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

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>

14 files changed, 700 insertions, 7 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 2443f5bb4364..b429c84ceef2 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1713,6 +1713,11 @@ and is between 256 and 4096 characters. It is defined in the file
                         autoconfiguration.
                         Ranges are in pairs (memory base and size).
 
+        dynamic_printk
+                        Enables pr_debug()/dev_dbg() calls if
+                        CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled. These can also
+                        be switched on/off via <debugfs>/dynamic_printk/modules
+
         print-fatal-signals=
                         [KNL] debug: print fatal signals
                         print-fatal-signals=1: print segfault info to
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 7440a0dceddb..74c5faf26c05 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -268,7 +268,15 @@
         CPU_DISCARD(init.data)                                          \
         CPU_DISCARD(init.rodata)                                        \
         MEM_DISCARD(init.data)                                          \
-        MEM_DISCARD(init.rodata)
+        MEM_DISCARD(init.rodata)                                        \
+        /* implement dynamic printk debug */                            \
+        VMLINUX_SYMBOL(__start___verbose_strings) = .;                  \
+        *(__verbose_strings)                                            \
+        VMLINUX_SYMBOL(__stop___verbose_strings) = .;                   \
+        . = ALIGN(8);                                                   \
+        VMLINUX_SYMBOL(__start___verbose) = .;                          \
+        *(__verbose)                                                    \
+        VMLINUX_SYMBOL(__stop___verbose) = .;
 
 #define INIT_TEXT                                                       \
         *(.init.text)                                                   \
diff --git a/include/linux/device.h b/include/linux/device.h
index 60f6456691a6..fb034461b395 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -550,7 +550,11 @@ extern const char *dev_driver_string(const struct device *dev);
 #define dev_info(dev, format, arg...)           \
         dev_printk(KERN_INFO , dev , format , ## arg)
 
