arch/powerpc/mm/hugetlbpage.c - kernel/msm-4.9 - Gitiles

 /*
  * PPC64 (POWER4) Huge TLB Page Support for Kernel.
  *
  * Copyright (C) 2003 David Gibson, IBM Corporation.
  *
  * Based on the IA-32 version:
  * Copyright (C) 2002, Rohit Seth <rohit.seth@intel.com>
  */

 #include <linux/init.h>
 #include <linux/fs.h>
 #include <linux/mm.h>
 #include <linux/hugetlb.h>
 #include <linux/pagemap.h>
 #include <linux/smp_lock.h>
 #include <linux/slab.h>
 #include <linux/err.h>
 #include <linux/sysctl.h>
 #include <asm/mman.h>
 #include <asm/pgalloc.h>
 #include <asm/tlb.h>
 #include <asm/tlbflush.h>
 #include <asm/mmu_context.h>
 #include <asm/machdep.h>
 #include <asm/cputable.h>
 #include <asm/tlb.h>

 #include <linux/sysctl.h>

 #define NUM_LOW_AREAS	(0x100000000UL >> SID_SHIFT)
 #define NUM_HIGH_AREAS	(PGTABLE_RANGE >> HTLB_AREA_SHIFT)

 /* Modelled after find_linux_pte() */
 pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
 {
 	pgd_t *pg;
 	pud_t *pu;
 	pmd_t *pm;
 	pte_t *pt;

 	BUG_ON(! in_hugepage_area(mm->context, addr));

 	addr &= HPAGE_MASK;

 	pg = pgd_offset(mm, addr);
 	if (!pgd_none(*pg)) {
 		pu = pud_offset(pg, addr);
 		if (!pud_none(*pu)) {
 			pm = pmd_offset(pu, addr);
 #ifdef CONFIG_PPC_64K_PAGES
 			/* Currently, we use the normal PTE offset within full
 			 * size PTE pages, thus our huge PTEs are scattered in
 			 * the PTE page and we do waste some. We may change
 			 * that in the future, but the current mecanism keeps
 			 * things much simpler
 			 */
 			if (!pmd_none(*pm)) {
 				/* Note: pte_offset_* are all equivalent on
 				 * ppc64 as we don't have HIGHMEM
 				 */
 				pt = pte_offset_kernel(pm, addr);
 				return pt;
 			}
 #else /* CONFIG_PPC_64K_PAGES */
 			/* On 4k pages, we put huge PTEs in the PMD page */
 			pt = (pte_t *)pm;
 			return pt;
 #endif /* CONFIG_PPC_64K_PAGES */
 		}
 	}

 	return NULL;
 }

 pte_t *huge_pte_alloc(struct mm_struct *mm, unsigned long addr)
 {
 	pgd_t *pg;
 	pud_t *pu;
 	pmd_t *pm;
 	pte_t *pt;

 	BUG_ON(! in_hugepage_area(mm->context, addr));

 	addr &= HPAGE_MASK;

 	pg = pgd_offset(mm, addr);
 	pu = pud_alloc(mm, pg, addr);

 	if (pu) {
 		pm = pmd_alloc(mm, pu, addr);
 		if (pm) {
 #ifdef CONFIG_PPC_64K_PAGES
 			/* See comment in huge_pte_offset. Note that if we ever
 			 * want to put the page size in the PMD, we would have
 			 * to open code our own pte_alloc* function in order
 			 * to populate and set the size atomically
 			 */
 			pt = pte_alloc_map(mm, pm, addr);
 #else /* CONFIG_PPC_64K_PAGES */
 			pt = (pte_t *)pm;
 #endif /* CONFIG_PPC_64K_PAGES */
 			return pt;
 		}
 	}

 	return NULL;
 }

 void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
 		     pte_t *ptep, pte_t pte)
 {
 	if (pte_present(*ptep)) {
 		/* We open-code pte_clear because we need to pass the right
 		 * argument to hpte_update (huge / !huge)
 		 */
 		unsigned long old = pte_update(ptep, ~0UL);
 		if (old & _PAGE_HASHPTE)
 			hpte_update(mm, addr & HPAGE_MASK, ptep, old, 1);
 		flush_tlb_pending();
 	}
 	*ptep = __pte(pte_val(pte) & ~_PAGE_HPTEFLAGS);
 }

 pte_t huge_ptep_get_and_clear(struct mm_struct *mm, unsigned long addr,
 			      pte_t *ptep)
 {
 	unsigned long old = pte_update(ptep, ~0UL);

 	if (old & _PAGE_HASHPTE)
 		hpte_update(mm, addr & HPAGE_MASK, ptep, old, 1);
 	*ptep = __pte(0);

 	return __pte(old);
 }

 /*
  * This function checks for proper alignment of input addr and len parameters.
  */
 int is_aligned_hugepage_range(unsigned long addr, unsigned long len)
 {
 	if (len & ~HPAGE_MASK)
 		return -EINVAL;
 	if (addr & ~HPAGE_MASK)
 		return -EINVAL;
 	if (! (within_hugepage_low_range(addr, len)
 	       || within_hugepage_high_range(addr, len)) )
 		return -EINVAL;
 	return 0;
 }

 struct slb_flush_info {
 	struct mm_struct *mm;
 	u16 newareas;
 };

 static void flush_low_segments(void *parm)
 {
 	struct slb_flush_info *fi = parm;
 	unsigned long i;

 	BUILD_BUG_ON((sizeof(fi->newareas)*8) != NUM_LOW_AREAS);

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

 	/* Only need to do anything if this CPU is working in the same
 	 * mm as the one which has changed */

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

 	asm volatile("isync" : : : "memory");
 	for (i = 0; i < NUM_LOW_AREAS; i++) {
 		if (! (fi->newareas & (1U << i)))
 			continue;
 		asm volatile("slbie %0"
 			     : : "r" ((i << SID_SHIFT) | SLBIE_C));
 	}
 	asm volatile("isync" : : : "memory");
 }

 static void flush_high_segments(void *parm)
 {
 	struct slb_flush_info *fi = parm;
 	unsigned long i, j;


 	BUILD_BUG_ON((sizeof(fi->newareas)*8) != NUM_HIGH_AREAS);

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

 	/* Only need to do anything if this CPU is working in the same
 	 * mm as the one which has changed */

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

 	asm volatile("isync" : : : "memory");
 	for (i = 0; i < NUM_HIGH_AREAS; i++) {
 		if (! (fi->newareas & (1U << i)))
 			continue;
 		for (j = 0; j < (1UL << (HTLB_AREA_SHIFT-SID_SHIFT)); j++)
 			asm volatile("slbie %0"
 				     :: "r" (((i << HTLB_AREA_SHIFT)
 					      + (j << SID_SHIFT)) | SLBIE_C));
 	}
 	asm volatile("isync" : : : "memory");
 }

 static int prepare_low_area_for_htlb(struct mm_struct *mm, unsigned long area)
 {
 	unsigned long start = area << SID_SHIFT;
 	unsigned long end = (area+1) << SID_SHIFT;
 	struct vm_area_struct *vma;

