Build and package standalone falco kernel module

Start packaging (and building when necessary) a falco-specific kernel
module in falco releases. Previously, falco would depend on sysdig and
use its kernel module instead.

The kernel module was already templated to some degree in various
places, so we just had to change the templated name from
sysdig/sysdig-probe to falco/falco-probe.

In containers, run falco-probe-loader instead of
sysdig-probe-loader. This is actually a script in the sysdig repository
which is modified in https://github.com/draios/sysdig/pull/789, and uses
the filename to indicate what kernel module to build and/or load.

For the falco package itself, don't depend on sysdig any longer but instead
depend on dkms and its dependencies, using sysdig as a guide on the set
of required packages.

Additionally, for the package pre-install/post-install scripts start
running falco-probe-loader.

Finally, add a --version argument to falco so it can pass the desired
version string to falco-probe-loader.

scripts/CMakeLists.txt

@@ -1,5 +1,12 @@
+configure_file(debian/postinst.in debian/postinst)
+configure_file(debian/prerm.in debian/prerm)
+
 file(COPY "${PROJECT_SOURCE_DIR}/scripts/debian/falco"
 	DESTINATION "${PROJECT_BINARY_DIR}/scripts/debian")
 
 file(COPY "${PROJECT_SOURCE_DIR}/scripts/rpm/falco"
 	DESTINATION "${PROJECT_BINARY_DIR}/scripts/rpm")
+
+install(PROGRAMS ${SYSDIG_DIR}/scripts/sysdig-probe-loader
+	DESTINATION bin
+	RENAME falco-probe-loader)

scripts/debian/postinst

@@ -1,9 +0,0 @@
-#!/bin/sh
-set -e
-
-NAME=falco
-
-if [ -x "/etc/init.d/$NAME" ]; then
-        update-rc.d $NAME defaults >/dev/null
-fi
-

scripts/debian/postinst.in

@@ -0,0 +1,32 @@
+#!/bin/sh
+set -e
+
+DKMS_PACKAGE_NAME="@PACKAGE_NAME@"
+DKMS_VERSION="@PROBE_VERSION@"
+NAME="@PACKAGE_NAME@"
+
+postinst_found=0
+
+case "$1" in
+	configure)
+		for DKMS_POSTINST in /usr/lib/dkms/common.postinst /usr/share/$DKMS_PACKAGE_NAME/postinst; do
+			if [ -f $DKMS_POSTINST ]; then
+				$DKMS_POSTINST $DKMS_PACKAGE_NAME $DKMS_VERSION /usr/share/$DKMS_PACKAGE_NAME "" $2
+				postinst_found=1
+				break
+			fi
+		done
+		if [ "$postinst_found" -eq 0 ]; then
+			echo "ERROR: DKMS version is too old and $DKMS_PACKAGE_NAME was not"
+			echo "built with legacy DKMS support."
+			echo "You must either rebuild $DKMS_PACKAGE_NAME with legacy postinst"
+			echo "support or upgrade DKMS to a more current version."
+			exit 1
+		fi
+	;;
+esac
+
+if [ -x "/etc/init.d/$NAME" ]; then
+        update-rc.d $NAME defaults >/dev/null
+fi
+

scripts/debian/prerm

@@ -1,13 +0,0 @@
-#!/bin/sh
-set -e
-
-NAME=falco
-
-if [ -x "/etc/init.d/$NAME" ]; then
-		if [ -x "`which invoke-rc.d 2>/dev/null`" ]; then
-				invoke-rc.d $NAME stop || exit $?
-		else
-				/etc/init.d/$NAME stop || exit $?
-		fi
-fi
-

scripts/debian/prerm.in

@@ -0,0 +1,23 @@
+#!/bin/sh
+set -e
+
+NAME="@PACKAGE_NAME@"
+
+if [ -x "/etc/init.d/$NAME" ]; then
+		if [ -x "`which invoke-rc.d 2>/dev/null`" ]; then
+				invoke-rc.d $NAME stop || exit $?
+		else
+				/etc/init.d/$NAME stop || exit $?
+		fi
+fi
+
+DKMS_PACKAGE_NAME="@PACKAGE_NAME@"
+DKMS_VERSION="@PROBE_VERSION@"
+
+case "$1" in
+	remove|upgrade|deconfigure)
+		if [  "$(dkms status -m $DKMS_PACKAGE_NAME -v $DKMS_VERSION)" ]; then
+			dkms remove -m $DKMS_PACKAGE_NAME -v $DKMS_VERSION --all
+		fi
+	;;
+esac

scripts/rpm/postinstall

@@ -1 +1,15 @@
+dkms add -m falco -v %{version} --rpm_safe_upgrade
+if [ `uname -r | grep -c "BOOT"` -eq 0 ] && [ -e /lib/modules/`uname -r`/build/include ]; then
+	dkms build -m falco -v %{version}
+	dkms install --force -m falco -v %{version}
+elif [ `uname -r | grep -c "BOOT"` -gt 0 ]; then
+	echo -e ""
+	echo -e "Module build for the currently running kernel was skipped since you"
+	echo -e "are running a BOOT variant of the kernel."
+else
+	echo -e ""
+	echo -e "Module build for the currently running kernel was skipped since the"
+	echo -e "kernel source for this kernel does not seem to be installed."
+fi
+
 /sbin/chkconfig --add falco

scripts/rpm/preuninstall

@@ -2,3 +2,5 @@ if [ $1 = 0 ]; then
 	/sbin/service falco stop > /dev/null 2>&1
 	/sbin/chkconfig --del falco
 fi
+
+dkms remove -m falco -v %{version} --all --rpm_safe_upgrade