1 /*
2 * Mesa 3-D graphics library
3 *
4 * Copyright (C) 1999-2005 Brian Paul All Rights Reserved.
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining a
7 * copy of this software and associated documentation files (the "Software"),
8 * to deal in the Software without restriction, including without limitation
9 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
10 * and/or sell copies of the Software, and to permit persons to whom the
11 * Software is furnished to do so, subject to the following conditions:
12 *
13 * The above copyright notice and this permission notice shall be included
14 * in all copies or substantial portions of the Software.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
17 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
19 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
20 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
21 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
22 * OTHER DEALINGS IN THE SOFTWARE.
23 */
24
25
26 /**
27 * \file glapi_execmem.c
28 *
29 * Function for allocating executable memory for dispatch stubs.
30 *
31 * Copied from main/execmem.c and simplified for dispatch stubs.
32 */
33
34
35 #include "c11/threads.h"
36 #include "u_execmem.h"
37
38
39 #define EXEC_MAP_SIZE (4*1024)
40
41 static mtx_t exec_mutex = _MTX_INITIALIZER_NP;
42
43 static unsigned int head = 0;
44
45 static unsigned char *exec_mem = (unsigned char *)0;
46
47
48 #if defined(__linux__) || defined(__OpenBSD__) || defined(__NetBSD__) || defined(__sun) || defined(__HAIKU__)
49
50 #include <unistd.h>
51 #include <sys/mman.h>
52
53 #ifdef MESA_SELINUX
54 #include <selinux/selinux.h>
55 #endif
56
57
58 #ifndef MAP_ANONYMOUS
59 #define MAP_ANONYMOUS MAP_ANON
60 #endif
61
62
63 /*
64 * Dispatch stubs are of fixed size and never freed. Thus, we do not need to
65 * overlay a heap, we just mmap a page and manage through an index.
66 */
67
68 static int
init_map(void)69 init_map(void)
70 {
71 #ifdef MESA_SELINUX
72 if (is_selinux_enabled()) {
73 if (!security_get_boolean_active("allow_execmem") ||
74 !security_get_boolean_pending("allow_execmem"))
75 return 0;
76 }
77 #endif
78
79 if (!exec_mem)
80 exec_mem = mmap(NULL, EXEC_MAP_SIZE, PROT_EXEC | PROT_READ | PROT_WRITE,
81 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
82
83 return (exec_mem != MAP_FAILED);
84 }
85
86
87 #elif defined(_WIN32)
88
89 #include <windows.h>
90
91
92 /*
93 * Avoid Data Execution Prevention.
94 */
95
96 static int
init_map(void)97 init_map(void)
98 {
99 exec_mem = VirtualAlloc(NULL, EXEC_MAP_SIZE, MEM_COMMIT, PAGE_EXECUTE_READWRITE);
100
101 return (exec_mem != NULL);
102 }
103
104
105 #else
106
107 #include <stdlib.h>
108
109 static int
init_map(void)110 init_map(void)
111 {
112 exec_mem = malloc(EXEC_MAP_SIZE);
113
114 return (exec_mem != NULL);
115 }
116
117
118 #endif
119
120 void *
u_execmem_alloc(unsigned int size)121 u_execmem_alloc(unsigned int size)
122 {
123 #ifndef MESA_EXECMEM
124 (void)size;
125 return NULL;
126 #else
127 void *addr = NULL;
128
129 mtx_lock(&exec_mutex);
130
131 if (!init_map())
132 goto bail;
133
134 /* free space check, assumes no integer overflow */
135 if (head + size > EXEC_MAP_SIZE)
136 goto bail;
137
138 /* allocation, assumes proper addr and size alignement */
139 addr = exec_mem + head;
140 head += size;
141
142 bail:
143 mtx_unlock(&exec_mutex);
144
145 return addr;
146 #endif /* MESA_EXECMEM */
147 }
148
149
150