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Documentation / kdump / gdbmacros.txt




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Based on kernel version 4.7.2. Page generated on 2016-08-22 22:46 EST.

1	#
2	# This file contains a few gdb macros (user defined commands) to extract
3	# useful information from kernel crashdump (kdump) like stack traces of
4	# all the processes or a particular process and trapinfo.
5	#
6	# These macros can be used by copying this file in .gdbinit (put in home
7	# directory or current directory) or by invoking gdb command with
8	# --command=<command-file-name> option
9	#
10	# Credits:
11	# Alexander Nyberg <alexn@telia.com>
12	# V Srivatsa <vatsa@in.ibm.com>
13	# Maneesh Soni <maneesh@in.ibm.com>
14	#
15	
16	define bttnobp
17		set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
18		set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
19		set $init_t=&init_task
20		set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
21		set var $stacksize = sizeof(union thread_union)
22		while ($next_t != $init_t)
23			set $next_t=(struct task_struct *)$next_t
24			printf "\npid %d; comm %s:\n", $next_t.pid, $next_t.comm
25			printf "===================\n"
26			set var $stackp = $next_t.thread.sp
27			set var $stack_top = ($stackp & ~($stacksize - 1)) + $stacksize
28	
29			while ($stackp < $stack_top)
30				if (*($stackp) > _stext && *($stackp) < _sinittext)
31					info symbol *($stackp)
32				end
33				set $stackp += 4
34			end
35			set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
36			while ($next_th != $next_t)
37				set $next_th=(struct task_struct *)$next_th
38				printf "\npid %d; comm %s:\n", $next_t.pid, $next_t.comm
39				printf "===================\n"
40				set var $stackp = $next_t.thread.sp
41				set var $stack_top = ($stackp & ~($stacksize - 1)) + stacksize
42	
43				while ($stackp < $stack_top)
44					if (*($stackp) > _stext && *($stackp) < _sinittext)
45						info symbol *($stackp)
46					end
47					set $stackp += 4
48				end
49				set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
50			end
51			set $next_t=(char *)($next_t->tasks.next) - $tasks_off
52		end
53	end
54	document bttnobp
55		dump all thread stack traces on a kernel compiled with !CONFIG_FRAME_POINTER
56	end
57	
58	define btthreadstack
59		set var $pid_task = $arg0
60	
61		printf "\npid %d; comm %s:\n", $pid_task.pid, $pid_task.comm
62		printf "task struct: "
63		print $pid_task
64		printf "===================\n"
65		set var $stackp = $pid_task.thread.sp
66		set var $stacksize = sizeof(union thread_union)
67		set var $stack_top = ($stackp & ~($stacksize - 1)) + $stacksize
68		set var $stack_bot = ($stackp & ~($stacksize - 1))
69	
70		set $stackp = *((unsigned long *) $stackp)
71		while (($stackp < $stack_top) && ($stackp > $stack_bot))
72			set var $addr = *(((unsigned long *) $stackp) + 1)
73			info symbol $addr
74			set $stackp = *((unsigned long *) $stackp)
75		end
76	end
77	document btthreadstack
78		 dump a thread stack using the given task structure pointer
79	end
80	
81	
82	define btt
83		set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
84		set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
85		set $init_t=&init_task
86		set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
87		while ($next_t != $init_t)
88			set $next_t=(struct task_struct *)$next_t
89			btthreadstack $next_t
90	
91			set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
92			while ($next_th != $next_t)
93				set $next_th=(struct task_struct *)$next_th
94				btthreadstack $next_th
95				set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
96			end
97			set $next_t=(char *)($next_t->tasks.next) - $tasks_off
98		end
99	end
100	document btt
101		dump all thread stack traces on a kernel compiled with CONFIG_FRAME_POINTER
102	end
103	
104	define btpid
105		set var $pid = $arg0
106		set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
107		set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
108		set $init_t=&init_task
109		set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
110		set var $pid_task = 0
111	
