source: mainline/uspace/libc/generic/as.c@ 36f19c0

/*
 * Copyright (c) 2006 Jakub Jermar
 * 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 <as.h>
#include <libc.h>
#include <unistd.h>
#include <align.h>
#include <types.h>
#include <bitops.h>

/**
 * Either 4*256M on 32-bit architecures or 16*256M on 64-bit architectures.
 */
#define MAX_HEAP_SIZE   (sizeof(uintptr_t)<<28)

/** Create address space area.
 *
 * @param address Virtual address where to place new address space area.
 * @param size Size of the area.
 * @param flags Flags describing type of the area.
 *
 * @return address on success, (void *) -1 otherwise.
 */
void *as_area_create(void *address, size_t size, int flags)
{
        return (void *) __SYSCALL3(SYS_AS_AREA_CREATE, (sysarg_t ) address,
            (sysarg_t) size, (sysarg_t) flags);
}

/** Resize address space area.
 *
 * @param address Virtual address pointing into already existing address space
 *      area.
 * @param size New requested size of the area.
 * @param flags Currently unused.
 *
 * @return Zero on success or a code from @ref errno.h on failure.
 */
int as_area_resize(void *address, size_t size, int flags)
{
        return __SYSCALL3(SYS_AS_AREA_RESIZE, (sysarg_t ) address,
            (sysarg_t) size, (sysarg_t) flags);
}

/** Destroy address space area.
 *
 * @param address Virtual address pointing into the address space area being
 *      destroyed.
 *
 * @return Zero on success or a code from @ref errno.h on failure.
 */
int as_area_destroy(void *address)
{
        return __SYSCALL1(SYS_AS_AREA_DESTROY, (sysarg_t ) address);
}

static size_t heapsize = 0;
static size_t maxheapsize = (size_t) (-1);

static void * last_allocated = 0;

/* Start of heap linker symbol */
extern char _heap;

/** Sbrk emulation 
 *
 * @param incr New area that should be allocated or negative, 
               if it should be shrinked
 * @return Pointer to newly allocated area
 */
void *sbrk(ssize_t incr)
{
        int rc;
        void *res;
        
        /* Check for invalid values */
        if (incr < 0 && -incr > heapsize)
                return NULL;
        
        /* Check for too large value */
        if (incr > 0 && incr+heapsize < heapsize)
                return NULL;
        
        /* Check for too small values */
        if (incr < 0 && incr+heapsize > heapsize)
                return NULL;
        
        /* Check for user limit */
        if ((maxheapsize != (size_t) (-1)) && (heapsize + incr) > maxheapsize)
                return NULL;
        
        rc = as_area_resize(&_heap, heapsize + incr, 0);
        if (rc != 0)
                return NULL;
        
        /* Compute start of new area */
        res = (void *) &_heap + heapsize;

        heapsize += incr;

        return res;
}

/** Set maximum heap size and return pointer just after the heap */
void *set_maxheapsize(size_t mhs)
{
        maxheapsize = mhs;
        /* Return pointer to area not managed by sbrk */
        return ((void *) &_heap + maxheapsize);
}

/** Return pointer to some unmapped area, where fits new as_area
 *
 * @param sz Requested size of the allocation.
 *
 * @return Pointer to the beginning 
 *
 * TODO: make some first_fit/... algorithm, we are now just incrementing
 *       the pointer to last area
 */
void *as_get_mappable_page(size_t sz)
{
        void *res;
        uint64_t asz;
        int i;
        
        if (!sz)
                return NULL;    

        asz = 1 << (fnzb64(sz - 1) + 1);

        /* Set heapsize to some meaningful value */
        if (maxheapsize == -1)
                set_maxheapsize(MAX_HEAP_SIZE);
        
        /*
         * Make sure we allocate from naturally aligned address.
         */
        i = 0;
        if (!last_allocated) {
                last_allocated = (void *) ALIGN_UP((void *) &_heap +
                    maxheapsize, asz);
        } else {
                last_allocated = (void *) ALIGN_UP(((uintptr_t)
                    last_allocated) + (int) (i > 0), asz);
        }

        res = last_allocated;
        last_allocated += ALIGN_UP(sz, PAGE_SIZE);

        return res;
}

/** @}
 */