hw/9pfs/9p-util.h

   1 /*
   2  * 9p utilities
   3  *
   4  * Copyright IBM, Corp. 2017
   5  *
   6  * Authors:
   7  *  Greg Kurz <groug@kaod.org>
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  10  * See the COPYING file in the top-level directory.
  11  */
  12
  13 #ifndef QEMU_9P_UTIL_H
  14 #define QEMU_9P_UTIL_H
  15
  16 #ifdef O_PATH
  17 #define O_PATH_9P_UTIL O_PATH
  18 #else
  19 #define O_PATH_9P_UTIL 0
  20 #endif
  21
  22 #if !defined(CONFIG_LINUX)
  23
  24 /*
  25  * Generates a Linux device number (a.k.a. dev_t) for given device major
  26  * and minor numbers.
  27  *
  28  * To be more precise: it generates a device number in glibc's format
  29  * (MMMM_Mmmm_mmmM_MMmm, 64 bits) actually, which is compatible with
  30  * Linux's format (mmmM_MMmm, 32 bits), as described in <bits/sysmacros.h>.
  31  */
  32 static inline uint64_t makedev_dotl(uint32_t dev_major, uint32_t dev_minor)
  33 {
  34     uint64_t dev;
  35
  36     // from glibc sysmacros.h:
  37     dev  = (((uint64_t) (dev_major & 0x00000fffu)) <<  8);
  38     dev |= (((uint64_t) (dev_major & 0xfffff000u)) << 32);
  39     dev |= (((uint64_t) (dev_minor & 0x000000ffu)) <<  0);
  40     dev |= (((uint64_t) (dev_minor & 0xffffff00u)) << 12);
  41     return dev;
  42 }
  43
  44 #endif
  45
  46 /*
  47  * Converts given device number from host's device number format to Linux
  48  * device number format. As both the size of type dev_t and encoding of
  49  * dev_t is system dependant, we have to convert them for Linux guests if
  50  * host is not running Linux.
  51  */
  52 static inline uint64_t host_dev_to_dotl_dev(dev_t dev)
  53 {
  54 #ifdef CONFIG_LINUX
  55     return dev;
  56 #else
  57     return makedev_dotl(major(dev), minor(dev));
  58 #endif
  59 }
  60
  61 /* Translates errno from host -> Linux if needed */
  62 static inline int errno_to_dotl(int err) {
  63 #if defined(CONFIG_LINUX)
  64     /* nothing to translate (Linux -> Linux) */
  65 #elif defined(CONFIG_DARWIN)
  66     /*
  67      * translation mandatory for macOS hosts
  68      *
  69      * FIXME: Only most important errnos translated here yet, this should be
  70      * extended to as many errnos being translated as possible in future.
  71      */
  72     if (err == ENAMETOOLONG) {
  73         err = 36; /* ==ENAMETOOLONG on Linux */
  74     } else if (err == ENOTEMPTY) {
  75         err = 39; /* ==ENOTEMPTY on Linux */
  76     } else if (err == ELOOP) {
  77         err = 40; /* ==ELOOP on Linux */
  78     } else if (err == ENOATTR) {
  79         err = 61; /* ==ENODATA on Linux */
  80     } else if (err == ENOTSUP) {
  81         err = 95; /* ==EOPNOTSUPP on Linux */
  82     } else if (err == EOPNOTSUPP) {
  83         err = 95; /* ==EOPNOTSUPP on Linux */
  84     }
  85 #else
  86 #error Missing errno translation to Linux for this host system
  87 #endif
  88     return err;
  89 }
  90
  91 #ifdef CONFIG_DARWIN
  92 #define qemu_fgetxattr(...) fgetxattr(__VA_ARGS__, 0, 0)
  93 #else
  94 #define qemu_fgetxattr fgetxattr
  95 #endif
  96
  97 #define qemu_openat     openat
  98 #define qemu_fstatat    fstatat
  99 #define qemu_mkdirat    mkdirat
 100 #define qemu_renameat   renameat
 101 #define qemu_utimensat  utimensat
 102 #define qemu_unlinkat   unlinkat
 103
 104 static inline void close_preserve_errno(int fd)
 105 {
 106     int serrno = errno;
 107     close(fd);
 108     errno = serrno;
 109 }
 110
 111 static inline int openat_dir(int dirfd, const char *name)
 112 {
 113     return qemu_openat(dirfd, name,
 114                        O_DIRECTORY | O_RDONLY | O_NOFOLLOW | O_PATH_9P_UTIL);
 115 }
 116
 117 static inline int openat_file(int dirfd, const char *name, int flags,
 118                               mode_t mode)
 119 {
 120     int fd, serrno, ret;
 121
 122 #ifndef CONFIG_DARWIN
 123 again:
 124 #endif
 125     fd = qemu_openat(dirfd, name, flags | O_NOFOLLOW | O_NOCTTY | O_NONBLOCK,
 126                      mode);
 127     if (fd == -1) {
 128 #ifndef CONFIG_DARWIN
 129         if (errno == EPERM && (flags & O_NOATIME)) {
 130             /*
 131              * The client passed O_NOATIME but we lack permissions to honor it.