-#ifdef DEBUG
+#if defined(CONFIG_DYNAMIC_PRINTK_DEBUG)
+#define dev_dbg(dev, format, ...) do { \
+        dynamic_dev_dbg(dev, format, ##__VA_ARGS__); \
+        } while (0)
+#elif defined(DEBUG)
 #define dev_dbg(dev, format, arg...)            \
         dev_printk(KERN_DEBUG , dev , format , ## arg)
 #else
diff --git a/include/linux/dynamic_printk.h b/include/linux/dynamic_printk.h
new file mode 100644
index 000000000000..2d528d009074
--- /dev/null
+++ b/include/linux/dynamic_printk.h
@@ -0,0 +1,93 @@
+#ifndef _DYNAMIC_PRINTK_H
+#define _DYNAMIC_PRINTK_H
+
+#define DYNAMIC_DEBUG_HASH_BITS 6
+#define DEBUG_HASH_TABLE_SIZE (1 << DYNAMIC_DEBUG_HASH_BITS)
+
+#define TYPE_BOOLEAN 1
+
+#define DYNAMIC_ENABLED_ALL 0
+#define DYNAMIC_ENABLED_NONE 1
+#define DYNAMIC_ENABLED_SOME 2
+
+extern int dynamic_enabled;
+
+/* dynamic_printk_enabled, and dynamic_printk_enabled2 are bitmasks in which
+ * bit n is set to 1 if any modname hashes into the bucket n, 0 otherwise. They
+ * use independent hash functions, to reduce the chance of false positives.
+ */
+extern long long dynamic_printk_enabled;
+extern long long dynamic_printk_enabled2;
+
+struct mod_debug {
+        char *modname;
+        char *logical_modname;
+        char *flag_names;
+        int type;
+        int hash;
+        int hash2;
+} __attribute__((aligned(8)));
+
+int register_dynamic_debug_module(char *mod_name, int type, char *share_name,
+                                        char *flags, int hash, int hash2);
+
+#if defined(CONFIG_DYNAMIC_PRINTK_DEBUG)
+extern int unregister_dynamic_debug_module(char *mod_name);
+extern int __dynamic_dbg_enabled_helper(char *modname, int type,
+                                        int value, int hash);
+
+#define __dynamic_dbg_enabled(module, type, value, level, hash)  ({          \
+        int __ret = 0;                                                       \
+        if (unlikely((dynamic_printk_enabled & (1LL << DEBUG_HASH)) &&       \
+                        (dynamic_printk_enabled2 & (1LL << DEBUG_HASH2))))   \
+                        __ret = __dynamic_dbg_enabled_helper(module, type,   \
+                                                                value, hash);\
+        __ret; })
+
+#define dynamic_pr_debug(fmt, ...) do {                                     \
+        static char mod_name[]                                              \
+        __attribute__((section("__verbose_strings")))                       \
+         = KBUILD_MODNAME;                                                  \
+        static struct mod_debug descriptor                                  \
+        __used                                                              \
+        __attribute__((section("__verbose"), aligned(8))) =                 \
+        { mod_name, mod_name, NULL, TYPE_BOOLEAN, DEBUG_HASH, DEBUG_HASH2 };\
+        if (__dynamic_dbg_enabled(KBUILD_MODNAME, TYPE_BOOLEAN,             \
+                                                0, 0, DEBUG_HASH))          \
+                printk(KERN_DEBUG KBUILD_MODNAME ":" fmt,                   \
+                                ##__VA_ARGS__);                             \
+        } while (0)
+
+#define dynamic_dev_dbg(dev, format, ...) do {                              \
+        static char mod_name[]                                              \
+        __attribute__((section("__verbose_strings")))                       \
+         = KBUILD_MODNAME;                                                  \
+        static struct mod_debug descriptor                                  \
+        __used                                                              \
+        __attribute__((section("__verbose"), aligned(8))) =                 \
+        { mod_name, mod_name, NULL, TYPE_BOOLEAN, DEBUG_HASH, DEBUG_HASH2 };\
+        if (__dynamic_dbg_enabled(KBUILD_MODNAME, TYPE_BOOLEAN,             \
+                                                0, 0, DEBUG_HASH))          \
+                        dev_printk(KERN_DEBUG, dev,                         \
+                                        KBUILD_MODNAME ": " format,         \
+                                        ##__VA_ARGS__);                     \
+        } while (0)
+
+#else
+
+static inline int unregister_dynamic_debug_module(const char *mod_name)
+{
+        return 0;
+}
+static inline int __dynamic_dbg_enabled_helper(char *modname, int type,
+                                                int value, int hash)
+{
+        return 0;
+}
+
+#define __dynamic_dbg_enabled(module, type, value, level, hash)  ({ 0; })
+#define dynamic_pr_debug(fmt, ...)  do { } while (0)
+#define dynamic_dev_dbg(dev, format, ...)  do { } while (0)
+#endif
+
+#endif
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 75d81f157d2e..ededb6e83b41 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -16,6 +16,7 @@
 #include <linux/log2.h>
 #include <linux/typecheck.h>
 #include <linux/ratelimit.h>
+#include <linux/dynamic_printk.h>
 #include <asm/byteorder.h>
 #include <asm/bug.h>
 
@@ -303,8 +304,12 @@ static inline char *pack_hex_byte(char *buf, u8 byte)
 #define pr_info(fmt, arg...) \
         printk(KERN_INFO fmt, ##arg)
 
-#ifdef DEBUG
 /* If you are writing a driver, please use dev_dbg instead */
+#if defined(CONFIG_DYNAMIC_PRINTK_DEBUG)
+#define pr_debug(fmt, ...) do { \
+        dynamic_pr_debug(fmt, ##__VA_ARGS__); \
+        } while (0)
+#elif defined(DEBUG)
 #define pr_debug(fmt, arg...) \
         printk(KERN_DEBUG fmt, ##arg)
 #else
diff --git a/include/linux/module.h b/include/linux/module.h
index 68e09557c951..a41555cbe00a 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -345,7 +345,6 @@ struct module
         /* Reference counts */
         struct module_ref ref[NR_CPUS];
 #endif
-
 };
 #ifndef MODULE_ARCH_INIT
 #define MODULE_ARCH_INIT {}
diff --git a/kernel/module.c b/kernel/module.c
index d5fcd24e5aff..c52700667292 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -784,6 +784,7 @@ sys_delete_module(const char __user *name_user, unsigned int flags)
         mutex_lock(&module_mutex);
         /* Store the name of the last unloaded module for diagnostic purposes */
         strlcpy(last_unloaded_module, mod->name, sizeof(last_unloaded_module));
+        unregister_dynamic_debug_module(mod->name);
         free_module(mod);
 
