arch/powerpc/mm/slice.c - kernel/lockdown - Git at Google

 /*
  * address space "slices" (meta-segments) support
  *
  * Copyright (C) 2007 Benjamin Herrenschmidt, IBM Corporation.
  *
  * Based on hugetlb implementation
  *
  * Copyright (C) 2003 David Gibson, IBM Corporation.
  *
  * 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.
  *
  * 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, write to the Free Software
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  */

 #undef DEBUG

 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/pagemap.h>
 #include <linux/err.h>
 #include <linux/spinlock.h>
 #include <linux/export.h>
 #include <linux/hugetlb.h>
 #include <asm/mman.h>
 #include <asm/mmu.h>
 #include <asm/copro.h>
 #include <asm/hugetlb.h>

 /* some sanity checks */
 #if (PGTABLE_RANGE >> 43) > SLICE_MASK_SIZE
 #error PGTABLE_RANGE exceeds slice_mask high_slices size
 #endif

 static DEFINE_SPINLOCK(slice_convert_lock);


 #ifdef DEBUG
 int _slice_debug = 1;

 static void slice_print_mask(const char *label, struct slice_mask mask)
 {
 	char	*p, buf[16 + 3 + 64 + 1];
 	int	i;

 	if (!_slice_debug)
 		return;
 	p = buf;
 	for (i = 0; i < SLICE_NUM_LOW; i++)
 		*(p++) = (mask.low_slices & (1 << i)) ? '1' : '0';
 	*(p++) = ' ';
 	*(p++) = '-';
 	*(p++) = ' ';
 	for (i = 0; i < SLICE_NUM_HIGH; i++)
 		*(p++) = (mask.high_slices & (1ul << i)) ? '1' : '0';
 	*(p++) = 0;

 	printk(KERN_DEBUG "%s:%s\n", label, buf);
 }

 #define slice_dbg(fmt...) do { if (_slice_debug) pr_debug(fmt); } while(0)

 #else

 static void slice_print_mask(const char *label, struct slice_mask mask) {}
 #define slice_dbg(fmt...)

 #endif

 static struct slice_mask slice_range_to_mask(unsigned long start,
 					     unsigned long len)
 {
 	unsigned long end = start + len - 1;
 	struct slice_mask ret = { 0, 0 };

 	if (start < SLICE_LOW_TOP) {
 		unsigned long mend = min(end, SLICE_LOW_TOP);
 		unsigned long mstart = min(start, SLICE_LOW_TOP);

 		ret.low_slices = (1u << (GET_LOW_SLICE_INDEX(mend) + 1))
 			- (1u << GET_LOW_SLICE_INDEX(mstart));
 	}

 	if ((start + len) > SLICE_LOW_TOP)
 		ret.high_slices = (1ul << (GET_HIGH_SLICE_INDEX(end) + 1))
 			- (1ul << GET_HIGH_SLICE_INDEX(start));

 	return ret;
 }

 static int slice_area_is_free(struct mm_struct *mm, unsigned long addr,
 			      unsigned long len)
 {
 	struct vm_area_struct *vma;

 	if ((mm->task_size - len) < addr)
 		return 0;
 	vma = find_vma(mm, addr);
 	return (!vma || (addr + len) <= vma->vm_start);
 }

 static int slice_low_has_vma(struct mm_struct *mm, unsigned long slice)
 {
 	return !slice_area_is_free(mm, slice << SLICE_LOW_SHIFT,
 				   1ul << SLICE_LOW_SHIFT);
 }

 static int slice_high_has_vma(struct mm_struct *mm, unsigned long slice)
 {
 	unsigned long start = slice << SLICE_HIGH_SHIFT;
 	unsigned long end = start + (1ul << SLICE_HIGH_SHIFT);

 	/* Hack, so that each addresses is controlled by exactly one
 	 * of the high or low area bitmaps, the first high area starts
 	 * at 4GB, not 0 */
 	if (start == 0)
 		start = SLICE_LOW_TOP;

 	return !slice_area_is_free(mm, start, end - start);
 }

 static struct slice_mask slice_mask_for_free(struct mm_struct *mm)
 {
 	struct slice_mask ret = { 0, 0 };
 	unsigned long i;

 	for (i = 0; i < SLICE_NUM_LOW; i++)
 		if (!slice_low_has_vma(mm, i))
 			ret.low_slices |= 1u << i;

 	if (mm->task_size <= SLICE_LOW_TOP)
 		return ret;

 	for (i = 0; i < SLICE_NUM_HIGH; i++)
 		if (!slice_high_has_vma(mm, i))
 			ret.high_slices |= 1ul << i;

 	return ret;
 }

 static struct slice_mask slice_mask_for_size(struct mm_struct *mm, int psize)
 {
 	unsigned char *hpsizes;
 	int index, mask_index;
 	struct slice_mask ret = { 0, 0 };
 	unsigned long i;
 	u64 lpsizes;

 	lpsizes = mm->context.low_slices_psize;
 	for (i = 0; i < SLICE_NUM_LOW; i++)
 		if (((lpsizes >> (i * 4)) & 0xf) == psize)
 			ret.low_slices |= 1u << i;

 	hpsizes = mm->context.high_slices_psize;
 	for (i = 0; i < SLICE_NUM_HIGH; i++) {
 		mask_index = i & 0x1;
 		index = i >> 1;
 		if (((hpsizes[index] >> (mask_index * 4)) & 0xf) == psize)
 			ret.high_slices |= 1ul << i;
 	}

 	return ret;
 }

 static int slice_check_fit(struct slice_mask mask, struct slice_mask available)
 {
 	return (mask.low_slices & available.low_slices) == mask.low_slices &&
 		(mask.high_slices & available.high_slices) == mask.high_slices;
 }

 static void slice_flush_segments(void *parm)
 {
 	struct mm_struct *mm = parm;
 	unsigned long flags;

 	if (mm != current->active_mm)
 		return;

