kpatch-build: clang support

Add support for clang-built kernels. This is completely automatic, we
check if the kernel was built with clang by looking for
CONFIG_CC_IS_CLANG in config.

This has almost no effect on non-clang built kernels with one exception:
we now do compliler checks _after_ we download kernel sources which is a
waste of resources in case when compilers don't match.

Signed-off-by: Artem Savkov <asavkov@redhat.com>

Makefile

@@ -62,7 +62,7 @@ vagrant-integration-quick:
 	$(MAKE) -C $(INTEGRATION_DIR) vagrant-quick
 
 check:
-	shellcheck kpatch/kpatch kpatch-build/kpatch-build kpatch-build/kpatch-gcc
+	shellcheck kpatch/kpatch kpatch-build/kpatch-build kpatch-build/kpatch-cc
 	shellcheck test/difftree.sh test/integration/kpatch-test		\
 		   test/integration/lib.sh test/integration/rebase-patches	\
 		   test/integration/test-vagrant				\

kpatch-build/Makefile

@@ -40,7 +40,7 @@ $(PLUGIN): gcc-plugins/ppc64le-plugin.c
 
 install: all
 	$(INSTALL) -d $(LIBEXECDIR)
-	$(INSTALL) $(TARGETS) kpatch-gcc $(LIBEXECDIR)
+	$(INSTALL) $(TARGETS) kpatch-cc $(LIBEXECDIR)
 	$(INSTALL) -d $(BINDIR)
 	$(INSTALL) kpatch-build $(BINDIR)
 

kpatch-build/kpatch-build

@@ -49,7 +49,7 @@ LOGFILE="$CACHEDIR/build.log"
 RELEASE_FILE=/etc/os-release
 DEBUG=0
 SKIPCLEANUP=0
-SKIPGCCCHECK=0
+SKIPCOMPILERCHECK=0
 ARCH_KCFLAGS=""
 DEBUG_KCFLAGS=""
 declare -a PATCH_LIST
@@ -219,10 +219,11 @@ find_core_symvers() {
 }
 
 gcc_version_from_file() {
-	readelf -p .comment "$1" | grep -o 'GCC:.*' | head -n 1
+	readelf -p .comment "$1" | grep -m 1 -o 'GCC:.*'
 }
 
 gcc_version_check() {
+	local target="$1"
 	local c="$TEMPDIR/test.c" o="$TEMPDIR/test.o"
 	local out gccver kgccver
 
@@ -231,11 +232,7 @@ gcc_version_check() {
 	echo 'void main(void) {}' > "$c"
 	out="$(gcc -c -pg -ffunction-sections -o "$o" "$c" 2>&1)"
 	gccver="$(gcc_version_from_file "$o")"
-	if [[ -n "$OOT_MODULE" ]]; then
+	kgccver="$(gcc_version_from_file "$target")"
-		kgccver="$(gcc_version_from_file "$OOT_MODULE")"
-	else
-		kgccver="$(gcc_version_from_file "$VMLINUX")"
-	fi
 
 	if [[ -n "$out" ]]; then
 		warn "gcc >= 4.8 required for -pg -ffunction-settings"
@@ -254,7 +251,31 @@ gcc_version_check() {
 		warn "gcc/kernel version mismatch"
 		echo "gcc version:    $gccver"
 		echo "kernel version: $kgccver"
-		echo "Install the matching gcc version (recommended) or use --skip-gcc-check"
+		echo "Install the matching gcc version (recommended) or use --skip-compiler-check"
+		echo "to skip the version matching enforcement (not recommended)"
+		return 1
+	fi
+
+	return
+}
+
+clang_version_from_file() {
+	readelf -p .comment "$1" | grep -m 1 -Eo 'clang version [0-9.]+'
+}
+
+clang_version_check() {
+	local target="$1"
+	local clangver kclangver
+
+	clangver=$(clang --version | grep -m 1 -Eo 'clang version [0-9.]+')
+	kclangver="$(clang_version_from_file "$target")"
+
+	# ensure clang version matches that used to build the kernel
+	if [[ "$clangver" != "$kclangver" ]]; then
+		warn "clang/kernel version mismatch"
+		echo "clang version:    $clangver"
+		echo "kernel version:   $kclangver"
+		echo "Install the matching clang version (recommended) or use --skip-compiler-check"
 		echo "to skip the version matching enforcement (not recommended)"
 		return 1
 	fi
@@ -456,11 +477,11 @@ usage() {
 	echo "		-e, --oot-module        Enable patching out-of-tree module," >&2
 	echo "		                        specify current version of module" >&2
 	echo "		--skip-cleanup          Skip post-build cleanup" >&2
-	echo "		--skip-gcc-check   Skip gcc version matching check" >&2
+	echo "		--skip-compiler-check   Skip compiler version matching check" >&2
 	echo "		                        (not recommended)" >&2
 }
 
