ls_parse: Allow handling unknown blocks

The Xen linker script has a block "PHDRS" that results in a failure
of the ls_parse.py script. As there is nothing to be done in that
script for that block, this commit adds an empty handler for this
block name. In case more blocks should be added, only the regular
expression to match the blocks has to be modified.

scripts/ls_parse.py

@@ -81,6 +81,7 @@ def get_linker_script_data(script):
     text = re.sub(r"/\*.*?\*/", " ", text)
 
     close_brace     = re.compile(r"\s}(\s*>\s*\w+)?")
+    uwnknown_cmd    = re.compile(r"\sPHDRS\s*{")  # only this pattern for now, more might follow!
     memory_cmd      = re.compile(r"\sMEMORY\s*{")
     sections_cmd    = re.compile(r"\sSECTIONS\s*{")
     assign_current  = re.compile(r"\s(?P<sym>\w+)\s*=\s*\.\s*;")
@@ -102,6 +103,7 @@ def get_linker_script_data(script):
     # with the info gleaned from the matched string.
     jump_table = {
         close_brace     : close_brace_fun,
+        uwnknown_cmd    : unknown_cmd_fun,
         memory_cmd      : memory_cmd_fun,
         sections_cmd    : sections_cmd_fun,
         assign_current  : assign_current_fun,
@@ -146,6 +148,7 @@ def get_linker_script_data(script):
     state["MEM"] = False
     state["SEC"] = False
     state["DEF"] = False
+    state["UNKNOWN"] = False
 
     i = 0
     while i < len(text):
@@ -274,6 +277,9 @@ def close_brace_fun(state, _, buf):
     elif state["MEM"]:
         info("Closing memory command")
         state["MEM"] = False
+    elif state["UNKNOWN"]:
+        info("Closing unknown command")
+        state["UNKNOWN"] = False
     else:
         error("Not in block\n%s", buf)
         exit(1)
@@ -306,6 +312,9 @@ def memory_cmd_fun(state, _, buf):
     asrt(not state["MEM"], "encountered MEMORY twice", buf)
     state["MEM"] = True
 
+def unknown_cmd_fun(state, _, buf):
+    asrt(not state["MEM"], "encountered UNKNOWN twice", buf)
+    state["UNKNOWN"] = True
 
 def match_up_expr_assigns(state):
     blocks = set([data["origin"] for data in state["expr-assigns"]])