Allow using sanitizers for ssp tests with out-of-tree compiler

With an out-of-tree Clang, we can use the -resource-dir flag when linking
to point it at the runtime libraries from the current SYSROOT.
This moves the path to the clang-internal library directory to a separate
.mk file that can be used by Makefiles that want to find the sanitizer
libraries. I intend to re-use this .mk file for my upcoming changes that
allow building the entire base system with ASAN/UBSAN/MSAN.

Reviewed By:	dim
Differential Revision: https://reviews.freebsd.org/D28852

lib/libc/tests/ssp/Makefile

@@ -6,9 +6,10 @@ MK_WERROR=	no
 WARNS?=	2
 
 CFLAGS.h_raw+=	-fstack-protector-all -Wstack-protector
-.if ${COMPILER_TYPE} == "clang" && ${CC} == "cc"
-# Only use -fsanitize=bounds when using the in-tree compiler.  Otherwise
-# we may link to a sanitizer library targeted at a newer kernel/libc.
+.if ${COMPILER_TYPE} == "clang"
+# Only use -fsanitize=bounds when using clang. Otherwise we are not able to
+# override the sanitizer runtime libraries to be the ones installed on the
+# target system.
 CFLAGS.h_raw+=	-fsanitize=bounds
 .elif ${COMPILER_TYPE} == "gcc"
 CFLAGS.h_raw+=	--param ssp-buffer-size=1
@@ -25,24 +26,20 @@ PROGS+=		h_getcwd
 PROGS+=		h_memcpy
 PROGS+=		h_memmove
 PROGS+=		h_memset
-# This testcase doesn't run properly when not compiled with -fsantize=bounds
-# with clang, which is currently contingent on a compiler_rt update
-#
 # XXX: the h_raw/h_read testcases don't cause a SIGABRT with in-tree gcc right
 # now on amd64 when it trips the stack bounds specified in t_ssp.sh . This
 # probably needs to be fixed as it's currently hardcoded.
-#
-# sanitizer is not tested or supported for ARM right now. sbruno
-.if ${COMPILER_TYPE} == "clang" && ${CC} == "cc" && !defined(_SKIP_BUILD) && \
+.if ${COMPILER_TYPE} == "clang" && !defined(_SKIP_BUILD) && \
     (!defined(_RECURSING_PROGS) || ${PROG} == "h_raw")
-.if !defined(_CLANG_RESOURCE_DIR)
-_CLANG_RESOURCE_DIR!=	${CC:N${CCACHE_BIN}} -print-resource-dir
-.export _CLANG_RESOURCE_DIR
-.endif
-_libclang_rt_arch=	${MACHINE_ARCH:S/amd64/x86_64/:C/hf$//:S/mipsn32/mips64/}
-_libclang_rt_ubsan=	${_CLANG_RESOURCE_DIR}/lib/freebsd/libclang_rt.ubsan_standalone-${_libclang_rt_arch}.a
+.include "${SRCTOP}/lib/libclang_rt/compiler-rt-vars.mk"
+_libclang_rt_ubsan=	${SYSROOT}${SANITIZER_LIBDIR}/libclang_rt.ubsan_standalone-${CRTARCH}.a
 .if exists(${_libclang_rt_ubsan})
 PROGS+=		h_raw
+LDADD.h_raw+=	${SANITIZER_LDFLAGS}
+.else
+.if make(all)
+.info "Could not find runtime library ${_libclang_rt_ubsan}, skipping h_raw"
+.endif
 .endif
 .endif
 PROGS+=		h_read

lib/libclang_rt/Makefile.inc

@@ -2,20 +2,12 @@
 
 .include <bsd.compiler.mk>
 
-# armv[67] is a bit special since we allow a soft-floating version via
-# CPUTYPE matching *soft*. This variant may not actually work though.
-.if ${MACHINE_ARCH:Marmv[67]*} != "" && \
-    (!defined(CPUTYPE) || ${CPUTYPE:M*soft*} == "")
-CRTARCH?=	armhf
-.else
-CRTARCH?=	${MACHINE_ARCH:C/amd64/x86_64/}
-.endif
 CRTSRC=		${SRCTOP}/contrib/llvm-project/compiler-rt
+.include "compiler-rt-vars.mk"
 
 .PATH:		${CRTSRC}/lib
 
-CLANGDIR=	/usr/lib/clang/11.0.1
-LIBDIR=		${CLANGDIR}/lib/freebsd
+LIBDIR=		${SANITIZER_LIBDIR}
 SHLIBDIR=	${LIBDIR}
 
 NO_PIC=

lib/libclang_rt/compiler-rt-vars.mk

@@ -0,0 +1,24 @@
+CLANG_SUBDIR=clang/11.0.1
+CLANGDIR=	/usr/lib/${CLANG_SUBDIR}
+SANITIZER_LIBDIR=		${CLANGDIR}/lib/freebsd
+
+# armv[67] is a bit special since we allow a soft-floating version via
+# CPUTYPE matching *soft*. This variant may not actually work though.
+.if ${MACHINE_ARCH:Marmv[67]*} != "" && \
+    (!defined(CPUTYPE) || ${CPUTYPE:M*soft*} == "")
+CRTARCH?=	armhf
+.else
+CRTARCH?=	${MACHINE_ARCH:S/amd64/x86_64/:C/hf$//:S/mipsn32/mips64/}
+.endif
+
+.if ${COMPILER_TYPE} == "clang"
+# The only way to set the path to the sanitizer libraries with clang is to
+# override the resource directory.
+# Note: lib/freebsd is automatically appended to the -resource-dir value.
+SANITIZER_LDFLAGS=	-resource-dir=${SYSROOT}${CLANGDIR}
+# Also set RPATH to ensure that the dynamically linked runtime libs are found.
+SANITIZER_LDFLAGS+=	-Wl,--enable-new-dtags
+SANITIZER_LDFLAGS+=	-Wl,-rpath,${SANITIZER_LIBDIR}
+.else
+.error "Unknown link flags for -fsanitize=... COMPILER_TYPE=${COMPILER_TYPE}"
+.endif