source: mainline/kernel/generic/src/mm/frame.c@ 498b201

/*
 * Copyright (c) 2001-2005 Jakub Jermar
 * Copyright (c) 2005 Sergey Bondari
 * 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
 */

/*
 * Locking order
 *
 * In order to access particular zone, the process must first lock
 * the zones.lock, then lock the zone and then unlock the zones.lock.
 * This insures, that we can fiddle with the zones in runtime without
 * affecting the processes. 
 *
 */

#include <arch/types.h>
#include <mm/frame.h>
#include <mm/as.h>
#include <panic.h>
#include <debug.h>
#include <adt/list.h>
#include <synch/spinlock.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>

typedef struct {
        count_t refcount;       /**< tracking of shared frames  */
        uint8_t buddy_order;    /**< buddy system block order */
        link_t buddy_link;      /**< link to the next free block inside one
                                     order */
        void *parent;           /**< If allocated by slab, this points there */
} frame_t;

typedef struct {
        SPINLOCK_DECLARE(lock); /**< this lock protects everything below */
        pfn_t base;             /**< frame_no of the first frame in the frames
                                     array */
        count_t count;          /**< Size of zone */

        frame_t *frames;        /**< array of frame_t structures in this
                                     zone */
        count_t free_count;     /**< number of free frame_t structures */
        count_t busy_count;     /**< number of busy frame_t structures */
        
        buddy_system_t *buddy_system; /**< buddy system for the zone */
        int flags;
} zone_t;

/*
 * The zoneinfo.lock must be locked when accessing zoneinfo structure.
 * Some of the attributes in zone_t structures are 'read-only'
 */

typedef struct {
        SPINLOCK_DECLARE(lock);
        unsigned int count;
        zone_t *info[ZONES_MAX];
} zones_t;

static zones_t zones;

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

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

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

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

static inline int frame_index_valid(zone_t *zone, index_t index)
{
        return (index < zone->count);
}

/** Compute pfn_t from frame_t pointer & zone pointer */
static index_t make_frame_index(zone_t *zone, frame_t *frame)
{
        return (frame - zone->frames);
}

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

/**********************/
/* Zoneinfo functions */
/**********************/

/** Insert-sort zone into zones list.
 *
 * @param newzone       New zone to be inserted into zone list.
 * @return              Zone number on success, -1 on error.
 */
static int zones_add_zone(zone_t *newzone)
{
        unsigned int i, j;
        ipl_t ipl;
        zone_t *z;

        ipl = interrupts_disable();
        spinlock_lock(&zones.lock);
        
        /* Try to merge */
        if (zones.count + 1 == ZONES_MAX) {
                printf("Maximum zone count %u exceeded!\n", ZONES_MAX);
                spinlock_unlock(&zones.lock);
                interrupts_restore(ipl);
                return -1;
        }
        
        for (i = 0; i < zones.count; i++) {
                /* Check for overflow */
                z = zones.info[i];
                if (overlaps(newzone->base, newzone->count, z->base,
                    z->count)) {
                        printf("Zones overlap!\n");
                        return -1;
                }
                if (newzone->base < z->base)
                        break;
        }
        
        /* Move other zones up */
        for (j = i; j < zones.count; j++)
                zones.info[j + 1] = zones.info[j];
        
        zones.info[i] = newzone;
        zones.count++;
        
        spinlock_unlock(&zones.lock);
        interrupts_restore(ipl);

        return i;
}

/** Try to find a zone where can we find the frame.
 *
 * Assume interrupts are disabled.
 *
 * @param frame         Frame number contained in zone.
 * @param pzone         If not null, it is used as zone hint. Zone index is
 *                      filled into the variable on success. 
 * @return              Pointer to locked zone containing frame.
 */
static zone_t *find_zone_and_lock(pfn_t frame, unsigned int *pzone)
{
        unsigned int i;
        unsigned int hint = pzone ? *pzone : 0;
        zone_t *z;
        
        spinlock_lock(&zones.lock);

        if (hint >= zones.count)
                hint = 0;
        
        i = hint;
        do {
                z = zones.info[i];
                spinlock_lock(&z->lock);
                if (z->base <= frame && z->base + z->count > frame) {
                        /* Unlock the global lock */
                        spinlock_unlock(&zones.lock); 
                        if (pzone)
                                *pzone = i;
                        return z;
                }
                spinlock_unlock(&z->lock);

                i++;
                if (i >= zones.count)
                        i = 0;
        } while (i != hint);

        spinlock_unlock(&zones.lock);
        return NULL;
}

/** @return True if zone can allocate specified order */
static int zone_can_alloc(zone_t *z, uint8_t order)
{
        return buddy_system_can_alloc(z->buddy_system, order);
}

