixmap_offset(pmdp, addr);
  	do {
  		pte_t old_pte = READ_ONCE(*ptep);
  
  		set_pte(ptep, pfn_pte(__phys_to_pfn(phys), prot));
  
  		/*
  		 * After the PTE entry has been populated once, we
  		 * only allow updates to the permission attributes.
  		 */
  		BUG_ON(!pgattr_change_is_safe(pte_val(old_pte),
  					      READ_ONCE(pte_val(*ptep))));
  
  		phys += PAGE_SIZE;
  	} while (ptep++, addr += PAGE_SIZE, addr != end);
  
  	pte_clear_fixmap();
  }
  
  static void alloc_init_cont_pte(pmd_t *pmdp, unsigned long addr,
  				unsigned long end, phys_addr_t phys,
  				pgprot_t prot,
  				phys_addr_t (*pgtable_alloc)(void),
  				int flags)
  {
  	unsigned long next;
  	pmd_t pmd = READ_ONCE(*pmdp);
  
  	BUG_ON(pmd_sect(pmd));
  	if (pmd_none(pmd)) {
  		phys_addr_t pte_phys;
  		BUG_ON(!pgtable_alloc);
  		pte_phys = pgtable_alloc();
  		__pmd_populate(pmdp, pte_phys, PMD_TYPE_TABLE);
  		pmd = READ_ONCE(*pmdp);
  	}
  	BUG_ON(pmd_bad(pmd));
  
  	do {
  		pgprot_t __prot = prot;
  
  		next = pte_cont_addr_end(addr, end);
  
  		/* use a contiguous mapping if the range is suitably aligned */
  		if ((((addr | next | phys) & ~CONT_PTE_MASK) == 0) &&
  		    (flags & NO_CONT_MAPPINGS) == 0)
  			__prot = __pgprot(pgprot_val(prot) | PTE_CONT);
  
  		init_pte(pmdp, addr, next, phys, __prot);
  
  		phys += next - addr;
  	} while (addr = next, addr != end);
  }
  
  static void init_pmd(pud_t *pudp, unsigned long addr, unsigned long end,
  		     phys_addr_t phys, pgprot_t prot,
  		     phys_addr_t (*pgtable_alloc)(void), int flags)
  {
  	unsigned long next;
  	pmd_t *pmdp;
  
  	pmdp = pmd_set_fixmap_offset(pudp, addr);
  	do {
  		pmd_t old_pmd = READ_ONCE(*pmdp);
  
  		next = pmd_addr_end(addr, end);
  
  		/* try section mapping first */
  		if (((addr | next | phys) & ~SECTION_MASK) == 0 &&
  		    (flags & NO_BLOCK_MAPPINGS) == 0) {
  			pmd_set_huge(pmdp, phys, prot);
  
  			/*
  			 * After the PMD entry has been populated once, we
  			 * only allow updates to the permission attributes.
  			 */
  			BUG_ON(!pgattr_change_is_safe(pmd_val(old_pmd),
  						      READ_ONCE(pmd_val(*pmdp))));
  		} else {
  			alloc_init_cont_pte(pmdp, addr, next, phys, prot,
  					    pgtable_alloc, flags);
  
  			BUG_ON(pmd_val(old_pmd) != 0 &&
  			       pmd_val(old_pmd) != READ_ONCE(pmd_val(*pmdp)));
  		}
  		phys += next - addr;
  	} while (pmdp++, addr = next, addr != end);
  
  	pmd_clear_fixmap();
  }
  
  static void alloc_init_cont_pmd(pud_t *pudp, unsigned long addr,
  				unsigned long end, phys_addr_t phys,
  				pgprot_t prot,
  				phys_addr_t (*pgtable_alloc)(void), int flags)
  {
  	unsigned long next;
  	pud_t pud = READ_ONCE(*pudp);
  
  	/*
  	 * Check for initial section mappings in the pgd/pud.
  	 */
  	BUG_ON(pud_sect(pud));
  	if (pud_none(pud)) {
  		phys_addr_t pmd_phys;
  		BUG_ON(!pgtable_alloc);
  		pmd_phys = pgtable_alloc();
  		__pud_populate(pudp, pmd_phys, PUD_TYPE_TABLE);
  		pud = READ_ONCE(*pudp);
  	}
  	BUG_ON(pud_bad(pud));
  
  	do {
  		pgprot_t __prot = prot;
  
  		next = pmd_cont_addr_end(addr, end);
  
