s390dbf.txt

《嵌入式系统设计与实例开发实验教材二源码》Linux内核移植与编译实验

    debug_int_exception(debug_info, 4, 4711);
    debug_event(debug_info, 3, &debug_info, 4);

    return 0;
}

void cleanup_module(void)
{
    debug_unregister (debug_info);
}

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

/*
 * sprintf-view Example
 */

#include <linux/module.h>
#include <asm/debug.h>

static debug_info_t* debug_info;

int init_module(void)
{
    /* 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_register_view(debug_info,&debug_sprintf_view);

    debug_sprintf_event(debug_info, 2 , "first event in %s:%i\n",__FILE__,__LINE__);
    debug_sprintf_exception(debug_info, 1, "pointer to debug info: %p\n",&debug_info);

    return 0;
}

void cleanup_module(void)
{
    debug_unregister (debug_info);
}



ProcFS Interface
----------------
Views to the debug logs can be investigated through reading the corresponding 
proc-files:

Example:

> ls /proc/s390dbf/dasd
flush  hex_ascii  level      raw 
> cat /proc/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 | ....
00 00974733272:682281 1 * 02 0006ab08  41 4c 4c 43 | EXCP 
01 00974733272:682284 2 - 02 0006ab16  45 43 4b 44 | ECKD
01 00974733272:682287 2 - 02 0006ab28  00 00 00 04 | ....
01 00974733272:682289 2 - 02 0006ab3e  00 00 00 20 | ... 
01 00974733272:682297 2 - 02 0006ad7e  07 ea 4a 90 | ....
01 00974733272:684384 2 - 00 0006ade6  46 52 45 45 | FREE
01 00974733272:684388 2 - 00 0006adf6  07 ea 4a 90 | ....

See section about predefined views for explanation of the above output!

Changing the debug level
------------------------

Example:


> cat /proc/s390dbf/dasd/level
3
> echo "5" > /proc/s390dbf/dasd/level
> cat /proc/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
are flushed.

Examples:

1. Flush debug area 0:
> echo "0" > /proc/s390dbf/dasd/flush  

2. Flush all debug areas:
> echo "-" > /proc/s390dbf/dasd/flush

lcrash Interface
----------------
It is planned that the dump analysis tool lcrash gets an additional command
's390dbf' to display all the debug logs. With this tool it will be possible 
to investigate the debug logs on a live system and with a memory dump after 
a system crash.

Investigating raw memory
------------------------
One last possibility to investigate the debug logs at a live
system and after a system crash is to look at the raw memory
under VM or at the Service Element.
It is possible to find the anker of the debug-logs through
the 'debug_area_first' symbol in the System map. Then one has
to follow the correct pointers of the data-structures defined
in debug.h and find the debug-areas in memory.
Normally modules which use the debug feature will also have
a global variable with the pointer to the debug-logs. Following
this pointer it will also be possible to find the debug logs in
memory.

For this method it is recommended to use '16 * x + 4' byte (x = 0..n)
for the length of the data field in debug_register() in
order to see the debug entries well formatted.


Predefined Views
----------------

There are three predefined views: hex_ascii, raw and sprintf. 
The hex_ascii view shows the data field in hex and ascii representation 
(e.g. '45 43 4b 44 | ECKD'). 
The raw view returns a bytestream as the debug areas are stored in memory.

The sprintf view formats the debug entries in the same way as the sprintf
function would do. The sprintf event/expection fuctions write to the 
debug entry a pointer to the format string (size = sizeof(long)) 
and for each vararg a long value. So e.g. for a debug entry with a format 
string plus two varargs one would need to allocate a (3 * sizeof(long)) 
byte data area in the debug_register() function.


NOTE: If using the sprintf view do NOT use other event/exception functions
than the sprintf-event and -exception functions.

