Kernel: T5641: enable module compression to save disk space

After signing the Linux Kernel modules with the ephemeral key, proceed
by compressing the Kernel modules with xz to reduce the final ISO image
size.

Initial tests have shown a size reduction by 60MiB.

1 files changed, 15 insertions, 2 deletions

diff --git a/scripts/package-build/linux-kernel/sign-modules.sh b/scripts/package-build/linux-kernel/sign-modules.sh
index cfb368eb..1fb82165 100755
--- a/scripts/package-build/linux-kernel/sign-modules.sh
+++ b/scripts/package-build/linux-kernel/sign-modules.sh
@@ -1,15 +1,28 @@
-#!/bin/sh
+#!/bin/sh -x
 
 BASE_DIR=$(dirname $0)
 MODULE_DIR=$1
+# Pass "--keep" as $2 to retain the uncompressed, signed .ko next to the
+# .ko.xz it produces. Needed by callers whose build system tracks the
+# uncompressed .ko as a build output (e.g. CMake custom commands) and
+# would otherwise consider it missing and regenerate an unsigned copy.
+KEEP_UNCOMPRESSED=$2
 . ${BASE_DIR}/kernel-vars
 
 SIGN_FILE="${KERNEL_DIR}/scripts/sign-file"
+CONFIG_FILE="${KERNEL_DIR}/.config"
 
 if [ -f ${EPHEMERAL_KEY} ] && [ -f ${EPHEMERAL_CERT} ]; then
     find ${MODULE_DIR} -type f -name \*.ko | while read MODULE; do
       echo "I: Signing ${MODULE} ..."
       ${SIGN_FILE} sha512 ${EPHEMERAL_KEY} ${EPHEMERAL_CERT} ${MODULE}
+      if [ -f "$CONFIG_FILE" ] && grep -qx "CONFIG_MODULE_COMPRESS_XZ=y" "$CONFIG_FILE"; then
+          if [ "${KEEP_UNCOMPRESSED}" = "--keep" ]; then
+              xz --compress --keep ${MODULE}
+          else
+              xz --compress ${MODULE}
+          fi
+      fi
     done
+    find ${MODULE_DIR}
 fi
-