 132              * Rather than failing the open, fall back without O_NOATIME. This
 133              * doesn't break the semantics on the client side, as the Linux
 134              * open(2) man page notes that O_NOATIME "may not be effective on
 135              * all filesystems". In particular, NFS and other network
 136              * filesystems ignore it entirely.
 137              */
 138             flags &= ~O_NOATIME;
 139             goto again;
 140         }
 141 #endif
 142         return -1;
 143     }
 144
 145     serrno = errno;
 146     /* O_NONBLOCK was only needed to open the file. Let's drop it. We don't
 147      * do that with O_PATH since fcntl(F_SETFL) isn't supported, and openat()
 148      * ignored it anyway.
 149      */
 150     if (!(flags & O_PATH_9P_UTIL)) {
 151         ret = fcntl(fd, F_SETFL, flags);
 152         assert(!ret);
 153     }
 154     errno = serrno;
 155     return fd;
 156 }
 157
 158 ssize_t fgetxattrat_nofollow(int dirfd, const char *path, const char *name,
 159                              void *value, size_t size);
 160 int fsetxattrat_nofollow(int dirfd, const char *path, const char *name,
 161                          void *value, size_t size, int flags);
 162 ssize_t flistxattrat_nofollow(int dirfd, const char *filename,
 163                               char *list, size_t size);
 164 ssize_t fremovexattrat_nofollow(int dirfd, const char *filename,
 165                                 const char *name);
 166
 167 /*
 168  * Darwin has d_seekoff, which appears to function similarly to d_off.
 169  * However, it does not appear to be supported on all file systems,
 170  * so ensure it is manually injected earlier and call here when
 171  * needed.
 172  */
 173 static inline off_t qemu_dirent_off(struct dirent *dent)
 174 {
 175 #ifdef CONFIG_DARWIN
 176     return dent->d_seekoff;
 177 #else
 178     return dent->d_off;
 179 #endif
 180 }
 181
 182 /**
 183  * qemu_dirent_dup() - Duplicate directory entry @dent.
 184  *
 185  * @dent: original directory entry to be duplicated
 186  * Return: duplicated directory entry which should be freed with g_free()
 187  *
 188  * It is highly recommended to use this function instead of open coding
 189  * duplication of dirent objects, because the actual struct dirent
 190  * size may be bigger or shorter than sizeof(struct dirent) and correct
 191  * handling is platform specific (see gitlab issue #841).
 192  */
 193 static inline struct dirent *qemu_dirent_dup(struct dirent *dent)
 194 {
 195     size_t sz = 0;
 196 #if defined _DIRENT_HAVE_D_RECLEN
 197     /* Avoid use of strlen() if platform supports d_reclen. */
 198     sz = dent->d_reclen;
 199 #endif
 200     /*
 201      * Test sz for zero even if d_reclen is available
 202      * because some drivers may set d_reclen to zero.
 203      */
 204     if (sz == 0) {
 205         /* Fallback to the most portable way. */
 206         sz = offsetof(struct dirent, d_name) +
 207                       strlen(dent->d_name) + 1;
 208     }
 209     return g_memdup(dent, sz);
 210 }
 211
 212 /*
 213  * As long as mknodat is not available on macOS, this workaround
 214  * using pthread_fchdir_np is needed. qemu_mknodat is defined in
 215  * os-posix.c. pthread_fchdir_np is weakly linked here as a guard
 216  * in case it disappears in future macOS versions, because it is
 217  * is a private API.
 218  */
 219 #if defined CONFIG_DARWIN && defined CONFIG_PTHREAD_FCHDIR_NP
 220 int pthread_fchdir_np(int fd) __attribute__((weak_import));
 221 #endif
 222 int qemu_mknodat(int dirfd, const char *filename, mode_t mode, dev_t dev);
 223
 224 #endif