/*
 * 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;
        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);
}