text: // SPDX-License-Identifier: GPL-2.0-only
  /*
   * arch/arm64/mm/hugetlbpage.c
   *
   * Copyright (C) 2013 Linaro Ltd.
   *
   * Based on arch/x86/mm/hugetlbpage.c.
   */
  
  #include <linux/init.h>
  #include <linux/fs.h>
  #include <linux/mm.h>
  #include <linux/hugetlb.h>
  #include <linux/pagemap.h>
  #include <linux/err.h>
  #include <linux/sysctl.h>
  #include <asm/mman.h>
  #include <asm/tlb.h>
  #include <asm/tlbflush.h>
  
  /*
   * HugeTLB Support Matrix
   *
   * ---------------------------------------------------
   * | Page Size | CONT PTE |  PMD  | CONT PMD |  PUD  |
   * ---------------------------------------------------
   * |     4K    |   64K    |   2M  |    32M   |   1G  |
   * |    16K    |    2M    |  32M  |     1G   |       |
   * |    64K    |    2M    | 512M  |    16G   |       |
   * ---------------------------------------------------
   */
  
  /*
   * Reserve CMA areas for the largest supported gigantic
   * huge page when requested. Any other smaller gigantic
   * huge pages could still be served from those areas.
   */
  #ifdef CONFIG_CMA
  void __init arm64_hugetlb_cma_reserve(void)
  {
  	int order;
  
  #ifdef CONFIG_ARM64_4K_PAGES
  	order = PUD_SHIFT - PAGE_SHIFT;
  #else
  	order = CONT_PMD_SHIFT - PAGE_SHIFT;
  #endif
  	/*
  	 * HugeTLB CMA reservation is required for gigantic
  	 * huge pages which could not be allocated via the
  	 * page allocator. Just warn if there is any change
  	 * breaking this assumption.
  	 */
  	WARN_ON(order <= MAX_ORDER);
  	hugetlb_cma_reserve(order);
  }
  #endif /* CONFIG_CMA */
  
  #ifdef CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION
  bool arch_hugetlb_migration_supported(struct hstate *h)
  {
  	size_t pagesize = huge_page_size(h);
  
  	switch (pagesize) {
  #ifdef CONFIG_ARM64_4K_PAGES
  	case PUD_SIZE:
  #endif
  	case PMD_SIZE:
  	case CONT_PMD_SIZE:
  	case CONT_PTE_SIZE:
  		return true;
  	}
  	pr_warn("%s: unrecognized huge page size 0x%lx\n",
  			__func__, pagesize);
  	return false;
  }
  #endif
  
  int pmd_huge(pmd_t pmd)
  {
  	return pmd_val(pmd) && !(pmd_val(pmd) & PMD_TABLE_BIT);
  }
  
  int pud_huge(pud_t pud)
  {
  #ifndef __PAGETABLE_PMD_FOLDED
  	return pud_val(pud) && !(pud_val(pud) & PUD_TABLE_BIT);
  #else
  	return 0;
  #endif
  }
  
  /*
   * Select all bits except the pfn
   */
  static inline pgprot_t pte_pgprot(pte_t pte)
  {
  	unsigned long pfn = pte_pfn(pte);
  
  	return __pgprot(pte_val(pfn_pte(pfn, __pgprot(0))) ^ pte_val(pte));
  }
  
  static int find_num_contig(struct mm_struct *mm, unsigned long addr,
  			   pte_t *ptep, size_t *pgsize)
  {
  	pgd_t *pgdp = pgd_offset(mm, addr);
  	p4d_t *p4dp;
  	pud_t *pudp;
  	pmd_t *pmdp;
  
  	*pgsize = PAGE_SIZE;
  	p4dp = p4d_offset(pgdp, addr);
  	pudp = pud_offset(p4dp, addr);
  	pmdp = pmd_offset(pudp, addr);
  	if ((pte_t *)pmdp == ptep) {
  		*pgsize = PMD_SIZE;
  		return CONT_PMDS;
  	}
  	return CONT_PTES;
  }
  
  static inline int num_contig_ptes(unsigned long size, size_t *pgsize)
  {
  	int contig_ptes = 0;
  
