Fix llvm-libunwind userspace build on ARM

GCC's libgcc exports a few ARM-specific symbols for ARM EABI, AEABI, or
EHABI or whatever it's called.  Export the same ones from LLVM-libunwind's
libgcc_s, on ARM.  As part of this, convert libgcc_s from a direct
Version.map to one constructed from component Symbol.map files.  This allows
the ARM-specific Symbol.map to be included only on ARM.

Fix ARM-only oddities in struct name/aliases in LLVM-libunwind to match
non-ARM definitions and ARM-specific expectations in libcxxrt /
libcompiler_rt.

No functional change intended for non-ARM architectures.

This commit does not actually flip the switch for ARM defaults from libgcc
to llvm-libunwind, but makes it possible (to compile, anyway).

contrib/compiler-rt/lib/builtins/gcc_personality_v0.c

@@ -9,8 +9,23 @@
 #include "int_lib.h"
 
 #include <unwind.h>
+/*
+ * XXX On FreeBSD, this file is compiled into three libraries:
+ *   - libcompiler_rt
+ *   - libgcc_eh
+ *   - libgcc_s
+ *
+ * In the former, the include path points to the contrib/libcxxrt/unwind-arm.h
+ * copy of unwind.h.  In the latter, the include path points to the
+ * contrib/libunwind/include/unwind.h header (LLVM libunwind).
+ *
+ * Neither (seemingly redundant) variant of unwind.h needs the redefinitions
+ * provided in the "helpful" header below, and libcxxrt's unwind-arm.h provides
+ * *no* useful distinguishing macros, so just forcibly disable the helper
+ * header on FreeBSD.
+ */
 #if defined(__arm__) && !defined(__ARM_DWARF_EH__) &&                          \
-    !defined(__USING_SJLJ_EXCEPTIONS__)
+    !defined(__USING_SJLJ_EXCEPTIONS__) && !defined(__FreeBSD__)
 // When building with older compilers (e.g. clang <3.9), it is possible that we
 // have a version of unwind.h which does not provide the EHABI declarations
 // which are quired for the C personality to conform to the specification.  In

contrib/libunwind/include/unwind.h

@@ -66,12 +66,16 @@ static const _Unwind_State _US_ACTION_MASK            = 3;
 static const _Unwind_State _US_FORCE_UNWIND           = 8;
 
 typedef uint32_t _Unwind_EHT_Header;
+/*
+ * gcc_personality_v0 references 'struct _Unwind_Exception' all over the place.
+ * Nothing in libunwind cares about 'struct _Unwind_Control_Block,' so make it
+ * the alias of struct _Unwind_Exception, instead of the other way around.
+ */
+struct _Unwind_Exception;
+typedef struct _Unwind_Exception _Unwind_Exception;
+typedef struct _Unwind_Exception _Unwind_Control_Block; /* Alias */
 
-struct _Unwind_Control_Block;
-typedef struct _Unwind_Control_Block _Unwind_Control_Block;
-typedef struct _Unwind_Control_Block _Unwind_Exception; /* Alias */
-
-struct _Unwind_Control_Block {
+struct _Unwind_Exception {
   uint64_t exception_class;
   void (*exception_cleanup)(_Unwind_Reason_Code, _Unwind_Control_Block*);
 

lib/libcompiler_rt/Makefile

@@ -12,10 +12,6 @@ CFLAGS+=	-fvisibility=hidden
 CFLAGS+=	-DVISIBILITY_HIDDEN
 CFLAGS+=	-I${SRCTOP}/contrib/libcxxrt
 
