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Linus Torvalds1da177e2005-04-16 15:20:36 -07001S390 Debug Feature
2==================
3
4files: arch/s390/kernel/debug.c
Randy Dunlap58cc8552009-01-06 14:42:42 -08005 arch/s390/include/asm/debug.h
Linus Torvalds1da177e2005-04-16 15:20:36 -07006
7Description:
8------------
9The goal of this feature is to provide a kernel debug logging API
10where log records can be stored efficiently in memory, where each component
11(e.g. device drivers) can have one separate debug log.
12One purpose of this is to inspect the debug logs after a production system crash
13in order to analyze the reason for the crash.
Matt LaPlantea2ffd272006-10-03 22:49:15 +020014If the system still runs but only a subcomponent which uses dbf fails,
Michael Holzheu66a464d2005-06-25 14:55:33 -070015it is possible to look at the debug logs on a live system via the Linux
16debugfs filesystem.
Linus Torvalds1da177e2005-04-16 15:20:36 -070017The debug feature may also very useful for kernel and driver development.
18
19Design:
20-------
21Kernel components (e.g. device drivers) can register themselves at the debug
22feature with the function call debug_register(). This function initializes a
23debug log for the caller. For each debug log exists a number of debug areas
24where exactly one is active at one time. Each debug area consists of contiguous
25pages in memory. In the debug areas there are stored debug entries (log records)
26which are written by event- and exception-calls.
27
28An event-call writes the specified debug entry to the active debug
29area and updates the log pointer for the active area. If the end
30of the active debug area is reached, a wrap around is done (ring buffer)
31and the next debug entry will be written at the beginning of the active
32debug area.
33
34An exception-call writes the specified debug entry to the log and
35switches to the next debug area. This is done in order to be sure
36that the records which describe the origin of the exception are not
37overwritten when a wrap around for the current area occurs.
38
Nicolas Kaiser2254f5a2006-12-04 15:40:23 +010039The debug areas themselves are also ordered in form of a ring buffer.
Linus Torvalds1da177e2005-04-16 15:20:36 -070040When an exception is thrown in the last debug area, the following debug
41entries are then written again in the very first area.
42
43There are three versions for the event- and exception-calls: One for
44logging raw data, one for text and one for numbers.
45
46Each debug entry contains the following data:
47
48- Timestamp
49- Cpu-Number of calling task
50- Level of debug entry (0...6)
51- Return Address to caller
52- Flag, if entry is an exception or not
53
54The debug logs can be inspected in a live system through entries in
Michael Holzheu66a464d2005-06-25 14:55:33 -070055the debugfs-filesystem. Under the toplevel directory "s390dbf" there is
Linus Torvalds1da177e2005-04-16 15:20:36 -070056a directory for each registered component, which is named like the
Michael Holzheu66a464d2005-06-25 14:55:33 -070057corresponding component. The debugfs normally should be mounted to
Nicolas Kaiser2254f5a2006-12-04 15:40:23 +010058/sys/kernel/debug therefore the debug feature can be accessed under
Michael Holzheu66a464d2005-06-25 14:55:33 -070059/sys/kernel/debug/s390dbf.
Linus Torvalds1da177e2005-04-16 15:20:36 -070060
61The content of the directories are files which represent different views
62to the debug log. Each component can decide which views should be
63used through registering them with the function debug_register_view().
64Predefined views for hex/ascii, sprintf and raw binary data are provided.
65It is also possible to define other views. The content of
Michael Holzheu66a464d2005-06-25 14:55:33 -070066a view can be inspected simply by reading the corresponding debugfs file.
Linus Torvalds1da177e2005-04-16 15:20:36 -070067
Paolo Ornati670e9f32006-10-03 22:57:56 +020068All debug logs have an actual debug level (range from 0 to 6).
Linus Torvalds1da177e2005-04-16 15:20:36 -070069The default level is 3. Event and Exception functions have a 'level'
70parameter. Only debug entries with a level that is lower or equal
71than the actual level are written to the log. This means, when
72writing events, high priority log entries should have a low level
73value whereas low priority entries should have a high one.
