This series adds LoongArch support for the klp-build livepatch tooling,
enabling automated livepatch module generation using objtool on
LoongArch.
It is based on Josh Poimboeuf's klp-build series [1] (see base-commit
below) and extends it with the LoongArch-specific objtool and build
pieces, plus a few LoongArch toolchain/relocation fixes required to make
livepatch modules load and run correctly.
Overview (the feature is wired up last so the series stays bisectable:
objtool's KLP arch hooks are all in place before ARCH_HAS_KLP is turned
on):
- Patches 1 and 6 add the objtool hooks LoongArch needs:
arch_adjusted_addend() and arch_jump_opcode_bytes() (the latter makes
klp checksums for jump/call instructions position-independent,
mirroring x86/arm64).
- Patch 2 marks the special sections so objtool can split them into
per-entry symbols: SHF_MERGE entry sizes for the read-only
.altinstructions/__ex_table, and ANNOTATE_DATA_SPECIAL for the
writable __bug_table/__jump_table.
- Patches 3-4 fix kernel panics seen when loading livepatch modules,
caused by LoongArch code-generation/relocation assumptions:
* disable -mdirect-extern-access for klp builds (the module loader
relies on GOT entries for external symbol references),
* build with -fPIC so same-compilation-unit symbol references stay
GOT-indirect and can be relocated into the livepatch module
(-fPIE is not enough: it emits direct, non-GOT references).
- Patch 5 fixes EFI linking when building with -fdata-sections.
- Patch 7 adds KLP_SYSCALL_DEFINEx() support for LoongArch.
- Patch 8 wires up LoongArch klp-build (selects HAVE_KLP_BUILD and
enables objtool's KLP support).
Testing:
- objtool builds cleanly for LoongArch.
- Livepatch modules were generated and loaded on a LoongArch machine;
the panics addressed by patches 3-4 no longer reproduce.
Changes since v1 [2]:
- Mark the writable special sections (__bug_table, __jump_table) with
ANNOTATE_DATA_SPECIAL instead of SHF_MERGE+entsize, which is invalid
for writable sections and rejected by Clang; SHF_MERGE is kept only
for the read-only .altinstructions/__ex_table. Also dropped a
redundant asm-offsets.h include in head.S. (WangYuli)
- Rewrote the -fPIC commit message: the root cause is GOT indirection,
not "absolute addressing". With CONFIG_RELOCATABLE=y the kernel is
already built -fPIE, yet -fPIE still emits direct, non-GOT references
for same-compilation-unit symbols, so -fPIC is required. (Xi Ruoyao)
- Set the LoongArch CFLAGS in build_kernel(), where the variables are
actually used; in v1 they were in clean_kernel() and had no effect.
(WangYuli)
- Gated the klp-build changes on CONFIG_RELOCATABLE=y and
CONFIG_AS_HAS_EXPLICIT_RELOCS=y, and only override KBUILD_CFLAGS_KERNEL
when needed, so other arches/configs are unaffected.
- Reordered the series so the enabling patch ("Add livepatch build (KLP)
support") comes last, keeping every commit buildable/bisectable.
Patch numbers therefore differ from v1.
[1]
https://git.kernel.org/pub/scm/linux/kernel/git/jpoimboe/linux.git/log/?h=klp-build-arm64
[2] https://lore.kernel.org/all/[email protected]/
George Guo (8):
objtool/LoongArch: Add arch_adjusted_addend() for KLP support
LoongArch: Mark special sections for KLP support
livepatch/klp-build: disable direct-extern-access for LoongArch to fix
kernel panic
livepatch/klp-build: build LoongArch with -fPIC to keep GOT-indirect
symbol references
LoongArch: Fix EFI linking with -fdata-sections
objtool/klp: Add LoongArch jump opcode bytes support
klp-build: Add LoongArch syscall patching macro
LoongArch: Add livepatch build (KLP) support
arch/loongarch/Kconfig | 1 +
arch/loongarch/include/asm/alternative-asm.h | 5 ++-
arch/loongarch/include/asm/alternative.h | 6 ++-
arch/loongarch/include/asm/asm-extable.h | 10 ++++-
arch/loongarch/include/asm/bug.h | 1 +
arch/loongarch/include/asm/jump_label.h | 2 +
arch/loongarch/kernel/asm-offsets.c | 20 +++++++++
arch/loongarch/kernel/vmlinux.lds.S | 2 +-
include/linux/livepatch_helpers.h | 22 ++++++++++
scripts/livepatch/klp-build | 36 ++++++++++++++-
tools/objtool/Makefile | 3 +-
tools/objtool/arch/loongarch/decode.c | 46 ++++++++++++++++++++
12 files changed, 145 insertions(+), 9 deletions(-)
base-commit: 85afaba140a4b9f20fe8c8a64b24fc85f022d981
--
2.25.1
