modsig: differentiate between ephemeral and persistent key names

Using the same name for ephemeral and "persistent" keys results
in deleting the "persistent" key.  This patch renames the normal
kbuild asymmetric key pair name to "default_signing_key" and the
ephemeral key pair name to "ephemeral_signing_key".

Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
diff --git a/Makefile b/Makefile
index d0dd777..525f512 100644
--- a/Makefile
+++ b/Makefile
@@ -721,15 +721,17 @@
 export KBUILD_MODSIG := 0
 
 ifeq ($(CONFIG_MODULE_SIG),y)
-MODSECKEY = ./signing_key.priv
-MODPUBKEY = ./signing_key.x509
-
 # Use 'make MODSIG=1 modules_install' to use ephemeral keys for module signing
 ifeq ("$(origin MODSIG)", "command line")
 KBUILD_MODSIG := $(MODSIG)
+MODSECKEY = ./ephemeral_signing_key.priv
+MODPUBKEY = ./ephemeral_signing_key.x509
+else
+MODSECKEY = ./default_signing_key.priv
+MODPUBKEY = ./default_signing_key.x509
 endif
 
-export MODPUBKEY
+export MODPUBKEY MODSECKEY
 mod_sign_cmd = perl $(srctree)/scripts/sign-file $(MODSECKEY) $(MODPUBKEY)
 else
 mod_sign_cmd = true
@@ -1037,7 +1039,9 @@
                   arch/*/include/generated
 MRPROPER_FILES += .config .config.old .version .old_version $(version_h) \
 		  Module.symvers tags TAGS cscope* GPATH GTAGS GRTAGS GSYMS \
-		  signing_key.priv signing_key.x509 x509.genkey		\
+		  default_signing_key.priv default_signing_key.x509	\
+		  ephemeral_signing_key.priv ephemeral_signing_key.x509 \
+		  signing_key.x509 x509.genkey				\
 		  extra_certificates signing_key.x509.keyid		\
 		  signing_key.x509.signer
 
diff --git a/kernel/Makefile b/kernel/Makefile
index 86e3285..34107d9 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -139,7 +139,11 @@
 extra_certificates:
 	touch $@
 
-kernel/modsign_pubkey.o: signing_key.x509 extra_certificates
+signing_key.x509: FORCE
+	ln -fs $(MODPUBKEY) $@
+	touch $@
+
+kernel/modsign_pubkey.o: $(MODPUBKEY) signing_key.x509 extra_certificates 
 
 ###############################################################################
 #
@@ -168,7 +172,7 @@
 $(error Could not determine digest type to use from kernel config)
 endif
 
-signing_key.priv signing_key.x509: x509.genkey
+$(MODSECKEY) $(MODPUBKEY): x509.genkey
 	@echo "###"
 	@echo "### Now generating an X.509 key pair to be used for signing modules."
 	@echo "###"
@@ -179,8 +183,8 @@
 	@echo "###"
 	openssl req -new -nodes -utf8 $(sign_key_with_hash) -days 36500 -batch \
 		-x509 -config x509.genkey \
-		-outform DER -out signing_key.x509 \
-		-keyout signing_key.priv
+		-outform DER -out $(MODPUBKEY) \
+		-keyout $(MODSECKEY)
 	@echo "###"
 	@echo "### Key pair generated."
 	@echo "###"