Subversion Repositories HelenOS

/*

 * Copyright (c) 2009 Martin Decky

 * Copyright (c) 2009 Petr Tuma

 * 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 libc

 * @{

 */

/** @file

 */

#include <malloc.h>

#include <bool.h>

#include <as.h>

#include <align.h>

#include <macros.h>

#include <assert.h>

#include <errno.h>

#include <bitops.h>

#include <mem.h>

#include <adt/gcdlcm.h>

/* Magic used in heap headers. */

#define HEAP_BLOCK_HEAD_MAGIC  0xBEEF0101

/* Magic used in heap footers. */

#define HEAP_BLOCK_FOOT_MAGIC  0xBEEF0202

/** Allocation alignment (this also covers the alignment of fields

    in the heap header and footer) */

#define BASE_ALIGN  16

/**

 * Either 4 * 256M on 32-bit architecures or 16 * 256M on 64-bit architectures

 */

#define MAX_HEAP_SIZE  (sizeof(uintptr_t) << 28)

/**

 *

 */

#define STRUCT_OVERHEAD  (sizeof(heap_block_head_t) + sizeof(heap_block_foot_t))

/**

 * Calculate real size of a heap block (with header and footer)

 */

#define GROSS_SIZE(size)  ((size) + STRUCT_OVERHEAD)

/**

 * Calculate net size of a heap block (without header and footer)

 */

#define NET_SIZE(size)  ((size) - STRUCT_OVERHEAD)

/** Header of a heap block

 *

 */

typedef struct {

    /* Size of the block (including header and footer) */

    size_t size;

    /* Indication of a free block */

    bool free;

    /* A magic value to detect overwrite of heap header */

    uint32_t magic;

} heap_block_head_t;

/** Footer of a heap block

 *

 */

typedef struct {

    /* Size of the block (including header and footer) */

    size_t size;

    /* A magic value to detect overwrite of heap footer */

    uint32_t magic;

} heap_block_foot_t;

/** Linker heap symbol */

extern char _heap;

/** Address of heap start */

static void *heap_start = 0;

/** Address of heap end */

static void *heap_end = 0;

/** Maximum heap size */

static size_t max_heap_size = (size_t) -1;

/** Current number of pages of heap area */

static size_t heap_pages = 0;

/** Initialize a heap block

 *

 * Fills in the structures related to a heap block.

 *

 * @param addr Address of the block.

 * @param size Size of the block including the header and the footer.

 * @param free Indication of a free block.

 *

 */

static void block_init(void *addr, size_t size, bool free)

{

    /* Calculate the position of the header and the footer */

    heap_block_head_t *head = (heap_block_head_t *) addr;

    heap_block_foot_t *foot =

        (heap_block_foot_t *) (addr + size - sizeof(heap_block_foot_t));

    head->size = size;

    head->free = free;

    head->magic = HEAP_BLOCK_HEAD_MAGIC;

    foot->size = size;

    foot->magic = HEAP_BLOCK_FOOT_MAGIC;

}

/** Check a heap block

 *

 * Verifies that the structures related to a heap block still contain

 * the magic constants. This helps detect heap corruption early on.

 *

 * @param addr Address of the block.

 *

 */

static void block_check(void *addr)

{

    heap_block_head_t *head = (heap_block_head_t *) addr;

    assert(head->magic == HEAP_BLOCK_HEAD_MAGIC);

    heap_block_foot_t *foot =

        (heap_block_foot_t *) (addr + head->size - sizeof(heap_block_foot_t));

    assert(foot->magic == HEAP_BLOCK_FOOT_MAGIC);

    assert(head->size == foot->size);

}

static bool grow_heap(size_t size)

{

    if (size == 0)

        return false;

    size_t heap_size = (size_t) (heap_end - heap_start);

    if ((max_heap_size != (size_t) -1) && (heap_size + size > max_heap_size))

        return false;

    size_t pages = (size - 1) / PAGE_SIZE + 1;

    if (as_area_resize((void *) &_heap, (heap_pages + pages) * PAGE_SIZE, 0)