Michael Holzheu66a464d2005-06-25 14:55:33 -070074The actual debug level can be changed with the help of the debugfs-filesystem
75through writing a number string "x" to the 'level' debugfs file which is
Linus Torvalds1da177e2005-04-16 15:20:36 -070076provided for every debug log. Debugging can be switched off completely
Michael Holzheu66a464d2005-06-25 14:55:33 -070077by using "-" on the 'level' debugfs file.
Linus Torvalds1da177e2005-04-16 15:20:36 -070078
79Example:
80
Michael Holzheu66a464d2005-06-25 14:55:33 -070081> echo "-" > /sys/kernel/debug/s390dbf/dasd/level
Linus Torvalds1da177e2005-04-16 15:20:36 -070082
83It is also possible to deactivate the debug feature globally for every
84debug log. You can change the behavior using 2 sysctl parameters in
85/proc/sys/s390dbf:
Matt LaPlante992caac2006-10-03 22:52:05 +020086There are currently 2 possible triggers, which stop the debug feature
87globally. The first possibility is to use the "debug_active" sysctl. If
Linus Torvalds1da177e2005-04-16 15:20:36 -070088set to 1 the debug feature is running. If "debug_active" is set to 0 the
89debug feature is turned off.
Nicolas Kaiser2254f5a2006-12-04 15:40:23 +010090The second trigger which stops the debug feature is a kernel oops.
Linus Torvalds1da177e2005-04-16 15:20:36 -070091That prevents the debug feature from overwriting debug information that
92happened before the oops. After an oops you can reactivate the debug feature
93by piping 1 to /proc/sys/s390dbf/debug_active. Nevertheless, its not
Nicolas Kaiser2254f5a2006-12-04 15:40:23 +010094suggested to use an oopsed kernel in a production environment.
Linus Torvalds1da177e2005-04-16 15:20:36 -070095If you want to disallow the deactivation of the debug feature, you can use
96the "debug_stoppable" sysctl. If you set "debug_stoppable" to 0 the debug
97feature cannot be stopped. If the debug feature is already stopped, it
98will stay deactivated.
99
100Kernel Interfaces:
101------------------
102
103----------------------------------------------------------------------------
Michael Holzheu66a464d2005-06-25 14:55:33 -0700104debug_info_t *debug_register(char *name, int pages, int nr_areas,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700105 int buf_size);
106
Michael Holzheu66a464d2005-06-25 14:55:33 -0700107Parameter: name: Name of debug log (e.g. used for debugfs entry)
108 pages: number of pages, which will be allocated per area
Linus Torvalds1da177e2005-04-16 15:20:36 -0700109 nr_areas: number of debug areas
110 buf_size: size of data area in each debug entry
111
112Return Value: Handle for generated debug area
113 NULL if register failed
114
115Description: Allocates memory for a debug log
116 Must not be called within an interrupt handler
117
Michael Holzheu9637c3f2008-04-17 07:46:18 +0200118----------------------------------------------------------------------------
119debug_info_t *debug_register_mode(char *name, int pages, int nr_areas,
120 int buf_size, mode_t mode, uid_t uid,
121 gid_t gid);
122
123Parameter: name: Name of debug log (e.g. used for debugfs entry)
124 pages: Number of pages, which will be allocated per area
125 nr_areas: Number of debug areas
126 buf_size: Size of data area in each debug entry
127 mode: File mode for debugfs files. E.g. S_IRWXUGO
128 uid: User ID for debugfs files. Currently only 0 is
129 supported.
130 gid: Group ID for debugfs files. Currently only 0 is
131 supported.
