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rheap.c

/*
 * 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/module.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);


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