From: George Guo <[email protected]> Add architecture-specific -fPIC compiler flag for LoongArch64 to prevent kernel panics when applying livepatches containing references to symbols defined in the same compilation unit.
Root cause: In the KLP workflow, when a function is livepatched, it's extracted from the original object file and compiled into a separate kernel module. When the patched function references symbols defined in the same compilation unit (like 'uts_sem' in kernel/sys.c), these references break if not compiled as position-independent code. On LoongArch64, without -fPIC, references to same-compilation-unit symbols use absolute addressing that assumes fixed memory locations. When the function is relocated into the livepatch module, these absolute addresses become invalid, causing kernel panics. Example failure case: - SYSCALL_DEFINE1(newuname) references the same-compilation-unit symbol 'uts_sem' - When kpatch extracts this function into a module, the reference to 'uts_sem' must be properly relocated - Without -fPIC, the absolute address reference causes invalid memory access and kernel panic Solution: Force -fPIC compilation for all LoongArch64 KLP builds. This ensures that references to same-compilation-unit symbols use position-independent addressing, allowing proper relocation by the kernel module loader and preventing kernel panics in livepatch scenarios. Co-developed-by: Kexin Liu <[email protected]> Signed-off-by: Kexin Liu <[email protected]> Signed-off-by: George Guo <[email protected]> --- scripts/livepatch/klp-build | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/scripts/livepatch/klp-build b/scripts/livepatch/klp-build index 529437d75346..83a43e0df3b9 100755 --- a/scripts/livepatch/klp-build +++ b/scripts/livepatch/klp-build @@ -543,8 +543,10 @@ fix_patches() { clean_kernel() { local cmd=() local ARCH_KBUILD_CFLAGS_KERNEL="" + local ARCH_KCFLAGS="" if [[ -v CONFIG_LOONGARCH && "$CONFIG_LOONGARCH" == "y" ]]; then + ARCH_KCFLAGS="-fPIC" if [[ -n "$CONFIG_CC_IS_CLANG" ]]; then ARCH_KBUILD_CFLAGS_KERNEL="-fno-direct-access-external-data" else @@ -592,7 +594,7 @@ build_kernel() { cmd+=("-s") fi cmd+=("-j$JOBS") - cmd+=("KCFLAGS=-ffunction-sections -fdata-sections") + cmd+=("KCFLAGS=-ffunction-sections -fdata-sections $ARCH_KCFLAGS") cmd+=("KBUILD_CFLAGS_KERNEL=$ARCH_KBUILD_CFLAGS_KERNEL") cmd+=("vmlinux") cmd+=("modules") -- 2.25.1
