/* $OpenBSD: alloc.c,v 1.13 2018/12/16 08:31:50 otto Exp $ */ /* $NetBSD: alloc.c,v 1.6 1997/02/04 18:36:33 thorpej Exp $ */ /* * Copyright (c) 1997 Christopher G. Demetriou. All rights reserved. * Copyright (c) 1996 * Matthias Drochner. All rights reserved. * Copyright (c) 1993 * The Regents of the University of California. All rights reserved. * * This code is derived from software contributed to Berkeley by * The Mach Operating System project at Carnegie-Mellon University. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. 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. * 3. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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. * * @(#)alloc.c 8.1 (Berkeley) 6/11/93 * * * Copyright (c) 1989, 1990, 1991 Carnegie Mellon University * All Rights Reserved. * * Author: Alessandro Forin * * Permission to use, copy, modify and distribute this software and its * documentation is hereby granted, provided that both the copyright * notice and this permission notice appear in all copies of the * software, derivative works or modified versions, and any portions * thereof, and that both notices appear in supporting documentation. * * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. * * Carnegie Mellon requests users of this software to return to * * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU * School of Computer Science * Carnegie Mellon University * Pittsburgh PA 15213-3890 * * any improvements or extensions that they make and grant Carnegie the * rights to redistribute these changes. */ /* * Dynamic memory allocator. * * Compile options: * * ALLOC_TRACE enable tracing of allocations/deallocations * * ALLOC_FIRST_FIT use a first-fit allocation algorithm, rather than * the default best-fit algorithm. * * HEAP_LIMIT heap limit address (defaults to "no limit"). * * HEAP_START start address of heap (defaults to '&end'). * * NEEDS_HEAP_H needs to #include "heap.h" to declare things * needed by HEAP_LIMIT and/or HEAP_START. * * NEEDS_HEAP_INIT needs to invoke heap_init() to initialize * heap boundaries. * * DEBUG enable debugging sanity checks. */ #include <sys/param.h> /* * Each block actually has ALIGN(unsigned) + ALIGN(size) bytes allocated * to it, as follows: * * 0 ... (sizeof(unsigned) - 1) * allocated or unallocated: holds size of user-data part of block. * * sizeof(unsigned) ... (ALIGN(sizeof(unsigned)) - 1) * allocated: unused * unallocated: depends on packing of struct fl * * ALIGN(sizeof(unsigned)) ... (ALIGN(sizeof(unsigned)) + ALIGN(data size) - 1) * allocated: user data * unallocated: depends on packing of struct fl * * 'next' is only used when the block is unallocated (i.e. on the free list). * However, note that ALIGN(sizeof(unsigned)) + ALIGN(data size) must * be at least 'sizeof(struct fl)', so that blocks can be used as structures * when on the free list. */ #include "stand.h" struct fl { unsigned size; struct fl *next; } *freelist = NULL; #ifdef NEEDS_HEAP_H #include "heap.h" #endif #ifndef NEEDS_HEAP_INIT #ifdef HEAP_START static char *top = (char *)HEAP_START; #else extern char end[]; static char *top = end; #endif #endif void * alloc(unsigned int size) { struct fl **f = &freelist, **bestf = NULL; #ifndef ALLOC_FIRST_FIT unsigned bestsize = 0xffffffff; /* greater than any real size */ #endif char *help; int failed; #ifdef NEEDS_HEAP_INIT heap_init(); #endif #ifdef ALLOC_TRACE printf("alloc(%u)", size); #endif #ifdef ALLOC_FIRST_FIT while (*f != NULL && (*f)->size < size) f = &((*f)->next); bestf = f; failed = (*bestf == NULL); #else /* scan freelist */ while (*f) { if ((*f)->size >= size) { if ((*f)->size == size) /* exact match */ goto found; if ((*f)->size < bestsize) { /* keep best fit */ bestf = f; bestsize = (*f)->size; } } f = &((*f)->next); } /* no match in freelist if bestsize unchanged */ failed = (bestsize == 0xffffffff || bestsize >= size * 2); #endif if (failed) { /* nothing found */ /* * allocate from heap, keep chunk len in * first word */ help = top; /* make _sure_ the region can hold a struct fl. */ if (size < ALIGN(sizeof (struct fl *))) size = ALIGN(sizeof (struct fl *)); top += ALIGN(sizeof(unsigned)) + ALIGN(size); #ifdef HEAP_LIMIT if (top > (char *)HEAP_LIMIT) panic("heap full (0x%lx+%u)", help, size); #endif *(unsigned *)help = ALIGN(size); #ifdef ALLOC_TRACE printf("=%p\n", help + ALIGN(sizeof(unsigned))); #endif return(help + ALIGN(sizeof(unsigned))); } /* we take the best fit */ f = bestf; #ifndef ALLOC_FIRST_FIT found: #endif /* remove from freelist */ help = (char *)*f; *f = (*f)->next; #ifdef ALLOC_TRACE printf("=%p (origsize %u)\n", help + ALIGN(sizeof(unsigned)), *(unsigned *)help); #endif return(help + ALIGN(sizeof(unsigned))); } void free(void *ptr, unsigned int size) { struct fl *f; if (ptr == NULL) return; f = (struct fl *)((char *)ptr - ALIGN(sizeof(unsigned))); #ifdef ALLOC_TRACE printf("free(%p, %u) (origsize %u)\n", ptr, size, f->size); #endif #ifdef DEBUG if (size > f->size) printf("free %u bytes @%p, should be <=%u\n", size, ptr, f->size); #ifdef HEAP_START if (ptr < (void *)HEAP_START) #else if (ptr < (void *)end) #endif printf("free: %lx before start of heap.\n", (u_long)ptr); #ifdef HEAP_LIMIT if (ptr > (void *)HEAP_LIMIT) printf("free: %lx beyond end of heap.\n", (u_long)ptr); #endif #endif /* DEBUG */ /* put into freelist */ f->next = freelist; freelist = f; }
