source: mainline/kernel/generic/src/mm/frame.c@ d81eaf94

/*
 * Copyright (c) 2001-2005 Jakub Jermar
 * Copyright (c) 2005 Sergey Bondari
 * Copyright (c) 2009 Martin Decky
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup genericmm
 * @{
 */

/**
 * @file
 * @brief Physical frame allocator.
 *
 * This file contains the physical frame allocator and memory zone management.
 * The frame allocator is built on top of the buddy allocator.
 *
 * @see buddy.c
 */

#include <typedefs.h>
#include <mm/frame.h>
#include <mm/reserve.h>
#include <mm/as.h>
#include <panic.h>
#include <debug.h>
#include <adt/list.h>
#include <synch/mutex.h>
#include <synch/condvar.h>
#include <arch/asm.h>
#include <arch.h>
#include <print.h>
#include <align.h>
#include <mm/slab.h>
#include <bitops.h>
#include <macros.h>
#include <config.h>
#include <str.h>

zones_t zones;

/*
 * Synchronization primitives used to sleep when there is no memory
 * available.
 */
static mutex_t mem_avail_mtx;
static condvar_t mem_avail_cv;
static size_t mem_avail_req = 0;  /**< Number of frames requested. */
static size_t mem_avail_gen = 0;  /**< Generation counter. */

/********************/
/* Helper functions */
/********************/

NO_TRACE static inline size_t frame_index(zone_t *zone, frame_t *frame)
{
        return (size_t) (frame - zone->frames);
}

NO_TRACE static inline size_t frame_index_abs(zone_t *zone, frame_t *frame)
{
        return (size_t) (frame - zone->frames) + zone->base;
}

NO_TRACE static inline bool frame_index_valid(zone_t *zone, size_t index)
{
        return (index < zone->count);
}

NO_TRACE static inline size_t make_frame_index(zone_t *zone, frame_t *frame)
{
        return (frame - zone->frames);
}

/** Initialize frame structure.
 *
 * @param frame Frame structure to be initialized.
 *
 */
NO_TRACE static void frame_initialize(frame_t *frame)
{
        frame->refcount = 1;
        frame->buddy_order = 0;
}

/*******************/
/* Zones functions */
/*******************/

/** Insert-sort zone into zones list.
 *
 * Assume interrupts are disabled and zones lock is
 * locked.
 *
 * @param base  Base frame of the newly inserted zone.
 * @param count Number of frames of the newly inserted zone.
 *
 * @return Zone number on success, -1 on error.
 *
 */
NO_TRACE static size_t zones_insert_zone(pfn_t base, size_t count,
    zone_flags_t flags)
{
        if (zones.count + 1 == ZONES_MAX) {
                printf("Maximum zone count %u exceeded!\n", ZONES_MAX);
                return (size_t) -1;
        }
        
        size_t i;
        for (i = 0; i < zones.count; i++) {
                /* Check for overlap */
                if (overlaps(zones.info[i].base, zones.info[i].count,
                    base, count)) {
                        
                        /*
                         * If the overlaping zones are of the same type
                         * and the new zone is completely within the previous
                         * one, then quietly ignore the new zone.
                         *
                         */
                        
                        if ((zones.info[i].flags != flags) ||
                            (!iswithin(zones.info[i].base, zones.info[i].count,
                            base, count))) {
                                printf("Zone (%p, %p) overlaps "
                                    "with previous zone (%p %p)!\n",
                                    (void *) PFN2ADDR(base), (void *) PFN2ADDR(count),
                                    (void *) PFN2ADDR(zones.info[i].base),
                                    (void *) PFN2ADDR(zones.info[i].count));
                        }
                        
                        return (size_t) -1;
                }
                if (base < zones.info[i].base)
                        break;
        }
        
        /* Move other zones up */
        size_t j;
        for (j = zones.count; j > i; j--) {
                zones.info[j] = zones.info[j - 1];
                if (zones.info[j].buddy_system != NULL)
                        zones.info[j].buddy_system->data =
                            (void *) &zones.info[j];
        }
        
        zones.count++;
        
        return i;
}

/** Get total available frames.
 *
 * Assume interrupts are disabled and zones lock is
 * locked.
 *
 * @return Total number of available frames.
 *
 */
NO_TRACE static size_t frame_total_free_get_internal(void)
{
        size_t total = 0;
        size_t i;

        for (i = 0; i < zones.count; i++)
                total += zones.info[i].free_count;
        
        return total;
}

NO_TRACE size_t frame_total_free_get(void)
{
        size_t total;

        irq_spinlock_lock(&zones.lock, true);
        total = frame_total_free_get_internal();
        irq_spinlock_unlock(&zones.lock, true);

        return total;
}


/** Find a zone with a given frames.
 *
 * Assume interrupts are disabled and zones lock is
 * locked.
 *
 * @param frame Frame number contained in zone.
 * @param count Number of frames to look for.
 * @param hint  Used as zone hint.
 *
 * @return Zone index or -1 if not found.
 *
 */
NO_TRACE size_t find_zone(pfn_t frame, size_t count, size_t hint)
{
        if (hint >= zones.count)
                hint = 0;
        
        size_t i = hint;
        do {
                if ((zones.info[i].base <= frame)
                    && (zones.info[i].base + zones.info[i].count >= frame + count))
                        return i;
                
                i++;
                if (i >= zones.count)
                        i = 0;
                
        } while (i != hint);
        
        return (size_t) -1;
}

/** @return True if zone can allocate specified order */
NO_TRACE static bool zone_can_alloc(zone_t *zone, uint8_t order)
{
        return ((zone->flags & ZONE_AVAILABLE) &&
            buddy_system_can_alloc(zone->buddy_system, order));
}

