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e3c8d33e0d
The type atomic_long_t can have size 4 or 8 bytes, depending on
CONFIG_64BIT; it's only content, the field 'counter', is either an
int or a s64 value.
Current code incorrectly uses the fixed size utils.read_u64() to
read the field 'counter' inside atomic_long_t.
On 32 bits architectures reading the last element 'tail_id' of the
struct prb_desc_ring:
struct prb_desc_ring {
...
atomic_long_t tail_id;
};
causes the utils.read_u64() to access outside the boundary of the
struct and the gdb command 'lx-dmesg' exits with error:
Python Exception <class 'IndexError'>: index out of range
Error occurred in Python: index out of range
Query the really used atomic_long_t counter type size.
Link: https://lore.kernel.org/r/20220617143758.137307-1-antonio.borneo@foss.st.com
Fixes: e60768311a ("scripts/gdb: update for lockless printk ringbuffer")
Signed-off-by: Antonio Borneo <antonio.borneo@foss.st.com>
[pmladek@suse.com: Query the really used atomic_long_t counter type size]
Tested-by: Antonio Borneo <antonio.borneo@foss.st.com>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20220719122831.19890-1-pmladek@suse.com
152 lines
5.7 KiB
Python
152 lines
5.7 KiB
Python
#
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# gdb helper commands and functions for Linux kernel debugging
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#
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# kernel log buffer dump
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#
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# Copyright (c) Siemens AG, 2011, 2012
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#
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# Authors:
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# Jan Kiszka <jan.kiszka@siemens.com>
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#
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# This work is licensed under the terms of the GNU GPL version 2.
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#
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import gdb
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import sys
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from linux import utils
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printk_info_type = utils.CachedType("struct printk_info")
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prb_data_blk_lpos_type = utils.CachedType("struct prb_data_blk_lpos")
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prb_desc_type = utils.CachedType("struct prb_desc")
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prb_desc_ring_type = utils.CachedType("struct prb_desc_ring")
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prb_data_ring_type = utils.CachedType("struct prb_data_ring")
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printk_ringbuffer_type = utils.CachedType("struct printk_ringbuffer")
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class LxDmesg(gdb.Command):
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"""Print Linux kernel log buffer."""
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def __init__(self):
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super(LxDmesg, self).__init__("lx-dmesg", gdb.COMMAND_DATA)
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def invoke(self, arg, from_tty):
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inf = gdb.inferiors()[0]
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# read in prb structure
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prb_addr = int(str(gdb.parse_and_eval("(void *)'printk.c'::prb")).split()[0], 16)
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sz = printk_ringbuffer_type.get_type().sizeof
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prb = utils.read_memoryview(inf, prb_addr, sz).tobytes()
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# read in descriptor ring structure
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off = printk_ringbuffer_type.get_type()['desc_ring'].bitpos // 8
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addr = prb_addr + off
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sz = prb_desc_ring_type.get_type().sizeof
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desc_ring = utils.read_memoryview(inf, addr, sz).tobytes()
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# read in descriptor count, size, and address
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off = prb_desc_ring_type.get_type()['count_bits'].bitpos // 8
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desc_ring_count = 1 << utils.read_u32(desc_ring, off)
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desc_sz = prb_desc_type.get_type().sizeof
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off = prb_desc_ring_type.get_type()['descs'].bitpos // 8
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desc_addr = utils.read_ulong(desc_ring, off)
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# read in info size and address
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info_sz = printk_info_type.get_type().sizeof
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off = prb_desc_ring_type.get_type()['infos'].bitpos // 8
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info_addr = utils.read_ulong(desc_ring, off)
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# read in text data ring structure
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off = printk_ringbuffer_type.get_type()['text_data_ring'].bitpos // 8
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addr = prb_addr + off
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sz = prb_data_ring_type.get_type().sizeof
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text_data_ring = utils.read_memoryview(inf, addr, sz).tobytes()
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# read in text data size and address
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off = prb_data_ring_type.get_type()['size_bits'].bitpos // 8
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text_data_sz = 1 << utils.read_u32(text_data_ring, off)
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off = prb_data_ring_type.get_type()['data'].bitpos // 8
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text_data_addr = utils.read_ulong(text_data_ring, off)
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sv_off = prb_desc_type.get_type()['state_var'].bitpos // 8
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off = prb_desc_type.get_type()['text_blk_lpos'].bitpos // 8
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begin_off = off + (prb_data_blk_lpos_type.get_type()['begin'].bitpos // 8)
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next_off = off + (prb_data_blk_lpos_type.get_type()['next'].bitpos // 8)
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ts_off = printk_info_type.get_type()['ts_nsec'].bitpos // 8
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len_off = printk_info_type.get_type()['text_len'].bitpos // 8
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# definitions from kernel/printk/printk_ringbuffer.h
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desc_committed = 1
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desc_finalized = 2
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desc_sv_bits = utils.get_long_type().sizeof * 8
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desc_flags_shift = desc_sv_bits - 2
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desc_flags_mask = 3 << desc_flags_shift
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desc_id_mask = ~desc_flags_mask
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# read in tail and head descriptor ids
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off = prb_desc_ring_type.get_type()['tail_id'].bitpos // 8
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tail_id = utils.read_atomic_long(desc_ring, off)
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off = prb_desc_ring_type.get_type()['head_id'].bitpos // 8
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head_id = utils.read_atomic_long(desc_ring, off)
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did = tail_id
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while True:
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ind = did % desc_ring_count
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desc_off = desc_sz * ind
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info_off = info_sz * ind
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desc = utils.read_memoryview(inf, desc_addr + desc_off, desc_sz).tobytes()
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# skip non-committed record
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state = 3 & (utils.read_atomic_long(desc, sv_off) >> desc_flags_shift)
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if state != desc_committed and state != desc_finalized:
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if did == head_id:
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break
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did = (did + 1) & desc_id_mask
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continue
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begin = utils.read_ulong(desc, begin_off) % text_data_sz
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end = utils.read_ulong(desc, next_off) % text_data_sz
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info = utils.read_memoryview(inf, info_addr + info_off, info_sz).tobytes()
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# handle data-less record
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if begin & 1 == 1:
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text = ""
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else:
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# handle wrapping data block
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if begin > end:
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begin = 0
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# skip over descriptor id
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text_start = begin + utils.get_long_type().sizeof
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text_len = utils.read_u16(info, len_off)
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# handle truncated message
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if end - text_start < text_len:
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text_len = end - text_start
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text_data = utils.read_memoryview(inf, text_data_addr + text_start,
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text_len).tobytes()
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text = text_data[0:text_len].decode(encoding='utf8', errors='replace')
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time_stamp = utils.read_u64(info, ts_off)
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for line in text.splitlines():
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msg = u"[{time:12.6f}] {line}\n".format(
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time=time_stamp / 1000000000.0,
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line=line)
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# With python2 gdb.write will attempt to convert unicode to
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# ascii and might fail so pass an utf8-encoded str instead.
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if sys.hexversion < 0x03000000:
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msg = msg.encode(encoding='utf8', errors='replace')
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gdb.write(msg)
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if did == head_id:
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break
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did = (did + 1) & desc_id_mask
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LxDmesg()
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