livepatch/klp-build: Introduce klp-build script for generating livepatch modules

Add a klp-build script which automates the generation of a livepatch
module from a source .patch file by performing the following steps:

  - Builds an original kernel with -function-sections and
    -fdata-sections, plus objtool function checksumming.

  - Applies the .patch file and rebuilds the kernel using the same
    options.

  - Runs 'objtool klp diff' to detect changed functions and generate
    intermediate binary diff objects.

  - Builds a kernel module which links the diff objects with some
    livepatch module init code (scripts/livepatch/init.c).

  - Finalizes the livepatch module (aka work around linker wreckage)
    using 'objtool klp post-link'.

Acked-by: Petr Mladek <pmladek@suse.com>
Tested-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

scripts/Makefile.lib

@@ -173,6 +173,7 @@ ifdef CONFIG_OBJTOOL
 
 objtool := $(objtree)/tools/objtool/objtool
 
+objtool-args-$(CONFIG_KLP_BUILD)			+= --checksum
 objtool-args-$(CONFIG_HAVE_JUMP_LABEL_HACK)		+= --hacks=jump_label
 objtool-args-$(CONFIG_HAVE_NOINSTR_HACK)		+= --hacks=noinstr
 objtool-args-$(CONFIG_MITIGATION_CALL_DEPTH_TRACKING)	+= --hacks=skylake

scripts/livepatch/fix-patch-lines

@@ -23,7 +23,7 @@ BEGIN {
 
 	in_hunk = 1
 
-	# for @@ -1,3 +1,4 @@:
+	# @@ -1,3 +1,4 @@:
 	#   1: line number in old file
 	#   3: how many lines the hunk covers in old file
 	#   1: line number in new file

tools/objtool/klp-diff.c

@@ -241,10 +241,12 @@ static struct symbol *next_file_symbol(struct elf *elf, struct symbol *sym)
 static bool is_uncorrelated_static_local(struct symbol *sym)
 {
 	static const char * const vars[] = {
-		"__key.",
-		"__warned.",
 		"__already_done.",
 		"__func__.",
+		"__key.",
+		"__warned.",
+		"_entry.",
+		"_entry_ptr.",
 		"_rs.",
 		"descriptor.",
 		"CSWTCH.",