1f04cf923SMarc-André Lureau /* 2f04cf923SMarc-André Lureau * memfd.c 3f04cf923SMarc-André Lureau * 4f04cf923SMarc-André Lureau * Copyright (c) 2015 Red Hat, Inc. 5f04cf923SMarc-André Lureau * 6f04cf923SMarc-André Lureau * QEMU library functions on POSIX which are shared between QEMU and 7f04cf923SMarc-André Lureau * the QEMU tools. 8f04cf923SMarc-André Lureau * 9f04cf923SMarc-André Lureau * Permission is hereby granted, free of charge, to any person obtaining a copy 10f04cf923SMarc-André Lureau * of this software and associated documentation files (the "Software"), to deal 11f04cf923SMarc-André Lureau * in the Software without restriction, including without limitation the rights 12f04cf923SMarc-André Lureau * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 13f04cf923SMarc-André Lureau * copies of the Software, and to permit persons to whom the Software is 14f04cf923SMarc-André Lureau * furnished to do so, subject to the following conditions: 15f04cf923SMarc-André Lureau * 16f04cf923SMarc-André Lureau * The above copyright notice and this permission notice shall be included in 17f04cf923SMarc-André Lureau * all copies or substantial portions of the Software. 18f04cf923SMarc-André Lureau * 19f04cf923SMarc-André Lureau * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 20f04cf923SMarc-André Lureau * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 21f04cf923SMarc-André Lureau * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 22f04cf923SMarc-André Lureau * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 23f04cf923SMarc-André Lureau * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 24f04cf923SMarc-André Lureau * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN 25f04cf923SMarc-André Lureau * THE SOFTWARE. 26f04cf923SMarc-André Lureau */ 27f04cf923SMarc-André Lureau 28f04cf923SMarc-André Lureau #include "qemu/osdep.h" 29f04cf923SMarc-André Lureau 300f2956f9SMarc-André Lureau #include "qapi/error.h" 31f04cf923SMarc-André Lureau #include "qemu/memfd.h" 322ef8c0c9SMarc-André Lureau #include "qemu/host-utils.h" 33f04cf923SMarc-André Lureau 3475e5b70eSPaolo Bonzini #if defined CONFIG_LINUX && !defined CONFIG_MEMFD 35f04cf923SMarc-André Lureau #include <sys/syscall.h> 36f04cf923SMarc-André Lureau #include <asm/unistd.h> 37f04cf923SMarc-André Lureau 38d3592199SMarc-André Lureau static int memfd_create(const char *name, unsigned int flags) 39f04cf923SMarc-André Lureau { 40f04cf923SMarc-André Lureau #ifdef __NR_memfd_create 41f04cf923SMarc-André Lureau return syscall(__NR_memfd_create, name, flags); 42f04cf923SMarc-André Lureau #else 43f04cf923SMarc-André Lureau return -1; 44f04cf923SMarc-André Lureau #endif 45f04cf923SMarc-André Lureau } 46f04cf923SMarc-André Lureau #endif 47f04cf923SMarc-André Lureau 48f04cf923SMarc-André Lureau #ifndef MFD_CLOEXEC 49f04cf923SMarc-André Lureau #define MFD_CLOEXEC 0x0001U 50f04cf923SMarc-André Lureau #endif 51f04cf923SMarc-André Lureau 52f04cf923SMarc-André Lureau #ifndef MFD_ALLOW_SEALING 53f04cf923SMarc-André Lureau #define MFD_ALLOW_SEALING 0x0002U 54f04cf923SMarc-André Lureau #endif 55d3592199SMarc-André Lureau 56c5b2a9e0SMarc-André Lureau #ifndef MFD_HUGETLB 57c5b2a9e0SMarc-André Lureau #define MFD_HUGETLB 0x0004U 58c5b2a9e0SMarc-André Lureau #endif 59c5b2a9e0SMarc-André Lureau 602ef8c0c9SMarc-André Lureau #ifndef MFD_HUGE_SHIFT 612ef8c0c9SMarc-André Lureau #define MFD_HUGE_SHIFT 26 622ef8c0c9SMarc-André Lureau #endif 632ef8c0c9SMarc-André Lureau 64c5b2a9e0SMarc-André Lureau int qemu_memfd_create(const char *name, size_t size, bool hugetlb, 652ef8c0c9SMarc-André Lureau uint64_t hugetlbsize, unsigned int seals, Error **errp) 