Re-add ALLOW_MIPS_SHARED_TEXTREL, sprinkle it around

Diff partially stolen from CheriBSD; these bits need -Wl,-z,notext in order
to build in an LLVM world. They are needed for all flavors/sizes of MIPS.
This will eventually get fixed in LLVM, but it's unclear when.

Reported by:	arichardson, emaste
Differential Revision:	https://reviews.freebsd.org/D21696

lib/csu/tests/dso/Makefile

@@ -5,6 +5,8 @@ SHLIB=		h_csu
 SHLIB_NAME=	libh_csu.so
 SHLIB_MAJOR=	1
 
+ALLOW_MIPS_SHARED_TEXTREL=
+
 WITHOUT_STATIC=
 WITHOUT_PROFILE=
 WITHOUT_PIC=

lib/libc++/Makefile

@@ -11,6 +11,8 @@ CXXINCLUDEDIR=	${INCLUDEDIR}/c++/v${SHLIB_MAJOR}
 STATIC_CXXFLAGS+= -mlong-calls
 .endif
 
+ALLOW_MIPS_SHARED_TEXTREL=
+
 .PATH: ${SRCDIR}
 
 LIB=		c++

lib/libcxxrt/Makefile

@@ -5,6 +5,7 @@ SRCDIR=		${SRCTOP}/contrib/libcxxrt
 
 SHLIB_MAJOR=	1
 SHLIBDIR?=	/lib
+ALLOW_MIPS_SHARED_TEXTREL=
 
 .PATH: ${SRCDIR}
 

lib/libgcc_eh/Makefile.inc

@@ -6,6 +6,8 @@ UNWINDSRCDIR=	${SRCTOP}/contrib/libunwind/src
 
 STATIC_CFLAGS+=${PICFLAG} -fvisibility=hidden -DVISIBILITY_HIDDEN
 
+ALLOW_MIPS_SHARED_TEXTREL=
+
 .PATH: ${COMPILERRTDIR}/lib/builtins
 .PATH: ${UNWINDSRCDIR}
 SRCS_EXC+=	gcc_personality_v0.c

lib/libpmc/Makefile

@@ -5,6 +5,8 @@ LIB=	pmc
 SRCS=	libpmc.c pmclog.c libpmc_pmu_util.c libpmc_json.cc
 INCS=	pmc.h pmclog.h pmcformat.h
 
+ALLOW_MIPS_SHARED_TEXTREL=
+
 .if ${MACHINE_ARCH} == "amd64" || ${MACHINE_ARCH} == "i386"
 
 .if ${MACHINE_ARCH} == "aarch64"

share/mk/bsd.lib.mk

@@ -287,6 +287,10 @@ CLEANFILES+=	${SOBJS}
 .if defined(SHLIB_NAME)
 _LIBS+=		${SHLIB_NAME}
 
+.if ${CFLAGS:M-fexceptions} || defined(SHLIB_CXX) || defined(LIB_CXX)
+ALLOW_MIPS_SHARED_TEXTREL=
+.endif
+
 SOLINKOPTS+=	-shared -Wl,-x
 .if defined(LD_FATAL_WARNINGS) && ${LD_FATAL_WARNINGS} == "no"
 SOLINKOPTS+=	-Wl,--no-fatal-warnings
@@ -295,6 +299,15 @@ SOLINKOPTS+=	-Wl,--fatal-warnings
 .endif
 SOLINKOPTS+=	-Wl,--warn-shared-textrel
 
+.if defined(ALLOW_MIPS_SHARED_TEXTREL) && ${MACHINE_CPUARCH:Mmips}
+# Check if we should be defining ALLOW_SHARED_TEXTREL... basically, C++
+# or -fexceptions in CFLAGS on MIPS.  This works around clang/lld attempting
+# to generate text relocations in read-only .eh_frame.  A future version of
+# clang/lld should instead transform them into relative references at link
+# time, and then we can stop doing this.
+SOLINKOPTS+=	-Wl,-z,notext
+.endif
+
 .if target(beforelinking)
 beforelinking: ${SOBJS}
 ${SHLIB_NAME_FULL}: beforelinking