[PATCH] s390: debug feature changes

One purpose of this is to inspect the debug logs after a production system crash

in order to analyze the reason for the crash.

If the system still runs but only a subcomponent which uses dbf failes,

it is possible to look at the debug logs on a live system via the Linux proc

filesystem.

it is possible to look at the debug logs on a live system via the Linux

debugfs filesystem.

The debug feature may also very useful for kernel and driver development.

Design:

- Flag, if entry is an exception or not

The debug logs can be inspected in a live system through entries in

the proc-filesystem. Under the path /proc/s390dbf there is 

the debugfs-filesystem. Under the toplevel directory "s390dbf" there is

a directory for each registered component, which is named like the

corresponding component.

corresponding component. The debugfs normally should be mounted to

/sys/kernel/debug therefore the debug feature can be accessed unter

/sys/kernel/debug/s390dbf.

The content of the directories are files which represent different views

to the debug log. Each component can decide which views should be

used through registering them with the function debug_register_view().

Predefined views for hex/ascii, sprintf and raw binary data are provided.

It is also possible to define other views. The content of

a view can be inspected simply by reading the corresponding proc file.

a view can be inspected simply by reading the corresponding debugfs file.

All debug logs have an an actual debug level (range from 0 to 6).

The default level is 3. Event and Exception functions have a 'level'

than the actual level are written to the log. This means, when

writing events, high priority log entries should have a low level

value whereas low priority entries should have a high one.

The actual debug level can be changed with the help of the proc-filesystem 

through writing a number string "x" to the 'level' proc file which is

The actual debug level can be changed with the help of the debugfs-filesystem

through writing a number string "x" to the 'level' debugfs file which is

provided for every debug log. Debugging can be switched off completely

by using "-" on the 'level' proc file.

by using "-" on the 'level' debugfs file.

Example:

> echo "-" > /proc/s390dbf/dasd/level

> echo "-" > /sys/kernel/debug/s390dbf/dasd/level

It is also possible to deactivate the debug feature globally for every

debug log. You can change the behavior using  2 sysctl parameters in

------------------

----------------------------------------------------------------------------

debug_info_t *debug_register(char *name, int pages_index, int nr_areas,

debug_info_t *debug_register(char *name, int pages, int nr_areas,

                             int buf_size);

Parameter:    name:        Name of debug log (e.g. used for proc entry) 

              pages_index: 2^pages_index pages will be allocated per area

Parameter:    name:        Name of debug log (e.g. used for debugfs entry)

              pages:       number of pages, which will be allocated per area

              nr_areas:    number of debug areas

              buf_size:    size of data area in each debug entry

Description:   Sets new actual debug level if new_level is valid. 

---------------------------------------------------------------------------

+void debug_stop_all(void);

void debug_stop_all(void);

Parameter:     none

Return Value:  0  : ok 

               < 0: Error 

Description:   registers new debug view and creates proc dir entry 

Description:   registers new debug view and creates debugfs dir entry

---------------------------------------------------------------------------

int debug_unregister_view (debug_info_t * id, struct debug_view *view); 

Return Value:  0  : ok 

               < 0: Error 

Description:   unregisters debug view and removes proc dir entry 

Description:   unregisters debug view and removes debugfs dir entry

{

    /* register 4 debug areas with one page each and 4 byte data field */

    debug_info = debug_register ("test", 0, 4, 4 );

    debug_info = debug_register ("test", 1, 4, 4 );

    debug_register_view(debug_info,&debug_hex_ascii_view);

    debug_register_view(debug_info,&debug_raw_view);

    /* register 4 debug areas with one page each and data field for */

    /* format string pointer + 2 varargs (= 3 * sizeof(long))       */

    debug_info = debug_register ("test", 0, 4, sizeof(long) * 3);

    debug_info = debug_register ("test", 1, 4, sizeof(long) * 3);

    debug_register_view(debug_info,&debug_sprintf_view);

    debug_sprintf_event(debug_info, 2 , "first event in %s:%i\n",__FILE__,__LINE__);

ProcFS Interface

Debugfs Interface

----------------

Views to the debug logs can be investigated through reading the corresponding 

proc-files:

debugfs-files:

Example:

> ls /proc/s390dbf/dasd

flush  hex_ascii  level      raw 

> cat /proc/s390dbf/dasd/hex_ascii | sort +1

> ls /sys/kernel/debug/s390dbf/dasd

flush  hex_ascii  level pages raw

> cat /sys/kernel/debug/s390dbf/dasd/hex_ascii | sort +1

00 00974733272:680099 2 - 02 0006ad7e  07 ea 4a 90 | ....

00 00974733272:682210 2 - 02 0006ade6  46 52 45 45 | FREE

00 00974733272:682213 2 - 02 0006adf6  07 ea 4a 90 | ....

