Fix meminfo and memstat for kernel>4.20

Fix meminfo and memstat to add support for kernel > 4.20.
The variable totalram_pages is changed to _totalram_pages.

Change-Id: I8ede274a64f748a96e572d1ef4c50325e3dda9f0
Signed-off-by: Shivendra Pratap <spratap@codeaurora.org>

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

@@ -142,7 +142,11 @@ class MemStats(RamParser):
 
     def print_mem_stats(self, out_mem_stat):
         # Total memory
-        total_mem = self.ramdump.read_word('totalram_pages')
+        if(self.ramdump.kernel_version > (4, 20, 0)):
+            total_mem = self.ramdump.read_word('_totalram_pages')
+        else:
+            total_mem = self.ramdump.read_word('totalram_pages')
+
         total_mem = self.pages_to_mb(total_mem)
 
         if (self.ramdump.kernel_version < (4, 9, 0)):

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

@@ -55,7 +55,11 @@ def do_dump_process_memory(ramdump):
 
     total_shmem_swap = get_shmem_swap_usage(ramdump)
     total_slab = slab_rec + slab_unrec
-    total_mem = ramdump.read_word('totalram_pages') * 4
+    if(ramdump.kernel_version > (4, 20, 0)):
+        total_mem = ramdump.read_word('_totalram_pages') * 4
+    else:
+        total_mem = ramdump.read_word('totalram_pages') * 4
+
     offset_comm = ramdump.field_offset('struct task_struct', 'comm')
     offset_signal = ramdump.field_offset('struct task_struct', 'signal')
     offset_adj = ramdump.field_offset('struct signal_struct', 'oom_score_adj')