 	/* update the paca copy of the context struct */
 	get_paca()->context = current->active_mm->context;

 	local_irq_save(flags);
 	slb_flush_and_rebolt();
 	local_irq_restore(flags);
 }

 static void slice_convert(struct mm_struct *mm, struct slice_mask mask, int psize)
 {
 	int index, mask_index;
 	/* Write the new slice psize bits */
 	unsigned char *hpsizes;
 	u64 lpsizes;
 	unsigned long i, flags;

 	slice_dbg("slice_convert(mm=%p, psize=%d)\n", mm, psize);
 	slice_print_mask(" mask", mask);

 	/* We need to use a spinlock here to protect against
 	 * concurrent 64k -> 4k demotion ...
 	 */
 	spin_lock_irqsave(&slice_convert_lock, flags);

 	lpsizes = mm->context.low_slices_psize;
 	for (i = 0; i < SLICE_NUM_LOW; i++)
 		if (mask.low_slices & (1u << i))
 			lpsizes = (lpsizes & ~(0xful << (i * 4))) |
 				(((unsigned long)psize) << (i * 4));

 	/* Assign the value back */
 	mm->context.low_slices_psize = lpsizes;

 	hpsizes = mm->context.high_slices_psize;
 	for (i = 0; i < SLICE_NUM_HIGH; i++) {
 		mask_index = i & 0x1;
 		index = i >> 1;
 		if (mask.high_slices & (1ul << i))
 			hpsizes[index] = (hpsizes[index] &
 					  ~(0xf << (mask_index * 4))) |
 				(((unsigned long)psize) << (mask_index * 4));
 	}

 	slice_dbg(" lsps=%lx, hsps=%lx\n",
 		  mm->context.low_slices_psize,
 		  mm->context.high_slices_psize);

 	spin_unlock_irqrestore(&slice_convert_lock, flags);

 	copro_flush_all_slbs(mm);
 }

 /*
  * Compute which slice addr is part of;
  * set *boundary_addr to the start or end boundary of that slice
  * (depending on 'end' parameter);
  * return boolean indicating if the slice is marked as available in the
  * 'available' slice_mark.
  */
 static bool slice_scan_available(unsigned long addr,
 				 struct slice_mask available,
 				 int end,
 				 unsigned long *boundary_addr)
 {
 	unsigned long slice;
 	if (addr < SLICE_LOW_TOP) {
 		slice = GET_LOW_SLICE_INDEX(addr);
 		*boundary_addr = (slice + end) << SLICE_LOW_SHIFT;
 		return !!(available.low_slices & (1u << slice));
 	} else {
 		slice = GET_HIGH_SLICE_INDEX(addr);
 		*boundary_addr = (slice + end) ?
 			((slice + end) << SLICE_HIGH_SHIFT) : SLICE_LOW_TOP;
 		return !!(available.high_slices & (1ul << slice));
 	}
 }

 static unsigned long slice_find_area_bottomup(struct mm_struct *mm,
 					      unsigned long len,
 					      struct slice_mask available,
 					      int psize)
 {
 	int pshift = max_t(int, mmu_psize_defs[psize].shift, PAGE_SHIFT);
 	unsigned long addr, found, next_end;
 	struct vm_unmapped_area_info info;

 	info.flags = 0;
 	info.length = len;
 	info.align_mask = PAGE_MASK & ((1ul << pshift) - 1);
 	info.align_offset = 0;

 	addr = TASK_UNMAPPED_BASE;
 	while (addr < TASK_SIZE) {
 		info.low_limit = addr;
 		if (!slice_scan_available(addr, available, 1, &addr))
 			continue;

  next_slice:
 		/*
 		 * At this point [info.low_limit; addr) covers
 		 * available slices only and ends at a slice boundary.
 		 * Check if we need to reduce the range, or if we can
 		 * extend it to cover the next available slice.
 		 */
 		if (addr >= TASK_SIZE)
 			addr = TASK_SIZE;
 		else if (slice_scan_available(addr, available, 1, &next_end)) {
 			addr = next_end;
 			goto next_slice;
 		}
 		info.high_limit = addr;

 		found = vm_unmapped_area(&info);
 		if (!(found & ~PAGE_MASK))
 			return found;
 	}

 	return -ENOMEM;
 }

 static unsigned long slice_find_area_topdown(struct mm_struct *mm,
 					     unsigned long len,
 					     struct slice_mask available,
 					     int psize)
 {
 	int pshift = max_t(int, mmu_psize_defs[psize].shift, PAGE_SHIFT);
 	unsigned long addr, found, prev;
 	struct vm_unmapped_area_info info;

 	info.flags = VM_UNMAPPED_AREA_TOPDOWN;
 	info.length = len;
 	info.align_mask = PAGE_MASK & ((1ul << pshift) - 1);
 	info.align_offset = 0;

 	addr = mm->mmap_base;
 	while (addr > PAGE_SIZE) {
 		info.high_limit = addr;
 		if (!slice_scan_available(addr - 1, available, 0, &addr))
 			continue;

  prev_slice:
 		/*
 		 * At this point [addr; info.high_limit) covers
 		 * available slices only and starts at a slice boundary.
 		 * Check if we need to reduce the range, or if we can
 		 * extend it to cover the previous available slice.
 		 */
 		if (addr < PAGE_SIZE)
 			addr = PAGE_SIZE;
 		else if (slice_scan_available(addr - 1, available, 0, &prev)) {
 			addr = prev;
 			goto prev_slice;
 		}
 		info.low_limit = addr;

 		found = vm_unmapped_area(&info);
 		if (!(found & ~PAGE_MASK))
 			return found;
 	}

 	/*
 	 * A failed mmap() very likely causes application failure,
 	 * so fall back to the bottom-up function here. This scenario
 	 * can happen with large stack limits and large mmap()
 	 * allocations.
 	 */
 	return slice_find_area_bottomup(mm, len, available, psize);
 }


 static unsigned long slice_find_area(struct mm_struct *mm, unsigned long len,
 				     struct slice_mask mask, int psize,
 				     int topdown)
 {
 	if (topdown)
 		return slice_find_area_topdown(mm, len, mask, psize);
 	else
 		return slice_find_area_bottomup(mm, len, mask, psize);
 }