  out:
@@ -1783,6 +1784,33 @@ static inline void add_kallsyms(struct module *mod,
 }
 #endif /* CONFIG_KALLSYMS */
 
+#ifdef CONFIG_DYNAMIC_PRINTK_DEBUG
+static void dynamic_printk_setup(Elf_Shdr *sechdrs, unsigned int verboseindex)
+{
+        struct mod_debug *debug_info;
+        unsigned long pos, end;
+        unsigned int num_verbose;
+
+        pos = sechdrs[verboseindex].sh_addr;
+        num_verbose = sechdrs[verboseindex].sh_size /
+                                sizeof(struct mod_debug);
+        end = pos + (num_verbose * sizeof(struct mod_debug));
+
+        for (; pos < end; pos += sizeof(struct mod_debug)) {
+                debug_info = (struct mod_debug *)pos;
+                register_dynamic_debug_module(debug_info->modname,
+                        debug_info->type, debug_info->logical_modname,
+                        debug_info->flag_names, debug_info->hash,
+                        debug_info->hash2);
+        }
+}
+#else
+static inline void dynamic_printk_setup(Elf_Shdr *sechdrs,
+                                        unsigned int verboseindex)
+{
+}
+#endif /* CONFIG_DYNAMIC_PRINTK_DEBUG */
+
 static void *module_alloc_update_bounds(unsigned long size)
 {
         void *ret = module_alloc(size);
@@ -1831,6 +1859,7 @@ static noinline struct module *load_module(void __user *umod,
 #endif
         unsigned int markersindex;
         unsigned int markersstringsindex;
+        unsigned int verboseindex;
         struct module *mod;
         long err = 0;
         void *percpu = NULL, *ptr = NULL; /* Stops spurious gcc warning */
@@ -2117,6 +2146,7 @@ static noinline struct module *load_module(void __user *umod,
         markersindex = find_sec(hdr, sechdrs, secstrings, "__markers");
         markersstringsindex = find_sec(hdr, sechdrs, secstrings,
                                         "__markers_strings");
+        verboseindex = find_sec(hdr, sechdrs, secstrings, "__verbose");
 
         /* Now do relocations. */
         for (i = 1; i < hdr->e_shnum; i++) {
@@ -2167,6 +2197,7 @@ static noinline struct module *load_module(void __user *umod,
                 marker_update_probe_range(mod->markers,
                         mod->markers + mod->num_markers);
 #endif
+        dynamic_printk_setup(sechdrs, verboseindex);
         err = module_finalize(hdr, sechdrs, mod);
         if (err < 0)
                 goto cleanup;
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index aa81d2848448..31d784dd80d0 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -807,6 +807,61 @@ menuconfig BUILD_DOCSRC
 
           Say N if you are unsure.
 
+config DYNAMIC_PRINTK_DEBUG
+        bool "Enable dynamic printk() call support"
+        default n
+        depends on PRINTK
+        select PRINTK_DEBUG
+        help
+
+          Compiles debug level messages into the kernel, which would not
+          otherwise be available at runtime. These messages can then be
+          enabled/disabled on a per module basis. This mechanism implicitly
+          enables all pr_debug() and dev_dbg() calls. The impact of this
+          compile option is a larger kernel text size of about 2%.
+
+          Usage:
+
+          Dynamic debugging is controlled by the debugfs file,
+          dynamic_printk/modules. This file contains a list of the modules that
+          can be enabled. The format of the file is the module name, followed
+          by a set of flags that can be enabled. The first flag is always the
+          'enabled' flag. For example:
+
+                <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
+
+          From a live system:
+
+                snd_hda_intel enabled=0
+                fixup enabled=0
+                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.
+
 source "samples/Kconfig"
 
