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      1 /*
      2  * CDDL HEADER START
      3  *
      4  * The contents of this file are subject to the terms of the
      5  * Common Development and Distribution License (the "License").
      6  * You may not use this file except in compliance with the License.
      7  *
      8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
      9  * or http://www.opensolaris.org/os/licensing.
     10  * See the License for the specific language governing permissions
     11  * and limitations under the License.
     12  *
     13  * When distributing Covered Code, include this CDDL HEADER in each
     14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
     15  * If applicable, add the following below this CDDL HEADER, with the
     16  * fields enclosed by brackets "[]" replaced with your own identifying
     17  * information: Portions Copyright [yyyy] [name of copyright owner]
     18  *
     19  * CDDL HEADER END
     20  */
     21 
     22 /*
     23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
     24  * Use is subject to license terms.
     25  */
     26 
     27 #pragma ident	"%Z%%M%	%I%	%E% SMI"
     28 
     29 #pragma weak _sbrk = sbrk
     30 #pragma weak _brk = brk
     31 
     32 #include "lint.h"
     33 #include <synch.h>
     34 #include <errno.h>
     35 #include <sys/isa_defs.h>
     36 #include <sys/types.h>
     37 #include <sys/sysmacros.h>
     38 #include <inttypes.h>
     39 #include <unistd.h>
     40 #include "mtlib.h"
     41 #include "libc.h"
     42 
     43 extern int _end;
     44 void *_nd = &_end;
     45 mutex_t __sbrk_lock = DEFAULTMUTEX;
     46 
     47 extern int _brk_unlocked(void *);
     48 extern void *_sbrk_unlocked(intptr_t);
     49 
     50 /*
     51  * The break must always be at least 8-byte aligned
     52  */
     53 #if (_MAX_ALIGNMENT < 8)
     54 #define	ALIGNSZ		8
     55 #else
     56 #define	ALIGNSZ		_MAX_ALIGNMENT
     57 #endif
     58 
     59 #define	BRKALIGN(x)	(caddr_t)P2ROUNDUP((uintptr_t)(x), ALIGNSZ)
     60 
     61 void *
     62 sbrk(intptr_t addend)
     63 {
     64 	void *result;
     65 
     66 	if (!primary_link_map) {
     67 		errno = ENOTSUP;
     68 		return ((void *)-1);
     69 	}
     70 	lmutex_lock(&__sbrk_lock);
     71 	result = _sbrk_unlocked(addend);
     72 	lmutex_unlock(&__sbrk_lock);
     73 
     74 	return (result);
     75 }
     76 
     77 /*
     78  * _sbrk_unlocked() aligns the old break, adds the addend, aligns
     79  * the new break, and calls _brk_unlocked() to set the new break.
     80  * We must align the old break because _nd may begin life misaligned.
     81  * The addend can be either positive or negative, so there are two
     82  * overflow/underflow edge conditions to reject:
     83  *
     84  *   - the addend is negative and brk + addend < 0.
     85  *   - the addend is positive and brk + addend > ULONG_MAX
     86  */
     87 void *
     88 _sbrk_unlocked(intptr_t addend)
     89 {
     90 	char *old_brk = BRKALIGN(_nd);
     91 	char *new_brk = BRKALIGN(old_brk + addend);
     92 
     93 	if ((addend > 0 && new_brk < old_brk) ||
     94 	    (addend < 0 && new_brk > old_brk)) {
     95 		errno = ENOMEM;
     96 		return ((void *)-1);
     97 	}
     98 	if (_brk_unlocked(new_brk) != 0)
     99 		return ((void *)-1);
    100 	_nd = new_brk;
    101 	return (old_brk);
    102 }
    103 
    104 /*
    105  * _sbrk_grow_aligned() aligns the old break to a low_align boundry,
    106  * adds min_size, aligns to a high_align boundry, and calls _brk_unlocked()
    107  * to set the new break.  The low_aligned-aligned value is returned, and
    108  * the actual space allocated is returned through actual_size.
    109  *
    110  * Unlike sbrk(2), _sbrk_grow_aligned takes an unsigned size, and does
    111  * not allow shrinking the heap.
    112  */
    113 void *
    114 _sbrk_grow_aligned(size_t min_size, size_t low_align, size_t high_align,
    115     size_t *actual_size)
    116 {
    117 	uintptr_t old_brk;
    118 	uintptr_t ret_brk;
    119 	uintptr_t high_brk;
    120 	uintptr_t new_brk;
    121 	int brk_result;
    122 
    123 	if (!primary_link_map) {
    124 		errno = ENOTSUP;
    125 		return ((void *)-1);
    126 	}
    127 	if ((low_align & (low_align - 1)) != 0 ||
    128 	    (high_align & (high_align - 1)) != 0) {
    129 		errno = EINVAL;
    130 		return ((void *)-1);
    131 	}
    132 	low_align = MAX(low_align, ALIGNSZ);
    133 	high_align = MAX(high_align, ALIGNSZ);
    134 
    135 	lmutex_lock(&__sbrk_lock);
    136 
    137 	old_brk = (uintptr_t)BRKALIGN(_nd);
    138 	ret_brk = P2ROUNDUP(old_brk, low_align);
    139 	high_brk = ret_brk + min_size;
    140 	new_brk = P2ROUNDUP(high_brk, high_align);
    141 
    142 	/*
    143 	 * Check for overflow
    144 	 */
    145 	if (ret_brk < old_brk || high_brk < ret_brk || new_brk < high_brk) {
    146 		lmutex_unlock(&__sbrk_lock);
    147 		errno = ENOMEM;
    148 		return ((void *)-1);
    149 	}
    150 
    151 	if ((brk_result = _brk_unlocked((void *)new_brk)) == 0)
    152 		_nd = (void *)new_brk;
    153 	lmutex_unlock(&__sbrk_lock);
    154 
    155 	if (brk_result != 0)
    156 		return ((void *)-1);
    157 
    158 	if (actual_size != NULL)
    159 		*actual_size = (new_brk - ret_brk);
    160 	return ((void *)ret_brk);
    161 }
    162 
    163 int
    164 brk(void *new_brk)
    165 {
    166 	int result;
    167 
    168 	if (!primary_link_map) {
    169 		errno = ENOTSUP;
    170 		return (-1);
    171 	}
    172 	/*
    173 	 * Need to align this here;  _brk_unlocked won't do it for us.
    174 	 */
    175 	new_brk = BRKALIGN(new_brk);
    176 
    177 	lmutex_lock(&__sbrk_lock);
    178 	if ((result = _brk_unlocked(new_brk)) == 0)
    179 		_nd = new_brk;
    180 	lmutex_unlock(&__sbrk_lock);
    181 
    182 	return (result);
    183 }
    184