test-bdrv-drain: AIO_WAIT_WHILE() in job .commit/.abort
[qemu/ar7.git] / util / memfd.c
blobd248a53c3c0815bee3a5b2e2309ddcff51c10b2a
1 /*
2 * memfd.c
4 * Copyright (c) 2015 Red Hat, Inc.
6 * QEMU library functions on POSIX which are shared between QEMU and
7 * the QEMU tools.
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:
16 * The above copyright notice and this permission notice shall be included in
17 * all copies or substantial portions of the Software.
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.
28 #include "qemu/osdep.h"
30 #include "qapi/error.h"
31 #include "qemu/memfd.h"
32 #include "qemu/host-utils.h"
34 #if defined CONFIG_LINUX && !defined CONFIG_MEMFD
35 #include <sys/syscall.h>
36 #include <asm/unistd.h>
38 static int memfd_create(const char *name, unsigned int flags)
40 #ifdef __NR_memfd_create
41 return syscall(__NR_memfd_create, name, flags);
42 #else
43 return -1;
44 #endif
46 #endif
48 #ifndef MFD_CLOEXEC
49 #define MFD_CLOEXEC 0x0001U
50 #endif
52 #ifndef MFD_ALLOW_SEALING
53 #define MFD_ALLOW_SEALING 0x0002U
54 #endif
56 #ifndef MFD_HUGETLB
57 #define MFD_HUGETLB 0x0004U
58 #endif
60 #ifndef MFD_HUGE_SHIFT
61 #define MFD_HUGE_SHIFT 26
62 #endif
64 int qemu_memfd_create(const char *name, size_t size, bool hugetlb,
65 uint64_t hugetlbsize, unsigned int seals, Error **errp)
67 int htsize = hugetlbsize ? ctz64(hugetlbsize) : 0;
69 if (htsize && 1ULL << htsize != hugetlbsize) {
70 error_setg(errp, "Hugepage size must be a power of 2");
71 return -1;
74 htsize = htsize << MFD_HUGE_SHIFT;
76 #ifdef CONFIG_LINUX
77 int mfd = -1;
78 unsigned int flags = MFD_CLOEXEC;
80 if (seals) {
81 flags |= MFD_ALLOW_SEALING;
83 if (hugetlb) {
84 flags |= MFD_HUGETLB;
85 flags |= htsize;
87 mfd = memfd_create(name, flags);
88 if (mfd < 0) {
89 goto err;
92 if (ftruncate(mfd, size) == -1) {
93 goto err;
96 if (seals && fcntl(mfd, F_ADD_SEALS, seals) == -1) {
97 goto err;
100 return mfd;
102 err:
103 if (mfd >= 0) {
104 close(mfd);
106 #endif
107 error_setg_errno(errp, errno, "failed to create memfd");
108 return -1;
112 * This is a best-effort helper for shared memory allocation, with
113 * optional sealing. The helper will do his best to allocate using
114 * memfd with sealing, but may fallback on other methods without
115 * sealing.
117 void *qemu_memfd_alloc(const char *name, size_t size, unsigned int seals,
118 int *fd, Error **errp)
120 void *ptr;
121 int mfd = qemu_memfd_create(name, size, false, 0, seals, NULL);
123 /* some systems have memfd without sealing */
124 if (mfd == -1) {
125 mfd = qemu_memfd_create(name, size, false, 0, 0, NULL);
128 if (mfd == -1) {
129 const char *tmpdir = g_get_tmp_dir();
130 gchar *fname;
132 fname = g_strdup_printf("%s/memfd-XXXXXX", tmpdir);
133 mfd = mkstemp(fname);
134 unlink(fname);
135 g_free(fname);
137 if (mfd == -1 ||
138 ftruncate(mfd, size) == -1) {
139 goto err;
143 ptr = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, mfd, 0);
144 if (ptr == MAP_FAILED) {
145 goto err;
148 *fd = mfd;
149 return ptr;
151 err:
152 error_setg_errno(errp, errno, "failed to allocate shared memory");
153 if (mfd >= 0) {
154 close(mfd);
156 return NULL;
159 void qemu_memfd_free(void *ptr, size_t size, int fd)
161 if (ptr) {
162 munmap(ptr, size);
165 if (fd != -1) {
166 close(fd);
170 enum {
171 MEMFD_KO,
172 MEMFD_OK,
173 MEMFD_TODO
177 * qemu_memfd_alloc_check():
179 * Check if qemu_memfd_alloc() can allocate, including using a
180 * fallback implementation when host doesn't support memfd.
182 bool qemu_memfd_alloc_check(void)
184 static int memfd_check = MEMFD_TODO;
186 if (memfd_check == MEMFD_TODO) {
187 int fd;
188 void *ptr;
190 ptr = qemu_memfd_alloc("test", 4096, 0, &fd, NULL);
191 memfd_check = ptr ? MEMFD_OK : MEMFD_KO;
192 qemu_memfd_free(ptr, 4096, fd);
195 return memfd_check == MEMFD_OK;
199 * qemu_memfd_check():
201 * Check if host supports memfd.
203 bool qemu_memfd_check(void)
205 #ifdef CONFIG_LINUX
206 static int memfd_check = MEMFD_TODO;
208 if (memfd_check == MEMFD_TODO) {
209 int mfd = memfd_create("test", 0);
210 if (mfd >= 0) {
211 memfd_check = MEMFD_OK;
212 close(mfd);
213 } else {
214 memfd_check = MEMFD_KO;
218 return memfd_check == MEMFD_OK;
219 #else
220 return false;
221 #endif