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Date: Fri, 14 Aug 2020 23:31:25 +0206
From: John Ogness <john.ogness@...utronix.de>
To: Jan Kiszka <jan.kiszka@...mens.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Baoquan He <bhe@...hat.com>, Dave Young <dyoung@...hat.com>,
Vivek Goyal <vgoyal@...hat.com>,
Jonathan Corbet <corbet@....net>,
Kieran Bingham <kbingham@...nel.org>,
Petr Mladek <pmladek@...e.com>,
Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
Steven Rostedt <rostedt@...dmis.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Nick Desaulniers <ndesaulniers@...gle.com>,
linux-kernel@...r.kernel.org
Subject: [PATCH 2/2][next] 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: ("printk: use the lockless ringbuffer")
Signed-off-by: John Ogness <john.ogness@...utronix.de>
Reported-by: Nick Desaulniers <ndesaulniers@...gle.com>
---
based on next-20200814
Documentation/admin-guide/kdump/gdbmacros.txt | 153 ++++++++++++------
scripts/gdb/linux/dmesg.py | 139 +++++++++++-----
2 files changed, 209 insertions(+), 83 deletions(-)
diff --git a/Documentation/admin-guide/kdump/gdbmacros.txt b/Documentation/admin-guide/kdump/gdbmacros.txt
index 220d0a80ca2c..6025534c6c14 100644
--- a/Documentation/admin-guide/kdump/gdbmacros.txt
+++ b/Documentation/admin-guide/kdump/gdbmacros.txt
@@ -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 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
diff --git a/scripts/gdb/linux/dmesg.py b/scripts/gdb/linux/dmesg.py
index 2fa7bb83885f..6c6022012ea8 100644
--- a/scripts/gdb/linux/dmesg.py
+++ b/scripts/gdb/linux/dmesg.py
@@ -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()
--
2.20.1
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