  		/* use a contiguous mapping if the range is suitably aligned */
  		if ((((addr | next | phys) & ~CONT_PMD_MASK) == 0) &&
  		    (flags & NO_CONT_MAPPINGS) == 0)
  			__prot = __pgprot(pgprot_val(prot) | PTE_CONT);
  
  		init_pmd(pudp, addr, next, phys, __prot, pgtable_alloc, flags);
  
  		phys += next - addr;
  	} while (addr = next, addr != end);
  }
  
  static inline bool use_1G_block(unsigned long addr, unsigned long next,
  			unsigned long phys)
  {
  	if (PAGE_SHIFT != 12)
  		return false;
  
  	if (((addr | next | phys) & ~PUD_MASK) != 0)
  		return false;
  
  	return true;
  }
  
  static void alloc_init_pud(pgd_t *pgdp, unsigned long addr, unsigned long end,
  			   phys_addr_t phys, pgprot_t prot,
  			   phys_addr_t (*pgtable_alloc)(void),
  			   int flags)
  {
  	unsigned long next;
  	pud_t *pudp;
  	pgd_t pgd = READ_ONCE(*pgdp);
  
  	if (pgd_none(pgd)) {
  		phys_addr_t pud_phys;
  		BUG_ON(!pgtable_alloc);
  		pud_phys = pgtable_alloc();
  		__pgd_populate(pgdp, pud_phys, PUD_TYPE_TABLE);
  		pgd = READ_ONCE(*pgdp);
  	}
  	BUG_ON(pgd_bad(pgd));
  
  	pudp = pud_set_fixmap_offset(pgdp, addr);
  	do {
  		pud_t old_pud = READ_ONCE(*pudp);
  
  		next = pud_addr_end(addr, end);
  
  		/*
  		 * For 4K granule only, attempt to put down a 1GB block
  		 */
  		if (use_1G_block(addr, next, phys) &&
  		    (flags & NO_BLOCK_MAPPINGS) == 0) {
  			pud_set_huge(pudp, phys, prot);
  
  			/*
  			 * After the PUD entry has been populated once, we
  			 * only allow updates to the permission attributes.
  			 */
  			BUG_ON(!pgattr_change_is_safe(pud_val(old_pud),
  						      READ_ONCE(pud_val(*pudp))));
  		} else {
  			alloc_init_cont_pmd(pudp, addr, next, phys, prot,
  					    pgtable_alloc, flags);
  
  			BUG_ON(pud_val(old_pud) != 0 &&
  			       pud_val(old_pud) != READ_ONCE(pud_val(*pudp)));
  		}
  		phys += next - addr;
  	} while (pudp++, addr = next, addr != end);
  
  	pud_clear_fixmap();
  }
  
  static void __create_pgd_mapping(pgd_t *pgdir, phys_addr_t phys,
  				 unsigned long virt, phys_addr_t size,
  				 pgprot_t prot,
  				 phys_addr_t (*pgtable_alloc)(void),
  				 int flags)
  {
  	unsigned long addr, length, end, next;
  	pgd_t *pgdp = pgd_offset_raw(pgdir, virt);
  
  	/*
  	 * If the virtual and physical address don't have the same offset
  	 * within a page, we cannot map the region as the caller expects.
  	 */
  	if (WARN_ON((phys ^ virt) & ~PAGE_MASK))
  		return;
  
  	phys &= PAGE_MASK;
  	addr = virt & PAGE_MASK;
  	length = PAGE_ALIGN(size + (virt & ~PAGE_MASK));
  
  	end = addr + length;
  	do {
  		next = pgd_addr_end(addr, end);
  		alloc_init_pud(pgdp, addr, next, phys, prot, pgtable_alloc,
  			       flags);
  		phys += next - addr;
  	} while (pgdp++, addr = next, addr != end);
  }
  
  static phys_addr_t pgd_pgtable_alloc(void)
  {
  	void *ptr = (void *)__get_free_page(PGALLOC_GFP);
  	if (!ptr || !pgtable_page_ctor(virt_to_page(ptr)))
  		BUG();
  