132
133Return Value: Handle for generated debug area
134 NULL if register failed
135
136Description: Allocates memory for a debug log
137 Must not be called within an interrupt handler
138
Linus Torvalds1da177e2005-04-16 15:20:36 -0700139---------------------------------------------------------------------------
140void debug_unregister (debug_info_t * id);
141
142Parameter: id: handle for debug log
143
144Return Value: none
145
Michael Holzheu98ae9b02013-03-06 11:06:57 +0100146Description: frees memory for a debug log and removes all registered debug
147 views.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700148 Must not be called within an interrupt handler
149
150---------------------------------------------------------------------------
151void debug_set_level (debug_info_t * id, int new_level);
152
153Parameter: id: handle for debug log
154 new_level: new debug level
155
156Return Value: none
157
158Description: Sets new actual debug level if new_level is valid.
159
160---------------------------------------------------------------------------
Hendrik Bruecknerf1d86b62013-09-18 17:21:34 +0200161bool debug_level_enabled (debug_info_t * id, int level);
162
163Parameter: id: handle for debug log
164 level: debug level
165
166Return Value: True if level is less or equal to the current debug level.
167
168Description: Returns true if debug events for the specified level would be
169 logged. Otherwise returns false.
170---------------------------------------------------------------------------
Michael Holzheu66a464d2005-06-25 14:55:33 -0700171void debug_stop_all(void);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700172
173Parameter: none
174
175Return Value: none
176
177Description: stops the debug feature if stopping is allowed. Currently
178 used in case of a kernel oops.
179
180---------------------------------------------------------------------------
181debug_entry_t* debug_event (debug_info_t* id, int level, void* data,
182 int length);
183
184Parameter: id: handle for debug log
185 level: debug level
186 data: pointer to data for debug entry
187 length: length of data in bytes
188
189Return Value: Address of written debug entry
190
191Description: writes debug entry to active debug area (if level <= actual
192 debug level)
193
194---------------------------------------------------------------------------
195debug_entry_t* debug_int_event (debug_info_t * id, int level,
196 unsigned int data);
197debug_entry_t* debug_long_event(debug_info_t * id, int level,
198 unsigned long data);
199
200Parameter: id: handle for debug log
201 level: debug level
202 data: integer value for debug entry
203
204Return Value: Address of written debug entry
205
206Description: writes debug entry to active debug area (if level <= actual
207 debug level)
208
209---------------------------------------------------------------------------
210debug_entry_t* debug_text_event (debug_info_t * id, int level,
211 const char* data);
212
213Parameter: id: handle for debug log
214 level: debug level
215 data: string for debug entry
216
217Return Value: Address of written debug entry
218
219Description: writes debug entry in ascii format to active debug area
220 (if level <= actual debug level)
221
222---------------------------------------------------------------------------
223debug_entry_t* debug_sprintf_event (debug_info_t * id, int level,
224 char* string,...);
225
226Parameter: id: handle for debug log
227 level: debug level
228 string: format string for debug entry
229 ...: varargs used as in sprintf()
230
231Return Value: Address of written debug entry
232
233Description: writes debug entry with format string and varargs (longs) to
234 active debug area (if level $<=$ actual debug level).
235 floats and long long datatypes cannot be used as varargs.
236
237---------------------------------------------------------------------------
238
239debug_entry_t* debug_exception (debug_info_t* id, int level, void* data,
240 int length);
241
242Parameter: id: handle for debug log
243 level: debug level
244 data: pointer to data for debug entry
245 length: length of data in bytes
246
247Return Value: Address of written debug entry
248
249Description: writes debug entry to active debug area (if level <= actual
250 debug level) and switches to next debug area
251
252---------------------------------------------------------------------------
253debug_entry_t* debug_int_exception (debug_info_t * id, int level,
254 unsigned int data);
255debug_entry_t* debug_long_exception(debug_info_t * id, int level,
256 unsigned long data);
257
258Parameter: id: handle for debug log
259 level: debug level
260 data: integer value for debug entry
261
262Return Value: Address of written debug entry
263
264Description: writes debug entry to active debug area (if level <= actual
265 debug level) and switches to next debug area
266
267---------------------------------------------------------------------------
268debug_entry_t* debug_text_exception (debug_info_t * id, int level,
269 const char* data);
270
271Parameter: id: handle for debug log
272 level: debug level
273 data: string for debug entry
274
275Return Value: Address of written debug entry
276
277Description: writes debug entry in ascii format to active debug area
278 (if level <= actual debug level) and switches to next debug
279 area
280
281---------------------------------------------------------------------------
282debug_entry_t* debug_sprintf_exception (debug_info_t * id, int level,
283 char* string,...);
284
285Parameter: id: handle for debug log
286 level: debug level
287 string: format string for debug entry
288 ...: varargs used as in sprintf()
289
290Return Value: Address of written debug entry
291
292Description: writes debug entry with format string and varargs (longs) to
293 active debug area (if level $<=$ actual debug level) and
294 switches to next debug area.