 	BUG_ON(area >= NUM_LOW_AREAS);

 	/* Check no VMAs are in the region */
 	vma = find_vma(mm, start);
 	if (vma && (vma->vm_start < end))
 		return -EBUSY;

 	return 0;
 }

 static int prepare_high_area_for_htlb(struct mm_struct *mm, unsigned long area)
 {
 	unsigned long start = area << HTLB_AREA_SHIFT;
 	unsigned long end = (area+1) << HTLB_AREA_SHIFT;
 	struct vm_area_struct *vma;

 	BUG_ON(area >= NUM_HIGH_AREAS);

 	/* 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 = 0x100000000UL;

 	/* Check no VMAs are in the region */
 	vma = find_vma(mm, start);
 	if (vma && (vma->vm_start < end))
 		return -EBUSY;

 	return 0;
 }

 static int open_low_hpage_areas(struct mm_struct *mm, u16 newareas)
 {
 	unsigned long i;
 	struct slb_flush_info fi;

 	BUILD_BUG_ON((sizeof(newareas)*8) != NUM_LOW_AREAS);
 	BUILD_BUG_ON((sizeof(mm->context.low_htlb_areas)*8) != NUM_LOW_AREAS);

 	newareas &= ~(mm->context.low_htlb_areas);
 	if (! newareas)
 		return 0; /* The segments we want are already open */

 	for (i = 0; i < NUM_LOW_AREAS; i++)
 		if ((1 << i) & newareas)
 			if (prepare_low_area_for_htlb(mm, i) != 0)
 				return -EBUSY;

 	mm->context.low_htlb_areas |= newareas;

 	/* the context change must make it to memory before the flush,
 	 * so that further SLB misses do the right thing. */
 	mb();

 	fi.mm = mm;
 	fi.newareas = newareas;
 	on_each_cpu(flush_low_segments, &fi, 0, 1);

 	return 0;
 }

 static int open_high_hpage_areas(struct mm_struct *mm, u16 newareas)
 {
 	struct slb_flush_info fi;
 	unsigned long i;

 	BUILD_BUG_ON((sizeof(newareas)*8) != NUM_HIGH_AREAS);
 	BUILD_BUG_ON((sizeof(mm->context.high_htlb_areas)*8)
 		     != NUM_HIGH_AREAS);

 	newareas &= ~(mm->context.high_htlb_areas);
 	if (! newareas)
 		return 0; /* The areas we want are already open */

 	for (i = 0; i < NUM_HIGH_AREAS; i++)
 		if ((1 << i) & newareas)
 			if (prepare_high_area_for_htlb(mm, i) != 0)
 				return -EBUSY;

 	mm->context.high_htlb_areas |= newareas;

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

 	/* the context change must make it to memory before the flush,
 	 * so that further SLB misses do the right thing. */
 	mb();

 	fi.mm = mm;
 	fi.newareas = newareas;
 	on_each_cpu(flush_high_segments, &fi, 0, 1);

 	return 0;
 }

 int prepare_hugepage_range(unsigned long addr, unsigned long len)
 {
 	int err = 0;

 	if ( (addr+len) < addr )
 		return -EINVAL;

 	if (addr < 0x100000000UL)
 		err = open_low_hpage_areas(current->mm,
 					  LOW_ESID_MASK(addr, len));
 	if ((addr + len) > 0x100000000UL)
 		err = open_high_hpage_areas(current->mm,
 					    HTLB_AREA_MASK(addr, len));
 	if (err) {
 		printk(KERN_DEBUG "prepare_hugepage_range(%lx, %lx)"
 		       " failed (lowmask: 0x%04hx, highmask: 0x%04hx)\n",
 		       addr, len,
 		       LOW_ESID_MASK(addr, len), HTLB_AREA_MASK(addr, len));
 		return err;
 	}

 	return 0;
 }

 struct page *
 follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
 {
 	pte_t *ptep;
 	struct page *page;

 	if (! in_hugepage_area(mm->context, address))
 		return ERR_PTR(-EINVAL);

 	ptep = huge_pte_offset(mm, address);
 	page = pte_page(*ptep);
 	if (page)
 		page += (address % HPAGE_SIZE) / PAGE_SIZE;

 	return page;
 }

 int pmd_huge(pmd_t pmd)
 {
 	return 0;
 }

 struct page *
 follow_huge_pmd(struct mm_struct *mm, unsigned long address,
 		pmd_t *pmd, int write)
 {
 	BUG();
 	return NULL;
 }

 /* Because we have an exclusive hugepage region which lies within the
  * normal user address space, we have to take special measures to make
  * non-huge mmap()s evade the hugepage reserved regions. */
 unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,
 				     unsigned long len, unsigned long pgoff,
 				     unsigned long flags)
 {
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma;
 	unsigned long start_addr;

 	if (len > TASK_SIZE)
 		return -ENOMEM;

 	if (addr) {
 		addr = PAGE_ALIGN(addr);
 		vma = find_vma(mm, addr);
 		if (((TASK_SIZE - len) >= addr)
 		    && (!vma || (addr+len) <= vma->vm_start)
 		    && !is_hugepage_only_range(mm, addr,len))
 			return addr;
 	}
 	if (len > mm->cached_hole_size) {
 	        start_addr = addr = mm->free_area_cache;
 	} else {
 	        start_addr = addr = TASK_UNMAPPED_BASE;
 	        mm->cached_hole_size = 0;
 	}

 full_search:
 	vma = find_vma(mm, addr);
 	while (TASK_SIZE - len >= addr) {
 		BUG_ON(vma && (addr >= vma->vm_end));

 		if (touches_hugepage_low_range(mm, addr, len)) {
 			addr = ALIGN(addr+1, 1<<SID_SHIFT);
 			vma = find_vma(mm, addr);
 			continue;
 		}
 		if (touches_hugepage_high_range(mm, addr, len)) {
 			addr = ALIGN(addr+1, 1UL<<HTLB_AREA_SHIFT);
 			vma = find_vma(mm, addr);
 			continue;
 		}
 		if (!vma || addr + len <= vma->vm_start) {
 			/*
 			 * Remember the place where we stopped the search:
 			 */
 			mm->free_area_cache = addr + len;
 			return addr;
 		}
 		if (addr + mm->cached_hole_size < vma->vm_start)
 		        mm->cached_hole_size = vma->vm_start - addr;
 		addr = vma->vm_end;
 		vma = vma->vm_next;
 	}

 	/* Make sure we didn't miss any holes */
 	if (start_addr != TASK_UNMAPPED_BASE) {
 		start_addr = addr = TASK_UNMAPPED_BASE;
 		mm->cached_hole_size = 0;
 		goto full_search;
 	}
 	return -ENOMEM;
 }

