[PATCH v3 19/21] objtool/klp: Introduce objtool for arm64
Josh Poimboeuf
jpoimboe at kernel.org
Tue May 12 20:34:15 PDT 2026
Add basic support for arm64 on objtool. Only "objtool klp" subcommands
are currently supported.
Signed-off-by: Josh Poimboeuf <jpoimboe at kernel.org>
---
arch/arm64/Kconfig | 2 +
tools/objtool/Makefile | 4 +
tools/objtool/arch/arm64/Build | 2 +
tools/objtool/arch/arm64/decode.c | 177 ++++++++++++++++++
.../arch/arm64/include/arch/cfi_regs.h | 11 ++
tools/objtool/arch/arm64/include/arch/elf.h | 15 ++
.../objtool/arch/arm64/include/arch/special.h | 21 +++
tools/objtool/arch/arm64/special.c | 21 +++
8 files changed, 253 insertions(+)
create mode 100644 tools/objtool/arch/arm64/Build
create mode 100644 tools/objtool/arch/arm64/decode.c
create mode 100644 tools/objtool/arch/arm64/include/arch/cfi_regs.h
create mode 100644 tools/objtool/arch/arm64/include/arch/elf.h
create mode 100644 tools/objtool/arch/arm64/include/arch/special.h
create mode 100644 tools/objtool/arch/arm64/special.c
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index fe60738e5943b..101080fd4f99e 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -210,9 +210,11 @@ config ARM64
select HAVE_HW_BREAKPOINT if PERF_EVENTS
select HAVE_IOREMAP_PROT
select HAVE_IRQ_TIME_ACCOUNTING
+ select HAVE_KLP_BUILD
select HAVE_LIVEPATCH
select HAVE_MOD_ARCH_SPECIFIC
select HAVE_NMI
+ select HAVE_OBJTOOL
select HAVE_PERF_EVENTS
select HAVE_PERF_EVENTS_NMI if ARM64_PSEUDO_NMI
select HAVE_PERF_REGS
diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
index a4484fd22a96d..94aabeee97367 100644
--- a/tools/objtool/Makefile
+++ b/tools/objtool/Makefile
@@ -11,6 +11,10 @@ ifeq ($(SRCARCH),loongarch)
BUILD_ORC := y
endif
+ifeq ($(SRCARCH),arm64)
+ ARCH_HAS_KLP := y
+endif
+
ifeq ($(ARCH_HAS_KLP),y)
HAVE_XXHASH = $(shell printf "$(pound)include <xxhash.h>\nXXH3_state_t *state;int main() {}" | \
$(HOSTCC) $(HOSTCFLAGS) -xc - -o /dev/null -lxxhash 2> /dev/null && echo y || echo n)
diff --git a/tools/objtool/arch/arm64/Build b/tools/objtool/arch/arm64/Build
new file mode 100644
index 0000000000000..d24d5636a5b84
--- /dev/null
+++ b/tools/objtool/arch/arm64/Build
@@ -0,0 +1,2 @@
+objtool-y += decode.o
+objtool-y += special.o
diff --git a/tools/objtool/arch/arm64/decode.c b/tools/objtool/arch/arm64/decode.c
new file mode 100644
index 0000000000000..47658c76e1af0
--- /dev/null
+++ b/tools/objtool/arch/arm64/decode.c
@@ -0,0 +1,177 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <objtool/check.h>
+#include <objtool/disas.h>
+#include <objtool/elf.h>
+#include <objtool/arch.h>
+#include <objtool/warn.h>
+#include <objtool/builtin.h>
+
+const char *arch_reg_name[CFI_NUM_REGS] = {};
+
+int arch_ftrace_match(const char *name)
+{
+ return 0;
+}
+
+s64 arch_insn_adjusted_addend(struct instruction *insn, struct reloc *reloc)
+{
+ return reloc_addend(reloc);
+}
+
+bool arch_callee_saved_reg(unsigned char reg)
+{
+ return false;
+}
+
+int arch_decode_hint_reg(u8 sp_reg, int *base)
+{
+ exit(-1);
+}
+
+const char *arch_nop_insn(int len)
+{
+ exit(-1);
+}
+
+const char *arch_ret_insn(int len)
+{
+ exit(-1);
+}
+
+int arch_decode_instruction(struct objtool_file *file, const struct section *sec,
+ unsigned long offset, unsigned int maxlen,
+ struct instruction *insn)
+{
+ u32 ins;
+
+ if (maxlen < 4) {
+ ERROR_INSN(insn, "can't decode instruction");
+ return -1;
+ }
+
+ /* arm64 instructions are always LE, thus no bswap_if_needed() */
+ ins = le32toh(*(u32 *)(sec->data->d_buf + offset));
+
+ /*
+ * These are the bare minimum needed for static branch detection and
+ * checksum calculations.
