linux-kernel - [PATCH 06/13] scripts/gdb: Add lx-dmesg command

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Date:	Mon,  5 Nov 2012 17:08:59 +0100
From:	Jan Kiszka <jan.kiszka@...mens.com>
To:	linux-kernel@...r.kernel.org
Cc:	Jason Wessel <jason.wessel@...driver.com>,
	kgdb-bugreport@...ts.sourceforge.net,
	Andi Kleen <andi@...stfloor.org>, Kay Sievers <kay@...y.org>
Subject: [PATCH 06/13] scripts/gdb: Add lx-dmesg command

This pokes into the log buffer of the debugged kernel, dumping it to the
gdb console. Helping in case the target should or can no longer execute
dmesg itself.

CC: Kay Sievers <kay@...y.org>
Signed-off-by: Jan Kiszka <jan.kiszka@...mens.com>
---
 scripts/gdb/dmesg.py       |   63 ++++++++++++++++++++++++++++++++++++++++++++
 scripts/gdb/vmlinux-gdb.py |    1 +
 2 files changed, 64 insertions(+), 0 deletions(-)
 create mode 100644 scripts/gdb/dmesg.py

diff --git a/scripts/gdb/dmesg.py b/scripts/gdb/dmesg.py
new file mode 100644
index 0000000..2f475bc
--- /dev/null
+++ b/scripts/gdb/dmesg.py
@@ -0,0 +1,63 @@
+#
+# gdb helper commands and functions for Linux kernel debugging
+#
+#  kernel log buffer dump
+#
+# Copyright (c) 2011, 2012 Siemens AG
+#
+# Authors:
+#  Jan Kiszka <jan.kiszka@...mens.com>
+#
+# This work is licensed under the terms of the GNU GPL version 2.
+#
+
+import gdb
+import string
+
+from utils import *
+
+class LinuxDmesg(gdb.Command):
+	__doc__ = "Print Linux kernel log buffer."
+
+	def __init__(self):
+		super(LinuxDmesg, self).__init__("lx-dmesg", gdb.COMMAND_DATA)
+
+	def invoke(self, arg, from_tty):
+		log_buf_addr = int(str(gdb.parse_and_eval("(void *)log_buf")),
+				   16)
+		log_first_idx = int(gdb.parse_and_eval("log_first_idx"))
+		log_next_idx = int(gdb.parse_and_eval("log_next_idx"))
+		log_buf_len = int(gdb.parse_and_eval("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 = inf.read_memory(start, length)
+		else:
+			log_buf_2nd_half = log_buf_len - log_first_idx
+			log_buf = inf.read_memory(start, log_buf_2nd_half) + \
+				  inf.read_memory(log_buf_addr, log_next_idx)
+
+		pos = 0
+		while pos < log_buf.__len__():
+			length = read_u16(log_buf[pos + 8 : pos + 10])
+			if length == 0:
+				if log_buf_2nd_half == -1:
+					print "Corrupted log buffer!"
+					break
+				pos = log_buf_2nd_half
+				continue
+
+			text_len = read_u16(log_buf[pos + 10 : pos + 12])
+			time_stamp = read_u64(log_buf[pos : pos + 8])
+
+			for line in log_buf[pos + 16 :
+					    pos + 16 + text_len].splitlines():
+				print "[%13.6f] " % \
+				      (time_stamp / 1000000000.0) + line
+
+			pos += length
+
+LinuxDmesg()
diff --git a/scripts/gdb/vmlinux-gdb.py b/scripts/gdb/vmlinux-gdb.py
index fa1d5e1..8b0422e 100644
--- a/scripts/gdb/vmlinux-gdb.py
+++ b/scripts/gdb/vmlinux-gdb.py
@@ -21,3 +21,4 @@ if not gdb.VERSION >= "7.1":
 else:
 	import utils
 	import symbols
+	import dmesg
-- 
1.7.3.4

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