  	/* Ensure the zeroed page is visible to the page table walker */
  	dsb(ishst);
  	return __pa(ptr);
  }
  
  /*
   * This function can only be used to modify existing table entries,
   * without allocating new levels of table. Note that this permits the
   * creation of new section or page entries.
   */
  static void __init create_mapping_noalloc(phys_addr_t phys, unsigned long virt,
  				  phys_addr_t size, pgprot_t prot)
  {
  	if (virt < VMALLOC_START) {
  		pr_warn("BUG: not creating mapping for %pa at 0x%016lx - outside kernel range\n",
  			&phys, virt);
  		return;
  	}
  	__create_pgd_mapping(init_mm.pgd, phys, virt, size, prot, NULL,
  			     NO_CONT_MAPPINGS);
  }
  
  void __init create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
  			       unsigned long virt, phys_addr_t size,
  			       pgprot_t prot, bool page_mappings_only)
  {
  	int flags = 0;
  
  	BUG_ON(mm == &init_mm);
  
  	if (page_mappings_only)
  		flags = NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
  
  	__create_pgd_mapping(mm->pgd, phys, virt, size, prot,
  			     pgd_pgtable_alloc, flags);
  }
  
  static void update_mapping_prot(phys_addr_t phys, unsigned long virt,
  				phys_addr_t size, pgprot_t prot)
  {
  	if (virt < VMALLOC_START) {
  		pr_warn("BUG: not updating mapping for %pa at 0x%016lx - outside kernel range\n",
  			&phys, virt);
  		return;
  	}
  
  	__create_pgd_mapping(init_mm.pgd, phys, virt, size, prot, NULL,
  			     NO_CONT_MAPPINGS);
  
  	/* flush the TLBs after updating live kernel mappings */
  	flush_tlb_kernel_range(virt, virt + size);
  }
  
  static void __init __map_memblock(pgd_t *pgdp, phys_addr_t start,
  				  phys_addr_t end, pgprot_t prot, int flags)
  {
  	__create_pgd_mapping(pgdp, start, __phys_to_virt(start), end - start,
  			     prot, early_pgtable_alloc, flags);
  }
  
  void __init mark_linear_text_alias_ro(void)
  {
  	/*
  	 * Remove the write permissions from the linear alias of .text/.rodata
  	 */
  	update_mapping_prot(__pa_symbol(_text), (unsigned long)lm_alias(_text),
  			    (unsigned long)__init_begin - (unsigned long)_text,
  			    PAGE_KERNEL_RO);
  }
  
  static void __init map_mem(pgd_t *pgdp)
  {
  	phys_addr_t kernel_start = __pa_symbol(_text);
  	phys_addr_t kernel_end = __pa_symbol(__init_begin);
  	struct memblock_region *reg;
  	int flags = 0;
  
  	if (debug_pagealloc_enabled())
  		flags = NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
  
  	/*
  	 * Take care not to create a writable alias for the
  	 * read-only text and rodata sections of the kernel image.
  	 * So temporarily mark them as NOMAP to skip mappings in
  	 * the following for-loop
  	 */
  	memblock_mark_nomap(kernel_start, kernel_end - kernel_start);
  #ifdef CONFIG_KEXEC_CORE
  	if (crashk_res.end)
  		memblock_mark_nomap(crashk_res.start,
  				    resource_size(&crashk_res));
  #endif
  
  	/* map all the memory banks */
  	for_each_memblock(memory, reg) {
  		phys_addr_t start = reg->base;
  		phys_addr_t end = start + reg->size;
  
  		if (start >= end)
  			break;
  		if (memblock_is_nomap(reg))
  			continue;
  
  		__map_memblock(pgdp, start, end, PAGE_KERNEL, flags);
  	}
  
  	/*
  	 * Map the linear alias of the [_text, __init_begin) interval
  	 * as non-executable now, and remove the write permission in
  	 * mark_linear_text_alias_ro() below (which will be called after
  	 * alternative patching has completed). This makes the contents
  	 * of the region accessible to subsystems such as hibernate,
  	 * but protects it from inadvertent modification or execution.
  	 * Note that contiguous mappings cannot be remapped in this way,
  	 * so we should avoid them here.
  	 */
  	__map_memblock(pgdp, kernel_start, kernel_end,
  		       PAGE_KERNEL, NO_CONT_MAPPINGS);
  	memblock_clear_nomap(kernel_start, kernel_end - kernel_start);
  
