23 files changed, 2088 insertions, 59 deletions

diff --git a/MAINTAINERS b/MAINTAINERS
index 46126ce2f968..755e2528f839 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14439,7 +14439,7 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/livepatching/livepatching.g
 F:	Documentation/ABI/testing/sysfs-kernel-livepatch
 F:	Documentation/livepatch/
 F:	arch/powerpc/include/asm/livepatch.h
-F:	include/linux/livepatch.h
+F:	include/linux/livepatch*.h
 F:	kernel/livepatch/
 F:	kernel/module/livepatch.c
 F:	samples/livepatch/
diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h
index 51a258c24ff5..772919e8096a 100644
--- a/include/linux/livepatch.h
+++ b/include/linux/livepatch.h
@@ -13,6 +13,7 @@
 #include <linux/ftrace.h>
 #include <linux/completion.h>
 #include <linux/list.h>
+#include <linux/livepatch_external.h>
 #include <linux/livepatch_sched.h>
 
 #if IS_ENABLED(CONFIG_LIVEPATCH)
@@ -77,30 +78,6 @@ struct klp_func {
 	bool transition;
 };
 
-struct klp_object;
-
-/**
- * struct klp_callbacks - pre/post live-(un)patch callback structure
- * @pre_patch:		executed before code patching
- * @post_patch:		executed after code patching
- * @pre_unpatch:	executed before code unpatching
- * @post_unpatch:	executed after code unpatching
- * @post_unpatch_enabled:	flag indicating if post-unpatch callback
- * 				should run
- *
- * All callbacks are optional.  Only the pre-patch callback, if provided,
- * will be unconditionally executed.  If the parent klp_object fails to
- * patch for any reason, including a non-zero error status returned from
- * the pre-patch callback, no further callbacks will be executed.
- */
-struct klp_callbacks {
-	int (*pre_patch)(struct klp_object *obj);
-	void (*post_patch)(struct klp_object *obj);
-	void (*pre_unpatch)(struct klp_object *obj);
-	void (*post_unpatch)(struct klp_object *obj);
-	bool post_unpatch_enabled;
-};
-
 /**
  * struct klp_object - kernel object structure for live patching
  * @name:	module name (or NULL for vmlinux)
diff --git a/include/linux/livepatch_external.h b/include/linux/livepatch_external.h
new file mode 100644
index 000000000000..138af19b0f5c
--- /dev/null
+++ b/include/linux/livepatch_external.h
@@ -0,0 +1,76 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * External livepatch interfaces for patch creation tooling
+ */
+
+#ifndef _LINUX_LIVEPATCH_EXTERNAL_H_
+#define _LINUX_LIVEPATCH_EXTERNAL_H_
+
+#include <linux/types.h>
+
+#define KLP_RELOC_SEC_PREFIX		".klp.rela."
+#define KLP_SYM_PREFIX			".klp.sym."
+
+#define __KLP_PRE_PATCH_PREFIX		__klp_pre_patch_callback_
+#define __KLP_POST_PATCH_PREFIX		__klp_post_patch_callback_
+#define __KLP_PRE_UNPATCH_PREFIX	__klp_pre_unpatch_callback_
+#define __KLP_POST_UNPATCH_PREFIX	__klp_post_unpatch_callback_
+
+#define KLP_PRE_PATCH_PREFIX		__stringify(__KLP_PRE_PATCH_PREFIX)
+#define KLP_POST_PATCH_PREFIX		__stringify(__KLP_POST_PATCH_PREFIX)
+#define KLP_PRE_UNPATCH_PREFIX		__stringify(__KLP_PRE_UNPATCH_PREFIX)
+#define KLP_POST_UNPATCH_PREFIX		__stringify(__KLP_POST_UNPATCH_PREFIX)
+
+struct klp_object;
+
+typedef int (*klp_pre_patch_t)(struct klp_object *obj);
+typedef void (*klp_post_patch_t)(struct klp_object *obj);
+typedef void (*klp_pre_unpatch_t)(struct klp_object *obj);
+typedef void (*klp_post_unpatch_t)(struct klp_object *obj);
+
+/**
+ * struct klp_callbacks - pre/post live-(un)patch callback structure
+ * @pre_patch:		executed before code patching
+ * @post_patch:		executed after code patching
+ * @pre_unpatch:	executed before code unpatching
+ * @post_unpatch:	executed after code unpatching
+ * @post_unpatch_enabled:	flag indicating if post-unpatch callback
+ *				should run
+ *
+ * All callbacks are optional.  Only the pre-patch callback, if provided,
+ * will be unconditionally executed.  If the parent klp_object fails to
+ * patch for any reason, including a non-zero error status returned from
+ * the pre-patch callback, no further callbacks will be executed.
+ */
+struct klp_callbacks {
+	klp_pre_patch_t		pre_patch;
+	klp_post_patch_t	post_patch;
+	klp_pre_unpatch_t	pre_unpatch;
+	klp_post_unpatch_t	post_unpatch;
+	bool post_unpatch_enabled;
+};
+
+/*
+ * 'struct klp_{func,object}_ext' are compact "external" representations of
+ * 'struct klp_{func,object}'.   They are used by objtool for livepatch
+ * generation.  The structs are then read by the livepatch module and converted
+ * to the real structs before calling klp_enable_patch().
+ *
+ * TODO make these the official API for klp_enable_patch().  That should
+ * simplify livepatch's interface as well as its data structure lifetime
+ * management.
+ */
+struct klp_func_ext {
+	const char *old_name;
+	void *new_func;
+	unsigned long sympos;
+};
+
+struct klp_object_ext {
+	const char *name;
+	struct klp_func_ext *funcs;
+	struct klp_callbacks callbacks;
+	unsigned int nr_funcs;
+};
+
+#endif /* _LINUX_LIVEPATCH_EXTERNAL_H_ */
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 7e443c2cf7d4..0044a8125013 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -224,7 +224,7 @@ static int klp_resolve_symbols(Elf_Shdr *sechdrs, const char *strtab,
 
 		/* Format: .klp.sym.sym_objname.sym_name,sympos */
 		cnt = sscanf(strtab + sym->st_name,
-			     ".klp.sym.%55[^.].%511[^,],%lu",
+			     KLP_SYM_PREFIX "%55[^.].%511[^,],%lu",
 			     sym_objname, sym_name, &sympos);
 		if (cnt != 3) {
 			pr_err("symbol %s has an incorrectly formatted name\n",
@@ -303,7 +303,7 @@ static int klp_write_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
 	 * See comment in klp_resolve_symbols() for an explanation
 	 * of the selected field width value.
 	 */
-	cnt = sscanf(shstrtab + sec->sh_name, ".klp.rela.%55[^.]",
+	cnt = sscanf(shstrtab + sec->sh_name, KLP_RELOC_SEC_PREFIX "%55[^.]",
 		     sec_objname);
 	if (cnt != 1) {
 		pr_err("section %s has an incorrectly formatted name\n",
diff --git a/scripts/module.lds.S b/scripts/module.lds.S
index 2632c6cb8ebe..3037d5e5527c 100644
--- a/scripts/module.lds.S
+++ b/scripts/module.lds.S
@@ -34,8 +34,16 @@ SECTIONS {
 
 	__patchable_function_entries : { *(__patchable_function_entries) }
 
+	__klp_funcs		0: ALIGN(8) { KEEP(*(__klp_funcs)) }
+
+	__klp_objects		0: ALIGN(8) {
+		__start_klp_objects = .;
+		KEEP(*(__klp_objects))
+		__stop_klp_objects = .;
+	}
+
 #ifdef CONFIG_ARCH_USES_CFI_TRAPS
-	__kcfi_traps 		: { KEEP(*(.kcfi_traps)) }
+	__kcfi_traps		: { KEEP(*(.kcfi_traps)) }
 #endif
 
 	.text : {
diff --git a/tools/include/linux/livepatch_external.h b/tools/include/linux/livepatch_external.h
new file mode 100644
index 000000000000..138af19b0f5c
--- /dev/null
+++ b/tools/include/linux/livepatch_external.h
@@ -0,0 +1,76 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * External livepatch interfaces for patch creation tooling
+ */
+
+#ifndef _LINUX_LIVEPATCH_EXTERNAL_H_
+#define _LINUX_LIVEPATCH_EXTERNAL_H_
+
+#include <linux/types.h>
+
+#define KLP_RELOC_SEC_PREFIX		".klp.rela."
+#define KLP_SYM_PREFIX			".klp.sym."
+
+#define __KLP_PRE_PATCH_PREFIX		__klp_pre_patch_callback_
+#define __KLP_POST_PATCH_PREFIX		__klp_post_patch_callback_
+#define __KLP_PRE_UNPATCH_PREFIX	__klp_pre_unpatch_callback_
+#define __KLP_POST_UNPATCH_PREFIX	__klp_post_unpatch_callback_
+
+#define KLP_PRE_PATCH_PREFIX		__stringify(__KLP_PRE_PATCH_PREFIX)
+#define KLP_POST_PATCH_PREFIX		__stringify(__KLP_POST_PATCH_PREFIX)
+#define KLP_PRE_UNPATCH_PREFIX		__stringify(__KLP_PRE_UNPATCH_PREFIX)
+#define KLP_POST_UNPATCH_PREFIX		__stringify(__KLP_POST_UNPATCH_PREFIX)
+
+struct klp_object;
+
+typedef int (*klp_pre_patch_t)(struct klp_object *obj);
+typedef void (*klp_post_patch_t)(struct klp_object *obj);
+typedef void (*klp_pre_unpatch_t)(struct klp_object *obj);
+typedef void (*klp_post_unpatch_t)(struct klp_object *obj);
+
+/**
+ * struct klp_callbacks - pre/post live-(un)patch callback structure
+ * @pre_patch:		executed before code patching
+ * @post_patch:		executed after code patching
+ * @pre_unpatch:	executed before code unpatching
+ * @post_unpatch:	executed after code unpatching
+ * @post_unpatch_enabled:	flag indicating if post-unpatch callback
+ *				should run
+ *
+ * All callbacks are optional.  Only the pre-patch callback, if provided,
+ * will be unconditionally executed.  If the parent klp_object fails to
+ * patch for any reason, including a non-zero error status returned from
+ * the pre-patch callback, no further callbacks will be executed.
+ */
+struct klp_callbacks {
+	klp_pre_patch_t		pre_patch;
+	klp_post_patch_t	post_patch;
+	klp_pre_unpatch_t	pre_unpatch;
+	klp_post_unpatch_t	post_unpatch;
+	bool post_unpatch_enabled;
+};
+
+/*
+ * 'struct klp_{func,object}_ext' are compact "external" representations of
+ * 'struct klp_{func,object}'.   They are used by objtool for livepatch
+ * generation.  The structs are then read by the livepatch module and converted
+ * to the real structs before calling klp_enable_patch().
+ *
+ * TODO make these the official API for klp_enable_patch().  That should
+ * simplify livepatch's interface as well as its data structure lifetime
+ * management.
+ */
+struct klp_func_ext {
+	const char *old_name;
+	void *new_func;
+	unsigned long sympos;
+};
+
+struct klp_object_ext {
+	const char *name;
+	struct klp_func_ext *funcs;
+	struct klp_callbacks callbacks;
+	unsigned int nr_funcs;
+};
+
+#endif /* _LINUX_LIVEPATCH_EXTERNAL_H_ */
diff --git a/tools/include/linux/string.h b/tools/include/linux/string.h
index 8499f509f03e..51ad3cf4fa82 100644
--- a/tools/include/linux/string.h
+++ b/tools/include/linux/string.h
@@ -44,6 +44,20 @@ static inline bool strstarts(const char *str, const char *prefix)
 	return strncmp(str, prefix, strlen(prefix)) == 0;
 }
 
