lkml.org 
[lkml]   [2019]   [Oct]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v2] scripts/gdb: fix lx-dmesg when CONFIG_PRINTK_CALLER is set
Date
When CONFIG_PRINTK_CALLER is set, struct printk_log contains an
additional member caller_id. This affects the offset of the log text.
Account for this by using the type information from gdb to determine all
the offsets instead of using hardcoded values.

This fixes following error:

(gdb) lx-dmesg
Python Exception <class 'ValueError'> embedded null character:
Error occurred in Python command: embedded null character

Signed-off-by: Joel Colledge <joel.colledge@linbit.com>
---
Changes in v2:
- use type information from gdb instead of hardcoded offsets

Thanks for the idea about using the struct layout info from gdb, Leonard. I can't see any reason we shouldn't use that here, since most of the other commands use it. LxDmesg has used hardcoded offsets since scripts/gdb was introduced, so I assume it just ended up like that during the initial development of the tool. Here is a version of the fix using offsets from gdb.

scripts/gdb/linux/dmesg.py | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/scripts/gdb/linux/dmesg.py b/scripts/gdb/linux/dmesg.py
index 6d2e09a2ad2f..8f5d899029b7 100644
--- a/scripts/gdb/linux/dmesg.py
+++ b/scripts/gdb/linux/dmesg.py
@@ -16,6 +16,8 @@ import sys

from linux import utils

+printk_log_type = utils.CachedType("struct printk_log")
+

class LxDmesg(gdb.Command):
"""Print Linux kernel log buffer."""
@@ -42,9 +44,14 @@ class LxDmesg(gdb.Command):
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 + 8:pos + 10])
+ length = utils.read_u16(log_buf[pos + length_offset:pos + length_offset + 2])
if length == 0:
if log_buf_2nd_half == -1:
gdb.write("Corrupted log buffer!\n")
@@ -52,10 +59,11 @@ class LxDmesg(gdb.Command):
pos = log_buf_2nd_half
continue

- text_len = utils.read_u16(log_buf[pos + 10:pos + 12])
- text = log_buf[pos + 16:pos + 16 + text_len].decode(
+ text_len = utils.read_u16(log_buf[pos + text_len_offset:pos + text_len_offset + 2])
+ text = log_buf[pos + text_offset:pos + text_offset + text_len].decode(
encoding='utf8', errors='replace')
- time_stamp = utils.read_u64(log_buf[pos:pos + 8])
+ time_stamp = utils.read_u64(
+ log_buf[pos + time_stamp_offset:pos + time_stamp_offset + 8])

for line in text.splitlines():
msg = u"[{time:12.6f}] {line}\n".format(
--
2.17.1
\
 
 \ /
  Last update: 2019-10-11 14:26    [W:0.096 / U:0.020 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site