1 files changed, 85 insertions, 0 deletions
diff --git a/libc/sysdeps/linux/aarch64/clone.S b/libc/sysdeps/linux/aarch64/clone.S
new file mode 100644
index 000000000..7437eec8d
--- /dev/null
+++ b/libc/sysdeps/linux/aarch64/clone.S
@@ -0,0 +1,85 @@
+/* Copyright (C) 1996-2017 Free Software Foundation, Inc.
+
+   This file is part of the GNU C Library.
+
+   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/>.  */
+
+/* clone() is even more special than fork() as it mucks with stacks
+   and invokes a function in the right context after its all over.  */
+
+#include <sysdep.h>
+#define _ERRNO_H	1
+#include <bits/errno.h>
+
+#define CLONE_VM_BIT      8
+#define CLONE_VM          (1 << CLONE_VM_BIT)
+
+#define CLONE_THREAD_BIT  16
+#define CLONE_THREAD      (1 << CLONE_THREAD_BIT)
+
+/* int clone(int (*fn)(void *arg),            x0
+	     void *child_stack,               x1
+	     int flags,                       x2
+	     void *arg,                       x3
+	     pid_t *ptid,                     x4
+	     struct user_desc *tls,           x5
+             pid_t *ctid);                    x6
+ */
+        .text
+ENTRY(__clone)
+	/* Save args for the child.  */
+	mov	x10, x0
+	mov	x11, x2
+	mov	x12, x3
+
+	/* Sanity check args.  */
+	mov	x0, #-EINVAL
+	cbz	x10, .Lsyscall_error
+	cbz	x1, .Lsyscall_error
+
+	/* Do the system call.  */
+	/* X0:flags, x1:newsp, x2:parenttidptr, x3:newtls, x4:childtid.  */
+	mov	x0, x2                  /* flags  */
+	/* New sp is already in x1.  */
+	mov	x2, x4			/* ptid  */
+	mov	x3, x5			/* tls  */
+	mov	x4, x6			/* ctid  */
+	mov	x8, #SYS_ify(clone)
+	svc	0x0
+
+	cmp	x0, #0
+	beq	thread_start
+	blt	.Lsyscall_error
+	RET
+PSEUDO_END (__clone)
+
+	.align 4
+	.type thread_start, %function
+thread_start:
+	cfi_startproc
+	cfi_undefined (x30)
+	mov	x29, 0
+
+	/* Pick the function arg and execute.  */
+	mov	x0, x12
+	blr	x10
+
+	/* We are done, pass the return value through x0.  */
+	b	HIDDEN_JUMPTARGET(_exit)
+	cfi_endproc
+	.size thread_start, .-thread_start
+
+libc_hidden_def (__clone)
+weak_alias (__clone, clone)