FreeBSD/Linux Kernel Cross Reference
sys/vm/redzone.c
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 TUNABLE_INT("vm.redzone.panic", &redzone_panic);
45 SYSCTL_INT(_vm_redzone, OID_AUTO, panic, CTLFLAG_RW, &redzone_panic, 0,
46 "Panic when buffer corruption is detected");
47
48 #define REDZONE_CHSIZE (16)
49 #define REDZONE_CFSIZE (16)
50 #define REDZONE_HSIZE (sizeof(struct stack) + sizeof(u_long) + REDZONE_CHSIZE)
51 #define REDZONE_FSIZE (REDZONE_CFSIZE)
52
53 static u_long
54 redzone_roundup(u_long n)
55 {
56
57 if (n < REDZONE_HSIZE)
58 n = REDZONE_HSIZE;
59 if (n <= 128)
60 return (128);
61 else if (n <= 256)
62 return (256);
63 else if (n <= 512)
64 return (512);
65 else if (n <= 1024)
66 return (1024);
67 else if (n <= 2048)
68 return (2048);
69 return (PAGE_SIZE);
70 }
71
72 u_long
73 redzone_get_size(caddr_t naddr)
74 {
75 u_long nsize;
76
77 bcopy(naddr - REDZONE_CHSIZE - sizeof(u_long), &nsize, sizeof(nsize));
78 return (nsize);
79 }
80
81 u_long
82 redzone_size_ntor(u_long nsize)
83 {
84
85 return (nsize + redzone_roundup(nsize) + REDZONE_FSIZE);
86 }
87
88 void *
89 redzone_addr_ntor(caddr_t naddr)
90 {
91
92 return (naddr - redzone_roundup(redzone_get_size(naddr)));
93 }
94
95 /*
96 * Set redzones and remember allocation backtrace.
97 */
98 void *
99 redzone_setup(caddr_t raddr, u_long nsize)
100 {
101 struct stack st;
102 caddr_t haddr, faddr;
103
104 atomic_add_long(&redzone_extra_mem, redzone_size_ntor(nsize) - nsize);
105
106 haddr = raddr + redzone_roundup(nsize) - REDZONE_HSIZE;
107 faddr = haddr + REDZONE_HSIZE + nsize;
108
109 /* Redzone header. */
110 stack_save(&st);
111 bcopy(&st, haddr, sizeof(st));
112 haddr += sizeof(st);
113 bcopy(&nsize, haddr, sizeof(nsize));
114 haddr += sizeof(nsize);
115 memset(haddr, 0x42, REDZONE_CHSIZE);
116 haddr += REDZONE_CHSIZE;
117
118 /* Redzone footer. */
119 memset(faddr, 0x42, REDZONE_CFSIZE);
120
121 return (haddr);
122 }
123
124 /*
125 * Verify redzones.
126 * This function is called on free() and realloc().
127 */
128 void
129 redzone_check(caddr_t naddr)
130 {
131 struct stack ast, fst;
132 caddr_t haddr, faddr;
133 u_int ncorruptions;
134 u_long nsize;
135 int i;
136
137 haddr = naddr - REDZONE_HSIZE;
138 bcopy(haddr, &ast, sizeof(ast));
139 haddr += sizeof(ast);
140 bcopy(haddr, &nsize, sizeof(nsize));
141 haddr += sizeof(nsize);
142
143 atomic_subtract_long(&redzone_extra_mem,
144 redzone_size_ntor(nsize) - nsize);
145
146 /* Look for buffer underflow. */
147 ncorruptions = 0;
148 for (i = 0; i < REDZONE_CHSIZE; i++, haddr++) {
149 if (*(u_char *)haddr != 0x42)
150 ncorruptions++;
151 }
152 if (ncorruptions > 0) {
153 printf("REDZONE: Buffer underflow detected. %u byte%s "
154 "corrupted before %p (%lu bytes allocated).\n",
155 ncorruptions, ncorruptions == 1 ? "" : "s", naddr, nsize);
156 printf("Allocation backtrace:\n");
157 stack_print_ddb(&ast);
158 printf("Free backtrace:\n");
159 stack_save(&fst);
160 stack_print_ddb(&fst);
161 if (redzone_panic)
162 panic("Stopping here.");
163 }
164 faddr = naddr + nsize;
165 /* Look for buffer overflow. */
166 ncorruptions = 0;
167 for (i = 0; i < REDZONE_CFSIZE; i++, faddr++) {
168 if (*(u_char *)faddr != 0x42)
169 ncorruptions++;
170 }
171 if (ncorruptions > 0) {
172 printf("REDZONE: Buffer overflow detected. %u byte%s corrupted "
173 "after %p (%lu bytes allocated).\n", ncorruptions,
174 ncorruptions == 1 ? "" : "s", naddr + nsize, nsize);
175 printf("Allocation backtrace:\n");
176 stack_print_ddb(&ast);
177 printf("Free backtrace:\n");
178 stack_save(&fst);
179 stack_print_ddb(&fst);
180 if (redzone_panic)
181 panic("Stopping here.");
182 }
183 }
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