scripts/gen_image_generic.sh: generate reproducible EFI filesystem

Generate FAT filesystem for EFI boot in a reproducible way:
 * use '--invariant' option of mkfs.fat
 * set timestamps of all files to SOURCE_DATE_EPOCH
 * make sure files are ordered locale-independent

Signed-off-by: Daniel Golle <[email protected]>

scripts/gen_image_generic.sh

@@ -31,8 +31,9 @@ dd if="$ROOTFSIMAGE" of="$OUTPUT" bs=512 seek="$ROOTFSOFFSET" conv=notrunc
 
 if [ -n "$GUID" ]; then
     [ -n "$PADDING" ] && dd if=/dev/zero of="$OUTPUT" bs=512 seek="$((ROOTFSOFFSET + ROOTFSSIZE))" conv=notrunc count="$sect"
-    mkfs.fat -n kernel -C "$OUTPUT.kernel" -S 512 "$((KERNELSIZE / 1024))"
-    mcopy -s -i "$OUTPUT.kernel" "$KERNELDIR"/* ::/
+    mkfs.fat --invariant -n kernel -C "$OUTPUT.kernel" -S 512 "$((KERNELSIZE / 1024))"
+    [ "$SOURCE_DATE_EPOCH" ] && find "$KERNELDIR"/ -mindepth 1 -execdir touch -hcd "@${SOURCE_DATE_EPOCH}" "{}" +
+    LC_ALL=C mcopy -m -s -i "$OUTPUT.kernel" "$KERNELDIR"/* ::/
 else
     make_ext4fs -J -L kernel -l "$KERNELSIZE" ${SOURCE_DATE_EPOCH:+-T ${SOURCE_DATE_EPOCH}} "$OUTPUT.kernel" "$KERNELDIR"
 fi