/** Find a zone that can allocate order frames.
 *
 * Assume interrupts are disabled and zones lock is
 * locked.
 *
 * @param order Size (2^order) of free space we are trying to find.
 * @param flags Required flags of the target zone.
 * @param hind  Preferred zone.
 *
 */
NO_TRACE static size_t find_free_zone(uint8_t order, zone_flags_t flags,
    size_t hint)
{
        if (hint >= zones.count)
                hint = 0;
        
        size_t i = hint;
        do {
                /*
                 * Check whether the zone meets the search criteria.
                 */
                if (ZONE_FLAGS_MATCH(zones.info[i].flags, flags)) {
                        /*
                         * Check if the zone has 2^order frames area available.
                         */
                        if (zone_can_alloc(&zones.info[i], order))
                                return i;
                }
                
                i++;
                if (i >= zones.count)
                        i = 0;
                
        } while (i != hint);
        
        return (size_t) -1;
}

/**************************/
/* Buddy system functions */
/**************************/

/** Buddy system find_block implementation.
 *
 * Find block that is parent of current list.
 * That means go to lower addresses, until such block is found
 *
 * @param order Order of parent must be different then this
 *              parameter!!
 *
 */
NO_TRACE static link_t *zone_buddy_find_block(buddy_system_t *buddy,
    link_t *child, uint8_t order)
{
        frame_t *frame = list_get_instance(child, frame_t, buddy_link);
        zone_t *zone = (zone_t *) buddy->data;
        
        size_t index = frame_index(zone, frame);
        do {
                if (zone->frames[index].buddy_order != order)
                        return &zone->frames[index].buddy_link;
        } while (index-- > 0);
        
        return NULL;
}

/** Buddy system find_buddy implementation.
 *
 * @param buddy Buddy system.
 * @param block Block for which buddy should be found.
 *
 * @return Buddy for given block if found.
 *
 */
NO_TRACE static link_t *zone_buddy_find_buddy(buddy_system_t *buddy,
    link_t *block)
{
        frame_t *frame = list_get_instance(block, frame_t, buddy_link);
        zone_t *zone = (zone_t *) buddy->data;
        ASSERT(IS_BUDDY_ORDER_OK(frame_index_abs(zone, frame),
            frame->buddy_order));
        
        bool is_left = IS_BUDDY_LEFT_BLOCK_ABS(zone, frame);
        
        size_t index;
        if (is_left) {
                index = (frame_index(zone, frame)) +
                    (1 << frame->buddy_order);
        } else {  /* is_right */
                index = (frame_index(zone, frame)) -
                    (1 << frame->buddy_order);
        }
        
        if (frame_index_valid(zone, index)) {
                if ((zone->frames[index].buddy_order == frame->buddy_order) &&
                    (zone->frames[index].refcount == 0)) {
                        return &zone->frames[index].buddy_link;
                }
        }
        
        return NULL;
}

/** Buddy system bisect implementation.
 *
 * @param buddy Buddy system.
 * @param block Block to bisect.
 *
 * @return Right block.
 *
 */
NO_TRACE static link_t *zone_buddy_bisect(buddy_system_t *buddy, link_t *block)
{
        frame_t *frame_l = list_get_instance(block, frame_t, buddy_link);
        frame_t *frame_r = (frame_l + (1 << (frame_l->buddy_order - 1)));
        
        return &frame_r->buddy_link;
}

/** Buddy system coalesce implementation.
 *
 * @param buddy   Buddy system.
 * @param block_1 First block.
 * @param block_2 First block's buddy.
 *
 * @return Coalesced block (actually block that represents lower
 *         address).
 *
 */
NO_TRACE static link_t *zone_buddy_coalesce(buddy_system_t *buddy,
    link_t *block_1, link_t *block_2)
{
        frame_t *frame1 = list_get_instance(block_1, frame_t, buddy_link);
        frame_t *frame2 = list_get_instance(block_2, frame_t, buddy_link);
        
        return ((frame1 < frame2) ? block_1 : block_2);
}

/** Buddy system set_order implementation.
 *
 * @param buddy Buddy system.
 * @param block Buddy system block.
 * @param order Order to set.
 *
 */
NO_TRACE static void zone_buddy_set_order(buddy_system_t *buddy, link_t *block,
    uint8_t order)
{
        list_get_instance(block, frame_t, buddy_link)->buddy_order = order;
}

/** Buddy system get_order implementation.
 *
 * @param buddy Buddy system.
 * @param block Buddy system block.
 *
 * @return Order of block.
 *
 */
NO_TRACE static uint8_t zone_buddy_get_order(buddy_system_t *buddy,
    link_t *block)
{
        return list_get_instance(block, frame_t, buddy_link)->buddy_order;
}

/** Buddy system mark_busy implementation.
 *
 * @param buddy Buddy system.
 * @param block Buddy system block.
 *
 */
NO_TRACE static void zone_buddy_mark_busy(buddy_system_t *buddy, link_t *block)
{
        list_get_instance(block, frame_t, buddy_link)->refcount = 1;
}

/** Buddy system mark_available implementation.
 *
 * @param buddy Buddy system.
 * @param block Buddy system block.
 *
 */
NO_TRACE static void zone_buddy_mark_available(buddy_system_t *buddy,
    link_t *block)
{
        list_get_instance(block, frame_t, buddy_link)->refcount = 0;
}

static buddy_system_operations_t zone_buddy_system_operations = {
        .find_buddy = zone_buddy_find_buddy,
        .bisect = zone_buddy_bisect,
        .coalesce = zone_buddy_coalesce,
        .set_order = zone_buddy_set_order,
        .get_order = zone_buddy_get_order,
        .mark_busy = zone_buddy_mark_busy,
        .mark_available = zone_buddy_mark_available,
        .find_block = zone_buddy_find_block
};

