[PATCH v4 02/14] LoongArch: Mark special sections for KLP support
From: George Guo
Date: Fri Jul 24 2026 - 07:48:28 EST
From: George Guo <guodongtai@xxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Kexin Liu <liukexin@xxxxxxxxxx>
Signed-off-by: George Guo <guodongtai@xxxxxxxxxx>
---
arch/loongarch/include/asm/alternative-asm.h | 10 ++++++++--
arch/loongarch/include/asm/alternative.h | 11 +++++++++--
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 | 18 ++++++++++++++++++
6 files changed, 46 insertions(+), 6 deletions(-)
diff --git a/arch/loongarch/include/asm/alternative-asm.h b/arch/loongarch/include/asm/alternative-asm.h
index 7dc29bd9b2f0..92122a258a8e 100644
--- a/arch/loongarch/include/asm/alternative-asm.h
+++ b/arch/loongarch/include/asm/alternative-asm.h
@@ -5,6 +5,8 @@
#ifdef __ASSEMBLER__
#include <asm/asm.h>
+#include <generated/asm-offsets.h>
+#include <linux/annotate.h>
/*
* Issue one struct alt_instr descriptor entry (need to put it into
@@ -33,14 +35,16 @@
.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
.subsection 1
+ ANNOTATE_DATA_SPECIAL
143 :
\newinstr
144 :
+ ANNOTATE_DATA_SPECIAL_END
.previous
.endm
@@ -63,17 +67,19 @@
(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
.subsection 1
+ ANNOTATE_DATA_SPECIAL
143 :
\newinstr1
144 :
\newinstr2
145 :
+ ANNOTATE_DATA_SPECIAL_END
.previous
.endm
diff --git a/arch/loongarch/include/asm/alternative.h b/arch/loongarch/include/asm/alternative.h
index b5bae21fb3c8..1d3ac2f667d1 100644
--- a/arch/loongarch/include/asm/alternative.h
+++ b/arch/loongarch/include/asm/alternative.h
@@ -7,6 +7,7 @@
#include <linux/types.h>
#include <linux/stddef.h>
#include <linux/stringify.h>
+#include <linux/objtool.h>
#include <asm/asm.h>
struct alt_instr {
@@ -70,22 +71,28 @@ 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" \
+ ANNOTATE_DATA_SPECIAL "\n" \
ALTINSTR_REPLACEMENT(newinstr, feature, 1) \
+ ANNOTATE_DATA_SPECIAL_END "\n" \
".previous\n"
#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" \
".subsection 1\n" \
+ ANNOTATE_DATA_SPECIAL "\n" \
ALTINSTR_REPLACEMENT(newinstr1, feature1, 1) \
ALTINSTR_REPLACEMENT(newinstr2, feature2, 2) \
+ ANNOTATE_DATA_SPECIAL_END "\n" \
".previous\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..a611cbe557ed 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 +325,19 @@ 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();
+}
--
2.53.0