dynamic debug: combine dprintk and dynamic printk

This patch combines Greg Bank's dprintk() work with the existing dynamic
printk patchset, we are now calling it 'dynamic debug'.

The new feature of this patchset is a richer /debugfs control file interface,
(an example output from my system is at the bottom), which allows fined grained
control over the the debug output. The output can be controlled by function,
file, module, format string, and line number.

for example, enabled all debug messages in module 'nf_conntrack':

echo -n 'module nf_conntrack +p' > /mnt/debugfs/dynamic_debug/control

to disable them:

echo -n 'module nf_conntrack -p' > /mnt/debugfs/dynamic_debug/control

A further explanation can be found in the documentation patch.

Signed-off-by: Greg Banks <gnb@sgi.com>
Signed-off-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 756 insertions, 0 deletions

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
new file mode 100644
index 0000000..9e123ae
--- /dev/null
+++ b/lib/dynamic_debug.c
@@ -0,0 +1,756 @@
+/*
+ * lib/dynamic_debug.c
+ *
+ * make pr_debug()/dev_dbg() calls runtime configurable based upon their
+ * source module.
+ *
+ * Copyright (C) 2008 Jason Baron <jbaron@redhat.com>
+ * By Greg Banks <gnb@melbourne.sgi.com>
+ * Copyright (c) 2008 Silicon Graphics Inc.  All Rights Reserved.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/kallsyms.h>
+#include <linux/version.h>
+#include <linux/types.h>
+#include <linux/mutex.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/list.h>
+#include <linux/sysctl.h>
+#include <linux/ctype.h>
+#include <linux/uaccess.h>
+#include <linux/dynamic_debug.h>
+#include <linux/debugfs.h>
+
+extern struct _ddebug __start___verbose[];
+extern struct _ddebug __stop___verbose[];
+
+/* dynamic_debug_enabled, and dynamic_debug_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_debug_enabled;
+EXPORT_SYMBOL_GPL(dynamic_debug_enabled);
+long long dynamic_debug_enabled2;
+EXPORT_SYMBOL_GPL(dynamic_debug_enabled2);
+
+struct ddebug_table {
+	struct list_head link;
+	char *mod_name;
+	unsigned int num_ddebugs;
+	unsigned int num_enabled;
+	struct _ddebug *ddebugs;
+};
+
+struct ddebug_query {
+	const char *filename;
+	const char *module;
+	const char *function;
+	const char *format;
+	unsigned int first_lineno, last_lineno;
+};
+
+struct ddebug_iter {
+	struct ddebug_table *table;
+	unsigned int idx;
+};
+
+static DEFINE_MUTEX(ddebug_lock);
+static LIST_HEAD(ddebug_tables);
+static int verbose = 0;
+
+/* Return the last part of a pathname */
+static inline const char *basename(const char *path)
+{
+	const char *tail = strrchr(path, '/');
+	return tail ? tail+1 : path;
+}
+
+/* format a string into buf[] which describes the _ddebug's flags */
+static char *ddebug_describe_flags(struct _ddebug *dp, char *buf,
+				    size_t maxlen)
+{
+	char *p = buf;
+
+	BUG_ON(maxlen < 4);
+	if (dp->flags & _DPRINTK_FLAGS_PRINT)
+		*p++ = 'p';
+	if (p == buf)
+		*p++ = '-';
+	*p = '\0';
+
+	return buf;
+}
+
+/*
+ * must be called with ddebug_lock held
+ */
+
+static int disabled_hash(char hash, bool first_table)
+{
+	struct ddebug_table *dt;
+	char table_hash_value;
+
+	list_for_each_entry(dt, &ddebug_tables, link) {
+		if (first_table)
+			table_hash_value = dt->ddebugs->primary_hash;
+		else
+			table_hash_value = dt->ddebugs->secondary_hash;
+		if (dt->num_enabled && (hash == table_hash_value))
+			return 0;
+	}
+	return 1;
+}
+
+/*
+ * Search the tables for _ddebug's which match the given
+ * `query' and apply the `flags' and `mask' to them.  Tells
+ * the user which ddebug's were changed, or whether none
+ * were matched.
