Adding upstream version 4.19.249.upstream/4.19.249

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1048 insertions, 0 deletions

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
new file mode 100644
index 000000000..9305ff43f
--- /dev/null
+++ b/lib/dynamic_debug.c
@@ -0,0 +1,1048 @@
+/*
+ * 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.
+ * Copyright (C) 2011 Bart Van Assche.  All Rights Reserved.
+ * Copyright (C) 2013 Du, Changbin <changbin.du@gmail.com>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ":%s: " fmt, __func__
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/kallsyms.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/string.h>
+#include <linux/parser.h>
+#include <linux/string_helpers.h>
+#include <linux/uaccess.h>
+#include <linux/dynamic_debug.h>
+#include <linux/debugfs.h>
+#include <linux/slab.h>
+#include <linux/jump_label.h>
+#include <linux/hardirq.h>
+#include <linux/sched.h>
+#include <linux/device.h>
+#include <linux/netdevice.h>
+
+extern struct _ddebug __start___verbose[];
+extern struct _ddebug __stop___verbose[];
+
+struct ddebug_table {
+	struct list_head link;
+	const char *mod_name;
+	unsigned int num_ddebugs;
+	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;
+module_param(verbose, int, 0644);
+
+/* Return the path relative to source root */
+static inline const char *trim_prefix(const char *path)
+{
+	int skip = strlen(__FILE__) - strlen("lib/dynamic_debug.c");
+
+	if (strncmp(path, __FILE__, skip))
+		skip = 0; /* prefix mismatch, don't skip */
+
+	return path + skip;
+}
+
+static struct { unsigned flag:8; char opt_char; } opt_array[] = {
+	{ _DPRINTK_FLAGS_PRINT, 'p' },
+	{ _DPRINTK_FLAGS_INCL_MODNAME, 'm' },
+	{ _DPRINTK_FLAGS_INCL_FUNCNAME, 'f' },
+	{ _DPRINTK_FLAGS_INCL_LINENO, 'l' },
+	{ _DPRINTK_FLAGS_INCL_TID, 't' },
+	{ _DPRINTK_FLAGS_NONE, '_' },
+};
+
+struct flagsbuf { char buf[ARRAY_SIZE(opt_array)+1]; };
+
+/* format a string into buf[] which describes the _ddebug's flags */
+static char *ddebug_describe_flags(unsigned int flags, struct flagsbuf *fb)
+{
+	char *p = fb->buf;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(opt_array); ++i)
+		if (flags & opt_array[i].flag)
+			*p++ = opt_array[i].opt_char;
+	if (p == fb->buf)
+		*p++ = '_';
+	*p = '\0';
+
+	return fb->buf;
+}
+
+#define vpr_info(fmt, ...)					\
+do {								\
+	if (verbose)						\
+		pr_info(fmt, ##__VA_ARGS__);			\
+} while (0)
+
+static void vpr_info_dq(const struct ddebug_query *query, const char *msg)
+{
+	/* trim any trailing newlines */
+	int fmtlen = 0;
+
+	if (query->format) {
+		fmtlen = strlen(query->format);
+		while (fmtlen && query->format[fmtlen - 1] == '\n')
+			fmtlen--;
+	}
+
+	vpr_info("%s: func=\"%s\" file=\"%s\" module=\"%s\" format=\"%.*s\" lineno=%u-%u\n",
+		 msg,
+		 query->function ? query->function : "",
+		 query->filename ? query->filename : "",
+		 query->module ? query->module : "",
+		 fmtlen, query->format ? query->format : "",
+		 query->first_lineno, query->last_lineno);
+}
+
+/*
+ * Search the tables for _ddebug's which match the given `query' and
+ * apply the `flags' and `mask' to them.  Returns number of matching
+ * callsites, normally the same as number of changes.  If verbose,
+ * logs the changes.  Takes ddebug_lock.