 /*
  * This mmap-allocator allocates new areas top-down from below the
  * stack's low limit (the base):
  *
  * Because we have an exclusive hugepage region which lies within the
  * normal user address space, we have to take special measures to make
  * non-huge mmap()s evade the hugepage reserved regions.
  */
 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)
 {
 	struct vm_area_struct *vma, *prev_vma;
 	struct mm_struct *mm = current->mm;
 	unsigned long base = mm->mmap_base, addr = addr0;
 	unsigned long largest_hole = mm->cached_hole_size;
 	int first_time = 1;

 	/* requested length too big for entire address space */
 	if (len > TASK_SIZE)
 		return -ENOMEM;

 	/* dont allow allocations above current base */
 	if (mm->free_area_cache > base)
 		mm->free_area_cache = base;

 	/* requesting a specific address */
 	if (addr) {
 		addr = PAGE_ALIGN(addr);
 		vma = find_vma(mm, addr);
 		if (TASK_SIZE - len >= addr &&
 				(!vma || addr + len <= vma->vm_start)
 				&& !is_hugepage_only_range(mm, addr,len))
 			return addr;
 	}

 	if (len <= largest_hole) {
 	        largest_hole = 0;
 		mm->free_area_cache = base;
 	}
 try_again:
 	/* make sure it can fit in the remaining address space */
 	if (mm->free_area_cache < len)
 		goto fail;

 	/* either no address requested or cant fit in requested address hole */
 	addr = (mm->free_area_cache - len) & PAGE_MASK;
 	do {
 hugepage_recheck:
 		if (touches_hugepage_low_range(mm, addr, len)) {
 			addr = (addr & ((~0) << SID_SHIFT)) - len;
 			goto hugepage_recheck;
 		} else if (touches_hugepage_high_range(mm, addr, len)) {
 			addr = (addr & ((~0UL) << HTLB_AREA_SHIFT)) - len;
 			goto hugepage_recheck;
 		}

 		/*
 		 * Lookup failure means no vma is above this address,
 		 * i.e. return with success:
 		 */
  	 	if (!(vma = find_vma_prev(mm, addr, &prev_vma)))
 			return addr;

 		/*
 		 * new region fits between prev_vma->vm_end and
 		 * vma->vm_start, use it:
 		 */
 		if (addr+len <= vma->vm_start &&
 		          (!prev_vma || (addr >= prev_vma->vm_end))) {
 			/* remember the address as a hint for next time */
 		        mm->cached_hole_size = largest_hole;
 		        return (mm->free_area_cache = addr);
 		} else {
 			/* pull free_area_cache down to the first hole */
 		        if (mm->free_area_cache == vma->vm_end) {
 				mm->free_area_cache = vma->vm_start;
 				mm->cached_hole_size = largest_hole;
 			}
 		}

 		/* remember the largest hole we saw so far */
 		if (addr + largest_hole < vma->vm_start)
 		        largest_hole = vma->vm_start - addr;

 		/* try just below the current vma->vm_start */
 		addr = vma->vm_start-len;
 	} while (len <= vma->vm_start);

 fail:
 	/*
 	 * if hint left us with no space for the requested
 	 * mapping then try again:
 	 */
 	if (first_time) {
 		mm->free_area_cache = base;
 		largest_hole = 0;
 		first_time = 0;
 		goto try_again;
 	}
 	/*
 	 * 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.
 	 */
 	mm->free_area_cache = TASK_UNMAPPED_BASE;
 	mm->cached_hole_size = ~0UL;
 	addr = arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
 	/*
 	 * Restore the topdown base:
 	 */
 	mm->free_area_cache = base;
 	mm->cached_hole_size = ~0UL;

 	return addr;
 }

 static int htlb_check_hinted_area(unsigned long addr, unsigned long len)
 {
 	struct vm_area_struct *vma;

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

 	return -ENOMEM;
 }

 static unsigned long htlb_get_low_area(unsigned long len, u16 segmask)
 {
 	unsigned long addr = 0;
 	struct vm_area_struct *vma;

 	vma = find_vma(current->mm, addr);
 	while (addr + len <= 0x100000000UL) {
 		BUG_ON(vma && (addr >= vma->vm_end)); /* invariant */

 		if (! __within_hugepage_low_range(addr, len, segmask)) {
 			addr = ALIGN(addr+1, 1<<SID_SHIFT);
 			vma = find_vma(current->mm, addr);
 			continue;
 		}

 		if (!vma || (addr + len) <= vma->vm_start)
 			return addr;
 		addr = ALIGN(vma->vm_end, HPAGE_SIZE);
 		/* Depending on segmask this might not be a confirmed
 		 * hugepage region, so the ALIGN could have skipped
 		 * some VMAs */
 		vma = find_vma(current->mm, addr);
 	}

 	return -ENOMEM;
 }

 static unsigned long htlb_get_high_area(unsigned long len, u16 areamask)
 {
 	unsigned long addr = 0x100000000UL;
 	struct vm_area_struct *vma;

 	vma = find_vma(current->mm, addr);
 	while (addr + len <= TASK_SIZE_USER64) {
 		BUG_ON(vma && (addr >= vma->vm_end)); /* invariant */

 		if (! __within_hugepage_high_range(addr, len, areamask)) {
 			addr = ALIGN(addr+1, 1UL<<HTLB_AREA_SHIFT);
 			vma = find_vma(current->mm, addr);
 			continue;
 		}

 		if (!vma || (addr + len) <= vma->vm_start)
 			return addr;
 		addr = ALIGN(vma->vm_end, HPAGE_SIZE);
 		/* Depending on segmask this might not be a confirmed
 		 * hugepage region, so the ALIGN could have skipped
 		 * some VMAs */
 		vma = find_vma(current->mm, addr);
 	}

 	return -ENOMEM;
 }

 unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
 					unsigned long len, unsigned long pgoff,
 					unsigned long flags)
 {
 	int lastshift;
 	u16 areamask, curareas;

 	if (HPAGE_SHIFT == 0)
 		return -EINVAL;
 	if (len & ~HPAGE_MASK)
 		return -EINVAL;

 	if (!cpu_has_feature(CPU_FTR_16M_PAGE))
 		return -EINVAL;

 	/* Paranoia, caller should have dealt with this */
 	BUG_ON((addr + len)  < addr);

 	if (test_thread_flag(TIF_32BIT)) {
 		/* Paranoia, caller should have dealt with this */
 		BUG_ON((addr + len) > 0x100000000UL);

 		curareas = current->mm->context.low_htlb_areas;

 		/* First see if we can use the hint address */
 		if (addr && (htlb_check_hinted_area(addr, len) == 0)) {
 			areamask = LOW_ESID_MASK(addr, len);
 			if (open_low_hpage_areas(current->mm, areamask) == 0)
 				return addr;
 		}

 		/* Next see if we can map in the existing low areas */
 		addr = htlb_get_low_area(len, curareas);
 		if (addr != -ENOMEM)
 			return addr;

