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glibc/startcontext-cantunwind.patch

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From 1061d6fe364ddac7458a872839ea9efe8f7600f0 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
__startcontext marks the bottom of the call stack of the contexts created
by makecontext.
[BZ #20435]
* sysdeps/unix/sysv/linux/arm/setcontext.S (__startcontext): Mark
as .cantunwind.
---
sysdeps/unix/sysv/linux/arm/setcontext.S | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/sysdeps/unix/sysv/linux/arm/setcontext.S b/sysdeps/unix/sysv/linux/arm/setcontext.S
index 603e508..d1f168f 100644
--- a/sysdeps/unix/sysv/linux/arm/setcontext.S
+++ b/sysdeps/unix/sysv/linux/arm/setcontext.S
@@ -86,12 +86,19 @@ weak_alias(__setcontext, setcontext)
/* 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
--
2.9.2