+ */
+static void ddebug_change(const struct ddebug_query *query,
+			   unsigned int flags, unsigned int mask)
+{
+	int i;
+	struct ddebug_table *dt;
+	unsigned int newflags;
+	unsigned int nfound = 0;
+	char flagbuf[8];
+
+	/* search for matching ddebugs */
+	mutex_lock(&ddebug_lock);
+	list_for_each_entry(dt, &ddebug_tables, link) {
+
+		/* match against the module name */
+		if (query->module != NULL &&
+		    strcmp(query->module, dt->mod_name))
+			continue;
+
+		for (i = 0 ; i < dt->num_ddebugs ; i++) {
+			struct _ddebug *dp = &dt->ddebugs[i];
+
+			/* match against the source filename */
+			if (query->filename != NULL &&
+			    strcmp(query->filename, dp->filename) &&
+			    strcmp(query->filename, basename(dp->filename)))
+				continue;
+
+			/* match against the function */
+			if (query->function != NULL &&
+			    strcmp(query->function, dp->function))
+				continue;
+
+			/* match against the format */
+			if (query->format != NULL &&
+			    strstr(dp->format, query->format) == NULL)
+				continue;
+
+			/* match against the line number range */
+			if (query->first_lineno &&
+			    dp->lineno < query->first_lineno)
+				continue;
+			if (query->last_lineno &&
+			    dp->lineno > query->last_lineno)
+				continue;
+
+			nfound++;
+
+			newflags = (dp->flags & mask) | flags;
+			if (newflags == dp->flags)
+				continue;
+
+			if (!newflags)
+				dt->num_enabled--;
+			else if (!dp-flags)
+				dt->num_enabled++;
+			dp->flags = newflags;
+			if (newflags) {
+				dynamic_debug_enabled |=
+						(1LL << dp->primary_hash);
+				dynamic_debug_enabled2 |=
+						(1LL << dp->secondary_hash);
+			} else {
+				if (disabled_hash(dp->primary_hash, true))
+					dynamic_debug_enabled &=
+						~(1LL << dp->primary_hash);
+				if (disabled_hash(dp->secondary_hash, false))
+					dynamic_debug_enabled2 &=
+						~(1LL << dp->secondary_hash);
+			}
+			if (verbose)
+				printk(KERN_INFO
+					"ddebug: changed %s:%d [%s]%s %s\n",
+					dp->filename, dp->lineno,
+					dt->mod_name, dp->function,
+					ddebug_describe_flags(dp, flagbuf,
+							sizeof(flagbuf)));
+		}
+	}
+	mutex_unlock(&ddebug_lock);
+
+	if (!nfound && verbose)
+		printk(KERN_INFO "ddebug: no matches for query\n");
+}
+
+/*
+ * Wrapper around strsep() to collapse the multiple empty tokens
+ * that it returns when fed sequences of separator characters.
+ * Now, if we had strtok_r()...
+ */
+static inline char *nearly_strtok_r(char **p, const char *sep)
+{
+	char *r;
+
+	while ((r = strsep(p, sep)) != NULL && *r == '\0')
+		;
+	return r;
+}
+
+/*
+ * Split the buffer `buf' into space-separated words.
+ * Return the number of such words or <0 on error.
+ */
+static int ddebug_tokenize(char *buf, char *words[], int maxwords)
+{
+	int nwords = 0;
+
+	while (nwords < maxwords &&
+	       (words[nwords] = nearly_strtok_r(&buf, " \t\r\n")) != NULL)
+		nwords++;
+	if (buf)
+		return -EINVAL;	/* ran out of words[] before bytes */
+
+	if (verbose) {
+		int i;
+		printk(KERN_INFO "%s: split into words:", __func__);
+		for (i = 0 ; i < nwords ; i++)
+			printk(" \"%s\"", words[i]);
+		printk("\n");
+	}
+
+	return nwords;
+}
+
+/*
+ * Parse a single line number.  Note that the empty string ""
+ * is treated as a special case and converted to zero, which
+ * is later treated as a "don't care" value.
