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>
diff --git a/lib/dynamic_printk.c b/lib/dynamic_printk.c
new file mode 100644
index 0000000..d640f87
--- /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);