+/*
+ * Checks if a string ends with another.
+ */
+static inline bool str_ends_with(const char *str, const char *substr)
+{
+	size_t len = strlen(str);
+	size_t sublen = strlen(substr);
+
+	if (sublen > len)
+		return false;
+
+	return !strcmp(str + len - sublen, substr);
+}
+
 extern char * __must_check skip_spaces(const char *);
 
 extern char *strim(char *);
diff --git a/tools/objtool/Build b/tools/objtool/Build
index a3cdf8af6635..0b01657671d7 100644
--- a/tools/objtool/Build
+++ b/tools/objtool/Build
@@ -8,8 +8,8 @@ objtool-y += builtin-check.o
 objtool-y += elf.o
 objtool-y += objtool.o
 
-objtool-$(BUILD_ORC) += orc_gen.o
-objtool-$(BUILD_ORC) += orc_dump.o
+objtool-$(BUILD_ORC) += orc_gen.o orc_dump.o
+objtool-$(BUILD_KLP) += builtin-klp.o klp-diff.o
 
 objtool-y += libstring.o
 objtool-y += libctype.o
diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
index 958761c05b7c..48928c9bebef 100644
--- a/tools/objtool/Makefile
+++ b/tools/objtool/Makefile
@@ -15,13 +15,14 @@ ifeq ($(ARCH_HAS_KLP),y)
 	HAVE_XXHASH = $(shell echo "int main() {}" | \
 		      $(HOSTCC) -xc - -o /dev/null -lxxhash 2> /dev/null && echo y || echo n)
 	ifeq ($(HAVE_XXHASH),y)
+		BUILD_KLP	 := y
 		LIBXXHASH_CFLAGS := $(shell $(HOSTPKG_CONFIG) libxxhash --cflags 2>/dev/null) \
 				    -DBUILD_KLP
 		LIBXXHASH_LIBS   := $(shell $(HOSTPKG_CONFIG) libxxhash --libs 2>/dev/null || echo -lxxhash)
 	endif
 endif
 
-export BUILD_ORC
+export BUILD_ORC BUILD_KLP
 
 ifeq ($(srctree),)
 srctree := $(patsubst %/,%,$(dir $(CURDIR)))
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index b2c320f701f9..5c72beeaa3a7 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -88,6 +88,46 @@ s64 arch_insn_adjusted_addend(struct instruction *insn, struct reloc *reloc)
 	return phys_to_virt(addend);
 }
 
+static void scan_for_insn(struct section *sec, unsigned long offset,
+			  unsigned long *insn_off, unsigned int *insn_len)
+{
+	unsigned long o = 0;
+	struct insn insn;
+
+	while (1) {
+
+		insn_decode(&insn, sec->data->d_buf + o, sec_size(sec) - o,
+			    INSN_MODE_64);
+
+		if (o + insn.length > offset) {
+			*insn_off = o;
+			*insn_len = insn.length;
+			return;
+		}
+
+		o += insn.length;
+	}
+}
+
+u64 arch_adjusted_addend(struct reloc *reloc)
+{
+	unsigned int type = reloc_type(reloc);
+	s64 addend = reloc_addend(reloc);
+	unsigned long insn_off;
+	unsigned int insn_len;
+
+	if (type == R_X86_64_PLT32)
+		return addend + 4;
+
+	if (type != R_X86_64_PC32 || !is_text_sec(reloc->sec->base))
+		return addend;
+
+	scan_for_insn(reloc->sec->base, reloc_offset(reloc),
+		      &insn_off, &insn_len);
+
+	return addend + insn_off + insn_len - reloc_offset(reloc);
+}
+
 unsigned long arch_jump_destination(struct instruction *insn)
 {
 	return insn->offset + insn->len + insn->immediate;
diff --git a/tools/objtool/builtin-klp.c b/tools/objtool/builtin-klp.c
new file mode 100644
index 000000000000..9b13dd1182af
--- /dev/null
+++ b/tools/objtool/builtin-klp.c
@@ -0,0 +1,52 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#include <subcmd/parse-options.h>
+#include <string.h>
+#include <stdlib.h>
+#include <objtool/builtin.h>
+#include <objtool/objtool.h>
+#include <objtool/klp.h>
+
+struct subcmd {
+	const char *name;
+	const char *description;
+	int (*fn)(int, const char **);
+};
+
+static struct subcmd subcmds[] = {
+	{ "diff",		"Generate binary diff of two object files",		cmd_klp_diff, },
+};
+
+static void cmd_klp_usage(void)
+{
+	fprintf(stderr, "usage: objtool klp <subcommand> [<options>]\n\n");
+	fprintf(stderr, "Subcommands:\n");
+
+	for (int i = 0; i < ARRAY_SIZE(subcmds); i++) {
+		struct subcmd *cmd = &subcmds[i];
+
+		fprintf(stderr, "  %s\t%s\n", cmd->name, cmd->description);
+	}
+
+	exit(1);
+}
+
+int cmd_klp(int argc, const char **argv)
+{
+	argc--;
+	argv++;
+
+	if (!argc)
+		cmd_klp_usage();
+
+	if (argc) {
+		for (int i = 0; i < ARRAY_SIZE(subcmds); i++) {
+			struct subcmd *cmd = &subcmds[i];
+
+			if (!strcmp(cmd->name, argv[0]))
+				return cmd->fn(argc, argv);
+		}
+	}
+
+	cmd_klp_usage();
+	return 0;
+}
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 0f5278127f37..8d17d930d0c8 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -186,20 +186,6 @@ static bool is_sibling_call(struct instruction *insn)
 }
 
 /*
- * Checks if a string ends with another.
- */
-static bool str_ends_with(const char *s, const char *sub)
-{
-	const int slen = strlen(s);
-	const int sublen = strlen(sub);
-
-	if (sublen > slen)
-		return 0;
-
-	return !memcmp(s + slen - sublen, sub, sublen);
-}
-
-/*
  * Checks if a function is a Rust "noreturn" one.
  */
 static bool is_rust_noreturn(const struct symbol *func)
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 0119b3b4c554..e1daae0630be 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -288,6 +288,18 @@ struct symbol *find_symbol_by_name(const struct elf *elf, const char *name)
 	return NULL;
 }
 
+struct symbol *find_global_symbol_by_name(const struct elf *elf, const char *name)
+{
+	struct symbol *sym;
+
+	elf_hash_for_each_possible(symbol_name, sym, name_hash, str_hash(name)) {
+		if (!strcmp(sym->name, name) && !is_local_sym(sym))
+			return sym;
+	}
+
+	return NULL;
+}
+
 struct reloc *find_reloc_by_dest_range(const struct elf *elf, struct section *sec,
 				     unsigned long offset, unsigned int len)
 {
@@ -475,6 +487,8 @@ static int elf_add_symbol(struct elf *elf, struct symbol *sym)
 	else
 		entry = &sym->sec->symbol_list;
 	list_add(&sym->list, entry);
+
+	list_add_tail(&sym->global_list, &elf->symbols);
 	elf_hash_add(symbol, &sym->hash, sym->idx);
 	elf_hash_add(symbol_name, &sym->name_hash, str_hash(sym->name));
 
@@ -531,6 +545,9 @@ static int read_symbols(struct elf *elf)
 		ERROR_GLIBC("calloc");
 		return -1;
 	}
+
+	INIT_LIST_HEAD(&elf->symbols);
+
 	for (i = 0; i < symbols_nr; i++) {
 		sym = &elf->symbol_data[i];
 
@@ -639,7 +656,7 @@ static int mark_group_syms(struct elf *elf)
 		return -1;
 	}
 
-	list_for_each_entry(sec, &elf->sections, list) {
+	for_each_sec(elf, sec) {
 		if (sec->sh.sh_type == SHT_GROUP &&
 		    sec->sh.sh_link == symtab->idx) {
 			sym = find_symbol_by_index(elf, sec->sh.sh_info);
@@ -1224,6 +1241,8 @@ struct elf *elf_create_file(GElf_Ehdr *ehdr, const char *name)
 		return NULL;
 	}
 
+	INIT_LIST_HEAD(&elf->symbols);
+
 	if (!elf_alloc_hash(section,		1000) ||
 	    !elf_alloc_hash(section_name,	1000) ||
 	    !elf_alloc_hash(symbol,		10000) ||
diff --git a/tools/objtool/include/objtool/arch.h b/tools/objtool/include/objtool/arch.h
index a4502947307a..d89f8b5ec14e 100644
--- a/tools/objtool/include/objtool/arch.h
+++ b/tools/objtool/include/objtool/arch.h
@@ -84,6 +84,7 @@ bool arch_callee_saved_reg(unsigned char reg);
 unsigned long arch_jump_destination(struct instruction *insn);
 
 s64 arch_insn_adjusted_addend(struct instruction *insn, struct reloc *reloc);
+u64 arch_adjusted_addend(struct reloc *reloc);
 
 const char *arch_nop_insn(int len);
 const char *arch_ret_insn(int len);
diff --git a/tools/objtool/include/objtool/builtin.h b/tools/objtool/include/objtool/builtin.h
index cee9fc031877..bb0b25eb08ba 100644
--- a/tools/objtool/include/objtool/builtin.h
+++ b/tools/objtool/include/objtool/builtin.h
@@ -53,4 +53,6 @@ int objtool_run(int argc, const char **argv);
 
 int make_backup(void);
 