/** Find and lock zone that can allocate order frames.
 *
 * Assume interrupts are disabled.
 *
 * @param order         Size (2^order) of free space we are trying to find.
 * @param flags         Required flags of the target zone.
 * @param pzone         Pointer to preferred zone or NULL, on return contains
 *                      zone number.
 */
static zone_t *
find_free_zone_and_lock(uint8_t order, int flags, unsigned int *pzone)
{
        unsigned int i;
        zone_t *z;
        unsigned int hint = pzone ? *pzone : 0;
        
        /* Mask off flags that are not applicable. */
        flags &= FRAME_LOW_4_GiB;

        spinlock_lock(&zones.lock);
        if (hint >= zones.count)
                hint = 0;
        i = hint;
        do {
                z = zones.info[i];
                
                spinlock_lock(&z->lock);

                /*
                 * Check whether the zone meets the search criteria.
                 */
                if ((z->flags & flags) == flags) {
                        /*
                         * Check if the zone has 2^order frames area available.
                         */
                        if (zone_can_alloc(z, order)) {
                                spinlock_unlock(&zones.lock);
                                if (pzone)
                                        *pzone = i;
                                return z;
                        }
                }
                spinlock_unlock(&z->lock);
                if (++i >= zones.count)
                        i = 0;
        } while (i != hint);
        spinlock_unlock(&zones.lock);
        return NULL;
}

/**************************/
/* 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!!
 */
static link_t *zone_buddy_find_block(buddy_system_t *b, link_t *child,
    uint8_t order)
{
        frame_t *frame;
        zone_t *zone;
        index_t index;
        
        frame = list_get_instance(child, frame_t, buddy_link);
        zone = (zone_t *) b->data;

        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 b             Buddy system.
 * @param block         Block for which buddy should be found.
 *
 * @return              Buddy for given block if found.
 */
static link_t *zone_buddy_find_buddy(buddy_system_t *b, link_t *block) 
{
        frame_t *frame;
        zone_t *zone;
        index_t index;
        bool is_left, is_right;

        frame = list_get_instance(block, frame_t, buddy_link);
        zone = (zone_t *) b->data;
        ASSERT(IS_BUDDY_ORDER_OK(frame_index_abs(zone, frame),
            frame->buddy_order));
        
        is_left = IS_BUDDY_LEFT_BLOCK_ABS(zone, frame);
        is_right = IS_BUDDY_RIGHT_BLOCK_ABS(zone, frame);

        ASSERT(is_left ^ is_right);
        if (is_left) {
                index = (frame_index(zone, frame)) +
                    (1 << frame->buddy_order);
        } else {        /* if (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 b             Buddy system.
 * @param block         Block to bisect.
 *
 * @return              Right block.
 */
static link_t *zone_buddy_bisect(buddy_system_t *b, link_t *block)
{
        frame_t *frame_l, *frame_r;

        frame_l = list_get_instance(block, frame_t, buddy_link);
        frame_r = (frame_l + (1 << (frame_l->buddy_order - 1)));
        
        return &frame_r->buddy_link;
}

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

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

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

/** Buddy system mark_busy implementation.
 *
 * @param b             Buddy system.
 * @param block         Buddy system block.
 */
static void zone_buddy_mark_busy(buddy_system_t *b, link_t * block)
{
        frame_t * frame;

        frame = list_get_instance(block, frame_t, buddy_link);
        frame->refcount = 1;
}

/** Buddy system mark_available implementation.
 *
 * @param b             Buddy system.
 * @param block         Buddy system block.
 */
static void zone_buddy_mark_available(buddy_system_t *b, link_t *block)
{
        frame_t *frame;
        frame = list_get_instance(block, frame_t, buddy_link);
        frame->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.
 * Panics if allocation is impossible.
 *
 * @param zone          Zone to allocate from.
 * @param order         Allocate exactly 2^order frames.
 *
 * @return              Frame index in zone.
 *
 */
static pfn_t zone_frame_alloc(zone_t *zone, uint8_t order)
{
        pfn_t v;
        link_t *tmp;
        frame_t *frame;

