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f04cf923 MAL |
1 | /* |
2 | * memfd.c | |
3 | * | |
4 | * Copyright (c) 2015 Red Hat, Inc. | |
5 | * | |
6 | * QEMU library functions on POSIX which are shared between QEMU and | |
7 | * the QEMU tools. | |
8 | * | |
9 | * Permission is hereby granted, free of charge, to any person obtaining a copy | |
10 | * of this software and associated documentation files (the "Software"), to deal | |
11 | * in the Software without restriction, including without limitation the rights | |
12 | * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | |
13 | * copies of the Software, and to permit persons to whom the Software is | |
14 | * furnished to do so, subject to the following conditions: | |
15 | * | |
16 | * The above copyright notice and this permission notice shall be included in | |
17 | * all copies or substantial portions of the Software. | |
18 | * | |
19 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | |
20 | * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | |
21 | * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL | |
22 | * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | |
23 | * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | |
24 | * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN | |
25 | * THE SOFTWARE. | |
26 | */ | |
27 | ||
28 | #include "qemu/osdep.h" | |
29 | ||
d3592199 MAL |
30 | #include <glib/gprintf.h> |
31 | ||
32 | #include <sys/mman.h> | |
33 | ||
f04cf923 MAL |
34 | #include "qemu/memfd.h" |
35 | ||
36 | #ifdef CONFIG_MEMFD | |
37 | #include <sys/memfd.h> | |
38 | #elif defined CONFIG_LINUX | |
39 | #include <sys/syscall.h> | |
40 | #include <asm/unistd.h> | |
41 | ||
d3592199 | 42 | static int memfd_create(const char *name, unsigned int flags) |
f04cf923 MAL |
43 | { |
44 | #ifdef __NR_memfd_create | |
45 | return syscall(__NR_memfd_create, name, flags); | |
46 | #else | |
47 | return -1; | |
48 | #endif | |
49 | } | |
50 | #endif | |
51 | ||
52 | #ifndef MFD_CLOEXEC | |
53 | #define MFD_CLOEXEC 0x0001U | |
54 | #endif | |
55 | ||
56 | #ifndef MFD_ALLOW_SEALING | |
57 | #define MFD_ALLOW_SEALING 0x0002U | |
58 | #endif | |
d3592199 MAL |
59 | |
60 | /* | |
61 | * This is a best-effort helper for shared memory allocation, with | |
62 | * optional sealing. The helper will do his best to allocate using | |
63 | * memfd with sealing, but may fallback on other methods without | |
64 | * sealing. | |
65 | */ | |
66 | void *qemu_memfd_alloc(const char *name, size_t size, unsigned int seals, | |
67 | int *fd) | |
68 | { | |
69 | void *ptr; | |
70 | int mfd = -1; | |
71 | ||
72 | *fd = -1; | |
73 | ||
74 | #ifdef CONFIG_LINUX | |
75 | if (seals) { | |
76 | mfd = memfd_create(name, MFD_ALLOW_SEALING | MFD_CLOEXEC); | |
77 | } | |
78 | ||
79 | if (mfd == -1) { | |
80 | /* some systems have memfd without sealing */ | |
81 | mfd = memfd_create(name, MFD_CLOEXEC); | |
82 | seals = 0; | |
83 | } | |
84 | #endif | |
85 | ||
86 | if (mfd != -1) { | |
87 | if (ftruncate(mfd, size) == -1) { | |
88 | perror("ftruncate"); | |
89 | close(mfd); | |
90 | return NULL; | |
91 | } | |
92 | ||
93 | if (seals && fcntl(mfd, F_ADD_SEALS, seals) == -1) { | |
94 | perror("fcntl"); | |
95 | close(mfd); | |
96 | return NULL; | |
97 | } | |
98 | } else { | |
35f9b6ef MAL |
99 | const char *tmpdir = g_get_tmp_dir(); |
100 | gchar *fname; | |
101 | ||
102 | fname = g_strdup_printf("%s/memfd-XXXXXX", tmpdir); | |
103 | mfd = mkstemp(fname); | |
104 | unlink(fname); | |
105 | g_free(fname); | |
106 | ||
107 | if (mfd == -1) { | |
108 | perror("mkstemp"); | |
109 | return NULL; | |
110 | } | |
111 | ||
112 | if (ftruncate(mfd, size) == -1) { | |
113 | perror("ftruncate"); | |
114 | close(mfd); | |
115 | return NULL; | |
116 | } | |
d3592199 MAL |
117 | } |
118 | ||
119 | ptr = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, mfd, 0); | |
120 | if (ptr == MAP_FAILED) { | |
121 | perror("mmap"); | |
122 | close(mfd); | |
123 | return NULL; | |
124 | } | |
125 | ||
126 | *fd = mfd; | |
127 | return ptr; | |
128 | } | |
129 | ||
130 | void qemu_memfd_free(void *ptr, size_t size, int fd) | |
131 | { | |
132 | if (ptr) { | |
133 | munmap(ptr, size); | |
134 | } | |
135 | ||
136 | if (fd != -1) { | |
137 | close(fd); | |
138 | } | |
139 | } | |
31190ed7 MAL |
140 | |
141 | enum { | |
142 | MEMFD_KO, | |
143 | MEMFD_OK, | |
144 | MEMFD_TODO | |
145 | }; | |
146 | ||
147 | bool qemu_memfd_check(void) | |
148 | { | |
149 | static int memfd_check = MEMFD_TODO; | |
150 | ||
151 | if (memfd_check == MEMFD_TODO) { | |
152 | int fd; | |
153 | void *ptr; | |
154 | ||
155 | ptr = qemu_memfd_alloc("test", 4096, 0, &fd); | |
156 | memfd_check = ptr ? MEMFD_OK : MEMFD_KO; | |
157 | qemu_memfd_free(ptr, 4096, fd); | |
158 | } | |
159 | ||
160 | return memfd_check == MEMFD_OK; | |
161 | } |