1/*
2 * Revision 12: http://theos.com/~deraadt/snprintf.c
3 *
4 * Copyright (c) 1997 Theo de Raadt
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 ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27#ifndef __VMS
28# include <sys/param.h>
29#endif
30#include <sys/types.h>
31#include <sys/mman.h>
32#include <signal.h>
33#include <stdio.h>
34#if __STDC__
35#include <stdarg.h>
36#include <stdlib.h>
37#else
38#include <varargs.h>
39#endif
40#include <setjmp.h>
41#include <unistd.h>
42#include <string.h>
43
44#ifndef roundup
45#define roundup(x, y) ((((x)+((y)-1))/(y))*(y))
46#endif
47
48#ifdef __sgi
49#define size_t ssize_t
50#endif
51
52static int pgsize;
53static char *curobj;
54static int caught;
55static sigjmp_buf bail;
56
57#define EXTRABYTES	2	/* XXX: why 2? you don't want to know */
58
59static char *
60msetup(str, n)
61	char *str;
62	size_t n;
63{
64	char *e;
65
66	if (n == 0)
67		return NULL;
68	if (pgsize == 0)
69		pgsize = getpagesize();
70	curobj = (char *)malloc(n + EXTRABYTES + pgsize * 2);
71	if (curobj == NULL)
72		return NULL;
73	e = curobj + n + EXTRABYTES;
74	e = (char *)roundup((unsigned long)e, pgsize);
75	if (mprotect(e, pgsize, PROT_NONE) == -1) {
76		free(curobj);
77		curobj = NULL;
78		return NULL;
79	}
80	e = e - n - EXTRABYTES;
81	*e = '\0';
82	return (e);
83}
84
85static void
86  mcatch( int a )
87{
88	siglongjmp(bail, 1);
89}
90
91static void
92mcleanup(str, n, p)
93	char *str;
94	size_t n;
95	char *p;
96{
97	strncpy(str, p, n-1);
98	str[n-1] = '\0';
99	if (mprotect((caddr_t)(p + n + EXTRABYTES), pgsize,
100	    PROT_READ|PROT_WRITE|PROT_EXEC) == -1)
101		mprotect((caddr_t)(p + n + EXTRABYTES), pgsize,
102		    PROT_READ|PROT_WRITE);
103	free(curobj);
104}
105
106int
107#if __STDC__
108vsnprintf(char *str, size_t n, char const *fmt, va_list ap)
109#else
110vsnprintf(str, n, fmt, ap)
111	char *str;
112	size_t n;
113	char *fmt;
114	char *ap;
115#endif
116{
117	struct sigaction osa, nsa;
118	char *p;
119	int ret = n + 1;	/* if we bail, indicated we overflowed */
120
121	memset(&nsa, 0, sizeof nsa);
122	nsa.sa_handler = mcatch;
123	sigemptyset(&nsa.sa_mask);
124
125	p = msetup(str, n);
126	if (p == NULL) {
127		*str = '\0';
128		return 0;
129	}
130	if (sigsetjmp(bail, 1) == 0) {
131		if (sigaction(SIGSEGV, &nsa, &osa) == -1) {
132			mcleanup(str, n, p);
133			return (0);
134		}
135		ret = vsprintf(p, fmt, ap);
136	}
137	mcleanup(str, n, p);
138	(void) sigaction(SIGSEGV, &osa, NULL);
139	return (ret);
140}
141
142int
143#if __STDC__
144snprintf(char *str, size_t n, char const *fmt, ...)
145#else
146snprintf(str, n, fmt, va_alist)
147	char *str;
148	size_t n;
149	char *fmt;
150	va_dcl
151#endif
152{
153	va_list ap;
154#if __STDC__
155	va_start(ap, fmt);
156#else
157	va_start(ap);
158#endif
159
160	return (vsnprintf(str, n, fmt, ap));
161	va_end(ap);
162}
163
164
165
166