  #ifdef CONFIG_KEXEC_CORE
  	/*
  	 * Use page-level mappings here so that we can shrink the region
  	 * in page granularity and put back unused memory to buddy system
  	 * through /sys/kernel/kexec_crash_size interface.
  	 */
  	if (crashk_res.end) {
  		__map_memblock(pgdp, crashk_res.start, crashk_res.end + 1,
  			       PAGE_KERNEL,
  			       NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS);
  		memblock_clear_nomap(crashk_res.start,
  				     resource_size(&crashk_res));
  	}
  #endif
  }
  
  void mark_rodata_ro(void)
  {
  	unsigned long section_size;
  
  	/*
  	 * mark .rodata as read only. Use __init_begin rather than __end_rodata
  	 * to cover NOTES and EXCEPTION_TABLE.
  	 */
  	section_size = (unsigned long)__init_begin - (unsigned long)__start_rodata;
  	update_mapping_prot(__pa_symbol(__start_rodata), (unsigned long)__start_rodata,
  			    section_size, PAGE_KERNEL_RO);
  
  	debug_checkwx();
  }
  
  static void __init map_kernel_segment(pgd_t *pgdp, void *va_start, void *va_end,
  				      pgprot_t prot, struct vm_struct *vma,
  				      int flags, unsigned long vm_flags)
  {
  	phys_addr_t pa_start = __pa_symbol(va_start);
  	unsigned long size = va_end - va_start;
  
  	BUG_ON(!PAGE_ALIGNED(pa_start));
  	BUG_ON(!PAGE_ALIGNED(size));
  
  	__create_pgd_mapping(pgdp, pa_start, (unsigned long)va_start, size, prot,
  			     early_pgtable_alloc, flags);
  
  	if (!(vm_flags & VM_NO_GUARD))
  		size += PAGE_SIZE;
  
  	vma->addr	= va_start;
  	vma->phys_addr	= pa_start;
  	vma->size	= size;
  	vma->flags	= VM_MAP | vm_flags;
  	vma->caller	= __builtin_return_address(0);
  
  	vm_area_add_early(vma);
  }
  
  static int __init parse_rodata(char *arg)
  {
  	return strtobool(arg, &rodata_enabled);
  }
  early_param("rodata", parse_rodata);
  
  #ifdef CONFIG_UNMAP_KERNEL_AT_EL0
  static int __init map_entry_trampoline(void)
  {
  	pgprot_t prot = rodata_enabled ? PAGE_KERNEL_ROX : PAGE_KERNEL_EXEC;
  	phys_addr_t pa_start = __pa_symbol(__entry_tramp_text_start);
  
  	/* The trampoline is always mapped and can therefore be global */
  	pgprot_val(prot) &= ~PTE_NG;
  
  	/* Map only the text into the trampoline page table */
  	memset(tramp_pg_dir, 0, PGD_SIZE);
  	__create_pgd_mapping(tramp_pg_dir, pa_start, TRAMP_VALIAS, PAGE_SIZE,
  			     prot, pgd_pgtable_alloc, 0);
  
  	/* Map both the text and data into the kernel page table */
  	__set_fixmap(FIX_ENTRY_TRAMP_TEXT, pa_start, prot);
  	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
  		extern char __entry_tramp_data_start[];
  
  		__set_fixmap(FIX_ENTRY_TRAMP_DATA,
  			     __pa_symbol(__entry_tramp_data_start),
  			     PAGE_KERNEL_RO);
  	}
  
  	return 0;
  }
  core_initcall(map_entry_trampoline);
  #endif
  
  /*
   * Create fine-grained mappings for the kernel.
   */
  static void __init map_kernel(pgd_t *pgdp)
  {
  	static struct vm_struct vmlinux_text, vmlinux_rodata, vmlinux_inittext,
  				vmlinux_initdata, vmlinux_data;
  
  	/*
  	 * External debuggers may need to write directly to the text
  	 * mapping to install SW breakpoints. Allow this (only) when
  	 * explicitly requested with rodata=off.
  	 */
  	pgprot_t text_prot = rodata_enabled ? PAGE_KERNEL_ROX : PAGE_KERNEL_EXEC;
  
