Dynamic Debug: Introduce ddebug_query= boot parameter

Dynamic debug lacks the ability to enable debug messages at boot time. One could patch initramfs or service startup scripts to write to /sys/../dynamic_debug/control, but this sucks. This patch makes it possible to pass a query in the same format one can write to /sys/../dynamic_debug/control via boot param. When dynamic debug gets initialized, this query will automatically be applied. Signed-off-by: Thomas Renninger <trenn@suse.de> Acked-by: jbaron@redhat.com Acked-by: Pekka Enberg <penberg@cs.helsinki.fi> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

Dynamic Debug: Introduce ddebug_query= boot parameter
Dynamic debug lacks the ability to enable debug messages at boot time. One could patch initramfs or service startup scripts to write to /sys/../dynamic_debug/control, but this sucks. This patch makes it possible to pass a query in the same format one can write to /sys/../dynamic_debug/control via boot param. When dynamic debug gets initialized, this query will automatically be applied. Signed-off-by: Thomas Renninger <trenn@suse.de> Acked-by: jbaron@redhat.com Acked-by: Pekka Enberg <penberg@cs.helsinki.fi> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Thomas Renninger · Greg Kroah-Hartman
1 parent fd89cfb871
Showing 3 changed files with 52 additions and 2 deletions Side-by-side Diff
Documentation/dynamic-debug-howto.txt
Documentation/kernel-parameters.txt
lib/dynamic_debug.c
@@ -24,7 +24,7 @@
    read to display the complete list of known debug statements, to help guide you
  
 Controlling dynamic debug Behaviour
-===============================
+===================================
  
 The behaviour of pr_debug()/dev_debug()s are controlled via writing to a
 control file in the 'debugfs' filesystem. Thus, you must first mount the debugfs
@@ -211,6 +211,26 @@
 Note the regexp ^[-+=][scp]+$ matches a flags specification.
 Note also that there is no convenient syntax to remove all
 the flags at once, you need to use "-psc".
+
+
+Debug messages during boot process
+==================================
+
+To be able to activate debug messages during the boot process,
+even before userspace and debugfs exists, use the boot parameter:
+ddebug_query="QUERY"
+
+QUERY follows the syntax described above, but must not exceed 1023
+characters. The enablement of debug messages is done as an arch_initcall.
+Thus you can enable debug messages in all code processed after this
+arch_initcall via this boot parameter.
+On an x86 system for example ACPI enablement is a subsys_initcall and
+ddebug_query="file ec.c +p"
+will show early Embedded Controller transactions during ACPI setup if
+your machine (typically a laptop) has an Embedded Controller.
+PCI (or other devices) initialization also is a hot candidate for using
+this boot parameter for debugging purposes.
+
  
 Examples
 ========
@@ -43,10 +43,11 @@
 	AVR32	AVR32 architecture is enabled.
 	AX25	Appropriate AX.25 support is enabled.
 	BLACKFIN Blackfin architecture is enabled.
-	DRM	Direct Rendering Management support is enabled.
 	EDD	BIOS Enhanced Disk Drive Services (EDD) is enabled
 	EFI	EFI Partitioning (GPT) is enabled
 	EIDE	EIDE/ATAPI support is enabled.
+	DRM	Direct Rendering Management support is enabled.
+	DYNAMIC_DEBUG Build in debug messages and enable them at runtime
 	FB	The frame buffer device is enabled.
 	GCOV	GCOV profiling is enabled.
 	HW	Appropriate hardware is enabled.
@@ -569,6 +570,10 @@
 			(one device per port)
 			Format: <port#>,<type>
 			See also Documentation/input/joystick-parport.txt
+
+	ddebug_query=   [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
+			time. See Documentation/dynamic-debug-howto.txt for
+			details.
  
 	debug		[KNL] Enable kernel debugging (events log level).
  
