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driver core: basic infrastructure for per-module dynamic debug messages

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Base infrastructure to enable per-module debug messages.

I've introduced CONFIG_DYNAMIC_PRINTK_DEBUG, which when enabled centralizes
control of debugging statements on a per-module basis in one /proc file,
currently, <debugfs>/dynamic_printk/modules. When, CONFIG_DYNAMIC_PRINTK_DEBUG,
is not set, debugging statements can still be enabled as before, often by
defining 'DEBUG' for the proper compilation unit. Thus, this patch set has no
affect when CONFIG_DYNAMIC_PRINTK_DEBUG is not set.

The infrastructure currently ties into all pr_debug() and dev_dbg() calls. That
is, if CONFIG_DYNAMIC_PRINTK_DEBUG is set, all pr_debug() and dev_dbg() calls
can be dynamically enabled/disabled on a per-module basis.

Future plans include extending this functionality to subsystems, that define 
their own debug levels and flags.

Usage:

Dynamic debugging is controlled by the debugfs file, 
<debugfs>/dynamic_printk/modules. This file contains a list of the modules that
can be enabled. The format of the file is as follows:

	<module_name> <enabled=0/1>
		.
		.
		.

	<module_name> : Name of the module in which the debug call resides
	<enabled=0/1> : whether the messages are enabled or not

For example:

	snd_hda_intel enabled=0
	fixup enabled=1
	driver enabled=0

Enable a module:

	$echo "set enabled=1 <module_name>" > dynamic_printk/modules

Disable a module:

	$echo "set enabled=0 <module_name>" > dynamic_printk/modules

Enable all modules:

	$echo "set enabled=1 all" > dynamic_printk/modules

Disable all modules:

	$echo "set enabled=0 all" > dynamic_printk/modules

Finally, passing "dynamic_printk" at the command line enables
debugging for all modules. This mode can be turned off via the above
disable command.

[gkh: minor cleanups and tweaks to make the build work quietly]

Signed-off-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Jason Baron
2008-08-12 16:46:19 -04:00
committed by Greg Kroah-Hartman
parent 33376c1c04
commit 346e15beb5
14 changed files with 700 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

11
scripts/Makefile.lib
View File

@@ -96,6 +96,14 @@ basename_flags = -D"KBUILD_BASENAME=KBUILD_STR($(call name-fix,$(basetarget)))"
modname_flags = $(if $(filter 1,$(words $(modname))),\
-D"KBUILD_MODNAME=KBUILD_STR($(call name-fix,$(modname)))")
#hash values
ifdef CONFIG_DYNAMIC_PRINTK_DEBUG
debug_flags = -D"DEBUG_HASH=$(shell ./scripts/basic/hash djb2 $(@D)$(modname))"\
-D"DEBUG_HASH2=$(shell ./scripts/basic/hash r5 $(@D)$(modname))"
else
debug_flags =
endif
orig_c_flags = $(KBUILD_CFLAGS) $(ccflags-y) $(CFLAGS_$(basetarget).o)
_c_flags = $(filter-out $(CFLAGS_REMOVE_$(basetarget).o), $(orig_c_flags))
_a_flags = $(KBUILD_AFLAGS) $(asflags-y) $(AFLAGS_$(basetarget).o)
@@ -121,7 +129,8 @@ endif
c_flags = -Wp,-MD,$(depfile) $(NOSTDINC_FLAGS) $(KBUILD_CPPFLAGS) \
$(__c_flags) $(modkern_cflags) \
-D"KBUILD_STR(s)=\#s" $(basename_flags) $(modname_flags)
-D"KBUILD_STR(s)=\#s" $(basename_flags) $(modname_flags) \
$(debug_flags)
a_flags = -Wp,-MD,$(depfile) $(NOSTDINC_FLAGS) $(KBUILD_CPPFLAGS) \
$(__a_flags) $(modkern_aflags)

2
scripts/basic/Makefile
View File

@@ -9,7 +9,7 @@
# fixdep: Used to generate dependency information during build process
# docproc: Used in Documentation/DocBook
hostprogs-y := fixdep docproc
hostprogs-y := fixdep docproc hash
always := $(hostprogs-y)
# fixdep is needed to compile other host programs

64
scripts/basic/hash.c Normal file
View File

@@ -0,0 +1,64 @@
/*
* Copyright (C) 2008 Red Hat, Inc., Jason Baron <jbaron@redhat.com>
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define DYNAMIC_DEBUG_HASH_BITS 6
static const char *program;
static void usage(void)
{
printf("Usage: %s <djb2|r5> <modname>\n", program);
exit(1);
}
/* djb2 hashing algorithm by Dan Bernstein. From:
* http://www.cse.yorku.ca/~oz/hash.html
*/
unsigned int djb2_hash(char *str)
{
unsigned long hash = 5381;
int c;
c = *str;
while (c) {
hash = ((hash << 5) + hash) + c;
c = *++str;
}
return (unsigned int)(hash & ((1 << DYNAMIC_DEBUG_HASH_BITS) - 1));
}
unsigned int r5_hash(char *str)
{
unsigned long hash = 0;
int c;
c = *str;
while (c) {
hash = (hash + (c << 4) + (c >> 4)) * 11;
c = *++str;
}
return (unsigned int)(hash & ((1 << DYNAMIC_DEBUG_HASH_BITS) - 1));
}
int main(int argc, char *argv[])
{
program = argv[0];
if (argc != 3)
usage();
if (!strcmp(argv[1], "djb2"))
printf("%d\n", djb2_hash(argv[2]));
else if (!strcmp(argv[1], "r5"))
printf("%d\n", r5_hash(argv[2]));
else
usage();
exit(0);
}