+int cmd_klp(int argc, const char **argv);
+
 #endif /* _BUILTIN_H */
diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h
index a1f1762f89c4..e2cd817fca52 100644
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -18,6 +18,7 @@
 #include <objtool/checksum_types.h>
 #include <arch/elf.h>
 
+#define SEC_NAME_LEN		1024
 #define SYM_NAME_LEN		512
 
 #define bswap_if_needed(elf, val) __bswap_if_needed(&elf->ehdr, val)
@@ -53,10 +54,12 @@ struct section {
 	bool _changed, text, rodata, noinstr, init, truncate;
 	struct reloc *relocs;
 	unsigned long nr_alloc_relocs;
+	struct section *twin;
 };
 
 struct symbol {
 	struct list_head list;
+	struct list_head global_list;
 	struct rb_node node;
 	struct elf_hash_node hash;
 	struct elf_hash_node name_hash;
@@ -83,10 +86,13 @@ struct symbol {
 	u8 cold		     : 1;
 	u8 prefix	     : 1;
 	u8 debug_checksum    : 1;
+	u8 changed	     : 1;
+	u8 included	     : 1;
 	struct list_head pv_target;
 	struct reloc *relocs;
 	struct section *group_sec;
 	struct checksum csum;
+	struct symbol *twin, *clone;
 };
 
 struct reloc {
@@ -104,6 +110,7 @@ struct elf {
 	const char *name, *tmp_name;
 	unsigned int num_files;
 	struct list_head sections;
+	struct list_head symbols;
 	unsigned long num_relocs;
 
 	int symbol_bits;
@@ -179,6 +186,7 @@ struct section *find_section_by_name(const struct elf *elf, const char *name);
 struct symbol *find_func_by_offset(struct section *sec, unsigned long offset);
 struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset);
 struct symbol *find_symbol_by_name(const struct elf *elf, const char *name);
+struct symbol *find_global_symbol_by_name(const struct elf *elf, const char *name);
 struct symbol *find_symbol_containing(const struct section *sec, unsigned long offset);
 int find_symbol_hole_containing(const struct section *sec, unsigned long offset);
 struct reloc *find_reloc_by_dest(const struct elf *elf, struct section *sec, unsigned long offset);
@@ -448,22 +456,48 @@ static inline void set_sym_next_reloc(struct reloc *reloc, struct reloc *next)
 #define sec_for_each_sym(sec, sym)					\
 	list_for_each_entry(sym, &sec->symbol_list, list)
 
+#define sec_prev_sym(sym)						\
+	sym->sec && sym->list.prev != &sym->sec->symbol_list ?		\
+	list_prev_entry(sym, list) : NULL
+
 #define for_each_sym(elf, sym)						\
-	for (struct section *__sec, *__fake = (struct section *)1;	\
-	     __fake; __fake = NULL)					\
-		for_each_sec(elf, __sec)				\
-			sec_for_each_sym(__sec, sym)
+	list_for_each_entry(sym, &elf->symbols, global_list)
+
+#define for_each_sym_continue(elf, sym)					\
+	list_for_each_entry_continue(sym, &elf->symbols, global_list)
+
+#define rsec_next_reloc(rsec, reloc)					\
+	reloc_idx(reloc) < sec_num_entries(rsec) - 1 ? reloc + 1 : NULL
 
 #define for_each_reloc(rsec, reloc)					\
-	for (int __i = 0, __fake = 1; __fake; __fake = 0)		\
-		for (reloc = rsec->relocs;				\
-		     __i < sec_num_entries(rsec);			\
-		     __i++, reloc++)
+	for (reloc = rsec->relocs; reloc; reloc = rsec_next_reloc(rsec, reloc))
 
 #define for_each_reloc_from(rsec, reloc)				\
-	for (int __i = reloc_idx(reloc);				\
-	     __i < sec_num_entries(rsec);				\
-	     __i++, reloc++)
+	for (; reloc; reloc = rsec_next_reloc(rsec, reloc))
+
+#define for_each_reloc_continue(rsec, reloc)				\
+	for (reloc = rsec_next_reloc(rsec, reloc); reloc;		\
+	     reloc = rsec_next_reloc(rsec, reloc))
+
+#define sym_for_each_reloc(elf, sym, reloc)				\
+	for (reloc = find_reloc_by_dest_range(elf, sym->sec,		\
+					      sym->offset, sym->len);	\
+	     reloc && reloc_offset(reloc) <  sym->offset + sym->len;	\
+	     reloc = rsec_next_reloc(sym->sec->rsec, reloc))
+
+static inline struct symbol *get_func_prefix(struct symbol *func)
+{
+	struct symbol *prev;
+
+	if (!is_func_sym(func))
+		return NULL;
+
+	prev = sec_prev_sym(func);
+	if (prev && is_prefix_func(prev))
+		return prev;
+
+	return NULL;
+}
 
 #define OFFSET_STRIDE_BITS	4
 #define OFFSET_STRIDE		(1UL << OFFSET_STRIDE_BITS)
diff --git a/tools/objtool/include/objtool/klp.h b/tools/objtool/include/objtool/klp.h
new file mode 100644
index 000000000000..07928fac059b
--- /dev/null
+++ b/tools/objtool/include/objtool/klp.h
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _OBJTOOL_KLP_H
+#define _OBJTOOL_KLP_H
+
+/*
+ * __klp_objects and __klp_funcs are created by klp diff and used by the patch
+ * module init code to build the klp_patch, klp_object and klp_func structs
+ * needed by the livepatch API.
+ */
+#define KLP_OBJECTS_SEC	"__klp_objects"
+#define KLP_FUNCS_SEC	"__klp_funcs"
+
+/*
+ * __klp_relocs is an intermediate section which are created by klp diff and
+ * converted into KLP symbols/relas by "objtool klp post-link".  This is needed
+ * to work around the linker, which doesn't preserve SHN_LIVEPATCH or
+ * SHF_RELA_LIVEPATCH, nor does it support having two RELA sections for a
+ * single PROGBITS section.
+ */
+#define KLP_RELOCS_SEC	"__klp_relocs"
+#define KLP_STRINGS_SEC	".rodata.klp.str1.1"
+
+struct klp_reloc {
+	void *offset;
+	void *sym;
+	u32 type;
+};
+
+int cmd_klp_diff(int argc, const char **argv);
+
+#endif /* _OBJTOOL_KLP_H */
diff --git a/tools/objtool/include/objtool/objtool.h b/tools/objtool/include/objtool/objtool.h
index c0dc86a78ff6..7f70b41d1b8d 100644
--- a/tools/objtool/include/objtool/objtool.h
+++ b/tools/objtool/include/objtool/objtool.h
@@ -39,6 +39,8 @@ struct objtool_file {
 	struct pv_state *pv_ops;
 };
 
+char *top_level_dir(const char *file);
+
 struct objtool_file *objtool_open_read(const char *_objname);
 