+ */
+static int 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;
+	struct flagsbuf fbuf;
+
+	/* search for matching ddebugs */
+	mutex_lock(&ddebug_lock);
+	list_for_each_entry(dt, &ddebug_tables, link) {
+
+		/* match against the module name */
+		if (query->module &&
+		    !match_wildcard(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 &&
+			    !match_wildcard(query->filename, dp->filename) &&
+			    !match_wildcard(query->filename,
+					   kbasename(dp->filename)) &&
+			    !match_wildcard(query->filename,
+					   trim_prefix(dp->filename)))
+				continue;
+
+			/* match against the function */
+			if (query->function &&
+			    !match_wildcard(query->function, dp->function))
+				continue;
+
+			/* match against the format */
+			if (query->format &&
+			    !strstr(dp->format, query->format))
+				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;
+#ifdef CONFIG_JUMP_LABEL
+			if (dp->flags & _DPRINTK_FLAGS_PRINT) {
+				if (!(flags & _DPRINTK_FLAGS_PRINT))
+					static_branch_disable(&dp->key.dd_key_true);
+			} else if (flags & _DPRINTK_FLAGS_PRINT)
+				static_branch_enable(&dp->key.dd_key_true);
+#endif
+			dp->flags = newflags;
+			vpr_info("changed %s:%d [%s]%s =%s\n",
+				 trim_prefix(dp->filename), dp->lineno,
+				 dt->mod_name, dp->function,
+				 ddebug_describe_flags(dp->flags, &fbuf));
+		}
+	}
+	mutex_unlock(&ddebug_lock);
+
+	if (!nfound && verbose)
+		pr_info("no matches for query\n");
+
+	return nfound;
+}
+
+/*
+ * Split the buffer `buf' into space-separated words.
+ * Handles simple " and ' quoting, i.e. without nested,
+ * embedded or escaped \".  Return the number of words
+ * or <0 on error.
+ */
+static int ddebug_tokenize(char *buf, char *words[], int maxwords)
+{
+	int nwords = 0;
+
+	while (*buf) {
+		char *end;
+
+		/* Skip leading whitespace */
+		buf = skip_spaces(buf);
+		if (!*buf)
+			break;	/* oh, it was trailing whitespace */
+		if (*buf == '#')
+			break;	/* token starts comment, skip rest of line */
+
+		/* find `end' of word, whitespace separated or quoted */
+		if (*buf == '"' || *buf == '\'') {
+			int quote = *buf++;
+			for (end = buf; *end && *end != quote; end++)
+				;
+			if (!*end) {
+				pr_err("unclosed quote: %s\n", buf);
+				return -EINVAL;	/* unclosed quote */
+			}
+		} else {
+			for (end = buf; *end && !isspace(*end); end++)
+				;
+			BUG_ON(end == buf);
+		}
+
+		/* `buf' is start of word, `end' is one past its end */
+		if (nwords == maxwords) {
+			pr_err("too many words, legal max <=%d\n", maxwords);
+			return -EINVAL;	/* ran out of words[] before bytes */
+		}
+		if (*end)
+			*end++ = '\0';	/* terminate the word */
+		words[nwords++] = buf;
+		buf = end;
+	}
+
+	if (verbose) {
+		int i;
+		pr_info("split into words:");
+		for (i = 0; i < nwords; i++)
+			pr_cont(" \"%s\"", words[i]);
+		pr_cont("\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)
+{
+	BUG_ON(str == NULL);
+	if (*str == '\0') {
+		*val = 0;
+		return 0;
+	}
+	if (kstrtouint(str, 10, val) < 0) {
+		pr_err("bad line-number: %s\n", str);
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static int check_set(const char **dest, char *src, char *name)
+{
+	int rc = 0;
+
+	if (*dest) {
+		rc = -EINVAL;
+		pr_err("match-spec:%s val:%s overridden by %s\n",
+		       name, *dest, src);
+	}
+	*dest = src;
+	return rc;
+}
+
+/*
+ * 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
+ *
+ * Only 1 of each type is allowed.
+ * Returns 0 on success, <0 on error.