        == EOK) {

        void *end = (void *) ALIGN_DOWN(((uintptr_t) &_heap) +

            (heap_pages + pages) * PAGE_SIZE, BASE_ALIGN);

        block_init(heap_end, end - heap_end, true);

        heap_pages += pages;

        heap_end = end;

        return true;

    }

    return false;

}

static void shrink_heap(void)

{

    // TODO

}

/** Initialize the heap allocator

 *

 * Finds how much physical memory we have and creates

 * the heap management structures that mark the whole

 * physical memory as a single free block.

 *

 */

void __heap_init(void)

{

    if (as_area_create((void *) &_heap, PAGE_SIZE,

        AS_AREA_WRITE | AS_AREA_READ)) {

        heap_pages = 1;

        heap_start = (void *) ALIGN_UP((uintptr_t) &_heap, BASE_ALIGN);

        heap_end =

            (void *) ALIGN_DOWN(((uintptr_t) &_heap) + PAGE_SIZE, BASE_ALIGN);

        /* Make the entire area one large block. */

        block_init(heap_start, heap_end - heap_start, true);

    }

}

uintptr_t get_max_heap_addr(void)

{

    if (max_heap_size == (size_t) -1)

        max_heap_size =

            max((size_t) (heap_end - heap_start), MAX_HEAP_SIZE);

    return ((uintptr_t) heap_start + max_heap_size);

}

static void split_mark(heap_block_head_t *cur, const size_t size)

{

    assert(cur->size >= size);

    /* See if we should split the block. */

    size_t split_limit = GROSS_SIZE(size);

    if (cur->size > split_limit) {

        /* Block big enough -> split. */

        void *next = ((void *) cur) + size;

        block_init(next, cur->size - size, true);

        block_init(cur, size, false);

    } else {

        /* Block too small -> use as is. */

        cur->free = false;

    }

}

/** Allocate a memory block

 *

 * @param size  The size of the block to allocate.

 * @param align Memory address alignment.

 *

 * @return the address of the block or NULL when not enough memory.

 *

 */

static void *malloc_internal(const size_t size, const size_t align)

{

    if (align == 0)

        return NULL;

    size_t falign = lcm(align, BASE_ALIGN);

    size_t real_size = GROSS_SIZE(ALIGN_UP(size, falign));

    bool grown = false;

    void *result;

loop:

    result = NULL;

    heap_block_head_t *cur = (heap_block_head_t *) heap_start;

    while ((result == NULL) && ((void *) cur < heap_end)) {

        block_check(cur);

        /* Try to find a block that is free and large enough. */

        if ((cur->free) && (cur->size >= real_size)) {

            /* We have found a suitable block.

               Check for alignment properties. */

            void *addr = ((void *) cur) + sizeof(heap_block_head_t);

            void *aligned = (void *) ALIGN_UP(addr, falign);

            if (addr == aligned) {

                /* Exact block start including alignment. */

                split_mark(cur, real_size);

                result = addr;

            } else {

                /* Block start has to be aligned, thus

                   the previous block needs to be enlarged */

                size_t excess = (size_t) (aligned - addr);

                if (cur->size >= real_size + excess) {

                    if ((void *) cur > heap_start) {

                        // TODO: This can be optimized further in case

                        // of expanding a previous allocated block if the

                        // excess is large enought to put another free

                        // block in between

                        heap_block_foot_t *prev_foot =

                            ((void *) cur) - sizeof(heap_block_foot_t);

                        heap_block_head_t *prev_head =

                            (heap_block_head_t *) (((void *) cur) - prev_foot->size);

                        block_check(prev_head);

                        size_t reduced_size = cur->size - excess;

                        cur = ((void *) cur) + excess;

                        block_init(prev_head, prev_head->size + excess, prev_head->free);

                        block_init(cur, reduced_size, true);

                        split_mark(cur, real_size);