 		/* Finally go looking for areas to open */
 		lastshift = 0;
 		for (areamask = LOW_ESID_MASK(0x100000000UL-len, len);
 		     ! lastshift; areamask >>=1) {
 			if (areamask & 1)
 				lastshift = 1;

 			addr = htlb_get_low_area(len, curareas | areamask);
 			if ((addr != -ENOMEM)
 			    && open_low_hpage_areas(current->mm, areamask) == 0)
 				return addr;
 		}
 	} else {
 		curareas = current->mm->context.high_htlb_areas;

 		/* First see if we can use the hint address */
 		/* We discourage 64-bit processes from doing hugepage
 		 * mappings below 4GB (must use MAP_FIXED) */
 		if ((addr >= 0x100000000UL)
 		    && (htlb_check_hinted_area(addr, len) == 0)) {
 			areamask = HTLB_AREA_MASK(addr, len);
 			if (open_high_hpage_areas(current->mm, areamask) == 0)
 				return addr;
 		}

 		/* Next see if we can map in the existing high areas */
 		addr = htlb_get_high_area(len, curareas);
 		if (addr != -ENOMEM)
 			return addr;

 		/* Finally go looking for areas to open */
 		lastshift = 0;
 		for (areamask = HTLB_AREA_MASK(TASK_SIZE_USER64-len, len);
 		     ! lastshift; areamask >>=1) {
 			if (areamask & 1)
 				lastshift = 1;

 			addr = htlb_get_high_area(len, curareas | areamask);
 			if ((addr != -ENOMEM)
 			    && open_high_hpage_areas(current->mm, areamask) == 0)
 				return addr;
 		}
 	}
 	printk(KERN_DEBUG "hugetlb_get_unmapped_area() unable to open"
 	       " enough areas\n");
 	return -ENOMEM;
 }

 /*
  * Called by asm hashtable.S for doing lazy icache flush
  */
 static unsigned int hash_huge_page_do_lazy_icache(unsigned long rflags,
 						  pte_t pte, int trap)
 {
 	struct page *page;
 	int i;

 	if (!pfn_valid(pte_pfn(pte)))
 		return rflags;

 	page = pte_page(pte);

 	/* page is dirty */
 	if (!test_bit(PG_arch_1, &page->flags) && !PageReserved(page)) {
 		if (trap == 0x400) {
 			for (i = 0; i < (HPAGE_SIZE / PAGE_SIZE); i++)
 				__flush_dcache_icache(page_address(page+i));
 			set_bit(PG_arch_1, &page->flags);
 		} else {
 			rflags |= HPTE_R_N;
 		}
 	}
 	return rflags;
 }

 int hash_huge_page(struct mm_struct *mm, unsigned long access,
 		   unsigned long ea, unsigned long vsid, int local,
 		   unsigned long trap)
 {
 	pte_t *ptep;
 	unsigned long old_pte, new_pte;
 	unsigned long va, rflags, pa;
 	long slot;
 	int err = 1;

 	ptep = huge_pte_offset(mm, ea);

 	/* Search the Linux page table for a match with va */
 	va = (vsid << 28) | (ea & 0x0fffffff);

 	/*
 	 * If no pte found or not present, send the problem up to
 	 * do_page_fault
 	 */
 	if (unlikely(!ptep || pte_none(*ptep)))
 		goto out;

 	/*
 	 * Check the user's access rights to the page.  If access should be
 	 * prevented then send the problem up to do_page_fault.
 	 */
 	if (unlikely(access & ~pte_val(*ptep)))
 		goto out;
 	/*
 	 * At this point, we have a pte (old_pte) which can be used to build
 	 * or update an HPTE. There are 2 cases:
 	 *
 	 * 1. There is a valid (present) pte with no associated HPTE (this is
 	 *	the most common case)
 	 * 2. There is a valid (present) pte with an associated HPTE. The
 	 *	current values of the pp bits in the HPTE prevent access
 	 *	because we are doing software DIRTY bit management and the
 	 *	page is currently not DIRTY.
 	 */


 	do {
 		old_pte = pte_val(*ptep);
 		if (old_pte & _PAGE_BUSY)
 			goto out;
 		new_pte = old_pte | _PAGE_BUSY |
 			_PAGE_ACCESSED | _PAGE_HASHPTE;
 	} while(old_pte != __cmpxchg_u64((unsigned long *)ptep,
 					 old_pte, new_pte));

 	rflags = 0x2 | (!(new_pte & _PAGE_RW));
  	/* _PAGE_EXEC -> HW_NO_EXEC since it's inverted */
 	rflags |= ((new_pte & _PAGE_EXEC) ? 0 : HPTE_R_N);
 	if (!cpu_has_feature(CPU_FTR_COHERENT_ICACHE))
 		/* No CPU has hugepages but lacks no execute, so we
 		 * don't need to worry about that case */
 		rflags = hash_huge_page_do_lazy_icache(rflags, __pte(old_pte),
 						       trap);

 	/* Check if pte already has an hpte (case 2) */
 	if (unlikely(old_pte & _PAGE_HASHPTE)) {
 		/* There MIGHT be an HPTE for this pte */
 		unsigned long hash, slot;

 		hash = hpt_hash(va, HPAGE_SHIFT);
 		if (old_pte & _PAGE_F_SECOND)
 			hash = ~hash;
 		slot = (hash & htab_hash_mask) * HPTES_PER_GROUP;
 		slot += (old_pte & _PAGE_F_GIX) >> 12;

 		if (ppc_md.hpte_updatepp(slot, rflags, va, mmu_huge_psize,
 					 local) == -1)
 			old_pte &= ~_PAGE_HPTEFLAGS;
 	}

 	if (likely(!(old_pte & _PAGE_HASHPTE))) {
 		unsigned long hash = hpt_hash(va, HPAGE_SHIFT);
 		unsigned long hpte_group;

 		pa = pte_pfn(__pte(old_pte)) << PAGE_SHIFT;

 repeat:
 		hpte_group = ((hash & htab_hash_mask) *
 			      HPTES_PER_GROUP) & ~0x7UL;

 		/* clear HPTE slot informations in new PTE */
 		new_pte = (new_pte & ~_PAGE_HPTEFLAGS) | _PAGE_HASHPTE;

 		/* Add in WIMG bits */
 		/* XXX We should store these in the pte */
 		/* --BenH: I think they are ... */
 		rflags |= _PAGE_COHERENT;

 		/* Insert into the hash table, primary slot */
 		slot = ppc_md.hpte_insert(hpte_group, va, pa, rflags, 0,
 					  mmu_huge_psize);

