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scripts/gdb: update for lockless printk ringbuffer
With the introduction of the lockless printk ringbuffer, the data
structure for the kernel log buffer was changed. Update the gdb
scripts to be able to parse/print the new log buffer structure.
Fixes: 896fbe20b4 ("printk: use the lockless ringbuffer")
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reported-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Petr Mladek <pmladek@suse.com>
[akpm@linux-foundation.org: A typo fix.]
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200814212525.6118-3-john.ogness@linutronix.de
This commit is contained in:
John Ogness
Petr Mladek
parent
3e0d075cb0
commit
e60768311a
2 changed files with 208 additions and 82 deletions
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@ -16,8 +16,13 @@ import sys
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from linux import utils
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printk_log_type = utils.CachedType("struct printk_log")
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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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atomic_long_type = utils.CachedType("atomic_long_t")
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class LxDmesg(gdb.Command):
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"""Print Linux kernel log buffer."""
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@ -26,44 +31,102 @@ class LxDmesg(gdb.Command):
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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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log_buf_addr = int(str(gdb.parse_and_eval(
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"(void *)'printk.c'::log_buf")).split()[0], 16)
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log_first_idx = int(gdb.parse_and_eval("'printk.c'::log_first_idx"))
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log_next_idx = int(gdb.parse_and_eval("'printk.c'::log_next_idx"))
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log_buf_len = int(gdb.parse_and_eval("'printk.c'::log_buf_len"))
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inf = gdb.inferiors()[0]
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start = log_buf_addr + log_first_idx
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if log_first_idx < log_next_idx:
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log_buf_2nd_half = -1
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length = log_next_idx - log_first_idx
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log_buf = utils.read_memoryview(inf, start, length).tobytes()
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else:
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log_buf_2nd_half = log_buf_len - log_first_idx
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a = utils.read_memoryview(inf, start, log_buf_2nd_half)
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b = utils.read_memoryview(inf, log_buf_addr, log_next_idx)
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log_buf = a.tobytes() + b.tobytes()
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length_offset = printk_log_type.get_type()['len'].bitpos // 8
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text_len_offset = printk_log_type.get_type()['text_len'].bitpos // 8
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time_stamp_offset = printk_log_type.get_type()['ts_nsec'].bitpos // 8
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text_offset = printk_log_type.get_type().sizeof
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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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pos = 0
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while pos < log_buf.__len__():
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length = utils.read_u16(log_buf, pos + length_offset)
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if length == 0:
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if log_buf_2nd_half == -1:
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gdb.write("Corrupted log buffer!\n")
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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 array
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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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addr = utils.read_ulong(desc_ring, off)
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descs = utils.read_memoryview(inf, addr, desc_sz * desc_ring_count).tobytes()
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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
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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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addr = utils.read_ulong(text_data_ring, off)
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text_data = utils.read_memoryview(inf, addr, text_data_sz).tobytes()
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counter_off = atomic_long_type.get_type()['counter'].bitpos // 8
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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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off = prb_desc_type.get_type()['info'].bitpos // 8
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ts_off = off + printk_info_type.get_type()['ts_nsec'].bitpos // 8
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len_off = 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_sv_bits = utils.get_long_type().sizeof * 8
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desc_committed_mask = 1 << (desc_sv_bits - 1)
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desc_reuse_mask = 1 << (desc_sv_bits - 2)
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desc_flags_mask = desc_committed_mask | desc_reuse_mask
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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_u64(desc_ring, off + counter_off)
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off = prb_desc_ring_type.get_type()['head_id'].bitpos // 8
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head_id = utils.read_u64(desc_ring, off + counter_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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# skip non-committed record
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state = utils.read_u64(descs, desc_off + sv_off + counter_off) & desc_flags_mask
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if state != desc_committed_mask:
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if did == head_id:
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break
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pos = log_buf_2nd_half
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did = (did + 1) & desc_id_mask
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continue
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text_len = utils.read_u16(log_buf, pos + text_len_offset)
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text_start = pos + text_offset
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text = log_buf[text_start:text_start + text_len].decode(
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encoding='utf8', errors='replace')
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time_stamp = utils.read_u64(log_buf, pos + time_stamp_offset)
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begin = utils.read_ulong(descs, desc_off + begin_off) % text_data_sz
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end = utils.read_ulong(descs, desc_off + next_off) % text_data_sz
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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(descs, desc_off + 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 = text_data[text_start:text_start + text_len].decode(
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encoding='utf8', errors='replace')
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time_stamp = utils.read_u64(descs, desc_off + 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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@ -75,7 +138,9 @@ class LxDmesg(gdb.Command):
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msg = msg.encode(encoding='utf8', errors='replace')
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gdb.write(msg)
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pos += length
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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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