-.if ${COMPILER_TYPE} == "clang"
-CWARNFLAGS.gcc_personality_v0.c+= -Wno-typedef-redefinition
-.endif
-
 # gcc has incompatible internal declarations for __divtc3 and __multc3, but has
 # no option to silence its warning, so make warnings non-fatal.
 NO_WERROR.gcc=

lib/libgcc_s/Makefile

@@ -4,12 +4,22 @@ PACKAGE=	clibs
 SHLIB_NAME=	libgcc_s.so.1
 SHLIBDIR?=	/lib
 
+.include <bsd.opts.mk>
+
 MK_SSP=		no
 WARNS?=	2
 
 LDFLAGS+=	-nodefaultlibs
 LIBADD+=	c
-VERSION_MAP=	${.CURDIR}/Version.map
+
+.if ${MK_SYMVER} == "yes"
+VERSION_DEF=	${.CURDIR}/Versions.def
+SYMBOL_MAPS=	${.CURDIR}/Symbol.map
+# Export ARM AEABI unwind routines needed by libc and libthr.
+.if exists(${.CURDIR}/${MACHINE_CPUARCH}/Symbol.map)
+SYMBOL_MAPS+=	${.CURDIR}/${MACHINE_CPUARCH}/Symbol.map
+.endif
+.endif
 
 .include "../libcompiler_rt/Makefile.inc"
 .include "../libgcc_eh/Makefile.inc"

lib/libgcc_s/Symbol.map

@@ -3,7 +3,6 @@
  */
 
 GCC_3.0 {
-global:
 	__absvdi2;
 	__absvsi2;
 	__addvdi3;
@@ -84,8 +83,6 @@ global:
 	_Unwind_Resume;
 	_Unwind_SetGR;
 	_Unwind_SetIP;
-local:
-	*;
 };
 
 GCC_3.3 {
@@ -93,11 +90,11 @@ GCC_3.3 {
 	_Unwind_FindEnclosingFunction;
 	_Unwind_GetCFA;
 	_Unwind_Resume_or_Rethrow;
-} GCC_3.0;
+};
 
 GCC_3.3.1 {
 	__gcc_personality_v0;
-} GCC_3.3;
+};
 
 GCC_3.4 {
 	__clzdi2;
@@ -112,11 +109,11 @@ GCC_3.4 {
 	__popcountdi2;
 	__popcountsi2;
 	__popcountti2;
-} GCC_3.3.1;
+};
 
 GCC_3.4.2 {
 	__enable_execute_stack;
-} GCC_3.4;
+};
 
 GCC_3.4.4 {
 	__absvti2;
@@ -124,7 +121,7 @@ GCC_3.4.4 {
 	__mulvti3;
 	__negvti2;
 	__subvti3;
-} GCC_3.4.2;
+};
 
 GCC_4.0.0 {
 	__divdc3;
@@ -136,7 +133,7 @@ GCC_4.0.0 {
 	__powidf2;
 	__powisf2;
 	__powixf2;
-} GCC_3.4.4;
+};
 
 GCC_4.2.0 {
 	__floatundidf;
@@ -146,9 +143,9 @@ GCC_4.2.0 {
 	__floatuntisf;
 	__floatuntixf;
 	_Unwind_GetIPInfo;
-} GCC_4.0.0;
+};
 
 GCC_4.3.0 {
 	__bswapdi2;
 	__bswapsi2;
-} GCC_4.2.0;
+};

lib/libgcc_s/Versions.def

@@ -0,0 +1,31 @@
+# $FreeBSD$
+
+GCC_3.0 {
+};
+
+GCC_3.3 {
+} GCC_3.0;
+
+GCC_3.3.1 {
+} GCC_3.3;
+
+GCC_3.4 {
+} GCC_3.3.1;
+
+GCC_3.4.2 {
+} GCC_3.4;
+
+GCC_3.4.4 {
+} GCC_3.4.2;
+
+GCC_3.5 {
+} GCC_3.4.4;
+
+GCC_4.0.0 {
+} GCC_3.5;
+
+GCC_4.2.0 {
+} GCC_4.0.0;
+
+GCC_4.3.0 {
+} GCC_4.2.0;

lib/libgcc_s/arm/Symbol.map

@@ -0,0 +1,12 @@
+/*
+ * $FreeBSD$
+ */
+
+GCC_3.5 {
+	_Unwind_VRS_Get;
+	_Unwind_VRS_Set;
+	__aeabi_unwind_cpp_pr0;
+	__aeabi_unwind_cpp_pr1;
+	__aeabi_unwind_cpp_pr2;
+	__gnu_unwind_frame;
+};