  	/*
  	 * Only rodata will be remapped with different permissions later on,
  	 * all other segments are allowed to use contiguous mappings.
  	 */
  	map_kernel_segment(pgdp, _text, _etext, text_prot, &vmlinux_text, 0,
  			   VM_NO_GUARD);
  	map_kernel_segment(pgdp, __start_rodata, __inittext_begin, PAGE_KERNEL,
  			   &vmlinux_rodata, NO_CONT_MAPPINGS, VM_NO_GUARD);
  	map_kernel_segment(pgdp, __inittext_begin, __inittext_end, text_prot,
  			   &vmlinux_inittext, 0, VM_NO_GUARD);
  	map_kernel_segment(pgdp, __initdata_begin, __initdata_end, PAGE_KERNEL,
  			   &vmlinux_initdata, 0, VM_NO_GUARD);
  	map_kernel_segment(pgdp, _data, _end, PAGE_KERNEL, &vmlinux_data, 0, 0);
  
  	if (!READ_ONCE(pgd_val(*pgd_offset_raw(pgdp, FIXADDR_START)))) {
  		/*
  		 * The fixmap falls in a separate pgd to the kernel, and doesn't
  		 * live in the carveout for the swapper_pg_dir. We can simply
  		 * re-use the existing dir for the fixmap.
  		 */
  		set_pgd(pgd_offset_raw(pgdp, FIXADDR_START),
  			READ_ONCE(*pgd_offset_k(FIXADDR_START)));
  	} else if (CONFIG_PGTABLE_LEVELS > 3) {
  		/*
  		 * The fixmap shares its top level pgd entry with the kernel
  		 * mapping. This can really only occur when we are running
  		 * with 16k/4 levels, so we can simply reuse the pud level
  		 * entry instead.
  		 */
  		BUG_ON(!IS_ENABLED(CONFIG_ARM64_16K_PAGES));
  		pud_populate(&init_mm,
  			     pud_set_fixmap_offset(pgdp, FIXADDR_START),
  			     lm_alias(bm_pmd));
  		pud_clear_fixmap();
  	} else {
  		BUG();
  	}
  
  	kasan_copy_shadow(pgdp);
  }
  
  /*
   * paging_init() sets up the page tables, initialises the zone memory
   * maps and sets up the zero page.
   */
  void __init paging_init(void)
  {
  	pgd_t *pgdp = pgd_set_fixmap(__pa_symbol(swapper_pg_dir));
  
  	map_kernel(pgdp);
  	map_mem(pgdp);
  
  	pgd_clear_fixmap();
  
  	cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
  	init_mm.pgd = swapper_pg_dir;
  
  	memblock_free(__pa_symbol(init_pg_dir),
  		      __pa_symbol(init_pg_end) - __pa_symbol(init_pg_dir));
  
  	memblock_allow_resize();
  }
  
  /*
   * Check whether a kernel address is valid (derived from arch/x86/).
   */
  int kern_addr_valid(unsigned long addr)
  {
  	pgd_t *pgdp;
  	pud_t *pudp, pud;
  	pmd_t *pmdp, pmd;
  	pte_t *ptep, pte;
  
  	if ((((long)addr) >> VA_BITS) != -1UL)
  		return 0;
  
  	pgdp = pgd_offset_k(addr);
  	if (pgd_none(READ_ONCE(*pgdp)))
  		return 0;
  
  	pudp = pud_offset(pgdp, addr);
  	pud = READ_ONCE(*pudp);
  	if (pud_none(pud))
  		return 0;
  
  	if (pud_sect(pud))
  		return pfn_valid(pud_pfn(pud));
  
  	pmdp = pmd_offset(pudp, addr);
  	pmd = READ_ONCE(*pmdp);
  	if (pmd_none(pmd))
  		return 0;
  
  	if (pmd_sect(pmd))
  		return pfn_valid(pmd_pfn(pmd));
  
  	ptep = pte_offset_kernel(pmdp, addr);
  	pte = READ_ONCE(*ptep);
  	if (pte_none(pte))
  		return 0;
  
