arch/powerpc/mm/subpage-prot.c - linux - Git at Google

 /*
  * 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 <linux/syscalls.h>

 #include <asm/pgtable.h>
 #include <linux/uaccess.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 < (TASK_SIZE_USER64 >> 43); ++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->vma;
 	split_huge_pmd(vma, pmd, addr);
 	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;
 		walk_page_vma(vma, &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.
  */
 SYSCALL_DEFINE3(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;

 	if (radix_enabled())
 		return -ENOENT;

 	/* Check parameters */
 	if ((addr & ~PAGE_MASK) || (len & ~PAGE_MASK) ||
 	    addr >= mm->task_size || len >= mm->task_size ||
 	    addr + len > mm->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(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);
 		if (__copy_from_user(spp, map, nw * sizeof(u32)))
 			return -EFAULT;
 		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);
 	return err;
 }
	/*
	* 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 <linux/syscalls.h>

	#include <asm/pgtable.h>
	#include <linux/uaccess.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 < (TASK_SIZE_USER64 >> 43); ++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->vma;
	split_huge_pmd(vma, pmd, addr);
	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;
	walk_page_vma(vma, &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.
	*/
	SYSCALL_DEFINE3(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;

	if (radix_enabled())
	return -ENOENT;

	/* Check parameters */
	if ((addr & ~PAGE_MASK) \|\| (len & ~PAGE_MASK) \|\|
	addr >= mm->task_size \|\| len >= mm->task_size \|\|
	addr + len > mm->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(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);
	if (__copy_from_user(spp, map, nw * sizeof(u32)))
	return -EFAULT;
	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);
	return err;
	}