295 floats and long long datatypes cannot be used as varargs.
296
297---------------------------------------------------------------------------
298
299int debug_register_view (debug_info_t * id, struct debug_view *view);
300
301Parameter: id: handle for debug log
302 view: pointer to debug view struct
303
304Return Value: 0 : ok
305 < 0: Error
306
Michael Holzheu66a464d2005-06-25 14:55:33 -0700307Description: registers new debug view and creates debugfs dir entry
Linus Torvalds1da177e2005-04-16 15:20:36 -0700308
309---------------------------------------------------------------------------
310int debug_unregister_view (debug_info_t * id, struct debug_view *view);
311
312Parameter: id: handle for debug log
313 view: pointer to debug view struct
314
315Return Value: 0 : ok
316 < 0: Error
317
Michael Holzheu66a464d2005-06-25 14:55:33 -0700318Description: unregisters debug view and removes debugfs dir entry
Linus Torvalds1da177e2005-04-16 15:20:36 -0700319
320
321
322Predefined views:
323-----------------
324
325extern struct debug_view debug_hex_ascii_view;
326extern struct debug_view debug_raw_view;
327extern struct debug_view debug_sprintf_view;
328
329Examples
330--------
331
332/*
333 * hex_ascii- + raw-view Example
334 */
335
336#include <linux/init.h>
337#include <asm/debug.h>
338
339static debug_info_t* debug_info;
340
341static int init(void)
342{
343 /* register 4 debug areas with one page each and 4 byte data field */
344
Michael Holzheu66a464d2005-06-25 14:55:33 -0700345 debug_info = debug_register ("test", 1, 4, 4 );
Linus Torvalds1da177e2005-04-16 15:20:36 -0700346 debug_register_view(debug_info,&debug_hex_ascii_view);
347 debug_register_view(debug_info,&debug_raw_view);
348
349 debug_text_event(debug_info, 4 , "one ");
350 debug_int_exception(debug_info, 4, 4711);
351 debug_event(debug_info, 3, &debug_info, 4);
352
353 return 0;
354}
355
356static void cleanup(void)
357{
358 debug_unregister (debug_info);
359}
360
361module_init(init);
362module_exit(cleanup);
363
364---------------------------------------------------------------------------
365
366/*
367 * sprintf-view Example
368 */
369
370#include <linux/init.h>
371#include <asm/debug.h>
372
373static debug_info_t* debug_info;
374
375static int init(void)
376{
377 /* register 4 debug areas with one page each and data field for */
378 /* format string pointer + 2 varargs (= 3 * sizeof(long)) */
379
Michael Holzheu66a464d2005-06-25 14:55:33 -0700380 debug_info = debug_register ("test", 1, 4, sizeof(long) * 3);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700381 debug_register_view(debug_info,&debug_sprintf_view);
382
383 debug_sprintf_event(debug_info, 2 , "first event in %s:%i\n",__FILE__,__LINE__);
384 debug_sprintf_exception(debug_info, 1, "pointer to debug info: %p\n",&debug_info);
385
386 return 0;
387}
388
389static void cleanup(void)
390{
391 debug_unregister (debug_info);
392}
393
394module_init(init);
395module_exit(cleanup);
396
397
398
Michael Holzheu66a464d2005-06-25 14:55:33 -0700399Debugfs Interface
Linus Torvalds1da177e2005-04-16 15:20:36 -0700400----------------
401Views to the debug logs can be investigated through reading the corresponding
Michael Holzheu66a464d2005-06-25 14:55:33 -0700402debugfs-files:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700403
404Example:
405
Michael Holzheu66a464d2005-06-25 14:55:33 -0700406> ls /sys/kernel/debug/s390dbf/dasd
407flush hex_ascii level pages raw
408> cat /sys/kernel/debug/s390dbf/dasd/hex_ascii | sort +1
Linus Torvalds1da177e2005-04-16 15:20:36 -070040900 00974733272:680099 2 - 02 0006ad7e 07 ea 4a 90 | ....
