/****************************************************************************
* mm/mm_heap/mm_memalign.c
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <assert.h>
#include <nuttx/mm/mm.h>
#include "mm_heap/mm.h"
#include "kasan/kasan.h"
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: mm_memalign
*
* Description:
* memalign requests more than enough space from malloc, finds a region
* within that chunk that meets the alignment request and then frees any
* leading or trailing space.
*
* The alignment argument must be a power of two. 8-byte alignment is
* guaranteed by normal malloc calls.
*
****************************************************************************/
FAR void *mm_memalign(FAR struct mm_heap_s *heap, size_t alignment,
size_t size)
{
FAR struct mm_allocnode_s *node;
size_t rawchunk;
size_t alignedchunk;
size_t mask = (size_t)(alignment - 1);
size_t allocsize;
size_t newsize;
/* Make sure that alignment is less than half max size_t */
if (alignment >= (SIZE_MAX / 2))
{
return NULL;
}
/* Make sure that alignment is a power of 2 */
if ((alignment & -alignment) != alignment)
{
return NULL;
}
/* If this requested alinement's less than or equal to the natural
* alignment of malloc, then just let malloc do the work.
*/
if (alignment <= MM_MIN_CHUNK)
{
return mm_malloc(heap, size);
}
/* Adjust the size to account for (1) the size of the allocated node, (2)
* to make sure that it is an even multiple of our granule size, and to
* include the alignment amount.
*
* Notice that we increase the allocation size by twice the requested
* alignment. We do this so that there will be at least two valid
* alignment points within the allocated memory.
*
* NOTE: These are sizes given to malloc and not chunk sizes. They do
* not include SIZEOF_MM_ALLOCNODE.
*/
newsize = MM_ALIGN_UP(size); /* Make multiples of our granule size */
allocsize = newsize + 2 * alignment; /* Add double full alignment size */
if ((newsize < size) || (allocsize < newsize))
{
/* Integer overflow */
return NULL;
}
/* Then malloc that size */
rawchunk = (size_t)mm_malloc(heap, allocsize);
if (rawchunk == 0)
{
return NULL;
}
kasan_poison((FAR void *)rawchunk, mm_malloc_size((FAR void *)rawchunk));
/* We need to hold the MM semaphore while we muck with the chunks and
* nodelist.
*/
DEBUGVERIFY(mm_takesemaphore(heap));
/* Get the node associated with the allocation and the next node after
* the allocation.
*/
node = (FAR struct mm_allocnode_s *)(rawchunk - SIZEOF_MM_ALLOCNODE);
/* Find the aligned subregion */
alignedchunk = (rawchunk + mask) & ~mask;
/* Check if there is free space at the beginning of the aligned chunk */
if (alignedchunk != rawchunk)
{
FAR struct mm_allocnode_s *newnode;
FAR struct mm_allocnode_s *next;
size_t precedingsize;
/* Get the node the next node after the allocation. */
next = (FAR struct mm_allocnode_s *)((FAR char *)node + node->size);
/* Make sure that there is space to convert the preceding
* mm_allocnode_s into an mm_freenode_s. I think that this should
* always be true
*/
DEBUGASSERT(alignedchunk >= rawchunk + 8);
newnode = (FAR struct mm_allocnode_s *)
(alignedchunk - SIZEOF_MM_ALLOCNODE);
/* Preceding size is full size of the new 'node,' including
* SIZEOF_MM_ALLOCNODE
*/
precedingsize = (size_t)newnode - (size_t)node;
/* If we were unlucky, then the alignedchunk can lie in such a position
* that precedingsize < SIZEOF_NODE_FREENODE. We can't let that happen
* because we are going to cast 'node' to struct mm_freenode_s below.
* This is why we allocated memory large enough to support two
* alignment points. In this case, we will simply use the second
* alignment point.
*/
if (precedingsize < SIZEOF_MM_FREENODE)
{
alignedchunk += alignment;
newnode = (FAR struct mm_allocnode_s *)
(alignedchunk - SIZEOF_MM_ALLOCNODE);
precedingsize = (size_t)newnode - (size_t)node;
}
/* Set up the size of the new node */
newnode->size = (size_t)next - (size_t)newnode;
newnode->preceding = precedingsize | MM_ALLOC_BIT;
MM_ADD_BACKTRACE(heap, newnode);
/* Reduce the size of the original chunk and mark it not allocated, */
node->size = precedingsize;
node->preceding &= ~MM_ALLOC_BIT;
/* Fix the preceding size of the next node */
next->preceding = newnode->size | (next->preceding & MM_ALLOC_BIT);
/* Convert the newnode chunk size back into malloc-compatible size by
* subtracting the header size SIZEOF_MM_ALLOCNODE.
*/
allocsize = newnode->size - SIZEOF_MM_ALLOCNODE;
/* Add the original, newly freed node to the free nodelist */
mm_addfreechunk(heap, (FAR struct mm_freenode_s *)node);
/* Replace the original node with the newlay realloaced,
* aligned node
*/
node = newnode;
}
/* Check if there is free space at the end of the aligned chunk. Convert
* malloc-compatible chunk size to include SIZEOF_MM_ALLOCNODE as needed
* for mm_shrinkchunk.
*/
size = MM_ALIGN_UP(size + SIZEOF_MM_ALLOCNODE);
if (allocsize > size)
{
/* Shrink the chunk by that much -- remember, mm_shrinkchunk wants
* internal chunk sizes that include SIZEOF_MM_ALLOCNODE.
*/
mm_shrinkchunk(heap, node, size);
}
mm_givesemaphore(heap);
kasan_unpoison((FAR void *)alignedchunk,
mm_malloc_size((FAR void *)alignedchunk));
return (FAR void *)alignedchunk;
}