 #define or_mask(dst, src)	do {			\
 	(dst).low_slices |= (src).low_slices;		\
 	(dst).high_slices |= (src).high_slices;		\
 } while (0)

 #define andnot_mask(dst, src)	do {			\
 	(dst).low_slices &= ~(src).low_slices;		\
 	(dst).high_slices &= ~(src).high_slices;	\
 } while (0)

 #ifdef CONFIG_PPC_64K_PAGES
 #define MMU_PAGE_BASE	MMU_PAGE_64K
 #else
 #define MMU_PAGE_BASE	MMU_PAGE_4K
 #endif

 unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
 				      unsigned long flags, unsigned int psize,
 				      int topdown)
 {
 	struct slice_mask mask = {0, 0};
 	struct slice_mask good_mask;
 	struct slice_mask potential_mask = {0,0} /* silence stupid warning */;
 	struct slice_mask compat_mask = {0, 0};
 	int fixed = (flags & MAP_FIXED);
 	int pshift = max_t(int, mmu_psize_defs[psize].shift, PAGE_SHIFT);
 	struct mm_struct *mm = current->mm;
 	unsigned long newaddr;

 	/* Sanity checks */
 	BUG_ON(mm->task_size == 0);

 	slice_dbg("slice_get_unmapped_area(mm=%p, psize=%d...\n", mm, psize);
 	slice_dbg(" addr=%lx, len=%lx, flags=%lx, topdown=%d\n",
 		  addr, len, flags, topdown);

 	if (len > mm->task_size)
 		return -ENOMEM;
 	if (len & ((1ul << pshift) - 1))
 		return -EINVAL;
 	if (fixed && (addr & ((1ul << pshift) - 1)))
 		return -EINVAL;
 	if (fixed && addr > (mm->task_size - len))
 		return -ENOMEM;

 	/* If hint, make sure it matches our alignment restrictions */
 	if (!fixed && addr) {
 		addr = _ALIGN_UP(addr, 1ul << pshift);
 		slice_dbg(" aligned addr=%lx\n", addr);
 		/* Ignore hint if it's too large or overlaps a VMA */
 		if (addr > mm->task_size - len ||
 		    !slice_area_is_free(mm, addr, len))
 			addr = 0;
 	}

 	/* First make up a "good" mask of slices that have the right size
 	 * already
 	 */
 	good_mask = slice_mask_for_size(mm, psize);
 	slice_print_mask(" good_mask", good_mask);

 	/*
 	 * Here "good" means slices that are already the right page size,
 	 * "compat" means slices that have a compatible page size (i.e.
 	 * 4k in a 64k pagesize kernel), and "free" means slices without
 	 * any VMAs.
 	 *
 	 * If MAP_FIXED:
 	 *	check if fits in good | compat => OK
 	 *	check if fits in good | compat | free => convert free
 	 *	else bad
 	 * If have hint:
 	 *	check if hint fits in good => OK
 	 *	check if hint fits in good | free => convert free
 	 * Otherwise:
 	 *	search in good, found => OK
 	 *	search in good | free, found => convert free
 	 *	search in good | compat | free, found => convert free.
 	 */

 #ifdef CONFIG_PPC_64K_PAGES
 	/* If we support combo pages, we can allow 64k pages in 4k slices */
 	if (psize == MMU_PAGE_64K) {
 		compat_mask = slice_mask_for_size(mm, MMU_PAGE_4K);
 		if (fixed)
 			or_mask(good_mask, compat_mask);
 	}
 #endif

 	/* First check hint if it's valid or if we have MAP_FIXED */
 	if (addr != 0 || fixed) {
 		/* Build a mask for the requested range */
 		mask = slice_range_to_mask(addr, len);
 		slice_print_mask(" mask", mask);

 		/* Check if we fit in the good mask. If we do, we just return,
 		 * nothing else to do
 		 */
 		if (slice_check_fit(mask, good_mask)) {
 			slice_dbg(" fits good !\n");
 			return addr;
 		}
 	} else {
 		/* Now let's see if we can find something in the existing
 		 * slices for that size
 		 */
 		newaddr = slice_find_area(mm, len, good_mask, psize, topdown);
 		if (newaddr != -ENOMEM) {
 			/* Found within the good mask, we don't have to setup,
 			 * we thus return directly
 			 */
 			slice_dbg(" found area at 0x%lx\n", newaddr);
 			return newaddr;
 		}
 	}

 	/* We don't fit in the good mask, check what other slices are
 	 * empty and thus can be converted
 	 */
 	potential_mask = slice_mask_for_free(mm);
 	or_mask(potential_mask, good_mask);
 	slice_print_mask(" potential", potential_mask);

 	if ((addr != 0 || fixed) && slice_check_fit(mask, potential_mask)) {
 		slice_dbg(" fits potential !\n");
 		goto convert;
 	}

 	/* If we have MAP_FIXED and failed the above steps, then error out */
 	if (fixed)
 		return -EBUSY;

 	slice_dbg(" search...\n");

 	/* If we had a hint that didn't work out, see if we can fit
 	 * anywhere in the good area.
 	 */
 	if (addr) {
 		addr = slice_find_area(mm, len, good_mask, psize, topdown);
 		if (addr != -ENOMEM) {
 			slice_dbg(" found area at 0x%lx\n", addr);
 			return addr;
 		}
 	}

 	/* Now let's see if we can find something in the existing slices
 	 * for that size plus free slices
 	 */
 	addr = slice_find_area(mm, len, potential_mask, psize, topdown);

