scripts/gdb/linux/dmesg.py

   1 #
   2 # gdb helper commands and functions for Linux kernel debugging
   3 #
   4 #  kernel log buffer dump
   5 #
   6 # Copyright (c) Siemens AG, 2011, 2012
   7 #
   8 # Authors:
   9 #  Jan Kiszka <jan.kiszka@siemens.com>
  10 #
  11 # This work is licensed under the terms of the GNU GPL version 2.
  12 #
  13
  14 import gdb
  15 import sys
  16
  17 from linux import utils
  18
  19 printk_log_type = utils.CachedType("struct printk_log")
  20
  21
  22 class LxDmesg(gdb.Command):
  23     """Print Linux kernel log buffer."""
  24
  25     def __init__(self):
  26         super(LxDmesg, self).__init__("lx-dmesg", gdb.COMMAND_DATA)
  27
  28     def invoke(self, arg, from_tty):
  29         log_buf_addr = int(str(gdb.parse_and_eval(
  30             "(void *)'printk.c'::log_buf")).split()[0], 16)
  31         log_first_idx = int(gdb.parse_and_eval("'printk.c'::log_first_idx"))
  32         log_next_idx = int(gdb.parse_and_eval("'printk.c'::log_next_idx"))
  33         log_buf_len = int(gdb.parse_and_eval("'printk.c'::log_buf_len"))
  34
  35         inf = gdb.inferiors()[0]
  36         start = log_buf_addr + log_first_idx
  37         if log_first_idx < log_next_idx:
  38             log_buf_2nd_half = -1
  39             length = log_next_idx - log_first_idx
  40             log_buf = utils.read_memoryview(inf, start, length).tobytes()
  41         else:
  42             log_buf_2nd_half = log_buf_len - log_first_idx
  43             a = utils.read_memoryview(inf, start, log_buf_2nd_half)
  44             b = utils.read_memoryview(inf, log_buf_addr, log_next_idx)
  45             log_buf = a.tobytes() + b.tobytes()
  46
  47         length_offset = printk_log_type.get_type()['len'].bitpos // 8
  48         text_len_offset = printk_log_type.get_type()['text_len'].bitpos // 8
  49         time_stamp_offset = printk_log_type.get_type()['ts_nsec'].bitpos // 8
  50         text_offset = printk_log_type.get_type().sizeof
  51
  52         pos = 0
  53         while pos < log_buf.__len__():
  54             length = utils.read_u16(log_buf, pos + length_offset)
  55             if length == 0:
  56                 if log_buf_2nd_half == -1:
  57                     gdb.write("Corrupted log buffer!\n")
  58                     break
  59                 pos = log_buf_2nd_half
  60                 continue
  61
  62             text_len = utils.read_u16(log_buf, pos + text_len_offset)
  63             text_start = pos + text_offset
  64             text = log_buf[text_start:text_start + text_len].decode(
  65                 encoding='utf8', errors='replace')
  66             time_stamp = utils.read_u64(log_buf, pos + time_stamp_offset)
  67
  68             for line in text.splitlines():
  69                 msg = u"[{time:12.6f}] {line}\n".format(
  70                     time=time_stamp / 1000000000.0,
  71                     line=line)
  72                 # With python2 gdb.write will attempt to convert unicode to
  73                 # ascii and might fail so pass an utf8-encoded str instead.
  74                 if sys.hexversion < 0x03000000:
  75                     msg = msg.encode(encoding='utf8', errors='replace')
  76                 gdb.write(msg)
  77
  78             pos += length
  79
  80
  81 LxDmesg()