@@ -450,6 +450,19 @@
 	return 0;
 }
  
+static __initdata char ddebug_setup_string[1024];
+static __init int ddebug_setup_query(char *str)
+{
+	if (strlen(str) >= 1024) {
+		pr_warning("ddebug boot param string too large\n");
+		return 0;
+	}
+	strcpy(ddebug_setup_string, str);
+	return 1;
+}
+
+__setup("ddebug_query=", ddebug_setup_query);
+
 /*
  * File_ops->write method for <debugfs>/dynamic_debug/conrol.  Gathers the
  * command text from userspace, parses and executes it.
@@ -769,6 +782,18 @@
 		}
 		ret = ddebug_add_module(iter_start, n, modname);
 	}
+
+	/* ddebug_query boot param got passed -> set it up */
+	if (ddebug_setup_string[0] != '\0') {
+		ret = ddebug_exec_query(ddebug_setup_string);
+		if (ret)
+			pr_warning("Invalid ddebug boot param %s",
+				   ddebug_setup_string);
+		else
+			pr_info("ddebug initialized with string %s",
+				ddebug_setup_string);
+	}
+
 out_free:
 	if (ret) {
 		ddebug_remove_all_tables();
...	...	@@ -24,7 +24,7 @@
24	24	read to display the complete list of known debug statements, to help guide you
25	25
26	26	Controlling dynamic debug Behaviour
27		-===============================
	27	+===================================
28	28
29	29	The behaviour of pr_debug()/dev_debug()s are controlled via writing to a
30	30	control file in the 'debugfs' filesystem. Thus, you must first mount the debugfs
...	...	@@ -211,6 +211,26 @@
211	211	Note the regexp ^[-+=][scp]+$ matches a flags specification.
212	212	Note also that there is no convenient syntax to remove all
213	213	the flags at once, you need to use "-psc".
	214	+
	215	+
	216	+Debug messages during boot process
	217	+==================================
	218	+
	219	+To be able to activate debug messages during the boot process,
	220	+even before userspace and debugfs exists, use the boot parameter:
	221	+ddebug_query="QUERY"
	222	+
	223	+QUERY follows the syntax described above, but must not exceed 1023
	224	+characters. The enablement of debug messages is done as an arch_initcall.
	225	+Thus you can enable debug messages in all code processed after this
	226	+arch_initcall via this boot parameter.
	227	+On an x86 system for example ACPI enablement is a subsys_initcall and
	228	+ddebug_query="file ec.c +p"
	229	+will show early Embedded Controller transactions during ACPI setup if
	230	+your machine (typically a laptop) has an Embedded Controller.
	231	+PCI (or other devices) initialization also is a hot candidate for using
	232	+this boot parameter for debugging purposes.
	233	+
214	234
215	235	Examples
216	236	========
...	...	@@ -43,10 +43,11 @@
43	43	AVR32 AVR32 architecture is enabled.
44	44	AX25 Appropriate AX.25 support is enabled.
45	45	BLACKFIN Blackfin architecture is enabled.
46		- DRM Direct Rendering Management support is enabled.
47	46	EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
48	47	EFI EFI Partitioning (GPT) is enabled
49	48	EIDE EIDE/ATAPI support is enabled.
	49	+ DRM Direct Rendering Management support is enabled.
	50	+ DYNAMIC_DEBUG Build in debug messages and enable them at runtime
50	51	FB The frame buffer device is enabled.
51	52	GCOV GCOV profiling is enabled.
52	53	HW Appropriate hardware is enabled.
...	...	@@ -569,6 +570,10 @@
569	570	(one device per port)
570	571	Format: <port#>,<type>
571	572	See also Documentation/input/joystick-parport.txt
	573	+
	574	+ ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
	575	+ time. See Documentation/dynamic-debug-howto.txt for
	576	+ details.
572	577
573	578	debug [KNL] Enable kernel debugging (events log level).
574	579
...	...	@@ -450,6 +450,19 @@
450	450	return 0;
451	451	}
452	452
	453	+static __initdata char ddebug_setup_string[1024];
	454	+static __init int ddebug_setup_query(char *str)
	455	+{
	456	+ if (strlen(str) >= 1024) {
	457	+ pr_warning("ddebug boot param string too large\n");
	458	+ return 0;
	459	+ }
	460	+ strcpy(ddebug_setup_string, str);
	461	+ return 1;
	462	+}
	463	+
	464	+__setup("ddebug_query=", ddebug_setup_query);
	465	+
453	466	/*
454	467	* File_ops->write method for <debugfs>/dynamic_debug/conrol. Gathers the
455	468	* command text from userspace, parses and executes it.
...	...	@@ -769,6 +782,18 @@
769	782	}
770	783	ret = ddebug_add_module(iter_start, n, modname);
771	784	}
	785	+
	786	+ /* ddebug_query boot param got passed -> set it up */
	787	+ if (ddebug_setup_string[0] != '\0') {
	788	+ ret = ddebug_exec_query(ddebug_setup_string);
	789	+ if (ret)
	790	+ pr_warning("Invalid ddebug boot param %s",
	791	+ ddebug_setup_string);
	792	+ else
	793	+ pr_info("ddebug initialized with string %s",
	794	+ ddebug_setup_string);
	795	+ }
	796	+
772	797	out_free:
773	798	if (ret) {
774	799	ddebug_remove_all_tables();