 #ifdef CONFIG_PPC_64K_PAGES
 	if (addr == -ENOMEM && psize == MMU_PAGE_64K) {
 		/* retry the search with 4k-page slices included */
 		or_mask(potential_mask, compat_mask);
 		addr = slice_find_area(mm, len, potential_mask, psize,
 				       topdown);
 	}
 #endif

 	if (addr == -ENOMEM)
 		return -ENOMEM;

 	mask = slice_range_to_mask(addr, len);
 	slice_dbg(" found potential area at 0x%lx\n", addr);
 	slice_print_mask(" mask", mask);

  convert:
 	andnot_mask(mask, good_mask);
 	andnot_mask(mask, compat_mask);
 	if (mask.low_slices || mask.high_slices) {
 		slice_convert(mm, mask, psize);
 		if (psize > MMU_PAGE_BASE)
 			on_each_cpu(slice_flush_segments, mm, 1);
 	}
 	return addr;

 }
 EXPORT_SYMBOL_GPL(slice_get_unmapped_area);

 unsigned long arch_get_unmapped_area(struct file *filp,
 				     unsigned long addr,
 				     unsigned long len,
 				     unsigned long pgoff,
 				     unsigned long flags)
 {
 	return slice_get_unmapped_area(addr, len, flags,
 				       current->mm->context.user_psize, 0);
 }

 unsigned long arch_get_unmapped_area_topdown(struct file *filp,
 					     const unsigned long addr0,
 					     const unsigned long len,
 					     const unsigned long pgoff,
 					     const unsigned long flags)
 {
 	return slice_get_unmapped_area(addr0, len, flags,
 				       current->mm->context.user_psize, 1);
 }

 unsigned int get_slice_psize(struct mm_struct *mm, unsigned long addr)
 {
 	unsigned char *hpsizes;
 	int index, mask_index;

 	if (addr < SLICE_LOW_TOP) {
 		u64 lpsizes;
 		lpsizes = mm->context.low_slices_psize;
 		index = GET_LOW_SLICE_INDEX(addr);
 		return (lpsizes >> (index * 4)) & 0xf;
 	}
 	hpsizes = mm->context.high_slices_psize;
 	index = GET_HIGH_SLICE_INDEX(addr);
 	mask_index = index & 0x1;
 	return (hpsizes[index >> 1] >> (mask_index * 4)) & 0xf;
 }
 EXPORT_SYMBOL_GPL(get_slice_psize);

 /*
  * This is called by hash_page when it needs to do a lazy conversion of
  * an address space from real 64K pages to combo 4K pages (typically
  * when hitting a non cacheable mapping on a processor or hypervisor
  * that won't allow them for 64K pages).
  *
  * This is also called in init_new_context() to change back the user
  * psize from whatever the parent context had it set to
  * N.B. This may be called before mm->context.id has been set.
  *
  * This function will only change the content of the {low,high)_slice_psize
  * masks, it will not flush SLBs as this shall be handled lazily by the
  * caller.
  */
 void slice_set_user_psize(struct mm_struct *mm, unsigned int psize)
 {
 	int index, mask_index;
 	unsigned char *hpsizes;
 	unsigned long flags, lpsizes;
 	unsigned int old_psize;
 	int i;

 	slice_dbg("slice_set_user_psize(mm=%p, psize=%d)\n", mm, psize);

 	spin_lock_irqsave(&slice_convert_lock, flags);

 	old_psize = mm->context.user_psize;
 	slice_dbg(" old_psize=%d\n", old_psize);
 	if (old_psize == psize)
 		goto bail;

 	mm->context.user_psize = psize;
 	wmb();

 	lpsizes = mm->context.low_slices_psize;
 	for (i = 0; i < SLICE_NUM_LOW; i++)
 		if (((lpsizes >> (i * 4)) & 0xf) == old_psize)
 			lpsizes = (lpsizes & ~(0xful << (i * 4))) |
 				(((unsigned long)psize) << (i * 4));
 	/* Assign the value back */
 	mm->context.low_slices_psize = lpsizes;

 	hpsizes = mm->context.high_slices_psize;
 	for (i = 0; i < SLICE_NUM_HIGH; i++) {
 		mask_index = i & 0x1;
 		index = i >> 1;
 		if (((hpsizes[index] >> (mask_index * 4)) & 0xf) == old_psize)
 			hpsizes[index] = (hpsizes[index] &
 					  ~(0xf << (mask_index * 4))) |
 				(((unsigned long)psize) << (mask_index * 4));
 	}


 	slice_dbg(" lsps=%lx, hsps=%lx\n",
 		  mm->context.low_slices_psize,
 		  mm->context.high_slices_psize);

  bail:
 	spin_unlock_irqrestore(&slice_convert_lock, flags);
 }

 void slice_set_range_psize(struct mm_struct *mm, unsigned long start,
 			   unsigned long len, unsigned int psize)
 {
 	struct slice_mask mask = slice_range_to_mask(start, len);

 	slice_convert(mm, mask, psize);
 }

 #ifdef CONFIG_HUGETLB_PAGE
 /*
  * is_hugepage_only_range() is used by generic code to verify whether
  * a normal mmap mapping (non hugetlbfs) is valid on a given area.
  *
  * until the generic code provides a more generic hook and/or starts
  * calling arch get_unmapped_area for MAP_FIXED (which our implementation
  * here knows how to deal with), we hijack it to keep standard mappings
  * away from us.
  *
  * because of that generic code limitation, MAP_FIXED mapping cannot
  * "convert" back a slice with no VMAs to the standard page size, only
  * get_unmapped_area() can. It would be possible to fix it here but I
  * prefer working on fixing the generic code instead.
  *
  * WARNING: This will not work if hugetlbfs isn't enabled since the
  * generic code will redefine that function as 0 in that. This is ok
  * for now as we only use slices with hugetlbfs enabled. This should
  * be fixed as the generic code gets fixed.
  */
 int is_hugepage_only_range(struct mm_struct *mm, unsigned long addr,
 			   unsigned long len)
 {
 	struct slice_mask mask, available;
 	unsigned int psize = mm->context.user_psize;

 	mask = slice_range_to_mask(addr, len);
 	available = slice_mask_for_size(mm, psize);
 #ifdef CONFIG_PPC_64K_PAGES
 	/* We need to account for 4k slices too */
 	if (psize == MMU_PAGE_64K) {
 		struct slice_mask compat_mask;
 		compat_mask = slice_mask_for_size(mm, MMU_PAGE_4K);
 		or_mask(available, compat_mask);
 	}
 #endif

