From 510638eaa788a8ca67902c2d1ee0f9cb5a9fcd44 Mon Sep 17 00:00:00 2001
From: mmel <mmel@FreeBSD.org>
Date: Tue, 9 May 2017 12:14:00 +0000
Subject: [PATCH] Fix _Unwind_Backtrace symbol version for ARM.

In real GNU libgcc, _Unwind_Backtrace is published with GCC_3.3 version
for all architectures but ARM. For ARM it's publishes with GCC_4.3.0
version.
This exception is not implement in your version of libggc, thus we
export _Unwind_Backtrace with bad version. To maintain backward
compatibility, publish _Unwind_Backtrace twice, once as compatible
symbol with GCC_3.3 version, and once as default symbol with
GCC_4.3.0 version.

While I'm in, fix typo in GCC_4.2.0 to GCC_4.3.0 inheritance declaration.

MFC after:	2 weeks
---
 contrib/gcc/config/arm/libgcc-bpabi.ver |  8 ++++++++
 contrib/gcc/config/arm/libunwind-arm.S  | 18 ++++++++++++++++++
 contrib/gcc/libgcc-std.ver              |  2 +-
 sys/arm/conf/std.armv6                  |  8 ++++----
 4 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/contrib/gcc/config/arm/libgcc-bpabi.ver b/contrib/gcc/config/arm/libgcc-bpabi.ver
index 2f259eb646e0..26d3c49608cb 100644
--- a/contrib/gcc/config/arm/libgcc-bpabi.ver
+++ b/contrib/gcc/config/arm/libgcc-bpabi.ver
@@ -81,3 +81,11 @@ GCC_3.5 {
   # GNU-specific entry point.
   __gnu_unwind_frame
 }
+
+%exclude {
+  _Unwind_Backtrace
+}
+
+GCC_4.3.0 {
+  _Unwind_Backtrace
+}
diff --git a/contrib/gcc/config/arm/libunwind-arm.S b/contrib/gcc/config/arm/libunwind-arm.S
index 8b1e2f3722e4..da553a4bfe78 100644
--- a/contrib/gcc/config/arm/libunwind-arm.S
+++ b/contrib/gcc/config/arm/libunwind-arm.S
@@ -133,4 +133,22 @@ UNWIND_WRAPPER _Unwind_Resume_or_Rethrow 1
 UNWIND_WRAPPER _Unwind_ForcedUnwind 3
 UNWIND_WRAPPER _Unwind_Backtrace 2
 
+/*
+ * Originally, we incorrectly export _Unwind_Backtrace symbol
+ * with  GCC_3.3 version, but real GCC libgcc export it as GCC_4.3.0.
+ * To maintain  backward compatibility, export it with both versions where 
+ * GCC_4.3.0 is default one.
+ *
+ * The workaround is complicated by next two issues:
+ *  - old GNU ld cannot handle two (or more) symbol versions
+ *    targeting same function.
+ *  - the .weakref crashes clang 4.0
+ */
+	.globl	SYM(_Unwind_Backtrace33)
+	TYPE(_Unwind_Backtrace33)
+SYM(_Unwind_Backtrace33):
+	b _Unwind_Backtrace
+
+	.symver	SYM(_Unwind_Backtrace33),_Unwind_Backtrace@GCC_3.3
+
 #endif  /* ndef __symbian__ */
diff --git a/contrib/gcc/libgcc-std.ver b/contrib/gcc/libgcc-std.ver
index 2d0a43df01d3..6e747ed7bc1b 100644
--- a/contrib/gcc/libgcc-std.ver
+++ b/contrib/gcc/libgcc-std.ver
@@ -275,7 +275,7 @@ GCC_4.2.0 {
   _Unwind_GetIPInfo
 }
 
-%inherit GCC_4.3 GCC_4.2.0
+%inherit GCC_4.3.0 GCC_4.2.0
 GCC_4.3.0 {
   # byte swapping routines
   __bswapsi2
diff --git a/sys/arm/conf/std.armv6 b/sys/arm/conf/std.armv6
index 4ee9caff32e7..2bf63c8b2793 100644
--- a/sys/arm/conf/std.armv6
+++ b/sys/arm/conf/std.armv6
@@ -68,10 +68,10 @@ options 	USB_DEBUG		# Enable usb debug support code
 # Optional extras, never enabled by default:
 #options 	BOOTVERBOSE
 #options 	DEBUG			# May result in extreme spewage
-#options 	KTR
-#options 	KTR_COMPILE=KTR_ALL
-#options 	KTR_ENTRIES=16384
-#options 	KTR_MASK=(KTR_SPARE2)
+options 	KTR
+options 	KTR_COMPILE=KTR_ALL
+options 	KTR_ENTRIES=163840
+options 	KTR_MASK=(KTR_SPARE3)
 #options 	KTR_VERBOSE=0
 #options 	USB_REQ_DEBUG
 #options 	USB_VERBOSE