+ */
+static int ddebug_parse_query(char *words[], int nwords,
+			struct ddebug_query *query, const char *modname)
+{
+	unsigned int i;
+	int rc = 0;
+
+	/* check we have an even number of words */
+	if (nwords % 2 != 0) {
+		pr_err("expecting pairs of match-spec <value>\n");
+		return -EINVAL;
+	}
+	memset(query, 0, sizeof(*query));
+
+	if (modname)
+		/* support $modname.dyndbg=<multiple queries> */
+		query->module = modname;
+
+	for (i = 0; i < nwords; i += 2) {
+		if (!strcmp(words[i], "func")) {
+			rc = check_set(&query->function, words[i+1], "func");
+		} else if (!strcmp(words[i], "file")) {
+			rc = check_set(&query->filename, words[i+1], "file");
+		} else if (!strcmp(words[i], "module")) {
+			rc = check_set(&query->module, words[i+1], "module");
+		} else if (!strcmp(words[i], "format")) {
+			string_unescape_inplace(words[i+1], UNESCAPE_SPACE |
+							    UNESCAPE_OCTAL |
+							    UNESCAPE_SPECIAL);
+			rc = check_set(&query->format, words[i+1], "format");
+		} else if (!strcmp(words[i], "line")) {
+			char *first = words[i+1];
+			char *last = strchr(first, '-');
+			if (query->first_lineno || query->last_lineno) {
+				pr_err("match-spec: line used 2x\n");
+				return -EINVAL;
+			}
+			if (last)
+				*last++ = '\0';
+			if (parse_lineno(first, &query->first_lineno) < 0)
+				return -EINVAL;
+			if (last) {
+				/* range <first>-<last> */
+				if (parse_lineno(last, &query->last_lineno) < 0)
+					return -EINVAL;
+
+				/* special case for last lineno not specified */
+				if (query->last_lineno == 0)
+					query->last_lineno = UINT_MAX;
+
+				if (query->last_lineno < query->first_lineno) {
+					pr_err("last-line:%d < 1st-line:%d\n",
+						query->last_lineno,
+						query->first_lineno);
+					return -EINVAL;
+				}
+			} else {
+				query->last_lineno = query->first_lineno;
+			}
+		} else {
+			pr_err("unknown keyword \"%s\"\n", words[i]);
+			return -EINVAL;
+		}
+		if (rc)
+			return rc;
+	}
+	vpr_info_dq(query, "parsed");
+	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 = '=', i;
+
+	switch (*str) {
+	case '+':
+	case '-':
+	case '=':
+		op = *str++;
+		break;
+	default:
+		pr_err("bad flag-op %c, at start of %s\n", *str, str);
+		return -EINVAL;
+	}
+	vpr_info("op='%c'\n", op);
+
+	for (; *str ; ++str) {
+		for (i = ARRAY_SIZE(opt_array) - 1; i >= 0; i--) {
+			if (*str == opt_array[i].opt_char) {
+				flags |= opt_array[i].flag;
+				break;
+			}
+		}
+		if (i < 0) {
+			pr_err("unknown flag '%c' in \"%s\"\n", *str, str);
+			return -EINVAL;
+		}
+	}
+	vpr_info("flags=0x%x\n", 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;
+	}
+	vpr_info("*flagsp=0x%x *maskp=0x%x\n", *flagsp, *maskp);
+	return 0;
+}
+
+static int ddebug_exec_query(char *query_string, const char *modname)
+{
+	unsigned int flags = 0, mask = 0;
+	struct ddebug_query query;
+#define MAXWORDS 9
+	int nwords, nfound;
+	char *words[MAXWORDS];
+
+	nwords = ddebug_tokenize(query_string, words, MAXWORDS);
+	if (nwords <= 0) {
+		pr_err("tokenize failed\n");
+		return -EINVAL;
+	}
+	/* check flags 1st (last arg) so query is pairs of spec,val */
+	if (ddebug_parse_flags(words[nwords-1], &flags, &mask)) {
+		pr_err("flags parse failed\n");
+		return -EINVAL;
+	}
+	if (ddebug_parse_query(words, nwords-1, &query, modname)) {
+		pr_err("query parse failed\n");
+		return -EINVAL;
+	}
+	/* actually go and implement the change */
+	nfound = ddebug_change(&query, flags, mask);
+	vpr_info_dq(&query, nfound ? "applied" : "no-match");
+
+	return nfound;
+}
+
+/* handle multiple queries in query string, continue on error, return
+   last error or number of matching callsites.  Module name is either
+   in param (for boot arg) or perhaps in query string.