/******************/
/* Zone functions */
/******************/

/** Allocate frame in particular zone.
 *
 * Assume zone is locked and is available for allocation.
 * Panics if allocation is impossible.
 *
 * @param zone  Zone to allocate from.
 * @param order Allocate exactly 2^order frames.
 *
 * @return Frame index in zone.
 *
 */
NO_TRACE static pfn_t zone_frame_alloc(zone_t *zone, uint8_t order)
{
        ASSERT(zone->flags & ZONE_AVAILABLE);
        
        /* Allocate frames from zone buddy system */
        link_t *link = buddy_system_alloc(zone->buddy_system, order);
        
        ASSERT(link);
        
        /* Update zone information. */
        zone->free_count -= (1 << order);
        zone->busy_count += (1 << order);
        
        /* Frame will be actually a first frame of the block. */
        frame_t *frame = list_get_instance(link, frame_t, buddy_link);
        
        /* Get frame address */
        return make_frame_index(zone, frame);
}

/** Free frame from zone.
 *
 * Assume zone is locked and is available for deallocation.
 *
 * @param zone      Pointer to zone from which the frame is to be freed.
 * @param frame_idx Frame index relative to zone.
 *
 * @return          Number of freed frames.
 *
 */
NO_TRACE static size_t zone_frame_free(zone_t *zone, size_t frame_idx)
{
        ASSERT(zone->flags & ZONE_AVAILABLE);
        
        frame_t *frame = &zone->frames[frame_idx];
        size_t size = 0;
        
        ASSERT(frame->refcount);
        
        if (!--frame->refcount) {
                size = 1 << frame->buddy_order;
                buddy_system_free(zone->buddy_system, &frame->buddy_link);              
                /* Update zone information. */
                zone->free_count += size;
                zone->busy_count -= size;
        }
        
        return size;
}

/** Return frame from zone. */
NO_TRACE static frame_t *zone_get_frame(zone_t *zone, size_t frame_idx)
{
        ASSERT(frame_idx < zone->count);
        return &zone->frames[frame_idx];
}

/** Mark frame in zone unavailable to allocation. */
NO_TRACE static void zone_mark_unavailable(zone_t *zone, size_t frame_idx)
{
        ASSERT(zone->flags & ZONE_AVAILABLE);
        
        frame_t *frame = zone_get_frame(zone, frame_idx);
        if (frame->refcount)
                return;
        
        link_t *link __attribute__ ((unused));
        
        link = buddy_system_alloc_block(zone->buddy_system,
            &frame->buddy_link);
        
        ASSERT(link);
        zone->free_count--;
        reserve_force_alloc(1);
}

/** Merge two zones.
 *
 * Expect buddy to point to space at least zone_conf_size large.
 * Assume z1 & z2 are locked and compatible and zones lock is
 * locked.
 *
 * @param z1     First zone to merge.
 * @param z2     Second zone to merge.
 * @param old_z1 Original date of the first zone.
 * @param buddy  Merged zone buddy.
 *
 */
NO_TRACE static void zone_merge_internal(size_t z1, size_t z2, zone_t *old_z1,
    buddy_system_t *buddy)
{
        ASSERT(zones.info[z1].flags & ZONE_AVAILABLE);
        ASSERT(zones.info[z2].flags & ZONE_AVAILABLE);
        ASSERT(zones.info[z1].flags == zones.info[z2].flags);
        ASSERT(zones.info[z1].base < zones.info[z2].base);
        ASSERT(!overlaps(zones.info[z1].base, zones.info[z1].count,
            zones.info[z2].base, zones.info[z2].count));
        
        /* Difference between zone bases */
        pfn_t base_diff = zones.info[z2].base - zones.info[z1].base;
        
        zones.info[z1].count = base_diff + zones.info[z2].count;
        zones.info[z1].free_count += zones.info[z2].free_count;
        zones.info[z1].busy_count += zones.info[z2].busy_count;
        zones.info[z1].buddy_system = buddy;
        
        uint8_t order = fnzb(zones.info[z1].count);
        buddy_system_create(zones.info[z1].buddy_system, order,
            &zone_buddy_system_operations, (void *) &zones.info[z1]);
        
        zones.info[z1].frames =
            (frame_t *) ((uint8_t *) zones.info[z1].buddy_system
            + buddy_conf_size(order));
        
        /* This marks all frames busy */
        size_t i;
        for (i = 0; i < zones.info[z1].count; i++)
                frame_initialize(&zones.info[z1].frames[i]);
        
        /* Copy frames from both zones to preserve full frame orders,
         * parents etc. Set all free frames with refcount = 0 to 1, because
         * we add all free frames to buddy allocator later again, clearing
         * order to 0. Don't set busy frames with refcount = 0, as they
         * will not be reallocated during merge and it would make later
         * problems with allocation/free.
         */
        for (i = 0; i < old_z1->count; i++)
                zones.info[z1].frames[i] = old_z1->frames[i];
        
        for (i = 0; i < zones.info[z2].count; i++)
                zones.info[z1].frames[base_diff + i]
                    = zones.info[z2].frames[i];
        
        i = 0;
        while (i < zones.info[z1].count) {
                if (zones.info[z1].frames[i].refcount) {
                        /* Skip busy frames */
                        i += 1 << zones.info[z1].frames[i].buddy_order;
                } else {
                        /* Free frames, set refcount = 1
                         * (all free frames have refcount == 0, we need not
                         * to check the order)
                         */
                        zones.info[z1].frames[i].refcount = 1;
                        zones.info[z1].frames[i].buddy_order = 0;
                        i++;
                }
        }
        
