1 files changed, 80 insertions, 0 deletions
diff --git a/libc-bottom-half/cloudlibc/src/libc/fcntl/openat.c b/libc-bottom-half/cloudlibc/src/libc/fcntl/openat.c
new file mode 100644
index 0000000..09cbbf8
--- /dev/null
+++ b/libc-bottom-half/cloudlibc/src/libc/fcntl/openat.c
@@ -0,0 +1,80 @@
+// Copyright (c) 2015-2016 Nuxi, https://nuxi.nl/
+//
+// SPDX-License-Identifier: BSD-2-Clause
+
+#include <assert.h>
+#include <wasi/api.h>
+#include <wasi/libc.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <string.h>
+
+static_assert(O_APPEND == __WASI_FDFLAGS_APPEND, "Value mismatch");
+static_assert(O_DSYNC == __WASI_FDFLAGS_DSYNC, "Value mismatch");
+static_assert(O_NONBLOCK == __WASI_FDFLAGS_NONBLOCK, "Value mismatch");
+static_assert(O_RSYNC == __WASI_FDFLAGS_RSYNC, "Value mismatch");
+static_assert(O_SYNC == __WASI_FDFLAGS_SYNC, "Value mismatch");
+
+static_assert(O_CREAT >> 12 == __WASI_OFLAGS_CREAT, "Value mismatch");
+static_assert(O_DIRECTORY >> 12 == __WASI_OFLAGS_DIRECTORY, "Value mismatch");
+static_assert(O_EXCL >> 12 == __WASI_OFLAGS_EXCL, "Value mismatch");
+static_assert(O_TRUNC >> 12 == __WASI_OFLAGS_TRUNC, "Value mismatch");
+
+int __wasilibc_nocwd_openat_nomode(int fd, const char *path, int oflag) {
+  // Compute rights corresponding with the access modes provided.
+  // Attempt to obtain all rights, except the ones that contradict the
+  // access mode provided to openat().
+  __wasi_rights_t max =
+      ~(__WASI_RIGHTS_FD_DATASYNC | __WASI_RIGHTS_FD_READ |
+        __WASI_RIGHTS_FD_WRITE | __WASI_RIGHTS_FD_ALLOCATE |
+        __WASI_RIGHTS_FD_READDIR | __WASI_RIGHTS_FD_FILESTAT_SET_SIZE);
+  switch (oflag & O_ACCMODE) {
+    case O_RDONLY:
+    case O_RDWR:
+    case O_WRONLY:
+      if ((oflag & O_RDONLY) != 0) {
+        max |= __WASI_RIGHTS_FD_READ | __WASI_RIGHTS_FD_READDIR;
+      }
+      if ((oflag & O_WRONLY) != 0) {
+        max |= __WASI_RIGHTS_FD_DATASYNC | __WASI_RIGHTS_FD_WRITE |
+               __WASI_RIGHTS_FD_ALLOCATE |
+               __WASI_RIGHTS_FD_FILESTAT_SET_SIZE;
+      }
+      break;
+    case O_EXEC:
+      break;
+    case O_SEARCH:
+      break;
+    default:
+      errno = EINVAL;
+      return -1;
+  }
+
+  // Ensure that we can actually obtain the minimal rights needed.
+  __wasi_fdstat_t fsb_cur;
+  __wasi_errno_t error = __wasi_fd_fdstat_get(fd, &fsb_cur);
+  if (error != 0) {
+    errno = error;
+    return -1;
+  }
+
+  // Path lookup properties.
+  __wasi_lookupflags_t lookup_flags = 0;
+  if ((oflag & O_NOFOLLOW) == 0)
+    lookup_flags |= __WASI_LOOKUPFLAGS_SYMLINK_FOLLOW;
+
+  // Open file with appropriate rights.
+  __wasi_fdflags_t fs_flags = oflag & 0xfff;
+  __wasi_rights_t fs_rights_base = max & fsb_cur.fs_rights_inheriting;
+  __wasi_rights_t fs_rights_inheriting = fsb_cur.fs_rights_inheriting;
+  __wasi_fd_t newfd;
+  error = __wasi_path_open(fd, lookup_flags, path,
+                                 (oflag >> 12) & 0xfff,
+                                 fs_rights_base, fs_rights_inheriting, fs_flags,
+                                 &newfd);
+  if (error != 0) {
+    errno = error;
+    return -1;
+  }
+  return newfd;
+}