Example:

> cat /proc/s390dbf/dasd/level

> cat /sys/kernel/debug/s390dbf/dasd/level

3

> echo "5" > /proc/s390dbf/dasd/level

> cat /proc/s390dbf/dasd/level

> echo "5" > /sys/kernel/debug/s390dbf/dasd/level

> cat /sys/kernel/debug/s390dbf/dasd/level

5

Flushing debug areas

--------------------

Debug areas can be flushed with piping the number of the desired

area (0...n) to the proc file "flush". When using "-" all debug areas

area (0...n) to the debugfs file "flush". When using "-" all debug areas

are flushed.

Examples:

1. Flush debug area 0:

> echo "0" > /proc/s390dbf/dasd/flush  

> echo "0" > /sys/kernel/debug/s390dbf/dasd/flush

2. Flush all debug areas:

> echo "-" > /proc/s390dbf/dasd/flush

> echo "-" > /sys/kernel/debug/s390dbf/dasd/flush

Changing the size of debug areas

------------------------------------

It is possible the change the size of debug areas through piping

the number of pages to the debugfs file "pages". The resize request will

also flush the debug areas.

Example:

Define 4 pages for the debug areas of debug feature "dasd":

> echo "4" > /sys/kernel/debug/s390dbf/dasd/pages

Stooping the debug feature

--------------------------

--------------

Views are specified with the 'debug_view' structure. There are defined

callback functions which are used for reading and writing the proc files:

callback functions which are used for reading and writing the debugfs files:

struct debug_view {

        char name[DEBUG_MAX_PROCF_LEN];  

The "private_data" member can be used as pointer to view specific data.

It is not used by the debug feature itself.

The output when reading a debug-proc file is structured like this:

The output when reading a debugfs file is structured like this:

"prolog_proc output"

"header_proc output 3"  "format_proc output 3"

...

When a view is read from the proc fs, the Debug Feature calls the 

When a view is read from the debugfs, the Debug Feature calls the

'prolog_proc' once for writing the prolog.

Then 'header_proc' and 'format_proc' are called for each 

existing debug entry.

The input_proc can be used to implement functionality when it is written to 

the view (e.g. like with 'echo "0" > /proc/s390dbf/dasd/level).

the view (e.g. like with 'echo "0" > /sys/kernel/debug/s390dbf/dasd/level).

For header_proc there can be used the default function

debug_dflt_header_fn() which is defined in in debug.h.

debug_register_view(debug_info, &debug_test_view);

for(i = 0; i < 10; i ++) debug_int_event(debug_info, 1, i);

> cat /proc/s390dbf/test/myview

> cat /sys/kernel/debug/s390dbf/test/myview

00 00964419734:611402 1 - 00 88042ca   This error...........

00 00964419734:611405 1 - 00 88042ca   That error...........

00 00964419734:611408 1 - 00 88042ca   Problem..............

		return rc;

	/* register 'device' debug area, used for all DBF_DEV_XXX calls */

	device->debug_area = debug_register(device->cdev->dev.bus_id, 0, 2,

	device->debug_area = debug_register(device->cdev->dev.bus_id, 1, 2,

					    8 * sizeof (long));

	debug_register_view(device->debug_area, &debug_sprintf_view);

	debug_set_level(device->debug_area, DBF_EMERG);

	init_waitqueue_head(&dasd_init_waitq);

	/* register 'common' DASD debug area, used for all DBF_XXX calls */

	dasd_debug_area = debug_register("dasd", 0, 2, 8 * sizeof (long));

	dasd_debug_area = debug_register("dasd", 1, 2, 8 * sizeof (long));

	if (dasd_debug_area == NULL) {

		rc = -ENOMEM;

		goto failed;

 *

 * /proc interface for the dasd driver.

 *

 * $Revision: 1.31 $

 * $Revision: 1.32 $

 */

#include <linux/config.h>

#include <linux/ctype.h>

#include <linux/seq_file.h>

#include <linux/vmalloc.h>

#include <linux/proc_fs.h>

#include <asm/debug.h>

#include <asm/uaccess.h>

{

	int rc;

	TAPE_DBF_AREA = debug_register ( "tape_34xx", 1, 2, 4*sizeof(long));

	TAPE_DBF_AREA = debug_register ( "tape_34xx", 2, 2, 4*sizeof(long));

	debug_register_view(TAPE_DBF_AREA, &debug_sprintf_view);

#ifdef DBF_LIKE_HELL

	debug_set_level(TAPE_DBF_AREA, 6);

#endif

	DBF_EVENT(3, "34xx init: $Revision: 1.21 $\n");

	DBF_EVENT(3, "34xx init: $Revision: 1.23 $\n");

	/* Register driver for 3480/3490 tapes. */

	rc = ccw_driver_register(&tape_34xx_driver);

	if (rc)

MODULE_DEVICE_TABLE(ccw, tape_34xx_ids);

MODULE_AUTHOR("(C) 2001-2002 IBM Deutschland Entwicklung GmbH");

MODULE_DESCRIPTION("Linux on zSeries channel attached 3480 tape "

		   "device driver ($Revision: 1.21 $)");

		   "device driver ($Revision: 1.23 $)");

MODULE_LICENSE("GPL");

module_init(tape_34xx_init);