/*
 * A Remote Heap.  Remote means that we don't touch the memory that the
 * heap points to. Normal heap implementations use the memory they manage
 * to place their list. We cannot do that because the memory we manage may
 * have special properties, for example it is uncachable or of different
 * endianess.
 *
 * Author: Pantelis Antoniou <panto@intracom.gr>
 *
 * 2004 (c) INTRACOM S.A. Greece. This file is licensed under
 * the terms of the GNU General Public License version 2. This program
 * is licensed "as is" without any warranty of any kind, whether express
 * or implied.
 */
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/mm.h>
#include <linux/err.h>
#include <linux/slab.h>

#include <asm/rheap.h>

/*
 * Fixup a list_head, needed when copying lists.  If the pointers fall
 * between s and e, apply the delta.  This assumes that
 * sizeof(struct list_head *) == sizeof(unsigned long *).
 */
static inline void fixup(unsigned long s, unsigned long e, int d,
                         struct list_head *l)
{
        unsigned long *pp;

        pp = (unsigned long *)&l->next;
        if (*pp >= s && *pp < e)
                *pp += d;

        pp = (unsigned long *)&l->prev;
        if (*pp >= s && *pp < e)
                *pp += d;
}

/* Grow the allocated blocks */
static int grow(rh_info_t * info, int max_blocks)
{
        rh_block_t *block, *blk;
        int i, new_blocks;
        int delta;
        unsigned long blks, blke;

        if (max_blocks <= info->max_blocks)
                return -EINVAL;

        new_blocks = max_blocks - info->max_blocks;

        block = kmalloc_array(max_blocks, sizeof(rh_block_t), GFP_ATOMIC);
        if (block == NULL)
                return -ENOMEM;

        if (info->max_blocks > 0) {

                /* copy old block area */
                memcpy(block, info->block,
                       sizeof(rh_block_t) * info->max_blocks);

                delta = (char *)block - (char *)info->block;

                /* and fixup list pointers */
                blks = (unsigned long)info->block;
                blke = (unsigned long)(info->block + info->max_blocks);

                for (i = 0, blk = block; i < info->max_blocks; i++, blk++)
                        fixup(blks, blke, delta, &blk->list);

                fixup(blks, blke, delta, &info->empty_list);
                fixup(blks, blke, delta, &info->free_list);
                fixup(blks, blke, delta, &info->taken_list);

                /* free the old allocated memory */
                if ((info->flags & RHIF_STATIC_BLOCK) == 0)
                        kfree(info->block);
        }

        info->block = block;
        info->empty_slots += new_blocks;
        info->max_blocks = max_blocks;
        info->flags &= ~RHIF_STATIC_BLOCK;

        /* add all new blocks to the free list */
        blk = block + info->max_blocks - new_blocks;
        for (i = 0; i < new_blocks; i++, blk++)
                list_add(&blk->list, &info->empty_list);

        return 0;
}

/*
 * Assure at least the required amount of empty slots.  If this function
 * causes a grow in the block area then all pointers kept to the block
 * area are invalid!
 */
static int assure_empty(rh_info_t * info, int slots)
{
        int max_blocks;

        /* This function is not meant to be used to grow uncontrollably */
        if (slots >= 4)
                return -EINVAL;

        /* Enough space */
        if (info->empty_slots >= slots)
                return 0;

        /* Next 16 sized block */
        max_blocks = ((info->max_blocks + slots) + 15) & ~15;

        return grow(info, max_blocks);
}

static rh_block_t *get_slot(rh_info_t * info)
{
        rh_block_t *blk;

        /* If no more free slots, and failure to extend. */
        /* XXX: You should have called assure_empty before */
        if (info->empty_slots == 0) {
                printk(KERN_ERR "rh: out of slots; crash is imminent.\n");
                return NULL;
        }

        /* Get empty slot to use */
        blk = list_entry(info->empty_list.next, rh_block_t, list);
        list_del_init(&blk->list);
        info->empty_slots--;

