buildextend-live: add readonly kargs file for 'coreos-installer iso k…

…arg reset'

Signed-off-by: Nikita Dubrovskii <nikita@linux.ibm.com>

src/cmd-buildextend-live

@@ -317,6 +317,7 @@ def generate_iso():
     kargs = ' '.join(kargs_array)
     print(f'Substituting ISO kernel arguments: {kargs}')
 
+    default_kargs = ''
     files_with_karg_embed_areas = {}
     karg_embed_area_length = 0
     # Grab all the contents from the live dir from the configs
@@ -341,6 +342,13 @@ def generate_iso():
                 buf = newbuf
                 karg_area_end = re.search(r'(#+) COREOS_KARG_EMBED_AREA\n', buf)
                 if karg_area_end is not None:
+                    if len(default_kargs) == 0:
+                        default_kargs = buf[karg_area_start.start():karg_area_end.end()]
+                        files_with_karg_embed_areas['.cmdline'] = 0
+                        cmdline = os.path.join(tmpisoroot, '.cmdline')
+                        with open(cmdline, 'w') as fh:
+                            fh.write(default_kargs if len(default_kargs) != 0 else kargs)
+
                     length = karg_area_end.start() + len(karg_area_end[1]) - karg_area_start.start()
                     files_with_karg_embed_areas[filename] = karg_area_start.start()
                     if karg_embed_area_length == 0:
@@ -519,15 +527,15 @@ def generate_iso():
         ISO_SYSTEM_AREA_SIZE = 32768
 
         # number of karg files we allow for in the format
-        MAX_KARG_FILES = 6
+        MAX_KARG_FILES = 7
         assert len(files_with_karg_embed_areas) <= MAX_KARG_FILES
 
         # these can really never change without ratcheting on the
         # coreos-installer side first
         INITRDFMT = '<8s2Q'
         assert struct.calcsize(INITRDFMT) == 24
         KARGSFMT = f"<8s{MAX_KARG_FILES+1}Q"  # +1 for area length
-        assert struct.calcsize(KARGSFMT) == 64
+        assert struct.calcsize(KARGSFMT) == 72
 
         # Start of the Ignition padding within the ISO
         offset = file_offset_in_iso(isoinfo, ignition_img)