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slice.c

/*
 * 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/module.h>
#include <asm/mman.h>
#include <asm/mmu.h>
#include <asm/spu.h>

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 + 16 + 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 & (1 << 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 = (1u << (GET_HIGH_SLICE_INDEX(end) + 1))
                  - (1u << 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 |= 1u << i;

      return ret;
}

static struct slice_mask slice_mask_for_size(struct mm_struct *mm, int psize)
{
      struct slice_mask ret = { 0, 0 };
      unsigned long i;
      u64 psizes;

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

      psizes = mm->context.high_slices_psize;
      for (i = 0; i < SLICE_NUM_HIGH; i++)
            if (((psizes >> (i * 4)) & 0xf) == psize)
                  ret.high_slices |= 1u << 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)
{
      /* Write the new slice psize bits */
      u64 lpsizes, hpsizes;
      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));

      hpsizes = mm->context.high_slices_psize;
      for (i = 0; i < SLICE_NUM_HIGH; i++)
            if (mask.high_slices & (1u << i))
                  hpsizes = (hpsizes & ~(0xful << (i * 4))) |
                        (((unsigned long)psize) << (i * 4));

      mm->context.low_slices_psize = lpsizes;
      mm->context.high_slices_psize = hpsizes;

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

      spin_unlock_irqrestore(&slice_convert_lock, flags);

#ifdef CONFIG_SPU_BASE
      spu_flush_all_slbs(mm);
#endif
}

static unsigned long slice_find_area_bottomup(struct mm_struct *mm,
                                    unsigned long len,
                                    struct slice_mask available,
                                    int psize, int use_cache)
{
      struct vm_area_struct *vma;
      unsigned long start_addr, addr;
      struct slice_mask mask;
      int pshift = max_t(int, mmu_psize_defs[psize].shift, PAGE_SHIFT);

      if (use_cache) {
            if (len <= mm->cached_hole_size) {
                  start_addr = addr = TASK_UNMAPPED_BASE;
                  mm->cached_hole_size = 0;
            } else
                  start_addr = addr = mm->free_area_cache;
      } else
            start_addr = addr = TASK_UNMAPPED_BASE;

full_search:
      for (;;) {
            addr = _ALIGN_UP(addr, 1ul << pshift);
            if ((TASK_SIZE - len) < addr)
                  break;
            vma = find_vma(mm, addr);
            BUG_ON(vma && (addr >= vma->vm_end));

            mask = slice_range_to_mask(addr, len);
            if (!slice_check_fit(mask, available)) {
                  if (addr < SLICE_LOW_TOP)
                        addr = _ALIGN_UP(addr + 1,  1ul << SLICE_LOW_SHIFT);
                  else
                        addr = _ALIGN_UP(addr + 1,  1ul << SLICE_HIGH_SHIFT);
                  continue;
            }
            if (!vma || addr + len <= vma->vm_start) {
                  /*
                   * Remember the place where we stopped the search:
                   */
                  if (use_cache)
                        mm->free_area_cache = addr + len;
                  return addr;
            }
            if (use_cache && (addr + mm->cached_hole_size) < vma->vm_start)
                    mm->cached_hole_size = vma->vm_start - addr;
            addr = vma->vm_end;
      }

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

static unsigned long slice_find_area_topdown(struct mm_struct *mm,
                                   unsigned long len,
                                   struct slice_mask available,
                                   int psize, int use_cache)
{
      struct vm_area_struct *vma;
      unsigned long addr;
      struct slice_mask mask;
      int pshift = max_t(int, mmu_psize_defs[psize].shift, PAGE_SHIFT);

      /* check if free_area_cache is useful for us */
      if (use_cache) {
            if (len <= mm->cached_hole_size) {
                  mm->cached_hole_size = 0;
                  mm->free_area_cache = mm->mmap_base;
            }

            /* either no address requested or can't fit in requested
             * address hole
             */
            addr = mm->free_area_cache;

