auto import from //depot/cupcake/@135843
diff --git a/libc/arch-arm/bionic/tkill.S b/libc/arch-arm/bionic/tkill.S
new file mode 100644
index 0000000..7b3301a
--- /dev/null
+++ b/libc/arch-arm/bionic/tkill.S
@@ -0,0 +1,53 @@
+/*
+ * Copyright (C) 2008 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.
+ */
+/* unlike our auto-generated syscall stubs, this code saves lr
+ on the stack, as well as a few other registers. this makes
+ our stack unwinder happy, when we generate debug stack
+ traces after the C library or other parts of the system
+ abort due to a fatal runtime error (e.g. detection
+ of a corrupted malloc heap).
+*/
+#include <sys/linux-syscalls.h>
+
+#ifndef __NR_tkill
+#define __NR_tkill 238
+#endif
+
+ .text
+ .type tkill, #function
+ .globl tkill
+ .align 4
+
+tkill:
+ stmfd sp!, {r4-r7, ip, lr}
+ ldr r7, =__NR_tkill
+ swi #0
+ ldmfd sp!, {r4-r7, ip, lr}
+ movs r0, r0
+ bxpl lr
+ b __set_syscall_errno