MODSIGN: Add modules_sign make target

If CONFIG_MODULE_SIG is set, and 'make modules_sign' is called then this
patch will cause the modules to get a signature appended.  The make target
is intended to be run after 'make modules_install', and will modify the
modules in-place in the installed location.  It can be used to produce
signed modules after they have been processed by distribution build
scripts.
Signed-off-by: Josh Boyer <jwboyer@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (minor typo fix)

Makefile

@@ -981,6 +981,12 @@ _modinst_post: _modinst_
 	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.fwinst obj=firmware __fw_modinst
 	$(call cmd,depmod)
 
+ifeq ($(CONFIG_MODULE_SIG), y)
+PHONY += modules_sign
+modules_sign:
+	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modsign
+endif
+
 else # CONFIG_MODULES
 
 # Modules not configured

scripts/Makefile.modsign

+# ==========================================================================
+# Signing modules
+# ==========================================================================
+
+PHONY := __modsign
+__modsign:
+
+include scripts/Kbuild.include
+
+__modules := $(sort $(shell grep -h '\.ko' /dev/null $(wildcard $(MODVERDIR)/*.mod)))
+modules := $(patsubst %.o,%.ko,$(wildcard $(__modules:.ko=.o)))
+
+PHONY += $(modules)
+__modsign: $(modules)
+	@:
+
+quiet_cmd_sign_ko = SIGN [M] $(2)/$(notdir $@)
+        cmd_sign_ko = $(mod_sign_cmd) $(2)/$(notdir $@)
+
+# Modules built outside the kernel source tree go into extra by default
+INSTALL_MOD_DIR ?= extra
+ext-mod-dir = $(INSTALL_MOD_DIR)$(subst $(patsubst %/,%,$(KBUILD_EXTMOD)),,$(@D))
+
+modinst_dir = $(if $(KBUILD_EXTMOD),$(ext-mod-dir),kernel/$(@D))
+
+$(modules):
+	$(call cmd,sign_ko,$(MODLIB)/$(modinst_dir))
+
+# Declare the contents of the .PHONY variable as phony.  We keep that
+# information in a variable se we can use it in if_changed and friends.
+
+.PHONY: $(PHONY)