[PATCH v3 06/21] arm64: Annotate special section entries
Josh Poimboeuf
jpoimboe at kernel.org
Tue May 12 20:34:02 PDT 2026
In preparation for adding arm64 support for "objtool klp checksum/diff"
to enable livepatch module generation, annotate special section entries.
This will allow objtool to determine the size and location of the
entries and to extract them when needed.
A new ANNOTATE_DATA_SPECIAL_END annotation is added to mark the end of
special data blocks, which is needed because arm64's replacement
instructions are emitted in .text rather than .altinstr_replacement, so
there's otherwise no way to determine where the last replacement block
ends.
Signed-off-by: Josh Poimboeuf <jpoimboe at kernel.org>
---
arch/arm64/include/asm/alternative-macros.h | 27 ++++++++++++++++-----
arch/arm64/include/asm/asm-bug.h | 2 ++
arch/arm64/include/asm/asm-extable.h | 21 ++++++++++------
arch/arm64/include/asm/jump_label.h | 2 ++
arch/arm64/kernel/asm-offsets.c | 5 ++++
include/linux/annotate.h | 14 ++++++++++-
include/linux/objtool_types.h | 1 +
tools/include/linux/objtool_types.h | 1 +
tools/objtool/klp-diff.c | 5 +++-
9 files changed, 62 insertions(+), 16 deletions(-)
diff --git a/arch/arm64/include/asm/alternative-macros.h b/arch/arm64/include/asm/alternative-macros.h
index 8624166248528..ba86d655af1d7 100644
--- a/arch/arm64/include/asm/alternative-macros.h
+++ b/arch/arm64/include/asm/alternative-macros.h
@@ -3,11 +3,16 @@
#define __ASM_ALTERNATIVE_MACROS_H
#include <linux/const.h>
+#include <linux/annotate.h>
#include <vdso/bits.h>
#include <asm/cpucaps.h>
#include <asm/insn-def.h>
+#ifndef COMPILE_OFFSETS
+#include <asm/asm-offsets.h>
+#endif
+
/*
* Binutils 2.27.0 can't handle a 'UL' suffix on constants, so for the assembly
* macros below we must use we must use `(1 << ARM64_CB_SHIFT)`.
@@ -58,15 +63,18 @@
"661:\n\t" \
oldinstr "\n" \
"662:\n" \
- ".pushsection .altinstructions,\"a\"\n" \
+ ".pushsection .altinstructions,\"aM\", @progbits, " \
+ __stringify(ALT_INSTR_SIZE) "\n" \
ALTINSTR_ENTRY(cpucap) \
".popsection\n" \
".subsection 1\n" \
+ ANNOTATE_DATA_SPECIAL "\n" \
"663:\n\t" \
newinstr "\n" \
"664:\n\t" \
".org . - (664b-663b) + (662b-661b)\n\t" \
".org . - (662b-661b) + (664b-663b)\n\t" \
+ ANNOTATE_DATA_SPECIAL_END "\n\t" \
".previous\n" \
".endif\n"
@@ -75,7 +83,8 @@
"661:\n\t" \
oldinstr "\n" \
"662:\n" \
- ".pushsection .altinstructions,\"a\"\n" \
+ ".pushsection .altinstructions,\"aM\", @progbits, " \
+ __stringify(ALT_INSTR_SIZE) "\n" \
ALTINSTR_ENTRY_CB(cpucap, cb) \
".popsection\n" \
"663:\n\t" \
@@ -102,13 +111,15 @@
.macro alternative_insn insn1, insn2, cap, enable = 1
.if \enable
661: \insn1
-662: .pushsection .altinstructions, "a"
+662: .pushsection .altinstructions, "aM", @progbits, ALT_INSTR_SIZE
altinstruction_entry 661b, 663f, \cap, 662b-661b, 664f-663f
.popsection
.subsection 1
+ ANNOTATE_DATA_SPECIAL
663: \insn2
664: .org . - (664b-663b) + (662b-661b)
.org . - (662b-661b) + (664b-663b)
+ ANNOTATE_DATA_SPECIAL_END
.previous
.endif
.endm
@@ -137,7 +148,7 @@
*/
.macro alternative_if_not cap
.set .Lasm_alt_mode, 0
- .pushsection .altinstructions, "a"
+ .pushsection .altinstructions, "aM", @progbits, ALT_INSTR_SIZE
altinstruction_entry 661f, 663f, \cap, 662f-661f, 664f-663f
.popsection
661:
@@ -145,17 +156,18 @@
.macro alternative_if cap
.set .Lasm_alt_mode, 1
- .pushsection .altinstructions, "a"