+ */
+static inline int parse_lineno(const char *str, unsigned int *val)
+{
+	char *end = NULL;
+	BUG_ON(str == NULL);
+	if (*str == '\0') {
+		*val = 0;
+		return 0;
+	}
+	*val = simple_strtoul(str, &end, 10);
+	return end == NULL || end == str || *end != '\0' ? -EINVAL : 0;
+}
+
+/*
+ * Undo octal escaping in a string, inplace.  This is useful to
+ * allow the user to express a query which matches a format
+ * containing embedded spaces.
+ */
+#define isodigit(c)		((c) >= '0' && (c) <= '7')
+static char *unescape(char *str)
+{
+	char *in = str;
+	char *out = str;
+
+	while (*in) {
+		if (*in == '\\') {
+			if (in[1] == '\\') {
+				*out++ = '\\';
+				in += 2;
+				continue;
+			} else if (in[1] == 't') {
+				*out++ = '\t';
+				in += 2;
+				continue;
+			} else if (in[1] == 'n') {
+				*out++ = '\n';
+				in += 2;
+				continue;
+			} else if (isodigit(in[1]) &&
+			         isodigit(in[2]) &&
+			         isodigit(in[3])) {
+				*out++ = ((in[1] - '0')<<6) |
+				          ((in[2] - '0')<<3) |
+				          (in[3] - '0');
+				in += 4;
+				continue;
+			}
+		}
+		*out++ = *in++;
+	}
+	*out = '\0';
+
+	return str;
+}
+
+/*
+ * Parse words[] as a ddebug query specification, which is a series
+ * of (keyword, value) pairs chosen from these possibilities:
+ *
+ * func <function-name>
+ * file <full-pathname>
+ * file <base-filename>
+ * module <module-name>
+ * format <escaped-string-to-find-in-format>
+ * line <lineno>
+ * line <first-lineno>-<last-lineno> // where either may be empty
+ */
+static int ddebug_parse_query(char *words[], int nwords,
+			       struct ddebug_query *query)
+{
+	unsigned int i;
+
+	/* check we have an even number of words */
+	if (nwords % 2 != 0)
+		return -EINVAL;
+	memset(query, 0, sizeof(*query));
+
+	for (i = 0 ; i < nwords ; i += 2) {
+		if (!strcmp(words[i], "func"))
+			query->function = words[i+1];
+		else if (!strcmp(words[i], "file"))
+			query->filename = words[i+1];
+		else if (!strcmp(words[i], "module"))
+			query->module = words[i+1];
+		else if (!strcmp(words[i], "format"))
+			query->format = unescape(words[i+1]);
+		else if (!strcmp(words[i], "line")) {
+			char *first = words[i+1];
+			char *last = strchr(first, '-');
+			if (last)
+				*last++ = '\0';
+			if (parse_lineno(first, &query->first_lineno) < 0)
+				return -EINVAL;
+			if (last != NULL) {
+				/* range <first>-<last> */
+				if (parse_lineno(last, &query->last_lineno) < 0)
+					return -EINVAL;
+			} else {
+				query->last_lineno = query->first_lineno;
+			}
+		} else {
+			if (verbose)
+				printk(KERN_ERR "%s: unknown keyword \"%s\"\n",
+					__func__, words[i]);
+			return -EINVAL;
+		}
+	}
+
+	if (verbose)
+		printk(KERN_INFO "%s: q->function=\"%s\" q->filename=\"%s\" "
+		       "q->module=\"%s\" q->format=\"%s\" q->lineno=%u-%u\n",
+			__func__, query->function, query->filename,
+			query->module, query->format, query->first_lineno,
+			query->last_lineno);
+
+	return 0;
+}
+
+/*
+ * Parse `str' as a flags specification, format [-+=][p]+.
+ * Sets up *maskp and *flagsp to be used when changing the
+ * flags fields of matched _ddebug's.  Returns 0 on success
+ * or <0 on error.
