Merge remote-tracking branch 'remotes/pmaydell/tags/pull-target-arm-20200406' into...
[qemu.git] / util / memfd.c
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
30 #include "qapi/error.h"
31 #include "qemu/memfd.h"
32 #include "qemu/host-utils.h"
33
34 #if defined CONFIG_LINUX && !defined CONFIG_MEMFD
35 #include <sys/syscall.h>
36 #include <asm/unistd.h>
37
38 int memfd_create(const char *name, unsigned int flags)
39 {
40 #ifdef __NR_memfd_create
41 return syscall(__NR_memfd_create, name, flags);
42 #else
43 errno = ENOSYS;
44 return -1;
45 #endif
46 }
47 #endif
48
49 int qemu_memfd_create(const char *name, size_t size, bool hugetlb,
50 uint64_t hugetlbsize, unsigned int seals, Error **errp)
51 {
52 int htsize = hugetlbsize ? ctz64(hugetlbsize) : 0;
53
54 if (htsize && 1ULL << htsize != hugetlbsize) {
55 error_setg(errp, "Hugepage size must be a power of 2");
56 return -1;
57 }
58
59 htsize = htsize << MFD_HUGE_SHIFT;
60
61 #ifdef CONFIG_LINUX
62 int mfd = -1;
63 unsigned int flags = MFD_CLOEXEC;
64
65 if (seals) {
66 flags |= MFD_ALLOW_SEALING;
67 }
68 if (hugetlb) {
69 flags |= MFD_HUGETLB;
70 flags |= htsize;
71 }
72 mfd = memfd_create(name, flags);
73 if (mfd < 0) {
74 error_setg_errno(errp, errno,
75 "failed to create memfd with flags 0x%x", flags);
76 goto err;
77 }
78
79 if (ftruncate(mfd, size) == -1) {
80 error_setg_errno(errp, errno, "failed to resize memfd to %zu", size);
81 goto err;
82 }
83
84 if (seals && fcntl(mfd, F_ADD_SEALS, seals) == -1) {
85 error_setg_errno(errp, errno, "failed to add seals 0x%x", seals);
86 goto err;
87 }
88
89 return mfd;
90
91 err:
92 if (mfd >= 0) {
93 close(mfd);
94 }
95 #else
96 error_setg_errno(errp, ENOSYS, "failed to create memfd");
97 #endif
98 return -1;
99 }
100
101 /*
102 * This is a best-effort helper for shared memory allocation, with
103 * optional sealing. The helper will do his best to allocate using
104 * memfd with sealing, but may fallback on other methods without
105 * sealing.
106 */
107 void *qemu_memfd_alloc(const char *name, size_t size, unsigned int seals,
108 int *fd, Error **errp)
109 {
110 void *ptr;
111 int mfd = qemu_memfd_create(name, size, false, 0, seals, NULL);
112
113 /* some systems have memfd without sealing */
114 if (mfd == -1) {
115 mfd = qemu_memfd_create(name, size, false, 0, 0, NULL);
116 }
117
118 if (mfd == -1) {
119 const char *tmpdir = g_get_tmp_dir();
120 gchar *fname;
121
122 fname = g_strdup_printf("%s/memfd-XXXXXX", tmpdir);
123 mfd = mkstemp(fname);
124 unlink(fname);
125 g_free(fname);
126
127 if (mfd == -1 ||
128 ftruncate(mfd, size) == -1) {
129 goto err;
130 }
131 }
132
133 ptr = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, mfd, 0);
134 if (ptr == MAP_FAILED) {
135 goto err;
136 }
137
138 *fd = mfd;
139 return ptr;
140
141 err:
142 error_setg_errno(errp, errno, "failed to allocate shared memory");
143 if (mfd >= 0) {
144 close(mfd);
145 }
146 return NULL;
147 }
148
149 void qemu_memfd_free(void *ptr, size_t size, int fd)
150 {
151 if (ptr) {
152 munmap(ptr, size);
153 }
154
155 if (fd != -1) {
156 close(fd);
157 }
158 }
159
160 enum {
161 MEMFD_KO,
162 MEMFD_OK,
163 MEMFD_TODO
164 };
165
166 /**
167 * qemu_memfd_alloc_check():
168 *
169 * Check if qemu_memfd_alloc() can allocate, including using a
170 * fallback implementation when host doesn't support memfd.
171 */
172 bool qemu_memfd_alloc_check(void)
173 {
174 static int memfd_check = MEMFD_TODO;
175
176 if (memfd_check == MEMFD_TODO) {
177 int fd;
178 void *ptr;
179
180 fd = -1;
181 ptr = qemu_memfd_alloc("test", 4096, 0, &fd, NULL);
182 memfd_check = ptr ? MEMFD_OK : MEMFD_KO;
183 qemu_memfd_free(ptr, 4096, fd);
184 }
185
186 return memfd_check == MEMFD_OK;
187 }
188
189 /**
190 * qemu_memfd_check():
191 *
192 * Check if host supports memfd.
193 */
194 bool qemu_memfd_check(unsigned int flags)
195 {
196 #ifdef CONFIG_LINUX
197 int mfd = memfd_create("test", flags | MFD_CLOEXEC);
198
199 if (mfd >= 0) {
200 close(mfd);
201 return true;
202 }
203 #endif
204
205 return false;
206 }