1 files changed, 63 insertions, 0 deletions
diff --git a/libc/sysdeps/linux/arm/swapcontext.S b/libc/sysdeps/linux/arm/swapcontext.S
new file mode 100644
index 000000000..ba6e31c4d
--- /dev/null
+++ b/libc/sysdeps/linux/arm/swapcontext.S
@@ -0,0 +1,63 @@
+/* Copyright (C) 2012 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/>.  */
+
+#include <sysdep.h>
+
+#include "ucontext_i.h"
+
+	.syntax unified
+	.text
+
+/* int swapcontext (ucontext_t *oucp, const ucontext_t *ucp) */
+
+ENTRY(swapcontext)
+
+	/* Have getcontext() do most of the work then fix up
+	   LR afterwards.  Save R3 to keep the stack aligned.  */
+	push	{r0,r1,r3,r14}
+	cfi_adjust_cfa_offset (16)
+	cfi_rel_offset (r0,0)
+	cfi_rel_offset (r1,4)
+	cfi_rel_offset (r3,8)
+	cfi_rel_offset (r14,12)
+
+	bl	__getcontext
+	mov	r4, r0
+
+	pop	{r0,r1,r3,r14}
+	cfi_adjust_cfa_offset (-16)
+	cfi_restore (r0)
+	cfi_restore (r1)
+	cfi_restore (r3)
+	cfi_restore (r14)
+
+	/* Exit if getcontext() failed.  */
+	cmp 	r4, #0
+	itt	ne
+	movne	r0, r4
+	RETINSTR(ne, r14)
+
+	/* Fix up LR and the PC.  */
+	str	r13,[r0, #MCONTEXT_ARM_SP]
+	str	r14,[r0, #MCONTEXT_ARM_LR]
+	str	r14,[r0, #MCONTEXT_ARM_PC]
+
+	/* And swap using swapcontext().  */
+	mov	r0, r1
+	b	__setcontext
+
+END(swapcontext)