/*
   *  mm/mprotect.c
   *
   *  (C) Copyright 1994 Linus Torvalds
   *  (C) Copyright 2002 Christoph Hellwig
   *

   *  Address space accounting code	<alan@lxorguk.ukuu.org.uk>

   *  (C) Copyright 2002 Red Hat Inc, All Rights Reserved
   */
  
  #include <linux/mm.h>
  #include <linux/hugetlb.h>

  #include <linux/shm.h>
  #include <linux/mman.h>
  #include <linux/fs.h>
  #include <linux/highmem.h>
  #include <linux/security.h>
  #include <linux/mempolicy.h>
  #include <linux/personality.h>
  #include <linux/syscalls.h>

  #include <linux/swap.h>
  #include <linux/swapops.h>

  #include <linux/mmu_notifier.h>

  #include <linux/migrate.h>

  #include <linux/perf_event.h>

  #include <linux/ksm.h>

  #include <linux/pkeys.h>

  #include <asm/uaccess.h>
  #include <asm/pgtable.h>
  #include <asm/cacheflush.h>
  #include <asm/tlbflush.h>

  #include "internal.h"

  /*
   * For a prot_numa update we only hold mmap_sem for read so there is a
   * potential race with faulting where a pmd was temporarily none. This
   * function checks for a transhuge pmd under the appropriate lock. It
   * returns a pte if it was successfully locked or NULL if it raced with
   * a transhuge insertion.
   */
  static pte_t *lock_pte_protection(struct vm_area_struct *vma, pmd_t *pmd,
  			unsigned long addr, int prot_numa, spinlock_t **ptl)
  {
  	pte_t *pte;
  	spinlock_t *pmdl;
  
  	/* !prot_numa is protected by mmap_sem held for write */
  	if (!prot_numa)
  		return pte_offset_map_lock(vma->vm_mm, pmd, addr, ptl);
  
  	pmdl = pmd_lock(vma->vm_mm, pmd);
  	if (unlikely(pmd_trans_huge(*pmd) || pmd_none(*pmd))) {
  		spin_unlock(pmdl);
  		return NULL;
  	}
  
  	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, ptl);
  	spin_unlock(pmdl);
  	return pte;
  }

  static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,

  		unsigned long addr, unsigned long end, pgprot_t newprot,

  		int dirty_accountable, int prot_numa)

  {

  	struct mm_struct *mm = vma->vm_mm;

  	pte_t *pte, oldpte;

  	spinlock_t *ptl;

  	unsigned long pages = 0;

  	pte = lock_pte_protection(vma, pmd, addr, prot_numa, &ptl);
  	if (!pte)
  		return 0;

  	arch_enter_lazy_mmu_mode();

  	do {

  		oldpte = *pte;
  		if (pte_present(oldpte)) {

  			pte_t ptent;

  			bool preserve_write = prot_numa && pte_write(oldpte);

  			/*
  			 * Avoid trapping faults against the zero or KSM
  			 * pages. See similar comment in change_huge_pmd.
  			 */
  			if (prot_numa) {
  				struct page *page;
  
  				page = vm_normal_page(vma, addr, oldpte);
  				if (!page || PageKsm(page))
  					continue;

  
  				/* Avoid TLB flush if possible */
  				if (pte_protnone(oldpte))
  					continue;

  			}

  			ptent = ptep_modify_prot_start(mm, addr, pte);
  			ptent = pte_modify(ptent, newprot);

  			if (preserve_write)
  				ptent = pte_mkwrite(ptent);

  			/* Avoid taking write faults for known dirty pages */
  			if (dirty_accountable && pte_dirty(ptent) &&
  					(pte_soft_dirty(ptent) ||
  					 !(vma->vm_flags & VM_SOFTDIRTY))) {
  				ptent = pte_mkwrite(ptent);

  			}

  			ptep_modify_prot_commit(mm, addr, pte, ptent);
  			pages++;

  		} else if (IS_ENABLED(CONFIG_MIGRATION)) {

  			swp_entry_t entry = pte_to_swp_entry(oldpte);
  
  			if (is_write_migration_entry(entry)) {

  				pte_t newpte;

  				/*
  				 * A protection check is difficult so
  				 * just be safe and disable write
  				 */
  				make_migration_entry_read(&entry);

  				newpte = swp_entry_to_pte(entry);
  				if (pte_swp_soft_dirty(oldpte))
  					newpte = pte_swp_mksoft_dirty(newpte);
  				set_pte_at(mm, addr, pte, newpte);

  
  				pages++;

  			}

  		}
  	} while (pte++, addr += PAGE_SIZE, addr != end);

  	arch_leave_lazy_mmu_mode();

  	pte_unmap_unlock(pte - 1, ptl);

  
  	return pages;

  }

  static inline unsigned long change_pmd_range(struct vm_area_struct *vma,
  		pud_t *pud, unsigned long addr, unsigned long end,
  		pgprot_t newprot, int dirty_accountable, int prot_numa)

