add experimental aarch64 support

Ported over from GNU C Library and runtime tested in Qemu.

1 files changed, 42 insertions, 0 deletions

diff --git a/libc/sysdeps/linux/aarch64/syscall.S b/libc/sysdeps/linux/aarch64/syscall.S
new file mode 100644
index 000000000..ac609a337
--- /dev/null
+++ b/libc/sysdeps/linux/aarch64/syscall.S
@@ -0,0 +1,42 @@
+/* Copyright (C) 2005-2017 Free Software Foundation, Inc.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public License as
+   published by the Free Software Foundation; either version 2.1 of the
+   License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <sysdep.h>
+
+/* syscall (int nr, ...)
+
+   AArch64 system calls take between 0 and 7 arguments. On entry here nr
+   is in w0 and any other system call arguments are in register x1..x7.
+
+   For kernel entry we need to move the system call nr to x8 then
+   load the remaining arguments to register. */
+
+ENTRY (syscall)
+	uxtw	x8, w0
+	mov	x0, x1
+	mov	x1, x2
+	mov	x2, x3
+	mov	x3, x4
+	mov	x4, x5
+	mov	x5, x6
+	mov	x6, x7
+	svc	0x0
+	cmn	x0, #4095
+	b.cs	1f
+	RET
+1:
+	b	SYSCALL_ERROR
+PSEUDO_END (syscall)