Based on

From 9e2ff6c9cc54c0b4402b8d49e4abe7000fde7617 Mon Sep 17 00:00:00 2001
From: Andreas Schwab <schwab@suse.de>
Date: Mon, 8 Aug 2016 09:29:18 +0200
Subject: [PATCH] arm: mark __startcontext as .cantunwind (bug 20435)

diff -Naur a/sysdeps/unix/sysv/linux/arm/setcontext.S b/sysdeps/unix/sysv/linux/arm/setcontext.S
--- a/sysdeps/unix/sysv/linux/arm/setcontext.S	2017-12-18 12:04:34.382270698 +0530
+++ b/sysdeps/unix/sysv/linux/arm/setcontext.S	2017-12-18 12:05:18.338269741 +0530
@@ -86,12 +86,19 @@
 
 	/* Called when a makecontext() context returns.  Start the
 	   context in R4 or fall through to exit().  */
+	/* Unwind descriptors are looked up based on PC - 2, so we have to
+	   make sure to mark the instruction preceding the __startcontext
+	   label as .cantunwind.  */
+	.fnstart
+	.cantunwind
+	nop
 ENTRY(__startcontext)
 	movs    r0, r4
 	bne     PLTJMP(__setcontext)
 
 	@ New context was 0 - exit
 	b       PLTJMP(HIDDEN_JUMPTARGET(exit))
+	.fnend
 END(__startcontext)
 
 #ifdef PIC