        /* Allocate frames from zone buddy system */
        tmp = buddy_system_alloc(zone->buddy_system, order);
        
        ASSERT(tmp);
        
        /* Update zone information. */
        zone->free_count -= (1 << order);
        zone->busy_count += (1 << order);

        /* Frame will be actually a first frame of the block. */
        frame = list_get_instance(tmp, frame_t, buddy_link);
        
        /* get frame address */
        v = make_frame_index(zone, frame);
        return v;
}

/** Free frame from zone.
 *
 * Assume zone is locked.
 *
 * @param zone          Pointer to zone from which the frame is to be freed.
 * @param frame_idx     Frame index relative to zone.
 */
static void zone_frame_free(zone_t *zone, index_t frame_idx)
{
        frame_t *frame;
        uint8_t order;

        frame = &zone->frames[frame_idx];
        
        /* remember frame order */
        order = frame->buddy_order;

        ASSERT(frame->refcount);

        if (!--frame->refcount) {
                buddy_system_free(zone->buddy_system, &frame->buddy_link);
        
                /* Update zone information. */
                zone->free_count += (1 << order);
                zone->busy_count -= (1 << order);
        }
}

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

/** Mark frame in zone unavailable to allocation. */
static void zone_mark_unavailable(zone_t *zone, index_t frame_idx)
{
        frame_t *frame;
        link_t *link;

        frame = zone_get_frame(zone, frame_idx);
        if (frame->refcount)
                return;
        link = buddy_system_alloc_block(zone->buddy_system,
            &frame->buddy_link);
        ASSERT(link);
        zone->free_count--;

        mutex_lock(&mem_avail_mtx);
        mem_avail_frames--;
        mutex_unlock(&mem_avail_mtx);
}

/** Join two zones.
 *
 * Expect zone_t *z to point to space at least zone_conf_size large.
 *
 * Assume z1 & z2 are locked.
 *
 * @param z             Target zone structure pointer.
 * @param z1            Zone to merge.
 * @param z2            Zone to merge.
 */
static void _zone_merge(zone_t *z, zone_t *z1, zone_t *z2)
{
        uint8_t max_order;
        unsigned int i;
        int z2idx;
        pfn_t frame_idx;
        frame_t *frame;

        ASSERT(!overlaps(z1->base, z1->count, z2->base, z2->count));
        ASSERT(z1->base < z2->base);

        spinlock_initialize(&z->lock, "zone_lock");
        z->base = z1->base;
        z->count = z2->base + z2->count - z1->base;
        z->flags = z1->flags & z2->flags;

        z->free_count = z1->free_count + z2->free_count;
        z->busy_count = z1->busy_count + z2->busy_count;
        
        max_order = fnzb(z->count);

        z->buddy_system = (buddy_system_t *) &z[1];
        buddy_system_create(z->buddy_system, max_order,
            &zone_buddy_system_operations, (void *) z);

        z->frames = (frame_t *)((uint8_t *) z->buddy_system +
            buddy_conf_size(max_order));
        for (i = 0; i < z->count; i++) {
                /* This marks all frames busy */
                frame_initialize(&z->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, clear
         * 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 < z1->count; i++)
                z->frames[i] = z1->frames[i];
        for (i = 0; i < z2->count; i++) {
                z2idx = i + (z2->base - z1->base);
                z->frames[z2idx] = z2->frames[i];
        }
        i = 0;
        while (i < z->count) {
                if (z->frames[i].refcount) {
                        /* skip busy frames */
                        i += 1 << z->frames[i].buddy_order;
                } else { /* Free frames, set refcount=1 */
                        /* All free frames have refcount=0, we need not
                         * to check the order */
                        z->frames[i].refcount = 1;
                        z->frames[i].buddy_order = 0;
                        i++;
                }
        }
        /* Add free blocks from the 2 original zones */
        while (zone_can_alloc(z1, 0)) {
                frame_idx = zone_frame_alloc(z1, 0);
                frame = &z->frames[frame_idx];
                frame->refcount = 0;
                buddy_system_free(z->buddy_system, &frame->buddy_link);
        }
        while (zone_can_alloc(z2, 0)) {
                frame_idx = zone_frame_alloc(z2, 0);
                frame = &z->frames[frame_idx + (z2->base - z1->base)];
                frame->refcount = 0;
                buddy_system_free(z->buddy_system, &frame->buddy_link);
        }
}

