[PATCH v2 0/8] LoongArch: Add livepatch build (KLP) support

[PATCH v2 0/8] LoongArch: Add livepatch build (KLP) support

[George Guo]

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/20260604065317.219777-1-dongtai.guo@linux.dev/

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

[PATCH v2 1/8] objtool/LoongArch: Add arch_adjusted_addend() for KLP support

[George Guo]

From: George Guo <guodongtai@kylinos.cn>

Implement arch_adjusted_addend() to return the relocation addend value.

Co-developed-by: Kexin Liu <liukexin@kylinos.cn>
Signed-off-by: Kexin Liu <liukexin@kylinos.cn>
Signed-off-by: George Guo <guodongtai@kylinos.cn>
---
 tools/objtool/arch/loongarch/decode.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tools/objtool/arch/loongarch/decode.c b/tools/objtool/arch/loongarch/decode.c
index 6cd288150f49..674e4efd138f 100644
--- a/tools/objtool/arch/loongarch/decode.c
+++ b/tools/objtool/arch/loongarch/decode.c
@@ -34,6 +34,11 @@ s64 arch_insn_adjusted_addend(struct instruction *insn, struct reloc *reloc)
 	return reloc_addend(reloc);
 }
 
+u64 arch_adjusted_addend(struct reloc *reloc)
+{
+	return reloc_addend(reloc);
+}
+
 bool arch_pc_relative_reloc(struct reloc *reloc)
 {
 	return false;
-- 
2.25.1

[PATCH v2 2/8] LoongArch: Mark special sections for KLP support

[George Guo]

From: George Guo <guodongtai@kylinos.cn>

objtool needs to split the kernel's special sections into per-entry
symbols when generating livepatch modules. Mark them so it can:

 - .altinstructions and __ex_table are read-only, so set an explicit
   entry size via SHF_MERGE (ALT_INSTR_SIZE / EXTABLE_SIZE).

 - __bug_table and __jump_table are writable. SHF_MERGE cannot be
   combined with SHF_WRITE (Clang rejects it), so annotate each entry
   with ANNOTATE_DATA_SPECIAL instead, mirroring x86/arm64.

Co-developed-by: Kexin Liu <liukexin@kylinos.cn>
Signed-off-by: Kexin Liu <liukexin@kylinos.cn>
Signed-off-by: George Guo <guodongtai@kylinos.cn>
---
 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 ++++++++++++++++++++
 6 files changed, 38 insertions(+), 6 deletions(-)

diff --git a/arch/loongarch/include/asm/alternative-asm.h b/arch/loongarch/include/asm/alternative-asm.h
index 7dc29bd9b2f0..d940d9d2c0e1 100644
--- a/arch/loongarch/include/asm/alternative-asm.h
+++ b/arch/loongarch/include/asm/alternative-asm.h
@@ -5,6 +5,7 @@
 #ifdef __ASSEMBLER__
 
 #include <asm/asm.h>
+#include <generated/asm-offsets.h>
 
 /*
  * Issue one struct alt_instr descriptor entry (need to put it into
@@ -33,7 +34,7 @@
 	.fill - (((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)) / 4, 4, 0x03400000
 142 :
 
-	.pushsection .altinstructions, "a"
+	.pushsection .altinstructions, "aM", @progbits, ALT_INSTR_SIZE
 	altinstruction_entry 140b, 143f, \feature, 142b-140b, 144f-143f
 	.popsection
 
@@ -63,7 +64,7 @@
 		(alt_max_short(new_len1, new_len2) - (old_len)) / 4, 4, 0x03400000
 142 :
 
-	.pushsection .altinstructions, "a"
+	.pushsection .altinstructions, "aM", @progbits, ALT_INSTR_SIZE
 	altinstruction_entry 140b, 143f, \feature1, 142b-140b, 144f-143f, 142b-141b
 	altinstruction_entry 140b, 144f, \feature2, 142b-140b, 145f-144f, 142b-141b
 	.popsection
diff --git a/arch/loongarch/include/asm/alternative.h b/arch/loongarch/include/asm/alternative.h
index b5bae21fb3c8..8f7712ed2f4e 100644
--- a/arch/loongarch/include/asm/alternative.h
+++ b/arch/loongarch/include/asm/alternative.h
@@ -70,7 +70,8 @@ extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
 /* alternative assembly primitive: */
 #define ALTERNATIVE(oldinstr, newinstr, feature)			\
 	OLDINSTR(oldinstr, 1)						\
-	".pushsection .altinstructions,\"a\"\n"				\
+	".pushsection .altinstructions, \"aM\", @progbits, "            \
+		 __stringify(ALT_INSTR_SIZE) "\n"                       \
 	ALTINSTR_ENTRY(feature, 1)					\
 	".popsection\n"							\
 	".subsection 1\n" \
@@ -79,7 +80,8 @@ extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
 