66dcff1035SMarc-André Lureau { 672ef8c0c9SMarc-André Lureau int htsize = hugetlbsize ? ctz64(hugetlbsize) : 0; 682ef8c0c9SMarc-André Lureau 69*4f938cbdSPeter Maydell if (htsize && 1ULL << htsize != hugetlbsize) { 702ef8c0c9SMarc-André Lureau error_setg(errp, "Hugepage size must be a power of 2"); 712ef8c0c9SMarc-André Lureau return -1; 722ef8c0c9SMarc-André Lureau } 732ef8c0c9SMarc-André Lureau 742ef8c0c9SMarc-André Lureau htsize = htsize << MFD_HUGE_SHIFT; 752ef8c0c9SMarc-André Lureau 76dcff1035SMarc-André Lureau #ifdef CONFIG_LINUX 770f2956f9SMarc-André Lureau int mfd = -1; 78dcff1035SMarc-André Lureau unsigned int flags = MFD_CLOEXEC; 79dcff1035SMarc-André Lureau 80dcff1035SMarc-André Lureau if (seals) { 81dcff1035SMarc-André Lureau flags |= MFD_ALLOW_SEALING; 82dcff1035SMarc-André Lureau } 83c5b2a9e0SMarc-André Lureau if (hugetlb) { 84c5b2a9e0SMarc-André Lureau flags |= MFD_HUGETLB; 852ef8c0c9SMarc-André Lureau flags |= htsize; 86c5b2a9e0SMarc-André Lureau } 87dcff1035SMarc-André Lureau mfd = memfd_create(name, flags); 88dcff1035SMarc-André Lureau if (mfd < 0) { 890f2956f9SMarc-André Lureau goto err; 90dcff1035SMarc-André Lureau } 91dcff1035SMarc-André Lureau 92dcff1035SMarc-André Lureau if (ftruncate(mfd, size) == -1) { 930f2956f9SMarc-André Lureau goto err; 94dcff1035SMarc-André Lureau } 95dcff1035SMarc-André Lureau 96dcff1035SMarc-André Lureau if (seals && fcntl(mfd, F_ADD_SEALS, seals) == -1) { 970f2956f9SMarc-André Lureau goto err; 98dcff1035SMarc-André Lureau } 99dcff1035SMarc-André Lureau 100dcff1035SMarc-André Lureau return mfd; 1010f2956f9SMarc-André Lureau 1020f2956f9SMarc-André Lureau err: 1030f2956f9SMarc-André Lureau if (mfd >= 0) { 1040f2956f9SMarc-André Lureau close(mfd); 1050f2956f9SMarc-André Lureau } 1060f2956f9SMarc-André Lureau #endif 1070f2956f9SMarc-André Lureau error_setg_errno(errp, errno, "failed to create memfd"); 1080f2956f9SMarc-André Lureau return -1; 109dcff1035SMarc-André Lureau } 110dcff1035SMarc-André Lureau 111d3592199SMarc-André Lureau /* 112d3592199SMarc-André Lureau * This is a best-effort helper for shared memory allocation, with 113d3592199SMarc-André Lureau * optional sealing. The helper will do his best to allocate using 114d3592199SMarc-André Lureau * memfd with sealing, but may fallback on other methods without 115d3592199SMarc-André Lureau * sealing. 116d3592199SMarc-André Lureau */ 117d3592199SMarc-André Lureau void *qemu_memfd_alloc(const char *name, size_t size, unsigned int seals, 1180f2956f9SMarc-André Lureau int *fd, Error **errp) 119d3592199SMarc-André Lureau { 120d3592199SMarc-André Lureau void *ptr; 1212ef8c0c9SMarc-André Lureau int mfd = qemu_memfd_create(name, size, false, 0, seals, NULL); 122d3592199SMarc-André Lureau 123dcff1035SMarc-André Lureau /* some systems have memfd without sealing */ 124dcff1035SMarc-André Lureau if (mfd == -1) { 1252ef8c0c9SMarc-André Lureau mfd = qemu_memfd_create(name, size, false, 0, 0, NULL); 126d3592199SMarc-André Lureau } 127d3592199SMarc-André Lureau 128d3592199SMarc-André Lureau if (mfd == -1) { 12935f9b6efSMarc-André Lureau const char *tmpdir = g_get_tmp_dir(); 13035f9b6efSMarc-André Lureau gchar *fname; 13135f9b6efSMarc-André Lureau 13235f9b6efSMarc-André Lureau fname = g_strdup_printf("%s/memfd-XXXXXX", tmpdir); 13335f9b6efSMarc-André Lureau mfd = mkstemp(fname); 13435f9b6efSMarc-André Lureau unlink(fname); 13535f9b6efSMarc-André Lureau g_free(fname); 13635f9b6efSMarc-André Lureau 1370f2956f9SMarc-André Lureau if (mfd == -1 || 1380f2956f9SMarc-André Lureau ftruncate(mfd, size) == -1) { 1390f2956f9SMarc-André Lureau goto err; 14035f9b6efSMarc-André Lureau } 14135f9b6efSMarc-André Lureau } 