  	*pgsize = size;
  
  	switch (size) {
  #ifdef CONFIG_ARM64_4K_PAGES
  	case PUD_SIZE:
  #endif
  	case PMD_SIZE:
  		contig_ptes = 1;
  		break;
  	case CONT_PMD_SIZE:
  		*pgsize = PMD_SIZE;
  		contig_ptes = CONT_PMDS;
  		break;
  	case CONT_PTE_SIZE:
  		*pgsize = PAGE_SIZE;
  		contig_ptes = CONT_PTES;
  		break;
  	}
  
  	return contig_ptes;
  }
  
  /*
   * Changing some bits of contiguous entries requires us to follow a
   * Break-Before-Make approach, breaking the whole contiguous set
   * before we can change any entries. See ARM DDI 0487A.k_iss10775,
   * "Misprogramming of the Contiguous bit", page D4-1762.
   *
   * This helper performs the break step.
   */
  static pte_t get_clear_flush(struct mm_struct *mm,
  			     unsigned long addr,
  			     pte_t *ptep,
  			     unsigned long pgsize,
  			     unsigned long ncontig)
  {
  	pte_t orig_pte = huge_ptep_get(ptep);
  	bool valid = pte_valid(orig_pte);
  	unsigned long i, saddr = addr;
  
  	for (i = 0; i < ncontig; i++, addr += pgsize, ptep++) {
  		pte_t pte = ptep_get_and_clear(mm, addr, ptep);
  
  		/*
  		 * If HW_AFDBM is enabled, then the HW could turn on
  		 * the dirty or accessed bit for any page in the set,
  		 * so check them all.
  		 */
  		if (pte_dirty(pte))
  			orig_pte = pte_mkdirty(orig_pte);
  
  		if (pte_young(pte))
  			orig_pte = pte_mkyoung(orig_pte);
  	}
  
  	if (valid) {
  		struct vm_area_struct vma = TLB_FLUSH_VMA(mm, 0);
  		flush_tlb_range(&vma, saddr, addr);
  	}
  	return orig_pte;
  }
  
  /*
   * Changing some bits of contiguous entries requires us to follow a
   * Break-Before-Make approach, breaking the whole contiguous set
   * before we can change any entries. See ARM DDI 0487A.k_iss10775,
   * "Misprogramming of the Contiguous bit", page D4-1762.
   *
   * This helper performs the break step for use cases where the
   * original pte is not needed.
   */
  static void clear_flush(struct mm_struct *mm,
  			     unsigned long addr,
  			     pte_t *ptep,
  			     unsigned long pgsize,
  			     unsigned long ncontig)
  {
  	struct vm_area_struct vma = TLB_FLUSH_VMA(mm, 0);
  	unsigned long i, saddr = addr;
  
  	for (i = 0; i < ncontig; i++, addr += pgsize, ptep++)
  		pte_clear(mm, addr, ptep);
  
  	flush_tlb_range(&vma, saddr, addr);
  }
  
  void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
  			    pte_t *ptep, pte_t pte)
  {
  	size_t pgsize;
  	int i;
  	int ncontig;
  	unsigned long pfn, dpfn;
  	pgprot_t hugeprot;
  
  	/*
  	 * Code needs to be expanded to handle huge swap and migration
  	 * entries. Needed for HUGETLB and MEMORY_FAILURE.
  	 */
  	WARN_ON(!pte_present(pte));
  
  	if (!pte_cont(pte)) {
  		set_pte_at(mm, addr, ptep, pte);
  		return;
  	}
  
  	ncontig = find_num_contig(mm, addr, ptep, &pgsize);
  	pfn = pte_pfn(pte);
  	dpfn = pgsize >> PAGE_SHIFT;
  	hugeprot = pte_pgprot(pte);
  
  	clear_flush(mm, addr, ptep, pgsize, ncontig);
  
  	for (i = 0; i < ncontig; i++, ptep++, addr += pgsize, pfn += dpfn)
  		set_pte_at(mm, addr, ptep, pfn_pte(pfn, hugeprot));
  }
  
  void set_huge_swap_pte_at(struct mm_struct *mm, unsigned long addr,
  			  pte_t *ptep, pte_t pte, unsigned long sz)
  {
  	int i, ncontig;
  	size_t pgsize;
  
  	ncontig = num_contig_ptes(sz, &pgsize);
  
  	for (i = 0; i < ncontig; i++, ptep++)
  		set_pte(ptep, pte);
  }
  
  pte_t *huge_pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma,
  		      unsigned long addr, unsigned long sz)
  {
  	pgd_t *pgdp;
  	p4d_t *p4dp;
  	pud_t *pudp;
  	pmd_t *pmdp;
  	pte_t *ptep = NULL;
  
  	pgdp = pgd_offset(mm, addr);
  	p4dp = p4d_offset(pgdp, addr);
  	pudp = pud_alloc(mm, p4dp, addr);
  	if (!pudp)
  		return NULL;
  
  	if (sz == PUD_SIZE) {
  		ptep = (pte_t *)pudp;
  	} else if (sz == (CONT_PTE_SIZE)) {
  		pmdp = pmd_alloc(mm, pudp, addr);
  		if (!pmdp)
  			return NULL;
  
