1 files changed, 59 insertions, 0 deletions
diff --git a/libc/bionic/faccessat.cpp b/libc/bionic/faccessat.cpp
new file mode 100644
index 0000000..5f375e0
--- /dev/null
+++ b/libc/bionic/faccessat.cpp
@@ -0,0 +1,59 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <fcntl.h>
+#include <unistd.h>
+#include <errno.h>
+
+extern "C" int ___faccessat(int, const char*, int);
+
+int faccessat(int dirfd, const char* pathname, int mode, int flags) {
+  // "The mode specifies the accessibility check(s) to be performed,
+  // and is either the value F_OK, or a mask consisting of the
+  // bitwise OR of one or more of R_OK, W_OK, and X_OK."
+  if ((mode != F_OK) && ((mode & ~(R_OK | W_OK | X_OK)) != 0) &&
+      ((mode & (R_OK | W_OK | X_OK)) == 0)) {
+    errno = EINVAL;
+    return -1;
+  }
+
+  if (flags != 0) {
+    // We deliberately don't support AT_SYMLINK_NOFOLLOW, a glibc
+    // only feature which is error prone and dangerous.
+    //
+    // AT_EACCESS isn't supported either. Android doesn't have setuid
+    // programs, and never runs code with euid!=uid. It could be
+    // implemented in an expensive way, following the model at
+    // https://gitlab.com/bminor/musl/commit/0a05eace163cee9b08571d2ff9d90f5e82d9c228
+    // but not worth it.
+    errno = EINVAL;
+    return -1;
+  }
+
+  return ___faccessat(dirfd, pathname, mode);
+}