 source "lib/Kconfig.kgdb"
diff --git a/lib/Makefile b/lib/Makefile
index 44001af76a7d..16feaab057b2 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -81,6 +81,8 @@ obj-$(CONFIG_HAVE_LMB) += lmb.o
 
 obj-$(CONFIG_HAVE_ARCH_TRACEHOOK) += syscall.o
 
+obj-$(CONFIG_DYNAMIC_PRINTK_DEBUG) += dynamic_printk.o
+
 hostprogs-y     := gen_crc32table
 clean-files     := crc32table.h
 
diff --git a/lib/dynamic_printk.c b/lib/dynamic_printk.c
new file mode 100644
index 000000000000..d640f87bdc9e
--- /dev/null
+++ b/lib/dynamic_printk.c
@@ -0,0 +1,418 @@
+/*
+ * lib/dynamic_printk.c
+ *
+ * make pr_debug()/dev_dbg() calls runtime configurable based upon their
+ * their source module.
+ *
+ * Copyright (C) 2008 Red Hat, Inc., Jason Baron <jbaron@redhat.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/uaccess.h>
+#include <linux/seq_file.h>
+#include <linux/debugfs.h>
+#include <linux/fs.h>
+
+extern struct mod_debug __start___verbose[];
+extern struct mod_debug __stop___verbose[];
+
+struct debug_name {
+        struct hlist_node hlist;
+        struct hlist_node hlist2;
+        int hash1;
+        int hash2;
+        char *name;
+        int enable;
+        int type;
+};
+
+static int nr_entries;
+static int num_enabled;
+int dynamic_enabled = DYNAMIC_ENABLED_NONE;
+static struct hlist_head module_table[DEBUG_HASH_TABLE_SIZE] =
+        { [0 ... DEBUG_HASH_TABLE_SIZE-1] = HLIST_HEAD_INIT };
+static struct hlist_head module_table2[DEBUG_HASH_TABLE_SIZE] =
+        { [0 ... DEBUG_HASH_TABLE_SIZE-1] = HLIST_HEAD_INIT };
+static DECLARE_MUTEX(debug_list_mutex);
+
+/* dynamic_printk_enabled, and dynamic_printk_enabled2 are bitmasks in which
+ * bit n is set to 1 if any modname hashes into the bucket n, 0 otherwise. They
+ * use independent hash functions, to reduce the chance of false positives.
+ */
+long long dynamic_printk_enabled;
+EXPORT_SYMBOL_GPL(dynamic_printk_enabled);
+long long dynamic_printk_enabled2;
+EXPORT_SYMBOL_GPL(dynamic_printk_enabled2);
+
+/* returns the debug module pointer. */
+static struct debug_name *find_debug_module(char *module_name)
+{
+        int i;
+        struct hlist_head *head;
+        struct hlist_node *node;
+        struct debug_name *element;
+
+        element = NULL;
+        for (i = 0; i < DEBUG_HASH_TABLE_SIZE; i++) {
+                head = &module_table[i];
+                hlist_for_each_entry_rcu(element, node, head, hlist)
+                        if (!strcmp(element->name, module_name))
+                                return element;
+        }
+        return NULL;
+}
+
+/* returns the debug module pointer. */
+static struct debug_name *find_debug_module_hash(char *module_name, int hash)
+{
+        struct hlist_head *head;
+        struct hlist_node *node;
+        struct debug_name *element;
+
+        element = NULL;
+        head = &module_table[hash];
+        hlist_for_each_entry_rcu(element, node, head, hlist)
+                if (!strcmp(element->name, module_name))
+                        return element;
+        return NULL;
+}
+
+/* caller must hold mutex*/
+static int __add_debug_module(char *mod_name, int hash, int hash2)
+{
+        struct debug_name *new;
+        char *module_name;
+        int ret = 0;
+
+        if (find_debug_module(mod_name)) {
+                ret = -EINVAL;
+                goto out;
+        }
+        module_name = kmalloc(strlen(mod_name) + 1, GFP_KERNEL);
+        if (!module_name) {
+                ret = -ENOMEM;
+                goto out;
+        }
+        module_name = strcpy(module_name, mod_name);
+        module_name[strlen(mod_name)] = '\0';
+        new = kzalloc(sizeof(struct debug_name), GFP_KERNEL);
+        if (!new) {
+                kfree(module_name);
+                ret = -ENOMEM;
+                goto out;
+        }
+        INIT_HLIST_NODE(&new->hlist);
+        INIT_HLIST_NODE(&new->hlist2);
+        new->name = module_name;
+        new->hash1 = hash;
