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/*
* libc/stdlib/malloc/malloc.c -- malloc function
*
* Copyright (C) 2002 NEC Corporation
* Copyright (C) 2002 Miles Bader <miles@gnu.org>
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License. See the file COPYING.LIB in the main
* directory of this archive for more details.
*
* Written by Miles Bader <miles@gnu.org>
*/
#include <stdlib.h>
#include <unistd.h>
#include <sys/mman.h>
#include "malloc.h"
#include "heap.h"
/* The malloc heap. */
struct heap __malloc_heap = HEAP_INIT;
#ifdef MALLOC_USE_LOCKING
/* A lock protecting the malloc heap. */
malloc_mutex_t __malloc_lock;
# ifdef MALLOC_USE_SBRK
/* A lock protecting our use of sbrk. */
malloc_mutex_t __malloc_sbrk_lock;
# endif /* MALLOC_USE_SBRK */
#endif /* MALLOC_USE_LOCKING */
void *
malloc (size_t size)
{
void *mem;
struct heap *heap = &__malloc_heap;
MALLOC_DEBUG ("malloc: %d bytes\n", size);
/* Include extra space to record the size of the allocated block. */
size += MALLOC_HEADER_SIZE;
__malloc_lock ();
/* First try to get memory that's already in our heap. */
mem = __heap_alloc (heap, &size);
if (unlikely (! mem))
/* We couldn't allocate from the heap, so grab some more
from the system, add it to the heap, and try again. */
{
/* If we're trying to allocate a block bigger than the default
MALLOC_HEAP_EXTEND_SIZE, make sure we get enough to hold it. */
void *block;
size_t block_size
= (size < MALLOC_HEAP_EXTEND_SIZE
? MALLOC_HEAP_EXTEND_SIZE
: MALLOC_ROUND_UP_TO_PAGE_SIZE (size));
#ifdef MALLOC_USE_SBRK
/* Get the sbrk lock while we've still got the main lock. */
__malloc_lock_sbrk ();
#endif
/* Don't hold the main lock during the syscall, so that small
allocations in a different thread may succeed while we're
blocked. */
__malloc_unlock ();
/* Allocate the new heap block. */
#ifdef MALLOC_USE_SBRK
/* Use sbrk we can, as it's faster than mmap, and guarantees
contiguous allocation. */
block = sbrk (block_size);
if (likely (block != (void *)-1))
{
/* Because sbrk can return results of arbitrary
alignment, align the result to a MALLOC_ALIGNMENT boundary. */
long aligned_block = MALLOC_ROUND_UP ((long)block, MALLOC_ALIGNMENT);
if (block != (void *)aligned_block)
/* Have to adjust. We should only have to actually do this
the first time (after which we will have aligned the brk
correctly). */
{
/* Move the brk to reflect the alignment; our next allocation
should start on exactly the right alignment. */
sbrk (aligned_block - (long)block);
block = (void *)aligned_block;
}
}
__malloc_unlock_sbrk ();
#else /* !MALLOC_USE_SBRK */
/* Otherwise, use mmap. */
block = mmap (0, block_size, PROT_READ | PROT_WRITE,
MAP_SHARED | MAP_ANONYMOUS, 0, 0);
#endif /* MALLOC_USE_SBRK */
/* Get back the main lock. */
__malloc_lock ();
if (likely (block != (void *)-1))
{
MALLOC_DEBUG (" adding memory: 0x%lx - 0x%lx (%d bytes)\n",
(long)block, (long)block + block_size, block_size);
/* Put BLOCK into the heap. */
__heap_free (heap, block, block_size);
/* Try again to allocate. */
mem = __heap_alloc (heap, &size);
}
}
__malloc_unlock ();
if (likely (mem))
/* Record the size of the block and get the user address. */
{
mem = MALLOC_SETUP (mem, size);
MALLOC_DEBUG (" malloc: returning 0x%lx (base:0x%lx, total_size:%d)\n",
(long)mem, (long)MALLOC_BASE(mem), (long)MALLOC_SIZE(mem));
}
return mem;
}
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