+ */
+ if (ins == 0xd503201f) {
+ /* NOP: static branch */
+ insn->type = INSN_NOP;
+ } else if ((ins & 0xfc000000) == 0x14000000) {
+ /* B: static branch, intra-TU sibling call */
+ insn->type = INSN_JUMP_UNCONDITIONAL;
+ insn->immediate = sign_extend64(ins & 0x03ffffff, 25);
+ } else if ((ins & 0xfc000000) == 0x94000000) {
+ /* BL: intra-TU call */
+ insn->type = INSN_CALL;
+ insn->immediate = sign_extend64(ins & 0x03ffffff, 25);
+ } else if ((ins & 0xff000000) == 0x54000000) {
+ /* B.cond: intra-TU sibling call */
+ insn->type = INSN_JUMP_CONDITIONAL;
+ insn->immediate = sign_extend64((ins >> 5) & 0x7ffff, 18);
+ } else if ((ins & 0x7e000000) == 0x34000000) {
+ /* CBZ/CBNZ: intra-TU sibling call */
+ insn->type = INSN_JUMP_CONDITIONAL;
+ insn->immediate = sign_extend64((ins >> 5) & 0x7ffff, 18);
+ } else if ((ins & 0x7e000000) == 0x36000000) {
+ /* TBZ/TBNZ: intra-TU sibling call */
+ insn->type = INSN_JUMP_CONDITIONAL;
+ insn->immediate = sign_extend64((ins >> 5) & 0x3fff, 13);
+ } else {
+ insn->type = INSN_OTHER;
+ }
+
+ insn->len = 4;
+ return 0;
+}
+
+size_t arch_jump_opcode_bytes(struct objtool_file *file, struct instruction *insn,
+ unsigned char *buf)
+{
+ u32 ins;
+
+ ins = le32toh(*(u32 *)(insn->sec->data->d_buf + insn->offset));
+
+ switch (insn->type) {
+ case INSN_JUMP_UNCONDITIONAL:
+ case INSN_CALL:
+ ins &= ~0x03ffffff;
+ break;
+ case INSN_JUMP_CONDITIONAL:
+ if ((ins & 0xff000000) == 0x54000000)
+ ins &= ~0x00ffffe0; /* B.cond */
+ else if ((ins & 0x7e000000) == 0x34000000)
+ ins &= ~0x00ffffe0; /* CBZ/CBNZ */
+ else
+ ins &= ~0x0007ffe0; /* TBZ/TBNZ */
+ break;
+ default:
+ break;
+ }
+
+ ins = htole32(ins);
+ memcpy(buf, &ins, 4);
+ return 4;
+}
+
+u64 arch_adjusted_addend(struct reloc *reloc)
+{
+ return reloc_addend(reloc);
+}
+
+unsigned long arch_jump_destination(struct instruction *insn)
+{
+ return insn->offset + (insn->immediate << 2);
+}
+
+bool arch_pc_relative_reloc(struct reloc *reloc)
+{
+ switch (reloc_type(reloc)) {
+ case R_AARCH64_PREL64:
+ case R_AARCH64_PREL32:
+ case R_AARCH64_PREL16:
+ case R_AARCH64_LD_PREL_LO19:
+ case R_AARCH64_ADR_PREL_LO21:
+ case R_AARCH64_ADR_PREL_PG_HI21:
+ case R_AARCH64_ADR_PREL_PG_HI21_NC:
+ case R_AARCH64_JUMP26:
+ case R_AARCH64_CALL26:
+ case R_AARCH64_CONDBR19:
+ case R_AARCH64_TSTBR14:
+ return true;
+ default:
+ return false;
+ }
+}
+
+void arch_initial_func_cfi_state(struct cfi_init_state *state)
+{
+ state->cfa.base = CFI_UNDEFINED;
+}
+
+unsigned int arch_reloc_size(struct reloc *reloc)
+{
+ switch (reloc_type(reloc)) {
+ case R_AARCH64_ABS64:
+ case R_AARCH64_PREL64:
+ return 8;
+ case R_AARCH64_PREL16:
+ return 2;
+ default:
+ return 4;
+ }
+}
+
+#ifdef DISAS
+int arch_disas_info_init(struct disassemble_info *dinfo)