  	return pfn_valid(pte_pfn(pte));
  }
  #ifdef CONFIG_SPARSEMEM_VMEMMAP
  #if !ARM64_SWAPPER_USES_SECTION_MAPS
  int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
  		struct vmem_altmap *altmap)
  {
  	return vmemmap_populate_basepages(start, end, node);
  }
  #else	/* !ARM64_SWAPPER_USES_SECTION_MAPS */
  int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
  		struct vmem_altmap *altmap)
  {
  	unsigned long addr = start;
  	unsigned long next;
  	pgd_t *pgdp;
  	pud_t *pudp;
  	pmd_t *pmdp;
  
  	do {
  		next = pmd_addr_end(addr, end);
  
  		pgdp = vmemmap_pgd_populate(addr, node);
  		if (!pgdp)
  			return -ENOMEM;
  
  		pudp = vmemmap_pud_populate(pgdp, addr, node);
  		if (!pudp)
  			return -ENOMEM;
  
  		pmdp = pmd_offset(pudp, addr);
  		if (pmd_none(READ_ONCE(*pmdp))) {
  			void *p = NULL;
  
  			p = vmemmap_alloc_block_buf(PMD_SIZE, node);
  			if (!p)
  				return -ENOMEM;
  
  			pmd_set_huge(pmdp, __pa(p), __pgprot(PROT_SECT_NORMAL));
  		} else
  			vmemmap_verify((pte_t *)pmdp, node, addr, next);
  	} while (addr = next, addr != end);
  
  	return 0;
  }
  #endif	/* CONFIG_ARM64_64K_PAGES */
  void vmemmap_free(unsigned long start, unsigned long end,
  		struct vmem_altmap *altmap)
  {
  }
  #endif	/* CONFIG_SPARSEMEM_VMEMMAP */
  
  static inline pud_t * fixmap_pud(unsigned long addr)
  {
  	pgd_t *pgdp = pgd_offset_k(addr);
  	pgd_t pgd = READ_ONCE(*pgdp);
  
  	BUG_ON(pgd_none(pgd) || pgd_bad(pgd));
  
  	return pud_offset_kimg(pgdp, addr);
  }
  
  static inline pmd_t * fixmap_pmd(unsigned long addr)
  {
  	pud_t *pudp = fixmap_pud(addr);
  	pud_t pud = READ_ONCE(*pudp);
  
  	BUG_ON(pud_none(pud) || pud_bad(pud));
  
  	return pmd_offset_kimg(pudp, addr);
  }
  
  static inline pte_t * fixmap_pte(unsigned long addr)
  {
  	return &bm_pte[pte_index(addr)];
  }
  
  /*
   * The p*d_populate functions call virt_to_phys implicitly so they can't be used
   * directly on kernel symbols (bm_p*d). This function is called too early to use
   * lm_alias so __p*d_populate functions must be used to populate with the
   * physical address from __pa_symbol.
   */
  void __init early_fixmap_init(void)
  {
  	pgd_t *pgdp, pgd;
  	pud_t *pudp;
  	pmd_t *pmdp;
  	unsigned long addr = FIXADDR_START;
  
  	pgdp = pgd_offset_k(addr);
  	pgd = READ_ONCE(*pgdp);
  	if (CONFIG_PGTABLE_LEVELS > 3 &&
  	    !(pgd_none(pgd) || pgd_page_paddr(pgd) == __pa_symbol(bm_pud))) {
  		/*
  		 * We only end up here if the kernel mapping and the fixmap
  		 * share the top level pgd entry, which should only happen on
  		 * 16k/4 levels configurations.
  		 */
  		BUG_ON(!IS_ENABLED(CONFIG_ARM64_16K_PAGES));
  		pudp = pud_offset_kimg(pgdp, addr);
  	} else {
  		if (pgd_none(pgd))
  			__pgd_populate(pgdp, __pa_symbol(bm_pud), PUD_TYPE_TABLE);
  		pudp = fixmap_pud(addr);
  	}
  	if (pud_none(READ_ONCE(*pudp)))
  		__pud_populate(pudp, __pa_symbol(bm_pmd), PMD_TYPE_TABLE);
  	pmdp = fixmap_pmd(addr);
  	__pmd_populate(pmdp, __pa_symbol(bm_pte), PMD_TYPE_TABLE);
  
