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docs: s390: s390dbf: typos and formatting, update crash command
Signed-off-by: Steffen Maier <maier@linux.ibm.com> Acked-by: Christian Borntraeger <borntraeger@de.ibm.com> Message-Id: <1562149189-1417-4-git-send-email-maier@linux.ibm.com> Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This commit is contained in:
Steffen Maier
Vasily Gorbik
parent
0328e519a7
commit
499723d120
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@ -23,7 +23,8 @@ The debug feature may also very useful for kernel and driver development.
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Design:
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-------
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Kernel components (e.g. device drivers) can register themselves at the debug
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feature with the function call debug_register(). This function initializes a
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feature with the function call :c:func:`debug_register()`.
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This function initializes a
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debug log for the caller. For each debug log exists a number of debug areas
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where exactly one is active at one time. Each debug area consists of contiguous
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pages in memory. In the debug areas there are stored debug entries (log records)
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@ -44,8 +45,9 @@ The debug areas themselves are also ordered in form of a ring buffer.
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When an exception is thrown in the last debug area, the following debug
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entries are then written again in the very first area.
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There are three versions for the event- and exception-calls: One for
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logging raw data, one for text and one for numbers.
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There are four versions for the event- and exception-calls: One for
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logging raw data, one for text, one for numbers (unsigned int and long),
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and one for sprintf-like formatted strings.
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Each debug entry contains the following data:
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@ -56,29 +58,29 @@ Each debug entry contains the following data:
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- Flag, if entry is an exception or not
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The debug logs can be inspected in a live system through entries in
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the debugfs-filesystem. Under the toplevel directory "s390dbf" there is
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the debugfs-filesystem. Under the toplevel directory "``s390dbf``" there is
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a directory for each registered component, which is named like the
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corresponding component. The debugfs normally should be mounted to
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/sys/kernel/debug therefore the debug feature can be accessed under
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/sys/kernel/debug/s390dbf.
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``/sys/kernel/debug`` therefore the debug feature can be accessed under
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``/sys/kernel/debug/s390dbf``.
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The content of the directories are files which represent different views
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to the debug log. Each component can decide which views should be
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used through registering them with the function debug_register_view().
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used through registering them with the function :c:func:`debug_register_view()`.
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Predefined views for hex/ascii, sprintf and raw binary data are provided.
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It is also possible to define other views. The content of
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a view can be inspected simply by reading the corresponding debugfs file.
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All debug logs have an actual debug level (range from 0 to 6).
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The default level is 3. Event and Exception functions have a 'level'
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The default level is 3. Event and Exception functions have a :c:data:`level`
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parameter. Only debug entries with a level that is lower or equal
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than the actual level are written to the log. This means, when
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writing events, high priority log entries should have a low level
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value whereas low priority entries should have a high one.
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The actual debug level can be changed with the help of the debugfs-filesystem
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through writing a number string "x" to the 'level' debugfs file which is
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through writing a number string "x" to the ``level`` debugfs file which is
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provided for every debug log. Debugging can be switched off completely
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by using "-" on the 'level' debugfs file.
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by using "-" on the ``level`` debugfs file.
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Example::
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@ -86,21 +88,21 @@ Example::
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It is also possible to deactivate the debug feature globally for every
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debug log. You can change the behavior using 2 sysctl parameters in
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/proc/sys/s390dbf:
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``/proc/sys/s390dbf``:
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There are currently 2 possible triggers, which stop the debug feature
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globally. The first possibility is to use the "debug_active" sysctl. If
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set to 1 the debug feature is running. If "debug_active" is set to 0 the
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globally. The first possibility is to use the ``debug_active`` sysctl. If
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set to 1 the debug feature is running. If ``debug_active`` is set to 0 the
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debug feature is turned off.
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The second trigger which stops the debug feature is a kernel oops.
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That prevents the debug feature from overwriting debug information that
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happened before the oops. After an oops you can reactivate the debug feature
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by piping 1 to /proc/sys/s390dbf/debug_active. Nevertheless, its not
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by piping 1 to ``/proc/sys/s390dbf/debug_active``. Nevertheless, it's not
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suggested to use an oopsed kernel in a production environment.
