xref: /freebsd/sys/vm/redzone.c (revision 6574b8ed19b093f0af09501d2c9676c28993cb97)
1 /*-
2  * Copyright (c) 2006 Pawel Jakub Dawidek <pjd@FreeBSD.org>
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  *
14  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24  * SUCH DAMAGE.
25  */
26 
27 #include <sys/cdefs.h>
28 __FBSDID("$FreeBSD$");
29 
30 #include <sys/param.h>
31 #include <sys/systm.h>
32 #include <sys/kernel.h>
33 #include <sys/stack.h>
34 #include <sys/sysctl.h>
35 
36 #include <vm/redzone.h>
37 
38 
39 static SYSCTL_NODE(_vm, OID_AUTO, redzone, CTLFLAG_RW, NULL, "RedZone data");
40 static u_long redzone_extra_mem = 0;
41 SYSCTL_ULONG(_vm_redzone, OID_AUTO, extra_mem, CTLFLAG_RD, &redzone_extra_mem,
42     0, "Extra memory allocated by redzone");
43 static int redzone_panic = 0;
44 SYSCTL_INT(_vm_redzone, OID_AUTO, panic, CTLFLAG_RWTUN, &redzone_panic, 0,
45     "Panic when buffer corruption is detected");
46 
47 #define	REDZONE_CHSIZE	(16)
48 #define	REDZONE_CFSIZE	(16)
49 #define	REDZONE_HSIZE	(sizeof(struct stack) + sizeof(u_long) + REDZONE_CHSIZE)
50 #define	REDZONE_FSIZE	(REDZONE_CFSIZE)
51 
52 static u_long
53 redzone_roundup(u_long n)
54 {
55 
56 	if (n < REDZONE_HSIZE)
57 		n = REDZONE_HSIZE;
58 	if (n <= 128)
59 		return (128);
60 	else if (n <= 256)
61 		return (256);
62 	else if (n <= 512)
63 		return (512);
64 	else if (n <= 1024)
65 		return (1024);
66 	else if (n <= 2048)
67 		return (2048);
68 	return (PAGE_SIZE);
69 }
70 
71 u_long
72 redzone_get_size(caddr_t naddr)
73 {
74 	u_long nsize;
75 
76 	bcopy(naddr - REDZONE_CHSIZE - sizeof(u_long), &nsize, sizeof(nsize));
77 	return (nsize);
78 }
79 
80 u_long
81 redzone_size_ntor(u_long nsize)
82 {
83 
84 	return (nsize + redzone_roundup(nsize) + REDZONE_FSIZE);
85 }
86 
87 void *
88 redzone_addr_ntor(caddr_t naddr)
89 {
90 
91 	return (naddr - redzone_roundup(redzone_get_size(naddr)));
92 }
93 
94 /*
95  * Set redzones and remember allocation backtrace.
96  */
97 void *
98 redzone_setup(caddr_t raddr, u_long nsize)
99 {
100 	struct stack st;
101 	caddr_t haddr, faddr;
102 
103 	atomic_add_long(&redzone_extra_mem, redzone_size_ntor(nsize) - nsize);
104 
105 	haddr = raddr + redzone_roundup(nsize) - REDZONE_HSIZE;
106 	faddr = haddr + REDZONE_HSIZE + nsize;
107 
108 	/* Redzone header. */
109 	stack_save(&st);
110 	bcopy(&st, haddr, sizeof(st));
111 	haddr += sizeof(st);
112 	bcopy(&nsize, haddr, sizeof(nsize));
113 	haddr += sizeof(nsize);
114 	memset(haddr, 0x42, REDZONE_CHSIZE);
115 	haddr += REDZONE_CHSIZE;
116 
117 	/* Redzone footer. */
118 	memset(faddr, 0x42, REDZONE_CFSIZE);
119 
120 	return (haddr);
121 }
122 
123 /*
124  * Verify redzones.
125  * This function is called on free() and realloc().
126  */
127 void
128 redzone_check(caddr_t naddr)
129 {
130 	struct stack ast, fst;
131 	caddr_t haddr, faddr;
132 	u_int ncorruptions;
133 	u_long nsize;
134 	int i;
135 
136 	haddr = naddr - REDZONE_HSIZE;
137 	bcopy(haddr, &ast, sizeof(ast));
138 	haddr += sizeof(ast);
139 	bcopy(haddr, &nsize, sizeof(nsize));
140 	haddr += sizeof(nsize);
141 
142 	atomic_subtract_long(&redzone_extra_mem,
143 	    redzone_size_ntor(nsize) - nsize);
144 
145 	/* Look for buffer underflow. */
146 	ncorruptions = 0;
147 	for (i = 0; i < REDZONE_CHSIZE; i++, haddr++) {
148 		if (*(u_char *)haddr != 0x42)
149 			ncorruptions++;
150 	}
151 	if (ncorruptions > 0) {
152 		printf("REDZONE: Buffer underflow detected. %u byte%s "
153 		    "corrupted before %p (%lu bytes allocated).\n",
154 		    ncorruptions, ncorruptions == 1 ? "" : "s", naddr, nsize);
155 		printf("Allocation backtrace:\n");
156 		stack_print_ddb(&ast);
157 		printf("Free backtrace:\n");
158 		stack_save(&fst);
159 		stack_print_ddb(&fst);
160 		if (redzone_panic)
161 			panic("Stopping here.");
162 	}
163 	faddr = naddr + nsize;
164 	/* Look for buffer overflow. */
165 	ncorruptions = 0;
166 	for (i = 0; i < REDZONE_CFSIZE; i++, faddr++) {
167 		if (*(u_char *)faddr != 0x42)
168 			ncorruptions++;
169 	}
170 	if (ncorruptions > 0) {
171 		printf("REDZONE: Buffer overflow detected. %u byte%s corrupted "
172 		    "after %p (%lu bytes allocated).\n", ncorruptions,
173 		    ncorruptions == 1 ? "" : "s", naddr + nsize, nsize);
174 		printf("Allocation backtrace:\n");
175 		stack_print_ddb(&ast);
176 		printf("Free backtrace:\n");
177 		stack_save(&fst);
178 		stack_print_ddb(&fst);
179 		if (redzone_panic)
180 			panic("Stopping here.");
181 	}
182 }
183