libc-bottom-half/cloudlibc/src/libc/fcntl/openat.c

   1 // Copyright (c) 2015-2016 Nuxi, https://nuxi.nl/
   2 //
   3 // SPDX-License-Identifier: BSD-2-Clause
   4
   5 #include <common/errno.h>
   6
   7 #include <assert.h>
   8 #include <wasi/api.h>
   9 #include <wasi/libc.h>
  10 #include <errno.h>
  11 #include <fcntl.h>
  12 #include <string.h>
  13
  14 static_assert(O_APPEND == __WASI_FDFLAGS_APPEND, "Value mismatch");
  15 static_assert(O_DSYNC == __WASI_FDFLAGS_DSYNC, "Value mismatch");
  16 static_assert(O_NONBLOCK == __WASI_FDFLAGS_NONBLOCK, "Value mismatch");
  17 static_assert(O_RSYNC == __WASI_FDFLAGS_RSYNC, "Value mismatch");
  18 static_assert(O_SYNC == __WASI_FDFLAGS_SYNC, "Value mismatch");
  19
  20 static_assert(O_CREAT >> 12 == __WASI_OFLAGS_CREAT, "Value mismatch");
  21 static_assert(O_DIRECTORY >> 12 == __WASI_OFLAGS_DIRECTORY, "Value mismatch");
  22 static_assert(O_EXCL >> 12 == __WASI_OFLAGS_EXCL, "Value mismatch");
  23 static_assert(O_TRUNC >> 12 == __WASI_OFLAGS_TRUNC, "Value mismatch");
  24
  25 int __wasilibc_nocwd_openat_nomode(int fd, const char *path, int oflag) {
  26   // Compute rights corresponding with the access modes provided.
  27   // Attempt to obtain all rights, except the ones that contradict the
  28   // access mode provided to openat().
  29   __wasi_rights_t max =
  30       ~(__WASI_RIGHTS_FD_DATASYNC | __WASI_RIGHTS_FD_READ |
  31         __WASI_RIGHTS_FD_WRITE | __WASI_RIGHTS_FD_ALLOCATE |
  32         __WASI_RIGHTS_FD_READDIR | __WASI_RIGHTS_FD_FILESTAT_SET_SIZE);
  33   switch (oflag & O_ACCMODE) {
  34     case O_RDONLY:
  35     case O_RDWR:
  36     case O_WRONLY:
  37       if ((oflag & O_RDONLY) != 0) {
  38         max |= __WASI_RIGHTS_FD_READ | __WASI_RIGHTS_FD_READDIR;
  39       }
  40       if ((oflag & O_WRONLY) != 0) {
  41         max |= __WASI_RIGHTS_FD_DATASYNC | __WASI_RIGHTS_FD_WRITE |
  42                __WASI_RIGHTS_FD_ALLOCATE |
  43                __WASI_RIGHTS_FD_FILESTAT_SET_SIZE;
  44       }
  45       break;
  46     case O_EXEC:
  47       break;
  48     case O_SEARCH:
  49       break;
  50     default:
  51       errno = EINVAL;
  52       return -1;
  53   }
  54
  55   // Ensure that we can actually obtain the minimal rights needed.
  56   __wasi_fdstat_t fsb_cur;
  57   __wasi_errno_t error = __wasi_fd_fdstat_get(fd, &fsb_cur);
  58   if (error != 0) {
  59     errno = error;
  60     return -1;
  61   }
  62
  63   // Path lookup properties.
  64   __wasi_lookupflags_t lookup_flags = 0;
  65   if ((oflag & O_NOFOLLOW) == 0)
  66     lookup_flags |= __WASI_LOOKUPFLAGS_SYMLINK_FOLLOW;
  67
  68   // Open file with appropriate rights.
  69   __wasi_fdflags_t fs_flags = oflag & 0xfff;
  70   __wasi_rights_t fs_rights_base = max & fsb_cur.fs_rights_inheriting;
  71   __wasi_rights_t fs_rights_inheriting = fsb_cur.fs_rights_inheriting;
  72   __wasi_fd_t newfd;
  73   error = __wasi_path_open(fd, lookup_flags, path,
  74                                  (oflag >> 12) & 0xfff,
  75                                  fs_rights_base, fs_rights_inheriting, fs_flags,
  76                                  &newfd);
  77   if (error != 0) {
  78     errno = errno_fixup_directory(fd, error);
  79     return -1;
  80   }
  81   return newfd;
  82 }