 #define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\
 	OLDINSTR_2(oldinstr, 1, 2)					\
-	".pushsection .altinstructions,\"a\"\n"				\
+	".pushsection .altinstructions, \"aM\", @progbits, "            \
+			__stringify(ALT_INSTR_SIZE) "\n"                \
 	ALTINSTR_ENTRY(feature1, 1)					\
 	ALTINSTR_ENTRY(feature2, 2)					\
 	".popsection\n"							\
diff --git a/arch/loongarch/include/asm/asm-extable.h b/arch/loongarch/include/asm/asm-extable.h
index d60bdf2e6377..2d7eef7c0b39 100644
--- a/arch/loongarch/include/asm/asm-extable.h
+++ b/arch/loongarch/include/asm/asm-extable.h
@@ -7,10 +7,15 @@
 #define EX_TYPE_UACCESS_ERR_ZERO	2
 #define EX_TYPE_BPF			3
 
+#ifndef COMPILE_OFFSETS
+#include <asm/asm-offsets.h>
+#endif
+
 #ifdef __ASSEMBLER__
 
 #define __ASM_EXTABLE_RAW(insn, fixup, type, data)	\
-	.pushsection	__ex_table, "a";		\
+	.pushsection    __ex_table, "aM", @progbits,    \
+			EXTABLE_SIZE;                   \
 	.balign		4;				\
 	.long		((insn) - .);			\
 	.long		((fixup) - .);			\
@@ -29,7 +34,8 @@
 #include <asm/gpr-num.h>
 
 #define __ASM_EXTABLE_RAW(insn, fixup, type, data)	\
-	".pushsection	__ex_table, \"a\"\n"		\
+	".pushsection   __ex_table, \"aM\", @progbits, "\
+	 __stringify(EXTABLE_SIZE) "\n"                 \
 	".balign	4\n"				\
 	".long		((" insn ") - .)\n"		\
 	".long		((" fixup ") - .)\n"		\
diff --git a/arch/loongarch/include/asm/bug.h b/arch/loongarch/include/asm/bug.h
index d090a5bec5eb..14e3acbaad8d 100644
--- a/arch/loongarch/include/asm/bug.h
+++ b/arch/loongarch/include/asm/bug.h
@@ -25,6 +25,7 @@
 #define __BUG_ENTRY(cond_str, flags)				\
 		.pushsection __bug_table, "aw";			\
 		.align 2;					\
+		__ANNOTATE_DATA_SPECIAL;				\
 	10000:	.long 10001f - .;				\
 		_BUGVERBOSE_LOCATION(WARN_CONDITION_STR(cond_str) __FILE__, __LINE__) \
 		.short flags;					\
diff --git a/arch/loongarch/include/asm/jump_label.h b/arch/loongarch/include/asm/jump_label.h
index 7ef4ae3abf08..d20f0fa24b6b 100644
--- a/arch/loongarch/include/asm/jump_label.h
+++ b/arch/loongarch/include/asm/jump_label.h
@@ -12,6 +12,7 @@
 #include <linux/types.h>
 #include <linux/stringify.h>
 #include <asm/asm.h>
+#include <linux/objtool.h>
 