        /* Add free blocks from the original zone z1 */
        while (zone_can_alloc(old_z1, 0)) {
                /* Allocate from the original zone */
                pfn_t frame_idx = zone_frame_alloc(old_z1, 0);
                
                /* Free the frame from the merged zone */
                frame_t *frame = &zones.info[z1].frames[frame_idx];
                frame->refcount = 0;
                buddy_system_free(zones.info[z1].buddy_system, &frame->buddy_link);
        }
        
        /* Add free blocks from the original zone z2 */
        while (zone_can_alloc(&zones.info[z2], 0)) {
                /* Allocate from the original zone */
                pfn_t frame_idx = zone_frame_alloc(&zones.info[z2], 0);
                
                /* Free the frame from the merged zone */
                frame_t *frame = &zones.info[z1].frames[base_diff + frame_idx];
                frame->refcount = 0;
                buddy_system_free(zones.info[z1].buddy_system, &frame->buddy_link);
        }
}

/** Return old configuration frames into the zone.
 *
 * We have two cases:
 * - The configuration data is outside the zone
 *   -> do nothing (perhaps call frame_free?)
 * - The configuration data was created by zone_create
 *   or updated by reduce_region -> free every frame
 *
 * @param znum  The actual zone where freeing should occur.
 * @param pfn   Old zone configuration frame.
 * @param count Old zone frame count.
 *
 */
NO_TRACE static void return_config_frames(size_t znum, pfn_t pfn, size_t count)
{
        ASSERT(zones.info[znum].flags & ZONE_AVAILABLE);
        
        size_t cframes = SIZE2FRAMES(zone_conf_size(count));
        
        if ((pfn < zones.info[znum].base)
            || (pfn >= zones.info[znum].base + zones.info[znum].count))
                return;
        
        frame_t *frame __attribute__ ((unused));

        frame = &zones.info[znum].frames[pfn - zones.info[znum].base];
        ASSERT(!frame->buddy_order);
        
        size_t i;
        for (i = 0; i < cframes; i++) {
                zones.info[znum].busy_count++;
                (void) zone_frame_free(&zones.info[znum],
                    pfn - zones.info[znum].base + i);
        }
}

/** Reduce allocated block to count of order 0 frames.
 *
 * The allocated block needs 2^order frames. Reduce all frames
 * in the block to order 0 and free the unneeded frames. This means that
 * when freeing the previously allocated block starting with frame_idx,
 * you have to free every frame.
 *
 * @param znum      Zone.
 * @param frame_idx Index the first frame of the block.
 * @param count     Allocated frames in block.
 *
 */
NO_TRACE static void zone_reduce_region(size_t znum, pfn_t frame_idx,
    size_t count)
{
        ASSERT(zones.info[znum].flags & ZONE_AVAILABLE);
        ASSERT(frame_idx + count < zones.info[znum].count);
        
        uint8_t order = zones.info[znum].frames[frame_idx].buddy_order;
        ASSERT((size_t) (1 << order) >= count);
        
        /* Reduce all blocks to order 0 */
        size_t i;
        for (i = 0; i < (size_t) (1 << order); i++) {
                frame_t *frame = &zones.info[znum].frames[i + frame_idx];
                frame->buddy_order = 0;
                if (!frame->refcount)
                        frame->refcount = 1;
                ASSERT(frame->refcount == 1);
        }
        
        /* Free unneeded frames */
        for (i = count; i < (size_t) (1 << order); i++)
                (void) zone_frame_free(&zones.info[znum], i + frame_idx);
}

/** Merge zones z1 and z2.
 *
 * The merged zones must be 2 zones with no zone existing in between
 * (which means that z2 = z1 + 1). Both zones must be available zones
 * with the same flags.
 *
 * When you create a new zone, the frame allocator configuration does
 * not to be 2^order size. Once the allocator is running it is no longer
 * possible, merged configuration data occupies more space :-/
 *
 */
bool zone_merge(size_t z1, size_t z2)
{
        irq_spinlock_lock(&zones.lock, true);
        
        bool ret = true;
        
        /* We can join only 2 zones with none existing inbetween,
         * the zones have to be available and with the same
         * set of flags
         */
        if ((z1 >= zones.count) || (z2 >= zones.count) || (z2 - z1 != 1) ||
            (zones.info[z1].flags != zones.info[z2].flags)) {
                ret = false;
                goto errout;
        }
        
        pfn_t cframes = SIZE2FRAMES(zone_conf_size(
            zones.info[z2].base - zones.info[z1].base
            + zones.info[z2].count));
        
        uint8_t order;
        if (cframes == 1)
                order = 0;
        else
                order = fnzb(cframes - 1) + 1;
        
        /* Allocate merged zone data inside one of the zones */
        pfn_t pfn;
        if (zone_can_alloc(&zones.info[z1], order)) {
                pfn = zones.info[z1].base + zone_frame_alloc(&zones.info[z1], order);
        } else if (zone_can_alloc(&zones.info[z2], order)) {
                pfn = zones.info[z2].base + zone_frame_alloc(&zones.info[z2], order);
        } else {
                ret = false;
                goto errout;
        }
        
        /* Preserve original data from z1 */
        zone_t old_z1 = zones.info[z1];
        old_z1.buddy_system->data = (void *) &old_z1;
        
        /* Do zone merging */
        buddy_system_t *buddy = (buddy_system_t *) PA2KA(PFN2ADDR(pfn));
        zone_merge_internal(z1, z2, &old_z1, buddy);
        
