/* * 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 2008 Sun Microsystems, Inc. All rights reserved. * Use is subject to license terms. * Copyright 2016 Joyent, Inc. * Copyright 2024 Oxide Computer Company */ /* Copyright (c) 1988 AT&T */ /* All Rights Reserved */ #include "lint.h" #include "mallint.h" #include "mtlib.h" #include <stdalign.h> #define _misaligned(p) ((unsigned)(p) & 3) /* 4-byte "word" alignment is considered ok in LP64 */ #define _nextblk(p, size) ((TREE *)((uintptr_t)(p) + (size))) /* * memalign(align, nbytes) * * Description: * Returns a block of specified size on a specified alignment boundary. * * Algorithm: * Malloc enough to ensure that a block can be aligned correctly. * Find the alignment point and return the fragments * before and after the block. * * Errors: * Returns NULL and sets errno as follows: * [EINVAL] * if nbytes = 0, * or if alignment is misaligned, * or if the heap has been detectably corrupted. * [ENOMEM] * if the requested memory could not be allocated. */ void * memalign(size_t align, size_t nbytes) { size_t reqsize; /* Num of bytes to get from malloc() */ TREE *p; /* Ptr returned from malloc() */ TREE *blk; /* For addressing fragment blocks */ size_t blksize; /* Current (shrinking) block size */ TREE *alignedp; /* Ptr to properly aligned boundary */ TREE *aligned_blk; /* The block to be returned */ size_t frag_size; /* size of fragments fore and aft */ size_t x; if (!primary_link_map) { errno = ENOTSUP; return (NULL); } /* * check for valid size and alignment parameters * MAX_ALIGN check prevents overflow in later calculation. */ if (nbytes == 0 || _misaligned(align) || align == 0 || align > MAX_ALIGN) { errno = EINVAL; return (NULL); } /* * Malloc enough memory to guarantee that the result can be * aligned correctly. The worst case is when malloc returns * a block so close to the next alignment boundary that a * fragment of minimum size cannot be created. In order to * make sure we can handle this, we need to force the * alignment to be at least as large as the minimum frag size * (MINSIZE + WORDSIZE). */ /* check for size that could overflow calculations */ if (nbytes > MAX_MALLOC) { errno = ENOMEM; return (NULL); } ROUND(nbytes); if (nbytes < MINSIZE) nbytes = MINSIZE; ROUND(align); while (align < MINSIZE + WORDSIZE) align <<= 1; reqsize = nbytes + align + (MINSIZE + WORDSIZE); /* check for overflow */ if (reqsize < nbytes) { errno = ENOMEM; return (NULL); } p = (TREE *)malloc(reqsize); if (p == (TREE *)NULL) { /* malloc sets errno */ return (NULL); } (void) mutex_lock(&libc_malloc_lock); /* * get size of the entire block (overhead and all) */ blk = BLOCK(p); /* back up to get length word */ blksize = SIZE(blk); CLRBITS01(blksize); /* * locate the proper alignment boundary within the block. */ x = (size_t)p; if (x % align != 0) x += align - (x % align); alignedp = (TREE *)x; aligned_blk = BLOCK(alignedp); /* * Check out the space to the left of the alignment * boundary, and split off a fragment if necessary. */ frag_size = (size_t)aligned_blk - (size_t)blk; if (frag_size != 0) { /* * Create a fragment to the left of the aligned block. */ if (frag_size < MINSIZE + WORDSIZE) { /* * Not enough space. So make the split * at the other end of the alignment unit. * We know this yields enough space, because * we forced align >= MINSIZE + WORDSIZE above. */ frag_size += align; aligned_blk = _nextblk(aligned_blk, align); } blksize -= frag_size; SIZE(aligned_blk) = blksize | BIT0; frag_size -= WORDSIZE; SIZE(blk) = frag_size | BIT0 | ISBIT1(SIZE(blk)); _free_unlocked(DATA(blk)); } /* * Is there a (sufficiently large) fragment to the * right of the aligned block? */ frag_size = blksize - nbytes; if (frag_size >= MINSIZE + WORDSIZE) { /* * split and free a fragment on the right */ blksize = SIZE(aligned_blk); SIZE(aligned_blk) = nbytes; blk = NEXT(aligned_blk); SETOLD01(SIZE(aligned_blk), blksize); frag_size -= WORDSIZE; SIZE(blk) = frag_size | BIT0; _free_unlocked(DATA(blk)); } (void) mutex_unlock(&libc_malloc_lock); return (DATA(aligned_blk)); } /* * This is the ISO/IEC C11 version of memalign. We have kept it as a separate * function, but it is almost the same thing. aligned_alloc allows any alignment * that is a fundamental alignment of one of the data types. However, * aligned_alloc (like malloc) is required to ensure that the alignment is good * for any of the base data objects. Our expectation is that memalign guarantees * this. To work with memalign(), we round up any smaller alignments to the * alignment of a pointer which is generally the requirement of memalign(3C). * * Note, aligned_alloc is implemented in terms of just calling memalign this way * so that way interposing libraries can just interpose on that. */ void * aligned_alloc(size_t align, size_t size) { if (align == 0 || (align & (align - 1)) != 0) { errno = EINVAL; return (NULL); } if (align < alignof (uintptr_t)) align = alignof (uintptr_t); return (memalign(align, size)); }