 #define HAVE_JUMP_LABEL_BATCH
 
@@ -27,6 +28,7 @@
 #define JUMP_TABLE_ENTRY(key, label)			\
 	 ".pushsection	__jump_table, \"aw\"	\n\t"	\
 	 ".align	" __stringify(PTRLOG) "	\n\t"	\
+	 ANNOTATE_DATA_SPECIAL "\n\t"			\
 	 ".long		1b - ., " label " - .	\n\t"	\
 	 JUMP_LABEL_TYPE  key " - .		\n\t"	\
 	 ".popsection				\n\t"
diff --git a/arch/loongarch/kernel/asm-offsets.c b/arch/loongarch/kernel/asm-offsets.c
index 2cc953f113ac..470323aa022c 100644
--- a/arch/loongarch/kernel/asm-offsets.c
+++ b/arch/loongarch/kernel/asm-offsets.c
@@ -18,6 +18,8 @@
 #include <asm/ftrace.h>
 #include <asm/sigframe.h>
 #include <vdso/datapage.h>
+#include <asm/alternative.h>
+#include <asm/extable.h>
 
 static void __used output_ptreg_defines(void)
 {
@@ -323,3 +325,21 @@ static void __used output_vdso_defines(void)
 	DEFINE(__VDSO_PAGES, VDSO_NR_PAGES);
 	BLANK();
 }
+
+static void __used output_extable_defines(void)
+{
+	COMMENT("LoongArch exception table entry offsets.");
+
+	DEFINE(EXTABLE_SIZE, sizeof(struct exception_table_entry));
+	BLANK();
+}
+
+static void __used output_alt_instr_defines(void)
+{
+	COMMENT("LoongArch alternative instructions offsets.");
+
+	DEFINE(ALT_INSTR_SIZE, sizeof(struct alt_instr));
+	BLANK();
+}
+
+
-- 
2.25.1

[PATCH v2 3/8] livepatch/klp-build: disable direct-extern-access for LoongArch to fix kernel panic

[George Guo]

From: George Guo <guodongtai@kylinos.cn>

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

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

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

See also commit 38b10b269d04 ("LoongArch: Tweak CFLAGS for Clang
compatibility"), which added -mdirect-extern-access to the kernel as a
nice-to-have optimization that reduces GOT accesses.

Note this is passed as a command-line KBUILD_CFLAGS_KERNEL= assignment,
which replaces arch/loongarch/Makefile's KBUILD_CFLAGS_KERNEL wholesale
rather than appending to it. As a side effect it also drops the -fPIE
that the arch adds under CONFIG_RELOCATABLE. That is intentional and
relied upon by the next patch ("LoongArch: ... -fPIC ..."), which adds
-fPIC via KCFLAGS: kbuild applies KBUILD_CFLAGS_KERNEL after KCFLAGS for
built-in objects (see modkern_cflags in scripts/Makefile.lib), so a
retained -fPIE would otherwise win over that -fPIC. The two patches must
stay together.

Co-developed-by: Kexin Liu <liukexin@kylinos.cn>
Signed-off-by: Kexin Liu <liukexin@kylinos.cn>
Signed-off-by: George Guo <guodongtai@kylinos.cn>
---
 scripts/livepatch/klp-build | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/scripts/livepatch/klp-build b/scripts/livepatch/klp-build
index e83973567c87..27fe8824ef12 100755
--- a/scripts/livepatch/klp-build
+++ b/scripts/livepatch/klp-build
@@ -556,6 +556,24 @@ build_kernel() {
 	local log="$TMP_DIR/build.log"
 	local cmd=()
 
+	local ARCH_KBUILD_CFLAGS_KERNEL=""
+
+	if [[ -v CONFIG_LOONGARCH && "$CONFIG_LOONGARCH" == "y" ]]; then
+		# -mdirect-extern-access only exists under explicit relocs, and this
+		# function replaces KBUILD_CFLAGS_KERNEL wholesale (safe only then;
+		# the non-explicit build puts -Wa,-mla-global-with-pcrel there).
+		[[ "${CONFIG_AS_HAS_EXPLICIT_RELOCS:-}" == "y" ]] || \
+			die "LoongArch klp-build requires CONFIG_AS_HAS_EXPLICIT_RELOCS=y"
+
+		if [[ "${CONFIG_CC_IS_CLANG:-}" == "y" ]]; then
+			ARCH_KBUILD_CFLAGS_KERNEL="-fno-direct-access-external-data"
+		else
+			ARCH_KBUILD_CFLAGS_KERNEL="-mno-direct-extern-access"
+		fi
+
+		status "LoongArch detected: adding $ARCH_KBUILD_CFLAGS_KERNEL to KBUILD_CFLAGS_KERNEL"
+	fi
+
 	cmd=("make")
 
