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
  16 from linux import utils
  17
  18
  19 class LxDmesg(gdb.Command):
  20     """Print Linux kernel log buffer."""
  21
  22     def __init__(self):
  23         super(LxDmesg, self).__init__("lx-dmesg", gdb.COMMAND_DATA)
  24
  25     def invoke(self, arg, from_tty):
  26         log_buf_addr = int(str(gdb.parse_and_eval(
  27             "'printk.c'::log_buf")).split()[0], 16)
  28         log_first_idx = int(gdb.parse_and_eval("'printk.c'::log_first_idx"))
  29         log_next_idx = int(gdb.parse_and_eval("'printk.c'::log_next_idx"))
  30         log_buf_len = int(gdb.parse_and_eval("'printk.c'::log_buf_len"))
  31
  32         inf = gdb.inferiors()[0]
  33         start = log_buf_addr + log_first_idx
  34         if log_first_idx < log_next_idx:
  35             log_buf_2nd_half = -1
  36             length = log_next_idx - log_first_idx
  37             log_buf = utils.read_memoryview(inf, start, length).tobytes()
  38         else:
  39             log_buf_2nd_half = log_buf_len - log_first_idx
  40             a = utils.read_memoryview(inf, start, log_buf_2nd_half)
  41             b = utils.read_memoryview(inf, log_buf_addr, log_next_idx)
  42             log_buf = a.tobytes() + b.tobytes()
  43
  44         pos = 0
  45         while pos < log_buf.__len__():
  46             length = utils.read_u16(log_buf[pos + 8:pos + 10])
  47             if length == 0:
  48                 if log_buf_2nd_half == -1:
  49                     gdb.write("Corrupted log buffer!\n")
  50                     break
  51                 pos = log_buf_2nd_half
  52                 continue
  53
  54             text_len = utils.read_u16(log_buf[pos + 10:pos + 12])
  55             text = log_buf[pos + 16:pos + 16 + text_len].decode()
  56             time_stamp = utils.read_u64(log_buf[pos:pos + 8])
  57
  58             for line in text.splitlines():
  59                 gdb.write("[{time:12.6f}] {line}\n".format(
  60                     time=time_stamp / 1000000000.0,
  61                     line=line))
  62
  63             pos += length
  64
  65
  66 LxDmesg()