+        new->hash2 = hash2;
+        hlist_add_head_rcu(&new->hlist, &module_table[hash]);
+        hlist_add_head_rcu(&new->hlist2, &module_table2[hash2]);
+        nr_entries++;
+out:
+        return ret;
+}
+
+int unregister_dynamic_debug_module(char *mod_name)
+{
+        struct debug_name *element;
+        int ret = 0;
+
+        down(&debug_list_mutex);
+        element = find_debug_module(mod_name);
+        if (!element) {
+                ret = -EINVAL;
+                goto out;
+        }
+        hlist_del_rcu(&element->hlist);
+        hlist_del_rcu(&element->hlist2);
+        synchronize_rcu();
+        kfree(element->name);
+        if (element->enable)
+                num_enabled--;
+        kfree(element);
+        nr_entries--;
+out:
+        up(&debug_list_mutex);
+        return 0;
+}
+EXPORT_SYMBOL_GPL(unregister_dynamic_debug_module);
+
+int register_dynamic_debug_module(char *mod_name, int type, char *share_name,
+                                        char *flags, int hash, int hash2)
+{
+        struct debug_name *elem;
+        int ret = 0;
+
+        down(&debug_list_mutex);
+        elem = find_debug_module(mod_name);
+        if (!elem) {
+                if (__add_debug_module(mod_name, hash, hash2))
+                        goto out;
+                elem = find_debug_module(mod_name);
+                if (dynamic_enabled == DYNAMIC_ENABLED_ALL &&
+                                !strcmp(mod_name, share_name)) {
+                        elem->enable = true;
+                        num_enabled++;
+                }
+        }
+        elem->type |= type;
+out:
+        up(&debug_list_mutex);
+        return ret;
+}
+EXPORT_SYMBOL_GPL(register_dynamic_debug_module);
+
+int __dynamic_dbg_enabled_helper(char *mod_name, int type, int value, int hash)
+{
+        struct debug_name *elem;
+        int ret = 0;
+
+        if (dynamic_enabled == DYNAMIC_ENABLED_ALL)
+                return 1;
+        rcu_read_lock();
+        elem = find_debug_module_hash(mod_name, hash);
+        if (elem && elem->enable)
+                ret = 1;
+        rcu_read_unlock();
+        return ret;
+}
+EXPORT_SYMBOL_GPL(__dynamic_dbg_enabled_helper);
+
+static void set_all(bool enable)
+{
+        struct debug_name *e;
+        struct hlist_node *node;
+        int i;
+        long long enable_mask;
+
+        for (i = 0; i < DEBUG_HASH_TABLE_SIZE; i++) {
+                if (module_table[i].first != NULL) {
+                        hlist_for_each_entry(e, node, &module_table[i], hlist) {
+                                e->enable = enable;
+                        }
+                }
+        }
+        if (enable)
+                enable_mask = ULLONG_MAX;
+        else
+                enable_mask = 0;
+        dynamic_printk_enabled = enable_mask;
+        dynamic_printk_enabled2 = enable_mask;
+}
+
+static int disabled_hash(int i, bool first_table)
+{
+        struct debug_name *e;
+        struct hlist_node *node;
+
+        if (first_table) {
+                hlist_for_each_entry(e, node, &module_table[i], hlist) {
+                        if (e->enable)
+                                return 0;
+                }
+        } else {
+                hlist_for_each_entry(e, node, &module_table2[i], hlist2) {
+                        if (e->enable)
+                                return 0;
+                }
+        }
+        return 1;
+}
+
+static ssize_t pr_debug_write(struct file *file, const char __user *buf,
+                                size_t length, loff_t *ppos)
+{
+        char *buffer, *s, *value_str, *setting_str;
+        int err, value;
+        struct debug_name *elem = NULL;
+        int all = 0;
+
+        if (length > PAGE_SIZE || length < 0)
+                return -EINVAL;
+
+        buffer = (char *)__get_free_page(GFP_KERNEL);
+        if (!buffer)
+                return -ENOMEM;
+
+        err = -EFAULT;
+        if (copy_from_user(buffer, buf, length))