+ */
+static int ddebug_parse_flags(const char *str, unsigned int *flagsp,
+			       unsigned int *maskp)
+{
+	unsigned flags = 0;
+	int op = '=';
+
+	switch (*str) {
+	case '+':
+	case '-':
+	case '=':
+		op = *str++;
+		break;
+	default:
+		return -EINVAL;
+	}
+	if (verbose)
+		printk(KERN_INFO "%s: op='%c'\n", __func__, op);
+
+	for ( ; *str ; ++str) {
+		switch (*str) {
+		case 'p':
+			flags |= _DPRINTK_FLAGS_PRINT;
+			break;
+		default:
+			return -EINVAL;
+		}
+	}
+	if (flags == 0)
+		return -EINVAL;
+	if (verbose)
+		printk(KERN_INFO "%s: flags=0x%x\n", __func__, flags);
+
+	/* calculate final *flagsp, *maskp according to mask and op */
+	switch (op) {
+	case '=':
+		*maskp = 0;
+		*flagsp = flags;
+		break;
+	case '+':
+		*maskp = ~0U;
+		*flagsp = flags;
+		break;
+	case '-':
+		*maskp = ~flags;
+		*flagsp = 0;
+		break;
+	}
+	if (verbose)
+		printk(KERN_INFO "%s: *flagsp=0x%x *maskp=0x%x\n",
+			__func__, *flagsp, *maskp);
+	return 0;
+}
+
+/*
+ * File_ops->write method for <debugfs>/dynamic_debug/conrol.  Gathers the
+ * command text from userspace, parses and executes it.
+ */
+static ssize_t ddebug_proc_write(struct file *file, const char __user *ubuf,
+				  size_t len, loff_t *offp)
+{
+	unsigned int flags = 0, mask = 0;
+	struct ddebug_query query;
+#define MAXWORDS 9
+	int nwords;
+	char *words[MAXWORDS];
+	char tmpbuf[256];
+
+	if (len == 0)
+		return 0;
+	/* we don't check *offp -- multiple writes() are allowed */
+	if (len > sizeof(tmpbuf)-1)
+		return -E2BIG;
+	if (copy_from_user(tmpbuf, ubuf, len))
+		return -EFAULT;
+	tmpbuf[len] = '\0';
+	if (verbose)
+		printk(KERN_INFO "%s: read %d bytes from userspace\n",
+			__func__, (int)len);
+
+	nwords = ddebug_tokenize(tmpbuf, words, MAXWORDS);
+	if (nwords < 0)
+		return -EINVAL;
+	if (ddebug_parse_query(words, nwords-1, &query))
+		return -EINVAL;
+	if (ddebug_parse_flags(words[nwords-1], &flags, &mask))
+		return -EINVAL;
+
+	/* actually go and implement the change */
+	ddebug_change(&query, flags, mask);
+
+	*offp += len;
+	return len;
+}
+
+/*
+ * Set the iterator to point to the first _ddebug object
+ * and return a pointer to that first object.  Returns
+ * NULL if there are no _ddebugs at all.
+ */
+static struct _ddebug *ddebug_iter_first(struct ddebug_iter *iter)
+{
+	if (list_empty(&ddebug_tables)) {
+		iter->table = NULL;
+		iter->idx = 0;
+		return NULL;
+	}
+	iter->table = list_entry(ddebug_tables.next,
+				 struct ddebug_table, link);
+	iter->idx = 0;
+	return &iter->table->ddebugs[iter->idx];
+}
+
+/*
+ * Advance the iterator to point to the next _ddebug
+ * object from the one the iterator currently points at,
+ * and returns a pointer to the new _ddebug.  Returns
+ * NULL if the iterator has seen all the _ddebugs.
+ */
+static struct _ddebug *ddebug_iter_next(struct ddebug_iter *iter)
+{
+	if (iter->table == NULL)
+		return NULL;
+	if (++iter->idx == iter->table->num_ddebugs) {
+		/* iterate to next table */
+		iter->idx = 0;
+		if (list_is_last(&iter->table->link, &ddebug_tables)) {
+			iter->table = NULL;
+			return NULL;
+		}
+		iter->table = list_entry(iter->table->link.next,
+					 struct ddebug_table, link);
+	}
+	return &iter->table->ddebugs[iter->idx];
+}
+
+/*
+ * Seq_ops start method.  Called at the start of every
+ * read() call from userspace.  Takes the ddebug_lock and
+ * seeks the seq_file's iterator to the given position.
