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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
38static 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 return -1;
44#endif
45}
46#endif
47
48#ifndef MFD_CLOEXEC
49#define MFD_CLOEXEC 0x0001U
50#endif
51
52#ifndef MFD_ALLOW_SEALING
53#define MFD_ALLOW_SEALING 0x0002U
54#endif
55
56#ifndef MFD_HUGETLB
57#define MFD_HUGETLB 0x0004U
58#endif
59
60#ifndef MFD_HUGE_SHIFT
61#define MFD_HUGE_SHIFT 26
62#endif
63
64int qemu_memfd_create(const char *name, size_t size, bool hugetlb,
65 uint64_t hugetlbsize, unsigned int seals, Error **errp)
66{
67 int htsize = hugetlbsize ? ctz64(hugetlbsize) : 0;
68
69 if (htsize && 1 << htsize != hugetlbsize) {
70 error_setg(errp, "Hugepage size must be a power of 2");
71 return -1;
72 }
73
74 htsize = htsize << MFD_HUGE_SHIFT;
75
76#ifdef CONFIG_LINUX
77 int mfd = -1;
78 unsigned int flags = MFD_CLOEXEC;
79
80 if (seals) {
81 flags |= MFD_ALLOW_SEALING;
82 }
83 if (hugetlb) {
84 flags |= MFD_HUGETLB;
85 flags |= htsize;
86 }
87 mfd = memfd_create(name, flags);
88 if (mfd < 0) {
89 goto err;
90 }
91
92 if (ftruncate(mfd, size) == -1) {
93 goto err;
94 }
95
96 if (seals && fcntl(mfd, F_ADD_SEALS, seals) == -1) {
97 goto err;
98 }
99
100 return mfd;
101
102err:
103 if (mfd >= 0) {
104 close(mfd);
105 }
106#endif
107 error_setg_errno(errp, errno, "failed to create memfd");
108 return -1;
109}
110
111
112
113
114
115
116
117void *qemu_memfd_alloc(const char *name, size_t size, unsigned int seals,
118 int *fd, Error **errp)
119{
120 void *ptr;
121 int mfd = qemu_memfd_create(name, size, false, 0, seals, NULL);
122
123
124 if (mfd == -1) {
125 mfd = qemu_memfd_create(name, size, false, 0, 0, NULL);
126 }
127
128 if (mfd == -1) {
129 const char *tmpdir = g_get_tmp_dir();
130 gchar *fname;
131
132 fname = g_strdup_printf("%s/memfd-XXXXXX", tmpdir);
133 mfd = mkstemp(fname);
134 unlink(fname);
135 g_free(fname);
136
137 if (mfd == -1 ||
138 ftruncate(mfd, size) == -1) {
139 goto err;
140 }
141 }
142
143 ptr = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, mfd, 0);
144 if (ptr == MAP_FAILED) {
145 goto err;
146 }
147
148 *fd = mfd;
149 return ptr;
150
151err:
152 error_setg_errno(errp, errno, "failed to allocate shared memory");
153 if (mfd >= 0) {
154 close(mfd);
155 }
156 return NULL;
157}
158
159void qemu_memfd_free(void *ptr, size_t size, int fd)
160{
161 if (ptr) {
162 munmap(ptr, size);
163 }
164
165 if (fd != -1) {
166 close(fd);
167 }
168}
169
170enum {
171 MEMFD_KO,
172 MEMFD_OK,
173 MEMFD_TODO
174};
175
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179
180
181
182bool qemu_memfd_alloc_check(void)
183{
184 static int memfd_check = MEMFD_TODO;
185
186 if (memfd_check == MEMFD_TODO) {
187 int fd;
188 void *ptr;
189
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);
193 }
194
195 return memfd_check == MEMFD_OK;
196}
197
198
199
200
201
202
203bool qemu_memfd_check(void)
204{
205#ifdef CONFIG_LINUX
206 static int memfd_check = MEMFD_TODO;
207
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;
215 }
216 }
217
218 return memfd_check == MEMFD_OK;
219#else
220 return false;
221#endif
222}
223