rheap.c

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/*
 * 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 <[email protected]>
 *
 * 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(sizeof(rh_block_t) * max_blocks, 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 && info->block != NULL)
        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 adjuscent */
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);