Use the uncompressed kernel file on arm and aarch to detect kernel version

This is due to file cannot read out the kernel version on these.

Many thanks to Alexander Graf finding this in old SUSE mkinitrd code.
Converted by Thomas Renninger.

Signed-off-by: Thomas Renninger <trenn@suse.de>

https://bugzilla.suse.com/show_bug.cgi?id=908454
Signed-off-by: Thomas Renninger <trenn@suse.de>

mkinitrd-suse.sh

@@ -145,6 +145,33 @@ is_xen_kernel() {
     return
 }
 
+# kernel_image_gz_from_image() and kernel_version_from_image() are helpers
+# for arm* kernels which produce zImage files which cannot be read from
+# get_kernel_version -> get rid of this workaround if possible
+kernel_image_gz_from_image() {
+    local arch=$(uname -i)
+    local r=${1}.gz
+
+    # uImage kernels can't be extracted directly. Use the vmlinux.gz instead
+    r=${r//uImage/vmlinux}
+
+    # on ARM a zImage can't be extracted directly. Other platforms define it
+    # as a gzipped vmlinux file, but not ARM. So only on ARM, use vmlinux.gz.
+    if [[ $arch =~ arm ]] || [[ $arch =~ aarch ]]; then
+        r=${r//zImage/vmlinux}
+    fi
+
+    echo $r
+}
+
+kernel_version_from_image() {
+    local kernel_image="$1" kernel_image_gz=$(kernel_image_gz_from_image "$1")
+
+    if get_kernel_version "$kernel_image" 2>/dev/null; then
+        return
+    fi
+    get_kernel_version "$kernel_image_gz" 2>/dev/null
+}
 
 # Taken over from SUSE mkinitrd
 default_kernel_images() {
@@ -183,7 +210,8 @@ default_kernel_images() {
 
         [ -L "$boot_dir/$kernel_image" ] && continue
         [ "${kernel_image%%.gz}" != "$kernel_image" ] && continue
-        kernel_version=$(/usr/bin/get_kernel_version \
+
+        kernel_version=$(kernel_version_from_image \
                          $boot_dir/$kernel_image 2> /dev/null)
         initrd_image=$(echo $kernel_image | sed -e "s|${regex}|initrd|")
         if [ "$kernel_image" != "$initrd_image" -a \