-options="$(getopt -o ha:r:s:c:v:j:t:n:o:de: -l "help,archversion:,sourcerpm:,sourcedir:,config:,vmlinux:,jobs:,target:,name:,output:,oot-module:,debug,skip-gcc-check,skip-cleanup" -- "$@")" || die "getopt failed"
+options="$(getopt -o ha:r:s:c:v:j:t:n:o:de: -l "help,archversion:,sourcerpm:,sourcedir:,config:,vmlinux:,jobs:,target:,name:,output:,oot-module:,debug,skip-gcc-check,skip-compiler-check,skip-cleanup" -- "$@")" || die "getopt failed"
 
 eval set -- "$options"
 
@@ -528,8 +549,11 @@ while [[ $# -gt 0 ]]; do
 		SKIPCLEANUP=1
 		;;
 	--skip-gcc-check)
-		echo "WARNING: Skipping gcc version matching check (not recommended)"
+		echo "DEPRECATED: --skip-gcc-check is deprecated, use --skip-compiler-check instead"
-		SKIPGCCCHECK=1
+		;&
+	--skip-compiler-check)
+		echo "WARNING: Skipping compiler version matching check (not recommended)"
+		SKIPCOMPILERCHECK=1
 		;;
 	*)
 		[[ "$1" = "--" ]] && shift && continue
@@ -631,10 +655,6 @@ fi
 
 find_dirs || die "can't find supporting tools"
 
-if [[ "$SKIPGCCCHECK" -eq 0 ]]; then
-	gcc_version_check || die
-fi
-
 if [[ -n "$USERSRCDIR" ]]; then
 	echo "Using source directory at $USERSRCDIR"
 
@@ -751,6 +771,8 @@ CONFIG_PARAVIRT=0
 CONFIG_UNWINDER_ORC=0
 CONFIG_JUMP_LABEL=0
 CONFIG_MODVERSIONS=0
+CONFIG_CC_IS_CLANG=0
+CONFIG_LD_IS_LLD=0
 
 if grep -q "CONFIG_LIVEPATCH=y" "$CONFIGFILE" && (kernel_is_rhel || kernel_version_gte 4.9.0); then
 
@@ -777,6 +799,8 @@ grep -q "CONFIG_PARAVIRT=y"     "$CONFIGFILE" && CONFIG_PARAVIRT=1
 grep -q "CONFIG_UNWINDER_ORC=y" "$CONFIGFILE" && CONFIG_UNWINDER_ORC=1
 grep -q "CONFIG_JUMP_LABEL=y"   "$CONFIGFILE" && CONFIG_JUMP_LABEL=1
 grep -q "CONFIG_MODVERSIONS=y"  "$CONFIGFILE" && CONFIG_MODVERSIONS=1
+grep -q "CONFIG_CC_IS_CLANG=y"  "$CONFIGFILE" && CONFIG_CC_IS_CLANG=1
+grep -q "CONFIG_LD_IS_LLD=y"    "$CONFIGFILE" && CONFIG_LD_IS_LLD=1
 
 # unsupported kernel option checking
 grep -q "CONFIG_DEBUG_INFO_SPLIT=y" "$CONFIGFILE" && die "kernel option 'CONFIG_DEBUG_INFO_SPLIT' not supported"
@@ -791,6 +815,23 @@ if grep -q "CONFIG_DEBUG_INFO_BTF=y" "$CONFIGFILE" ; then
 	sed -i 's/CONFIG_DEBUG_INFO_BTF/DISABLED_FOR_KPATCH_BUILD/g' "$SRCDIR"/scripts/link-vmlinux.sh || die
 fi
 
+if [[ "$CONFIG_CC_IS_CLANG" -eq 1 ]]; then
+	echo "WARNING: Clang support is experimental"
+fi
+
+if [[ "$SKIPCOMPILERCHECK" -eq 0 ]]; then
+	if [[ -n "$OOT_MODULE" ]]; then
+		target="$OOT_MODULE"
+	else
+		target="$VMLINUX"
+	fi
+	if [[ "$CONFIG_CC_IS_CLANG" -eq 0 ]]; then
+		gcc_version_check "$target" || die
+	else
+		clang_version_check "$target" || die
+	fi
+fi
+
 echo "Testing patch file(s)"
 cd "$SRCDIR" || die
 verify_patch_files
@@ -816,9 +857,27 @@ fi
 echo "Building original source"
 [[ -n "$OOT_MODULE" ]] || ./scripts/setlocalversion --save-scmversion || die
 unset KPATCH_GCC_TEMPDIR
+
+KPATCH_CC_PREFIX="$TOOLSDIR/kpatch-cc "
+declare -a MAKEVARS
+if [ "$CONFIG_CC_IS_CLANG" -eq 1 ]; then
+	MAKEVARS+=("CC=${KPATCH_CC_PREFIX}clang")
+	MAKEVARS+=("HOSTCC=clang")
+else
+	MAKEVARS+=("CC=${KPATCH_CC_PREFIX}gcc")
+fi
+
+if [ "$CONFIG_LD_IS_LLD" -eq 1 ]; then
+	MAKEVARS+=("LD=${KPATCH_CC_PREFIX}ld.lld")
+	MAKEVARS+=("HOSTLD=ld.lld")
+else
+	MAKEVARS+=("LD=${KPATCH_CC_PREFIX}ld")
+fi
+
+
 # $TARGETS used as list, no quotes.
 # shellcheck disable=SC2086
-CROSS_COMPILE="$TOOLSDIR/kpatch-gcc " make "-j$CPUS" $TARGETS 2>&1 | logger || die
+make "${MAKEVARS[@]}" "-j$CPUS" $TARGETS 2>&1 | logger || die
 