 #if 0 /* too verbose */
 	slice_dbg("is_hugepage_only_range(mm=%p, addr=%lx, len=%lx)\n",
 		 mm, addr, len);
 	slice_print_mask(" mask", mask);
 	slice_print_mask(" available", available);
 #endif
 	return !slice_check_fit(mask, available);
 }
 #endif
	/*
	* address space "slices" (meta-segments) support
	*
	* Copyright (C) 2007 Benjamin Herrenschmidt, IBM Corporation.
	*
	* Based on hugetlb implementation
	*
	* Copyright (C) 2003 David Gibson, IBM Corporation.
	*
	* 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.
	*
	* 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, write to the Free Software
	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	*/

	#undef DEBUG

	#include <linux/kernel.h>
	#include <linux/mm.h>
	#include <linux/pagemap.h>
	#include <linux/err.h>
	#include <linux/spinlock.h>
	#include <linux/export.h>
	#include <linux/hugetlb.h>
	#include <asm/mman.h>
	#include <asm/mmu.h>
	#include <asm/copro.h>
	#include <asm/hugetlb.h>

	/* some sanity checks */
	#if (PGTABLE_RANGE >> 43) > SLICE_MASK_SIZE
	#error PGTABLE_RANGE exceeds slice_mask high_slices size
	#endif

	static DEFINE_SPINLOCK(slice_convert_lock);


	#ifdef DEBUG
	int _slice_debug = 1;

	static void slice_print_mask(const char *label, struct slice_mask mask)
	{
	char *p, buf[16 + 3 + 64 + 1];
	int i;

	if (!_slice_debug)
	return;
	p = buf;
	for (i = 0; i < SLICE_NUM_LOW; i++)
	*(p++) = (mask.low_slices & (1 << i)) ? '1' : '0';
	*(p++) = ' ';
	*(p++) = '-';
	*(p++) = ' ';
	for (i = 0; i < SLICE_NUM_HIGH; i++)
	*(p++) = (mask.high_slices & (1ul << i)) ? '1' : '0';
	*(p++) = 0;

	printk(KERN_DEBUG "%s:%s\n", label, buf);
	}

	#define slice_dbg(fmt...) do { if (_slice_debug) pr_debug(fmt); } while(0)

	#else

	static void slice_print_mask(const char *label, struct slice_mask mask) {}
	#define slice_dbg(fmt...)

	#endif

	static struct slice_mask slice_range_to_mask(unsigned long start,
	unsigned long len)
	{
	unsigned long end = start + len - 1;
	struct slice_mask ret = { 0, 0 };

	if (start < SLICE_LOW_TOP) {
	unsigned long mend = min(end, SLICE_LOW_TOP);
	unsigned long mstart = min(start, SLICE_LOW_TOP);

	ret.low_slices = (1u << (GET_LOW_SLICE_INDEX(mend) + 1))
	- (1u << GET_LOW_SLICE_INDEX(mstart));
	}

	if ((start + len) > SLICE_LOW_TOP)
	ret.high_slices = (1ul << (GET_HIGH_SLICE_INDEX(end) + 1))
	- (1ul << GET_HIGH_SLICE_INDEX(start));

	return ret;
	}

	static int slice_area_is_free(struct mm_struct *mm, unsigned long addr,
	unsigned long len)
	{
	struct vm_area_struct *vma;

	if ((mm->task_size - len) < addr)
	return 0;
	vma = find_vma(mm, addr);
	return (!vma \|\| (addr + len) <= vma->vm_start);
	}

	static int slice_low_has_vma(struct mm_struct *mm, unsigned long slice)
	{
	return !slice_area_is_free(mm, slice << SLICE_LOW_SHIFT,
	1ul << SLICE_LOW_SHIFT);
	}

	static int slice_high_has_vma(struct mm_struct *mm, unsigned long slice)
	{
	unsigned long start = slice << SLICE_HIGH_SHIFT;
	unsigned long end = start + (1ul << SLICE_HIGH_SHIFT);

	/* Hack, so that each addresses is controlled by exactly one
	* of the high or low area bitmaps, the first high area starts
	* at 4GB, not 0 */
	if (start == 0)
	start = SLICE_LOW_TOP;

	return !slice_area_is_free(mm, start, end - start);
	}

	static struct slice_mask slice_mask_for_free(struct mm_struct *mm)
	{
	struct slice_mask ret = { 0, 0 };
	unsigned long i;

	for (i = 0; i < SLICE_NUM_LOW; i++)
	if (!slice_low_has_vma(mm, i))
	ret.low_slices \|= 1u << i;

	if (mm->task_size <= SLICE_LOW_TOP)
	return ret;

	for (i = 0; i < SLICE_NUM_HIGH; i++)
	if (!slice_high_has_vma(mm, i))
	ret.high_slices \|= 1ul << i;

	return ret;
	}

	static struct slice_mask slice_mask_for_size(struct mm_struct *mm, int psize)
	{
	unsigned char *hpsizes;
	int index, mask_index;
	struct slice_mask ret = { 0, 0 };
	unsigned long i;
	u64 lpsizes;

	lpsizes = mm->context.low_slices_psize;
	for (i = 0; i < SLICE_NUM_LOW; i++)
	if (((lpsizes >> (i * 4)) & 0xf) == psize)
	ret.low_slices \|= 1u << i;

	hpsizes = mm->context.high_slices_psize;
	for (i = 0; i < SLICE_NUM_HIGH; i++) {
	mask_index = i & 0x1;
	index = i >> 1;
	if (((hpsizes[index] >> (mask_index * 4)) & 0xf) == psize)
	ret.high_slices \|= 1ul << i;
	}

	return ret;
	}

	static int slice_check_fit(struct slice_mask mask, struct slice_mask available)
	{
	return (mask.low_slices & available.low_slices) == mask.low_slices &&
	(mask.high_slices & available.high_slices) == mask.high_slices;
	}

	static void slice_flush_segments(void *parm)
	{
	struct mm_struct *mm = parm;
	unsigned long flags;

	if (mm != current->active_mm)
	return;

