kpatch/LoongArch: fix kernel panic by disabling direct-extern-access for livepatches

On LoongArch systems, livepatch modules containing references to global
variables trigger kernel panics when the core kernel is built with
-mdirect-extern-access optimization.

Root cause:
The -mdirect-extern-access optimization replaces GOT-based symbol access
with direct addressing. While this improves performance, it breaks the
module loading mechanism which relies on GOT entries for proper symbol
relocation. Direct access to global variables from livepatch modules
causes invalid memory accesses and kernel panics.

Solution:
For LoongArch kpatch builds, conditionally disable direct-extern-access
by adding:
- -mno-direct-extern-access for GCC builds
- -fno-direct-access-external-data for Clang builds

Signed-off-by: george <[email protected]>

Author: georgejguo

kpatch-build/kpatch-build

@@ -61,6 +61,7 @@ KLP_REPLACE=1
 
 GCC="${CROSS_COMPILE:-}gcc"
 CLANG="${CROSS_COMPILE:-}clang"
+CC_OPTION=""
 LD="${CROSS_COMPILE:-}ld"
 LLD="${CROSS_COMPILE:-}ld.lld"
 READELF="${CROSS_COMPILE:-}readelf"
@@ -382,6 +383,21 @@ clang_version_check() {
 	return
 }
 
+cc_option_check() {
+	local option="$1"
+	local compiler=""
+
+	if [[ -n "$CONFIG_CC_IS_CLANG" ]]; then
+	    compiler="$CLANG"
+	else
+	    compiler="$GCC"
+	fi
+
+	if $compiler -Werror "$option" -c -x c /dev/null -o /dev/null 2>/dev/null; then
+		CC_OPTION+=" $option";
+	fi
+}
+
 find_special_section_data() {
 	local -A check
 
@@ -1291,7 +1307,15 @@ declare -a MAKEVARS
 if [[ -n "$CONFIG_CC_IS_CLANG" ]]; then
 	MAKEVARS+=("CC=${KPATCH_CC_PREFIX}${CLANG}")
 	MAKEVARS+=("HOSTCC=clang")
+	if [[ "$ARCH" = "loongarch64" ]]; then
+		cc_option_check "-fno-direct-access-external-data"
+		MAKEVARS+=("KBUILD_CFLAGS_KERNEL+=${CC_OPTION}")
+	fi
 else
+	if [[ "$ARCH" = "loongarch64" ]]; then
+		cc_option_check "-mno-direct-extern-access"
+		MAKEVARS+=("KBUILD_CFLAGS_KERNEL+=${CC_OPTION}")
+	fi
 	MAKEVARS+=("CC=${KPATCH_CC_PREFIX}${GCC}")
 fi