        /* Initialize */
        blk->start = 0;
        blk->size = 0;
        blk->owner = NULL;

        return blk;
}

static inline void release_slot(rh_info_t * info, rh_block_t * blk)
{
        list_add(&blk->list, &info->empty_list);
        info->empty_slots++;
}

static void attach_free_block(rh_info_t * info, rh_block_t * blkn)
{
        rh_block_t *blk;
        rh_block_t *before;
        rh_block_t *after;
        rh_block_t *next;
        int size;
        unsigned long s, e, bs, be;
        struct list_head *l;

        /* We assume that they are aligned properly */
        size = blkn->size;
        s = blkn->start;
        e = s + size;

        /* Find the blocks immediately before and after the given one
         * (if any) */
        before = NULL;
        after = NULL;
        next = NULL;

        list_for_each(l, &info->free_list) {
                blk = list_entry(l, rh_block_t, list);

                bs = blk->start;
                be = bs + blk->size;

                if (next == NULL && s >= bs)
                        next = blk;

                if (be == s)
                        before = blk;

                if (e == bs)
                        after = blk;

                /* If both are not null, break now */
                if (before != NULL && after != NULL)
                        break;
        }

        /* Now check if they are really adjacent */
        if (before && s != (before->start + before->size))
                before = NULL;

        if (after && e != after->start)
                after = NULL;

        /* No coalescing; list insert and return */
        if (before == NULL && after == NULL) {

                if (next != NULL)
                        list_add(&blkn->list, &next->list);
                else
                        list_add(&blkn->list, &info->free_list);

                return;
        }

        /* We don't need it anymore */
        release_slot(info, blkn);

        /* Grow the before block */
        if (before != NULL && after == NULL) {
                before->size += size;
                return;
        }

        /* Grow the after block backwards */
        if (before == NULL && after != NULL) {
                after->start -= size;
                after->size += size;
                return;
        }

        /* Grow the before block, and release the after block */
        before->size += size + after->size;
        list_del(&after->list);
        release_slot(info, after);
}

static void attach_taken_block(rh_info_t * info, rh_block_t * blkn)
{
        rh_block_t *blk;
        struct list_head *l;

        /* Find the block immediately before the given one (if any) */
        list_for_each(l, &info->taken_list) {
                blk = list_entry(l, rh_block_t, list);
                if (blk->start > blkn->start) {
                        list_add_tail(&blkn->list, &blk->list);
                        return;
                }
        }

        list_add_tail(&blkn->list, &info->taken_list);
}

/*
 * Create a remote heap dynamically.  Note that no memory for the blocks
 * are allocated.  It will upon the first allocation
 */
rh_info_t *rh_create(unsigned int alignment)
{
        rh_info_t *info;

        /* Alignment must be a power of two */
        if ((alignment & (alignment - 1)) != 0)
                return ERR_PTR(-EINVAL);

        info = kmalloc(sizeof(*info), GFP_ATOMIC);
        if (info == NULL)
                return ERR_PTR(-ENOMEM);

        info->alignment = alignment;

        /* Initially everything as empty */
        info->block = NULL;
        info->max_blocks = 0;
        info->empty_slots = 0;
        info->flags = 0;

        INIT_LIST_HEAD(&info->empty_list);
        INIT_LIST_HEAD(&info->free_list);
        INIT_LIST_HEAD(&info->taken_list);

        return info;
}
EXPORT_SYMBOL_GPL(rh_create);

/*
 * Destroy a dynamically created remote heap.  Deallocate only if the areas
 * are not static
 */
void rh_destroy(rh_info_t * info)
{
        if ((info->flags & RHIF_STATIC_BLOCK) == 0)
                kfree(info->block);

        if ((info->flags & RHIF_STATIC_INFO) == 0)
                kfree(info);
}
EXPORT_SYMBOL_GPL(rh_destroy);

/*
 * Initialize in place a remote heap info block.  This is needed to support
 * operation very early in the startup of the kernel, when it is not yet safe
 * to call kmalloc.
 */
void rh_init(rh_info_t * info, unsigned int alignment, int max_blocks,
             rh_block_t * block)
{
        int i;
        rh_block_t *blk;

