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Commit e6076831 authored by John Ogness's avatar John Ogness Committed by Petr Mladek
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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: 896fbe20 ("printk: use the lockless ringbuffer")
Signed-off-by: default avatarJohn Ogness <john.ogness@linutronix.de>
Reported-by: default avatarNick Desaulniers <ndesaulniers@google.com>
Tested-by: default avatarNick Desaulniers <ndesaulniers@google.com>
Tested-by: default avatarPetr Mladek <pmladek@suse.com>
[akpm@linux-foundation.org: A typo fix.]
Signed-off-by: default avatarPetr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200814212525.6118-3-john.ogness@linutronix.de
parent 3e0d075c
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Showing with 209 additions and 83 deletions
Documentation/admin-guide/kdump/gdbmacros.txt
View file @ e6076831
......@@ -170,57 +170,111 @@ document trapinfo
address the kernel panicked.
end
define dump_log_idx
set $idx = $arg0
define dump_record
set var $desc = $arg0
if ($argc > 1)
set $prev_flags = $arg1
set var $prev_flags = $arg1
else
set $prev_flags = 0
set var $prev_flags = 0
end
set $msg = ((struct printk_log *) (log_buf + $idx))
set $prefix = 1
set $newline = 1
set $log = log_buf + $idx + sizeof(*$msg)
# prev & LOG_CONT && !(msg->flags & LOG_PREIX)
if (($prev_flags & 8) && !($msg->flags & 4))
set $prefix = 0
set var $info = &$desc->info
set var $prefix = 1
set var $newline = 1
set var $begin = $desc->text_blk_lpos.begin % (1U << prb->text_data_ring.size_bits)
set var $next = $desc->text_blk_lpos.next % (1U << prb->text_data_ring.size_bits)
# handle data-less record
if ($begin & 1)
set var $text_len = 0
set var $log = ""
else
# handle wrapping data block
if ($begin > $next)
set var $begin = 0
end
# skip over descriptor id
set var $begin = $begin + sizeof(long)
# handle truncated message
if ($next - $begin < $info->text_len)
set var $text_len = $next - $begin
else
set var $text_len = $info->text_len
end
set var $log = &prb->text_data_ring.data[$begin]
end
# prev & LOG_CONT && !(info->flags & LOG_PREIX)
if (($prev_flags & 8) && !($info->flags & 4))
set var $prefix = 0
end
# msg->flags & LOG_CONT
if ($msg->flags & 8)
# info->flags & LOG_CONT
if ($info->flags & 8)
# (prev & LOG_CONT && !(prev & LOG_NEWLINE))
if (($prev_flags & 8) && !($prev_flags & 2))
set $prefix = 0
set var $prefix = 0
end
# (!(msg->flags & LOG_NEWLINE))
if (!($msg->flags & 2))
set $newline = 0
# (!(info->flags & LOG_NEWLINE))
if (!($info->flags & 2))
set var $newline = 0
end
end
if ($prefix)
printf "[%5lu.%06lu] ", $msg->ts_nsec / 1000000000, $msg->ts_nsec % 1000000000
printf "[%5lu.%06lu] ", $info->ts_nsec / 1000000000, $info->ts_nsec % 1000000000
end
if ($msg->text_len != 0)
eval "printf \"%%%d.%ds\", $log", $msg->text_len, $msg->text_len
if ($text_len)
eval "printf \"%%%d.%ds\", $log", $text_len, $text_len
end
if ($newline)
printf "\n"
end
if ($msg->dict_len > 0)
set $dict = $log + $msg->text_len
set $idx = 0
set $line = 1
while ($idx < $msg->dict_len)
# handle dictionary data
set var $begin = $desc->dict_blk_lpos.begin % (1U << prb->dict_data_ring.size_bits)
set var $next = $desc->dict_blk_lpos.next % (1U << prb->dict_data_ring.size_bits)
# handle data-less record
if ($begin & 1)
set var $dict_len = 0
set var $dict = ""
else
# handle wrapping data block
if ($begin > $next)
set var $begin = 0
end
# skip over descriptor id
set var $begin = $begin + sizeof(long)
# handle truncated message
if ($next - $begin < $info->dict_len)
set var $dict_len = $next - $begin
else
set var $dict_len = $info->dict_len
end
set var $dict = &prb->dict_data_ring.data[$begin]
end
if ($dict_len > 0)
set var $idx = 0
set var $line = 1
while ($idx < $dict_len)
if ($line)
printf " "
set $line = 0
set var $line = 0
end
set $c = $dict[$idx]
set var $c = $dict[$idx]
if ($c == '\0')
printf "\n"
set $line = 1
set var $line = 1
else
if ($c < ' ' || $c >= 127 || $c == '\\')
printf "\\x%02x", $c
......@@ -228,33 +282,40 @@ define dump_log_idx
printf "%c", $c
end
end
set $idx = $idx + 1
set var $idx = $idx + 1
end
printf "\n"
end
end
document dump_log_idx
Dump a single log given its index in the log buffer. The first
parameter is the index into log_buf, the second is optional and
specified the previous log buffer's flags, used for properly
formatting continued lines.