+*/
+static int ddebug_exec_queries(char *query, const char *modname)
+{
+	char *split;
+	int i, errs = 0, exitcode = 0, rc, nfound = 0;
+
+	for (i = 0; query; query = split) {
+		split = strpbrk(query, ";\n");
+		if (split)
+			*split++ = '\0';
+
+		query = skip_spaces(query);
+		if (!query || !*query || *query == '#')
+			continue;
+
+		vpr_info("query %d: \"%s\"\n", i, query);
+
+		rc = ddebug_exec_query(query, modname);
+		if (rc < 0) {
+			errs++;
+			exitcode = rc;
+		} else {
+			nfound += rc;
+		}
+		i++;
+	}
+	vpr_info("processed %d queries, with %d matches, %d errs\n",
+		 i, nfound, errs);
+
+	if (exitcode)
+		return exitcode;
+	return nfound;
+}
+
+#define PREFIX_SIZE 64
+
+static int remaining(int wrote)
+{
+	if (PREFIX_SIZE - wrote > 0)
+		return PREFIX_SIZE - wrote;
+	return 0;
+}
+
+static char *dynamic_emit_prefix(const struct _ddebug *desc, char *buf)
+{
+	int pos_after_tid;
+	int pos = 0;
+
+	*buf = '\0';
+
+	if (desc->flags & _DPRINTK_FLAGS_INCL_TID) {
+		if (in_interrupt())
+			pos += snprintf(buf + pos, remaining(pos), "<intr> ");
+		else
+			pos += snprintf(buf + pos, remaining(pos), "[%d] ",
+					task_pid_vnr(current));
+	}
+	pos_after_tid = pos;
+	if (desc->flags & _DPRINTK_FLAGS_INCL_MODNAME)
+		pos += snprintf(buf + pos, remaining(pos), "%s:",
+				desc->modname);
+	if (desc->flags & _DPRINTK_FLAGS_INCL_FUNCNAME)
+		pos += snprintf(buf + pos, remaining(pos), "%s:",
+				desc->function);
+	if (desc->flags & _DPRINTK_FLAGS_INCL_LINENO)
+		pos += snprintf(buf + pos, remaining(pos), "%d:",
+				desc->lineno);
+	if (pos - pos_after_tid)
+		pos += snprintf(buf + pos, remaining(pos), " ");
+	if (pos >= PREFIX_SIZE)
+		buf[PREFIX_SIZE - 1] = '\0';
+
+	return buf;
+}
+
+void __dynamic_pr_debug(struct _ddebug *descriptor, const char *fmt, ...)
+{
+	va_list args;
+	struct va_format vaf;
+	char buf[PREFIX_SIZE];
+
+	BUG_ON(!descriptor);
+	BUG_ON(!fmt);
+
+	va_start(args, fmt);
+
+	vaf.fmt = fmt;
+	vaf.va = &args;
+
+	printk(KERN_DEBUG "%s%pV", dynamic_emit_prefix(descriptor, buf), &vaf);
+
+	va_end(args);
+}
+EXPORT_SYMBOL(__dynamic_pr_debug);
+
+void __dynamic_dev_dbg(struct _ddebug *descriptor,
+		      const struct device *dev, const char *fmt, ...)
+{
+	struct va_format vaf;
+	va_list args;
+
+	BUG_ON(!descriptor);
+	BUG_ON(!fmt);
+
+	va_start(args, fmt);
+
+	vaf.fmt = fmt;
+	vaf.va = &args;
+
+	if (!dev) {
+		printk(KERN_DEBUG "(NULL device *): %pV", &vaf);
+	} else {
+		char buf[PREFIX_SIZE];
+
+		dev_printk_emit(LOGLEVEL_DEBUG, dev, "%s%s %s: %pV",
+				dynamic_emit_prefix(descriptor, buf),
+				dev_driver_string(dev), dev_name(dev),
+				&vaf);
+	}
+
+	va_end(args);
+}
+EXPORT_SYMBOL(__dynamic_dev_dbg);
+
+#ifdef CONFIG_NET
+
+void __dynamic_netdev_dbg(struct _ddebug *descriptor,
+			  const struct net_device *dev, const char *fmt, ...)
