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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 | ||
0f2956f9 | 30 | #include "qapi/error.h" |
f04cf923 MAL |
31 | #include "qemu/memfd.h" |
32 | ||
75e5b70e | 33 | #if defined CONFIG_LINUX && !defined CONFIG_MEMFD |
f04cf923 MAL |
34 | #include <sys/syscall.h> |
35 | #include <asm/unistd.h> | |
36 | ||
d3592199 | 37 | static int memfd_create(const char *name, unsigned int flags) |
f04cf923 MAL |
38 | { |
39 | #ifdef __NR_memfd_create | |
40 | return syscall(__NR_memfd_create, name, flags); | |
41 | #else | |
42 | return -1; | |
43 | #endif | |
44 | } | |
45 | #endif | |
46 | ||
47 | #ifndef MFD_CLOEXEC | |
48 | #define MFD_CLOEXEC 0x0001U | |
49 | #endif | |
50 | ||
51 | #ifndef MFD_ALLOW_SEALING | |
52 | #define MFD_ALLOW_SEALING 0x0002U | |
53 | #endif | |
d3592199 | 54 | |
0f2956f9 MAL |
55 | int qemu_memfd_create(const char *name, size_t size, |
56 | unsigned int seals, Error **errp) | |
dcff1035 | 57 | { |
dcff1035 | 58 | #ifdef CONFIG_LINUX |
0f2956f9 | 59 | int mfd = -1; |
dcff1035 MAL |
60 | unsigned int flags = MFD_CLOEXEC; |
61 | ||
62 | if (seals) { | |
63 | flags |= MFD_ALLOW_SEALING; | |
64 | } | |
65 | ||
66 | mfd = memfd_create(name, flags); | |
67 | if (mfd < 0) { | |
0f2956f9 | 68 | goto err; |
dcff1035 MAL |
69 | } |
70 | ||
71 | if (ftruncate(mfd, size) == -1) { | |
0f2956f9 | 72 | goto err; |
dcff1035 MAL |
73 | } |
74 | ||
75 | if (seals && fcntl(mfd, F_ADD_SEALS, seals) == -1) { | |
0f2956f9 | 76 | goto err; |
dcff1035 | 77 | } |
dcff1035 MAL |
78 | |
79 | return mfd; | |
0f2956f9 MAL |
80 | |
81 | err: | |
82 | if (mfd >= 0) { | |
83 | close(mfd); | |
84 | } | |
85 | #endif | |
86 | error_setg_errno(errp, errno, "failed to create memfd"); | |
87 | return -1; | |
dcff1035 MAL |
88 | } |
89 | ||
d3592199 MAL |
90 | /* |
91 | * This is a best-effort helper for shared memory allocation, with | |
92 | * optional sealing. The helper will do his best to allocate using | |
93 | * memfd with sealing, but may fallback on other methods without | |
94 | * sealing. | |
95 | */ | |
96 | void *qemu_memfd_alloc(const char *name, size_t size, unsigned int seals, | |
0f2956f9 | 97 | int *fd, Error **errp) |
d3592199 MAL |
98 | { |
99 | void *ptr; | |
0f2956f9 | 100 | int mfd = qemu_memfd_create(name, size, seals, NULL); |
d3592199 | 101 | |
dcff1035 | 102 | /* some systems have memfd without sealing */ |
d3592199 | 103 | if (mfd == -1) { |
0f2956f9 | 104 | mfd = qemu_memfd_create(name, size, 0, NULL); |
d3592199 | 105 | } |
d3592199 | 106 | |
dcff1035 | 107 | if (mfd == -1) { |
35f9b6ef MAL |
108 | const char *tmpdir = g_get_tmp_dir(); |
109 | gchar *fname; | |
110 | ||
111 | fname = g_strdup_printf("%s/memfd-XXXXXX", tmpdir); | |
112 | mfd = mkstemp(fname); | |
113 | unlink(fname); | |
114 | g_free(fname); | |
115 | ||
0f2956f9 MAL |
116 | if (mfd == -1 || |
117 | ftruncate(mfd, size) == -1) { | |
118 | goto err; | |
35f9b6ef | 119 | } |
d3592199 MAL |
120 | } |
121 | ||
122 | ptr = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, mfd, 0); | |
123 | if (ptr == MAP_FAILED) { | |
0f2956f9 | 124 | goto err; |
d3592199 MAL |
125 | } |
126 | ||
127 | *fd = mfd; | |
128 | return ptr; | |
0f2956f9 MAL |
129 | |
130 | err: | |
131 | error_setg_errno(errp, errno, "failed to allocate shared memory"); | |
132 | if (mfd >= 0) { | |
133 | close(mfd); | |
134 | } | |
135 | return NULL; | |
d3592199 MAL |
136 | } |
137 | ||
138 | void qemu_memfd_free(void *ptr, size_t size, int fd) | |
139 | { | |
140 | if (ptr) { | |
141 | munmap(ptr, size); | |
142 | } | |
143 | ||
144 | if (fd != -1) { | |
145 | close(fd); | |
146 | } | |
147 | } | |
31190ed7 MAL |
148 | |
149 | enum { | |
150 | MEMFD_KO, | |
151 | MEMFD_OK, | |
152 | MEMFD_TODO | |
153 | }; | |
154 | ||
155 | bool qemu_memfd_check(void) | |
156 | { | |
157 | static int memfd_check = MEMFD_TODO; | |
158 | ||
159 | if (memfd_check == MEMFD_TODO) { | |
160 | int fd; | |
161 | void *ptr; | |
162 | ||
0f2956f9 | 163 | ptr = qemu_memfd_alloc("test", 4096, 0, &fd, NULL); |
31190ed7 MAL |
164 | memfd_check = ptr ? MEMFD_OK : MEMFD_KO; |
165 | qemu_memfd_free(ptr, 4096, fd); | |
166 | } | |
167 | ||
168 | return memfd_check == MEMFD_OK; | |
169 | } |