        /* Free unneeded config frames */
        zone_reduce_region(z1, pfn - zones.info[z1].base, cframes);
        
        /* Subtract zone information from busy frames */
        zones.info[z1].busy_count -= cframes;
        
        /* Free old zone information */
        return_config_frames(z1,
            ADDR2PFN(KA2PA((uintptr_t) old_z1.frames)), old_z1.count);
        return_config_frames(z1,
            ADDR2PFN(KA2PA((uintptr_t) zones.info[z2].frames)),
            zones.info[z2].count);
        
        /* Move zones down */
        size_t i;
        for (i = z2 + 1; i < zones.count; i++) {
                zones.info[i - 1] = zones.info[i];
                if (zones.info[i - 1].buddy_system != NULL)
                        zones.info[i - 1].buddy_system->data =
                            (void *) &zones.info[i - 1];
        }
        
        zones.count--;
        
errout:
        irq_spinlock_unlock(&zones.lock, true);
        
        return ret;
}

/** Merge all mergeable zones into one big zone.
 *
 * It is reasonable to do this on systems where
 * BIOS reports parts in chunks, so that we could
 * have 1 zone (it's faster).
 *
 */
void zone_merge_all(void)
{
        size_t i = 0;
        while (i < zones.count) {
                if (!zone_merge(i, i + 1))
                        i++;
        }
}

/** Create new frame zone.
 *
 * @param zone  Zone to construct.
 * @param buddy Address of buddy system configuration information.
 * @param start Physical address of the first frame within the zone.
 * @param count Count of frames in zone.
 * @param flags Zone flags.
 *
 * @return Initialized zone.
 *
 */
NO_TRACE static void zone_construct(zone_t *zone, buddy_system_t *buddy,
    pfn_t start, size_t count, zone_flags_t flags)
{
        zone->base = start;
        zone->count = count;
        zone->flags = flags;
        zone->free_count = count;
        zone->busy_count = 0;
        zone->buddy_system = buddy;
        
        if (flags & ZONE_AVAILABLE) {
                /*
                 * Compute order for buddy system and initialize
                 */
                uint8_t order = fnzb(count);
                buddy_system_create(zone->buddy_system, order,
                    &zone_buddy_system_operations, (void *) zone);
                
                /* Allocate frames _after_ the confframe */
                
                /* Check sizes */
                zone->frames = (frame_t *) ((uint8_t *) zone->buddy_system +
                    buddy_conf_size(order));
                
                size_t i;
                for (i = 0; i < count; i++)
                        frame_initialize(&zone->frames[i]);
                
                /* Stuffing frames */
                for (i = 0; i < count; i++) {
                        zone->frames[i].refcount = 0;
                        buddy_system_free(zone->buddy_system, &zone->frames[i].buddy_link);
                }
        } else
                zone->frames = NULL;
}

/** Compute configuration data size for zone.
 *
 * @param count Size of zone in frames.
 *
 * @return Size of zone configuration info (in bytes).
 *
 */
size_t zone_conf_size(size_t count)
{
        return (count * sizeof(frame_t) + buddy_conf_size(fnzb(count)));
}

/** Allocate external configuration frames from low memory. */
pfn_t zone_external_conf_alloc(size_t count)
{
        size_t size = zone_conf_size(count);
        size_t order = ispwr2(size) ? fnzb(size) : (fnzb(size) + 1);

        return ADDR2PFN((uintptr_t) frame_alloc(order - FRAME_WIDTH,
            FRAME_LOWMEM | FRAME_ATOMIC));
}

/** Create and add zone to system.
 *
 * @param start     First frame number (absolute).
 * @param count     Size of zone in frames.
 * @param confframe Where configuration frames are supposed to be.
 *                  Automatically checks, that we will not disturb the
 *                  kernel and possibly init. If confframe is given
 *                  _outside_ this zone, it is expected, that the area is
 *                  already marked BUSY and big enough to contain
 *                  zone_conf_size() amount of data. If the confframe is
 *                  inside the area, the zone free frame information is
 *                  modified not to include it.
 *
 * @return Zone number or -1 on error.
 *
 */
size_t zone_create(pfn_t start, size_t count, pfn_t confframe,
    zone_flags_t flags)
{
        irq_spinlock_lock(&zones.lock, true);
        
        if (flags & ZONE_AVAILABLE) {  /* Create available zone */
                /* Theoretically we could have NULL here, practically make sure
                 * nobody tries to do that. If some platform requires, remove
                 * the assert
                 */
                ASSERT(confframe != ADDR2PFN((uintptr_t ) NULL));

                /* Update the known end of physical memory. */
                config.physmem_end = max(config.physmem_end, PFN2ADDR(start + count));
                
                /* If confframe is supposed to be inside our zone, then make sure
                 * it does not span kernel & init
                 */
                size_t confcount = SIZE2FRAMES(zone_conf_size(count));
                if ((confframe >= start) && (confframe < start + count)) {
                        for (; confframe < start + count; confframe++) {
                                uintptr_t addr = PFN2ADDR(confframe);
                                if (overlaps(addr, PFN2ADDR(confcount),
                                    KA2PA(config.base), config.kernel_size))
                                        continue;
                                
                                if (overlaps(addr, PFN2ADDR(confcount),
                                    KA2PA(config.stack_base), config.stack_size))
                                        continue;
                                
                                bool overlap = false;
                                size_t i;
                                for (i = 0; i < init.cnt; i++)
                                        if (overlaps(addr, PFN2ADDR(confcount),
                                            KA2PA(init.tasks[i].addr),
                                            init.tasks[i].size)) {
                                                overlap = true;
                                                break;
                                        }
                                if (overlap)
                                        continue;
                                