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If you want to disallow the deactivation of the debug feature, you can use
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the "debug_stoppable" sysctl. If you set "debug_stoppable" to 0 the debug
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the ``debug_stoppable`` sysctl. If you set ``debug_stoppable`` to 0 the debug
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feature cannot be stopped. If the debug feature is already stopped, it
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will stay deactivated.
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@ -113,16 +115,18 @@ Kernel Interfaces:
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Predefined views:
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-----------------
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extern struct debug_view debug_hex_ascii_view;
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.. code-block:: c
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extern struct debug_view debug_raw_view;
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extern struct debug_view debug_hex_ascii_view;
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extern struct debug_view debug_sprintf_view;
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extern struct debug_view debug_raw_view;
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extern struct debug_view debug_sprintf_view;
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Examples
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--------
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::
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.. code-block:: c
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/*
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* hex_ascii- + raw-view Example
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@ -131,15 +135,15 @@ Examples
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#include <linux/init.h>
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#include <asm/debug.h>
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static debug_info_t* debug_info;
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static debug_info_t *debug_info;
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static int init(void)
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{
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/* register 4 debug areas with one page each and 4 byte data field */
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debug_info = debug_register ("test", 1, 4, 4 );
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debug_register_view(debug_info,&debug_hex_ascii_view);
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debug_register_view(debug_info,&debug_raw_view);
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debug_info = debug_register("test", 1, 4, 4 );
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debug_register_view(debug_info, &debug_hex_ascii_view);
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debug_register_view(debug_info, &debug_raw_view);
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debug_text_event(debug_info, 4 , "one ");
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debug_int_exception(debug_info, 4, 4711);
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@ -150,13 +154,13 @@ Examples
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static void cleanup(void)
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{
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debug_unregister (debug_info);
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debug_unregister(debug_info);
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}
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module_init(init);
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module_exit(cleanup);
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::
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.. code-block:: c
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/*
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* sprintf-view Example
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@ -165,15 +169,15 @@ Examples
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#include <linux/init.h>
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#include <asm/debug.h>
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static debug_info_t* debug_info;
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static debug_info_t *debug_info;
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static int init(void)
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{
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/* register 4 debug areas with one page each and data field for */
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/* format string pointer + 2 varargs (= 3 * sizeof(long)) */
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debug_info = debug_register ("test", 1, 4, sizeof(long) * 3);
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debug_register_view(debug_info,&debug_sprintf_view);
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debug_info = debug_register("test", 1, 4, sizeof(long) * 3);
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debug_register_view(debug_info, &debug_sprintf_view);
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debug_sprintf_event(debug_info, 2 , "first event in %s:%i\n",__FILE__,__LINE__);
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debug_sprintf_exception(debug_info, 1, "pointer to debug info: %p\n",&debug_info);
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@ -183,7 +187,7 @@ Examples
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static void cleanup(void)
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{
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debug_unregister (debug_info);
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debug_unregister(debug_info);
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}
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module_init(init);
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@ -252,7 +256,7 @@ Define 4 pages for the debug areas of debug feature "dasd"::
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> echo "4" > /sys/kernel/debug/s390dbf/dasd/pages
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Stooping the debug feature
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Stopping the debug feature
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--------------------------
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Example:
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@ -264,10 +268,11 @@ Example:
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> echo 0 > /proc/sys/s390dbf/debug_active
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lcrash Interface
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crash Interface
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----------------
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It is planned that the dump analysis tool lcrash gets an additional command
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's390dbf' to display all the debug logs. With this tool it will be possible
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The ``crash`` tool since v5.1.0 has a built-in command
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``s390dbf`` to display all the debug logs or export them to the file system.
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With this tool it is possible
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to investigate the debug logs on a live system and with a memory dump after
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a system crash.
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@ -276,8 +281,8 @@ Investigating raw memory
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One last possibility to investigate the debug logs at a live
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system and after a system crash is to look at the raw memory
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under VM or at the Service Element.
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It is possible to find the anker of the debug-logs through
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the 'debug_area_first' symbol in the System map. Then one has
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It is possible to find the anchor of the debug-logs through
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the ``debug_area_first`` symbol in the System map. Then one has
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to follow the correct pointers of the data-structures defined
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in debug.h and find the debug-areas in memory.
