/*
   * Copyright 2007-2008 Paul Mackerras, IBM Corp.
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License
   * as published by the Free Software Foundation; either version
   * 2 of the License, or (at your option) any later version.
   */
  
  #include <linux/errno.h>
  #include <linux/kernel.h>
  #include <linux/gfp.h>
  #include <linux/types.h>
  #include <linux/mm.h>
  #include <linux/hugetlb.h>
  
  #include <asm/pgtable.h>
  #include <asm/uaccess.h>
  #include <asm/tlbflush.h>
  
  /*
   * Free all pages allocated for subpage protection maps and pointers.
   * Also makes sure that the subpage_prot_table structure is
   * reinitialized for the next user.
   */
  void subpage_prot_free(struct mm_struct *mm)
  {
  	struct subpage_prot_table *spt = &mm->context.spt;
  	unsigned long i, j, addr;
  	u32 **p;
  
  	for (i = 0; i < 4; ++i) {
  		if (spt->low_prot[i]) {
  			free_page((unsigned long)spt->low_prot[i]);
  			spt->low_prot[i] = NULL;
  		}
  	}
  	addr = 0;
  	for (i = 0; i < 2; ++i) {
  		p = spt->protptrs[i];
  		if (!p)
  			continue;
  		spt->protptrs[i] = NULL;
  		for (j = 0; j < SBP_L2_COUNT && addr < spt->maxaddr;
  		     ++j, addr += PAGE_SIZE)
  			if (p[j])
  				free_page((unsigned long)p[j]);
  		free_page((unsigned long)p);
  	}
  	spt->maxaddr = 0;
  }
  
  void subpage_prot_init_new_context(struct mm_struct *mm)
  {
  	struct subpage_prot_table *spt = &mm->context.spt;
  
  	memset(spt, 0, sizeof(*spt));
  }
  
  static void hpte_flush_range(struct mm_struct *mm, unsigned long addr,
  			     int npages)
  {
  	pgd_t *pgd;
  	pud_t *pud;
  	pmd_t *pmd;
  	pte_t *pte;
  	spinlock_t *ptl;
  
  	pgd = pgd_offset(mm, addr);
  	if (pgd_none(*pgd))
  		return;
  	pud = pud_offset(pgd, addr);
  	if (pud_none(*pud))
  		return;
  	pmd = pmd_offset(pud, addr);
  	if (pmd_none(*pmd))
  		return;
  	pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
  	arch_enter_lazy_mmu_mode();
  	for (; npages > 0; --npages) {
  		pte_update(mm, addr, pte, 0, 0, 0);
  		addr += PAGE_SIZE;
  		++pte;
  	}
  	arch_leave_lazy_mmu_mode();
  	pte_unmap_unlock(pte - 1, ptl);
  }
  
  /*
   * Clear the subpage protection map for an address range, allowing
   * all accesses that are allowed by the pte permissions.
   */
  static void subpage_prot_clear(unsigned long addr, unsigned long len)
  {
  	struct mm_struct *mm = current->mm;
  	struct subpage_prot_table *spt = &mm->context.spt;
  	u32 **spm, *spp;
  	unsigned long i;
  	size_t nw;
  	unsigned long next, limit;
  
  	down_write(&mm->mmap_sem);
  	limit = addr + len;
  	if (limit > spt->maxaddr)
  		limit = spt->maxaddr;
  	for (; addr < limit; addr = next) {
  		next = pmd_addr_end(addr, limit);
  		if (addr < 0x100000000UL) {
  			spm = spt->low_prot;
  		} else {
  			spm = spt->protptrs[addr >> SBP_L3_SHIFT];
  			if (!spm)
  				continue;
  		}
  		spp = spm[(addr >> SBP_L2_SHIFT) & (SBP_L2_COUNT - 1)];
  		if (!spp)
  			continue;
  		spp += (addr >> PAGE_SHIFT) & (SBP_L1_COUNT - 1);
  
  		i = (addr >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
  		nw = PTRS_PER_PTE - i;
  		if (addr + (nw << PAGE_SHIFT) > next)
  			nw = (next - addr) >> PAGE_SHIFT;
  
  		memset(spp, 0, nw * sizeof(u32));
  
  		/* now flush any existing HPTEs for the range */
  		hpte_flush_range(mm, addr, nw);
  	}
  	up_write(&mm->mmap_sem);
  }
  
