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diff --git a/Documentation/s390/s390dbf.txt b/Documentation/s390/s390dbf.txt deleted file mode 100644 index 61329fd62e89..000000000000 --- a/Documentation/s390/s390dbf.txt +++ /dev/null @@ -1,667 +0,0 @@ -S390 Debug Feature -================== - -files: arch/s390/kernel/debug.c - arch/s390/include/asm/debug.h - -Description: ------------- -The goal of this feature is to provide a kernel debug logging API -where log records can be stored efficiently in memory, where each component -(e.g. device drivers) can have one separate debug log. -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 fails, -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: -------- -Kernel components (e.g. device drivers) can register themselves at the debug -feature with the function call debug_register(). This function initializes a -debug log for the caller. For each debug log exists a number of debug areas -where exactly one is active at one time. Each debug area consists of contiguous -pages in memory. In the debug areas there are stored debug entries (log records) -which are written by event- and exception-calls. - -An event-call writes the specified debug entry to the active debug -area and updates the log pointer for the active area. If the end -of the active debug area is reached, a wrap around is done (ring buffer) -and the next debug entry will be written at the beginning of the active -debug area. - -An exception-call writes the specified debug entry to the log and -switches to the next debug area. This is done in order to be sure -that the records which describe the origin of the exception are not -overwritten when a wrap around for the current area occurs. - -The debug areas themselves are also ordered in form of a ring buffer. -When an exception is thrown in the last debug area, the following debug -entries are then written again in the very first area. - -There are three versions for the event- and exception-calls: One for -logging raw data, one for text and one for numbers. - -Each debug entry contains the following data: - -- Timestamp -- Cpu-Number of calling task -- Level of debug entry (0...6) -- Return Address to caller -- Flag, if entry is an exception or not - -The debug logs can be inspected in a live system through entries in -the debugfs-filesystem. Under the toplevel directory "s390dbf" there is -a directory for each registered component, which is named like the -corresponding component. The debugfs normally should be mounted to -/sys/kernel/debug therefore the debug feature can be accessed under -/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 debugfs file. - -All debug logs have an actual debug level (range from 0 to 6). -The default level is 3. Event and Exception functions have a 'level' -parameter. Only debug entries with a level that is lower or equal -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 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' debugfs file. - -Example: - -> 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 -/proc/sys/s390dbf: -There are currently 2 possible triggers, which stop the debug feature -globally. The first possibility is to use the "debug_active" sysctl. If -set to 1 the debug feature is running. If "debug_active" is set to 0 the -debug feature is turned off. -The second trigger which stops the debug feature is a kernel oops. -That prevents the debug feature from overwriting debug information that -happened before the oops. After an oops you can reactivate the debug feature -by piping 1 to /proc/sys/s390dbf/debug_active. Nevertheless, its not -suggested to use an oopsed kernel in a production environment. -If you want to disallow the deactivation of the debug feature, you can use -the "debug_stoppable" sysctl. If you set "debug_stoppable" to 0 the debug -feature cannot be stopped. If the debug feature is already stopped, it -will stay deactivated. - -Kernel Interfaces: ------------------- - ----------------------------------------------------------------------------- -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 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 - -Return Value: Handle for generated debug area - NULL if register failed - -Description: Allocates memory for a debug log - Must not be called within an interrupt handler - ----------------------------------------------------------------------------- -debug_info_t *debug_register_mode(char *name, int pages, int nr_areas, - int buf_size, mode_t mode, uid_t uid, - gid_t gid); - -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 - mode: File mode for debugfs files. E.g. S_IRWXUGO - uid: User ID for debugfs files. Currently only 0 is - supported. - gid: Group ID for debugfs files. Currently only 0 is - supported. - -Return Value: Handle for generated debug area - NULL if register failed - -Description: Allocates memory for a debug log - Must not be called within an interrupt handler - ---------------------------------------------------------------------------- -void debug_unregister (debug_info_t * id); - -Parameter: id: handle for debug log - -Return Value: none - -Description: frees memory for a debug log and removes all registered debug - views. - Must not be called within an interrupt handler - ---------------------------------------------------------------------------- -void debug_set_level (debug_info_t * id, int new_level); - -Parameter: id: handle for debug log - new_level: new debug level - -Return Value: none - -Description: Sets new actual debug level if new_level is valid. - ---------------------------------------------------------------------------- -bool debug_level_enabled (debug_info_t * id, int level); - -Parameter: id: handle for debug log - level: debug level - -Return Value: True if level is less or equal to the current debug level. - -Description: Returns true if debug events for the specified level would be - logged. Otherwise returns false. ---------------------------------------------------------------------------- -void debug_stop_all(void); - -Parameter: none - -Return Value: none - -Description: stops the debug feature if stopping is allowed. Currently - used in case of a kernel oops. - ---------------------------------------------------------------------------- -debug_entry_t* debug_event (debug_info_t* id, int level, void* data, - int length); - -Parameter: id: handle for debug log - level: debug level - data: pointer to data for debug entry - length: length of data in bytes - -Return Value: Address of written debug entry - -Description: writes debug entry to active debug area (if level <= actual - debug level) - ---------------------------------------------------------------------------- -debug_entry_t* debug_int_event (debug_info_t * id, int level, - unsigned int data); -debug_entry_t* debug_long_event(debug_info_t * id, int level, - unsigned long data); - -Parameter: id: handle for debug log - level: debug level - data: integer value for debug entry - -Return Value: Address of written debug entry - -Description: writes debug entry