  {
  	pmd_t *pmd;

  	struct mm_struct *mm = vma->vm_mm;

  	unsigned long next;

  	unsigned long pages = 0;

  	unsigned long nr_huge_updates = 0;

  	unsigned long mni_start = 0;

  
  	pmd = pmd_offset(pud, addr);
  	do {

  		unsigned long this_pages;

  		next = pmd_addr_end(addr, end);

  		if (!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd)
  				&& pmd_none_or_clear_bad(pmd))

  			continue;

  
  		/* invoke the mmu notifier if the pmd is populated */
  		if (!mni_start) {
  			mni_start = addr;
  			mmu_notifier_invalidate_range_start(mm, mni_start, end);
  		}

  		if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd)) {

  			if (next - addr != HPAGE_PMD_SIZE) {

  				split_huge_pmd(vma, pmd, addr);

  				if (pmd_none(*pmd))
  					continue;
  			} else {

  				int nr_ptes = change_huge_pmd(vma, pmd, addr,

  						newprot, prot_numa);

  
  				if (nr_ptes) {

  					if (nr_ptes == HPAGE_PMD_NR) {
  						pages += HPAGE_PMD_NR;
  						nr_huge_updates++;
  					}

  
  					/* huge pmd was handled */

  					continue;
  				}

  			}

  			/* fall through, the trans huge pmd just split */

  		}

  		this_pages = change_pte_range(vma, pmd, addr, next, newprot,

  				 dirty_accountable, prot_numa);

  		pages += this_pages;

  	} while (pmd++, addr = next, addr != end);

  	if (mni_start)
  		mmu_notifier_invalidate_range_end(mm, mni_start, end);

  	if (nr_huge_updates)
  		count_vm_numa_events(NUMA_HUGE_PTE_UPDATES, nr_huge_updates);

  	return pages;

  }

  static inline unsigned long change_pud_range(struct vm_area_struct *vma,
  		pgd_t *pgd, unsigned long addr, unsigned long end,
  		pgprot_t newprot, int dirty_accountable, int prot_numa)

  {
  	pud_t *pud;
  	unsigned long next;

  	unsigned long pages = 0;

  
  	pud = pud_offset(pgd, addr);
  	do {
  		next = pud_addr_end(addr, end);
  		if (pud_none_or_clear_bad(pud))
  			continue;

  		pages += change_pmd_range(vma, pud, addr, next, newprot,

  				 dirty_accountable, prot_numa);

  	} while (pud++, addr = next, addr != end);

  
  	return pages;

  }

  static unsigned long change_protection_range(struct vm_area_struct *vma,

  		unsigned long addr, unsigned long end, pgprot_t newprot,

  		int dirty_accountable, int prot_numa)

  {
  	struct mm_struct *mm = vma->vm_mm;
  	pgd_t *pgd;
  	unsigned long next;
  	unsigned long start = addr;

  	unsigned long pages = 0;

  
  	BUG_ON(addr >= end);
  	pgd = pgd_offset(mm, addr);
  	flush_cache_range(vma, addr, end);

  	set_tlb_flush_pending(mm);

  	do {
  		next = pgd_addr_end(addr, end);
  		if (pgd_none_or_clear_bad(pgd))
  			continue;

  		pages += change_pud_range(vma, pgd, addr, next, newprot,

  				 dirty_accountable, prot_numa);

  	} while (pgd++, addr = next, addr != end);

  	/* Only flush the TLB if we actually modified any entries: */
  	if (pages)
  		flush_tlb_range(vma, start, end);

  	clear_tlb_flush_pending(mm);

  
  	return pages;
  }
  
  unsigned long change_protection(struct vm_area_struct *vma, unsigned long start,
  		       unsigned long end, pgprot_t newprot,

  		       int dirty_accountable, int prot_numa)

  {

  	unsigned long pages;

  	if (is_vm_hugetlb_page(vma))
  		pages = hugetlb_change_protection(vma, start, end, newprot);
  	else

  		pages = change_protection_range(vma, start, end, newprot, dirty_accountable, prot_numa);

  
  	return pages;

  }

  int

  mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
  	unsigned long start, unsigned long end, unsigned long newflags)
  {
  	struct mm_struct *mm = vma->vm_mm;
  	unsigned long oldflags = vma->vm_flags;
  	long nrpages = (end - start) >> PAGE_SHIFT;
  	unsigned long charged = 0;

  	pgoff_t pgoff;
  	int error;

  	int dirty_accountable = 0;

  
  	if (newflags == oldflags) {
  		*pprev = vma;
  		return 0;
  	}
  
  	/*
  	 * If we make a private mapping writable we increase our commit;
  	 * but (without finer accounting) cannot reduce our commit if we

  	 * make it unwritable again. hugetlb mapping were accounted for
  	 * even if read-only so there is no need to account for them here