41000 00974733272:682210 2 - 02 0006ade6 46 52 45 45 | FREE
41100 00974733272:682213 2 - 02 0006adf6 07 ea 4a 90 | ....
41200 00974733272:682281 1 * 02 0006ab08 41 4c 4c 43 | EXCP
41301 00974733272:682284 2 - 02 0006ab16 45 43 4b 44 | ECKD
41401 00974733272:682287 2 - 02 0006ab28 00 00 00 04 | ....
41501 00974733272:682289 2 - 02 0006ab3e 00 00 00 20 | ...
41601 00974733272:682297 2 - 02 0006ad7e 07 ea 4a 90 | ....
41701 00974733272:684384 2 - 00 0006ade6 46 52 45 45 | FREE
41801 00974733272:684388 2 - 00 0006adf6 07 ea 4a 90 | ....
419
420See section about predefined views for explanation of the above output!
421
422Changing the debug level
423------------------------
424
425Example:
426
427
Michael Holzheu66a464d2005-06-25 14:55:33 -0700428> cat /sys/kernel/debug/s390dbf/dasd/level
Linus Torvalds1da177e2005-04-16 15:20:36 -07004293
Michael Holzheu66a464d2005-06-25 14:55:33 -0700430> echo "5" > /sys/kernel/debug/s390dbf/dasd/level
431> cat /sys/kernel/debug/s390dbf/dasd/level
Linus Torvalds1da177e2005-04-16 15:20:36 -07004325
433
434Flushing debug areas
435--------------------
436Debug areas can be flushed with piping the number of the desired
Michael Holzheu66a464d2005-06-25 14:55:33 -0700437area (0...n) to the debugfs file "flush". When using "-" all debug areas
Linus Torvalds1da177e2005-04-16 15:20:36 -0700438are flushed.
439
440Examples:
441
4421. Flush debug area 0:
Michael Holzheu66a464d2005-06-25 14:55:33 -0700443> echo "0" > /sys/kernel/debug/s390dbf/dasd/flush
Linus Torvalds1da177e2005-04-16 15:20:36 -0700444
4452. Flush all debug areas:
Michael Holzheu66a464d2005-06-25 14:55:33 -0700446> echo "-" > /sys/kernel/debug/s390dbf/dasd/flush
447
448Changing the size of debug areas
449------------------------------------
450It is possible the change the size of debug areas through piping
451the number of pages to the debugfs file "pages". The resize request will
452also flush the debug areas.
453
454Example:
455
456Define 4 pages for the debug areas of debug feature "dasd":
457> echo "4" > /sys/kernel/debug/s390dbf/dasd/pages
Linus Torvalds1da177e2005-04-16 15:20:36 -0700458
459Stooping the debug feature
460--------------------------
461Example:
462
4631. Check if stopping is allowed
464> cat /proc/sys/s390dbf/debug_stoppable
4652. Stop debug feature
466> echo 0 > /proc/sys/s390dbf/debug_active
467
468lcrash Interface
469----------------
470It is planned that the dump analysis tool lcrash gets an additional command
471's390dbf' to display all the debug logs. With this tool it will be possible
472to investigate the debug logs on a live system and with a memory dump after
473a system crash.