 	# When a patch to a kernel module references a newly created unexported
@@ -582,6 +600,7 @@ build_kernel() {
 	fi
 	cmd+=("-j$JOBS")
 	cmd+=("KCFLAGS=-ffunction-sections -fdata-sections")
+	cmd+=("KBUILD_CFLAGS_KERNEL=$ARCH_KBUILD_CFLAGS_KERNEL")
 	cmd+=("vmlinux")
 	cmd+=("modules")
 
-- 
2.25.1

[PATCH v2 4/8] livepatch/klp-build: build LoongArch with -fPIC to keep GOT-indirect symbol references

[George Guo]

From: George Guo <guodongtai@kylinos.cn>

On LoongArch, klp-build livepatch modules panic when a patched function
references a global defined in the same compilation unit (e.g.
SYSCALL_DEFINE1(newuname) -> 'uts_sem' in kernel/sys.c).

With CONFIG_RELOCATABLE=y the kernel is already -fPIE, so this is not
absolute addressing; the problem is GOT indirection. For a same-unit
global, -fPIE emits a direct PC-relative reference (R_LARCH_PCALA_*) and
skips the GOT, while -fPIC routes it through the GOT (R_LARCH_GOT_PC_*).
klp-build extracts the patched function into a separate module while
'uts_sem' stays in the core kernel, and the klp relocation machinery can
only redirect such a cross-object reference through a GOT entry. The
direct -fPIE reference has no GOT slot to fix up, so once the function is
relocated its target is wrong and it faults.

Force -fPIC for LoongArch KLP builds; -fPIE is not enough, as it
optimizes away the very GOT indirection KLP relies on.

This depends on the preceding patch: -fPIC is passed via KCFLAGS, but the
arch adds -fPIE via KBUILD_CFLAGS_KERNEL, which kbuild applies after
KCFLAGS (so -fPIE would win). That patch's command-line
KBUILD_CFLAGS_KERNEL= assignment replaces the arch value and drops -fPIE,
letting -fPIC take effect. The two patches must stay together.

Co-developed-by: Kexin Liu <liukexin@kylinos.cn>
Signed-off-by: Kexin Liu <liukexin@kylinos.cn>
Signed-off-by: George Guo <guodongtai@kylinos.cn>
---
 scripts/livepatch/klp-build | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/scripts/livepatch/klp-build b/scripts/livepatch/klp-build
index 27fe8824ef12..42cd58aff3d8 100755
--- a/scripts/livepatch/klp-build
+++ b/scripts/livepatch/klp-build
@@ -557,8 +557,15 @@ build_kernel() {
 	local cmd=()
 
 	local ARCH_KBUILD_CFLAGS_KERNEL=""
+	local ARCH_KCFLAGS=""
 
 	if [[ -v CONFIG_LOONGARCH && "$CONFIG_LOONGARCH" == "y" ]]; then
+		# -fPIC replaces the kernel's -fPIE (added under CONFIG_RELOCATABLE);
+		# without that config there is no -fPIE to replace.
+		[[ "${CONFIG_RELOCATABLE:-}" == "y" ]] || \
+			die "LoongArch klp-build requires CONFIG_RELOCATABLE=y"
+		ARCH_KCFLAGS="-fPIC"
+
 		# -mdirect-extern-access only exists under explicit relocs, and this
 		# function replaces KBUILD_CFLAGS_KERNEL wholesale (safe only then;
 		# the non-explicit build puts -Wa,-mla-global-with-pcrel there).
@@ -599,8 +606,16 @@ build_kernel() {
 		cmd+=("-s")
 	fi
 	cmd+=("-j$JOBS")
-	cmd+=("KCFLAGS=-ffunction-sections -fdata-sections")
-	cmd+=("KBUILD_CFLAGS_KERNEL=$ARCH_KBUILD_CFLAGS_KERNEL")
+	cmd+=("KCFLAGS=-ffunction-sections -fdata-sections${ARCH_KCFLAGS:+ $ARCH_KCFLAGS}")
+	# -fPIC is added for KLP via KCFLAGS above; the arch adds -fPIE via
+	# KBUILD_CFLAGS_KERNEL, which kbuild places after KCFLAGS on the
+	# built-in compile line.  -fPIC/-fPIE is last-one-wins, so -fPIE would
+	# win.  Setting KBUILD_CFLAGS_KERNEL on the command line replaces the
+	# arch value (not append), which drops -fPIE and lets -fPIC win.  Only
+	# do this when an arch needs it (LoongArch).
+	if [[ -n "$ARCH_KBUILD_CFLAGS_KERNEL" ]]; then
+		cmd+=("KBUILD_CFLAGS_KERNEL=$ARCH_KBUILD_CFLAGS_KERNEL")
+	fi
 	cmd+=("vmlinux")
 	cmd+=("modules")
 