        /* Alignment must be a power of two */
        if ((alignment & (alignment - 1)) != 0)
                return;

        info->alignment = alignment;

        /* Initially everything as empty */
        info->block = block;
        info->max_blocks = max_blocks;
        info->empty_slots = max_blocks;
        info->flags = RHIF_STATIC_INFO | RHIF_STATIC_BLOCK;

        INIT_LIST_HEAD(&info->empty_list);
        INIT_LIST_HEAD(&info->free_list);
        INIT_LIST_HEAD(&info->taken_list);

        /* Add all new blocks to the free list */
        for (i = 0, blk = block; i < max_blocks; i++, blk++)
                list_add(&blk->list, &info->empty_list);
}
EXPORT_SYMBOL_GPL(rh_init);

/* Attach a free memory region, coalesces regions if adjacent */
int rh_attach_region(rh_info_t * info, unsigned long start, int size)
{
        rh_block_t *blk;
        unsigned long s, e, m;
        int r;

        /* The region must be aligned */
        s = start;
        e = s + size;
        m = info->alignment - 1;

        /* Round start up */
        s = (s + m) & ~m;

        /* Round end down */
        e = e & ~m;

        if (IS_ERR_VALUE(e) || (e < s))
                return -ERANGE;

        /* Take final values */
        start = s;
        size = e - s;

        /* Grow the blocks, if needed */
        r = assure_empty(info, 1);
        if (r < 0)
                return r;

        blk = get_slot(info);
        blk->start = start;
        blk->size = size;
        blk->owner = NULL;

        attach_free_block(info, blk);

        return 0;
}
EXPORT_SYMBOL_GPL(rh_attach_region);

/* Detatch given address range, splits free block if needed. */
unsigned long rh_detach_region(rh_info_t * info, unsigned long start, int size)
{
        struct list_head *l;
        rh_block_t *blk, *newblk;
        unsigned long s, e, m, bs, be;

        /* Validate size */
        if (size <= 0)
                return (unsigned long) -EINVAL;

        /* The region must be aligned */
        s = start;
        e = s + size;
        m = info->alignment - 1;

        /* Round start up */
        s = (s + m) & ~m;

        /* Round end down */
        e = e & ~m;

        if (assure_empty(info, 1) < 0)
                return (unsigned long) -ENOMEM;

        blk = NULL;
        list_for_each(l, &info->free_list) {
                blk = list_entry(l, rh_block_t, list);
                /* The range must lie entirely inside one free block */
                bs = blk->start;
                be = blk->start + blk->size;
                if (s >= bs && e <= be)
                        break;
                blk = NULL;
        }

        if (blk == NULL)
                return (unsigned long) -ENOMEM;

        /* Perfect fit */
        if (bs == s && be == e) {
                /* Delete from free list, release slot */
                list_del(&blk->list);
                release_slot(info, blk);
                return s;
        }

        /* blk still in free list, with updated start and/or size */
        if (bs == s || be == e) {
                if (bs == s)
                        blk->start += size;
                blk->size -= size;

        } else {
                /* The front free fragment */
                blk->size = s - bs;

                /* the back free fragment */
                newblk = get_slot(info);
                newblk->start = e;
                newblk->size = be - e;

                list_add(&newblk->list, &blk->list);
        }

        return s;
}
EXPORT_SYMBOL_GPL(rh_detach_region);

/* Allocate a block of memory at the specified alignment.  The value returned
 * is an offset into the buffer initialized by rh_init(), or a negative number
 * if there is an error.
 */
unsigned long rh_alloc_align(rh_info_t * info, int size, int alignment, const char *owner)
{
        struct list_head *l;
        rh_block_t *blk;
        rh_block_t *newblk;
        unsigned long start, sp_size;

        /* Validate size, and alignment must be power of two */
        if (size <= 0 || (alignment & (alignment - 1)) != 0)
                return (unsigned long) -EINVAL;

