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
  20 class LxDmesg(gdb.Command):
  21     """Print Linux kernel log buffer."""
  22
  23     def __init__(self):
  24         super(LxDmesg, self).__init__("lx-dmesg", gdb.COMMAND_DATA)
  25
  26     def invoke(self, arg, from_tty):
  27         log_buf_addr = int(str(gdb.parse_and_eval(
  28             "(void *)'printk.c'::log_buf")).split()[0], 16)
  29         log_first_idx = int(gdb.parse_and_eval("'printk.c'::log_first_idx"))
  30         log_next_idx = int(gdb.parse_and_eval("'printk.c'::log_next_idx"))
  31         log_buf_len = int(gdb.parse_and_eval("'printk.c'::log_buf_len"))
  32
  33         inf = gdb.inferiors()[0]
  34         start = log_buf_addr + log_first_idx
  35         if log_first_idx < log_next_idx:
  36             log_buf_2nd_half = -1
  37             length = log_next_idx - log_first_idx
  38             log_buf = utils.read_memoryview(inf, start, length).tobytes()
  39         else:
  40             log_buf_2nd_half = log_buf_len - log_first_idx
  41             a = utils.read_memoryview(inf, start, log_buf_2nd_half)
  42             b = utils.read_memoryview(inf, log_buf_addr, log_next_idx)
  43             log_buf = a.tobytes() + b.tobytes()
  44
  45         pos = 0
  46         while pos < log_buf.__len__():
  47             length = utils.read_u16(log_buf[pos + 8:pos + 10])
  48             if length == 0:
  49                 if log_buf_2nd_half == -1:
  50                     gdb.write("Corrupted log buffer!\n")
  51                     break
  52                 pos = log_buf_2nd_half
  53                 continue
  54
  55             text_len = utils.read_u16(log_buf[pos + 10:pos + 12])
  56             text = log_buf[pos + 16:pos + 16 + text_len].decode(
  57                 encoding='utf8', errors='replace')
  58             time_stamp = utils.read_u64(log_buf[pos:pos + 8])
  59
  60             for line in text.splitlines():
  61                 msg = u"[{time:12.6f}] {line}\n".format(
  62                     time=time_stamp / 1000000000.0,
  63                     line=line)
  64                 # With python2 gdb.write will attempt to convert unicode to
  65                 # ascii and might fail so pass an utf8-encoded str instead.
  66                 if sys.hexversion < 0x03000000:
  67                     msg = msg.encode(encoding='utf8', errors='replace')
  68                 gdb.write(msg)
  69
  70             pos += length
  71
  72
  73 LxDmesg()