xref: /illumos-gate/usr/src/lib/libc/port/sys/sbrk.c (revision d2a70789f056fc6c9ce3ab047b52126d80b0e3da)
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 weak _sbrk = sbrk
28 #pragma weak _brk = brk
29 
30 #include "lint.h"
31 #include <synch.h>
32 #include <errno.h>
33 #include <sys/isa_defs.h>
34 #include <sys/types.h>
35 #include <sys/sysmacros.h>
36 #include <inttypes.h>
37 #include <unistd.h>
38 #include "mtlib.h"
39 #include "libc.h"
40 
41 void *_nd = NULL;
42 mutex_t __sbrk_lock = DEFAULTMUTEX;
43 
44 extern intptr_t _brk_unlocked(void *);
45 void *_sbrk_unlocked(intptr_t);
46 
47 /*
48  * The break must always be at least 8-byte aligned
49  */
50 #if (_MAX_ALIGNMENT < 8)
51 #define	ALIGNSZ		8
52 #else
53 #define	ALIGNSZ		_MAX_ALIGNMENT
54 #endif
55 
56 #define	BRKALIGN(x)	(caddr_t)P2ROUNDUP((uintptr_t)(x), ALIGNSZ)
57 
58 void *
sbrk(intptr_t addend)59 sbrk(intptr_t addend)
60 {
61 	void *result;
62 
63 	if (!primary_link_map) {
64 		errno = ENOTSUP;
65 		return ((void *)-1);
66 	}
67 	lmutex_lock(&__sbrk_lock);
68 	result = _sbrk_unlocked(addend);
69 	lmutex_unlock(&__sbrk_lock);
70 
71 	return (result);
72 }
73 
74 /*
75  * _sbrk_unlocked() aligns the old break, adds the addend, aligns
76  * the new break, and calls _brk_unlocked() to set the new break.
77  * We must align the old break because _nd may begin life misaligned.
78  * The addend can be either positive or negative, so there are two
79  * overflow/underflow edge conditions to reject:
80  *
81  *   - the addend is negative and brk + addend < 0.
82  *   - the addend is positive and brk + addend > ULONG_MAX
83  */
84 void *
_sbrk_unlocked(intptr_t addend)85 _sbrk_unlocked(intptr_t addend)
86 {
87 	char *old_brk;
88 	char *new_brk;
89 
90 	if (_nd == NULL) {
91 		_nd = (void *)_brk_unlocked(0);
92 	}
93 
94 	old_brk = BRKALIGN(_nd);
95 	new_brk = BRKALIGN(old_brk + addend);
96 
97 	if ((addend > 0 && new_brk < old_brk) ||
98 	    (addend < 0 && new_brk > old_brk)) {
99 		errno = ENOMEM;
100 		return ((void *)-1);
101 	}
102 	if (_brk_unlocked(new_brk) != 0)
103 		return ((void *)-1);
104 	_nd = new_brk;
105 	return (old_brk);
106 }
107 
108 /*
109  * _sbrk_grow_aligned() aligns the old break to a low_align boundry,
110  * adds min_size, aligns to a high_align boundry, and calls _brk_unlocked()
111  * to set the new break.  The low_aligned-aligned value is returned, and
112  * the actual space allocated is returned through actual_size.
113  *
114  * Unlike sbrk(2), _sbrk_grow_aligned takes an unsigned size, and does
115  * not allow shrinking the heap.
116  */
117 void *
_sbrk_grow_aligned(size_t min_size,size_t low_align,size_t high_align,size_t * actual_size)118 _sbrk_grow_aligned(size_t min_size, size_t low_align, size_t high_align,
119     size_t *actual_size)
120 {
121 	uintptr_t old_brk;
122 	uintptr_t ret_brk;
123 	uintptr_t high_brk;
124 	uintptr_t new_brk;
125 	intptr_t brk_result;
126 
127 	if (!primary_link_map) {
128 		errno = ENOTSUP;
129 		return ((void *)-1);
130 	}
131 	if ((low_align & (low_align - 1)) != 0 ||
132 	    (high_align & (high_align - 1)) != 0) {
133 		errno = EINVAL;
134 		return ((void *)-1);
135 	}
136 	low_align = MAX(low_align, ALIGNSZ);
137 	high_align = MAX(high_align, ALIGNSZ);
138 
139 	lmutex_lock(&__sbrk_lock);
140 
141 	if (_nd == NULL)
142 		_nd = (void *)_brk_unlocked(0);
143 
144 	old_brk = (uintptr_t)BRKALIGN(_nd);
145 	ret_brk = P2ROUNDUP(old_brk, low_align);
146 	high_brk = ret_brk + min_size;
147 	new_brk = P2ROUNDUP(high_brk, high_align);
148 
149 	/*
150 	 * Check for overflow
151 	 */
152 	if (ret_brk < old_brk || high_brk < ret_brk || new_brk < high_brk) {
153 		lmutex_unlock(&__sbrk_lock);
154 		errno = ENOMEM;
155 		return ((void *)-1);
156 	}
157 
158 	if ((brk_result = _brk_unlocked((void *)new_brk)) == 0)
159 		_nd = (void *)new_brk;
160 	lmutex_unlock(&__sbrk_lock);
161 
162 	if (brk_result != 0)
163 		return ((void *)-1);
164 
165 	if (actual_size != NULL)
166 		*actual_size = (new_brk - ret_brk);
167 	return ((void *)ret_brk);
168 }
169 
170 int
brk(void * new_brk)171 brk(void *new_brk)
172 {
173 	intptr_t result;
174 
175 	/*
176 	 * brk(2) will return the current brk if given an argument of 0, so we
177 	 * need to fail it here
178 	 */
179 	if (new_brk == 0) {
180 		errno = ENOMEM;
181 		return (-1);
182 	}
183 
184 	if (!primary_link_map) {
185 		errno = ENOTSUP;
186 		return (-1);
187 	}
188 	/*
189 	 * Need to align this here;  _brk_unlocked won't do it for us.
190 	 */
191 	new_brk = BRKALIGN(new_brk);
192 
193 	lmutex_lock(&__sbrk_lock);
194 	if ((result = _brk_unlocked(new_brk)) == 0)
195 		_nd = new_brk;
196 	lmutex_unlock(&__sbrk_lock);
197 
198 	return (result);
199 }
200