-- 
2.25.1

[PATCH v2 5/8] LoongArch: Fix EFI linking with -fdata-sections

[George Guo]

From: George Guo <guodongtai@kylinos.cn>

When building with func-fdata-sections, the .init.bss section gets split
up into a bunch of .init.bss.<var> sections.  Make sure they get linked
into .init.data.

Co-developed-by: Kexin Liu <liukexin@kylinos.cn>
Signed-off-by: Kexin Liu <liukexin@kylinos.cn>
Signed-off-by: George Guo <guodongtai@kylinos.cn>
---
 arch/loongarch/kernel/vmlinux.lds.S | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/loongarch/kernel/vmlinux.lds.S b/arch/loongarch/kernel/vmlinux.lds.S
index 840d944c2f73..dc5fa017db94 100644
--- a/arch/loongarch/kernel/vmlinux.lds.S
+++ b/arch/loongarch/kernel/vmlinux.lds.S
@@ -96,7 +96,7 @@ SECTIONS
 #endif
 
 	.init.bss : {
-		*(.init.bss)
+		*(.init.bss .init.bss.*)
 	}
 	. = ALIGN(PECOFF_SEGMENT_ALIGN);
 	__initdata_end = .;
-- 
2.25.1

[PATCH v2 6/8] objtool/klp: Add LoongArch jump opcode bytes support

[George Guo]

From: George Guo <guodongtai@kylinos.cn>

Implement arch_jump_opcode_bytes() for LoongArch so that klp checksums
for jump/call instructions with non-relocated destination offsets are
position-independent, mirroring the x86 and arm64 implementations.

Mask out the embedded branch offset while preserving the opcode and the
register operands, which differ per instruction format:

  - B/BL (reg0i26):                  no regs -> 0xfc000000
  - BEQZ/BNEZ/BCEQZ/BCNEZ (reg1i21): keep rj/cj -> 0xfc0003e0
  - JIRL/BEQ/BNE/.../BGEU (reg2i16): keep rj/rd -> 0xfc0003ff

Co-developed-by: Kexin Liu <liukexin@kylinos.cn>
Signed-off-by: Kexin Liu <liukexin@kylinos.cn>
Signed-off-by: George Guo <guodongtai@kylinos.cn>
---
 tools/objtool/arch/loongarch/decode.c | 41 +++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/tools/objtool/arch/loongarch/decode.c b/tools/objtool/arch/loongarch/decode.c
index 674e4efd138f..12facd0cc8d1 100644
--- a/tools/objtool/arch/loongarch/decode.c
+++ b/tools/objtool/arch/loongarch/decode.c
@@ -432,6 +432,47 @@ unsigned long arch_jump_table_sym_offset(struct reloc *reloc, struct reloc *tabl
 	}
 }
 
+size_t arch_jump_opcode_bytes(struct objtool_file *file, struct instruction *insn,
+			      unsigned char *buf)
+{
+	union loongarch_instruction *code;
+	u32 insn_word;
+
+	insn_word = le32toh(*(u32 *)(insn->sec->data->d_buf + insn->offset));
+	code = (union loongarch_instruction *)&insn_word;
+
+	switch (code->reg0i26_format.opcode) {
+	case b_op:
+	case bl_op:
+		/* reg0i26: 26-bit offset, no register operands */
+		insn_word &= 0xfc000000;
+		break;
+	case beqz_op:
+	case bnez_op:
+	case bceqz_op:		/* == bcnez_op */
+		/* reg1i21: keep opcode + rj/cj at bits[9:5] */
+		insn_word &= 0xfc0003e0;
+		break;
+	case jirl_op:
+	case beq_op:
+	case bne_op:
+	case blt_op:
+	case bge_op:
+	case bltu_op:
+	case bgeu_op:
+		/* reg2i16: keep opcode + rj/rd at bits[9:0] */
+		insn_word &= 0xfc0003ff;
+		break;
+	default:
+		break;
+	}
+
+	insn_word = htole32(insn_word);
+	memcpy(buf, &insn_word, sizeof(insn_word));
+
+	return LOONGARCH_INSN_SIZE;
+}
+
 #ifdef DISAS
 
