2018-03-01  Aurelien Jarno  <aurelien@aurel32.net>

	[BZ #22910]
	* sysdeps/unix/sysv/linux/alpha/setcontext.S (__startcontext): Set
	up CFI directive to forbid further backtracing.


--- a/sysdeps/unix/sysv/linux/alpha/makecontext.S
+++ b/sysdeps/unix/sysv/linux/alpha/makecontext.S
@@ -138,10 +138,14 @@ weak_alias (__makecontext, makecontext)
 
 	.align	4
 	.ent	__startcontext
+	cfi_startproc
 __startcontext:
 	.frame $31, 0, $31, 0
 	.prologue 0
 
+	/* Mark ra as undefined in order to stop unwinding here.  */
+	cfi_undefined(ra)
+
 	jsr	$26, ($27), 0
 	ldgp	$29, 0($26)
 	mov	$9, $16
@@ -160,4 +164,5 @@ __startcontext:
 
 	halt
 
+	cfi_endproc
 	.end __startcontext