4 * Copyright (c) 2015 Red Hat, Inc.
6 * QEMU library functions on POSIX which are shared between QEMU and
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
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
);
49 #define MFD_CLOEXEC 0x0001U
52 #ifndef MFD_ALLOW_SEALING
53 #define MFD_ALLOW_SEALING 0x0002U
57 #define MFD_HUGETLB 0x0004U
60 #ifndef MFD_HUGE_SHIFT
61 #define MFD_HUGE_SHIFT 26
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
&& 1 << htsize
!= hugetlbsize
) {
70 error_setg(errp
, "Hugepage size must be a power of 2");
74 htsize
= htsize
<< MFD_HUGE_SHIFT
;
78 unsigned int flags
= MFD_CLOEXEC
;
81 flags
|= MFD_ALLOW_SEALING
;
87 mfd
= memfd_create(name
, flags
);
92 if (ftruncate(mfd
, size
) == -1) {
96 if (seals
&& fcntl(mfd
, F_ADD_SEALS
, seals
) == -1) {
107 error_setg_errno(errp
, errno
, "failed to create memfd");
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
117 void *qemu_memfd_alloc(const char *name
, size_t size
, unsigned int seals
,
118 int *fd
, Error
**errp
)
121 int mfd
= qemu_memfd_create(name
, size
, false, 0, seals
, NULL
);
123 /* some systems have memfd without sealing */
125 mfd
= qemu_memfd_create(name
, size
, false, 0, 0, NULL
);
129 const char *tmpdir
= g_get_tmp_dir();
132 fname
= g_strdup_printf("%s/memfd-XXXXXX", tmpdir
);
133 mfd
= mkstemp(fname
);
138 ftruncate(mfd
, size
) == -1) {
143 ptr
= mmap(0, size
, PROT_READ
| PROT_WRITE
, MAP_SHARED
, mfd
, 0);
144 if (ptr
== MAP_FAILED
) {
152 error_setg_errno(errp
, errno
, "failed to allocate shared memory");
159 void qemu_memfd_free(void *ptr
, size_t size
, int fd
)
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
) {
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)
206 static int memfd_check
= MEMFD_TODO
;
208 if (memfd_check
== MEMFD_TODO
) {
209 int mfd
= memfd_create("test", 0);
211 memfd_check
= MEMFD_OK
;
214 memfd_check
= MEMFD_KO
;
218 return memfd_check
== MEMFD_OK
;