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Normally modules which use the debug feature will also have
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@ -286,7 +291,7 @@ this pointer it will also be possible to find the debug logs in
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memory.
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For this method it is recommended to use '16 * x + 4' byte (x = 0..n)
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for the length of the data field in debug_register() in
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for the length of the data field in :c:func:`debug_register()` in
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order to see the debug entries well formatted.
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@ -295,7 +300,7 @@ Predefined Views
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There are three predefined views: hex_ascii, raw and sprintf.
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The hex_ascii view shows the data field in hex and ascii representation
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(e.g. '45 43 4b 44 | ECKD').
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(e.g. ``45 43 4b 44 | ECKD``).
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The raw view returns a bytestream as the debug areas are stored in memory.
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The sprintf view formats the debug entries in the same way as the sprintf
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@ -335,18 +340,20 @@ The format of the raw view is:
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- datafield
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A typical line of the hex_ascii view will look like the following (first line
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is only for explanation and will not be displayed when 'cating' the view):
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is only for explanation and will not be displayed when 'cating' the view)::
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area time level exception cpu caller data (hex + ascii)
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--------------------------------------------------------------------------
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00 00964419409:440690 1 - 00 88023fe
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area time level exception cpu caller data (hex + ascii)
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--------------------------------------------------------------------------
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00 00964419409:440690 1 - 00 88023fe
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Defining views
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--------------
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Views are specified with the 'debug_view' structure. There are defined
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callback functions which are used for reading and writing the debugfs files::
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callback functions which are used for reading and writing the debugfs files:
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.. code-block:: c
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struct debug_view {
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char name[DEBUG_MAX_PROCF_LEN];
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@ -357,7 +364,9 @@ callback functions which are used for reading and writing the debugfs files::
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void* private_data;
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};
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where::
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where:
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.. code-block:: c
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typedef int (debug_header_proc_t) (debug_info_t* id,
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struct debug_view* view,
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@ -395,10 +404,10 @@ Then 'header_proc' and 'format_proc' are called for each
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existing debug entry.
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The input_proc can be used to implement functionality when it is written to
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the view (e.g. like with 'echo "0" > /sys/kernel/debug/s390dbf/dasd/level).
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the view (e.g. like with ``echo "0" > /sys/kernel/debug/s390dbf/dasd/level``).
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For header_proc there can be used the default function
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debug_dflt_header_fn() which is defined in debug.h.
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:c:func:`debug_dflt_header_fn()` which is defined in debug.h.
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and which produces the same header output as the predefined views.
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E.g::
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@ -407,7 +416,9 @@ E.g::
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In order to see how to use the callback functions check the implementation
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of the default views!
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Example::
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Example:
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.. code-block:: c
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#include <asm/debug.h>
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@ -423,21 +434,20 @@ Example::
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};
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static int debug_test_format_fn(
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debug_info_t * id, struct debug_view *view,
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debug_info_t *id, struct debug_view *view,
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char *out_buf, const char *in_buf
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)
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{
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int i, rc = 0;
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if(id->buf_size >= 4) {
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if (id->buf_size >= 4) {
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int msg_nr = *((int*)in_buf);
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if(msg_nr < sizeof(messages)/sizeof(char*) - 1)
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if (msg_nr < sizeof(messages) / sizeof(char*) - 1)
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rc += sprintf(out_buf, "%s", messages[msg_nr]);
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else
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rc += sprintf(out_buf, UNKNOWNSTR, msg_nr);
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}
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out:
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return rc;
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return rc;
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}
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struct debug_view debug_test_view = {
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@ -452,13 +462,17 @@ Example::
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test:
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=====
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::
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.. code-block:: c
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debug_info_t *debug_info;
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int i;
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...
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debug_info = debug_register ("test", 0, 4, 4 ));
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debug_info = debug_register("test", 0, 4, 4);
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debug_register_view(debug_info, &debug_test_view);
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for(i = 0; i < 10; i ++) debug_int_event(debug_info, 1, i);
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for (i = 0; i < 10; i ++)
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debug_int_event(debug_info, 1, i);
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::
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> cat /sys/kernel/debug/s390dbf/test/myview
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00 00964419734:611402 1 - 00 88042ca This error...........
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