/** Return old configuration frames into the zone.
 *
 * We have several cases
 * - the conf. data is outside of zone -> exit, shall we call frame_free??
 * - the conf. data was created by zone_create or 
 *   updated with reduce_region -> free every frame
 *
 * @param newzone       The actual zone where freeing should occur.
 * @param oldzone       Pointer to old zone configuration data that should
 *                      be freed from new zone.
 */
static void return_config_frames(zone_t *newzone, zone_t *oldzone)
{
        pfn_t pfn;
        frame_t *frame;
        count_t cframes;
        unsigned int i;

        pfn = ADDR2PFN((uintptr_t)KA2PA(oldzone));
        cframes = SIZE2FRAMES(zone_conf_size(oldzone->count));
        
        if (pfn < newzone->base || pfn >= newzone->base + newzone->count)
                return;

        frame = &newzone->frames[pfn - newzone->base];
        ASSERT(!frame->buddy_order);

        for (i = 0; i < cframes; i++) {
                newzone->busy_count++;
                zone_frame_free(newzone, pfn+i-newzone->base);
        }
}

/** Reduce allocated block to count of order 0 frames.
 *
 * The allocated block need 2^order frames of space. Reduce all frames
 * in 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 zone 
 * @param frame_idx             Index to block.
 * @param count                 Allocated space in block.
 */
static void zone_reduce_region(zone_t *zone, pfn_t frame_idx, count_t count)
{
        count_t i;
        uint8_t order;
        frame_t *frame;
        
        ASSERT(frame_idx + count < zone->count);

        order = zone->frames[frame_idx].buddy_order;
        ASSERT((count_t) (1 << order) >= count);

        /* Reduce all blocks to order 0 */
        for (i = 0; i < (count_t) (1 << order); i++) {
                frame = &zone->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 < (count_t) (1 << order); i++) {
                zone_frame_free(zone, i + frame_idx);
        }
}

/** Merge zones z1 and z2.
 *
 * - the zones must be 2 zones with no zone existing in between,
 *   which means that z2 = z1+1
 *
 * - 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 :-/
 */
void zone_merge(unsigned int z1, unsigned int z2)
{
        ipl_t ipl;
        zone_t *zone1, *zone2, *newzone;
        unsigned int cframes;
        uint8_t order;
        unsigned int i;
        pfn_t pfn;

        ipl = interrupts_disable();
        spinlock_lock(&zones.lock);

        if ((z1 >= zones.count) || (z2 >= zones.count))
                goto errout;
        /* We can join only 2 zones with none existing inbetween */
        if (z2 - z1 != 1)
                goto errout;

        zone1 = zones.info[z1];
        zone2 = zones.info[z2];
        spinlock_lock(&zone1->lock);
        spinlock_lock(&zone2->lock);

        cframes = SIZE2FRAMES(zone_conf_size(zone2->base + zone2->count -
            zone1->base));
        if (cframes == 1)
                order = 0;
        else 
                order = fnzb(cframes - 1) + 1;

        /* Allocate zonedata inside one of the zones */
        if (zone_can_alloc(zone1, order))
                pfn = zone1->base + zone_frame_alloc(zone1, order);
        else if (zone_can_alloc(zone2, order))
                pfn = zone2->base + zone_frame_alloc(zone2, order);
        else
                goto errout2;

        newzone = (zone_t *) PA2KA(PFN2ADDR(pfn));

        _zone_merge(newzone, zone1, zone2);

        /* Free unneeded config frames */
        zone_reduce_region(newzone, pfn - newzone->base,  cframes);
        /* Subtract zone information from busy frames */
        newzone->busy_count -= cframes;

        /* Replace existing zones in zoneinfo list */
        zones.info[z1] = newzone;
        for (i = z2 + 1; i < zones.count; i++)
                zones.info[i - 1] = zones.info[i];
        zones.count--;