                                break;
                        }
                        
                        if (confframe >= start + count)
                                panic("Cannot find configuration data for zone.");
                }
                
                size_t znum = zones_insert_zone(start, count, flags);
                if (znum == (size_t) -1) {
                        irq_spinlock_unlock(&zones.lock, true);
                        return (size_t) -1;
                }
                
                buddy_system_t *buddy = (buddy_system_t *) PA2KA(PFN2ADDR(confframe));
                zone_construct(&zones.info[znum], buddy, start, count, flags);
                
                /* If confdata in zone, mark as unavailable */
                if ((confframe >= start) && (confframe < start + count)) {
                        size_t i;
                        for (i = confframe; i < confframe + confcount; i++)
                                zone_mark_unavailable(&zones.info[znum],
                                    i - zones.info[znum].base);
                }
                
                irq_spinlock_unlock(&zones.lock, true);
                
                return znum;
        }
        
        /* Non-available zone */
        size_t znum = zones_insert_zone(start, count, flags);
        if (znum == (size_t) -1) {
                irq_spinlock_unlock(&zones.lock, true);
                return (size_t) -1;
        }
        zone_construct(&zones.info[znum], NULL, start, count, flags);
        
        irq_spinlock_unlock(&zones.lock, true);
        
        return znum;
}

/*******************/
/* Frame functions */
/*******************/

/** Set parent of frame. */
void frame_set_parent(pfn_t pfn, void *data, size_t hint)
{
        irq_spinlock_lock(&zones.lock, true);
        
        size_t znum = find_zone(pfn, 1, hint);
        
        ASSERT(znum != (size_t) -1);
        
        zone_get_frame(&zones.info[znum],
            pfn - zones.info[znum].base)->parent = data;
        
        irq_spinlock_unlock(&zones.lock, true);
}

void *frame_get_parent(pfn_t pfn, size_t hint)
{
        irq_spinlock_lock(&zones.lock, true);
        
        size_t znum = find_zone(pfn, 1, hint);
        
        ASSERT(znum != (size_t) -1);
        
        void *res = zone_get_frame(&zones.info[znum],
            pfn - zones.info[znum].base)->parent;
        
        irq_spinlock_unlock(&zones.lock, true);
        
        return res;
}

/** Allocate power-of-two frames of physical memory.
 *
 * @param order Allocate exactly 2^order frames.
 * @param flags Flags for host zone selection and address processing.
 * @param pzone Preferred zone.
 *
 * @return Physical address of the allocated frame.
 *
 */
void *frame_alloc_generic(uint8_t order, frame_flags_t flags, size_t *pzone)
{
        size_t size = ((size_t) 1) << order;
        size_t hint = pzone ? (*pzone) : 0;
        
        /*
         * If not told otherwise, we must first reserve the memory.
         */
        if (!(flags & FRAME_NO_RESERVE)) 
                reserve_force_alloc(size);

loop:
        irq_spinlock_lock(&zones.lock, true);
        
        /*
         * First, find suitable frame zone.
         */
        size_t znum = find_free_zone(order,
            FRAME_TO_ZONE_FLAGS(flags), hint);
        
        /* If no memory, reclaim some slab memory,
           if it does not help, reclaim all */
        if ((znum == (size_t) -1) && (!(flags & FRAME_NO_RECLAIM))) {
                irq_spinlock_unlock(&zones.lock, true);
                size_t freed = slab_reclaim(0);
                irq_spinlock_lock(&zones.lock, true);
                
                if (freed > 0)
                        znum = find_free_zone(order,
                            FRAME_TO_ZONE_FLAGS(flags), hint);
                
                if (znum == (size_t) -1) {
                        irq_spinlock_unlock(&zones.lock, true);
                        freed = slab_reclaim(SLAB_RECLAIM_ALL);
                        irq_spinlock_lock(&zones.lock, true);
                        
                        if (freed > 0)
                                znum = find_free_zone(order,
                                    FRAME_TO_ZONE_FLAGS(flags), hint);
                }
        }
        
        if (znum == (size_t) -1) {
                if (flags & FRAME_ATOMIC) {
                        irq_spinlock_unlock(&zones.lock, true);
                        if (!(flags & FRAME_NO_RESERVE))
                                reserve_free(size);
                        return NULL;
                }
                
#ifdef CONFIG_DEBUG
                size_t avail = frame_total_free_get_internal();
#endif
                
                irq_spinlock_unlock(&zones.lock, true);
                
                if (!THREAD)
                        panic("Cannot wait for memory to become available.");
                
                /*
                 * Sleep until some frames are available again.
                 */
                
#ifdef CONFIG_DEBUG
                printf("Thread %" PRIu64 " waiting for %zu frames, "
                    "%zu available.\n", THREAD->tid, size, avail);
#endif
                
                mutex_lock(&mem_avail_mtx);
                
                if (mem_avail_req > 0)
                        mem_avail_req = min(mem_avail_req, size);
                else
                        mem_avail_req = size;
                size_t gen = mem_avail_gen;
                
                while (gen == mem_avail_gen)
                        condvar_wait(&mem_avail_cv, &mem_avail_mtx);
                
                mutex_unlock(&mem_avail_mtx);
                
#ifdef CONFIG_DEBUG
                printf("Thread %" PRIu64 " woken up.\n", THREAD->tid);
#endif
                
                goto loop;
        }
        
        pfn_t pfn = zone_frame_alloc(&zones.info[znum], order)
            + zones.info[znum].base;
        
        irq_spinlock_unlock(&zones.lock, true);
        
        if (pzone)
                *pzone = znum;
        
        if (flags & FRAME_KA)
                return (void *) PA2KA(PFN2ADDR(pfn));
        
        return (void *) PFN2ADDR(pfn);
}

void *frame_alloc(uint8_t order, frame_flags_t flags)
{
        return frame_alloc_generic(order, flags, NULL);
}

void *frame_alloc_noreserve(uint8_t order, frame_flags_t flags)
{
        return frame_alloc_generic(order, flags | FRAME_NO_RESERVE, NULL);
}