 		/* Primary is full, try the secondary */
 		if (unlikely(slot == -1)) {
 			new_pte |= _PAGE_F_SECOND;
 			hpte_group = ((~hash & htab_hash_mask) *
 				      HPTES_PER_GROUP) & ~0x7UL;
 			slot = ppc_md.hpte_insert(hpte_group, va, pa, rflags,
 						  HPTE_V_SECONDARY,
 						  mmu_huge_psize);
 			if (slot == -1) {
 				if (mftb() & 0x1)
 					hpte_group = ((hash & htab_hash_mask) *
 						      HPTES_PER_GROUP)&~0x7UL;

 				ppc_md.hpte_remove(hpte_group);
 				goto repeat;
                         }
 		}

 		if (unlikely(slot == -2))
 			panic("hash_huge_page: pte_insert failed\n");

 		new_pte |= (slot << 12) & _PAGE_F_GIX;
 	}

 	/*
 	 * No need to use ldarx/stdcx here
 	 */
 	*ptep = __pte(new_pte & ~_PAGE_BUSY);

 	err = 0;

  out:
 	return err;
 }
	/*
	* PPC64 (POWER4) Huge TLB Page Support for Kernel.
	*
	* Copyright (C) 2003 David Gibson, IBM Corporation.
	*
	* Based on the IA-32 version:
	* Copyright (C) 2002, Rohit Seth <rohit.seth@intel.com>
	*/

	#include <linux/init.h>
	#include <linux/fs.h>
	#include <linux/mm.h>
	#include <linux/hugetlb.h>
	#include <linux/pagemap.h>
	#include <linux/smp_lock.h>
	#include <linux/slab.h>
	#include <linux/err.h>
	#include <linux/sysctl.h>
	#include <asm/mman.h>
	#include <asm/pgalloc.h>
	#include <asm/tlb.h>
	#include <asm/tlbflush.h>
	#include <asm/mmu_context.h>
	#include <asm/machdep.h>
	#include <asm/cputable.h>
	#include <asm/tlb.h>

	#include <linux/sysctl.h>

	#define NUM_LOW_AREAS (0x100000000UL >> SID_SHIFT)
	#define NUM_HIGH_AREAS (PGTABLE_RANGE >> HTLB_AREA_SHIFT)

	/* Modelled after find_linux_pte() */
	pte_t huge_pte_offset(struct mm_struct mm, unsigned long addr)
	{
	pgd_t *pg;
	pud_t *pu;
	pmd_t *pm;
	pte_t *pt;

	BUG_ON(! in_hugepage_area(mm->context, addr));

	addr &= HPAGE_MASK;

	pg = pgd_offset(mm, addr);
	if (!pgd_none(*pg)) {
	pu = pud_offset(pg, addr);
	if (!pud_none(*pu)) {
	pm = pmd_offset(pu, addr);
	#ifdef CONFIG_PPC_64K_PAGES
	/* Currently, we use the normal PTE offset within full
	* size PTE pages, thus our huge PTEs are scattered in
	* the PTE page and we do waste some. We may change
	* that in the future, but the current mecanism keeps
	* things much simpler
	*/
	if (!pmd_none(*pm)) {
	/* Note: pte_offset_* are all equivalent on
	* ppc64 as we don't have HIGHMEM
	*/
	pt = pte_offset_kernel(pm, addr);
	return pt;
	}
	#else /* CONFIG_PPC_64K_PAGES */
	/* On 4k pages, we put huge PTEs in the PMD page */
	pt = (pte_t *)pm;
	return pt;
	#endif /* CONFIG_PPC_64K_PAGES */
	}
	}

	return NULL;
	}

	pte_t huge_pte_alloc(struct mm_struct mm, unsigned long addr)
	{
	pgd_t *pg;
	pud_t *pu;
	pmd_t *pm;
	pte_t *pt;

	BUG_ON(! in_hugepage_area(mm->context, addr));

	addr &= HPAGE_MASK;

	pg = pgd_offset(mm, addr);
	pu = pud_alloc(mm, pg, addr);

	if (pu) {
	pm = pmd_alloc(mm, pu, addr);
	if (pm) {
	#ifdef CONFIG_PPC_64K_PAGES
	/* See comment in huge_pte_offset. Note that if we ever
	* want to put the page size in the PMD, we would have
	* to open code our own pte_alloc* function in order
	* to populate and set the size atomically
	*/
	pt = pte_alloc_map(mm, pm, addr);
	#else /* CONFIG_PPC_64K_PAGES */
	pt = (pte_t *)pm;
	#endif /* CONFIG_PPC_64K_PAGES */
	return pt;
	}
	}

	return NULL;
	}

	void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
	pte_t *ptep, pte_t pte)
	{
	if (pte_present(*ptep)) {
	/* We open-code pte_clear because we need to pass the right
	* argument to hpte_update (huge / !huge)
	*/
	unsigned long old = pte_update(ptep, ~0UL);
	if (old & _PAGE_HASHPTE)
	hpte_update(mm, addr & HPAGE_MASK, ptep, old, 1);
	flush_tlb_pending();
	}
	*ptep = __pte(pte_val(pte) & ~_PAGE_HPTEFLAGS);
	}

	pte_t huge_ptep_get_and_clear(struct mm_struct *mm, unsigned long addr,
	pte_t *ptep)
	{
	unsigned long old = pte_update(ptep, ~0UL);

	if (old & _PAGE_HASHPTE)
	hpte_update(mm, addr & HPAGE_MASK, ptep, old, 1);
	*ptep = __pte(0);

	return __pte(old);
	}

	/*
	* This function checks for proper alignment of input addr and len parameters.
	*/
	int is_aligned_hugepage_range(unsigned long addr, unsigned long len)
	{
	if (len & ~HPAGE_MASK)
	return -EINVAL;
	if (addr & ~HPAGE_MASK)
	return -EINVAL;
	if (! (within_hugepage_low_range(addr, len)
	\|\| within_hugepage_high_range(addr, len)) )
	return -EINVAL;
	return 0;
	}

	struct slb_flush_info {
	struct mm_struct *mm;
	u16 newareas;
	};

	static void flush_low_segments(void *parm)
	{
	struct slb_flush_info *fi = parm;
	unsigned long i;

	BUILD_BUG_ON((sizeof(fi->newareas)*8) != NUM_LOW_AREAS);

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

	/* Only need to do anything if this CPU is working in the same
	* mm as the one which has changed */

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

	asm volatile("isync" : : : "memory");
	for (i = 0; i < NUM_LOW_AREAS; i++) {
	if (! (fi->newareas & (1U << i)))
	continue;
	asm volatile("slbie %0"
	: : "r" ((i << SID_SHIFT) \| SLBIE_C));
	}
	asm volatile("isync" : : : "memory");
	}

	static void flush_high_segments(void *parm)
	{
	struct slb_flush_info *fi = parm;
	unsigned long i, j;


	BUILD_BUG_ON((sizeof(fi->newareas)*8) != NUM_HIGH_AREAS);

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

	/* Only need to do anything if this CPU is working in the same
	* mm as the one which has changed */