+ .pushsection .altinstructions, "aM", @progbits, ALT_INSTR_SIZE
altinstruction_entry 663f, 661f, \cap, 664f-663f, 662f-661f
.popsection
.subsection 1
.align 2 /* So GAS knows label 661 is suitably aligned */
+ ANNOTATE_DATA_SPECIAL
661:
.endm
.macro alternative_cb cap, cb
.set .Lasm_alt_mode, 0
- .pushsection .altinstructions, "a"
+ .pushsection .altinstructions, "aM", @progbits, ALT_INSTR_SIZE
altinstruction_entry 661f, \cb, (1 << ARM64_CB_SHIFT) | \cap, 662f-661f, 0
.popsection
661:
@@ -168,7 +180,9 @@
662:
.if .Lasm_alt_mode==0
.subsection 1
+ ANNOTATE_DATA_SPECIAL
.else
+ ANNOTATE_DATA_SPECIAL_END
.previous
.endif
663:
@@ -182,6 +196,7 @@
.org . - (664b-663b) + (662b-661b)
.org . - (662b-661b) + (664b-663b)
.if .Lasm_alt_mode==0
+ ANNOTATE_DATA_SPECIAL_END
.previous
.endif
.endm
diff --git a/arch/arm64/include/asm/asm-bug.h b/arch/arm64/include/asm/asm-bug.h
index a5f13801b7840..22e1a9df9851d 100644
--- a/arch/arm64/include/asm/asm-bug.h
+++ b/arch/arm64/include/asm/asm-bug.h
@@ -5,6 +5,7 @@
*/
#define __ASM_ASM_BUG_H
+#include <linux/annotate.h>
#include <asm/brk-imm.h>
#ifdef CONFIG_DEBUG_BUGVERBOSE
@@ -24,6 +25,7 @@
#define __BUG_ENTRY_START \
.pushsection __bug_table,"aw"; \
.align 2; \
+ __ANNOTATE_DATA_SPECIAL; \
14470: .long 14471f - .; \
#define __BUG_ENTRY_END \
diff --git a/arch/arm64/include/asm/asm-extable.h b/arch/arm64/include/asm/asm-extable.h
index d67e2fdd1aee5..e81700edbb936 100644
--- a/arch/arm64/include/asm/asm-extable.h
+++ b/arch/arm64/include/asm/asm-extable.h
@@ -5,6 +5,10 @@
#include <linux/bits.h>
#include <asm/gpr-num.h>
+#ifndef COMPILE_OFFSETS
+#include <asm/asm-offsets.h>
+#endif
+
#define EX_TYPE_NONE 0
#define EX_TYPE_BPF 1
#define EX_TYPE_UACCESS_ERR_ZERO 2
@@ -29,13 +33,13 @@
#ifdef __ASSEMBLER__
-#define __ASM_EXTABLE_RAW(insn, fixup, type, data) \
- .pushsection __ex_table, "a"; \
- .align 2; \
- .long ((insn) - .); \
- .long ((fixup) - .); \
- .short (type); \
- .short (data); \
+#define __ASM_EXTABLE_RAW(insn, fixup, type, data) \
+ .pushsection __ex_table, "aM", @progbits, EXTABLE_SIZE; \
+ .align 2; \
+ .long ((insn) - .); \
+ .long ((fixup) - .); \
+ .short (type); \
+ .short (data); \
.popsection;
#define EX_DATA_REG(reg, gpr) \
@@ -82,7 +86,8 @@
#include <linux/stringify.h>
#define __ASM_EXTABLE_RAW(insn, fixup, type, data) \
- ".pushsection __ex_table, \"a\"\n" \
+ ".pushsection __ex_table, \"aM\", @progbits, "\
+ __stringify(EXTABLE_SIZE) "\n" \
".align 2\n" \
".long ((" insn ") - .)\n" \
".long ((" fixup ") - .)\n" \
diff --git a/arch/arm64/include/asm/jump_label.h b/arch/arm64/include/asm/jump_label.h
index 0cb211d3607d3..4dacb28641d72 100644
--- a/arch/arm64/include/asm/jump_label.h
+++ b/arch/arm64/include/asm/jump_label.h
@@ -11,6 +11,7 @@
#ifndef __ASSEMBLER__
#include <linux/types.h>
+#include <linux/annotate.h>
#include <asm/insn.h>
#define HAVE_JUMP_LABEL_BATCH
@@ -19,6 +20,7 @@
#define JUMP_TABLE_ENTRY(key, label) \
".pushsection __jump_table, \"aw\"\n\t" \
".align 3\n\t" \
+ ANNOTATE_DATA_SPECIAL "\n\t" \
".long 1b - ., " label " - .\n\t" \
".quad " key " - .\n\t" \
".popsection\n\t"
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index 44b92f582c127..76251586e31c7 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -23,6 +23,8 @@
#include <asm/suspend.h>
#include <linux/kbuild.h>
#include <linux/arm-smccc.h>
+#include <asm/alternative.h>
+#include <asm/extable.h>
int main(void)
{