 int objtool_pv_add(struct objtool_file *file, int idx, struct symbol *func);
diff --git a/tools/objtool/include/objtool/util.h b/tools/objtool/include/objtool/util.h
new file mode 100644
index 000000000000..a0180b312f73
--- /dev/null
+++ b/tools/objtool/include/objtool/util.h
@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _UTIL_H
+#define _UTIL_H
+
+#include <objtool/warn.h>
+
+#define snprintf_check(str, size, format, args...)			\
+({									\
+	int __ret = snprintf(str, size, format, args);			\
+	if (__ret < 0)							\
+		ERROR_GLIBC("snprintf");				\
+	else if (__ret >= size)						\
+		ERROR("snprintf() failed for '" format "'", args);	\
+	else								\
+		__ret = 0;						\
+	__ret;								\
+})
+
+#endif /* _UTIL_H */
diff --git a/tools/objtool/klp-diff.c b/tools/objtool/klp-diff.c
new file mode 100644
index 000000000000..0d69b621a26c
--- /dev/null
+++ b/tools/objtool/klp-diff.c
@@ -0,0 +1,1646 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#define _GNU_SOURCE /* memmem() */
+#include <subcmd/parse-options.h>
+#include <stdlib.h>
+#include <string.h>
+#include <libgen.h>
+#include <stdio.h>
+#include <ctype.h>
+
+#include <objtool/objtool.h>
+#include <objtool/warn.h>
+#include <objtool/arch.h>
+#include <objtool/klp.h>
+#include <objtool/util.h>
+#include <arch/special.h>
+
+#include <linux/objtool_types.h>
+#include <linux/livepatch_external.h>
+#include <linux/stringify.h>
+#include <linux/string.h>
+#include <linux/jhash.h>
+
+#define sizeof_field(TYPE, MEMBER) sizeof((((TYPE *)0)->MEMBER))
+
+struct elfs {
+	struct elf *orig, *patched, *out;
+	const char *modname;
+};
+
+struct export {
+	struct hlist_node hash;
+	char *mod, *sym;
+};
+
+static const char * const klp_diff_usage[] = {
+	"objtool klp diff [<options>] <in1.o> <in2.o> <out.o>",
+	NULL,
+};
+
+static const struct option klp_diff_options[] = {
+	OPT_END(),
+};
+
+static DEFINE_HASHTABLE(exports, 15);
+
+static inline u32 str_hash(const char *str)
+{
+	return jhash(str, strlen(str), 0);
+}
+
+static int read_exports(void)
+{
+	const char *symvers = "Module.symvers";
+	char line[1024], *path = NULL;
+	unsigned int line_num = 1;
+	FILE *file;
+
+	file = fopen(symvers, "r");
+	if (!file) {
+		path = top_level_dir(symvers);
+		if (!path) {
+			ERROR("can't open '%s', \"objtool diff\" should be run from the kernel tree", symvers);
+			return -1;
+		}
+
+		file = fopen(path, "r");
+		if (!file) {
+			ERROR_GLIBC("fopen");
+			return -1;
+		}
+	}
+
+	while (fgets(line, 1024, file)) {
+		char *sym, *mod, *type;
+		struct export *export;
+
+		sym = strchr(line, '\t');
+		if (!sym) {
+			ERROR("malformed Module.symvers (sym) at line %d", line_num);
+			return -1;
+		}
+
+		*sym++ = '\0';
+
+		mod = strchr(sym, '\t');
+		if (!mod) {
+			ERROR("malformed Module.symvers (mod) at line %d", line_num);
+			return -1;
+		}
+
+		*mod++ = '\0';
+
+		type = strchr(mod, '\t');
+		if (!type) {
+			ERROR("malformed Module.symvers (type) at line %d", line_num);
+			return -1;
+		}
+
+		*type++ = '\0';
+
+		if (*sym == '\0' || *mod == '\0') {
+			ERROR("malformed Module.symvers at line %d", line_num);
+			return -1;
+		}
+
+		export = calloc(1, sizeof(*export));
+		if (!export) {
+			ERROR_GLIBC("calloc");
+			return -1;
+		}
+
+		export->mod = strdup(mod);
+		if (!export->mod) {
+			ERROR_GLIBC("strdup");
+			return -1;
+		}
+
+		export->sym = strdup(sym);
+		if (!export->sym) {
+			ERROR_GLIBC("strdup");
+			return -1;
+		}
+
+		hash_add(exports, &export->hash, str_hash(sym));
+	}
+
+	free(path);
+	fclose(file);
+
+	return 0;
+}
+
+static int read_sym_checksums(struct elf *elf)
+{
+	struct section *sec;
+
+	sec = find_section_by_name(elf, ".discard.sym_checksum");
+	if (!sec) {
+		ERROR("'%s' missing .discard.sym_checksum section, file not processed by 'objtool --checksum'?",
+		      elf->name);
+		return -1;
+	}
+
+	if (!sec->rsec) {
+		ERROR("missing reloc section for .discard.sym_checksum");
+		return -1;
+	}
+
+	if (sec_size(sec) % sizeof(struct sym_checksum)) {
+		ERROR("struct sym_checksum size mismatch");
+		return -1;
+	}
+
+	for (int i = 0; i < sec_size(sec) / sizeof(struct sym_checksum); i++) {
+		struct sym_checksum *sym_checksum;
+		struct reloc *reloc;
+		struct symbol *sym;
+
+		sym_checksum = (struct sym_checksum *)sec->data->d_buf + i;
+
+		reloc = find_reloc_by_dest(elf, sec, i * sizeof(*sym_checksum));
+		if (!reloc) {
+			ERROR("can't find reloc for sym_checksum[%d]", i);
+			return -1;
+		}
+
+		sym = reloc->sym;
+
+		if (is_sec_sym(sym)) {
+			ERROR("not sure how to handle section %s", sym->name);
+			return -1;
+		}
+
+		if (is_func_sym(sym))
+			sym->csum.checksum = sym_checksum->checksum;
+	}
+
+	return 0;
+}
+
+static struct symbol *first_file_symbol(struct elf *elf)
+{
+	struct symbol *sym;
+
+	for_each_sym(elf, sym) {
+		if (is_file_sym(sym))
+			return sym;
+	}
+
+	return NULL;
+}
+
+static struct symbol *next_file_symbol(struct elf *elf, struct symbol *sym)
+{
+	for_each_sym_continue(elf, sym) {
+		if (is_file_sym(sym))
+			return sym;
+	}
+
+	return NULL;
+}
+
+/*
+ * Certain static local variables should never be correlated.  They will be
+ * used in place rather than referencing the originals.
+ */
+static bool is_uncorrelated_static_local(struct symbol *sym)
+{
+	static const char * const vars[] = {
+		"__key.",
+		"__warned.",
+		"__already_done.",
+		"__func__.",
+		"_rs.",
+		"descriptor.",
+		"CSWTCH.",
+	};
+
+	if (!is_object_sym(sym) || !is_local_sym(sym))
+		return false;
+
+	if (!strcmp(sym->sec->name, ".data.once"))
+		return true;
+
+	for (int i = 0; i < ARRAY_SIZE(vars); i++) {
+		if (strstarts(sym->name, vars[i]))
+			return true;
+	}
+
+	return false;
+}
+
+/*
+ * Clang emits several useless .Ltmp_* code labels.
+ */
+static bool is_clang_tmp_label(struct symbol *sym)
+{
+	return sym->type == STT_NOTYPE &&
+	       is_text_sec(sym->sec) &&
+	       strstarts(sym->name, ".Ltmp") &&
+	       isdigit(sym->name[5]);
+}
+
+static bool is_special_section(struct section *sec)
+{
+	static const char * const specials[] = {
+		".altinstructions",
+		".smp_locks",
+		"__bug_table",
+		"__ex_table",
+		"__jump_table",
+		"__mcount_loc",
+
+		/*
+		 * Extract .static_call_sites here to inherit non-module
+		 * preferential treatment.  The later static call processing
+		 * during klp module build will be skipped when it sees this
+		 * section already exists.
+		 */
+		".static_call_sites",
+	};
+
+	static const char * const non_special_discards[] = {
+		".discard.addressable",
+		".discard.sym_checksum",
+	};
+
+	if (is_text_sec(sec))
+		return false;
+
+	for (int i = 0; i < ARRAY_SIZE(specials); i++) {
+		if (!strcmp(sec->name, specials[i]))
+			return true;
+	}
+
+	/* Most .discard data sections are special */
+	for (int i = 0; i < ARRAY_SIZE(non_special_discards); i++) {
+		if (!strcmp(sec->name, non_special_discards[i]))
+			return false;
+	}
+
+	return strstarts(sec->name, ".discard.");
+}
+
+/*
+ * These sections are referenced by special sections but aren't considered
+ * special sections themselves.
+ */
+static bool is_special_section_aux(struct section *sec)
+{
+	static const char * const specials_aux[] = {
+		".altinstr_replacement",
+		".altinstr_aux",
+	};
+
+	for (int i = 0; i < ARRAY_SIZE(specials_aux); i++) {
+		if (!strcmp(sec->name, specials_aux[i]))
+			return true;
+	}
+
+	return false;
+}
+
+/*
+ * These symbols should never be correlated, so their local patched versions
+ * are used instead of linking to the originals.
+ */
+static bool dont_correlate(struct symbol *sym)
+{
+	return is_file_sym(sym) ||
+	       is_null_sym(sym) ||
+	       is_sec_sym(sym) ||
+	       is_prefix_func(sym) ||
+	       is_uncorrelated_static_local(sym) ||
+	       is_clang_tmp_label(sym) ||
+	       is_string_sec(sym->sec) ||
+	       is_special_section(sym->sec) ||
+	       is_special_section_aux(sym->sec) ||
+	       strstarts(sym->name, "__initcall__");
+}
+
+/*
+ * For each symbol in the original kernel, find its corresponding "twin" in the
+ * patched kernel.
+ */
+static int correlate_symbols(struct elfs *e)
+{
+	struct symbol *file1_sym, *file2_sym;
+	struct symbol *sym1, *sym2;
+
+	/* Correlate locals */
+	for (file1_sym = first_file_symbol(e->orig),
+	     file2_sym = first_file_symbol(e->patched); ;
+	     file1_sym = next_file_symbol(e->orig, file1_sym),
+	     file2_sym = next_file_symbol(e->patched, file2_sym)) {
+
+		if (!file1_sym && file2_sym) {
+			ERROR("FILE symbol mismatch: NULL != %s", file2_sym->name);
+			return -1;
+		}
+
+		if (file1_sym && !file2_sym) {
+			ERROR("FILE symbol mismatch: %s != NULL", file1_sym->name);
+			return -1;
+		}
+
+		if (!file1_sym)
+			break;
+
+		if (strcmp(file1_sym->name, file2_sym->name)) {
+			ERROR("FILE symbol mismatch: %s != %s", file1_sym->name, file2_sym->name);
+			return -1;
+		}
+
+		file1_sym->twin = file2_sym;
+		file2_sym->twin = file1_sym;
+
+		sym1 = file1_sym;
+
+		for_each_sym_continue(e->orig, sym1) {
+			if (is_file_sym(sym1) || !is_local_sym(sym1))
+				break;
+
+			if (dont_correlate(sym1))
+				continue;
+
+			sym2 = file2_sym;
+			for_each_sym_continue(e->patched, sym2) {
+				if (is_file_sym(sym2) || !is_local_sym(sym2))
+					break;
+
+				if (sym2->twin || dont_correlate(sym2))
+					continue;
+
+				if (strcmp(sym1->demangled_name, sym2->demangled_name))
+					continue;
+
+				sym1->twin = sym2;
+				sym2->twin = sym1;
+				break;
+			}
+		}
+	}
+
+	/* Correlate globals */
+	for_each_sym(e->orig, sym1) {
+		if (sym1->bind == STB_LOCAL)
+			continue;
+
+		sym2 = find_global_symbol_by_name(e->patched, sym1->name);
+
+		if (sym2 && !sym2->twin && !strcmp(sym1->name, sym2->name)) {
+			sym1->twin = sym2;
+			sym2->twin = sym1;
+		}
+	}
+
+	for_each_sym(e->orig, sym1) {
+		if (sym1->twin || dont_correlate(sym1))
+			continue;
+		WARN("no correlation: %s", sym1->name);
+	}
+
+	return 0;
+}
+
+/* "sympos" is used by livepatch to disambiguate duplicate symbol names */
+static unsigned long find_sympos(struct elf *elf, struct symbol *sym)
+{
+	bool vmlinux = str_ends_with(objname, "vmlinux.o");
+	unsigned long sympos = 0, nr_matches = 0;
+	bool has_dup = false;
+	struct symbol *s;
+
+	if (sym->bind != STB_LOCAL)
+		return 0;
+
+	if (vmlinux && sym->type == STT_FUNC) {
+		/*
+		 * HACK: Unfortunately, symbol ordering can differ between
+		 * vmlinux.o and vmlinux due to the linker script emitting
+		 * .text.unlikely* before .text*.  Count .text.unlikely* first.
+		 *
+		 * TODO: Disambiguate symbols more reliably (checksums?)
+		 */
+		for_each_sym(elf, s) {
+			if (strstarts(s->sec->name, ".text.unlikely") &&
+			    !strcmp(s->name, sym->name)) {
+				nr_matches++;
+				if (s == sym)
+					sympos = nr_matches;
+				else
+					has_dup = true;
+			}
+		}
+		for_each_sym(elf, s) {
+			if (!strstarts(s->sec->name, ".text.unlikely") &&
+			    !strcmp(s->name, sym->name)) {
+				nr_matches++;
+				if (s == sym)
+					sympos = nr_matches;
+				else
+					has_dup = true;
+			}
+		}
+	} else {
+		for_each_sym(elf, s) {
+			if (!strcmp(s->name, sym->name)) {
+				nr_matches++;
+				if (s == sym)
+					sympos = nr_matches;
+				else
+					has_dup = true;
+			}
+		}
+	}
+
+	if (!sympos) {
+		ERROR("can't find sympos for %s", sym->name);
+		return ULONG_MAX;
+	}
+
+	return has_dup ? sympos : 0;
+}
+
+static int clone_sym_relocs(struct elfs *e, struct symbol *patched_sym);
+
+static struct symbol *__clone_symbol(struct elf *elf, struct symbol *patched_sym,
+				     bool data_too)
+{
+	struct section *out_sec = NULL;
+	unsigned long offset = 0;
+	struct symbol *out_sym;
+
+	if (data_too && !is_undef_sym(patched_sym)) {
+		struct section *patched_sec = patched_sym->sec;
+
+		out_sec = find_section_by_name(elf, patched_sec->name);
+		if (!out_sec) {
+			out_sec = elf_create_section(elf, patched_sec->name, 0,
+						     patched_sec->sh.sh_entsize,
+						     patched_sec->sh.sh_type,
+						     patched_sec->sh.sh_addralign,
+						     patched_sec->sh.sh_flags);
+			if (!out_sec)
+				return NULL;
+		}
+
+		if (is_string_sec(patched_sym->sec)) {
+			out_sym = elf_create_section_symbol(elf, out_sec);
+			if (!out_sym)
+				return NULL;
+
+			goto sym_created;
+		}
+
+		if (!is_sec_sym(patched_sym))
+			offset = sec_size(out_sec);
+
+		if (patched_sym->len || is_sec_sym(patched_sym)) {
+			void *data = NULL;
+			size_t size;
+
+			/* bss doesn't have data */
+			if (patched_sym->sec->data->d_buf)
+				data = patched_sym->sec->data->d_buf + patched_sym->offset;
+
+			if (is_sec_sym(patched_sym))
+				size = sec_size(patched_sym->sec);
+			else
+				size = patched_sym->len;
+
+			if (!elf_add_data(elf, out_sec, data, size))
+				return NULL;
+		}
+	}
+
+	out_sym = elf_create_symbol(elf, patched_sym->name, out_sec,
+				    patched_sym->bind, patched_sym->type,
+				    offset, patched_sym->len);
+	if (!out_sym)
+		return NULL;
+
+sym_created:
+	patched_sym->clone = out_sym;
+	out_sym->clone = patched_sym;
+
+	return out_sym;
+}
+
+/*
+ * Copy a symbol to the output object, optionally including its data and
+ * relocations.
+ */
+static struct symbol *clone_symbol(struct elfs *e, struct symbol *patched_sym,
+				   bool data_too)
+{
+	struct symbol *pfx;
+
+	if (patched_sym->clone)
+		return patched_sym->clone;
+
+	/* Make sure the prefix gets cloned first */
+	if (is_func_sym(patched_sym) && data_too) {
+		pfx = get_func_prefix(patched_sym);
+		if (pfx)
+			clone_symbol(e, pfx, true);
+	}
+
+	if (!__clone_symbol(e->out, patched_sym, data_too))
+		return NULL;
+
+	if (data_too && clone_sym_relocs(e, patched_sym))
+		return NULL;
+
+	return patched_sym->clone;
+}
+
+static void mark_included_function(struct symbol *func)
+{
+	struct symbol *pfx;
+
+	func->included = 1;
+
+	/* Include prefix function */
+	pfx = get_func_prefix(func);
+	if (pfx)
+		pfx->included = 1;
+
+	/* Make sure .cold parent+child always stay together */
+	if (func->cfunc && func->cfunc != func)
+		func->cfunc->included = 1;
+	if (func->pfunc && func->pfunc != func)
+		func->pfunc->included = 1;
+}
+
+/*
+ * Copy all changed functions (and their dependencies) from the patched object
+ * to the output object.
+ */
+static int mark_changed_functions(struct elfs *e)
+{
+	struct symbol *sym_orig, *patched_sym;
+	bool changed = false;
+
+	/* Find changed functions */
+	for_each_sym(e->orig, sym_orig) {
+		if (!is_func_sym(sym_orig) || is_prefix_func(sym_orig))