112		while ($next_t != $init_t)
113			set $next_t=(struct task_struct *)$next_t
114	
115			if ($next_t.pid == $pid)
116				set $pid_task = $next_t
117			end
118	
119			set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
120			while ($next_th != $next_t)
121				set $next_th=(struct task_struct *)$next_th
122				if ($next_th.pid == $pid)
123					set $pid_task = $next_th
124				end
125				set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
126			end
127			set $next_t=(char *)($next_t->tasks.next) - $tasks_off
128		end
129	
130		btthreadstack $pid_task
131	end
132	document btpid
133		backtrace of pid
134	end
135	
136	
137	define trapinfo
138		set var $pid = $arg0
139		set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
140		set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
141		set $init_t=&init_task
142		set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
143		set var $pid_task = 0
144	
145		while ($next_t != $init_t)
146			set $next_t=(struct task_struct *)$next_t
147	
148			if ($next_t.pid == $pid)
149				set $pid_task = $next_t
150			end
151	
152			set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
153			while ($next_th != $next_t)
154				set $next_th=(struct task_struct *)$next_th
155				if ($next_th.pid == $pid)
156					set $pid_task = $next_th
157				end
158				set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
159			end
160			set $next_t=(char *)($next_t->tasks.next) - $tasks_off
161		end
162	
163		printf "Trapno %ld, cr2 0x%lx, error_code %ld\n", $pid_task.thread.trap_no, \
164					$pid_task.thread.cr2, $pid_task.thread.error_code
165	
166	end
167	document trapinfo
168		Run info threads and lookup pid of thread #1
169		'trapinfo <pid>' will tell you by which trap & possibly
170		address the kernel panicked.
171	end
172	
173	define dump_log_idx
174		set $idx = $arg0
175		if ($argc > 1)
176			set $prev_flags = $arg1
177		else
178			set $prev_flags = 0
179		end
180		set $msg = ((struct printk_log *) (log_buf + $idx))
181		set $prefix = 1
182		set $newline = 1
183		set $log = log_buf + $idx + sizeof(*$msg)
184	
185		# prev & LOG_CONT && !(msg->flags & LOG_PREIX)
186		if (($prev_flags & 8) && !($msg->flags & 4))
187			set $prefix = 0
188		end
189	
190		# msg->flags & LOG_CONT
191		if ($msg->flags & 8)
192			# (prev & LOG_CONT && !(prev & LOG_NEWLINE))
193			if (($prev_flags & 8) && !($prev_flags & 2))
194				set $prefix = 0
195			end
196			# (!(msg->flags & LOG_NEWLINE))
197			if (!($msg->flags & 2))
198				set $newline = 0
199			end
200		end
201	
202		if ($prefix)
203			printf "[%5lu.%06lu] ", $msg->ts_nsec / 1000000000, $msg->ts_nsec % 1000000000
204		end
205		if ($msg->text_len != 0)
206			eval "printf \"%%%d.%ds\", $log", $msg->text_len, $msg->text_len
207		end
208		if ($newline)
209			printf "\n"
210		end
211		if ($msg->dict_len > 0)
212			set $dict = $log + $msg->text_len
213			set $idx = 0
214			set $line = 1
215			while ($idx < $msg->dict_len)
216				if ($line)
217					printf " "
218					set $line = 0
219				end
220				set $c = $dict[$idx]
221				if ($c == '\0')
222					printf "\n"
223					set $line = 1
224				else
225					if ($c < ' ' || $c >= 127 || $c == '\\')
226						printf "\\x%02x", $c
227					else
228						printf "%c", $c
229					end
230				end
231				set $idx = $idx + 1
232			end
233			printf "\n"
234		end
235	end
236	document dump_log_idx
237		Dump a single log given its index in the log buffer.  The first
238		parameter is the index into log_buf, the second is optional and
239		specified the previous log buffer's flags, used for properly
240		formatting continued lines.
241	end
242	
243	define dmesg
244		set $i = log_first_idx
245		set $end_idx = log_first_idx
246		set $prev_flags = 0
247	
248		while (1)
249			set $msg = ((struct printk_log *) (log_buf + $i))
250			if ($msg->len == 0)
251				set $i = 0
252			else
253				dump_log_idx $i $prev_flags
254				set $i = $i + $msg->len
255				set $prev_flags = $msg->flags
256			end
257			if ($i == $end_idx)
258				loop_break
259			end
260		end
261	end
262	document dmesg
263		print the kernel ring buffer
264	end
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