dmesg.py (5967B)
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 14import gdb 15import sys 16 17from linux import utils 18 19printk_info_type = utils.CachedType("struct printk_info") 20prb_data_blk_lpos_type = utils.CachedType("struct prb_data_blk_lpos") 21prb_desc_type = utils.CachedType("struct prb_desc") 22prb_desc_ring_type = utils.CachedType("struct prb_desc_ring") 23prb_data_ring_type = utils.CachedType("struct prb_data_ring") 24printk_ringbuffer_type = utils.CachedType("struct printk_ringbuffer") 25atomic_long_type = utils.CachedType("atomic_long_t") 26 27class LxDmesg(gdb.Command): 28 """Print Linux kernel log buffer.""" 29 30 def __init__(self): 31 super(LxDmesg, self).__init__("lx-dmesg", gdb.COMMAND_DATA) 32 33 def invoke(self, arg, from_tty): 34 inf = gdb.inferiors()[0] 35 36 # read in prb structure 37 prb_addr = int(str(gdb.parse_and_eval("(void *)'printk.c'::prb")).split()[0], 16) 38 sz = printk_ringbuffer_type.get_type().sizeof 39 prb = utils.read_memoryview(inf, prb_addr, sz).tobytes() 40 41 # read in descriptor ring structure 42 off = printk_ringbuffer_type.get_type()['desc_ring'].bitpos // 8 43 addr = prb_addr + off 44 sz = prb_desc_ring_type.get_type().sizeof 45 desc_ring = utils.read_memoryview(inf, addr, sz).tobytes() 46 47 # read in descriptor count, size, and address 48 off = prb_desc_ring_type.get_type()['count_bits'].bitpos // 8 49 desc_ring_count = 1 << utils.read_u32(desc_ring, off) 50 desc_sz = prb_desc_type.get_type().sizeof 51 off = prb_desc_ring_type.get_type()['descs'].bitpos // 8 52 desc_addr = utils.read_ulong(desc_ring, off) 53 54 # read in info size and address 55 info_sz = printk_info_type.get_type().sizeof 56 off = prb_desc_ring_type.get_type()['infos'].bitpos // 8 57 info_addr = utils.read_ulong(desc_ring, off) 58 59 # read in text data ring structure 60 off = printk_ringbuffer_type.get_type()['text_data_ring'].bitpos // 8 61 addr = prb_addr + off 62 sz = prb_data_ring_type.get_type().sizeof 63 text_data_ring = utils.read_memoryview(inf, addr, sz).tobytes() 64 65 # read in text data size and address 66 off = prb_data_ring_type.get_type()['size_bits'].bitpos // 8 67 text_data_sz = 1 << utils.read_u32(text_data_ring, off) 68 off = prb_data_ring_type.get_type()['data'].bitpos // 8 69 text_data_addr = utils.read_ulong(text_data_ring, off) 70 71 counter_off = atomic_long_type.get_type()['counter'].bitpos // 8 72 73 sv_off = prb_desc_type.get_type()['state_var'].bitpos // 8 74 75 off = prb_desc_type.get_type()['text_blk_lpos'].bitpos // 8 76 begin_off = off + (prb_data_blk_lpos_type.get_type()['begin'].bitpos // 8) 77 next_off = off + (prb_data_blk_lpos_type.get_type()['next'].bitpos // 8) 78 79 ts_off = printk_info_type.get_type()['ts_nsec'].bitpos // 8 80 len_off = printk_info_type.get_type()['text_len'].bitpos // 8 81 82 # definitions from kernel/printk/printk_ringbuffer.h 83 desc_committed = 1 84 desc_finalized = 2 85 desc_sv_bits = utils.get_long_type().sizeof * 8 86 desc_flags_shift = desc_sv_bits - 2 87 desc_flags_mask = 3 << desc_flags_shift 88 desc_id_mask = ~desc_flags_mask 89 90 # read in tail and head descriptor ids 91 off = prb_desc_ring_type.get_type()['tail_id'].bitpos // 8 92 tail_id = utils.read_u64(desc_ring, off + counter_off) 93 off = prb_desc_ring_type.get_type()['head_id'].bitpos // 8 94 head_id = utils.read_u64(desc_ring, off + counter_off) 95 96 did = tail_id 97 while True: 98 ind = did % desc_ring_count 99 desc_off = desc_sz * ind 100 info_off = info_sz * ind 101 102 desc = utils.read_memoryview(inf, desc_addr + desc_off, desc_sz).tobytes() 103 104 # skip non-committed record 105 state = 3 & (utils.read_u64(desc, sv_off + counter_off) >> desc_flags_shift) 106 if state != desc_committed and state != desc_finalized: 107 if did == head_id: 108 break 109 did = (did + 1) & desc_id_mask 110 continue 111 112 begin = utils.read_ulong(desc, begin_off) % text_data_sz 113 end = utils.read_ulong(desc, next_off) % text_data_sz 114 115 info = utils.read_memoryview(inf, info_addr + info_off, info_sz).tobytes() 116 117 # handle data-less record 118 if begin & 1 == 1: 119 text = "" 120 else: 121 # handle wrapping data block 122 if begin > end: 123 begin = 0 124 125 # skip over descriptor id 126 text_start = begin + utils.get_long_type().sizeof 127 128 text_len = utils.read_u16(info, len_off) 129 130 # handle truncated message 131 if end - text_start < text_len: 132 text_len = end - text_start 133 134 text_data = utils.read_memoryview(inf, text_data_addr + text_start, 135 text_len).tobytes() 136 text = text_data[0:text_len].decode(encoding='utf8', errors='replace') 137 138 time_stamp = utils.read_u64(info, ts_off) 139 140 for line in text.splitlines(): 141 msg = u"[{time:12.6f}] {line}\n".format( 142 time=time_stamp / 1000000000.0, 143 line=line) 144 # With python2 gdb.write will attempt to convert unicode to 145 # ascii and might fail so pass an utf8-encoded str instead. 146 if sys.hexversion < 0x03000000: 147 msg = msg.encode(encoding='utf8', errors='replace') 148 gdb.write(msg) 149 150 if did == head_id: 151 break 152 did = (did + 1) & desc_id_mask 153 154 155LxDmesg()