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  static int subpage_walk_pmd_entry(pmd_t *pmd, unsigned long addr,
  				  unsigned long end, struct mm_walk *walk)
  {
  	struct vm_area_struct *vma = walk->private;
  	split_huge_page_pmd(vma, addr, pmd);
  	return 0;
  }
  
  static void subpage_mark_vma_nohuge(struct mm_struct *mm, unsigned long addr,
  				    unsigned long len)
  {
  	struct vm_area_struct *vma;
  	struct mm_walk subpage_proto_walk = {
  		.mm = mm,
  		.pmd_entry = subpage_walk_pmd_entry,
  	};
  
  	/*
  	 * We don't try too hard, we just mark all the vma in that range
  	 * VM_NOHUGEPAGE and split them.
  	 */
  	vma = find_vma(mm, addr);
  	/*
  	 * If the range is in unmapped range, just return
  	 */
  	if (vma && ((addr + len) <= vma->vm_start))
  		return;
  
  	while (vma) {
  		if (vma->vm_start >= (addr + len))
  			break;
  		vma->vm_flags |= VM_NOHUGEPAGE;
  		subpage_proto_walk.private = vma;
  		walk_page_range(vma->vm_start, vma->vm_end,
  				&subpage_proto_walk);
  		vma = vma->vm_next;
  	}
  }
  #else
  static void subpage_mark_vma_nohuge(struct mm_struct *mm, unsigned long addr,
  				    unsigned long len)
  {
  	return;
  }
  #endif
  
  /*
   * Copy in a subpage protection map for an address range.
   * The map has 2 bits per 4k subpage, so 32 bits per 64k page.
   * Each 2-bit field is 0 to allow any access, 1 to prevent writes,
   * 2 or 3 to prevent all accesses.
   * Note that the normal page protections also apply; the subpage
   * protection mechanism is an additional constraint, so putting 0
   * in a 2-bit field won't allow writes to a page that is otherwise
   * write-protected.
   */
  long sys_subpage_prot(unsigned long addr, unsigned long len, u32 __user *map)
  {
  	struct mm_struct *mm = current->mm;
  	struct subpage_prot_table *spt = &mm->context.spt;
  	u32 **spm, *spp;
  	unsigned long i;
  	size_t nw;
  	unsigned long next, limit;
  	int err;
  
  	/* Check parameters */
  	if ((addr & ~PAGE_MASK) || (len & ~PAGE_MASK) ||
  	    addr >= TASK_SIZE || len >= TASK_SIZE || addr + len > TASK_SIZE)
  		return -EINVAL;
  
  	if (is_hugepage_only_range(mm, addr, len))
  		return -EINVAL;
  
  	if (!map) {
  		/* Clear out the protection map for the address range */
  		subpage_prot_clear(addr, len);
  		return 0;
  	}
  
  	if (!access_ok(VERIFY_READ, map, (len >> PAGE_SHIFT) * sizeof(u32)))
  		return -EFAULT;
  
  	down_write(&mm->mmap_sem);
  	subpage_mark_vma_nohuge(mm, addr, len);
  	for (limit = addr + len; addr < limit; addr = next) {
  		next = pmd_addr_end(addr, limit);
  		err = -ENOMEM;
  		if (addr < 0x100000000UL) {
  			spm = spt->low_prot;
  		} else {
  			spm = spt->protptrs[addr >> SBP_L3_SHIFT];
  			if (!spm) {
  				spm = (u32 **)get_zeroed_page(GFP_KERNEL);
  				if (!spm)
  					goto out;
  				spt->protptrs[addr >> SBP_L3_SHIFT] = spm;
  			}
  		}
  		spm += (addr >> SBP_L2_SHIFT) & (SBP_L2_COUNT - 1);
  		spp = *spm;
  		if (!spp) {
  			spp = (u32 *)get_zeroed_page(GFP_KERNEL);
  			if (!spp)
  				goto out;
  			*spm = spp;
  		}
  		spp += (addr >> PAGE_SHIFT) & (SBP_L1_COUNT - 1);
  
  		local_irq_disable();
  		demote_segment_4k(mm, addr);
  		local_irq_enable();
  
  		i = (addr >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
  		nw = PTRS_PER_PTE - i;
  		if (addr + (nw << PAGE_SHIFT) > next)
  			nw = (next - addr) >> PAGE_SHIFT;
  
  		up_write(&mm->mmap_sem);
  		err = -EFAULT;
  		if (__copy_from_user(spp, map, nw * sizeof(u32)))
  			goto out2;
  		map += nw;
  		down_write(&mm->mmap_sem);
  
  		/* now flush any existing HPTEs for the range */
  		hpte_flush_range(mm, addr, nw);
  	}
  	if (limit > spt->maxaddr)
  		spt->maxaddr = limit;
  	err = 0;
   out:
  	up_write(&mm->mmap_sem);
   out2:
  	return err;
  }