        /* Free old zone information */
        return_config_frames(newzone, zone1);
        return_config_frames(newzone, zone2);
errout2:
        /* Nobody is allowed to enter to zone, so we are safe
         * to touch the spinlocks last time */
        spinlock_unlock(&zone1->lock);
        spinlock_unlock(&zone2->lock);
errout:
        spinlock_unlock(&zones.lock);
        interrupts_restore(ipl);
}

/** Merge all zones into one big zone.
 *
 * It is reasonable to do this on systems whose bios reports parts in chunks,
 * so that we could have 1 zone (it's faster).
 */
void zone_merge_all(void)
{
        int count = zones.count;

        while (zones.count > 1 && --count) {
                zone_merge(0, 1);
                break;
        }
}

/** Create new frame zone.
 *
 * @param start         Physical address of the first frame within the zone.
 * @param count         Count of frames in zone.
 * @param z             Address of configuration information of zone.
 * @param flags         Zone flags.
 *
 * @return              Initialized zone.
 */
static void zone_construct(pfn_t start, count_t count, zone_t *z, int flags)
{
        unsigned int i;
        uint8_t max_order;

        spinlock_initialize(&z->lock, "zone_lock");
        z->base = start;
        z->count = count;

        /* Mask off flags that are calculated automatically. */
        flags &= ~FRAME_LOW_4_GiB;
        /* Determine calculated flags. */
        if (z->base + count < (1ULL << (32 - FRAME_WIDTH)))     /* 4 GiB */
                flags |= FRAME_LOW_4_GiB;

        z->flags = flags;

        z->free_count = count;
        z->busy_count = 0;

        /*
         * Compute order for buddy system, initialize
         */
        max_order = fnzb(count);
        z->buddy_system = (buddy_system_t *)&z[1];
        
        buddy_system_create(z->buddy_system, max_order, 
            &zone_buddy_system_operations, (void *) z);
        
        /* Allocate frames _after_ the conframe */
        /* Check sizes */
        z->frames = (frame_t *)((uint8_t *) z->buddy_system +
            buddy_conf_size(max_order));
        for (i = 0; i < count; i++) {
                frame_initialize(&z->frames[i]);
        }
        
        /* Stuffing frames */
        for (i = 0; i < count; i++) {
                z->frames[i].refcount = 0;
                buddy_system_free(z->buddy_system, &z->frames[i].buddy_link);
        }
}

/** Compute configuration data size for zone.
 *
 * @param count         Size of zone in frames.
 * @return              Size of zone configuration info (in bytes).
 */
uintptr_t zone_conf_size(count_t count)
{
        int size = sizeof(zone_t) + count * sizeof(frame_t);
        int max_order;

        max_order = fnzb(count);
        size += buddy_conf_size(max_order);
        return size;
}

/** 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.
 */
int zone_create(pfn_t start, count_t count, pfn_t confframe, int flags)
{
        zone_t *z;
        uintptr_t addr;
        count_t confcount;
        unsigned int i;
        int znum;

        /* Theoretically we could have here 0, practically make sure
         * nobody tries to do that. If some platform requires, remove
         * the assert
         */
        ASSERT(confframe);
        /* If conframe is supposed to be inside our zone, then make sure
         * it does not span kernel & init
         */
        confcount = SIZE2FRAMES(zone_conf_size(count));
        if (confframe >= start && confframe < start + count) {
                for (; confframe < start + count; confframe++) {
                        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;
                        count_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.");
        }

        z = (zone_t *) PA2KA(PFN2ADDR(confframe));
        zone_construct(start, count, z, flags);
        znum = zones_add_zone(z);
        if (znum == -1)
                return -1;

        mutex_lock(&mem_avail_mtx);
        mem_avail_frames += count;
        mutex_unlock(&mem_avail_mtx);

        /* If confdata in zone, mark as unavailable */
        if (confframe >= start && confframe < start + count)
                for (i = confframe; i < confframe + confcount; i++) {
                        zone_mark_unavailable(z, i - z->base);
                }
        
        return znum;
}

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

/** Set parent of frame. */
void frame_set_parent(pfn_t pfn, void *data, unsigned int hint)
{
        zone_t *zone = find_zone_and_lock(pfn, &hint);

        ASSERT(zone);

        zone_get_frame(zone, pfn - zone->base)->parent = data;
        spinlock_unlock(&zone->lock);
}

void *frame_get_parent(pfn_t pfn, unsigned int hint)
{
        zone_t *zone = find_zone_and_lock(pfn, &hint);
        void *res;

