xref: /freebsd/lib/libc/sys/brk.c (revision f126890ac5386406dadf7c4cfa9566cbb56537c5)
1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause
3  *
4  * Copyright (c) 2018 Mark Johnston <markj@FreeBSD.org>
5  *
6  * Redistribution and use in source and binary forms, with or without
7  * modification, are permitted provided that the following conditions
8  * are met:
9  * 1. Redistributions of source code must retain the above copyright
10  *    notice, this list of conditions and the following disclaimer.
11  * 2. Redistributions in binary form must reproduce the above copyright
12  *    notice, this list of conditions and the following disclaimer in the
13  *    documentation and/or other materials provided with the distribution.
14  *
15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25  * SUCH DAMAGE.
26  */
27 
28 #include <sys/types.h>
29 #include <sys/syscall.h>
30 #include <errno.h>
31 #include <stdint.h>
32 #include <stdlib.h>
33 
34 void *__sys_break(char *nsize);
35 
36 static uintptr_t curbrk, minbrk;
37 static int curbrk_initted;
38 
39 static int
40 initbrk(void)
41 {
42 	void *newbrk;
43 
44 	if (!curbrk_initted) {
45 		newbrk = __sys_break(NULL);
46 		if (newbrk == (void *)-1)
47 			return (-1);
48 		curbrk = minbrk = (uintptr_t)newbrk;
49 		curbrk_initted = 1;
50 	}
51 	return (0);
52 }
53 
54 static void *
55 mvbrk(void *addr)
56 {
57 	uintptr_t oldbrk;
58 
59 	if ((uintptr_t)addr < minbrk) {
60 		/* Emulate legacy error handling in the syscall. */
61 		errno = EINVAL;
62 		return ((void *)-1);
63 	}
64 	if (__sys_break(addr) == (void *)-1)
65 		return ((void *)-1);
66 	oldbrk = curbrk;
67 	curbrk = (uintptr_t)addr;
68 	return ((void *)oldbrk);
69 }
70 
71 int
72 brk(const void *addr)
73 {
74 
75 	if (initbrk() == -1)
76 		return (-1);
77 	if ((uintptr_t)addr < minbrk)
78 		addr = (void *)minbrk;
79 	return (mvbrk(__DECONST(void *, addr)) == (void *)-1 ? -1 : 0);
80 }
81 
82 int
83 _brk(const void *addr)
84 {
85 
86 	if (initbrk() == -1)
87 		return (-1);
88 	return (mvbrk(__DECONST(void *, addr)) == (void *)-1 ? -1 : 0);
89 }
90 
91 void *
92 sbrk(intptr_t incr)
93 {
94 
95 	if (initbrk() == -1)
96 		return ((void *)-1);
97 	if ((incr > 0 && curbrk + incr < curbrk) ||
98 	    (incr < 0 && curbrk + incr > curbrk)) {
99 		/* Emulate legacy error handling in the syscall. */
100 		errno = EINVAL;
101 		return ((void *)-1);
102 	}
103 	return (mvbrk((void *)(curbrk + incr)));
104 }
105