+			continue;
+
+		patched_sym = sym_orig->twin;
+		if (!patched_sym)
+			continue;
+
+		if (sym_orig->csum.checksum != patched_sym->csum.checksum) {
+			patched_sym->changed = 1;
+			mark_included_function(patched_sym);
+			changed = true;
+		}
+	}
+
+	/* Find added functions and print them */
+	for_each_sym(e->patched, patched_sym) {
+		if (!is_func_sym(patched_sym) || is_prefix_func(patched_sym))
+			continue;
+
+		if (!patched_sym->twin) {
+			printf("%s: new function: %s\n", objname, patched_sym->name);
+			mark_included_function(patched_sym);
+			changed = true;
+		}
+	}
+
+	/* Print changed functions */
+	for_each_sym(e->patched, patched_sym) {
+		if (patched_sym->changed)
+			printf("%s: changed function: %s\n", objname, patched_sym->name);
+	}
+
+	return !changed ? -1 : 0;
+}
+
+static int clone_included_functions(struct elfs *e)
+{
+	struct symbol *patched_sym;
+
+	for_each_sym(e->patched, patched_sym) {
+		if (patched_sym->included) {
+			if (!clone_symbol(e, patched_sym, true))
+				return -1;
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * Determine whether a relocation should reference the section rather than the
+ * underlying symbol.
+ */
+static bool section_reference_needed(struct section *sec)
+{
+	/*
+	 * String symbols are zero-length and uncorrelated.  It's easier to
+	 * deal with them as section symbols.
+	 */
+	if (is_string_sec(sec))
+		return true;
+
+	/*
+	 * .rodata has mostly anonymous data so there's no way to determine the
+	 * length of a needed reference.  just copy the whole section if needed.
+	 */
+	if (strstarts(sec->name, ".rodata"))
+		return true;
+
+	/* UBSAN anonymous data */
+	if (strstarts(sec->name, ".data..Lubsan") ||	/* GCC */
+	    strstarts(sec->name, ".data..L__unnamed_"))	/* Clang */
+		return true;
+
+	return false;
+}
+
+static bool is_reloc_allowed(struct reloc *reloc)
+{
+	return section_reference_needed(reloc->sym->sec) == is_sec_sym(reloc->sym);
+}
+
+static struct export *find_export(struct symbol *sym)
+{
+	struct export *export;
+
+	hash_for_each_possible(exports, export, hash, str_hash(sym->name)) {
+		if (!strcmp(export->sym, sym->name))
+			return export;
+	}
+
+	return NULL;
+}
+
+static const char *__find_modname(struct elfs *e)
+{
+	struct section *sec;
+	char *name;
+
+	sec = find_section_by_name(e->orig, ".modinfo");
+	if (!sec) {
+		ERROR("missing .modinfo section");
+		return NULL;
+	}
+
+	name = memmem(sec->data->d_buf, sec_size(sec), "\0name=", 6);
+	if (name)
+		return name + 6;
+
+	name = strdup(e->orig->name);
+	if (!name) {
+		ERROR_GLIBC("strdup");
+		return NULL;
+	}
+
+	for (char *c = name; *c; c++) {
+		if (*c == '/')
+			name = c + 1;
+		else if (*c == '-')
+			*c = '_';
+		else if (*c == '.') {
+			*c = '\0';
+			break;
+		}
+	}
+
+	return name;
+}
+
+/* Get the object's module name as defined by the kernel (and klp_object) */
+static const char *find_modname(struct elfs *e)
+{
+	const char *modname;
+
+	if (e->modname)
+		return e->modname;
+
+	modname = __find_modname(e);
+	e->modname = modname;
+	return modname;
+}
+
+/*
+ * Copying a function from its native compiled environment to a kernel module
+ * removes its natural access to local functions/variables and unexported
+ * globals.  References to such symbols need to be converted to KLP relocs so
+ * the kernel arch relocation code knows to apply them and where to find the
+ * symbols.  Particularly, duplicate static symbols need to be disambiguated.
+ */
+static bool klp_reloc_needed(struct reloc *patched_reloc)
+{
+	struct symbol *patched_sym = patched_reloc->sym;
+	struct export *export;
+
+	/* no external symbol to reference */
+	if (dont_correlate(patched_sym))
+		return false;
+
+	/* For included functions, a regular reloc will do. */
+	if (patched_sym->included)
+		return false;
+
+	/*
+	 * If exported by a module, it has to be a klp reloc.  Thanks to the
+	 * clusterfunk that is late module patching, the patch module is
+	 * allowed to be loaded before any modules it depends on.
+	 *
+	 * If exported by vmlinux, a normal reloc will do.
+	 */
+	export = find_export(patched_sym);
+	if (export)
+		return strcmp(export->mod, "vmlinux");
+
+	if (!patched_sym->twin) {
+		/*
+		 * Presumably the symbol and its reference were added by the
+		 * patch.  The symbol could be defined in this .o or in another
+		 * .o in the patch module.
+		 *
+		 * This check needs to be *after* the export check due to the
+		 * possibility of the patch adding a new UNDEF reference to an
+		 * exported symbol.
+		 */
+		return false;
+	}
+
+	/* Unexported symbol which lives in the original vmlinux or module. */
+	return true;
+}
+
+static int convert_reloc_sym_to_secsym(struct elf *elf, struct reloc *reloc)
+{
+	struct symbol *sym = reloc->sym;
+	struct section *sec = sym->sec;
+
+	if (!sec->sym && !elf_create_section_symbol(elf, sec))
+		return -1;
+
+	reloc->sym = sec->sym;
+	set_reloc_sym(elf, reloc, sym->idx);
+	set_reloc_addend(elf, reloc, sym->offset + reloc_addend(reloc));
+	return 0;
+}
+
+static int convert_reloc_secsym_to_sym(struct elf *elf, struct reloc *reloc)
+{
+	struct symbol *sym = reloc->sym;
+	struct section *sec = sym->sec;
+
+	/* If the symbol has a dedicated section, it's easy to find */
+	sym = find_symbol_by_offset(sec, 0);
+	if (sym && sym->len == sec_size(sec))
+		goto found_sym;
+
+	/* No dedicated section; find the symbol manually */
+	sym = find_symbol_containing(sec, arch_adjusted_addend(reloc));
+	if (!sym) {
+		/*
+		 * This can happen for special section references to weak code
+		 * whose symbol has been stripped by the linker.
+		 */
+		return -1;
+	}
+
+found_sym:
+	reloc->sym = sym;
+	set_reloc_sym(elf, reloc, sym->idx);
+	set_reloc_addend(elf, reloc, reloc_addend(reloc) - sym->offset);
+	return 0;
+}
+
+/*
+ * Convert a relocation symbol reference to the needed format: either a section
+ * symbol or the underlying symbol itself.
+ */
+static int convert_reloc_sym(struct elf *elf, struct reloc *reloc)
+{
+	if (is_reloc_allowed(reloc))
+		return 0;
+
+	if (section_reference_needed(reloc->sym->sec))
+		return convert_reloc_sym_to_secsym(elf, reloc);
+	else
+		return convert_reloc_secsym_to_sym(elf, reloc);
+}
+
+/*
+ * Convert a regular relocation to a klp relocation (sort of).
+ */
+static int clone_reloc_klp(struct elfs *e, struct reloc *patched_reloc,
+			   struct section *sec, unsigned long offset,
+			   struct export *export)
+{
+	struct symbol *patched_sym = patched_reloc->sym;
+	s64 addend = reloc_addend(patched_reloc);
+	const char *sym_modname, *sym_orig_name;
+	static struct section *klp_relocs;
+	struct symbol *sym, *klp_sym;
+	unsigned long klp_reloc_off;
+	char sym_name[SYM_NAME_LEN];
+	struct klp_reloc klp_reloc;
+	unsigned long sympos;
+
+	if (!patched_sym->twin) {
+		ERROR("unexpected klp reloc for new symbol %s", patched_sym->name);
+		return -1;
+	}
+
+	/*
+	 * Keep the original reloc intact for now to avoid breaking objtool run
+	 * which relies on proper relocations for many of its features.  This
+	 * will be disabled later by "objtool klp post-link".
+	 *
+	 * Convert it to UNDEF (and WEAK to avoid modpost warnings).
+	 */
+
+	sym = patched_sym->clone;
+	if (!sym) {
+		/* STB_WEAK: avoid modpost undefined symbol warnings */
+		sym = elf_create_symbol(e->out, patched_sym->name, NULL,
+					STB_WEAK, patched_sym->type, 0, 0);
+		if (!sym)
+			return -1;
+
+		patched_sym->clone = sym;
+		sym->clone = patched_sym;
+	}
+
+	if (!elf_create_reloc(e->out, sec, offset, sym, addend, reloc_type(patched_reloc)))
+		return -1;
+
+	/*
+	 * Create the KLP symbol.
+	 */
+
+	if (export) {
+		sym_modname = export->mod;
+		sym_orig_name = export->sym;
+		sympos = 0;
+	} else {
+		sym_modname = find_modname(e);
+		if (!sym_modname)
+			return -1;
+
+		sym_orig_name = patched_sym->twin->name;
+		sympos = find_sympos(e->orig, patched_sym->twin);
+		if (sympos == ULONG_MAX)
+			return -1;
+	}
+
+	/* symbol format: .klp.sym.modname.sym_name,sympos */
+	if (snprintf_check(sym_name, SYM_NAME_LEN, KLP_SYM_PREFIX "%s.%s,%ld",
+		      sym_modname, sym_orig_name, sympos))
+		return -1;
+
+	klp_sym = find_symbol_by_name(e->out, sym_name);
+	if (!klp_sym) {
+		/* STB_WEAK: avoid modpost undefined symbol warnings */
+		klp_sym = elf_create_symbol(e->out, sym_name, NULL,
+					    STB_WEAK, patched_sym->type, 0, 0);
+		if (!klp_sym)
+			return -1;
+	}
+
+	/*
+	 * Create the __klp_relocs entry.  This will be converted to an actual
+	 * KLP rela by "objtool klp post-link".
+	 *
+	 * This intermediate step is necessary to prevent corruption by the
+	 * linker, which doesn't know how to properly handle two rela sections
+	 * applying to the same base section.
+	 */
+
+	if (!klp_relocs) {
+		klp_relocs = elf_create_section(e->out, KLP_RELOCS_SEC, 0,
+						0, SHT_PROGBITS, 8, SHF_ALLOC);
+		if (!klp_relocs)
+			return -1;
+	}
+
+	klp_reloc_off = sec_size(klp_relocs);
+	memset(&klp_reloc, 0, sizeof(klp_reloc));
+
+	klp_reloc.type = reloc_type(patched_reloc);
+	if (!elf_add_data(e->out, klp_relocs, &klp_reloc, sizeof(klp_reloc)))
+		return -1;
+
+	/* klp_reloc.offset */
+	if (!sec->sym && !elf_create_section_symbol(e->out, sec))
+		return -1;
+
+	if (!elf_create_reloc(e->out, klp_relocs,
+			      klp_reloc_off + offsetof(struct klp_reloc, offset),
+			      sec->sym, offset, R_ABS64))
+		return -1;
+
+	/* klp_reloc.sym */
+	if (!elf_create_reloc(e->out, klp_relocs,
+			      klp_reloc_off + offsetof(struct klp_reloc, sym),
+			      klp_sym, addend, R_ABS64))
+		return -1;
+
+	return 0;
+}
+
+/* Copy a reloc and its symbol to the output object */
+static int clone_reloc(struct elfs *e, struct reloc *patched_reloc,
+			struct section *sec, unsigned long offset)
+{
+	struct symbol *patched_sym = patched_reloc->sym;
+	struct export *export = find_export(patched_sym);
+	long addend = reloc_addend(patched_reloc);
+	struct symbol *out_sym;
+	bool klp;
+
+	if (!is_reloc_allowed(patched_reloc)) {
+		ERROR_FUNC(patched_reloc->sec->base, reloc_offset(patched_reloc),
+			   "missing symbol for reference to %s+%ld",
+			   patched_sym->name, addend);
+		return -1;
+	}
+
+	klp = klp_reloc_needed(patched_reloc);
+
+	if (klp) {
+		if (clone_reloc_klp(e, patched_reloc, sec, offset, export))
+			return -1;
+
+		return 0;
+	}
+
+	/*
+	 * Why !export sets 'data_too':
+	 *
+	 * Unexported non-klp symbols need to live in the patch module,
+	 * otherwise there will be unresolved symbols.  Notably, this includes:
+	 *
+	 *   - New functions/data
+	 *   - String sections
+	 *   - Special section entries
+	 *   - Uncorrelated static local variables
+	 *   - UBSAN sections
+	 */
+	out_sym = clone_symbol(e, patched_sym, patched_sym->included || !export);
+	if (!out_sym)
+		return -1;
+
+	/*
+	 * For strings, all references use section symbols, thanks to
+	 * section_reference_needed().  clone_symbol() has cloned an empty
+	 * version of the string section.  Now copy the string itself.
+	 */
+	if (is_string_sec(patched_sym->sec)) {
+		const char *str = patched_sym->sec->data->d_buf + addend;
+
+		addend = elf_add_string(e->out, out_sym->sec, str);
+		if (addend == -1)
+			return -1;
+	}
+
+	if (!elf_create_reloc(e->out, sec, offset, out_sym, addend,
+			      reloc_type(patched_reloc)))
+		return -1;
+
+	return 0;
+}
+
+/* Copy all relocs needed for a symbol's contents */
+static int clone_sym_relocs(struct elfs *e, struct symbol *patched_sym)
+{
+	struct section *patched_rsec = patched_sym->sec->rsec;
+	struct reloc *patched_reloc;
+	unsigned long start, end;
+	struct symbol *out_sym;
+
+	out_sym = patched_sym->clone;
+	if (!out_sym) {
+		ERROR("no clone for %s", patched_sym->name);
+		return -1;
+	}
+
+	if (!patched_rsec)
+		return 0;
+
+	if (!is_sec_sym(patched_sym) && !patched_sym->len)
+		return 0;
+
+	if (is_string_sec(patched_sym->sec))
+		return 0;
+
+	if (is_sec_sym(patched_sym)) {
+		start = 0;
+		end = sec_size(patched_sym->sec);
+	} else {
+		start = patched_sym->offset;
+		end = start + patched_sym->len;
+	}
+
+	for_each_reloc(patched_rsec, patched_reloc) {
+		unsigned long offset;
+
+		if (reloc_offset(patched_reloc) < start ||
+		    reloc_offset(patched_reloc) >= end)
+			continue;
+
+		/*
+		 * Skip any reloc referencing .altinstr_aux.  Its code is
+		 * always patched by alternatives.  See ALTERNATIVE_TERNARY().
+		 */
+		if (patched_reloc->sym->sec &&
+		    !strcmp(patched_reloc->sym->sec->name, ".altinstr_aux"))
+			continue;
+
+		if (convert_reloc_sym(e->patched, patched_reloc)) {
+			ERROR_FUNC(patched_rsec->base, reloc_offset(patched_reloc),
+				   "failed to convert reloc sym '%s' to its proper format",
+				   patched_reloc->sym->name);
+			return -1;
+		}
+
+		offset = out_sym->offset + (reloc_offset(patched_reloc) - patched_sym->offset);
+
+		if (clone_reloc(e, patched_reloc, out_sym->sec, offset))
+			return -1;
+	}
+	return 0;
+
+}
+
+static int create_fake_symbol(struct elf *elf, struct section *sec,
+			      unsigned long offset, size_t size)
+{
+	char name[SYM_NAME_LEN];
+	unsigned int type;
+	static int ctr;
+	char *c;
+
+	if (snprintf_check(name, SYM_NAME_LEN, "%s_%d", sec->name, ctr++))
+		return -1;
+
+	for (c = name; *c; c++)
+		if (*c == '.')
+			*c = '_';
+
+	/*
+	 * STT_NOTYPE: Prevent objtool from validating .altinstr_replacement
+	 *	       while still allowing objdump to disassemble it.
+	 */
+	type = is_text_sec(sec) ? STT_NOTYPE : STT_OBJECT;
+	return elf_create_symbol(elf, name, sec, STB_LOCAL, type, offset, size) ? 0 : -1;
+}
+
+/*
+ * Special sections (alternatives, etc) are basically arrays of structs.
+ * For all the special sections, create a symbol for each struct entry.  This
+ * is a bit cumbersome, but it makes the extracting of the individual entries
+ * much more straightforward.
+ *
+ * There are three ways to identify the entry sizes for a special section:
+ *
+ * 1) ELF section header sh_entsize: Ideally this would be used almost
+ *    everywhere.  But unfortunately the toolchains make it difficult.  The
+ *    assembler .[push]section directive syntax only takes entsize when
+ *    combined with SHF_MERGE.  But Clang disallows combining SHF_MERGE with
+ *    SHF_WRITE.  And some special sections do need to be writable.
+ *
+ *    Another place this wouldn't work is .altinstr_replacement, whose entries
+ *    don't have a fixed size.
+ *
+ * 2) ANNOTATE_DATA_SPECIAL: This is a lightweight objtool annotation which