document dump_record
Dump a single record. The first parameter is the descriptor
sequence number, the second is optional and specifies the
previous record's flags, used for properly formatting
continued lines.
end
define dmesg
set $i = log_first_idx
set $end_idx = log_first_idx
set $prev_flags = 0
set var $desc_committed = 1UL << ((sizeof(long) * 8) - 1)
set var $flags_mask = 3UL << ((sizeof(long) * 8) - 2)
set var $id_mask = ~$flags_mask
set var $desc_count = 1U << prb->desc_ring.count_bits
set var $prev_flags = 0
set var $id = prb->desc_ring.tail_id.counter
set var $end_id = prb->desc_ring.head_id.counter
while (1)
set $msg = ((struct printk_log *) (log_buf + $i))
if ($msg->len == 0)
set $i = 0
else
dump_log_idx $i $prev_flags
set $i = $i + $msg->len
set $prev_flags = $msg->flags
set var $desc = &prb->desc_ring.descs[$id % $desc_count]
# skip non-committed record
if (($desc->state_var.counter & $flags_mask) == $desc_committed)
dump_record $desc $prev_flags
set var $prev_flags = $desc->info.flags
end
if ($i == $end_idx)
set var $id = ($id + 1) & $id_mask
if ($id == $end_id)
loop_break
end
end
......
scripts/gdb/linux/dmesg.py
View file @ e6076831
......@@ -16,8 +16,13 @@ import sys
from linux import utils
printk_log_type = utils.CachedType("struct printk_log")
printk_info_type = utils.CachedType("struct printk_info")
prb_data_blk_lpos_type = utils.CachedType("struct prb_data_blk_lpos")
prb_desc_type = utils.CachedType("struct prb_desc")
prb_desc_ring_type = utils.CachedType("struct prb_desc_ring")
prb_data_ring_type = utils.CachedType("struct prb_data_ring")
printk_ringbuffer_type = utils.CachedType("struct printk_ringbuffer")
atomic_long_type = utils.CachedType("atomic_long_t")
class LxDmesg(gdb.Command):
"""Print Linux kernel log buffer."""
......@@ -26,44 +31,102 @@ class LxDmesg(gdb.Command):
super(LxDmesg, self).__init__("lx-dmesg", gdb.COMMAND_DATA)
def invoke(self, arg, from_tty):
log_buf_addr = int(str(gdb.parse_and_eval(
"(void *)'printk.c'::log_buf")).split()[0], 16)
log_first_idx = int(gdb.parse_and_eval("'printk.c'::log_first_idx"))
log_next_idx = int(gdb.parse_and_eval("'printk.c'::log_next_idx"))
log_buf_len = int(gdb.parse_and_eval("'printk.c'::log_buf_len"))
inf = gdb.inferiors()[0]
start = log_buf_addr + log_first_idx
if log_first_idx < log_next_idx:
log_buf_2nd_half = -1
length = log_next_idx - log_first_idx
log_buf = utils.read_memoryview(inf, start, length).tobytes()
else:
log_buf_2nd_half = log_buf_len - log_first_idx
a = utils.read_memoryview(inf, start, log_buf_2nd_half)
b = utils.read_memoryview(inf, log_buf_addr, log_next_idx)
log_buf = a.tobytes() + b.tobytes()
length_offset = printk_log_type.get_type()['len'].bitpos // 8
text_len_offset = printk_log_type.get_type()['text_len'].bitpos // 8
time_stamp_offset = printk_log_type.get_type()['ts_nsec'].bitpos // 8
text_offset = printk_log_type.get_type().sizeof
pos = 0
while pos < log_buf.__len__():
length = utils.read_u16(log_buf, pos + length_offset)
if length == 0:
if log_buf_2nd_half == -1:
gdb.write("Corrupted log buffer!\n")
# read in prb structure
prb_addr = int(str(gdb.parse_and_eval("(void *)'printk.c'::prb")).split()[0], 16)
sz = printk_ringbuffer_type.get_type().sizeof
prb = utils.read_memoryview(inf, prb_addr, sz).tobytes()
# read in descriptor ring structure
off = printk_ringbuffer_type.get_type()['desc_ring'].bitpos // 8
addr = prb_addr + off
sz = prb_desc_ring_type.get_type().sizeof
desc_ring = utils.read_memoryview(inf, addr, sz).tobytes()