+{
+	struct va_format vaf;
+	va_list args;
+
+	BUG_ON(!descriptor);
+	BUG_ON(!fmt);
+
+	va_start(args, fmt);
+
+	vaf.fmt = fmt;
+	vaf.va = &args;
+
+	if (dev && dev->dev.parent) {
+		char buf[PREFIX_SIZE];
+
+		dev_printk_emit(LOGLEVEL_DEBUG, dev->dev.parent,
+				"%s%s %s %s%s: %pV",
+				dynamic_emit_prefix(descriptor, buf),
+				dev_driver_string(dev->dev.parent),
+				dev_name(dev->dev.parent),
+				netdev_name(dev), netdev_reg_state(dev),
+				&vaf);
+	} else if (dev) {
+		printk(KERN_DEBUG "%s%s: %pV", netdev_name(dev),
+		       netdev_reg_state(dev), &vaf);
+	} else {
+		printk(KERN_DEBUG "(NULL net_device): %pV", &vaf);
+	}
+
+	va_end(args);
+}
+EXPORT_SYMBOL(__dynamic_netdev_dbg);
+
+#endif
+
+#define DDEBUG_STRING_SIZE 1024
+static __initdata char ddebug_setup_string[DDEBUG_STRING_SIZE];
+
+static __init int ddebug_setup_query(char *str)
+{
+	if (strlen(str) >= DDEBUG_STRING_SIZE) {
+		pr_warn("ddebug boot param string too large\n");
+		return 0;
+	}
+	strlcpy(ddebug_setup_string, str, DDEBUG_STRING_SIZE);
+	return 1;
+}
+
+__setup("ddebug_query=", ddebug_setup_query);
+
+/*
+ * File_ops->write method for <debugfs>/dynamic_debug/control.  Gathers the
+ * command text from userspace, parses and executes it.
+ */
+#define USER_BUF_PAGE 4096
+static ssize_t ddebug_proc_write(struct file *file, const char __user *ubuf,
+				  size_t len, loff_t *offp)
+{
+	char *tmpbuf;
+	int ret;
+
+	if (len == 0)
+		return 0;
+	if (len > USER_BUF_PAGE - 1) {
+		pr_warn("expected <%d bytes into control\n", USER_BUF_PAGE);
+		return -E2BIG;
+	}
+	tmpbuf = memdup_user_nul(ubuf, len);
+	if (IS_ERR(tmpbuf))
+		return PTR_ERR(tmpbuf);
+	vpr_info("read %d bytes from userspace\n", (int)len);
+
+	ret = ddebug_exec_queries(tmpbuf, NULL);
+	kfree(tmpbuf);
+	if (ret < 0)
+		return ret;
+
+	*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;
+
+	vpr_info("called m=%p *pos=%lld\n", 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;
+
+	vpr_info("called m=%p p=%p *pos=%lld\n",
+		 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;
+	struct flagsbuf flags;
+
+	vpr_info("called m=%p p=%p\n", 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 \"",
+		   trim_prefix(dp->filename), dp->lineno,
+		   iter->table->mod_name, dp->function,
+		   ddebug_describe_flags(dp->flags, &flags));
+	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)
+{
+	vpr_info("called m=%p p=%p\n", 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)
+{
+	vpr_info("called\n");
+	return seq_open_private(file, &ddebug_proc_seqops,
+				sizeof(struct ddebug_iter));
+}
+
+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;
+	const char *new_name;
+
+	dt = kzalloc(sizeof(*dt), GFP_KERNEL);
+	if (dt == NULL)
+		return -ENOMEM;
+	new_name = kstrdup_const(name, GFP_KERNEL);
+	if (new_name == NULL) {
+		kfree(dt);
+		return -ENOMEM;
+	}
+	dt->mod_name = new_name;
+	dt->num_ddebugs = n;
+	dt->ddebugs = tab;
+
+	mutex_lock(&ddebug_lock);
+	list_add_tail(&dt->link, &ddebug_tables);
+	mutex_unlock(&ddebug_lock);
+
+	vpr_info("%u debug prints in module %s\n", n, dt->mod_name);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(ddebug_add_module);
+
+/* helper for ddebug_dyndbg_(boot|module)_param_cb */
+static int ddebug_dyndbg_param_cb(char *param, char *val,
+				const char *modname, int on_err)
+{
+	char *sep;
+
+	sep = strchr(param, '.');
+	if (sep) {
+		/* needed only for ddebug_dyndbg_boot_param_cb */
+		*sep = '\0';
+		modname = param;
+		param = sep + 1;
+	}
+	if (strcmp(param, "dyndbg"))
+		return on_err; /* determined by caller */
+
+	ddebug_exec_queries((val ? val : "+p"), modname);
+
+	return 0; /* query failure shouldnt stop module load */
+}
+
+/* handle both dyndbg and $module.dyndbg params at boot */
+static int ddebug_dyndbg_boot_param_cb(char *param, char *val,
+				const char *unused, void *arg)
+{
+	vpr_info("%s=\"%s\"\n", param, val);
+	return ddebug_dyndbg_param_cb(param, val, NULL, 0);
+}
+
+/*
+ * modprobe foo finds foo.params in boot-args, strips "foo.", and
+ * passes them to load_module().  This callback gets unknown params,
+ * processes dyndbg params, rejects others.
