1 files changed, 53 insertions, 0 deletions
diff --git a/libc-bottom-half/cloudlibc/src/libc/unistd/faccessat.c b/libc-bottom-half/cloudlibc/src/libc/unistd/faccessat.c
new file mode 100644
index 0000000..ffaef6e
--- /dev/null
+++ b/libc-bottom-half/cloudlibc/src/libc/unistd/faccessat.c
@@ -0,0 +1,53 @@
+// Copyright (c) 2016 Nuxi, https://nuxi.nl/
+//
+// SPDX-License-Identifier: BSD-2-Clause
+
+#include <wasi/api.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <string.h>
+#include <unistd.h>
+
+int __wasilibc_nocwd_faccessat(int fd, const char *path, int amode, int flag) {
+  // Validate function parameters.
+  if ((amode & ~(F_OK | R_OK | W_OK | X_OK)) != 0 ||
+      (flag & ~AT_EACCESS) != 0) {
+    errno = EINVAL;
+    return -1;
+  }
+
+  // Check for target file existence and obtain the file type.
+  __wasi_lookupflags_t lookup_flags = __WASI_LOOKUPFLAGS_SYMLINK_FOLLOW;
+  __wasi_filestat_t file;
+  __wasi_errno_t error =
+      __wasi_path_filestat_get(fd, lookup_flags, path, &file);
+  if (error != 0) {
+    errno = error;
+    return -1;
+  }
+
+  // Test whether the requested access rights are present on the
+  // directory file descriptor.
+  if (amode != 0) {
+    __wasi_fdstat_t directory;
+    error = __wasi_fd_fdstat_get(fd, &directory);
+    if (error != 0) {
+      errno = error;
+      return -1;
+    }
+
+    __wasi_rights_t min = 0;
+    if ((amode & R_OK) != 0)
+      min |= file.filetype == __WASI_FILETYPE_DIRECTORY
+                 ? __WASI_RIGHTS_FD_READDIR
+                 : __WASI_RIGHTS_FD_READ;
+    if ((amode & W_OK) != 0)
+      min |= __WASI_RIGHTS_FD_WRITE;
+
+    if ((min & directory.fs_rights_inheriting) != min) {
+      errno = EACCES;
+      return -1;
+    }
+  }
+  return 0;
+}