  	/*
  	 * The boot-ioremap range spans multiple pmds, for which
  	 * we are not prepared:
  	 */
  	BUILD_BUG_ON((__fix_to_virt(FIX_BTMAP_BEGIN) >> PMD_SHIFT)
  		     != (__fix_to_virt(FIX_BTMAP_END) >> PMD_SHIFT));
  
  	if ((pmdp != fixmap_pmd(fix_to_virt(FIX_BTMAP_BEGIN)))
  	     || pmdp != fixmap_pmd(fix_to_virt(FIX_BTMAP_END))) {
  		WARN_ON(1);
  		pr_warn("pmdp %p != %p, %p\n",
  			pmdp, fixmap_pmd(fix_to_virt(FIX_BTMAP_BEGIN)),
  			fixmap_pmd(fix_to_virt(FIX_BTMAP_END)));
  		pr_warn("fix_to_virt(FIX_BTMAP_BEGIN): %08lx\n",
  			fix_to_virt(FIX_BTMAP_BEGIN));
  		pr_warn("fix_to_virt(FIX_BTMAP_END):   %08lx\n",
  			fix_to_virt(FIX_BTMAP_END));
  
  		pr_warn("FIX_BTMAP_END:       %d\n", FIX_BTMAP_END);
  		pr_warn("FIX_BTMAP_BEGIN:     %d\n", FIX_BTMAP_BEGIN);
  	}
  }
  
  /*
   * Unusually, this is also called in IRQ context (ghes_iounmap_irq) so if we
   * ever need to use IPIs for TLB broadcasting, then we're in trouble here.
   */
  void __set_fixmap(enum fixed_addresses idx,
  			       phys_addr_t phys, pgprot_t flags)
  {
  	unsigned long addr = __fix_to_virt(idx);
  	pte_t *ptep;
  
  	BUG_ON(idx <= FIX_HOLE || idx >= __end_of_fixed_addresses);
  
  	ptep = fixmap_pte(addr);
  
  	if (pgprot_val(flags)) {
  		set_pte(ptep, pfn_pte(phys >> PAGE_SHIFT, flags));
  	} else {
  		pte_clear(&init_mm, addr, ptep);
  		flush_tlb_kernel_range(addr, addr+PAGE_SIZE);
  	}
  }
  
  void *__init __fixmap_remap_fdt(phys_addr_t dt_phys, int *size, pgprot_t prot)
  {
  	const u64 dt_virt_base = __fix_to_virt(FIX_FDT);
  	int offset;
  	void *dt_virt;
  
  	/*
  	 * Check whether the physical FDT address is set and meets the minimum
  	 * alignment requirement. Since we are relying on MIN_FDT_ALIGN to be
  	 * at least 8 bytes so that we can always access the magic and size
  	 * fields of the FDT header after mapping the first chunk, double check
  	 * here if that is indeed the case.
  	 */
  	BUILD_BUG_ON(MIN_FDT_ALIGN < 8);
  	if (!dt_phys || dt_phys % MIN_FDT_ALIGN)
  		return NULL;
  
  	/*
  	 * Make sure that the FDT region can be mapped without the need to
  	 * allocate additional translation table pages, so that it is safe
  	 * to call create_mapping_noalloc() this early.
  	 *
  	 * On 64k pages, the FDT will be mapped using PTEs, so we need to
  	 * be in the same PMD as the rest of the fixmap.
  	 * On 4k pages, we'll use section mappings for the FDT so we only
  	 * have to be in the same PUD.
  	 */
  	BUILD_BUG_ON(dt_virt_base % SZ_2M);
  
  	BUILD_BUG_ON(__fix_to_virt(FIX_FDT_END) >> SWAPPER_TABLE_SHIFT !=
  		     __fix_to_virt(FIX_BTMAP_BEGIN) >> SWAPPER_TABLE_SHIFT);
  
  	offset = dt_phys % SWAPPER_BLOCK_SIZE;
  	dt_virt = (void *)dt_virt_base + offset;
  
  	/* map the first chunk so we can read the size from the header */
  	create_mapping_noalloc(round_down(dt_phys, SWAPPER_BLOCK_SIZE),
  			dt_virt_base, SWAPPER_BLOCK_SIZE, prot);
  
  	if (fdt_magic(dt_virt) != FDT_MAGIC)
  		return NULL;
  