# read in descriptor array
off = prb_desc_ring_type.get_type()['count_bits'].bitpos // 8
desc_ring_count = 1 << utils.read_u32(desc_ring, off)
desc_sz = prb_desc_type.get_type().sizeof
off = prb_desc_ring_type.get_type()['descs'].bitpos // 8
addr = utils.read_ulong(desc_ring, off)
descs = utils.read_memoryview(inf, addr, desc_sz * desc_ring_count).tobytes()
# read in text data ring structure
off = printk_ringbuffer_type.get_type()['text_data_ring'].bitpos // 8
addr = prb_addr + off
sz = prb_data_ring_type.get_type().sizeof
text_data_ring = utils.read_memoryview(inf, addr, sz).tobytes()
# read in text data
off = prb_data_ring_type.get_type()['size_bits'].bitpos // 8
text_data_sz = 1 << utils.read_u32(text_data_ring, off)
off = prb_data_ring_type.get_type()['data'].bitpos // 8
addr = utils.read_ulong(text_data_ring, off)
text_data = utils.read_memoryview(inf, addr, text_data_sz).tobytes()
counter_off = atomic_long_type.get_type()['counter'].bitpos // 8
sv_off = prb_desc_type.get_type()['state_var'].bitpos // 8
off = prb_desc_type.get_type()['text_blk_lpos'].bitpos // 8
begin_off = off + (prb_data_blk_lpos_type.get_type()['begin'].bitpos // 8)
next_off = off + (prb_data_blk_lpos_type.get_type()['next'].bitpos // 8)
off = prb_desc_type.get_type()['info'].bitpos // 8
ts_off = off + printk_info_type.get_type()['ts_nsec'].bitpos // 8
len_off = off + printk_info_type.get_type()['text_len'].bitpos // 8
# definitions from kernel/printk/printk_ringbuffer.h
desc_sv_bits = utils.get_long_type().sizeof * 8
desc_committed_mask = 1 << (desc_sv_bits - 1)
desc_reuse_mask = 1 << (desc_sv_bits - 2)
desc_flags_mask = desc_committed_mask | desc_reuse_mask
desc_id_mask = ~desc_flags_mask
# read in tail and head descriptor ids
off = prb_desc_ring_type.get_type()['tail_id'].bitpos // 8
tail_id = utils.read_u64(desc_ring, off + counter_off)
off = prb_desc_ring_type.get_type()['head_id'].bitpos // 8
head_id = utils.read_u64(desc_ring, off + counter_off)
did = tail_id
while True:
ind = did % desc_ring_count
desc_off = desc_sz * ind
# skip non-committed record
state = utils.read_u64(descs, desc_off + sv_off + counter_off) & desc_flags_mask
if state != desc_committed_mask:
if did == head_id:
break
pos = log_buf_2nd_half
did = (did + 1) & desc_id_mask
continue
text_len = utils.read_u16(log_buf, pos + text_len_offset)
text_start = pos + text_offset
text = log_buf[text_start:text_start + text_len].decode(
encoding='utf8', errors='replace')
time_stamp = utils.read_u64(log_buf, pos + time_stamp_offset)
begin = utils.read_ulong(descs, desc_off + begin_off) % text_data_sz
end = utils.read_ulong(descs, desc_off + next_off) % text_data_sz
# handle data-less record
if begin & 1 == 1:
text = ""
else:
# handle wrapping data block
if begin > end:
begin = 0
# skip over descriptor id
text_start = begin + utils.get_long_type().sizeof
text_len = utils.read_u16(descs, desc_off + len_off)
# handle truncated message
if end - text_start < text_len:
text_len = end - text_start
text = text_data[text_start:text_start + text_len].decode(
encoding='utf8', errors='replace')
time_stamp = utils.read_u64(descs, desc_off + ts_off)
for line in text.splitlines():
msg = u"[{time:12.6f}] {line}\n".format(
......@@ -75,7 +138,9 @@ class LxDmesg(gdb.Command):
msg = msg.encode(encoding='utf8', errors='replace')
gdb.write(msg)
pos += length
if did == head_id:
break
did = (did + 1) & desc_id_mask
LxDmesg()
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