+ *    points to the beginning of each entry.  The size of the entry is then
+ *    inferred by the location of the subsequent annotation (or end of
+ *    section).
+ *
+ * 3) Simple array of pointers: If the special section is just a basic array of
+ *    pointers, the entry size can be inferred by the number of relocations.
+ *    No annotations needed.
+ *
+ * Note I also tried to create per-entry symbols at the time of creation, in
+ * the original [inline] asm.  Unfortunately, creating uniquely named symbols
+ * is trickier than one might think, especially with Clang inline asm.  I
+ * eventually just gave up trying to make that work, in favor of using
+ * ANNOTATE_DATA_SPECIAL and creating the symbols here after the fact.
+ */
+static int create_fake_symbols(struct elf *elf)
+{
+	struct section *sec;
+	struct reloc *reloc;
+
+	/*
+	 * 1) Make symbols for all the ANNOTATE_DATA_SPECIAL entries:
+	 */
+
+	sec = find_section_by_name(elf, ".discard.annotate_data");
+	if (!sec || !sec->rsec)
+		return 0;
+
+	for_each_reloc(sec->rsec, reloc) {
+		unsigned long offset, size;
+		struct reloc *next_reloc;
+
+		if (annotype(elf, sec, reloc) != ANNOTYPE_DATA_SPECIAL)
+			continue;
+
+		offset = reloc_addend(reloc);
+
+		size = 0;
+		next_reloc = reloc;
+		for_each_reloc_continue(sec->rsec, next_reloc) {
+			if (annotype(elf, sec, next_reloc) != ANNOTYPE_DATA_SPECIAL ||
+			    next_reloc->sym->sec != reloc->sym->sec)
+				continue;
+
+			size = reloc_addend(next_reloc) - offset;
+			break;
+		}
+
+		if (!size)
+			size = sec_size(reloc->sym->sec) - offset;
+
+		if (create_fake_symbol(elf, reloc->sym->sec, offset, size))
+			return -1;
+	}
+
+	/*
+	 * 2) Make symbols for sh_entsize, and simple arrays of pointers:
+	 */
+
+	for_each_sec(elf, sec) {
+		unsigned int entry_size;
+		unsigned long offset;
+
+		if (!is_special_section(sec) || find_symbol_by_offset(sec, 0))
+			continue;
+
+		if (!sec->rsec) {
+			ERROR("%s: missing special section relocations", sec->name);
+			return -1;
+		}
+
+		entry_size = sec->sh.sh_entsize;
+		if (!entry_size) {
+			entry_size = arch_reloc_size(sec->rsec->relocs);
+			if (sec_size(sec) != entry_size * sec_num_entries(sec->rsec)) {
+				ERROR("%s: missing special section entsize or annotations", sec->name);
+				return -1;
+			}
+		}
+
+		for (offset = 0; offset < sec_size(sec); offset += entry_size) {
+			if (create_fake_symbol(elf, sec, offset, entry_size))
+				return -1;
+		}
+	}
+
+	return 0;
+}
+
+/* Keep a special section entry if it references an included function */
+static bool should_keep_special_sym(struct elf *elf, struct symbol *sym)
+{
+	struct reloc *reloc;
+
+	if (is_sec_sym(sym) || !sym->sec->rsec)
+		return false;
+
+	sym_for_each_reloc(elf, sym, reloc) {
+		if (convert_reloc_sym(elf, reloc))
+			continue;
+
+		if (is_func_sym(reloc->sym) && reloc->sym->included)
+			return true;
+	}
+
+	return false;
+}
+
+/*
+ * Klp relocations aren't allowed for __jump_table and .static_call_sites if
+ * the referenced symbol lives in a kernel module, because such klp relocs may
+ * be applied after static branch/call init, resulting in code corruption.
+ *
+ * Validate a special section entry to avoid that.  Note that an inert
+ * tracepoint is harmless enough, in that case just skip the entry and print a
+ * warning.  Otherwise, return an error.
+ *
+ * This is only a temporary limitation which will be fixed when livepatch adds
+ * support for submodules: fully self-contained modules which are embedded in
+ * the top-level livepatch module's data and which can be loaded on demand when
+ * their corresponding to-be-patched module gets loaded.  Then klp relocs can
+ * be retired.
+ *
+ * Return:
+ *   -1: error: validation failed
+ *    1: warning: tracepoint skipped
+ *    0: success
+ */
+static int validate_special_section_klp_reloc(struct elfs *e, struct symbol *sym)
+{
+	bool static_branch = !strcmp(sym->sec->name, "__jump_table");
+	bool static_call   = !strcmp(sym->sec->name, ".static_call_sites");
+	struct symbol *code_sym = NULL;
+	unsigned long code_offset = 0;
+	struct reloc *reloc;
+	int ret = 0;
+
+	if (!static_branch && !static_call)
+		return 0;
+
+	sym_for_each_reloc(e->patched, sym, reloc) {
+		const char *sym_modname;
+		struct export *export;
+
+		/* Static branch/call keys are always STT_OBJECT */
+		if (reloc->sym->type != STT_OBJECT) {
+
+			/* Save code location which can be printed below */
+			if (reloc->sym->type == STT_FUNC && !code_sym) {
+				code_sym = reloc->sym;
+				code_offset = reloc_addend(reloc);
+			}
+
+			continue;
+		}
+
+		if (!klp_reloc_needed(reloc))
+			continue;
+
+		export = find_export(reloc->sym);
+		if (export) {
+			sym_modname = export->mod;
+		} else {
+			sym_modname = find_modname(e);
+			if (!sym_modname)
+				return -1;
+		}
+
+		/* vmlinux keys are ok */
+		if (!strcmp(sym_modname, "vmlinux"))
+			continue;
+
+		if (static_branch) {
+			if (strstarts(reloc->sym->name, "__tracepoint_")) {
+				WARN("%s: disabling unsupported tracepoint %s",
+				     code_sym->name, reloc->sym->name + 13);
+				ret = 1;
+				continue;
+			}
+
+			ERROR("%s+0x%lx: unsupported static branch key %s.  Use static_key_enabled() instead",
+			      code_sym->name, code_offset, reloc->sym->name);
+			return -1;
+		}
+
+		/* static call */
+		if (strstarts(reloc->sym->name, "__SCK__tp_func_")) {
+			ret = 1;
+			continue;
+		}
+
+		ERROR("%s()+0x%lx: unsupported static call key %s.  Use KLP_STATIC_CALL() instead",
+		      code_sym->name, code_offset, reloc->sym->name);
+		return -1;
+	}
+
+	return ret;
+}
+
+static int clone_special_section(struct elfs *e, struct section *patched_sec)
+{
+	struct symbol *patched_sym;
+
+	/*
+	 * Extract all special section symbols (and their dependencies) which
+	 * reference included functions.
+	 */
+	sec_for_each_sym(patched_sec, patched_sym) {
+		int ret;
+
+		if (!is_object_sym(patched_sym))
+			continue;
+
+		if (!should_keep_special_sym(e->patched, patched_sym))
+			continue;
+
+		ret = validate_special_section_klp_reloc(e, patched_sym);
+		if (ret < 0)
+			return -1;
+		if (ret > 0)
+			continue;
+
+		if (!clone_symbol(e, patched_sym, true))
+			return -1;
+	}
+
+	return 0;
+}
+
+/* Extract only the needed bits from special sections */
+static int clone_special_sections(struct elfs *e)
+{
+	struct section *patched_sec;
+
+	if (create_fake_symbols(e->patched))
+		return -1;
+
+	for_each_sec(e->patched, patched_sec) {
+		if (is_special_section(patched_sec)) {
+			if (clone_special_section(e, patched_sec))
+				return -1;
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * Create __klp_objects and __klp_funcs sections which are intermediate
+ * sections provided as input to the patch module's init code for building the
+ * klp_patch, klp_object and klp_func structs for the livepatch API.
+ */
+static int create_klp_sections(struct elfs *e)
+{
+	size_t obj_size  = sizeof(struct klp_object_ext);
+	size_t func_size = sizeof(struct klp_func_ext);
+	struct section *obj_sec, *funcs_sec, *str_sec;
+	struct symbol *funcs_sym, *str_sym, *sym;
+	char sym_name[SYM_NAME_LEN];
+	unsigned int nr_funcs = 0;
+	const char *modname;
+	void *obj_data;
+	s64 addend;
+
+	obj_sec  = elf_create_section_pair(e->out, KLP_OBJECTS_SEC, obj_size, 0, 0);
+	if (!obj_sec)
+		return -1;
+
+	funcs_sec = elf_create_section_pair(e->out, KLP_FUNCS_SEC, func_size, 0, 0);
+	if (!funcs_sec)
+		return -1;
+
+	funcs_sym = elf_create_section_symbol(e->out, funcs_sec);
+	if (!funcs_sym)
+		return -1;
+
+	str_sec = elf_create_section(e->out, KLP_STRINGS_SEC, 0, 0,
+				     SHT_PROGBITS, 1,
+				     SHF_ALLOC | SHF_STRINGS | SHF_MERGE);
+	if (!str_sec)
+		return -1;
+
+	if (elf_add_string(e->out, str_sec, "") == -1)
+		return -1;
+
+	str_sym = elf_create_section_symbol(e->out, str_sec);
+	if (!str_sym)
+		return -1;
+
+	/* allocate klp_object_ext */
+	obj_data = elf_add_data(e->out, obj_sec, NULL, obj_size);
+	if (!obj_data)
+		return -1;
+
+	modname = find_modname(e);
+	if (!modname)
+		return -1;
+
+	/* klp_object_ext.name */
+	if (strcmp(modname, "vmlinux")) {
+		addend = elf_add_string(e->out, str_sec, modname);
+		if (addend == -1)
+			return -1;
+
+		if (!elf_create_reloc(e->out, obj_sec,
+				      offsetof(struct klp_object_ext, name),
+				      str_sym, addend, R_ABS64))
+			return -1;
+	}
+
+	/* klp_object_ext.funcs */
+	if (!elf_create_reloc(e->out, obj_sec, offsetof(struct klp_object_ext, funcs),
+			      funcs_sym, 0, R_ABS64))
+		return -1;
+
+	for_each_sym(e->out, sym) {
+		unsigned long offset = nr_funcs * func_size;
+		unsigned long sympos;
+		void *func_data;
+
+		if (!is_func_sym(sym) || sym->cold || !sym->clone || !sym->clone->changed)
+			continue;
+
+		/* allocate klp_func_ext */
+		func_data = elf_add_data(e->out, funcs_sec, NULL, func_size);
+		if (!func_data)
+			return -1;
+
+		/* klp_func_ext.old_name */
+		addend = elf_add_string(e->out, str_sec, sym->clone->twin->name);
+		if (addend == -1)
+			return -1;
+
+		if (!elf_create_reloc(e->out, funcs_sec,
+				      offset + offsetof(struct klp_func_ext, old_name),
+				      str_sym, addend, R_ABS64))
+			return -1;
+
+		/* klp_func_ext.new_func */
+		if (!elf_create_reloc(e->out, funcs_sec,
+				      offset + offsetof(struct klp_func_ext, new_func),
+				      sym, 0, R_ABS64))
+			return -1;
+
+		/* klp_func_ext.sympos */
+		BUILD_BUG_ON(sizeof(sympos) != sizeof_field(struct klp_func_ext, sympos));
+		sympos = find_sympos(e->orig, sym->clone->twin);
+		if (sympos == ULONG_MAX)
+			return -1;
+		memcpy(func_data + offsetof(struct klp_func_ext, sympos), &sympos,
+		       sizeof_field(struct klp_func_ext, sympos));
+
+		nr_funcs++;
+	}
+
+	/* klp_object_ext.nr_funcs */
+	BUILD_BUG_ON(sizeof(nr_funcs) != sizeof_field(struct klp_object_ext, nr_funcs));
+	memcpy(obj_data + offsetof(struct klp_object_ext, nr_funcs), &nr_funcs,
+	       sizeof_field(struct klp_object_ext, nr_funcs));
+
+	/*
+	 * Find callback pointers created by KLP_PRE_PATCH_CALLBACK() and
+	 * friends, and add them to the klp object.
+	 */
+
+	if (snprintf_check(sym_name, SYM_NAME_LEN, KLP_PRE_PATCH_PREFIX "%s", modname))
+		return -1;
+
+	sym = find_symbol_by_name(e->out, sym_name);
+	if (sym) {
+		struct reloc *reloc;
+
+		reloc = find_reloc_by_dest(e->out, sym->sec, sym->offset);
+
+		if (!elf_create_reloc(e->out, obj_sec,
+				      offsetof(struct klp_object_ext, callbacks) +
+				      offsetof(struct klp_callbacks, pre_patch),
+				      reloc->sym, reloc_addend(reloc), R_ABS64))
+			return -1;
+	}
+
+	if (snprintf_check(sym_name, SYM_NAME_LEN, KLP_POST_PATCH_PREFIX "%s", modname))
+		return -1;
+
+	sym = find_symbol_by_name(e->out, sym_name);
+	if (sym) {
+		struct reloc *reloc;
+
+		reloc = find_reloc_by_dest(e->out, sym->sec, sym->offset);
+
+		if (!elf_create_reloc(e->out, obj_sec,
+				      offsetof(struct klp_object_ext, callbacks) +
+				      offsetof(struct klp_callbacks, post_patch),
+				      reloc->sym, reloc_addend(reloc), R_ABS64))
+			return -1;
+	}
+
+	if (snprintf_check(sym_name, SYM_NAME_LEN, KLP_PRE_UNPATCH_PREFIX "%s", modname))
+		return -1;
+
+	sym = find_symbol_by_name(e->out, sym_name);
+	if (sym) {
+		struct reloc *reloc;
+
+		reloc = find_reloc_by_dest(e->out, sym->sec, sym->offset);
+
+		if (!elf_create_reloc(e->out, obj_sec,
+				      offsetof(struct klp_object_ext, callbacks) +
+				      offsetof(struct klp_callbacks, pre_unpatch),
+				      reloc->sym, reloc_addend(reloc), R_ABS64))
+			return -1;
+	}
+
+	if (snprintf_check(sym_name, SYM_NAME_LEN, KLP_POST_UNPATCH_PREFIX "%s", modname))
+		return -1;
+
+	sym = find_symbol_by_name(e->out, sym_name);
+	if (sym) {
+		struct reloc *reloc;
+
+		reloc = find_reloc_by_dest(e->out, sym->sec, sym->offset);
+
+		if (!elf_create_reloc(e->out, obj_sec,
+				      offsetof(struct klp_object_ext, callbacks) +
+				      offsetof(struct klp_callbacks, post_unpatch),
+				      reloc->sym, reloc_addend(reloc), R_ABS64))
+			return -1;
+	}
+
+	return 0;
+}
+
+/*
+ * Copy all .modinfo import_ns= tags to ensure all namespaced exported symbols
+ * can be accessed via normal relocs.
+ */
+static int copy_import_ns(struct elfs *e)
+{
+	struct section *patched_sec, *out_sec = NULL;
+	char *import_ns, *data_end;
+
+	patched_sec = find_section_by_name(e->patched, ".modinfo");
+	if (!patched_sec)
+		return 0;
+
+	import_ns = patched_sec->data->d_buf;
+	if (!import_ns)
+		return 0;
+
+	for (data_end = import_ns + sec_size(patched_sec);
+	     import_ns < data_end;
+	     import_ns += strlen(import_ns) + 1) {
+
+		import_ns = memmem(import_ns, data_end - import_ns, "import_ns=", 10);
+		if (!import_ns)
+			return 0;
+
+		if (!out_sec) {
+			out_sec = find_section_by_name(e->out, ".modinfo");
+			if (!out_sec) {
+				out_sec = elf_create_section(e->out, ".modinfo", 0,
+							     patched_sec->sh.sh_entsize,
+							     patched_sec->sh.sh_type,
+							     patched_sec->sh.sh_addralign,
+							     patched_sec->sh.sh_flags);
+				if (!out_sec)
+					return -1;
+			}
+		}
+
+		if (!elf_add_data(e->out, out_sec, import_ns, strlen(import_ns) + 1))
+			return -1;
+	}
+
+	return 0;
+}
+
+int cmd_klp_diff(int argc, const char **argv)
+{
+	struct elfs e = {0};
+
+	argc = parse_options(argc, argv, klp_diff_options, klp_diff_usage, 0);
+	if (argc != 3)
+		usage_with_options(klp_diff_usage, klp_diff_options);
+
+	objname = argv[0];
+
+	e.orig = elf_open_read(argv[0], O_RDONLY);
+	e.patched = elf_open_read(argv[1], O_RDONLY);
+	e.out = NULL;
+
+	if (!e.orig || !e.patched)
+		return -1;
+
+	if (read_exports())
+		return -1;
+
+	if (read_sym_checksums(e.orig))
+		return -1;
+
+	if (read_sym_checksums(e.patched))
+		return -1;
+
+	if (correlate_symbols(&e))
+		return -1;
+
+	if (mark_changed_functions(&e))
+		return 0;
+
+	e.out = elf_create_file(&e.orig->ehdr, argv[2]);
+	if (!e.out)
+		return -1;
+
+	if (clone_included_functions(&e))
+		return -1;
+
+	if (clone_special_sections(&e))
+		return -1;
+
+	if (create_klp_sections(&e))
+		return -1;
+
+	if (copy_import_ns(&e))
+		return -1;
+
+	if  (elf_write(e.out))
+		return -1;
+
+	return elf_close(e.out);
+}
diff --git a/tools/objtool/objtool.c b/tools/objtool/objtool.c
index 5c8b974ad0f9..c8f611c1320d 100644
--- a/tools/objtool/objtool.c
+++ b/tools/objtool/objtool.c
@@ -16,8 +16,6 @@
 #include <objtool/objtool.h>
 #include <objtool/warn.h>
 