+ */
+static void *ddebug_proc_start(struct seq_file *m, loff_t *pos)
+{
+	struct ddebug_iter *iter = m->private;
+	struct _ddebug *dp;
+	int n = *pos;
+
+	if (verbose)
+		printk(KERN_INFO "%s: called m=%p *pos=%lld\n",
+			__func__, m, (unsigned long long)*pos);
+
+	mutex_lock(&ddebug_lock);
+
+	if (!n)
+		return SEQ_START_TOKEN;
+	if (n < 0)
+		return NULL;
+	dp = ddebug_iter_first(iter);
+	while (dp != NULL && --n > 0)
+		dp = ddebug_iter_next(iter);
+	return dp;
+}
+
+/*
+ * Seq_ops next method.  Called several times within a read()
+ * call from userspace, with ddebug_lock held.  Walks to the
+ * next _ddebug object with a special case for the header line.
+ */
+static void *ddebug_proc_next(struct seq_file *m, void *p, loff_t *pos)
+{
+	struct ddebug_iter *iter = m->private;
+	struct _ddebug *dp;
+
+	if (verbose)
+		printk(KERN_INFO "%s: called m=%p p=%p *pos=%lld\n",
+			__func__, m, p, (unsigned long long)*pos);
+
+	if (p == SEQ_START_TOKEN)
+		dp = ddebug_iter_first(iter);
+	else
+		dp = ddebug_iter_next(iter);
+	++*pos;
+	return dp;
+}
+
+/*
+ * Seq_ops show method.  Called several times within a read()
+ * call from userspace, with ddebug_lock held.  Formats the
+ * current _ddebug as a single human-readable line, with a
+ * special case for the header line.
+ */
+static int ddebug_proc_show(struct seq_file *m, void *p)
+{
+	struct ddebug_iter *iter = m->private;
+	struct _ddebug *dp = p;
+	char flagsbuf[8];
+
+	if (verbose)
+		printk(KERN_INFO "%s: called m=%p p=%p\n",
+			__func__, m, p);
+
+	if (p == SEQ_START_TOKEN) {
+		seq_puts(m,
+			"# filename:lineno [module]function flags format\n");
+		return 0;
+	}
+
+	seq_printf(m, "%s:%u [%s]%s %s \"",
+		   dp->filename, dp->lineno,
+		   iter->table->mod_name, dp->function,
+		   ddebug_describe_flags(dp, flagsbuf, sizeof(flagsbuf)));
+	seq_escape(m, dp->format, "\t\r\n\"");
+	seq_puts(m, "\"\n");
+
+	return 0;
+}
+
+/*
+ * Seq_ops stop method.  Called at the end of each read()
+ * call from userspace.  Drops ddebug_lock.
+ */
+static void ddebug_proc_stop(struct seq_file *m, void *p)
+{
+	if (verbose)
+		printk(KERN_INFO "%s: called m=%p p=%p\n",
+			__func__, m, p);
+	mutex_unlock(&ddebug_lock);
+}
+
+static const struct seq_operations ddebug_proc_seqops = {
+	.start = ddebug_proc_start,
+	.next = ddebug_proc_next,
+	.show = ddebug_proc_show,
+	.stop = ddebug_proc_stop
+};
+
+/*
+ * File_ops->open method for <debugfs>/dynamic_debug/control.  Does the seq_file
+ * setup dance, and also creates an iterator to walk the _ddebugs.
+ * Note that we create a seq_file always, even for O_WRONLY files
+ * where it's not needed, as doing so simplifies the ->release method.
