1 /*
2 * Stack-less Just-In-Time compiler
3 *
4 * Copyright Zoltan Herczeg (hzmester@freemail.hu). All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without modification, are
7 * permitted provided that the following conditions are met:
8 *
9 * 1. Redistributions of source code must retain the above copyright notice, this list of
10 * conditions and the following disclaimer.
11 *
12 * 2. Redistributions in binary form must reproduce the above copyright notice, this list
13 * of conditions and the following disclaimer in the documentation and/or other materials
14 * provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) AND CONTRIBUTORS ``AS IS'' AND ANY
17 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
19 * SHALL THE COPYRIGHT HOLDER(S) OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
21 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
22 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
23 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
24 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27 /*
28 This file contains a simple W^X executable memory allocator for POSIX
29 like systems and Windows
30
31 In *NIX, MAP_ANON is required (that is considered a feature) so make
32 sure to set the right availability macros for your system or the code
33 will fail to build.
34
35 If your system doesn't support mapping of anonymous pages (ex: IRIX) it
36 is also likely that it doesn't need this allocator and should be using
37 the standard one instead.
38
39 It allocates a separate map for each code block and may waste a lot of
40 memory, because whatever was requested, will be rounded up to the page
41 size (minimum 4KB, but could be even bigger).
42
43 It changes the page permissions (RW <-> RX) as needed and therefore, if you
44 will be updating the code after it has been generated, need to make sure to
45 block any concurrent execution, or could result in a SIGBUS, that could
46 even manifest itself at a different address than the one that was being
47 modified.
48
49 Only use if you are unable to use the regular allocator because of security
50 restrictions and adding exceptions to your application or the system are
51 not possible.
52 */
53
54 #define SLJIT_UPDATE_WX_FLAGS(from, to, enable_exec) \
55 sljit_update_wx_flags((from), (to), (enable_exec))
56
57 #ifndef _WIN32
58 #include <sys/types.h>
59 #include <sys/mman.h>
60
61 #ifdef __NetBSD__
62 #if defined(PROT_MPROTECT)
63 #define check_se_protected(ptr, size) (0)
64 #define SLJIT_PROT_WX PROT_MPROTECT(PROT_EXEC)
65 #else /* !PROT_MPROTECT */
66 #ifdef _NETBSD_SOURCE
67 #include <sys/param.h>
68 #else /* !_NETBSD_SOURCE */
69 typedef unsigned int u_int;
70 #define devmajor_t sljit_s32
71 #endif /* _NETBSD_SOURCE */
72 #include <sys/sysctl.h>
73 #include <unistd.h>
74
75 #define check_se_protected(ptr, size) netbsd_se_protected()
76
netbsd_se_protected(void)77 static SLJIT_INLINE int netbsd_se_protected(void)
78 {
79 int mib[3];
80 int paxflags;
81 size_t len = sizeof(paxflags);
82
83 mib[0] = CTL_PROC;
84 mib[1] = getpid();
85 mib[2] = PROC_PID_PAXFLAGS;
86
87 if (SLJIT_UNLIKELY(sysctl(mib, 3, &paxflags, &len, NULL, 0) < 0))
88 return -1;
89
90 return (paxflags & CTL_PROC_PAXFLAGS_MPROTECT) ? -1 : 0;
91 }
92 #endif /* PROT_MPROTECT */
93 #else /* POSIX */
94 #define check_se_protected(ptr, size) generic_se_protected(ptr, size)
95
generic_se_protected(void * ptr,sljit_uw size)96 static SLJIT_INLINE int generic_se_protected(void *ptr, sljit_uw size)
97 {
98 if (SLJIT_LIKELY(!mprotect(ptr, size, PROT_EXEC)))
99 return mprotect(ptr, size, PROT_READ | PROT_WRITE);
100
101 return -1;
102 }