-bool help;
-
 static struct objtool_file file;
 
 struct objtool_file *objtool_open_read(const char *filename)
@@ -71,6 +69,39 @@ int objtool_pv_add(struct objtool_file *f, int idx, struct symbol *func)
 	return 0;
 }
 
+char *top_level_dir(const char *file)
+{
+	ssize_t len, self_len, file_len;
+	char self[PATH_MAX], *str;
+	int i;
+
+	len = readlink("/proc/self/exe", self, sizeof(self) - 1);
+	if (len <= 0)
+		return NULL;
+	self[len] = '\0';
+
+	for (i = 0; i < 3; i++) {
+		char *s = strrchr(self, '/');
+		if (!s)
+			return NULL;
+		*s = '\0';
+	}
+
+	self_len = strlen(self);
+	file_len = strlen(file);
+
+	str = malloc(self_len + file_len + 2);
+	if (!str)
+		return NULL;
+
+	memcpy(str, self, self_len);
+	str[self_len] = '/';
+	strcpy(str + self_len + 1, file);
+
+	return str;
+}
+
+
 int main(int argc, const char **argv)
 {
 	static const char *UNUSED = "OBJTOOL_NOT_IMPLEMENTED";
@@ -79,5 +110,11 @@ int main(int argc, const char **argv)
 	exec_cmd_init("objtool", UNUSED, UNUSED, UNUSED);
 	pager_init(UNUSED);
 