+{
+ return disas_info_init(dinfo, bfd_arch_aarch64,
+ bfd_mach_arm_unknown, bfd_mach_aarch64,
+ NULL);
+}
+#endif /* DISAS */
diff --git a/tools/objtool/arch/arm64/include/arch/cfi_regs.h b/tools/objtool/arch/arm64/include/arch/cfi_regs.h
new file mode 100644
index 0000000000000..49c81cbb6646d
--- /dev/null
+++ b/tools/objtool/arch/arm64/include/arch/cfi_regs.h
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _OBJTOOL_ARCH_CFI_REGS_H
+#define _OBJTOOL_ARCH_CFI_REGS_H
+
+/* These aren't actually used for arm64 */
+#define CFI_BP 0
+#define CFI_SP 0
+#define CFI_RA 0
+#define CFI_NUM_REGS 2
+
+#endif /* _OBJTOOL_ARCH_CFI_REGS_H */
diff --git a/tools/objtool/arch/arm64/include/arch/elf.h b/tools/objtool/arch/arm64/include/arch/elf.h
new file mode 100644
index 0000000000000..418b90885c501
--- /dev/null
+++ b/tools/objtool/arch/arm64/include/arch/elf.h
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _OBJTOOL_ARCH_ELF_H
+#define _OBJTOOL_ARCH_ELF_H
+
+#define R_NONE R_AARCH64_NONE
+#define R_ABS64 R_AARCH64_ABS64
+#define R_ABS32 R_AARCH64_ABS32
+#define R_DATA32 R_AARCH64_PREL32
+#define R_DATA64 R_AARCH64_PREL64
+#define R_TEXT32 R_AARCH64_PREL32
+#define R_TEXT64 R_AARCH64_PREL64
+
+#define ARCH_HAS_INLINE_ALTS 1
+
+#endif /* _OBJTOOL_ARCH_ELF_H */
diff --git a/tools/objtool/arch/arm64/include/arch/special.h b/tools/objtool/arch/arm64/include/arch/special.h
new file mode 100644
index 0000000000000..8ae804a83ea49
--- /dev/null
+++ b/tools/objtool/arch/arm64/include/arch/special.h
@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _OBJTOOL_ARCH_SPECIAL_H
+#define _OBJTOOL_ARCH_SPECIAL_H
+
+#define EX_ENTRY_SIZE 12
+#define EX_ORIG_OFFSET 0
+#define EX_NEW_OFFSET 4
+
+#define JUMP_ENTRY_SIZE 16
+#define JUMP_ORIG_OFFSET 0
+#define JUMP_NEW_OFFSET 4
+#define JUMP_KEY_OFFSET 8
+
+#define ALT_ENTRY_SIZE 12
+#define ALT_ORIG_OFFSET 0
+#define ALT_NEW_OFFSET 4
+#define ALT_FEATURE_OFFSET 8
+#define ALT_ORIG_LEN_OFFSET 10
+#define ALT_NEW_LEN_OFFSET 11
+
+#endif /* _OBJTOOL_ARCH_SPECIAL_H */
diff --git a/tools/objtool/arch/arm64/special.c b/tools/objtool/arch/arm64/special.c
new file mode 100644
index 0000000000000..6ddecd362f3dd
--- /dev/null
+++ b/tools/objtool/arch/arm64/special.c
@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#include <objtool/special.h>
+
+bool arch_support_alt_relocation(struct special_alt *special_alt,
+ struct instruction *insn,
+ struct reloc *reloc)
+{
+ return true;
+}
+
+struct reloc *arch_find_switch_table(struct objtool_file *file,
+ struct instruction *insn,
+ unsigned long *table_size)
+{
+ return NULL;
+}
+
+const char *arch_cpu_feature_name(int feature_number)
+{
+ return NULL;
+}
--
2.53.0
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