+                goto out;
+
+        err = -EINVAL;
+        if (length < PAGE_SIZE)
+                buffer[length] = '\0';
+        else if (buffer[PAGE_SIZE-1])
+                goto out;
+
+        err = -EINVAL;
+        down(&debug_list_mutex);
+
+        if (strncmp("set", buffer, 3))
+                goto out_up;
+        s = buffer + 3;
+        setting_str = strsep(&s, "=");
+        if (s == NULL)
+                goto out_up;
+        setting_str = strstrip(setting_str);
+        value_str = strsep(&s, " ");
+        if (s == NULL)
+                goto out_up;
+        s = strstrip(s);
+        if (!strncmp(s, "all", 3))
+                all = 1;
+        else
+                elem = find_debug_module(s);
+        if (!strncmp(setting_str, "enable", 6)) {
+                value = !!simple_strtol(value_str, NULL, 10);
+                if (all) {
+                        if (value) {
+                                set_all(true);
+                                num_enabled = nr_entries;
+                                dynamic_enabled = DYNAMIC_ENABLED_ALL;
+                        } else {
+                                set_all(false);
+                                num_enabled = 0;
+                                dynamic_enabled = DYNAMIC_ENABLED_NONE;
+                        }
+                        err = 0;
+                } else {
+                        if (elem) {
+                                if (value && (elem->enable == 0)) {
+                                        dynamic_printk_enabled |=
+                                                        (1LL << elem->hash1);
+                                        dynamic_printk_enabled2 |=
+                                                        (1LL << elem->hash2);
+                                        elem->enable = 1;
+                                        num_enabled++;
+                                        dynamic_enabled = DYNAMIC_ENABLED_SOME;
+                                        err = 0;
+                                        printk(KERN_DEBUG
+                                               "debugging enabled for module %s",
+                                               elem->name);
+                                } else if (!value && (elem->enable == 1)) {
+                                        elem->enable = 0;
+                                        num_enabled--;
+                                        if (disabled_hash(elem->hash1, true))
+                                                dynamic_printk_enabled &=
+                                                        ~(1LL << elem->hash1);
+                                        if (disabled_hash(elem->hash2, false))
+                                                dynamic_printk_enabled2 &=
+                                                        ~(1LL << elem->hash2);
+                                        if (num_enabled)
+                                                dynamic_enabled =
+                                                        DYNAMIC_ENABLED_SOME;
+                                        else
+                                                dynamic_enabled =
+                                                        DYNAMIC_ENABLED_NONE;
+                                        err = 0;
+                                        printk(KERN_DEBUG
+                                               "debugging disabled for module "
+                                               "%s", elem->name);
+                                }
+                        }
+                }
+        }
+        if (!err)
+                err = length;
+out_up:
+        up(&debug_list_mutex);
+out:
+        free_page((unsigned long)buffer);
+        return err;
+}
+
+static void *pr_debug_seq_start(struct seq_file *f, loff_t *pos)
+{
+        return (*pos < DEBUG_HASH_TABLE_SIZE) ? pos : NULL;
+}
+