  		WARN_ON(addr & (sz - 1));
  		/*
  		 * Note that if this code were ever ported to the
  		 * 32-bit arm platform then it will cause trouble in
  		 * the case where CONFIG_HIGHPTE is set, since there
  		 * will be no pte_unmap() to correspond with this
  		 * pte_alloc_map().
  		 */
  		ptep = pte_alloc_map(mm, pmdp, addr);
  	} else if (sz == PMD_SIZE) {
  		if (want_pmd_share(vma, addr) && pud_none(READ_ONCE(*pudp)))
  			ptep = huge_pmd_share(mm, vma, addr, pudp);
  		else
  			ptep = (pte_t *)pmd_alloc(mm, pudp, addr);
  	} else if (sz == (CONT_PMD_SIZE)) {
  		pmdp = pmd_alloc(mm, pudp, addr);
  		WARN_ON(addr & (sz - 1));
  		return (pte_t *)pmdp;
  	}
  
  	return ptep;
  }
  
  pte_t *huge_pte_offset(struct mm_struct *mm,
  		       unsigned long addr, unsigned long sz)
  {
  	pgd_t *pgdp;
  	p4d_t *p4dp;
  	pud_t *pudp, pud;
  	pmd_t *pmdp, pmd;
  
  	pgdp = pgd_offset(mm, addr);
  	if (!pgd_present(READ_ONCE(*pgdp)))
  		return NULL;
  
  	p4dp = p4d_offset(pgdp, addr);
  	if (!p4d_present(READ_ONCE(*p4dp)))
  		return NULL;
  
  	pudp = pud_offset(p4dp, addr);
  	pud = READ_ONCE(*pudp);
  	if (sz != PUD_SIZE && pud_none(pud))
  		return NULL;
  	/* hugepage or swap? */
  	if (pud_huge(pud) || !pud_present(pud))
  		return (pte_t *)pudp;
  	/* table; check the next level */
  
  	if (sz == CONT_PMD_SIZE)
  		addr &= CONT_PMD_MASK;
  
  	pmdp = pmd_offset(pudp, addr);
  	pmd = READ_ONCE(*pmdp);
  	if (!(sz == PMD_SIZE || sz == CONT_PMD_SIZE) &&
  	    pmd_none(pmd))
  		return NULL;
  	if (pmd_huge(pmd) || !pmd_present(pmd))
  		return (pte_t *)pmdp;
  
  	if (sz == CONT_PTE_SIZE)
  		return pte_offset_kernel(pmdp, (addr & CONT_PTE_MASK));
  
  	return NULL;
  }
  
  pte_t arch_make_huge_pte(pte_t entry, unsigned int shift, vm_flags_t flags)
  {
  	size_t pagesize = 1UL << shift;
  
  	if (pagesize == CONT_PTE_SIZE) {
  		entry = pte_mkcont(entry);
  	} else if (pagesize == CONT_PMD_SIZE) {
  		entry = pmd_pte(pmd_mkcont(pte_pmd(entry)));
  	} else if (pagesize != PUD_SIZE && pagesize != PMD_SIZE) {
  		pr_warn("%s: unrecognized huge page size 0x%lx\n",
  			__func__, pagesize);
  	}
  	return entry;
  }
  
  void huge_pte_clear(struct mm_struct *mm, unsigned long addr,
  		    pte_t *ptep, unsigned long sz)
  {
  	int i, ncontig;
  	size_t pgsize;
  
  	ncontig = num_contig_ptes(sz, &pgsize);
  
  	for (i = 0; i < ncontig; i++, addr += pgsize, ptep++)
  		pte_clear(mm, addr, ptep);
  }
  
  pte_t huge_ptep_get_and_clear(struct mm_struct *mm,
  			      unsigned long addr, pte_t *ptep)
  {
  	int ncontig;
  	size_t pgsize;
  	pte_t orig_pte = huge_ptep_get(ptep);
  
  	if (!pte_cont(orig_pte))
  		return ptep_get_and_clear(mm, addr, ptep);
  
  	ncontig = find_num_contig(mm, addr, ptep, &pgsize);
  
  	return get_clear_flush(mm, addr, ptep, pgsize, ncontig);
  }
  
  /*
   * huge_ptep_set_access_flags will update access flags (dirty, accesssed)
   * and write permission.
   *
   * For a contiguous huge pte range we need to check whether or not write
   * permission has to change only on the first pte in the set. Then for
   * all the contiguous ptes we need to check whether or not there is a
   * discrepancy between dirty or young.
   */
  static int __cont_access_flags_changed(pte_t *ptep, pte_t pte, int ncontig)
  {
  	int i;
  