14235f9b6efSMarc-André Lureau 143d3592199SMarc-André Lureau ptr = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, mfd, 0); 144d3592199SMarc-André Lureau if (ptr == MAP_FAILED) { 1450f2956f9SMarc-André Lureau goto err; 146d3592199SMarc-André Lureau } 147d3592199SMarc-André Lureau 148d3592199SMarc-André Lureau *fd = mfd; 149d3592199SMarc-André Lureau return ptr; 1500f2956f9SMarc-André Lureau 1510f2956f9SMarc-André Lureau err: 1520f2956f9SMarc-André Lureau error_setg_errno(errp, errno, "failed to allocate shared memory"); 1530f2956f9SMarc-André Lureau if (mfd >= 0) { 1540f2956f9SMarc-André Lureau close(mfd); 1550f2956f9SMarc-André Lureau } 1560f2956f9SMarc-André Lureau return NULL; 157d3592199SMarc-André Lureau } 158d3592199SMarc-André Lureau 159d3592199SMarc-André Lureau void qemu_memfd_free(void *ptr, size_t size, int fd) 160d3592199SMarc-André Lureau { 161d3592199SMarc-André Lureau if (ptr) { 162d3592199SMarc-André Lureau munmap(ptr, size); 163d3592199SMarc-André Lureau } 164d3592199SMarc-André Lureau 165d3592199SMarc-André Lureau if (fd != -1) { 166d3592199SMarc-André Lureau close(fd); 167d3592199SMarc-André Lureau } 168d3592199SMarc-André Lureau } 16931190ed7SMarc-André Lureau 17031190ed7SMarc-André Lureau enum { 17131190ed7SMarc-André Lureau MEMFD_KO, 17231190ed7SMarc-André Lureau MEMFD_OK, 17331190ed7SMarc-André Lureau MEMFD_TODO 17431190ed7SMarc-André Lureau }; 17531190ed7SMarc-André Lureau 176648abbfbSMarc-André Lureau /** 177648abbfbSMarc-André Lureau * qemu_memfd_alloc_check(): 178648abbfbSMarc-André Lureau * 179648abbfbSMarc-André Lureau * Check if qemu_memfd_alloc() can allocate, including using a 180648abbfbSMarc-André Lureau * fallback implementation when host doesn't support memfd. 181648abbfbSMarc-André Lureau */ 182648abbfbSMarc-André Lureau bool qemu_memfd_alloc_check(void) 18331190ed7SMarc-André Lureau { 18431190ed7SMarc-André Lureau static int memfd_check = MEMFD_TODO; 18531190ed7SMarc-André Lureau 18631190ed7SMarc-André Lureau if (memfd_check == MEMFD_TODO) { 18731190ed7SMarc-André Lureau int fd; 18831190ed7SMarc-André Lureau void *ptr; 18931190ed7SMarc-André Lureau 1900f2956f9SMarc-André Lureau ptr = qemu_memfd_alloc("test", 4096, 0, &fd, NULL); 19131190ed7SMarc-André Lureau memfd_check = ptr ? MEMFD_OK : MEMFD_KO; 19231190ed7SMarc-André Lureau qemu_memfd_free(ptr, 4096, fd); 19331190ed7SMarc-André Lureau } 19431190ed7SMarc-André Lureau 19531190ed7SMarc-André Lureau return memfd_check == MEMFD_OK; 19631190ed7SMarc-André Lureau } 197648abbfbSMarc-André Lureau 198648abbfbSMarc-André Lureau /** 199648abbfbSMarc-André Lureau * qemu_memfd_check(): 200648abbfbSMarc-André Lureau * 201648abbfbSMarc-André Lureau * Check if host supports memfd. 202648abbfbSMarc-André Lureau */ 203648abbfbSMarc-André Lureau bool qemu_memfd_check(void) 204648abbfbSMarc-André Lureau { 205648abbfbSMarc-André Lureau #ifdef CONFIG_LINUX 206648abbfbSMarc-André Lureau static int memfd_check = MEMFD_TODO; 207648abbfbSMarc-André Lureau 208648abbfbSMarc-André Lureau if (memfd_check == MEMFD_TODO) { 209648abbfbSMarc-André Lureau int mfd = memfd_create("test", 0); 210648abbfbSMarc-André Lureau if (mfd >= 0) { 211648abbfbSMarc-André Lureau memfd_check = MEMFD_OK; 212648abbfbSMarc-André Lureau close(mfd); 213648abbfbSMarc-André Lureau } else { 214648abbfbSMarc-André Lureau memfd_check = MEMFD_KO; 215648abbfbSMarc-André Lureau } 216648abbfbSMarc-André Lureau } 217648abbfbSMarc-André Lureau 218648abbfbSMarc-André Lureau return memfd_check == MEMFD_OK; 219648abbfbSMarc-André Lureau #else 220648abbfbSMarc-André Lureau return false; 221648abbfbSMarc-André Lureau #endif 222648abbfbSMarc-André Lureau } 223