+	if (argc > 1 && !strcmp(argv[1], "klp")) {
+		argc--;
+		argv++;
+		return cmd_klp(argc, argv);
+	}
+
 	return objtool_run(argc, argv);
 }
diff --git a/tools/objtool/sync-check.sh b/tools/objtool/sync-check.sh
index 86d64e3ac6f7..e38167ca56a9 100755
--- a/tools/objtool/sync-check.sh
+++ b/tools/objtool/sync-check.sh
@@ -17,6 +17,7 @@ arch/x86/include/asm/emulate_prefix.h
 arch/x86/lib/x86-opcode-map.txt
 arch/x86/tools/gen-insn-attr-x86.awk
 include/linux/interval_tree_generic.h
+include/linux/livepatch_external.h
 include/linux/static_call_types.h
 "
 
diff --git a/tools/objtool/weak.c b/tools/objtool/weak.c
index d83f607733b0..d6562f292259 100644
--- a/tools/objtool/weak.c
+++ b/tools/objtool/weak.c
@@ -8,6 +8,8 @@
 #include <stdbool.h>
 #include <errno.h>
 #include <objtool/objtool.h>
+#include <objtool/arch.h>
+#include <objtool/builtin.h>
 
 #define UNSUPPORTED(name)						\
 ({									\
@@ -24,3 +26,8 @@ int __weak orc_create(struct objtool_file *file)
 {
 	UNSUPPORTED("ORC");
 }
+
+int __weak cmd_klp(int argc, const char **argv)
+{
+	UNSUPPORTED("klp");
+}