 # Save original module symvers
 cp -f "$SRCDIR/Module.symvers" "$TEMPDIR/Module.symvers" || die
@@ -832,9 +891,7 @@ KPATCH_GCC_SRCDIR="$SRCDIR"
 export KPATCH_GCC_SRCDIR
 # $TARGETS used as list, no quotes.
 # shellcheck disable=SC2086
-CROSS_COMPILE="$TOOLSDIR/kpatch-gcc " \
+KBUILD_MODPOST_WARN=1 make "${MAKEVARS[@]}" "-j$CPUS" $TARGETS 2>&1 | logger || die
-	KBUILD_MODPOST_WARN=1 \
-	make "-j$CPUS" $TARGETS 2>&1 | logger || die
 
 # source.c:(.section+0xFF): undefined reference to `symbol'
 grep "undefined reference" "$LOGFILE" | sed -r "s/^.*\`(.*)'$/\\1/" \
@@ -1026,10 +1083,16 @@ if [[ -z "$OOT_MODULE" ]]; then
 else
 	KPATCH_BUILD="/lib/modules/$ARCHVERSION/build"
 fi
+
+# We no longer need kpatch-cc
+for ((idx=0; idx<${#MAKEVARS[@]}; idx++)); do
+    MAKEVARS[$idx]=${MAKEVARS[$idx]/${KPATCH_CC_PREFIX}/}
+done
+
 KPATCH_BUILD="$KPATCH_BUILD" KPATCH_NAME="$MODNAME" \
 KBUILD_EXTRA_SYMBOLS="$KBUILD_EXTRA_SYMBOLS" \
 KPATCH_LDFLAGS="$KPATCH_LDFLAGS" \
-	make 2>&1 | logger || die
+	make "${MAKEVARS[@]}" 2>&1 | logger || die
 
 if [[ "$USE_KLP" -eq 1 ]]; then
 	if [[ "$USE_KLP_ARCH" -eq 0 ]]; then

kpatch-build/kpatch-cc

@@ -13,7 +13,7 @@ fi
 
 declare -a args=("$@")
 
-if [[ "$TOOLCHAINCMD" =~ "gcc" ]] ; then
+if [[ "$TOOLCHAINCMD" =~ ^(.*-)?gcc$ || "$TOOLCHAINCMD" =~ ^(.*-)?clang$ ]] ; then
 	while [ "$#" -gt 0 ]; do
 		if [ "$1" = "-o" ]; then
 			obj="$2"
@@ -61,7 +61,7 @@ if [[ "$TOOLCHAINCMD" =~ "gcc" ]] ; then
 		fi
 		shift
 	done
-elif [[ "$TOOLCHAINCMD" = "ld" ]] ; then
+elif [[ "$TOOLCHAINCMD" =~ ^(.*-)?ld || "$TOOLCHAINCMD" =~ ^(.*-)?ld.lld ]] ; then
 	while [ "$#" -gt 0 ]; do
 		if [ "$1" = "-o" ]; then
 			obj="$2"

man/kpatch-build.1

@@ -54,12 +54,12 @@ effect.
 --skip-cleanup
    Skip post-build cleanup
 
---skip-gcc-check
+--skip-compiler-check
-   Skips check that ensures that the system gcc version and
+   Skips check that ensures that the system compiler version and
-   the gcc version that built the kernel match.  Skipping this
+   the compiler version that built the kernel match.  Skipping this
-   check is not recommended, but is useful if the exact gcc
+   check is not recommended, but is useful if the exact compiler
    version is not available or is not easily installed. Use
-   only when confident that the two versions of gcc output
+   only when confident that the two versions of compiler output
    identical objects for a given target.  Otherwise, use of
    this option might result in unexpected changed objects
    being detected.