open: Use openat if arch does not have the open syscall

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>

Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

libc/sysdeps/linux/common/open.c

@@ -12,13 +12,18 @@
 #include <stdarg.h>
 #include <cancel.h>
 
-#define __NR___syscall_open __NR_open
+#if defined __NR_open
+# define __NR___syscall_open __NR_open
 static __always_inline _syscall3(int, __syscall_open, const char *, file,
 				 int, flags, __kernel_mode_t, mode)
 strong_alias_untyped(__syscall_open,__NC(open))
 
-#define __NR___open2_nocancel __NR_open
+# define __NR___open2_nocancel __NR_open
 _syscall2(int, __NC(open2), const char *, file, int, flags)
+#else
+int __open2_nocancel(const char *, int) __nonnull ((1)) attribute_hidden;
+int __open_nocancel(const char *, int, mode_t) __nonnull ((1)) attribute_hidden;
+#endif
 
 int open(const char *file, int oflag, ...)
 {
@@ -32,13 +37,26 @@ int open(const char *file, int oflag, ...)
 	}
 
 	if (SINGLE_THREAD_P)
+#if defined(__NR_open)
 		return __NC(open)(file, oflag, mode);
+#elif defined(__NR_openat)
+		return openat(AT_FDCWD, file, oflag, mode);
+#endif
+
 #ifdef __NEW_THREADS
 	int oldtype = LIBC_CANCEL_ASYNC ();
+# if defined(__NR_open)
 	int result = __NC(open)(file, oflag, mode);
+# else
+	int result = openat(AT_FDCWD, file, oflag, mode);
+# endif
 	LIBC_CANCEL_RESET (oldtype);
 	return result;
 #endif
 }
 lt_strong_alias(open)
 lt_libc_hidden(open)
+#if !defined(__NR_open)
+strong_alias_untyped(open,__open2_nocancel)
+strong_alias_untyped(open,__open_nocancel)
+#endif