kbuild: Support LOCALVERSION

Add LOCALVERSION so we can append strings that show up in uname
without having to fiddle with the Makefile and EXTRAVERSION, etc.

* localversion* files are read first
* config variable is appended last
* LOCALVERSION from the command line overrides all of this
* check is forced on build, since we can't really know when
  the config or environment options change.
Signed-off-by: Ian Wienand <ianw@gelato.unsw.edu.au>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

Makefile

@@ -141,7 +141,25 @@ VPATH		:= $(srctree)
 
 export srctree objtree VPATH TOPDIR
 
-KERNELRELEASE=$(VERSION).$(PATCHLEVEL).$(SUBLEVEL)$(EXTRAVERSION)
+nullstring :=
+space      := $(nullstring) # end of line
+
+# Take the contents of any files called localversion* and the config
+# variable CONFIG_LOCALVERSION and append them to KERNELRELEASE. Be
+# careful not to include files twice if building in the source
+# directory. LOCALVERSION from the command line override all of this
+
+ifeq ($(objtree),$(srctree))
+localversion-files := $(wildcard $(srctree)/localversion*)
+else
+localversion-files := $(wildcard $(objtree)/localversion* $(srctree)/localversion*)
+endif
+
+LOCALVERSION = $(subst $(space),, \
+	       $(shell cat /dev/null $(localversion-files)) \
+	       $(subst ",,$(CONFIG_LOCALVERSION)))
+
+KERNELRELEASE=$(VERSION).$(PATCHLEVEL).$(SUBLEVEL)$(EXTRAVERSION)$(LOCALVERSION)
 
 # SUBARCH tells the usermode build what the underlying arch is.  That is set
 # first, and if a usermode build is happening, the "ARCH=um" on the command
@@ -329,8 +347,8 @@ CFLAGS 		:= -Wall -Wstrict-prototypes -Wno-trigraphs \
 	  	   -fno-strict-aliasing -fno-common
 AFLAGS		:= -D__ASSEMBLY__
 
-export	VERSION PATCHLEVEL SUBLEVEL EXTRAVERSION KERNELRELEASE ARCH \
-	CONFIG_SHELL HOSTCC HOSTCFLAGS CROSS_COMPILE AS LD CC \
+export	VERSION PATCHLEVEL SUBLEVEL EXTRAVERSION LOCALVERSION KERNELRELEASE \
+	ARCH CONFIG_SHELL HOSTCC HOSTCFLAGS CROSS_COMPILE AS LD CC \
 	CPP AR NM STRIP OBJCOPY OBJDUMP MAKE AWK GENKSYMS PERL UTS_MACHINE \
 	HOSTCXX HOSTCXXFLAGS LDFLAGS_MODULE CHECK CHECKFLAGS
 
@@ -747,8 +765,8 @@ include/config/MARKER: include/linux/autoconf.h
 # Generate some files
 # ---------------------------------------------------------------------------
 
-#	version.h changes when $(KERNELRELEASE) etc change, as defined in
-#	this Makefile
+# KERNELRELEASE can change from a few different places, meaning version.h
+# needs to be updated, so this check is forced on all builds
 
 uts_len := 64
 
@@ -763,7 +781,7 @@ define filechk_version.h
 	)
 endef
 
-include/linux/version.h: Makefile
+include/linux/version.h: FORCE
 	$(call filechk,version.h)
 
 # ---------------------------------------------------------------------------

init/Kconfig

@@ -283,6 +283,16 @@ config CC_OPTIMIZE_FOR_SIZE
 
 	  If unsure, say N.
 
+config LOCALVERSION
+	string "Local Version"
+	help
+	  Append an extra string to the end of your kernel version.
+	  This will show up when you type uname, for example.
+	  The string you set here will be appended after the contents of=20
+	  any files with a filename matching localversion* in your=20
+	  object and source tree, in that order.  Your total string can
+	  be a maximum of 64 characters.
+
 endmenu		# General setup
 
 menu "Loadable module support"