        /* Align to configured alignment */
        size = (size + (info->alignment - 1)) & ~(info->alignment - 1);

        if (assure_empty(info, 2) < 0)
                return (unsigned long) -ENOMEM;

        blk = NULL;
        list_for_each(l, &info->free_list) {
                blk = list_entry(l, rh_block_t, list);
                if (size <= blk->size) {
                        start = (blk->start + alignment - 1) & ~(alignment - 1);
                        if (start + size <= blk->start + blk->size)
                                break;
                }
                blk = NULL;
        }

        if (blk == NULL)
                return (unsigned long) -ENOMEM;

        /* Just fits */
        if (blk->size == size) {
                /* Move from free list to taken list */
                list_del(&blk->list);
                newblk = blk;
        } else {
                /* Fragment caused, split if needed */
                /* Create block for fragment in the beginning */
                sp_size = start - blk->start;
                if (sp_size) {
                        rh_block_t *spblk;

                        spblk = get_slot(info);
                        spblk->start = blk->start;
                        spblk->size = sp_size;
                        /* add before the blk */
                        list_add(&spblk->list, blk->list.prev);
                }
                newblk = get_slot(info);
                newblk->start = start;
                newblk->size = size;

                /* blk still in free list, with updated start and size
                 * for fragment in the end */
                blk->start = start + size;
                blk->size -= sp_size + size;
                /* No fragment in the end, remove blk */
                if (blk->size == 0) {
                        list_del(&blk->list);
                        release_slot(info, blk);
                }
        }

        newblk->owner = owner;
        attach_taken_block(info, newblk);

        return start;
}
EXPORT_SYMBOL_GPL(rh_alloc_align);

/* Allocate a block of memory at the default alignment.  The value returned is
 * an offset into the buffer initialized by rh_init(), or a negative number if
 * there is an error.
 */
unsigned long rh_alloc(rh_info_t * info, int size, const char *owner)
{
        return rh_alloc_align(info, size, info->alignment, owner);
}
EXPORT_SYMBOL_GPL(rh_alloc);

/* Allocate a block of memory at the given offset, rounded up to the default
 * alignment.  The value returned is an offset into the buffer initialized by
 * rh_init(), or a negative number if there is an error.
 */
unsigned long rh_alloc_fixed(rh_info_t * info, unsigned long start, int size, const char *owner)
{
        struct list_head *l;
        rh_block_t *blk, *newblk1, *newblk2;
        unsigned long s, e, m, bs = 0, be = 0;

        /* Validate size */
        if (size <= 0)
                return (unsigned long) -EINVAL;

        /* The region must be aligned */
        s = start;
        e = s + size;
        m = info->alignment - 1;

        /* Round start up */
        s = (s + m) & ~m;

        /* Round end down */
        e = e & ~m;

        if (assure_empty(info, 2) < 0)
                return (unsigned long) -ENOMEM;

        blk = NULL;
        list_for_each(l, &info->free_list) {
                blk = list_entry(l, rh_block_t, list);
                /* The range must lie entirely inside one free block */
                bs = blk->start;
                be = blk->start + blk->size;
                if (s >= bs && e <= be)
                        break;
                blk = NULL;
        }

        if (blk == NULL)
                return (unsigned long) -ENOMEM;

        /* Perfect fit */
        if (bs == s && be == e) {
                /* Move from free list to taken list */
                list_del(&blk->list);
                blk->owner = owner;

                start = blk->start;
                attach_taken_block(info, blk);

                return start;

        }

        /* blk still in free list, with updated start and/or size */
        if (bs == s || be == e) {
                if (bs == s)
                        blk->start += size;
                blk->size -= size;

        } else {
                /* The front free fragment */
                blk->size = s - bs;

                /* The back free fragment */
                newblk2 = get_slot(info);
                newblk2->start = e;
                newblk2->size = be - e;

                list_add(&newblk2->list, &blk->list);
        }

        newblk1 = get_slot(info);
        newblk1->start = s;
        newblk1->size = e - s;
        newblk1->owner = owner;

        start = newblk1->start;
        attach_taken_block(info, newblk1);

        return start;
}
EXPORT_SYMBOL_GPL(rh_alloc_fixed);