  	*size = fdt_totalsize(dt_virt);
  	if (*size > MAX_FDT_SIZE)
  		return NULL;
  
  	if (offset + *size > SWAPPER_BLOCK_SIZE)
  		create_mapping_noalloc(round_down(dt_phys, SWAPPER_BLOCK_SIZE), dt_virt_base,
  			       round_up(offset + *size, SWAPPER_BLOCK_SIZE), prot);
  
  	return dt_virt;
  }
  
  void *__init fixmap_remap_fdt(phys_addr_t dt_phys)
  {
  	void *dt_virt;
  	int size;
  
  	dt_virt = __fixmap_remap_fdt(dt_phys, &size, PAGE_KERNEL_RO);
  	if (!dt_virt)
  		return NULL;
  
  	memblock_reserve(dt_phys, size);
  	return dt_virt;
  }
  
  int __init arch_ioremap_pud_supported(void)
  {
  	/* only 4k granule supports level 1 block mappings */
  	return IS_ENABLED(CONFIG_ARM64_4K_PAGES);
  }
  
  int __init arch_ioremap_pmd_supported(void)
  {
  	return 1;
  }
  
  int pud_set_huge(pud_t *pudp, phys_addr_t phys, pgprot_t prot)
  {
  	pgprot_t sect_prot = __pgprot(PUD_TYPE_SECT |
  					pgprot_val(mk_sect_prot(prot)));
  	pud_t new_pud = pfn_pud(__phys_to_pfn(phys), sect_prot);
  
  	/* Only allow permission changes for now */
  	if (!pgattr_change_is_safe(READ_ONCE(pud_val(*pudp)),
  				   pud_val(new_pud)))
  		return 0;
  
  	BUG_ON(phys & ~PUD_MASK);
  	set_pud(pudp, new_pud);
  	return 1;
  }
  
  int pmd_set_huge(pmd_t *pmdp, phys_addr_t phys, pgprot_t prot)
  {
  	pgprot_t sect_prot = __pgprot(PMD_TYPE_SECT |
  					pgprot_val(mk_sect_prot(prot)));
  	pmd_t new_pmd = pfn_pmd(__phys_to_pfn(phys), sect_prot);
  
  	/* Only allow permission changes for now */
  	if (!pgattr_change_is_safe(READ_ONCE(pmd_val(*pmdp)),
  				   pmd_val(new_pmd)))
  		return 0;
  
  	BUG_ON(phys & ~PMD_MASK);
  	set_pmd(pmdp, new_pmd);
  	return 1;
  }
  
  int pud_clear_huge(pud_t *pudp)
  {
  	if (!pud_sect(READ_ONCE(*pudp)))
  		return 0;
  	pud_clear(pudp);
  	return 1;
  }
  
  int pmd_clear_huge(pmd_t *pmdp)
  {
  	if (!pmd_sect(READ_ONCE(*pmdp)))
  		return 0;
  	pmd_clear(pmdp);
  	return 1;
  }
  
  int pmd_free_pte_page(pmd_t *pmdp, unsigned long addr)
  {
  	pte_t *table;
  	pmd_t pmd;
  
  	pmd = READ_ONCE(*pmdp);
  
  	if (!pmd_present(pmd))
  		return 1;
  	if (!pmd_table(pmd)) {
  		VM_WARN_ON(!pmd_table(pmd));
  		return 1;
  	}
  
  	table = pte_offset_kernel(pmdp, addr);
  	pmd_clear(pmdp);
  	__flush_tlb_kernel_pgtable(addr);
  	pte_free_kernel(NULL, table);
  	return 1;
  }
  
  int pud_free_pmd_page(pud_t *pudp, unsigned long addr)
  {
  	pmd_t *table;
  	pmd_t *pmdp;
  	pud_t pud;
  	unsigned long next, end;
  
  	pud = READ_ONCE(*pudp);
  
  	if (!pud_present(pud))
  		return 1;
  	if (!pud_table(pud)) {
  		VM_WARN_ON(!pud_table(pud));
  		return 1;
  	}
  
  	table = pmd_offset(pudp, addr);
  	pmdp = table;
  	next = addr;
  	end = addr + PUD_SIZE;
  	do {
  		pmd_free_pte_page(pmdp, next);
  	} while (pmdp++, next += PMD_SIZE, next != end);
  
  	pud_clear(pudp);
  	__flush_tlb_kernel_pgtable(addr);
  	pmd_free(NULL, table);
  	return 1;
  }
  