        ASSERT(zone);
        res = zone_get_frame(zone, pfn - zone->base)->parent;
        
        spinlock_unlock(&zone->lock);
        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, int flags, unsigned int *pzone)
{
        ipl_t ipl;
        int freed;
        pfn_t v;
        zone_t *zone;
        unsigned long gen = 0;
        
loop:
        ipl = interrupts_disable();
        
        /*
         * First, find suitable frame zone.
         */
        zone = find_free_zone_and_lock(order, flags, pzone);
        
        /* If no memory, reclaim some slab memory,
           if it does not help, reclaim all */
        if (!zone && !(flags & FRAME_NO_RECLAIM)) {
                freed = slab_reclaim(0);
                if (freed)
                        zone = find_free_zone_and_lock(order, flags, pzone);
                if (!zone) {
                        freed = slab_reclaim(SLAB_RECLAIM_ALL);
                        if (freed)
                                zone = find_free_zone_and_lock(order, flags,
                                    pzone);
                }
        }
        if (!zone) {
                /*
                 * Sleep until some frames are available again.
                 */
                if (flags & FRAME_ATOMIC) {
                        interrupts_restore(ipl);
                        return 0;
                }
                
#ifdef CONFIG_DEBUG
                unsigned long avail;

                mutex_lock(&mem_avail_mtx);
                avail = mem_avail_frames;
                mutex_unlock(&mem_avail_mtx);

                printf("Thread %" PRIu64 " waiting for %u frames, "
                    "%u available.\n", THREAD->tid, 1ULL << order, avail);
#endif

                mutex_lock(&mem_avail_mtx);
                while ((mem_avail_frames < (1ULL << order)) ||
                    gen == mem_avail_gen)
                        condvar_wait(&mem_avail_cv, &mem_avail_mtx);
                gen = mem_avail_gen;
                mutex_unlock(&mem_avail_mtx);

#ifdef CONFIG_DEBUG
                mutex_lock(&mem_avail_mtx);
                avail = mem_avail_frames;
                mutex_unlock(&mem_avail_mtx);

                printf("Thread %" PRIu64 " woken up, %u frames available.\n",
                    THREAD->tid, avail);
#endif

                interrupts_restore(ipl);
                goto loop;
        }
        
        v = zone_frame_alloc(zone, order);
        v += zone->base;

        spinlock_unlock(&zone->lock);
        
        mutex_lock(&mem_avail_mtx);
        mem_avail_frames -= (1ULL << order);
        mutex_unlock(&mem_avail_mtx);

        interrupts_restore(ipl);

        if (flags & FRAME_KA)
                return (void *)PA2KA(PFN2ADDR(v));
        return (void *)PFN2ADDR(v);
}

/** 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.
 */
void frame_free(uintptr_t frame)
{
        ipl_t ipl;
        zone_t *zone;
        pfn_t pfn = ADDR2PFN(frame);

        ipl = interrupts_disable();

        /*
         * First, find host frame zone for addr.
         */
        zone = find_zone_and_lock(pfn, NULL);
        ASSERT(zone);
        
        zone_frame_free(zone, pfn - zone->base);
        
        spinlock_unlock(&zone->lock);
        
        /*
         * Signal that some memory has been freed.
         */
        mutex_lock(&mem_avail_mtx);
        mem_avail_frames++;
        mem_avail_gen++;
        condvar_broadcast(&mem_avail_cv);
        mutex_unlock(&mem_avail_mtx);

        interrupts_restore(ipl);
}

/** 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.
 */
void frame_reference_add(pfn_t pfn)
{
        ipl_t ipl;
        zone_t *zone;
        frame_t *frame;

        ipl = interrupts_disable();
        