+ */
+int ddebug_dyndbg_module_param_cb(char *param, char *val, const char *module)
+{
+	vpr_info("module: %s %s=\"%s\"\n", module, param, val);
+	return ddebug_dyndbg_param_cb(param, val, module, -ENOENT);
+}
+
+static void ddebug_table_free(struct ddebug_table *dt)
+{
+	list_del_init(&dt->link);
+	kfree_const(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(const char *mod_name)
+{
+	struct ddebug_table *dt, *nextdt;
+	int ret = -ENOENT;
+
+	vpr_info("removing module \"%s\"\n", 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 __initdata int ddebug_init_success;
+
+static int __init dynamic_debug_init_debugfs(void)
+{
+	struct dentry *dir, *file;
+
+	if (!ddebug_init_success)
+		return -ENODEV;
+
+	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;
+	}
+	return 0;
+}
+
+static int __init dynamic_debug_init(void)
+{
+	struct _ddebug *iter, *iter_start;
+	const char *modname = NULL;
+	char *cmdline;
+	int ret = 0;
+	int n = 0, entries = 0, modct = 0;
+	int verbose_bytes = 0;
+
+	if (__start___verbose == __stop___verbose) {
+		pr_warn("_ddebug table is empty in a CONFIG_DYNAMIC_DEBUG build\n");
+		return 1;
+	}
+	iter = __start___verbose;
+	modname = iter->modname;
+	iter_start = iter;
+	for (; iter < __stop___verbose; iter++) {
+		entries++;
+		verbose_bytes += strlen(iter->modname) + strlen(iter->function)
+			+ strlen(iter->filename) + strlen(iter->format);
+
+		if (strcmp(modname, iter->modname)) {
+			modct++;
+			ret = ddebug_add_module(iter_start, n, modname);
+			if (ret)
+				goto out_err;
+			n = 0;
+			modname = iter->modname;
+			iter_start = iter;
+		}
+		n++;
+	}
+	ret = ddebug_add_module(iter_start, n, modname);
+	if (ret)
+		goto out_err;
+
+	ddebug_init_success = 1;
+	vpr_info("%d modules, %d entries and %d bytes in ddebug tables, %d bytes in (readonly) verbose section\n",
+		 modct, entries, (int)(modct * sizeof(struct ddebug_table)),
+		 verbose_bytes + (int)(__stop___verbose - __start___verbose));
+
+	/* apply ddebug_query boot param, dont unload tables on err */
+	if (ddebug_setup_string[0] != '\0') {
+		pr_warn("ddebug_query param name is deprecated, change it to dyndbg\n");
+		ret = ddebug_exec_queries(ddebug_setup_string, NULL);
+		if (ret < 0)
+			pr_warn("Invalid ddebug boot param %s\n",
+				ddebug_setup_string);
+		else
+			pr_info("%d changes by ddebug_query\n", ret);
+	}
+	/* now that ddebug tables are loaded, process all boot args
+	 * again to find and activate queries given in dyndbg params.
+	 * While this has already been done for known boot params, it
+	 * ignored the unknown ones (dyndbg in particular).  Reusing
+	 * parse_args avoids ad-hoc parsing.  This will also attempt
+	 * to activate queries for not-yet-loaded modules, which is
+	 * slightly noisy if verbose, but harmless.
+	 */
+	cmdline = kstrdup(saved_command_line, GFP_KERNEL);
+	parse_args("dyndbg params", cmdline, NULL,
+		   0, 0, 0, NULL, &ddebug_dyndbg_boot_param_cb);
+	kfree(cmdline);
+	return 0;
+
+out_err:
+	ddebug_remove_all_tables();
+	return 0;
+}
+/* Allow early initialization for boot messages via boot param */
+early_initcall(dynamic_debug_init);
+
+/* Debugfs setup must be done later */
+fs_initcall(dynamic_debug_init_debugfs);