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 <[email protected]> 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 array 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 addr = utils.read_ulong(desc_ring, off) 53 descs = utils.read_memoryview(inf, addr, desc_sz * desc_ring_count).tobytes() 54 55 # read in text data ring structure 56 off = printk_ringbuffer_type.get_type()['text_data_ring'].bitpos // 8 57 addr = prb_addr + off 58 sz = prb_data_ring_type.get_type().sizeof 59 text_data_ring = utils.read_memoryview(inf, addr, sz).tobytes() 60 61 # read in text data 62 off = prb_data_ring_type.get_type()['size_bits'].bitpos // 8 63 text_data_sz = 1 << utils.read_u32(text_data_ring, off) 64 off = prb_data_ring_type.get_type()['data'].bitpos // 8 65 addr = utils.read_ulong(text_data_ring, off) 66 text_data = utils.read_memoryview(inf, addr, text_data_sz).tobytes() 67 68 counter_off = atomic_long_type.get_type()['counter'].bitpos // 8 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 off = prb_desc_type.get_type()['info'].bitpos // 8 77 ts_off = off + printk_info_type.get_type()['ts_nsec'].bitpos // 8 78 len_off = off + printk_info_type.get_type()['text_len'].bitpos // 8 79 80 # definitions from kernel/printk/printk_ringbuffer.h 81 desc_committed = 1 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_u64(desc_ring, off + counter_off) 90 off = prb_desc_ring_type.get_type()['head_id'].bitpos // 8 91 head_id = utils.read_u64(desc_ring, off + counter_off) 92 93 did = tail_id 94 while True: 95 ind = did % desc_ring_count 96 desc_off = desc_sz * ind 97 98 # skip non-committed record 99 state = 3 & (utils.read_u64(descs, desc_off + sv_off + 100 counter_off) >> desc_flags_shift) 101 if state != desc_committed: 102 if did == head_id: 103 break 104 did = (did + 1) & desc_id_mask 105 continue 106 107 begin = utils.read_ulong(descs, desc_off + begin_off) % text_data_sz 108 end = utils.read_ulong(descs, desc_off + next_off) % text_data_sz 109 110 # handle data-less record 111 if begin & 1 == 1: 112 text = "" 113 else: 114 # handle wrapping data block 115 if begin > end: 116 begin = 0 117 118 # skip over descriptor id 119 text_start = begin + utils.get_long_type().sizeof 120 121 text_len = utils.read_u16(descs, desc_off + len_off) 122 123 # handle truncated message 124 if end - text_start < text_len: 125 text_len = end - text_start 126 127 text = text_data[text_start:text_start + text_len].decode( 128 encoding='utf8', errors='replace') 129 130 time_stamp = utils.read_u64(descs, desc_off + ts_off) 131 132 for line in text.splitlines(): 133 msg = u"[{time:12.6f}] {line}\n".format( 134 time=time_stamp / 1000000000.0, 135 line=line) 136 # With python2 gdb.write will attempt to convert unicode to 137 # ascii and might fail so pass an utf8-encoded str instead. 138 if sys.hexversion < 0x03000000: 139 msg = msg.encode(encoding='utf8', errors='replace') 140 gdb.write(msg) 141 142 if did == head_id: 143 break 144 did = (did + 1) & desc_id_mask 145 146 147LxDmesg() 148