The format of the hex_ascii and sprintf view is as follows:
- Number of area
- Timestamp (formatted as seconds and microseconds since 00:00:00 Coordinated 
  Universal Time (UTC), January 1, 1970)
- level of debug entry
- Exception flag (* = Exception)
- Cpu-Number of calling task
- Return Address to caller
- data field

The format of the raw view is:
- Header as described in debug.h
- datafield 

A typical line of the hex_ascii view will look like the following (first line 
is only for explanation and will not be displayed when 'cating' the view):

area  time           level exception cpu caller    data (hex + ascii)
--------------------------------------------------------------------------
00    00964419409:440690 1 -         00  88023fe   


Defining views
--------------

Views are specified with the 'debug_view' structure. There are defined
callback functions which are used for reading and writing the proc files:

struct debug_view {
        char name[DEBUG_MAX_PROCF_LEN];  
        debug_prolog_proc_t* prolog_proc; 
        debug_header_proc_t* header_proc;
        debug_format_proc_t* format_proc;
        debug_input_proc_t*  input_proc;
	void*                private_data;
};

where

typedef int (debug_header_proc_t) (debug_info_t* id,
                                   struct debug_view* view,
                                   int area,
                                   debug_entry_t* entry,
                                   char* out_buf);

typedef int (debug_format_proc_t) (debug_info_t* id,
                                   struct debug_view* view, char* out_buf,
                                   const char* in_buf);
typedef int (debug_prolog_proc_t) (debug_info_t* id,
                                   struct debug_view* view,
                                   char* out_buf);
typedef int (debug_input_proc_t) (debug_info_t* id,
                                  struct debug_view* view,
                                  struct file* file, const char* user_buf,
                                  size_t in_buf_size, loff_t* offset);


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:

"prolog_proc output"

"header_proc output 1"  "format_proc output 1"
"header_proc output 2"  "format_proc output 2"
"header_proc output 3"  "format_proc output 3"
...

When a view is read from the proc fs, 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).

For header_proc there can be used the default function
debug_dflt_header_fn() which is defined in in debug.h.
and which produces the same header output as the predefined views.
E.g:
00 00964419409:440761 2 - 00 88023ec

In order to see how to use the callback functions check the implementation
of the default views!

Example

#include <asm/debug.h>

#define UNKNOWNSTR "data: %08x"

const char* messages[] =
{"This error...........\n",
 "That error...........\n",
 "Problem..............\n",
 "Something went wrong.\n",
 "Everything ok........\n",
 NULL
};

static int debug_test_format_fn(
   debug_info_t * id, struct debug_view *view, 
   char *out_buf, const char *in_buf
)
{
  int i, rc = 0;

  if(id->buf_size >= 4) {
     int msg_nr = *((int*)in_buf);
     if(msg_nr < sizeof(messages)/sizeof(char*) - 1)
        rc += sprintf(out_buf, "%s", messages[msg_nr]);	
     else
        rc += sprintf(out_buf, UNKNOWNSTR, msg_nr);
  }
 out:
   return rc;
}

struct debug_view debug_test_view = {
  "myview",                 /* name of view */
  NULL,                     /* no prolog */
  &debug_dflt_header_fn,    /* default header for each entry */
  &debug_test_format_fn,    /* our own format function */
  NULL,                     /* no input function */
  NULL                      /* no private data */
};

=====
test:
=====
debug_info_t *debug_info;
...
debug_info = debug_register ("test", 0, 4, 4 ));
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
00 00964419734:611402 1 - 00 88042ca   This error...........
00 00964419734:611405 1 - 00 88042ca   That error...........
00 00964419734:611408 1 - 00 88042ca   Problem..............
00 00964419734:611411 1 - 00 88042ca   Something went wrong.
00 00964419734:611414 1 - 00 88042ca   Everything ok........
00 00964419734:611417 1 - 00 88042ca   data: 00000005
00 00964419734:611419 1 - 00 88042ca   data: 00000006
00 00964419734:611422 1 - 00 88042ca   data: 00000007
00 00964419734:611425 1 - 00 88042ca   data: 00000008
00 00964419734:611428 1 - 00 88042ca   data: 00000009