kbuild: add option for stripping modules while installing them

Add option for stripping modules while installing them.

This function adds support for stripping modules while they are being
installed.  CONFIG_DEBUG_KERNEL (which will probably become more
popular as developers use kdump) causes the size of the installed
modules to grow by a factor of 9 or so.

Some kernel package systems solve this problem by stripping the debug
information from /lib/modules after running "make modules_install",
but that may not work for people who are installing directly into
/lib/modules --- root partitions that were sized to handle 16 megs
worth of modules may not be quite so happy with 145 megs of modules,
so the "make modules_install" never succeeds.

This patch allows such users to request modules_install to strip the
modules as they are installed.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

Documentation/kbuild/makefiles.txt

@@ -1123,6 +1123,14 @@ The top Makefile exports the following variables:
 	$(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE).  The user may
 	override this value on the command line if desired.
 
+    INSTALL_MOD_STRIP
+
+	If this variable is specified, will cause modules to be stripped
+	after they are installed.  If INSTALL_MOD_STRIP is '1', then the
+	default option --strip-debug will be used.  Otherwise,
+	INSTALL_MOD_STRIP will used as the option(s) to the strip command.
+
+
 === 8 Makefile language
 
 The kernel Makefiles are designed to run with GNU Make.  The Makefiles

Makefile

@@ -512,6 +512,23 @@ export	INSTALL_PATH ?= /boot
 MODLIB	= $(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE)
 export MODLIB
 
+#
+#  INSTALL_MOD_STRIP, if defined, will cause modules to be
+#  stripped after they are installed.  If INSTALL_MOD_STRIP is '1', then
+#  the default option --strip-debug will be used.  Otherwise,
+#  INSTALL_MOD_STRIP will used as the options to the strip command.
+
+ifdef INSTALL_MOD_STRIP
+ifeq ($(INSTALL_MOD_STRIP),1)
+mod_strip_cmd = $STRIP) --strip-debug
+else
+mod_strip_cmd = $(STRIP) $(INSTALL_MOD_STRIP)
+endif # INSTALL_MOD_STRIP=1
+else
+mod_strip_cmd = true
+endif # INSTALL_MOD_STRIP
+export mod_strip_cmd
+
 
 ifeq ($(KBUILD_EXTMOD),)
 core-y		+= kernel/ mm/ fs/ ipc/ security/ crypto/ block/

scripts/Makefile.modinst

@@ -17,7 +17,7 @@ __modinst: $(modules)
 	@:
 
 quiet_cmd_modules_install = INSTALL $@
-      cmd_modules_install = mkdir -p $(2); cp $@ $(2)
+      cmd_modules_install = mkdir -p $(2); cp $@ $(2) ; $(mod_strip_cmd) $(2)/$(notdir $@)
 
 # Modules built outside the kernel source tree go into extra by default
 INSTALL_MOD_DIR ?= extra