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

	asm volatile("isync" : : : "memory");
	for (i = 0; i < NUM_HIGH_AREAS; i++) {
	if (! (fi->newareas & (1U << i)))
	continue;
	for (j = 0; j < (1UL << (HTLB_AREA_SHIFT-SID_SHIFT)); j++)
	asm volatile("slbie %0"
	:: "r" (((i << HTLB_AREA_SHIFT)
	+ (j << SID_SHIFT)) \| SLBIE_C));
	}
	asm volatile("isync" : : : "memory");
	}

	static int prepare_low_area_for_htlb(struct mm_struct *mm, unsigned long area)
	{
	unsigned long start = area << SID_SHIFT;
	unsigned long end = (area+1) << SID_SHIFT;
	struct vm_area_struct *vma;

	BUG_ON(area >= NUM_LOW_AREAS);

	/* Check no VMAs are in the region */
	vma = find_vma(mm, start);
	if (vma && (vma->vm_start < end))
	return -EBUSY;

	return 0;
	}

	static int prepare_high_area_for_htlb(struct mm_struct *mm, unsigned long area)
	{
	unsigned long start = area << HTLB_AREA_SHIFT;
	unsigned long end = (area+1) << HTLB_AREA_SHIFT;
	struct vm_area_struct *vma;

	BUG_ON(area >= NUM_HIGH_AREAS);

	/* 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 = 0x100000000UL;

	/* Check no VMAs are in the region */
	vma = find_vma(mm, start);
	if (vma && (vma->vm_start < end))
	return -EBUSY;

	return 0;
	}

	static int open_low_hpage_areas(struct mm_struct *mm, u16 newareas)
	{
	unsigned long i;
	struct slb_flush_info fi;

	BUILD_BUG_ON((sizeof(newareas)*8) != NUM_LOW_AREAS);
	BUILD_BUG_ON((sizeof(mm->context.low_htlb_areas)*8) != NUM_LOW_AREAS);

	newareas &= ~(mm->context.low_htlb_areas);
	if (! newareas)
	return 0; /* The segments we want are already open */

	for (i = 0; i < NUM_LOW_AREAS; i++)
	if ((1 << i) & newareas)
	if (prepare_low_area_for_htlb(mm, i) != 0)
	return -EBUSY;

	mm->context.low_htlb_areas \|= newareas;

	/* the context change must make it to memory before the flush,
	* so that further SLB misses do the right thing. */
	mb();

	fi.mm = mm;
	fi.newareas = newareas;
	on_each_cpu(flush_low_segments, &fi, 0, 1);

	return 0;
	}

	static int open_high_hpage_areas(struct mm_struct *mm, u16 newareas)
	{
	struct slb_flush_info fi;
	unsigned long i;

	BUILD_BUG_ON((sizeof(newareas)*8) != NUM_HIGH_AREAS);
	BUILD_BUG_ON((sizeof(mm->context.high_htlb_areas)*8)
	!= NUM_HIGH_AREAS);

	newareas &= ~(mm->context.high_htlb_areas);
	if (! newareas)
	return 0; /* The areas we want are already open */

	for (i = 0; i < NUM_HIGH_AREAS; i++)
	if ((1 << i) & newareas)
	if (prepare_high_area_for_htlb(mm, i) != 0)
	return -EBUSY;

	mm->context.high_htlb_areas \|= newareas;

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

	/* the context change must make it to memory before the flush,
	* so that further SLB misses do the right thing. */
	mb();

	fi.mm = mm;
	fi.newareas = newareas;
	on_each_cpu(flush_high_segments, &fi, 0, 1);

	return 0;
	}

	int prepare_hugepage_range(unsigned long addr, unsigned long len)
	{
	int err = 0;

	if ( (addr+len) < addr )
	return -EINVAL;

	if (addr < 0x100000000UL)
	err = open_low_hpage_areas(current->mm,
	LOW_ESID_MASK(addr, len));
	if ((addr + len) > 0x100000000UL)
	err = open_high_hpage_areas(current->mm,
	HTLB_AREA_MASK(addr, len));
	if (err) {
	printk(KERN_DEBUG "prepare_hugepage_range(%lx, %lx)"
	" failed (lowmask: 0x%04hx, highmask: 0x%04hx)\n",
	addr, len,
	LOW_ESID_MASK(addr, len), HTLB_AREA_MASK(addr, len));
	return err;
	}

	return 0;
	}

	struct page *
	follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
	{
	pte_t *ptep;
	struct page *page;

	if (! in_hugepage_area(mm->context, address))
	return ERR_PTR(-EINVAL);

	ptep = huge_pte_offset(mm, address);
	page = pte_page(*ptep);
	if (page)
	page += (address % HPAGE_SIZE) / PAGE_SIZE;

	return page;
	}

	int pmd_huge(pmd_t pmd)
	{
	return 0;
	}

	struct page *
	follow_huge_pmd(struct mm_struct *mm, unsigned long address,
	pmd_t *pmd, int write)
	{
	BUG();
	return NULL;
	}

	/* Because we have an exclusive hugepage region which lies within the
	* normal user address space, we have to take special measures to make
	* non-huge mmap()s evade the hugepage reserved regions. */
	unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,
	unsigned long len, unsigned long pgoff,
	unsigned long flags)
	{
	struct mm_struct *mm = current->mm;
	struct vm_area_struct *vma;
	unsigned long start_addr;

	if (len > TASK_SIZE)
	return -ENOMEM;

	if (addr) {
	addr = PAGE_ALIGN(addr);
	vma = find_vma(mm, addr);
	if (((TASK_SIZE - len) >= addr)
	&& (!vma \|\| (addr+len) <= vma->vm_start)
	&& !is_hugepage_only_range(mm, addr,len))
	return addr;
	}
	if (len > mm->cached_hole_size) {
	start_addr = addr = mm->free_area_cache;
	} else {
	start_addr = addr = TASK_UNMAPPED_BASE;
	mm->cached_hole_size = 0;
	}

	full_search:
	vma = find_vma(mm, addr);
	while (TASK_SIZE - len >= addr) {
	BUG_ON(vma && (addr >= vma->vm_end));

	if (touches_hugepage_low_range(mm, addr, len)) {
	addr = ALIGN(addr+1, 1<<SID_SHIFT);
	vma = find_vma(mm, addr);
	continue;
	}
	if (touches_hugepage_high_range(mm, addr, len)) {
	addr = ALIGN(addr+1, 1UL<<HTLB_AREA_SHIFT);
	vma = find_vma(mm, addr);
	continue;
	}
	if (!vma \|\| addr + len <= vma->vm_start) {
	/*
	* Remember the place where we stopped the search:
	*/
	mm->free_area_cache = addr + len;
	return addr;
	}
	if (addr + mm->cached_hole_size < vma->vm_start)
	mm->cached_hole_size = vma->vm_start - addr;
	addr = vma->vm_end;
	vma = vma->vm_next;
	}

	/* Make sure we didn't miss any holes */
	if (start_addr != TASK_UNMAPPED_BASE) {
	start_addr = addr = TASK_UNMAPPED_BASE;
	mm->cached_hole_size = 0;
	goto full_search;
	}
	return -ENOMEM;
	}