                        result = aligned;

                    } else {

                        while (excess < STRUCT_OVERHEAD) {

                            aligned += falign;

                            excess += falign;

                        }

                        if (cur->size >= real_size + excess) {

                            size_t reduced_size = cur->size - excess;

                            cur = (heap_block_head_t *) (heap_start + excess);

                            block_init(heap_start, excess, true);

                            block_init(cur, reduced_size, true);

                            split_mark(cur, real_size);

                            result = aligned;

                        }

                    }

                }

            }

        }

        /* Advance to the next block. */

        cur = (heap_block_head_t *) (((void *) cur) + cur->size);

    }

    if ((result == NULL) && (!grown)) {

        if (grow_heap(real_size)) {

            grown = true;

            goto loop;

        }

    }

    return result;

}

void *malloc(const size_t size)

{

    return malloc_internal(size, BASE_ALIGN);

}

void *memalign(const size_t align, const size_t size)

{

    if (align == 0)

        return NULL;

    size_t palign =

        1 << (fnzb(max(sizeof(void *), align) - 1) + 1);

    return malloc_internal(size, palign);

}

void *realloc(const void *addr, const size_t size)

{

    if (addr == NULL)

        return malloc(size);

    /* Calculate the position of the header. */

    heap_block_head_t *head =

        (heap_block_head_t *) (addr - sizeof(heap_block_head_t));

    assert((void *) head >= heap_start);

    assert((void *) head < heap_end);

    block_check(head);

    assert(!head->free);

    void *ptr = NULL;

    size_t real_size = GROSS_SIZE(size);

    size_t orig_size = head->size;

    if (orig_size > real_size) {

        /* Shrink */

        if (orig_size - real_size >= STRUCT_OVERHEAD) {

            /* Split the original block to a full block

               and a tailing free block */

            block_init((void *) head, real_size, false);

            block_init((void *) head + real_size,

                orig_size - real_size, true);

            shrink_heap();

        }

        ptr = ((void *) head) + sizeof(heap_block_head_t);

    } else {

        /* Look at the next block. If it is free and the size is

           sufficient then merge the two. */

        heap_block_head_t *next_head =

            (heap_block_head_t *) (((void *) head) + head->size);

        if (((void *) next_head < heap_end)

            && (head->size + next_head->size >= real_size)) {

            block_check(next_head);

            block_init(head, head->size + next_head->size, false);

            split_mark(head, size);

            ptr = ((void *) head) + sizeof(heap_block_head_t);

        } else {

            ptr = malloc(size);

            if (ptr != NULL) {

                memcpy(ptr, addr, NET_SIZE(orig_size));

                free(addr);

            }

        }

    }

    return ptr;

}

/** Free a memory block

 *

 * @param addr The address of the block.

 */

void free(const void *addr)

{

    /* Calculate the position of the header. */

    heap_block_head_t *head

        = (heap_block_head_t *) (addr - sizeof(heap_block_head_t));

    assert((void *) head >= heap_start);

    assert((void *) head < heap_end);

    block_check(head);

    assert(!head->free);

    /* Mark the block itself as free. */

    head->free = true;

    /* Look at the next block. If it is free, merge the two. */

    heap_block_head_t *next_head

        = (heap_block_head_t *) (((void *) head) + head->size);

    if ((void *) next_head < heap_end) {

        block_check(next_head);

        if (next_head->free)

            block_init(head, head->size + next_head->size, true);

    }

    /* Look at the previous block. If it is free, merge the two. */

    if ((void *) head > heap_start) {

        heap_block_foot_t *prev_foot =

            (heap_block_foot_t *) (((void *) head) - sizeof(heap_block_foot_t));

        heap_block_head_t *prev_head =

            (heap_block_head_t *) (((void *) head) - prev_foot->size);

        block_check(prev_head);

        if (prev_head->free)

            block_init(prev_head, prev_head->size + head->size, true);

    }

    shrink_heap();

}

/** @}

 */