@@ -185,5 +187,8 @@ int main(void)
#endif
DEFINE(PIE_E0_ASM, PIE_E0);
DEFINE(PIE_E1_ASM, PIE_E1);
+ BLANK();
+ DEFINE(ALT_INSTR_SIZE, sizeof(struct alt_instr));
+ DEFINE(EXTABLE_SIZE, sizeof(struct exception_table_entry));
return 0;
}
diff --git a/include/linux/annotate.h b/include/linux/annotate.h
index 2f1599c9e5732..7f5aa15f353d6 100644
--- a/include/linux/annotate.h
+++ b/include/linux/annotate.h
@@ -3,6 +3,7 @@
#define _LINUX_ANNOTATE_H
#include <linux/objtool_types.h>
+#include <linux/stringify.h>
#ifdef CONFIG_OBJTOOL
@@ -11,6 +12,10 @@
.long label - ., type; \
.popsection
+#define __ASM_ANNOTATE_DATA(type) \
+912: \
+ __ASM_ANNOTATE(.discard.annotate_data, 912b, type)
+
#ifndef __ASSEMBLY__
#define ASM_ANNOTATE_LABEL(label, type) \
@@ -39,6 +44,9 @@
#endif /* __ASSEMBLY__ */
#else /* !CONFIG_OBJTOOL */
+
+#define __ASM_ANNOTATE_DATA(type)
+
#ifndef __ASSEMBLY__
#define ASM_ANNOTATE_LABEL(label, type) ""
#define ASM_ANNOTATE(type)
@@ -106,10 +114,12 @@
#define ANNOTATE_NOCFI_SYM(sym) asm(ASM_ANNOTATE_LABEL(sym, ANNOTYPE_NOCFI))
/*
- * Annotate a special section entry. This emables livepatch module generation
+ * Annotate a special section entry. This enables livepatch module generation
* to find and extract individual special section entries as needed.
*/
#define ANNOTATE_DATA_SPECIAL ASM_ANNOTATE_DATA(ANNOTYPE_DATA_SPECIAL)
+#define __ANNOTATE_DATA_SPECIAL __ASM_ANNOTATE_DATA(ANNOTYPE_DATA_SPECIAL)
+#define ANNOTATE_DATA_SPECIAL_END ASM_ANNOTATE_DATA(ANNOTYPE_DATA_SPECIAL_END)
#else /* __ASSEMBLY__ */
#define ANNOTATE_NOENDBR ANNOTATE type=ANNOTYPE_NOENDBR
@@ -122,6 +132,8 @@
#define ANNOTATE_REACHABLE ANNOTATE type=ANNOTYPE_REACHABLE
#define ANNOTATE_NOCFI_SYM ANNOTATE type=ANNOTYPE_NOCFI
#define ANNOTATE_DATA_SPECIAL ANNOTATE_DATA type=ANNOTYPE_DATA_SPECIAL
+#define __ANNOTATE_DATA_SPECIAL __ASM_ANNOTATE_DATA(ANNOTYPE_DATA_SPECIAL)
+#define ANNOTATE_DATA_SPECIAL_END ANNOTATE_DATA type=ANNOTYPE_DATA_SPECIAL_END
#endif /* __ASSEMBLY__ */
#endif /* _LINUX_ANNOTATE_H */
diff --git a/include/linux/objtool_types.h b/include/linux/objtool_types.h
index c6def4049b1ae..744118ffd025f 100644
--- a/include/linux/objtool_types.h
+++ b/include/linux/objtool_types.h
@@ -68,5 +68,6 @@ struct unwind_hint {
#define ANNOTYPE_NOCFI 9
#define ANNOTYPE_DATA_SPECIAL 1
+#define ANNOTYPE_DATA_SPECIAL_END 2
#endif /* _LINUX_OBJTOOL_TYPES_H */
diff --git a/tools/include/linux/objtool_types.h b/tools/include/linux/objtool_types.h
index c6def4049b1ae..744118ffd025f 100644
--- a/tools/include/linux/objtool_types.h
+++ b/tools/include/linux/objtool_types.h
@@ -68,5 +68,6 @@ struct unwind_hint {
#define ANNOTYPE_NOCFI 9
#define ANNOTYPE_DATA_SPECIAL 1
+#define ANNOTYPE_DATA_SPECIAL_END 2
#endif /* _LINUX_OBJTOOL_TYPES_H */
diff --git a/tools/objtool/klp-diff.c b/tools/objtool/klp-diff.c
index f8787d7d14547..6a1cec57dc6a3 100644
--- a/tools/objtool/klp-diff.c
+++ b/tools/objtool/klp-diff.c
@@ -1667,7 +1667,10 @@ static int create_fake_symbols(struct elf *elf)
size = 0;
next_reloc = reloc;
for_each_reloc_continue(sec->rsec, next_reloc) {
- if (annotype(elf, sec, next_reloc) != ANNOTYPE_DATA_SPECIAL ||
+ unsigned int next_type = annotype(elf, sec, next_reloc);
+
+ if ((next_type != ANNOTYPE_DATA_SPECIAL &&
+ next_type != ANNOTYPE_DATA_SPECIAL_END) ||
next_reloc->sym->sec != reloc->sym->sec)
continue;
--
2.53.0
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