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_info_type = utils.CachedType("struct printk_info")
20 prb_data_blk_lpos_type = utils.CachedType("struct prb_data_blk_lpos")
21 prb_desc_type = utils.CachedType("struct prb_desc")
22 prb_desc_ring_type = utils.CachedType("struct prb_desc_ring")
23 prb_data_ring_type = utils.CachedType("struct prb_data_ring")
24 printk_ringbuffer_type = utils.CachedType("struct printk_ringbuffer")
25
26 class LxDmesg(gdb.Command):
27 """Print Linux kernel log buffer."""
28
29 def __init__(self):
30 super(LxDmesg, self).__init__("lx-dmesg", gdb.COMMAND_DATA)
31
32 def invoke(self, arg, from_tty):
33 inf = gdb.inferiors()[0]
34
35 # read in prb structure
36 prb_addr = int(str(gdb.parse_and_eval("(void *)'printk.c'::prb")).split()[0], 16)
37 sz = printk_ringbuffer_type.get_type().sizeof
38 prb = utils.read_memoryview(inf, prb_addr, sz).tobytes()
39
40 # read in descriptor ring structure
41 off = printk_ringbuffer_type.get_type()['desc_ring'].bitpos // 8
42 addr = prb_addr + off
43 sz = prb_desc_ring_type.get_type().sizeof
44 desc_ring = utils.read_memoryview(inf, addr, sz).tobytes()
45
46 # read in descriptor count, size, and address
47 off = prb_desc_ring_type.get_type()['count_bits'].bitpos // 8
48 desc_ring_count = 1 << utils.read_u32(desc_ring, off)
49 desc_sz = prb_desc_type.get_type().sizeof
50 off = prb_desc_ring_type.get_type()['descs'].bitpos // 8
51 desc_addr = utils.read_ulong(desc_ring, off)
52
53 # read in info size and address
54 info_sz = printk_info_type.get_type().sizeof
55 off = prb_desc_ring_type.get_type()['infos'].bitpos // 8
56 info_addr = utils.read_ulong(desc_ring, off)
57
58 # read in text data ring structure
59 off = printk_ringbuffer_type.get_type()['text_data_ring'].bitpos // 8
60 addr = prb_addr + off
61 sz = prb_data_ring_type.get_type().sizeof
62 text_data_ring = utils.read_memoryview(inf, addr, sz).tobytes()
63
64 # read in text data size and address
65 off = prb_data_ring_type.get_type()['size_bits'].bitpos // 8
66 text_data_sz = 1 << utils.read_u32(text_data_ring, off)
67 off = prb_data_ring_type.get_type()['data'].bitpos // 8
68 text_data_addr = utils.read_ulong(text_data_ring, off)
69
70 sv_off = prb_desc_type.get_type()['state_var'].bitpos // 8
71
72 off = prb_desc_type.get_type()['text_blk_lpos'].bitpos // 8
73 begin_off = off + (prb_data_blk_lpos_type.get_type()['begin'].bitpos // 8)
74 next_off = off + (prb_data_blk_lpos_type.get_type()['next'].bitpos // 8)
75
76 ts_off = printk_info_type.get_type()['ts_nsec'].bitpos // 8
77 len_off = printk_info_type.get_type()['text_len'].bitpos // 8
78
79 # definitions from kernel/printk/printk_ringbuffer.h
80 desc_committed = 1
81 desc_finalized = 2
82 desc_sv_bits = utils.get_long_type().sizeof * 8
83 desc_flags_shift = desc_sv_bits - 2
84 desc_flags_mask = 3 << desc_flags_shift
85 desc_id_mask = ~desc_flags_mask
86
87 # read in tail and head descriptor ids
88 off = prb_desc_ring_type.get_type()['tail_id'].bitpos // 8
89 tail_id = utils.read_atomic_long(desc_ring, off)
90 off = prb_desc_ring_type.get_type()['head_id'].bitpos // 8
91 head_id = utils.read_atomic_long(desc_ring, off)
92
93 did = tail_id
94 while True:
95 ind = did % desc_ring_count
96 desc_off = desc_sz * ind
97 info_off = info_sz * ind
98
99 desc = utils.read_memoryview(inf, desc_addr + desc_off, desc_sz).tobytes()
100
101 # skip non-committed record
102 state = 3 & (utils.read_atomic_long(desc, sv_off) >> desc_flags_shift)
103 if state != desc_committed and state != desc_finalized:
104 if did == head_id:
105 break
106 did = (did + 1) & desc_id_mask
107 continue
108
109 begin = utils.read_ulong(desc, begin_off) % text_data_sz
110 end = utils.read_ulong(desc, next_off) % text_data_sz
111
112 info = utils.read_memoryview(inf, info_addr + info_off, info_sz).tobytes()
113
114 # handle data-less record
115 if begin & 1 == 1:
116 text = ""
117 else:
118 # handle wrapping data block
119 if begin > end:
120 begin = 0
121
122 # skip over descriptor id
123 text_start = begin + utils.get_long_type().sizeof
124
125 text_len = utils.read_u16(info, len_off)
126
127 # handle truncated message
128 if end - text_start < text_len:
129 text_len = end - text_start
130
131 text_data = utils.read_memoryview(inf, text_data_addr + text_start,
132 text_len).tobytes()
133 text = text_data[0:text_len].decode(encoding='utf8', errors='replace')
134
135 time_stamp = utils.read_u64(info, ts_off)
136
137 for line in text.splitlines():
138 msg = u"[{time:12.6f}] {line}\n".format(
139 time=time_stamp / 1000000000.0,
140 line=line)
141 # With python2 gdb.write will attempt to convert unicode to
142 # ascii and might fail so pass an utf8-encoded str instead.
143 if sys.hexversion < 0x03000000:
144 msg = msg.encode(encoding='utf8', errors='replace')
145 gdb.write(msg)
146
147 if did == head_id:
148 break
149 did = (did + 1) & desc_id_mask
150
151
152 LxDmesg()
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