474
475Investigating raw memory
476------------------------
477One last possibility to investigate the debug logs at a live
478system and after a system crash is to look at the raw memory
479under VM or at the Service Element.
480It is possible to find the anker of the debug-logs through
481the 'debug_area_first' symbol in the System map. Then one has
482to follow the correct pointers of the data-structures defined
483in debug.h and find the debug-areas in memory.
484Normally modules which use the debug feature will also have
485a global variable with the pointer to the debug-logs. Following
486this pointer it will also be possible to find the debug logs in
487memory.
488
489For this method it is recommended to use '16 * x + 4' byte (x = 0..n)
490for the length of the data field in debug_register() in
491order to see the debug entries well formatted.
492
493
494Predefined Views
495----------------
496
497There are three predefined views: hex_ascii, raw and sprintf.
498The hex_ascii view shows the data field in hex and ascii representation
499(e.g. '45 43 4b 44 | ECKD').
500The raw view returns a bytestream as the debug areas are stored in memory.
501
502The sprintf view formats the debug entries in the same way as the sprintf
Matt LaPlantefff92892006-10-03 22:47:42 +0200503function would do. The sprintf event/exception functions write to the
Linus Torvalds1da177e2005-04-16 15:20:36 -0700504debug entry a pointer to the format string (size = sizeof(long))
505and for each vararg a long value. So e.g. for a debug entry with a format
506string plus two varargs one would need to allocate a (3 * sizeof(long))
507byte data area in the debug_register() function.
508
Michael Holzheuf64d04c2009-09-11 10:28:59 +0200509IMPORTANT: Using "%s" in sprintf event functions is dangerous. You can only
510use "%s" in the sprintf event functions, if the memory for the passed string is
511available as long as the debug feature exists. The reason behind this is that
512due to performance considerations only a pointer to the string is stored in
513the debug feature. If you log a string that is freed afterwards, you will get
514an OOPS when inspecting the debug feature, because then the debug feature will
515access the already freed memory.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700516
517NOTE: If using the sprintf view do NOT use other event/exception functions
518than the sprintf-event and -exception functions.
519
520The format of the hex_ascii and sprintf view is as follows:
521- Number of area
522- Timestamp (formatted as seconds and microseconds since 00:00:00 Coordinated
523 Universal Time (UTC), January 1, 1970)
524- level of debug entry
525- Exception flag (* = Exception)
526- Cpu-Number of calling task
527- Return Address to caller
528- data field
529
530The format of the raw view is:
531- Header as described in debug.h
532- datafield
533
534A typical line of the hex_ascii view will look like the following (first line
535is only for explanation and will not be displayed when 'cating' the view):
536
537area time level exception cpu caller data (hex + ascii)
538--------------------------------------------------------------------------
53900 00964419409:440690 1 - 00 88023fe
540
541
542Defining views
543--------------
544
545Views are specified with the 'debug_view' structure. There are defined
Michael Holzheu66a464d2005-06-25 14:55:33 -0700546callback functions which are used for reading and writing the debugfs files:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700547
548struct debug_view {
549 char name[DEBUG_MAX_PROCF_LEN];
550 debug_prolog_proc_t* prolog_proc;
551 debug_header_proc_t* header_proc;
552 debug_format_proc_t* format_proc;
553 debug_input_proc_t* input_proc;
554 void* private_data;
555};
556
557where
558
559typedef int (debug_header_proc_t) (debug_info_t* id,
560 struct debug_view* view,
561 int area,
562 debug_entry_t* entry,
563 char* out_buf);
564
565typedef int (debug_format_proc_t) (debug_info_t* id,
566 struct debug_view* view, char* out_buf,
567 const char* in_buf);
568typedef int (debug_prolog_proc_t) (debug_info_t* id,
569 struct debug_view* view,
570 char* out_buf);
571typedef int (debug_input_proc_t) (debug_info_t* id,
572 struct debug_view* view,
573 struct file* file, const char* user_buf,
574 size_t in_buf_size, loff_t* offset);
575
576
577The "private_data" member can be used as pointer to view specific data.
