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;
+	}