	/*
	* This mmap-allocator allocates new areas top-down from below the
	* stack's low limit (the base):
	*
	* Because we have an exclusive hugepage region which lies within the
	* normal user address space, we have to take special measures to make
	* non-huge mmap()s evade the hugepage reserved regions.
	*/
	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)
	{
	struct vm_area_struct vma, prev_vma;
	struct mm_struct *mm = current->mm;
	unsigned long base = mm->mmap_base, addr = addr0;
	unsigned long largest_hole = mm->cached_hole_size;
	int first_time = 1;

	/* requested length too big for entire address space */
	if (len > TASK_SIZE)
	return -ENOMEM;

	/* dont allow allocations above current base */
	if (mm->free_area_cache > base)
	mm->free_area_cache = base;

	/* requesting a specific address */
	if (addr) {
	addr = PAGE_ALIGN(addr);
	vma = find_vma(mm, addr);
	if (TASK_SIZE - len >= addr &&
	(!vma \|\| addr + len <= vma->vm_start)
	&& !is_hugepage_only_range(mm, addr,len))
	return addr;
	}

	if (len <= largest_hole) {
	largest_hole = 0;
	mm->free_area_cache = base;
	}
	try_again:
	/* make sure it can fit in the remaining address space */
	if (mm->free_area_cache < len)
	goto fail;

	/* either no address requested or cant fit in requested address hole */
	addr = (mm->free_area_cache - len) & PAGE_MASK;
	do {
	hugepage_recheck:
	if (touches_hugepage_low_range(mm, addr, len)) {
	addr = (addr & ((~0) << SID_SHIFT)) - len;
	goto hugepage_recheck;
	} else if (touches_hugepage_high_range(mm, addr, len)) {
	addr = (addr & ((~0UL) << HTLB_AREA_SHIFT)) - len;
	goto hugepage_recheck;
	}

	/*
	* Lookup failure means no vma is above this address,
	* i.e. return with success:
	*/
	if (!(vma = find_vma_prev(mm, addr, &prev_vma)))
	return addr;

	/*
	* new region fits between prev_vma->vm_end and
	* vma->vm_start, use it:
	*/
	if (addr+len <= vma->vm_start &&
	(!prev_vma \|\| (addr >= prev_vma->vm_end))) {
	/* remember the address as a hint for next time */
	mm->cached_hole_size = largest_hole;
	return (mm->free_area_cache = addr);
	} else {
	/* pull free_area_cache down to the first hole */
	if (mm->free_area_cache == vma->vm_end) {
	mm->free_area_cache = vma->vm_start;
	mm->cached_hole_size = largest_hole;
	}
	}

	/* remember the largest hole we saw so far */
	if (addr + largest_hole < vma->vm_start)
	largest_hole = vma->vm_start - addr;

	/* try just below the current vma->vm_start */
	addr = vma->vm_start-len;
	} while (len <= vma->vm_start);

	fail:
	/*
	* if hint left us with no space for the requested
	* mapping then try again:
	*/
	if (first_time) {
	mm->free_area_cache = base;
	largest_hole = 0;
	first_time = 0;
	goto try_again;
	}
	/*
	* 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.
	*/
	mm->free_area_cache = TASK_UNMAPPED_BASE;
	mm->cached_hole_size = ~0UL;
	addr = arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
	/*
	* Restore the topdown base:
	*/
	mm->free_area_cache = base;
	mm->cached_hole_size = ~0UL;

	return addr;
	}

	static int htlb_check_hinted_area(unsigned long addr, unsigned long len)
	{
	struct vm_area_struct *vma;

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

	return -ENOMEM;
	}

	static unsigned long htlb_get_low_area(unsigned long len, u16 segmask)
	{
	unsigned long addr = 0;
	struct vm_area_struct *vma;

	vma = find_vma(current->mm, addr);
	while (addr + len <= 0x100000000UL) {
	BUG_ON(vma && (addr >= vma->vm_end)); /* invariant */

	if (! __within_hugepage_low_range(addr, len, segmask)) {
	addr = ALIGN(addr+1, 1<<SID_SHIFT);
	vma = find_vma(current->mm, addr);
	continue;
	}

	if (!vma \|\| (addr + len) <= vma->vm_start)
	return addr;
	addr = ALIGN(vma->vm_end, HPAGE_SIZE);
	/* Depending on segmask this might not be a confirmed
	* hugepage region, so the ALIGN could have skipped
	* some VMAs */
	vma = find_vma(current->mm, addr);
	}

	return -ENOMEM;
	}

	static unsigned long htlb_get_high_area(unsigned long len, u16 areamask)
	{
	unsigned long addr = 0x100000000UL;
	struct vm_area_struct *vma;

	vma = find_vma(current->mm, addr);
	while (addr + len <= TASK_SIZE_USER64) {
	BUG_ON(vma && (addr >= vma->vm_end)); /* invariant */

	if (! __within_hugepage_high_range(addr, len, areamask)) {
	addr = ALIGN(addr+1, 1UL<<HTLB_AREA_SHIFT);
	vma = find_vma(current->mm, addr);
	continue;
	}

	if (!vma \|\| (addr + len) <= vma->vm_start)
	return addr;
	addr = ALIGN(vma->vm_end, HPAGE_SIZE);
	/* Depending on segmask this might not be a confirmed
	* hugepage region, so the ALIGN could have skipped
	* some VMAs */
	vma = find_vma(current->mm, addr);
	}

	return -ENOMEM;
	}

	unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
	unsigned long len, unsigned long pgoff,
	unsigned long flags)
	{
	int lastshift;
	u16 areamask, curareas;

	if (HPAGE_SHIFT == 0)
	return -EINVAL;
	if (len & ~HPAGE_MASK)
	return -EINVAL;

	if (!cpu_has_feature(CPU_FTR_16M_PAGE))
	return -EINVAL;

	/* Paranoia, caller should have dealt with this */
	BUG_ON((addr + len) < addr);

	if (test_thread_flag(TIF_32BIT)) {
	/* Paranoia, caller should have dealt with this */
	BUG_ON((addr + len) > 0x100000000UL);

	curareas = current->mm->context.low_htlb_areas;

	/* First see if we can use the hint address */
	if (addr && (htlb_check_hinted_area(addr, len) == 0)) {
	areamask = LOW_ESID_MASK(addr, len);
	if (open_low_hpage_areas(current->mm, areamask) == 0)
	return addr;
	}

	/* Next see if we can map in the existing low areas */
	addr = htlb_get_low_area(len, curareas);
	if (addr != -ENOMEM)
	return addr;

	/* Finally go looking for areas to open */
	lastshift = 0;
	for (areamask = LOW_ESID_MASK(0x100000000UL-len, len);
	! lastshift; areamask >>=1) {
	if (areamask & 1)
	lastshift = 1;

	addr = htlb_get_low_area(len, curareas \| areamask);
	if ((addr != -ENOMEM)
	&& open_low_hpage_areas(current->mm, areamask) == 0)
	return addr;
	}
	} else {
	curareas = current->mm->context.high_htlb_areas;