	/* update the paca copy of the context struct */
	get_paca()->context = current->active_mm->context;

	local_irq_save(flags);
	slb_flush_and_rebolt();
	local_irq_restore(flags);
	}

	static void slice_convert(struct mm_struct *mm, struct slice_mask mask, int psize)
	{
	int index, mask_index;
	/* Write the new slice psize bits */
	unsigned char *hpsizes;
	u64 lpsizes;
	unsigned long i, flags;

	slice_dbg("slice_convert(mm=%p, psize=%d)\n", mm, psize);
	slice_print_mask(" mask", mask);

	/* We need to use a spinlock here to protect against
	* concurrent 64k -> 4k demotion ...
	*/
	spin_lock_irqsave(&slice_convert_lock, flags);

	lpsizes = mm->context.low_slices_psize;
	for (i = 0; i < SLICE_NUM_LOW; i++)
	if (mask.low_slices & (1u << i))
	lpsizes = (lpsizes & ~(0xful << (i * 4))) \|
	(((unsigned long)psize) << (i * 4));

	/* Assign the value back */
	mm->context.low_slices_psize = lpsizes;

	hpsizes = mm->context.high_slices_psize;
	for (i = 0; i < SLICE_NUM_HIGH; i++) {
	mask_index = i & 0x1;
	index = i >> 1;
	if (mask.high_slices & (1ul << i))
	hpsizes[index] = (hpsizes[index] &
	~(0xf << (mask_index * 4))) \|
	(((unsigned long)psize) << (mask_index * 4));
	}

	slice_dbg(" lsps=%lx, hsps=%lx\n",
	mm->context.low_slices_psize,
	mm->context.high_slices_psize);

	spin_unlock_irqrestore(&slice_convert_lock, flags);

	copro_flush_all_slbs(mm);
	}

	/*
	* Compute which slice addr is part of;
	* set *boundary_addr to the start or end boundary of that slice
	* (depending on 'end' parameter);
	* return boolean indicating if the slice is marked as available in the
	* 'available' slice_mark.
	*/
	static bool slice_scan_available(unsigned long addr,
	struct slice_mask available,
	int end,
	unsigned long *boundary_addr)
	{
	unsigned long slice;
	if (addr < SLICE_LOW_TOP) {
	slice = GET_LOW_SLICE_INDEX(addr);
	*boundary_addr = (slice + end) << SLICE_LOW_SHIFT;
	return !!(available.low_slices & (1u << slice));
	} else {
	slice = GET_HIGH_SLICE_INDEX(addr);
	*boundary_addr = (slice + end) ?
	((slice + end) << SLICE_HIGH_SHIFT) : SLICE_LOW_TOP;
	return !!(available.high_slices & (1ul << slice));
	}
	}

	static unsigned long slice_find_area_bottomup(struct mm_struct *mm,
	unsigned long len,
	struct slice_mask available,
	int psize)
	{
	int pshift = max_t(int, mmu_psize_defs[psize].shift, PAGE_SHIFT);
	unsigned long addr, found, next_end;
	struct vm_unmapped_area_info info;

	info.flags = 0;
	info.length = len;
	info.align_mask = PAGE_MASK & ((1ul << pshift) - 1);
	info.align_offset = 0;

	addr = TASK_UNMAPPED_BASE;
	while (addr < TASK_SIZE) {
	info.low_limit = addr;
	if (!slice_scan_available(addr, available, 1, &addr))
	continue;

	next_slice:
	/*
	* At this point [info.low_limit; addr) covers
	* available slices only and ends at a slice boundary.
	* Check if we need to reduce the range, or if we can
	* extend it to cover the next available slice.
	*/
	if (addr >= TASK_SIZE)
	addr = TASK_SIZE;
	else if (slice_scan_available(addr, available, 1, &next_end)) {
	addr = next_end;
	goto next_slice;
	}
	info.high_limit = addr;

	found = vm_unmapped_area(&info);
	if (!(found & ~PAGE_MASK))
	return found;
	}

	return -ENOMEM;
	}

	static unsigned long slice_find_area_topdown(struct mm_struct *mm,
	unsigned long len,
	struct slice_mask available,
	int psize)
	{
	int pshift = max_t(int, mmu_psize_defs[psize].shift, PAGE_SHIFT);
	unsigned long addr, found, prev;
	struct vm_unmapped_area_info info;

	info.flags = VM_UNMAPPED_AREA_TOPDOWN;
	info.length = len;
	info.align_mask = PAGE_MASK & ((1ul << pshift) - 1);
	info.align_offset = 0;

	addr = mm->mmap_base;
	while (addr > PAGE_SIZE) {
	info.high_limit = addr;
	if (!slice_scan_available(addr - 1, available, 0, &addr))
	continue;

	prev_slice:
	/*
	* At this point [addr; info.high_limit) covers
	* available slices only and starts at a slice boundary.
	* Check if we need to reduce the range, or if we can
	* extend it to cover the previous available slice.
	*/
	if (addr < PAGE_SIZE)
	addr = PAGE_SIZE;
	else if (slice_scan_available(addr - 1, available, 0, &prev)) {
	addr = prev;
	goto prev_slice;
	}
	info.low_limit = addr;

	found = vm_unmapped_area(&info);
	if (!(found & ~PAGE_MASK))
	return found;
	}

	/*
	* A failed mmap() very likely causes application failure,
	* so fall back to the bottom-up function here. This scenario
	* can happen with large stack limits and large mmap()
	* allocations.
	*/
	return slice_find_area_bottomup(mm, len, available, psize);
	}


	static unsigned long slice_find_area(struct mm_struct *mm, unsigned long len,
	struct slice_mask mask, int psize,
	int topdown)
	{
	if (topdown)
	return slice_find_area_topdown(mm, len, mask, psize);
	else
	return slice_find_area_bottomup(mm, len, mask, psize);
	}

