scripts/gdb: fix issue with dmesg.py and python 3.X

When built against Python 3, GDB differs in the return type for its
read_memory function, causing the lx-dmesg command to fail.

Now that we have an improved read_16() we can use the new
read_memoryview() abstraction to make lx-dmesg return valid data on both
current Python APIs

Tested with python 3.4 and 2.7
Tested with gdb 7.7

Link: http://lkml.kernel.org/r/28477b727ff7fe3101fd4e426060e8a68317a639.1462865983.git.jan.kiszka@siemens.com
Signed-off-by: Dom Cote <buzdelabuz2+git@gmail.com>
[kieran@bingham.xyz: Adjusted commit log to better reflect code changes]
Tested-by: Kieran Bingham <kieran@bingham.xyz> (Py2.7,Py3.4,GDB10)
Signed-off-by: Kieran Bingham <kieran@bingham.xyz>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/gdb/linux/dmesg.py

@@ -33,11 +33,12 @@ class LxDmesg(gdb.Command):
         if log_first_idx < log_next_idx:
             log_buf_2nd_half = -1
             length = log_next_idx - log_first_idx
-            log_buf = inf.read_memory(start, length)
+            log_buf = utils.read_memoryview(inf, start, length).tobytes()
         else:
             log_buf_2nd_half = log_buf_len - log_first_idx
-            log_buf = inf.read_memory(start, log_buf_2nd_half) + \
-                inf.read_memory(log_buf_addr, log_next_idx)
+            a = utils.read_memoryview(inf, start, log_buf_2nd_half)
+            b = utils.read_memoryview(inf, log_buf_addr, log_next_idx)
+            log_buf = a.tobytes() + b.tobytes()
 
         pos = 0
         while pos < log_buf.__len__():