/** Free a frame.
 *
 * Find respective frame structure for supplied physical frame address.
 * Decrement frame reference count. If it drops to zero, move the frame
 * structure to free list.
 *
 * @param frame Physical Address of of the frame to be freed.
 * @param flags Flags to control memory reservation.
 *
 */
void frame_free_generic(uintptr_t frame, frame_flags_t flags)
{
        size_t size;
        
        irq_spinlock_lock(&zones.lock, true);
        
        /*
         * First, find host frame zone for addr.
         */
        pfn_t pfn = ADDR2PFN(frame);
        size_t znum = find_zone(pfn, 1, 0);

        ASSERT(znum != (size_t) -1);
        
        size = zone_frame_free(&zones.info[znum], pfn - zones.info[znum].base);
        
        irq_spinlock_unlock(&zones.lock, true);
        
        /*
         * Signal that some memory has been freed.
         */
        mutex_lock(&mem_avail_mtx);
        if (mem_avail_req > 0)
                mem_avail_req -= min(mem_avail_req, size);
        
        if (mem_avail_req == 0) {
                mem_avail_gen++;
                condvar_broadcast(&mem_avail_cv);
        }
        mutex_unlock(&mem_avail_mtx);
        
        if (!(flags & FRAME_NO_RESERVE))
                reserve_free(size);
}

void frame_free(uintptr_t frame)
{
        frame_free_generic(frame, 0);
}

void frame_free_noreserve(uintptr_t frame)
{
        frame_free_generic(frame, FRAME_NO_RESERVE);
}

/** Add reference to frame.
 *
 * Find respective frame structure for supplied PFN and
 * increment frame reference count.
 *
 * @param pfn Frame number of the frame to be freed.
 *
 */
NO_TRACE void frame_reference_add(pfn_t pfn)
{
        irq_spinlock_lock(&zones.lock, true);
        
        /*
         * First, find host frame zone for addr.
         */
        size_t znum = find_zone(pfn, 1, 0);
        
        ASSERT(znum != (size_t) -1);
        
        zones.info[znum].frames[pfn - zones.info[znum].base].refcount++;
        
        irq_spinlock_unlock(&zones.lock, true);
}

/** Mark given range unavailable in frame zones.
 *
 */
NO_TRACE void frame_mark_unavailable(pfn_t start, size_t count)
{
        irq_spinlock_lock(&zones.lock, true);
        
        size_t i;
        for (i = 0; i < count; i++) {
                size_t znum = find_zone(start + i, 1, 0);
                if (znum == (size_t) -1)  /* PFN not found */
                        continue;
                
                zone_mark_unavailable(&zones.info[znum],
                    start + i - zones.info[znum].base);
        }
        
        irq_spinlock_unlock(&zones.lock, true);
}

/** Initialize physical memory management.
 *
 */
void frame_init(void)
{
        if (config.cpu_active == 1) {
                zones.count = 0;
                irq_spinlock_initialize(&zones.lock, "frame.zones.lock");
                mutex_initialize(&mem_avail_mtx, MUTEX_ACTIVE);
                condvar_initialize(&mem_avail_cv);
        }
        
        /* Tell the architecture to create some memory */
        frame_low_arch_init();
        if (config.cpu_active == 1) {
                frame_mark_unavailable(ADDR2PFN(KA2PA(config.base)),
                    SIZE2FRAMES(config.kernel_size));
                frame_mark_unavailable(ADDR2PFN(KA2PA(config.stack_base)),
                    SIZE2FRAMES(config.stack_size));
                
                size_t i;
                for (i = 0; i < init.cnt; i++) {
                        pfn_t pfn = ADDR2PFN(KA2PA(init.tasks[i].addr));
                        frame_mark_unavailable(pfn,
                            SIZE2FRAMES(init.tasks[i].size));
                }
                
                if (ballocs.size)
                        frame_mark_unavailable(ADDR2PFN(KA2PA(ballocs.base)),
                            SIZE2FRAMES(ballocs.size));
                
                /* Black list first frame, as allocating NULL would
                 * fail in some places
                 */
                frame_mark_unavailable(0, 1);
        }
        frame_high_arch_init();
}

/** Adjust bounds of physical memory region according to low/high memory split.
 *
 * @param low[in]       If true, the adujstment is performed to make the region
 *                      fit in the low memory. Otherwise the adjustment is
 *                      performed to make the region fit in the high memory.
 * @param basep[inout]  Pointer to a variable which contains the region's base
 *                      address and which may receive the adjusted base address.
 * @param sizep[inout]  Pointer to a variable which contains the region's size
 *                      and which may receive the adjusted size.
 * @retun               True if the region still exists even after the
 *                      adjustment, false otherwise.
 */
bool frame_adjust_zone_bounds(bool low, uintptr_t *basep, size_t *sizep)
{
        uintptr_t limit = config.identity_size;

        if (low) {
                if (*basep > limit)
                        return false;
                if (*basep + *sizep > limit)
                        *sizep = limit - *basep;
        } else {
                if (*basep + *sizep <= limit)
                        return false;
                if (*basep <= limit) {
                        *sizep -= limit - *basep;
                        *basep = limit;
                }
        }
        return true;
}