/* Deallocate the memory previously allocated by one of the rh_alloc functions.
 * The return value is the size of the deallocated block, or a negative number
 * if there is an error.
 */
int rh_free(rh_info_t * info, unsigned long start)
{
        rh_block_t *blk, *blk2;
        struct list_head *l;
        int size;

        /* Linear search for block */
        blk = NULL;
        list_for_each(l, &info->taken_list) {
                blk2 = list_entry(l, rh_block_t, list);
                if (start < blk2->start)
                        break;
                blk = blk2;
        }

        if (blk == NULL || start > (blk->start + blk->size))
                return -EINVAL;

        /* Remove from taken list */
        list_del(&blk->list);

        /* Get size of freed block */
        size = blk->size;
        attach_free_block(info, blk);

        return size;
}
EXPORT_SYMBOL_GPL(rh_free);

int rh_get_stats(rh_info_t * info, int what, int max_stats, rh_stats_t * stats)
{
        rh_block_t *blk;
        struct list_head *l;
        struct list_head *h;
        int nr;

        switch (what) {

        case RHGS_FREE:
                h = &info->free_list;
                break;

        case RHGS_TAKEN:
                h = &info->taken_list;
                break;

        default:
                return -EINVAL;
        }

        /* Linear search for block */
        nr = 0;
        list_for_each(l, h) {
                blk = list_entry(l, rh_block_t, list);
                if (stats != NULL && nr < max_stats) {
                        stats->start = blk->start;
                        stats->size = blk->size;
                        stats->owner = blk->owner;
                        stats++;
                }
                nr++;
        }

        return nr;
}
EXPORT_SYMBOL_GPL(rh_get_stats);

int rh_set_owner(rh_info_t * info, unsigned long start, const char *owner)
{
        rh_block_t *blk, *blk2;
        struct list_head *l;
        int size;

        /* Linear search for block */
        blk = NULL;
        list_for_each(l, &info->taken_list) {
                blk2 = list_entry(l, rh_block_t, list);
                if (start < blk2->start)
                        break;
                blk = blk2;
        }

        if (blk == NULL || start > (blk->start + blk->size))
                return -EINVAL;

        blk->owner = owner;
        size = blk->size;

        return size;
}
EXPORT_SYMBOL_GPL(rh_set_owner);

void rh_dump(rh_info_t * info)
{
        static rh_stats_t st[32];       /* XXX maximum 32 blocks */
        int maxnr;
        int i, nr;

        maxnr = ARRAY_SIZE(st);

        printk(KERN_INFO
               "info @0x%p (%d slots empty / %d max)\n",
               info, info->empty_slots, info->max_blocks);

        printk(KERN_INFO "  Free:\n");
        nr = rh_get_stats(info, RHGS_FREE, maxnr, st);
        if (nr > maxnr)
                nr = maxnr;
        for (i = 0; i < nr; i++)
                printk(KERN_INFO
                       "    0x%lx-0x%lx (%u)\n",
                       st[i].start, st[i].start + st[i].size,
                       st[i].size);
        printk(KERN_INFO "\n");

        printk(KERN_INFO "  Taken:\n");
        nr = rh_get_stats(info, RHGS_TAKEN, maxnr, st);
        if (nr > maxnr)
                nr = maxnr;
        for (i = 0; i < nr; i++)
                printk(KERN_INFO
                       "    0x%lx-0x%lx (%u) %s\n",
                       st[i].start, st[i].start + st[i].size,
                       st[i].size, st[i].owner != NULL ? st[i].owner : "");
        printk(KERN_INFO "\n");
}
EXPORT_SYMBOL_GPL(rh_dump);

void rh_dump_blk(rh_info_t * info, rh_block_t * blk)
{
        printk(KERN_INFO
               "blk @0x%p: 0x%lx-0x%lx (%u)\n",
               blk, blk->start, blk->start + blk->size, blk->size);
}
EXPORT_SYMBOL_GPL(rh_dump_blk);