	/* First see if we can use the hint address */
	/* We discourage 64-bit processes from doing hugepage
	* mappings below 4GB (must use MAP_FIXED) */
	if ((addr >= 0x100000000UL)
	&& (htlb_check_hinted_area(addr, len) == 0)) {
	areamask = HTLB_AREA_MASK(addr, len);
	if (open_high_hpage_areas(current->mm, areamask) == 0)
	return addr;
	}

	/* Next see if we can map in the existing high areas */
	addr = htlb_get_high_area(len, curareas);
	if (addr != -ENOMEM)
	return addr;

	/* Finally go looking for areas to open */
	lastshift = 0;
	for (areamask = HTLB_AREA_MASK(TASK_SIZE_USER64-len, len);
	! lastshift; areamask >>=1) {
	if (areamask & 1)
	lastshift = 1;

	addr = htlb_get_high_area(len, curareas \| areamask);
	if ((addr != -ENOMEM)
	&& open_high_hpage_areas(current->mm, areamask) == 0)
	return addr;
	}
	}
	printk(KERN_DEBUG "hugetlb_get_unmapped_area() unable to open"
	" enough areas\n");
	return -ENOMEM;
	}

	/*
	* Called by asm hashtable.S for doing lazy icache flush
	*/
	static unsigned int hash_huge_page_do_lazy_icache(unsigned long rflags,
	pte_t pte, int trap)
	{
	struct page *page;
	int i;

	if (!pfn_valid(pte_pfn(pte)))
	return rflags;

	page = pte_page(pte);

	/* page is dirty */
	if (!test_bit(PG_arch_1, &page->flags) && !PageReserved(page)) {
	if (trap == 0x400) {
	for (i = 0; i < (HPAGE_SIZE / PAGE_SIZE); i++)
	__flush_dcache_icache(page_address(page+i));
	set_bit(PG_arch_1, &page->flags);
	} else {
	rflags \|= HPTE_R_N;
	}
	}
	return rflags;
	}

	int hash_huge_page(struct mm_struct *mm, unsigned long access,
	unsigned long ea, unsigned long vsid, int local,
	unsigned long trap)
	{
	pte_t *ptep;
	unsigned long old_pte, new_pte;
	unsigned long va, rflags, pa;
	long slot;
	int err = 1;

	ptep = huge_pte_offset(mm, ea);

	/* Search the Linux page table for a match with va */
	va = (vsid << 28) \| (ea & 0x0fffffff);

	/*
	* If no pte found or not present, send the problem up to
	* do_page_fault
	*/
	if (unlikely(!ptep \|\| pte_none(*ptep)))
	goto out;

	/*
	* Check the user's access rights to the page. If access should be
	* prevented then send the problem up to do_page_fault.
	*/
	if (unlikely(access & ~pte_val(*ptep)))
	goto out;
	/*
	* At this point, we have a pte (old_pte) which can be used to build
	* or update an HPTE. There are 2 cases:
	*
	* 1. There is a valid (present) pte with no associated HPTE (this is
	* the most common case)
	* 2. There is a valid (present) pte with an associated HPTE. The
	* current values of the pp bits in the HPTE prevent access
	* because we are doing software DIRTY bit management and the
	* page is currently not DIRTY.
	*/


	do {
	old_pte = pte_val(*ptep);
	if (old_pte & _PAGE_BUSY)
	goto out;
	new_pte = old_pte \| _PAGE_BUSY \|
	_PAGE_ACCESSED \| _PAGE_HASHPTE;
	} while(old_pte != __cmpxchg_u64((unsigned long *)ptep,
	old_pte, new_pte));

	rflags = 0x2 \| (!(new_pte & _PAGE_RW));
	/* _PAGE_EXEC -> HW_NO_EXEC since it's inverted */
	rflags \|= ((new_pte & _PAGE_EXEC) ? 0 : HPTE_R_N);
	if (!cpu_has_feature(CPU_FTR_COHERENT_ICACHE))
	/* No CPU has hugepages but lacks no execute, so we
	* don't need to worry about that case */
	rflags = hash_huge_page_do_lazy_icache(rflags, __pte(old_pte),
	trap);

	/* Check if pte already has an hpte (case 2) */
	if (unlikely(old_pte & _PAGE_HASHPTE)) {
	/* There MIGHT be an HPTE for this pte */
	unsigned long hash, slot;

	hash = hpt_hash(va, HPAGE_SHIFT);
	if (old_pte & _PAGE_F_SECOND)
	hash = ~hash;
	slot = (hash & htab_hash_mask) * HPTES_PER_GROUP;
	slot += (old_pte & _PAGE_F_GIX) >> 12;

	if (ppc_md.hpte_updatepp(slot, rflags, va, mmu_huge_psize,
	local) == -1)
	old_pte &= ~_PAGE_HPTEFLAGS;
	}

	if (likely(!(old_pte & _PAGE_HASHPTE))) {
	unsigned long hash = hpt_hash(va, HPAGE_SHIFT);
	unsigned long hpte_group;

	pa = pte_pfn(__pte(old_pte)) << PAGE_SHIFT;

	repeat:
	hpte_group = ((hash & htab_hash_mask) *
	HPTES_PER_GROUP) & ~0x7UL;

	/* clear HPTE slot informations in new PTE */
	new_pte = (new_pte & ~_PAGE_HPTEFLAGS) \| _PAGE_HASHPTE;

	/* Add in WIMG bits */
	/* XXX We should store these in the pte */
	/* --BenH: I think they are ... */
	rflags \|= _PAGE_COHERENT;

	/* Insert into the hash table, primary slot */
	slot = ppc_md.hpte_insert(hpte_group, va, pa, rflags, 0,
	mmu_huge_psize);

	/* Primary is full, try the secondary */
	if (unlikely(slot == -1)) {
	new_pte \|= _PAGE_F_SECOND;
	hpte_group = ((~hash & htab_hash_mask) *
	HPTES_PER_GROUP) & ~0x7UL;
	slot = ppc_md.hpte_insert(hpte_group, va, pa, rflags,
	HPTE_V_SECONDARY,
	mmu_huge_psize);
	if (slot == -1) {
	if (mftb() & 0x1)
	hpte_group = ((hash & htab_hash_mask) *
	HPTES_PER_GROUP)&~0x7UL;

	ppc_md.hpte_remove(hpte_group);
	goto repeat;
	}
	}

	if (unlikely(slot == -2))
	panic("hash_huge_page: pte_insert failed\n");

	new_pte \|= (slot << 12) & _PAGE_F_GIX;
	}

	/*
	* No need to use ldarx/stdcx here
	*/
	*ptep = __pte(new_pte & ~_PAGE_BUSY);

	err = 0;

	out:
	return err;
	}