/** Return total size of all zones.
 *
 */
uint64_t zones_total_size(void)
{
        irq_spinlock_lock(&zones.lock, true);
        
        uint64_t total = 0;
        size_t i;
        for (i = 0; i < zones.count; i++)
                total += (uint64_t) FRAMES2SIZE(zones.info[i].count);
        
        irq_spinlock_unlock(&zones.lock, true);
        
        return total;
}

void zones_stats(uint64_t *total, uint64_t *unavail, uint64_t *busy,
    uint64_t *free)
{
        ASSERT(total != NULL);
        ASSERT(unavail != NULL);
        ASSERT(busy != NULL);
        ASSERT(free != NULL);
        
        irq_spinlock_lock(&zones.lock, true);
        
        *total = 0;
        *unavail = 0;
        *busy = 0;
        *free = 0;
        
        size_t i;
        for (i = 0; i < zones.count; i++) {
                *total += (uint64_t) FRAMES2SIZE(zones.info[i].count);
                
                if (zones.info[i].flags & ZONE_AVAILABLE) {
                        *busy += (uint64_t) FRAMES2SIZE(zones.info[i].busy_count);
                        *free += (uint64_t) FRAMES2SIZE(zones.info[i].free_count);
                } else
                        *unavail += (uint64_t) FRAMES2SIZE(zones.info[i].count);
        }
        
        irq_spinlock_unlock(&zones.lock, true);
}

/** Prints list of zones.
 *
 */
void zones_print_list(void)
{
#ifdef __32_BITS__
        printf("[nr] [base addr] [frames    ] [flags ] [free frames ] [busy frames ]\n");
#endif

#ifdef __64_BITS__
        printf("[nr] [base address    ] [frames    ] [flags ] [free frames ] [busy frames ]\n");
#endif
        
        /*
         * Because printing may require allocation of memory, we may not hold
         * the frame allocator locks when printing zone statistics.  Therefore,
         * we simply gather the statistics under the protection of the locks and
         * print the statistics when the locks have been released.
         *
         * When someone adds/removes zones while we are printing the statistics,
         * we may end up with inaccurate output (e.g. a zone being skipped from
         * the listing).
         */
        
        size_t i;
        for (i = 0;; i++) {
                irq_spinlock_lock(&zones.lock, true);
                
                if (i >= zones.count) {
                        irq_spinlock_unlock(&zones.lock, true);
                        break;
                }
                
                uintptr_t base = PFN2ADDR(zones.info[i].base);
                size_t count = zones.info[i].count;
                zone_flags_t flags = zones.info[i].flags;
                size_t free_count = zones.info[i].free_count;
                size_t busy_count = zones.info[i].busy_count;
                
                irq_spinlock_unlock(&zones.lock, true);
                
                bool available = ((flags & ZONE_AVAILABLE) != 0);
                
                printf("%-4zu", i);
                
#ifdef __32_BITS__
                printf("  %p", (void *) base);
#endif
                
#ifdef __64_BITS__
                printf(" %p", (void *) base);
#endif
                
                printf(" %12zu %c%c%c%c%c    ", count,
                    available ? 'A' : '-',
                    (flags & ZONE_RESERVED) ? 'R' : '-',
                    (flags & ZONE_FIRMWARE) ? 'F' : '-',
                    (flags & ZONE_LOWMEM) ? 'L' : '-',
                    (flags & ZONE_HIGHMEM) ? 'H' : '-');
                
                if (available)
                        printf("%14zu %14zu",
                            free_count, busy_count);
                
                printf("\n");
        }
}

/** Prints zone details.
 *
 * @param num Zone base address or zone number.
 *
 */
void zone_print_one(size_t num)
{
        irq_spinlock_lock(&zones.lock, true);
        size_t znum = (size_t) -1;
        
        size_t i;
        for (i = 0; i < zones.count; i++) {
                if ((i == num) || (PFN2ADDR(zones.info[i].base) == num)) {
                        znum = i;
                        break;
                }
        }
        
        if (znum == (size_t) -1) {
                irq_spinlock_unlock(&zones.lock, true);
                printf("Zone not found.\n");
                return;
        }
        
        uintptr_t base = PFN2ADDR(zones.info[i].base);
        zone_flags_t flags = zones.info[i].flags;
        size_t count = zones.info[i].count;
        size_t free_count = zones.info[i].free_count;
        size_t busy_count = zones.info[i].busy_count;
        
        irq_spinlock_unlock(&zones.lock, true);
        
        bool available = ((flags & ZONE_AVAILABLE) != 0);
        
        uint64_t size;
        const char *size_suffix;
        bin_order_suffix(FRAMES2SIZE(count), &size, &size_suffix, false);
        
        printf("Zone number:       %zu\n", znum);
        printf("Zone base address: %p\n", (void *) base);
        printf("Zone size:         %zu frames (%" PRIu64 " %s)\n", count,
            size, size_suffix);
        printf("Zone flags:        %c%c%c%c%c\n",
            available ? 'A' : '-',
            (flags & ZONE_RESERVED) ? 'R' : '-',
            (flags & ZONE_FIRMWARE) ? 'F' : '-',
            (flags & ZONE_LOWMEM) ? 'L' : '-',
            (flags & ZONE_HIGHMEM) ? 'H' : '-');
        
        if (available) {
                bin_order_suffix(FRAMES2SIZE(busy_count), &size, &size_suffix,
                    false);
                printf("Allocated space:   %zu frames (%" PRIu64 " %s)\n",
                    busy_count, size, size_suffix);
                bin_order_suffix(FRAMES2SIZE(free_count), &size, &size_suffix,
                    false);
                printf("Available space:   %zu frames (%" PRIu64 " %s)\n",
                    free_count, size, size_suffix);
        }
}

/** @}
 */