	#define or_mask(dst, src) do { \
	(dst).low_slices \|= (src).low_slices; \
	(dst).high_slices \|= (src).high_slices; \
	} while (0)

	#define andnot_mask(dst, src) do { \
	(dst).low_slices &= ~(src).low_slices; \
	(dst).high_slices &= ~(src).high_slices; \
	} while (0)

	#ifdef CONFIG_PPC_64K_PAGES
	#define MMU_PAGE_BASE MMU_PAGE_64K
	#else
	#define MMU_PAGE_BASE MMU_PAGE_4K
	#endif

	unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
	unsigned long flags, unsigned int psize,
	int topdown)
	{
	struct slice_mask mask = {0, 0};
	struct slice_mask good_mask;
	struct slice_mask potential_mask = {0,0} /* silence stupid warning */;
	struct slice_mask compat_mask = {0, 0};
	int fixed = (flags & MAP_FIXED);
	int pshift = max_t(int, mmu_psize_defs[psize].shift, PAGE_SHIFT);
	struct mm_struct *mm = current->mm;
	unsigned long newaddr;

	/* Sanity checks */
	BUG_ON(mm->task_size == 0);

	slice_dbg("slice_get_unmapped_area(mm=%p, psize=%d...\n", mm, psize);
	slice_dbg(" addr=%lx, len=%lx, flags=%lx, topdown=%d\n",
	addr, len, flags, topdown);

	if (len > mm->task_size)
	return -ENOMEM;
	if (len & ((1ul << pshift) - 1))
	return -EINVAL;
	if (fixed && (addr & ((1ul << pshift) - 1)))
	return -EINVAL;
	if (fixed && addr > (mm->task_size - len))
	return -ENOMEM;

	/* If hint, make sure it matches our alignment restrictions */
	if (!fixed && addr) {
	addr = _ALIGN_UP(addr, 1ul << pshift);
	slice_dbg(" aligned addr=%lx\n", addr);
	/* Ignore hint if it's too large or overlaps a VMA */
	if (addr > mm->task_size - len \|\|
	!slice_area_is_free(mm, addr, len))
	addr = 0;
	}

	/* First make up a "good" mask of slices that have the right size
	* already
	*/
	good_mask = slice_mask_for_size(mm, psize);
	slice_print_mask(" good_mask", good_mask);

	/*
	* Here "good" means slices that are already the right page size,
	* "compat" means slices that have a compatible page size (i.e.
	* 4k in a 64k pagesize kernel), and "free" means slices without
	* any VMAs.
	*
	* If MAP_FIXED:
	* check if fits in good \| compat => OK
	* check if fits in good \| compat \| free => convert free
	* else bad
	* If have hint:
	* check if hint fits in good => OK
	* check if hint fits in good \| free => convert free
	* Otherwise:
	* search in good, found => OK
	* search in good \| free, found => convert free
	* search in good \| compat \| free, found => convert free.
	*/

	#ifdef CONFIG_PPC_64K_PAGES
	/* If we support combo pages, we can allow 64k pages in 4k slices */
	if (psize == MMU_PAGE_64K) {
	compat_mask = slice_mask_for_size(mm, MMU_PAGE_4K);
	if (fixed)
	or_mask(good_mask, compat_mask);
	}
	#endif

	/* First check hint if it's valid or if we have MAP_FIXED */
	if (addr != 0 \|\| fixed) {
	/* Build a mask for the requested range */
	mask = slice_range_to_mask(addr, len);
	slice_print_mask(" mask", mask);

	/* Check if we fit in the good mask. If we do, we just return,
	* nothing else to do
	*/
	if (slice_check_fit(mask, good_mask)) {
	slice_dbg(" fits good !\n");
	return addr;
	}
	} else {
	/* Now let's see if we can find something in the existing
	* slices for that size
	*/
	newaddr = slice_find_area(mm, len, good_mask, psize, topdown);
	if (newaddr != -ENOMEM) {
	/* Found within the good mask, we don't have to setup,
	* we thus return directly
	*/
	slice_dbg(" found area at 0x%lx\n", newaddr);
	return newaddr;
	}
	}

	/* We don't fit in the good mask, check what other slices are
	* empty and thus can be converted
	*/
	potential_mask = slice_mask_for_free(mm);
	or_mask(potential_mask, good_mask);
	slice_print_mask(" potential", potential_mask);

	if ((addr != 0 \|\| fixed) && slice_check_fit(mask, potential_mask)) {
	slice_dbg(" fits potential !\n");
	goto convert;
	}

	/* If we have MAP_FIXED and failed the above steps, then error out */
	if (fixed)
	return -EBUSY;

	slice_dbg(" search...\n");

	/* If we had a hint that didn't work out, see if we can fit
	* anywhere in the good area.
	*/
	if (addr) {
	addr = slice_find_area(mm, len, good_mask, psize, topdown);
	if (addr != -ENOMEM) {
	slice_dbg(" found area at 0x%lx\n", addr);
	return addr;
	}
	}

	/* Now let's see if we can find something in the existing slices
	* for that size plus free slices
	*/
	addr = slice_find_area(mm, len, potential_mask, psize, topdown);

	#ifdef CONFIG_PPC_64K_PAGES
	if (addr == -ENOMEM && psize == MMU_PAGE_64K) {
	/* retry the search with 4k-page slices included */
	or_mask(potential_mask, compat_mask);
	addr = slice_find_area(mm, len, potential_mask, psize,
	topdown);
	}
	#endif

	if (addr == -ENOMEM)
	return -ENOMEM;

	mask = slice_range_to_mask(addr, len);
	slice_dbg(" found potential area at 0x%lx\n", addr);
	slice_print_mask(" mask", mask);

	convert:
	andnot_mask(mask, good_mask);
	andnot_mask(mask, compat_mask);
	if (mask.low_slices \|\| mask.high_slices) {
	slice_convert(mm, mask, psize);
	if (psize > MMU_PAGE_BASE)
	on_each_cpu(slice_flush_segments, mm, 1);
	}
	return addr;