            /* make sure it can fit in the remaining address space */
            if (addr > len) {
                  addr = _ALIGN_DOWN(addr - len, 1ul << pshift);
                  mask = slice_range_to_mask(addr, len);
                  if (slice_check_fit(mask, available) &&
                      slice_area_is_free(mm, addr, len))
                              /* remember the address as a hint for
                               * next time
                               */
                              return (mm->free_area_cache = addr);
            }
      }

      addr = mm->mmap_base;
      while (addr > len) {
            /* Go down by chunk size */
            addr = _ALIGN_DOWN(addr - len, 1ul << pshift);

            /* Check for hit with different page size */
            mask = slice_range_to_mask(addr, len);
            if (!slice_check_fit(mask, available)) {
                  if (addr < SLICE_LOW_TOP)
                        addr = _ALIGN_DOWN(addr, 1ul << SLICE_LOW_SHIFT);
                  else if (addr < (1ul << SLICE_HIGH_SHIFT))
                        addr = SLICE_LOW_TOP;
                  else
                        addr = _ALIGN_DOWN(addr, 1ul << SLICE_HIGH_SHIFT);
                  continue;
            }

            /*
             * Lookup failure means no vma is above this address,
             * else if new region fits below vma->vm_start,
             * return with success:
             */
            vma = find_vma(mm, addr);
            if (!vma || (addr + len) <= vma->vm_start) {
                  /* remember the address as a hint for next time */
                  if (use_cache)
                        mm->free_area_cache = addr;
                  return addr;
            }

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

            /* try just below the current vma->vm_start */
            addr = vma->vm_start;
      }

      /*
       * 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.
       */
      addr = slice_find_area_bottomup(mm, len, available, psize, 0);

      /*
       * Restore the topdown base:
       */
      if (use_cache) {
            mm->free_area_cache = mm->mmap_base;
            mm->cached_hole_size = ~0UL;
      }

      return addr;
}


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

#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, int use_cache)
{
      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, use_cache=%d\n",
              addr, len, flags, topdown, use_cache);

      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 -EINVAL;

      /* 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,
                                use_cache);
            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,
                               use_cache);
            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,
                         use_cache);

#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, use_cache);
      }
#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, 1);
}

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, 1);
}

unsigned int get_slice_psize(struct mm_struct *mm, unsigned long addr)
{
      u64 psizes;
      int index;

      if (addr < SLICE_LOW_TOP) {
            psizes = mm->context.low_slices_psize;
            index = GET_LOW_SLICE_INDEX(addr);
      } else {
            psizes = mm->context.high_slices_psize;
            index = GET_HIGH_SLICE_INDEX(addr);
      }

      return (psizes >> (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)
{
      unsigned long flags, lpsizes, hpsizes;
      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));

      hpsizes = mm->context.high_slices_psize;
      for (i = 0; i < SLICE_NUM_HIGH; i++)
            if (((hpsizes >> (i * 4)) & 0xf) == old_psize)
                  hpsizes = (hpsizes & ~(0xful << (i * 4))) |
                        (((unsigned long)psize) << (i * 4));

      mm->context.low_slices_psize = lpsizes;
      mm->context.high_slices_psize = hpsizes;

      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_psize(struct mm_struct *mm, unsigned long address,
                 unsigned int psize)
{
      unsigned long i, flags;
      u64 *p;

      spin_lock_irqsave(&slice_convert_lock, flags);
      if (address < SLICE_LOW_TOP) {
            i = GET_LOW_SLICE_INDEX(address);
            p = &mm->context.low_slices_psize;
      } else {
            i = GET_HIGH_SLICE_INDEX(address);
            p = &mm->context.high_slices_psize;
      }
      *p = (*p & ~(0xful << (i * 4))) | ((unsigned long) psize << (i * 4));
      spin_unlock_irqrestore(&slice_convert_lock, flags);

#ifdef CONFIG_SPU_BASE
      spu_flush_all_slbs(mm);
#endif
}

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);
}

/*
 * is_hugepage_only_range() is used by generic code to verify wether
 * 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;

      mask = slice_range_to_mask(addr, len);
      available = slice_mask_for_size(mm, mm->context.user_psize);

#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);
}


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