        /*
         * First, find host frame zone for addr.
         */
        zone = find_zone_and_lock(pfn, NULL);
        ASSERT(zone);
        
        frame = &zone->frames[pfn - zone->base];
        frame->refcount++;
        
        spinlock_unlock(&zone->lock);
        interrupts_restore(ipl);
}

/** Mark given range unavailable in frame zones. */
void frame_mark_unavailable(pfn_t start, count_t count)
{
        unsigned int i;
        zone_t *zone;
        unsigned int prefzone = 0;
        
        for (i = 0; i < count; i++) {
                zone = find_zone_and_lock(start + i, &prefzone);
                if (!zone) /* PFN not found */
                        continue;
                zone_mark_unavailable(zone, start + i - zone->base);

                spinlock_unlock(&zone->lock);
        }
}

/** Initialize physical memory management. */
void frame_init(void)
{
        if (config.cpu_active == 1) {
                zones.count = 0;
                spinlock_initialize(&zones.lock, "zones.lock");
                mutex_initialize(&mem_avail_mtx, MUTEX_ACTIVE);
                condvar_initialize(&mem_avail_cv);
        }
        /* Tell the architecture to create some memory */
        frame_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));
                
                count_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);
        }
}


/** Return total size of all zones. */
uint64_t zone_total_size(void)
{
        zone_t *zone = NULL;
        unsigned int i;
        ipl_t ipl;
        uint64_t total = 0;

        ipl = interrupts_disable();
        spinlock_lock(&zones.lock);
        
        for (i = 0; i < zones.count; i++) {
                zone = zones.info[i];
                spinlock_lock(&zone->lock);
                total += (uint64_t) FRAMES2SIZE(zone->count);
                spinlock_unlock(&zone->lock);
        }
        
        spinlock_unlock(&zones.lock);
        interrupts_restore(ipl);
        
        return total;
}

/** Prints list of zones. */
void zone_print_list(void)
{
        zone_t *zone = NULL;
        unsigned int i;
        ipl_t ipl;

#ifdef __32_BITS__      
        printf("#  base address free frames  busy frames\n");
        printf("-- ------------ ------------ ------------\n");
#endif

#ifdef __64_BITS__
        printf("#  base address         free frames  busy frames\n");
        printf("-- -------------------- ------------ ------------\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).
         */

        for (i = 0; ; i++) {
                uintptr_t base;
                count_t free_count;
                count_t busy_count;

                ipl = interrupts_disable();
                spinlock_lock(&zones.lock);
                
                if (i >= zones.count) {
                        spinlock_unlock(&zones.lock);
                        interrupts_restore(ipl);
                        break;
                }

                zone = zones.info[i];
                spinlock_lock(&zone->lock);

                base = PFN2ADDR(zone->base);
                free_count = zone->free_count;
                busy_count = zone->busy_count;

                spinlock_unlock(&zone->lock);
                
                spinlock_unlock(&zones.lock);
                interrupts_restore(ipl);

#ifdef __32_BITS__
                printf("%-2u   %10p %12" PRIc " %12" PRIc "\n", i, base,
                    free_count, busy_count);
#endif

#ifdef __64_BITS__
                printf("%-2u   %18p %12" PRIc " %12" PRIc "\n", i, base,
                    free_count, busy_count);
#endif
                
        }
}

/** Prints zone details.
 *
 * @param num           Zone base address or zone number.
 */
void zone_print_one(unsigned int num)
{
        zone_t *zone = NULL;
        ipl_t ipl;
        unsigned int i;
        uintptr_t base;
        count_t count;
        count_t busy_count;
        count_t free_count;

        ipl = interrupts_disable();
        spinlock_lock(&zones.lock);

        for (i = 0; i < zones.count; i++) {
                if ((i == num) || (PFN2ADDR(zones.info[i]->base) == num)) {
                        zone = zones.info[i];
                        break;
                }
        }
        if (!zone) {
                spinlock_unlock(&zones.lock);
                interrupts_restore(ipl);
                printf("Zone not found.\n");
                return;
        }
        
        spinlock_lock(&zone->lock);
        base = PFN2ADDR(zone->base);
        count = zone->count;
        busy_count = zone->busy_count;
        free_count = zone->free_count;
        spinlock_unlock(&zone->lock);
        spinlock_unlock(&zones.lock);
        interrupts_restore(ipl);

        printf("Zone base address: %p\n", base);
        printf("Zone size: %" PRIc " frames (%" PRIs " KiB)\n", count,
            SIZE2KB(FRAMES2SIZE(count)));
        printf("Allocated space: %" PRIc " frames (%" PRIs " KiB)\n",
            busy_count, SIZE2KB(FRAMES2SIZE(busy_count)));
        printf("Available space: %" PRIc " frames (%" PRIs " KiB)\n",
            free_count, SIZE2KB(FRAMES2SIZE(free_count)));
}

/** @}
 */