  	if (pte_write(pte) != pte_write(huge_ptep_get(ptep)))
  		return 1;
  
  	for (i = 0; i < ncontig; i++) {
  		pte_t orig_pte = huge_ptep_get(ptep + i);
  
  		if (pte_dirty(pte) != pte_dirty(orig_pte))
  			return 1;
  
  		if (pte_young(pte) != pte_young(orig_pte))
  			return 1;
  	}
  
  	return 0;
  }
  
  int huge_ptep_set_access_flags(struct vm_area_struct *vma,
  			       unsigned long addr, pte_t *ptep,
  			       pte_t pte, int dirty)
  {
  	int ncontig, i;
  	size_t pgsize = 0;
  	unsigned long pfn = pte_pfn(pte), dpfn;
  	pgprot_t hugeprot;
  	pte_t orig_pte;
  
  	if (!pte_cont(pte))
  		return ptep_set_access_flags(vma, addr, ptep, pte, dirty);
  
  	ncontig = find_num_contig(vma->vm_mm, addr, ptep, &pgsize);
  	dpfn = pgsize >> PAGE_SHIFT;
  
  	if (!__cont_access_flags_changed(ptep, pte, ncontig))
  		return 0;
  
  	orig_pte = get_clear_flush(vma->vm_mm, addr, ptep, pgsize, ncontig);
  
  	/* Make sure we don't lose the dirty or young state */
  	if (pte_dirty(orig_pte))
  		pte = pte_mkdirty(pte);
  
  	if (pte_young(orig_pte))
  		pte = pte_mkyoung(pte);
  
  	hugeprot = pte_pgprot(pte);
  	for (i = 0; i < ncontig; i++, ptep++, addr += pgsize, pfn += dpfn)
  		set_pte_at(vma->vm_mm, addr, ptep, pfn_pte(pfn, hugeprot));
  
  	return 1;
  }
  
  void huge_ptep_set_wrprotect(struct mm_struct *mm,
  			     unsigned long addr, pte_t *ptep)
  {
  	unsigned long pfn, dpfn;
  	pgprot_t hugeprot;
  	int ncontig, i;
  	size_t pgsize;
  	pte_t pte;
  
  	if (!pte_cont(READ_ONCE(*ptep))) {
  		ptep_set_wrprotect(mm, addr, ptep);
  		return;
  	}
  
  	ncontig = find_num_contig(mm, addr, ptep, &pgsize);
  	dpfn = pgsize >> PAGE_SHIFT;
  
  	pte = get_clear_flush(mm, addr, ptep, pgsize, ncontig);
  	pte = pte_wrprotect(pte);
  
  	hugeprot = pte_pgprot(pte);
  	pfn = pte_pfn(pte);
  
  	for (i = 0; i < ncontig; i++, ptep++, addr += pgsize, pfn += dpfn)
  		set_pte_at(mm, addr, ptep, pfn_pte(pfn, hugeprot));
  }
  
  void huge_ptep_clear_flush(struct vm_area_struct *vma,
  			   unsigned long addr, pte_t *ptep)
  {
  	size_t pgsize;
  	int ncontig;
  
  	if (!pte_cont(READ_ONCE(*ptep))) {
  		ptep_clear_flush(vma, addr, ptep);
  		return;
  	}
  
  	ncontig = find_num_contig(vma->vm_mm, addr, ptep, &pgsize);
  	clear_flush(vma->vm_mm, addr, ptep, pgsize, ncontig);
  }
  
  static int __init hugetlbpage_init(void)
  {
  #ifdef CONFIG_ARM64_4K_PAGES
  	hugetlb_add_hstate(PUD_SHIFT - PAGE_SHIFT);
  #endif
  	hugetlb_add_hstate(CONT_PMD_SHIFT - PAGE_SHIFT);
  	hugetlb_add_hstate(PMD_SHIFT - PAGE_SHIFT);
  	hugetlb_add_hstate(CONT_PTE_SHIFT - PAGE_SHIFT);
  
  	return 0;
  }
  arch_initcall(hugetlbpage_init);
  
  bool __init arch_hugetlb_valid_size(unsigned long size)
  {
  	switch (size) {
  #ifdef CONFIG_ARM64_4K_PAGES
  	case PUD_SIZE:
  #endif
  	case CONT_PMD_SIZE:
  	case PMD_SIZE:
  	case CONT_PTE_SIZE:
  		return true;
  	}
  
  	return false;
  }
  