linux-ramdump-parser-v2: Improve slabinfo robustness

Sometimes the slabinfo data structures may be corrupt because of software
error or when the ramdumps were collected. Detect this bettter to
avoid looping forever or going out of bounds.

Change-Id: I5b0202048d61b937355d7e3d2b2b18f629529657

linux-ramdump-parser-v2/parsers/slabinfo.py

-# Copyright (c) 2012-2013, The Linux Foundation. All rights reserved.
+# Copyright (c) 2012-2014, The Linux Foundation. All rights reserved.
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License version 2 and
@@ -11,7 +11,7 @@
 
 import re
 
-from mm import page_address
+from mm import page_address, pfn_to_page
 from print_out import print_out_str
 from parser_util import register_parser, RamParser
 
@@ -39,13 +39,15 @@ class Slabinfo(RamParser):
         freelist = self.ramdump.read_word(page + freelist_offset)
         p = freelist
         addr = page_address(self.ramdump, page)
+        seen = []
         if addr is None:
             return
-        while p != 0 and p is not None:
+        while p != 0 and p is not None and p not in seen:
             idx = self.slab_index(self.ramdump, p, addr, slab)
             if idx >= len(bitarray) or idx < 0:
                 return
             bitarray[idx] = 1
+            seen.append(p)
             p = self.get_free_pointer(self.ramdump, slab, p)
 
     def get_track(self, ramdump, slab, obj, track_type):
@@ -136,15 +138,24 @@ class Slabinfo(RamParser):
 
     def print_slab_page_info(self, ramdump, slab, slab_node, start, out_file):
         page = self.ramdump.read_word(start)
+        seen = []
         if page == 0:
             return
         slab_lru_offset = self.ramdump.field_offset('struct page', 'lru')
         page_flags_offset = self.ramdump.field_offset('struct page', 'flags')
         slab_node_offset = self.ramdump.field_offset(
             'struct kmem_cache', 'size')
+        max_pfn_addr = self.ramdump.addr_lookup('max_pfn')
+        max_pfn = self.ramdump.read_word(max_pfn_addr)
+        max_page = pfn_to_page(ramdump, max_pfn)
         while page != start:
             if page is None:
                 return
+            if page in seen:
+               return
+            if page > max_page:
+               return
+            seen.append(page)
             page = page - slab_lru_offset
             page_flags = self.ramdump.read_word(page + page_flags_offset)
             page_addr = page_address(self.ramdump, page)