103 #endif /* NetBSD */
104
105 #if defined SLJIT_SINGLE_THREADED && SLJIT_SINGLE_THREADED
106 #define SLJIT_SE_LOCK()
107 #define SLJIT_SE_UNLOCK()
108 #else /* !SLJIT_SINGLE_THREADED */
109 #include <pthread.h>
110 #define SLJIT_SE_LOCK() pthread_mutex_lock(&se_lock)
111 #define SLJIT_SE_UNLOCK() pthread_mutex_unlock(&se_lock)
112 #endif /* SLJIT_SINGLE_THREADED */
113
114 #ifndef SLJIT_PROT_WX
115 #define SLJIT_PROT_WX 0
116 #endif /* !SLJIT_PROT_WX */
117
sljit_malloc_exec(sljit_uw size)118 SLJIT_API_FUNC_ATTRIBUTE void* sljit_malloc_exec(sljit_uw size)
119 {
120 #if !(defined SLJIT_SINGLE_THREADED && SLJIT_SINGLE_THREADED)
121 static pthread_mutex_t se_lock = PTHREAD_MUTEX_INITIALIZER;
122 #endif
123 static int se_protected = !SLJIT_PROT_WX;
124 sljit_uw* ptr;
125
126 if (SLJIT_UNLIKELY(se_protected < 0))
127 return NULL;
128
129 size += sizeof(sljit_uw);
130 ptr = (sljit_uw*)mmap(NULL, size, PROT_READ | PROT_WRITE | SLJIT_PROT_WX,
131 MAP_PRIVATE | MAP_ANON, -1, 0);
132
133 if (ptr == MAP_FAILED)
134 return NULL;
135
136 if (SLJIT_UNLIKELY(se_protected > 0)) {
137 SLJIT_SE_LOCK();
138 se_protected = check_se_protected(ptr, size);
139 SLJIT_SE_UNLOCK();
140 if (SLJIT_UNLIKELY(se_protected < 0)) {
141 munmap((void *)ptr, size);
142 return NULL;
143 }
144 }
145
146 *ptr++ = size;
147 return ptr;
148 }
149
150 #undef SLJIT_PROT_WX
151 #undef SLJIT_SE_UNLOCK
152 #undef SLJIT_SE_LOCK
153
sljit_free_exec(void * ptr)154 SLJIT_API_FUNC_ATTRIBUTE void sljit_free_exec(void* ptr)
155 {
156 sljit_uw *start_ptr = ((sljit_uw*)ptr) - 1;
157 munmap((void*)start_ptr, *start_ptr);
158 }
159
sljit_update_wx_flags(void * from,void * to,sljit_s32 enable_exec)160 static void sljit_update_wx_flags(void *from, void *to, sljit_s32 enable_exec)
161 {
162 sljit_uw page_mask = (sljit_uw)get_page_alignment();
163 sljit_uw start = (sljit_uw)from;
164 sljit_uw end = (sljit_uw)to;
165 int prot = PROT_READ | (enable_exec ? PROT_EXEC : PROT_WRITE);
166
167 SLJIT_ASSERT(start < end);
168
169 start &= ~page_mask;
170 end = (end + page_mask) & ~page_mask;
171
172 mprotect((void*)start, end - start, prot);
173 }
174
175 #else /* windows */
176
sljit_malloc_exec(sljit_uw size)177 SLJIT_API_FUNC_ATTRIBUTE void* sljit_malloc_exec(sljit_uw size)
178 {
179 sljit_uw *ptr;
180
181 size += sizeof(sljit_uw);
182 ptr = (sljit_uw*)VirtualAlloc(NULL, size,
183 MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
184
185 if (!ptr)
186 return NULL;
187
188 *ptr++ = size;
189
190 return ptr;
191 }
192
sljit_free_exec(void * ptr)193 SLJIT_API_FUNC_ATTRIBUTE void sljit_free_exec(void* ptr)
194 {
195 sljit_uw start = (sljit_uw)ptr - sizeof(sljit_uw);
196 #if defined(SLJIT_DEBUG) && SLJIT_DEBUG
197 sljit_uw page_mask = (sljit_uw)get_page_alignment();
198
199 SLJIT_ASSERT(!(start & page_mask));
200 #endif
201 VirtualFree((void*)start, 0, MEM_RELEASE);
202 }
203
sljit_update_wx_flags(void * from,void * to,sljit_s32 enable_exec)204 static void sljit_update_wx_flags(void *from, void *to, sljit_s32 enable_exec)
205 {
206 DWORD oldprot;
207 sljit_uw page_mask = (sljit_uw)get_page_alignment();
208 sljit_uw start = (sljit_uw)from;
209 sljit_uw end = (sljit_uw)to;
210 DWORD prot = enable_exec ? PAGE_EXECUTE : PAGE_READWRITE;
211
212 SLJIT_ASSERT(start < end);
213
214 start &= ~page_mask;
215 end = (end + page_mask) & ~page_mask;
216
217 VirtualProtect((void*)start, end - start, prot, &oldprot);
218 }
219
220 #endif /* !windows */
221
sljit_free_unused_memory_exec(void)222 SLJIT_API_FUNC_ATTRIBUTE void sljit_free_unused_memory_exec(void)
223 {
224 /* This allocator does not keep unused memory for future allocations. */
225 }
226