to active debug area (if level <= actual - debug level) - ---------------------------------------------------------------------------- -debug_entry_t* debug_text_event (debug_info_t * id, int level, - const char* data); - -Parameter: id: handle for debug log - level: debug level - data: string for debug entry - -Return Value: Address of written debug entry - -Description: writes debug entry in ascii format to active debug area - (if level <= actual debug level) - ---------------------------------------------------------------------------- -debug_entry_t* debug_sprintf_event (debug_info_t * id, int level, - char* string,...); - -Parameter: id: handle for debug log - level: debug level - string: format string for debug entry - ...: varargs used as in sprintf() - -Return Value: Address of written debug entry - -Description: writes debug entry with format string and varargs (longs) to - active debug area (if level $<=$ actual debug level). - floats and long long datatypes cannot be used as varargs. - ---------------------------------------------------------------------------- - -debug_entry_t* debug_exception (debug_info_t* id, int level, void* data, - int length); - -Parameter: id: handle for debug log - level: debug level - data: pointer to data for debug entry - length: length of data in bytes - -Return Value: Address of written debug entry - -Description: writes debug entry to active debug area (if level <= actual - debug level) and switches to next debug area - ---------------------------------------------------------------------------- -debug_entry_t* debug_int_exception (debug_info_t * id, int level, - unsigned int data); -debug_entry_t* debug_long_exception(debug_info_t * id, int level, - unsigned long data); - -Parameter: id: handle for debug log - level: debug level - data: integer value for debug entry - -Return Value: Address of written debug entry - -Description: writes debug entry to active debug area (if level <= actual - debug level) and switches to next debug area - ---------------------------------------------------------------------------- -debug_entry_t* debug_text_exception (debug_info_t * id, int level, - const char* data); - -Parameter: id: handle for debug log - level: debug level - data: string for debug entry - -Return Value: Address of written debug entry - -Description: writes debug entry in ascii format to active debug area - (if level <= actual debug level) and switches to next debug - area - ---------------------------------------------------------------------------- -debug_entry_t* debug_sprintf_exception (debug_info_t * id, int level, - char* string,...); - -Parameter: id: handle for debug log - level: debug level - string: format string for debug entry - ...: varargs used as in sprintf() - -Return Value: Address of written debug entry - -Description: writes debug entry with format string and varargs (longs) to - active debug area (if level $<=$ actual debug level) and - switches to next debug area. - floats and long long datatypes cannot be used as varargs. - ---------------------------------------------------------------------------- - -int debug_register_view (debug_info_t * id, struct debug_view *view); - -Parameter: id: handle for debug log - view: pointer to debug view struct - -Return Value: 0 : ok - < 0: Error - -Description: registers new debug view and creates debugfs dir entry - ---------------------------------------------------------------------------- -int debug_unregister_view (debug_info_t * id, struct debug_view *view); - -Parameter: id: handle for debug log - view: pointer to debug view struct - -Return Value: 0 : ok - < 0: Error - -Description: unregisters debug view and removes debugfs dir entry - - - -Predefined views: ------------------ - -extern struct debug_view debug_hex_ascii_view; -extern struct debug_view debug_raw_view; -extern struct debug_view debug_sprintf_view; - -Examples --------- - -/* - * hex_ascii- + raw-view Example - */ - -#include <linux/init.h> -#include <asm/debug.h> - -static debug_info_t* debug_info; - -static int init(void) -{ - /* register 4 debug areas with one page each and 4 byte data field */ - - 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); - - debug_text_event(debug_info, 4 , "one "); - debug_int_exception(debug_info, 4, 4711); - debug_event(debug_info, 3, &debug_info, 4); - - return 0; -} - -static void cleanup(void) -{ - debug_unregister (debug_info); -} - -module_init(init); -module_exit(cleanup); - ---------------------------------------------------------------------------- - -/* - * sprintf-view Example - */ - -#include <linux/init.h> -#include <asm/debug.h> - -static debug_info_t* debug_info; - -static int init(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", 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__); - debug_sprintf_exception(debug_info, 1, "pointer to debug info: %p\n",&debug_info); - - return 0; -} - -static void cleanup(void) -{ - debug_unregister (debug_info); -} - -module_init(init); -module_exit(cleanup); - - - -Debugfs Interface ----------------- -Views to the debug logs can be investigated through reading the corresponding -debugfs-files: - -Example: - -> ls /sys/kernel/debug/s390dbf/dasd -flush hex_ascii level pages raw -> cat /sys/kernel/debug/s390dbf/dasd/hex_ascii | sort -k2,2 -s -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 /sys/kernel/debug/s390dbf/dasd/level -3 -> 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 debugfs file "flush". When using "-" all debug areas -are flushed. - -Examples: - -1. Flush debug area 0: -> echo "0" > /sys/kernel/debug/s390dbf/dasd/flush - -2. Flush all debug areas: -> 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 --------------------------- -Example: - -1. Check if stopping is allowed -> cat /proc/sys/s390dbf/debug_stoppable -2. Stop debug feature -> echo 0 > /proc/sys/s390dbf/debug_active - -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/exception functions 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. - -IMPORTANT: Using "%s" in sprintf event functions is dangerous. You can only -use "%s" in the sprintf event functions, if the memory for the passed string is -available as long as the debug feature exists. The reason behind this is that -due to performance considerations only a pointer to the string is stored in -the debug feature. If you log a string that is freed afterwards, you will get -an OOPS when inspecting the debug feature, because then the debug feature will -access the already freed memory. - -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 debugfs 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 debugfs 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 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" > /sys/kernel/debug/s390dbf/dasd/level). - -For header_proc there can be used the default function -debug_dflt_header_fn() which is defined 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 /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.............. -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 |