/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright (c) 1991, 2012, Oracle and/or its affiliates. All rights reserved.
*/
/* Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
/* All Rights Reserved */
#include <sys/types.h>
/*
* Simplified version of malloc(), free() and realloc(), to be linked with
* utilities that use [s]brk() and do not define their own version of the
* routines.
*
* The algorithm used to get extra memory space by mmap'ing /dev/zero. This
* breaks if the application closes the open descriptor, so now it uses
* mmap's MAP_ANON feature.
*
* Each call to mmap() creates a page. The pages are linked in a list.
* Each page is divided in blocks. There is at least one block in a page.
* New memory chunks are allocated on a first-fit basis.
* Freed blocks are joined in larger blocks. Free pages are unmapped.
*/
#include <stdlib.h>
#include <sys/types.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include <thread.h>
#include <pthread.h>
#include <synch.h>
#include <string.h>
static mutex_t lock = DEFAULTMUTEX;
struct block {
size_t size; /* Space available for user */
struct page *page; /* Backwards reference to page */
int status;
struct block *next;
void *memstart[1];
};
struct page {
size_t size; /* Total page size (incl. header) */
struct page *next;
struct block block[1];
};
#define FREE 0
#define BUSY 1
#define HDR_BLOCK (sizeof (struct block) - sizeof (void *))
#define HDR_PAGE (sizeof (struct page) - sizeof (void *))
#define MINSZ sizeof (double)
/* for convenience */
#ifndef NULL
#define NULL (0)
#endif
struct page *memstart;
static int pagesize;
static void defrag(struct page *);
static void split(struct block *, size_t);
static void *malloc_unlocked(size_t);
static size_t align(size_t, int);
void *
malloc(size_t size)
{
void *retval;
(void) mutex_lock(&lock);
retval = malloc_unlocked(size);
(void) mutex_unlock(&lock);
return (retval);
}
static void *
malloc_unlocked(size_t size)
{
struct block *block;
struct page *page;
if (pagesize == 0)
pagesize = (int)sysconf(_SC_PAGESIZE);
size = align(size, MINSZ);
/*
* Try to locate necessary space
*/
for (page = memstart; page; page = page->next) {
for (block = page->block; block; block = block->next) {
if (block->status == FREE && block->size >= size)
goto found;
}
}
found:
/*
* Need to allocate a new page
*/
if (!page) {
size_t totsize = size + HDR_PAGE;
size_t totpage = align(totsize, pagesize);
if ((page = (struct page *)mmap(0, totpage,
PROT_READ|PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0))
== MAP_FAILED)
return (0);
page->next = memstart;
memstart = page;
page->size = totpage;
block = page->block;
block->next = 0;
block->status = FREE;
block->size = totpage - HDR_PAGE;
block->page = page;
}
split(block, size);
block->status = BUSY;
return (&block->memstart);
}
void *
realloc(void *ptr, size_t size)
{
struct block *block;
size_t osize;
void *newptr;
if (size == 0) {
free(ptr);
return ((void *)0x00000001);
}
(void) mutex_lock(&lock);
if (ptr <= (void *)0x00000001) {
newptr = malloc_unlocked(size);
(void) mutex_unlock(&lock);
return (newptr);
}
block = (struct block *)((char *)ptr - HDR_BLOCK);
size = align(size, MINSZ);
osize = block->size;
/*
* Join block with next one if it is free
*/
if (block->next && block->next->status == FREE) {
block->size += block->next->size + HDR_BLOCK;
block->next = block->next->next;
}
if (size <= block->size) {
split(block, size);
(void) mutex_unlock(&lock);
return (ptr);
}
newptr = malloc_unlocked(size);
(void) memcpy(newptr, ptr, osize);
block->status = FREE;
defrag(block->page);
(void) mutex_unlock(&lock);
return (newptr);
}
void
free(void *ptr)
{
struct block *block;
(void) mutex_lock(&lock);
if (ptr <= (void *)0x00000001) {
(void) mutex_unlock(&lock);
return;
}
block = (struct block *)((char *)ptr - HDR_BLOCK);
block->status = FREE;
defrag(block->page);
(void) mutex_unlock(&lock);
}
/*
* Align size on an appropriate boundary
*/
static size_t
align(size_t size, int bound)
{
if (size < bound)
return ((size_t)bound);
else
return (size + bound - 1 - (size + bound - 1) % bound);
}
static void
split(struct block *block, size_t size)
{
if (block->size > size + sizeof (struct block)) {
struct block *newblock;
newblock = (struct block *)((char *)block + HDR_BLOCK + size);
newblock->next = block->next;
block->next = newblock;
newblock->status = FREE;
newblock->page = block->page;
newblock->size = block->size - size - HDR_BLOCK;
block->size = size;
}
}
/*
* Defragmentation
*/
static void
defrag(struct page *page)
{
struct block *block;
for (block = page->block; block; block = block->next) {
struct block *block2;
if (block->status == BUSY)
continue;
for (block2 = block->next; block2 && block2->status == FREE;
block2 = block2->next) {
block->next = block2->next;
block->size += block2->size + HDR_BLOCK;
}
}
/*
* Free page
*/
if (page->block->size == page->size - HDR_PAGE) {
if (page == memstart)
memstart = page->next;
else {
struct page *page2;
for (page2 = memstart; page2->next;
page2 = page2->next) {
if (page2->next == page) {
page2->next = page->next;
break;
}
}
}
(void) munmap((caddr_t)page, page->size);
}
}
static void
malloc_prepare()
{
(void) mutex_lock(&lock);
}
static void
malloc_release()
{
(void) mutex_unlock(&lock);
}
#pragma init(malloc_init)
static void
malloc_init(void)
{
(void) pthread_atfork(malloc_prepare, malloc_release, malloc_release);
}