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") 25 26class 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 152LxDmesg() 153