578It is not used by the debug feature itself.
579
Michael Holzheu66a464d2005-06-25 14:55:33 -0700580The output when reading a debugfs file is structured like this:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700581
582"prolog_proc output"
583
584"header_proc output 1" "format_proc output 1"
585"header_proc output 2" "format_proc output 2"
586"header_proc output 3" "format_proc output 3"
587...
588
Michael Holzheu66a464d2005-06-25 14:55:33 -0700589When a view is read from the debugfs, the Debug Feature calls the
Linus Torvalds1da177e2005-04-16 15:20:36 -0700590'prolog_proc' once for writing the prolog.
591Then 'header_proc' and 'format_proc' are called for each
592existing debug entry.
593
594The input_proc can be used to implement functionality when it is written to
Michael Holzheu66a464d2005-06-25 14:55:33 -0700595the view (e.g. like with 'echo "0" > /sys/kernel/debug/s390dbf/dasd/level).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700596
597For header_proc there can be used the default function
Paolo Ornati670e9f32006-10-03 22:57:56 +0200598debug_dflt_header_fn() which is defined in debug.h.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700599and which produces the same header output as the predefined views.
600E.g:
60100 00964419409:440761 2 - 00 88023ec
602
603In order to see how to use the callback functions check the implementation
604of the default views!
605
606Example
607
608#include <asm/debug.h>
609
610#define UNKNOWNSTR "data: %08x"
611
612const char* messages[] =
613{"This error...........\n",
614 "That error...........\n",
615 "Problem..............\n",
616 "Something went wrong.\n",
617 "Everything ok........\n",
618 NULL
619};
620
621static int debug_test_format_fn(
622 debug_info_t * id, struct debug_view *view,
623 char *out_buf, const char *in_buf
624)
625{
626 int i, rc = 0;
627
628 if(id->buf_size >= 4) {
629 int msg_nr = *((int*)in_buf);
630 if(msg_nr < sizeof(messages)/sizeof(char*) - 1)
631 rc += sprintf(out_buf, "%s", messages[msg_nr]);
632 else
633 rc += sprintf(out_buf, UNKNOWNSTR, msg_nr);
634 }
635 out:
636 return rc;
637}
638
639struct debug_view debug_test_view = {
640 "myview", /* name of view */
641 NULL, /* no prolog */
642 &debug_dflt_header_fn, /* default header for each entry */
643 &debug_test_format_fn, /* our own format function */
644 NULL, /* no input function */
645 NULL /* no private data */
646};
647
648=====
649test:
650=====
651debug_info_t *debug_info;
652...
653debug_info = debug_register ("test", 0, 4, 4 ));
654debug_register_view(debug_info, &debug_test_view);
655for(i = 0; i < 10; i ++) debug_int_event(debug_info, 1, i);
656
Michael Holzheu66a464d2005-06-25 14:55:33 -0700657> cat /sys/kernel/debug/s390dbf/test/myview
Linus Torvalds1da177e2005-04-16 15:20:36 -070065800 00964419734:611402 1 - 00 88042ca This error...........
65900 00964419734:611405 1 - 00 88042ca That error...........
66000 00964419734:611408 1 - 00 88042ca Problem..............
66100 00964419734:611411 1 - 00 88042ca Something went wrong.
66200 00964419734:611414 1 - 00 88042ca Everything ok........
66300 00964419734:611417 1 - 00 88042ca data: 00000005
66400 00964419734:611419 1 - 00 88042ca data: 00000006
66500 00964419734:611422 1 - 00 88042ca data: 00000007
66600 00964419734:611425 1 - 00 88042ca data: 00000008
66700 00964419734:611428 1 - 00 88042ca data: 00000009