+ */
+static int ddebug_proc_open(struct inode *inode, struct file *file)
+{
+	struct ddebug_iter *iter;
+	int err;
+
+	if (verbose)
+		printk(KERN_INFO "%s: called\n", __func__);
+
+	iter = kzalloc(sizeof(*iter), GFP_KERNEL);
+	if (iter == NULL)
+		return -ENOMEM;
+
+	err = seq_open(file, &ddebug_proc_seqops);
+	if (err) {
+		kfree(iter);
+		return err;
+	}
+	((struct seq_file *) file->private_data)->private = iter;
+	return 0;
+}
+
+static const struct file_operations ddebug_proc_fops = {
+	.owner = THIS_MODULE,
+	.open = ddebug_proc_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = seq_release_private,
+	.write = ddebug_proc_write
+};
+
+/*
+ * Allocate a new ddebug_table for the given module
+ * and add it to the global list.
+ */
+int ddebug_add_module(struct _ddebug *tab, unsigned int n,
+			     const char *name)
+{
+	struct ddebug_table *dt;
+	char *new_name;
+
+	dt = kzalloc(sizeof(*dt), GFP_KERNEL);
+	if (dt == NULL)
+		return -ENOMEM;
+	new_name = kstrdup(name, GFP_KERNEL);
+	if (new_name == NULL) {
+		kfree(dt);
+		return -ENOMEM;
+	}
+	dt->mod_name = new_name;
+	dt->num_ddebugs = n;
+	dt->num_enabled = 0;
+	dt->ddebugs = tab;
+
+	mutex_lock(&ddebug_lock);
+	list_add_tail(&dt->link, &ddebug_tables);
+	mutex_unlock(&ddebug_lock);
+
+	if (verbose)
+		printk(KERN_INFO "%u debug prints in module %s\n",
+				 n, dt->mod_name);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(ddebug_add_module);
+
+static void ddebug_table_free(struct ddebug_table *dt)
+{
+	list_del_init(&dt->link);
+	kfree(dt->mod_name);
+	kfree(dt);
+}
+
+/*
+ * Called in response to a module being unloaded.  Removes
+ * any ddebug_table's which point at the module.
+ */
+int ddebug_remove_module(char *mod_name)
+{
+	struct ddebug_table *dt, *nextdt;
+	int ret = -ENOENT;
+
+	if (verbose)
+		printk(KERN_INFO "%s: removing module \"%s\"\n",
+				__func__, mod_name);
+
+	mutex_lock(&ddebug_lock);
+	list_for_each_entry_safe(dt, nextdt, &ddebug_tables, link) {
+		if (!strcmp(dt->mod_name, mod_name)) {
+			ddebug_table_free(dt);
+			ret = 0;
+		}
+	}
+	mutex_unlock(&ddebug_lock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(ddebug_remove_module);
+
+static void ddebug_remove_all_tables(void)
+{
+	mutex_lock(&ddebug_lock);
+	while (!list_empty(&ddebug_tables)) {
+		struct ddebug_table *dt = list_entry(ddebug_tables.next,
+						      struct ddebug_table,
+						      link);
+		ddebug_table_free(dt);
+	}
+	mutex_unlock(&ddebug_lock);
+}
+
+static int __init dynamic_debug_init(void)
+{
+	struct dentry *dir, *file;
+	struct _ddebug *iter, *iter_start;
+	const char *modname = NULL;
+	int ret = 0;
+	int n = 0;
+
+	dir = debugfs_create_dir("dynamic_debug", NULL);
+	if (!dir)
+		return -ENOMEM;
+	file = debugfs_create_file("control", 0644, dir, NULL,
+					&ddebug_proc_fops);
+	if (!file) {
+		debugfs_remove(dir);
+		return -ENOMEM;
+	}
+	if (__start___verbose != __stop___verbose) {
+		iter = __start___verbose;
+		modname = iter->modname;
+		iter_start = iter;
+		for (; iter < __stop___verbose; iter++) {
+			if (strcmp(modname, iter->modname)) {
+				ret = ddebug_add_module(iter_start, n, modname);
+				if (ret)
+					goto out_free;
+				n = 0;
+				modname = iter->modname;
+				iter_start = iter;
+			}
+			n++;
+		}
+		ret = ddebug_add_module(iter_start, n, modname);
+	}
+out_free:
+	if (ret) {
+		ddebug_remove_all_tables();
+		debugfs_remove(dir);
+		debugfs_remove(file);
+	}
+	return 0;
+}
+module_init(dynamic_debug_init);