dyndbg: add source filename to prefix

Printing the line number without the file is of limited usefulness.

Knowing the filename also makes it also easier to relate the logged
information to the controlfile.

Example:

    # modprobe test_dynamic_debug
    # echo 'file test_dynamic_debug.c =pfsl' > /proc/dynamic_debug/control
    # echo 1 > /sys/module/test_dynamic_debug/parameters/do_prints
    # dmesg | tail -2
    [   71.802212] do_cats:lib/test_dynamic_debug.c:103: test_dd: doing categories
    [   71.802227] do_levels:lib/test_dynamic_debug.c:123: test_dd: doing levels
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Acked-by: Jim Cromie <jim.cromie@gmail.com>
Acked-by: Jason Baron <jbaron@akamai.com>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Link: https://lore.kernel.org/r/20230709-dyndbg-filename-v2-3-fd83beef0925@weissschuh.netSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/admin-guide/dynamic-debug-howto.rst

@@ -216,13 +216,14 @@ The flags are::
   t    Include thread ID, or <intr>
   m    Include module name
   f    Include the function name
+  s    Include the source file name
   l    Include line number
 
 For ``print_hex_dump_debug()`` and ``print_hex_dump_bytes()``, only
 the ``p`` flag has meaning, other flags are ignored.
 
-Note the regexp ``^[-+=][flmpt_]+$`` matches a flags specification.
-To clear all flags at once, use ``=_`` or ``-flmpt``.
+Note the regexp ``^[-+=][fslmpt_]+$`` matches a flags specification.
+To clear all flags at once, use ``=_`` or ``-fslmpt``.
 
 
 Debug messages during Boot Process

include/linux/dynamic_debug.h

@@ -37,10 +37,12 @@ struct _ddebug {
 #define _DPRINTK_FLAGS_INCL_FUNCNAME	(1<<2)
 #define _DPRINTK_FLAGS_INCL_LINENO	(1<<3)
 #define _DPRINTK_FLAGS_INCL_TID		(1<<4)
+#define _DPRINTK_FLAGS_INCL_SOURCENAME	(1<<5)
 
 #define _DPRINTK_FLAGS_INCL_ANY		\
 	(_DPRINTK_FLAGS_INCL_MODNAME | _DPRINTK_FLAGS_INCL_FUNCNAME |\
-	 _DPRINTK_FLAGS_INCL_LINENO  | _DPRINTK_FLAGS_INCL_TID)
+	 _DPRINTK_FLAGS_INCL_LINENO  | _DPRINTK_FLAGS_INCL_TID |\
+	 _DPRINTK_FLAGS_INCL_SOURCENAME)
 
 #if defined DEBUG
 #define _DPRINTK_FLAGS_DEFAULT _DPRINTK_FLAGS_PRINT

lib/dynamic_debug.c

@@ -92,6 +92,7 @@ static const struct { unsigned flag:8; char opt_char; } opt_array[] = {
 	{ _DPRINTK_FLAGS_PRINT, 'p' },
 	{ _DPRINTK_FLAGS_INCL_MODNAME, 'm' },
 	{ _DPRINTK_FLAGS_INCL_FUNCNAME, 'f' },
+	{ _DPRINTK_FLAGS_INCL_SOURCENAME, 's' },
 	{ _DPRINTK_FLAGS_INCL_LINENO, 'l' },
 	{ _DPRINTK_FLAGS_INCL_TID, 't' },
 	{ _DPRINTK_FLAGS_NONE, '_' },
@@ -836,6 +837,9 @@ static char *__dynamic_emit_prefix(const struct _ddebug *desc, char *buf)
 	if (desc->flags & _DPRINTK_FLAGS_INCL_FUNCNAME)
 		pos += snprintf(buf + pos, remaining(pos), "%s:",
 				desc->function);
+	if (desc->flags & _DPRINTK_FLAGS_INCL_SOURCENAME)
+		pos += snprintf(buf + pos, remaining(pos), "%s:",
+				trim_prefix(desc->filename));
 	if (desc->flags & _DPRINTK_FLAGS_INCL_LINENO)
 		pos += snprintf(buf + pos, remaining(pos), "%d:",
 				desc->lineno);