+static void *pr_debug_seq_next(struct seq_file *s, void *v, loff_t *pos)
+{
+        (*pos)++;
+        if (*pos >= DEBUG_HASH_TABLE_SIZE)
+                return NULL;
+        return pos;
+}
+
+static void pr_debug_seq_stop(struct seq_file *s, void *v)
+{
+        /* Nothing to do */
+}
+
+static int pr_debug_seq_show(struct seq_file *s, void *v)
+{
+        struct hlist_head *head;
+        struct hlist_node *node;
+        struct debug_name *elem;
+        unsigned int i = *(loff_t *) v;
+
+        rcu_read_lock();
+        head = &module_table[i];
+        hlist_for_each_entry_rcu(elem, node, head, hlist) {
+                seq_printf(s, "%s enabled=%d", elem->name, elem->enable);
+                seq_printf(s, "\n");
+        }
+        rcu_read_unlock();
+        return 0;
+}
+
+static struct seq_operations pr_debug_seq_ops = {
+        .start = pr_debug_seq_start,
+        .next  = pr_debug_seq_next,
+        .stop  = pr_debug_seq_stop,
+        .show  = pr_debug_seq_show
+};
+
+static int pr_debug_open(struct inode *inode, struct file *filp)
+{
+        return seq_open(filp, &pr_debug_seq_ops);
+}
+
+static const struct file_operations pr_debug_operations = {
+        .open           = pr_debug_open,
+        .read           = seq_read,
+        .write          = pr_debug_write,
+        .llseek         = seq_lseek,
+        .release        = seq_release,
+};
+
+static int __init dynamic_printk_init(void)
+{
+        struct dentry *dir, *file;
+        struct mod_debug *iter;
+        unsigned long value;
+
+        dir = debugfs_create_dir("dynamic_printk", NULL);
+        if (!dir)
+                return -ENOMEM;
+        file = debugfs_create_file("modules", 0644, dir, NULL,
+                                        &pr_debug_operations);
+        if (!file) {
+                debugfs_remove(dir);
+                return -ENOMEM;
+        }
+        for (value = (unsigned long)__start___verbose;
+                value < (unsigned long)__stop___verbose;
+                value += sizeof(struct mod_debug)) {
+                        iter = (struct mod_debug *)value;
+                        register_dynamic_debug_module(iter->modname,
+                                iter->type,
+                                iter->logical_modname,
+                                iter->flag_names, iter->hash, iter->hash2);
+        }
+        return 0;
+}
+module_init(dynamic_printk_init);
+/* may want to move this earlier so we can get traces as early as possible */
+
+static int __init dynamic_printk_setup(char *str)
+{
+        if (str)
+                return -ENOENT;
+        set_all(true);
+        return 0;
+}
+/* Use early_param(), so we can get debug output as early as possible */
+early_param("dynamic_printk", dynamic_printk_setup);
diff --git a/net/netfilter/nf_conntrack_pptp.c b/net/netfilter/nf_conntrack_pptp.c
index 373e51e91ce5..1bc3001d1827 100644
--- a/net/netfilter/nf_conntrack_pptp.c
+++ b/net/netfilter/nf_conntrack_pptp.c
@@ -65,7 +65,7 @@ void
                              struct nf_conntrack_expect *exp) __read_mostly;
 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_expectfn);
 
-#ifdef DEBUG
+#if defined(DEBUG) || defined(CONFIG_DYNAMIC_PRINTK_DEBUG)
 /* PptpControlMessageType names */
 const char *const pptp_msg_name[] = {
         "UNKNOWN_MESSAGE",
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index ea48b82a3707..b4ca38a21158 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -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)
diff --git a/scripts/basic/Makefile b/scripts/basic/Makefile
index 4c324a1f1e0e..09559951df12 100644
--- a/scripts/basic/Makefile
+++ b/scripts/basic/Makefile
@@ -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
diff --git a/scripts/basic/hash.c b/scripts/basic/hash.c
new file mode 100644
index 000000000000..3299ad7fc8c0
--- /dev/null
+++ b/scripts/basic/hash.c
@@ -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);
+}
+