  	 */
  	if (newflags & VM_WRITE) {

  		/* Check space limits when area turns into data. */
  		if (!may_expand_vm(mm, newflags, nrpages) &&
  				may_expand_vm(mm, oldflags, nrpages))
  			return -ENOMEM;

  		if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB|

  						VM_SHARED|VM_NORESERVE))) {

  			charged = nrpages;

  			if (security_vm_enough_memory_mm(mm, charged))

  				return -ENOMEM;
  			newflags |= VM_ACCOUNT;
  		}
  	}

  	/*
  	 * First try to merge with previous and/or next vma.
  	 */
  	pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
  	*pprev = vma_merge(mm, *pprev, start, end, newflags,

  			   vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma),
  			   vma->vm_userfaultfd_ctx);

  	if (*pprev) {
  		vma = *pprev;
  		goto success;
  	}
  
  	*pprev = vma;
  
  	if (start != vma->vm_start) {
  		error = split_vma(mm, vma, start, 1);
  		if (error)
  			goto fail;
  	}
  
  	if (end != vma->vm_end) {
  		error = split_vma(mm, vma, end, 0);
  		if (error)
  			goto fail;
  	}
  
  success:
  	/*
  	 * vm_flags and vm_page_prot are protected by the mmap_sem
  	 * held in write mode.
  	 */
  	vma->vm_flags = newflags;

  	dirty_accountable = vma_wants_writenotify(vma);
  	vma_set_page_prot(vma);

  	change_protection(vma, start, end, vma->vm_page_prot,
  			  dirty_accountable, 0);

  	/*
  	 * Private VM_LOCKED VMA becoming writable: trigger COW to avoid major
  	 * fault on access.
  	 */
  	if ((oldflags & (VM_WRITE | VM_SHARED | VM_LOCKED)) == VM_LOCKED &&
  			(newflags & VM_WRITE)) {
  		populate_vma_page_range(vma, start, end, NULL);
  	}

  	vm_stat_account(mm, oldflags, -nrpages);
  	vm_stat_account(mm, newflags, nrpages);

  	perf_event_mmap(vma);

  	return 0;
  
  fail:
  	vm_unacct_memory(charged);
  	return error;
  }

  SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len,
  		unsigned long, prot)

  {

  	unsigned long nstart, end, tmp, reqprot;

  	struct vm_area_struct *vma, *prev;
  	int error = -EINVAL;
  	const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP);

  	const bool rier = (current->personality & READ_IMPLIES_EXEC) &&
  				(prot & PROT_READ);

  	prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP);
  	if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */
  		return -EINVAL;
  
  	if (start & ~PAGE_MASK)
  		return -EINVAL;
  	if (!len)
  		return 0;
  	len = PAGE_ALIGN(len);
  	end = start + len;
  	if (end <= start)
  		return -ENOMEM;

  	if (!arch_validate_prot(prot))

  		return -EINVAL;
  
  	reqprot = prot;

  	down_write(&current->mm->mmap_sem);

  	vma = find_vma(current->mm, start);

  	error = -ENOMEM;
  	if (!vma)
  		goto out;

  	prev = vma->vm_prev;

  	if (unlikely(grows & PROT_GROWSDOWN)) {
  		if (vma->vm_start >= end)
  			goto out;
  		start = vma->vm_start;
  		error = -EINVAL;
  		if (!(vma->vm_flags & VM_GROWSDOWN))
  			goto out;

  	} else {

  		if (vma->vm_start > start)
  			goto out;
  		if (unlikely(grows & PROT_GROWSUP)) {
  			end = vma->vm_end;
  			error = -EINVAL;
  			if (!(vma->vm_flags & VM_GROWSUP))
  				goto out;
  		}
  	}
  	if (start > vma->vm_start)
  		prev = vma;
  
  	for (nstart = start ; ; ) {
  		unsigned long newflags;

  		int pkey = arch_override_mprotect_pkey(vma, prot, -1);

  		/* Here we know that vma->vm_start <= nstart < vma->vm_end. */

  		/* Does the application expect PROT_READ to imply PROT_EXEC */
  		if (rier && (vma->vm_flags & VM_MAYEXEC))
  			prot |= PROT_EXEC;

  		newflags = calc_vm_prot_bits(prot, pkey);

  		newflags |= (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC));

  		/* newflags >> 4 shift VM_MAY% in place of VM_% */
  		if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) {

  			error = -EACCES;
  			goto out;
  		}
  
  		error = security_file_mprotect(vma, reqprot, prot);
  		if (error)
  			goto out;
  
  		tmp = vma->vm_end;
  		if (tmp > end)
  			tmp = end;
  		error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);
  		if (error)
  			goto out;
  		nstart = tmp;
  
  		if (nstart < prev->vm_end)
  			nstart = prev->vm_end;
  		if (nstart >= end)
  			goto out;
  
  		vma = prev->vm_next;
  		if (!vma || vma->vm_start != nstart) {
  			error = -ENOMEM;
  			goto out;
  		}

  		prot = reqprot;

  	}
  out:
  	up_write(&current->mm->mmap_sem);
  	return error;
  }