	}
	EXPORT_SYMBOL_GPL(slice_get_unmapped_area);

	unsigned long arch_get_unmapped_area(struct file *filp,
	unsigned long addr,
	unsigned long len,
	unsigned long pgoff,
	unsigned long flags)
	{
	return slice_get_unmapped_area(addr, len, flags,
	current->mm->context.user_psize, 0);
	}

	unsigned long arch_get_unmapped_area_topdown(struct file *filp,
	const unsigned long addr0,
	const unsigned long len,
	const unsigned long pgoff,
	const unsigned long flags)
	{
	return slice_get_unmapped_area(addr0, len, flags,
	current->mm->context.user_psize, 1);
	}

	unsigned int get_slice_psize(struct mm_struct *mm, unsigned long addr)
	{
	unsigned char *hpsizes;
	int index, mask_index;

	if (addr < SLICE_LOW_TOP) {
	u64 lpsizes;
	lpsizes = mm->context.low_slices_psize;
	index = GET_LOW_SLICE_INDEX(addr);
	return (lpsizes >> (index * 4)) & 0xf;
	}
	hpsizes = mm->context.high_slices_psize;
	index = GET_HIGH_SLICE_INDEX(addr);
	mask_index = index & 0x1;
	return (hpsizes[index >> 1] >> (mask_index * 4)) & 0xf;
	}
	EXPORT_SYMBOL_GPL(get_slice_psize);

	/*
	* This is called by hash_page when it needs to do a lazy conversion of
	* an address space from real 64K pages to combo 4K pages (typically
	* when hitting a non cacheable mapping on a processor or hypervisor
	* that won't allow them for 64K pages).
	*
	* This is also called in init_new_context() to change back the user
	* psize from whatever the parent context had it set to
	* N.B. This may be called before mm->context.id has been set.
	*
	* This function will only change the content of the {low,high)_slice_psize
	* masks, it will not flush SLBs as this shall be handled lazily by the
	* caller.
	*/
	void slice_set_user_psize(struct mm_struct *mm, unsigned int psize)
	{
	int index, mask_index;
	unsigned char *hpsizes;
	unsigned long flags, lpsizes;
	unsigned int old_psize;
	int i;

	slice_dbg("slice_set_user_psize(mm=%p, psize=%d)\n", mm, psize);

	spin_lock_irqsave(&slice_convert_lock, flags);

	old_psize = mm->context.user_psize;
	slice_dbg(" old_psize=%d\n", old_psize);
	if (old_psize == psize)
	goto bail;

	mm->context.user_psize = psize;
	wmb();

	lpsizes = mm->context.low_slices_psize;
	for (i = 0; i < SLICE_NUM_LOW; i++)
	if (((lpsizes >> (i * 4)) & 0xf) == old_psize)
	lpsizes = (lpsizes & ~(0xful << (i * 4))) \|
	(((unsigned long)psize) << (i * 4));
	/* Assign the value back */
	mm->context.low_slices_psize = lpsizes;

	hpsizes = mm->context.high_slices_psize;
	for (i = 0; i < SLICE_NUM_HIGH; i++) {
	mask_index = i & 0x1;
	index = i >> 1;
	if (((hpsizes[index] >> (mask_index * 4)) & 0xf) == old_psize)
	hpsizes[index] = (hpsizes[index] &
	~(0xf << (mask_index * 4))) \|
	(((unsigned long)psize) << (mask_index * 4));
	}




	slice_dbg(" lsps=%lx, hsps=%lx\n",
	mm->context.low_slices_psize,
	mm->context.high_slices_psize);

	bail:
	spin_unlock_irqrestore(&slice_convert_lock, flags);
	}

	void slice_set_range_psize(struct mm_struct *mm, unsigned long start,
	unsigned long len, unsigned int psize)
	{
	struct slice_mask mask = slice_range_to_mask(start, len);

	slice_convert(mm, mask, psize);
	}

	#ifdef CONFIG_HUGETLB_PAGE
	/*
	* is_hugepage_only_range() is used by generic code to verify whether
	* a normal mmap mapping (non hugetlbfs) is valid on a given area.
	*
	* until the generic code provides a more generic hook and/or starts
	* calling arch get_unmapped_area for MAP_FIXED (which our implementation
	* here knows how to deal with), we hijack it to keep standard mappings
	* away from us.
	*
	* because of that generic code limitation, MAP_FIXED mapping cannot
	* "convert" back a slice with no VMAs to the standard page size, only
	* get_unmapped_area() can. It would be possible to fix it here but I
	* prefer working on fixing the generic code instead.
	*
	* WARNING: This will not work if hugetlbfs isn't enabled since the
	* generic code will redefine that function as 0 in that. This is ok
	* for now as we only use slices with hugetlbfs enabled. This should
	* be fixed as the generic code gets fixed.
	*/
	int is_hugepage_only_range(struct mm_struct *mm, unsigned long addr,
	unsigned long len)
	{
	struct slice_mask mask, available;
	unsigned int psize = mm->context.user_psize;

	mask = slice_range_to_mask(addr, len);
	available = slice_mask_for_size(mm, psize);
	#ifdef CONFIG_PPC_64K_PAGES
	/* We need to account for 4k slices too */
	if (psize == MMU_PAGE_64K) {
	struct slice_mask compat_mask;
	compat_mask = slice_mask_for_size(mm, MMU_PAGE_4K);
	or_mask(available, compat_mask);
	}
	#endif

	#if 0 /* too verbose */
	slice_dbg("is_hugepage_only_range(mm=%p, addr=%lx, len=%lx)\n",
	mm, addr, len);
	slice_print_mask(" mask", mask);
	slice_print_mask(" available", available);
	#endif
	return !slice_check_fit(mask, available);
	}
	#endif