 int arch_disas_info_init(struct disassemble_info *dinfo)
-- 
2.25.1

[PATCH v2 7/8] klp-build: Add LoongArch syscall patching macro

[George Guo]

From: George Guo <guodongtai@kylinos.cn>

Add LoongArch support for KLP_SYSCALL_DEFINEx(), mirroring the generic
__SYSCALL_DEFINEx() pattern from include/linux/syscalls.h.

Co-developed-by: Kexin Liu <liukexin@kylinos.cn>
Signed-off-by: Kexin Liu <liukexin@kylinos.cn>
Signed-off-by: George Guo <guodongtai@kylinos.cn>
---
 include/linux/livepatch_helpers.h | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/include/linux/livepatch_helpers.h b/include/linux/livepatch_helpers.h
index 4b647b83865f..a8aad067177b 100644
--- a/include/linux/livepatch_helpers.h
+++ b/include/linux/livepatch_helpers.h
@@ -91,6 +91,28 @@
 	}								\
 	static inline long __klp_do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
 
+#elif defined(CONFIG_LOONGARCH)
+
+#define __KLP_SYSCALL_DEFINEx(x, name, ...)                             \
+	__diag_push();                                                  \
+	__diag_ignore(GCC, 8, "-Wattribute-alias",                      \
+		      "Type aliasing is used to sanitize syscall arguments");\
+	asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))       \
+		__attribute__((alias(__stringify(__se_sys##name))));    \
+	ALLOW_ERROR_INJECTION(sys##name, ERRNO);                        \
+	static inline long __klp_do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
+	asmlinkage long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)); \
+	asmlinkage long __attribute__((optimize("-fno-optimize-sibling-calls")))\
+			__se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__))  \
+	{                                                               \
+		long ret = __klp_do_sys##name(__MAP(x,__SC_CAST,__VA_ARGS__));\
+		__MAP(x,__SC_TEST,__VA_ARGS__);                         \
+		__PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__));       \
+		return ret;                                             \
+	}                                                               \
+	__diag_pop();                                                   \
+	static inline long __klp_do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
+
 #endif
 
 #endif /* _LINUX_LIVEPATCH_HELPERS_H */
-- 
2.25.1

[PATCH v2 8/8] LoongArch: Add livepatch build (KLP) support

[George Guo]

From: George Guo <guodongtai@kylinos.cn>

This allows automated livepatch module generation using objtool.

Co-developed-by: Kexin Liu <liukexin@kylinos.cn>
Signed-off-by: Kexin Liu <liukexin@kylinos.cn>
Signed-off-by: George Guo <guodongtai@kylinos.cn>
---
 arch/loongarch/Kconfig | 1 +
 tools/objtool/Makefile | 3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 3b042dbb2c41..1dbf51ba9d6a 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -159,6 +159,7 @@ config LOONGARCH
 	select HAVE_IOREMAP_PROT
 	select HAVE_IRQ_EXIT_ON_IRQ_STACK
 	select HAVE_IRQ_TIME_ACCOUNTING
+	select HAVE_KLP_BUILD
 	select HAVE_KPROBES
 	select HAVE_KPROBES_ON_FTRACE
 	select HAVE_KRETPROBES
diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
index 94aabeee9736..83d645675ed9 100644
--- a/tools/objtool/Makefile
+++ b/tools/objtool/Makefile
@@ -8,7 +8,8 @@ ifeq ($(SRCARCH),x86)
 endif
 
 ifeq ($(SRCARCH),loongarch)
-	BUILD_ORC	   := y
+	BUILD_ORC    := y
+	ARCH_HAS_KLP := y
 endif
 
 ifeq ($(SRCARCH),arm64)
-- 
2.25.1