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From:   Jim Cromie <jim.cromie@gmail.com>
To:     jbaron@akamai.com, gregkh@linuxfoundation.org,
        linux-kernel@vger.kernel.org
Cc:     Jim Cromie <jim.cromie@gmail.com>
Subject: [RFC PATCH v4 15/19] dyndbg: add _index to struct _ddebug
Date:   Wed, 17 Mar 2021 00:54:08 -0600
Message-Id: <20210317065412.2890414-16-jim.cromie@gmail.com>
In-Reply-To: <20210317065412.2890414-1-jim.cromie@gmail.com>
References: <20210317065412.2890414-1-jim.cromie@gmail.com>
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We currently use dp->site to map: &__dyndbg[N] -> &__dyndbg_sites[N].
We want to drop site, new _ddebug._index provides the N.

The mapping is done in ddebug_site_get():

For builtin modules, a _ddebug *ptr is between __start___dyndbg and
__stop___dyndbg, and we can use &__start___dyndbg_sites[N] directly.
For loadable modules, we still need work, so we print rubbish, and
just return site pointer (which is correct).

ddebug_add_module() handles _index initialization:
Its new task is to number each module consecutively, so it gets new
base arg to pass the next starting index.

To actually drop site, We need both the module's __dyndbg* section
addys, and we need their relative placement to have a base-to-base
offset.

PLAN - a table header connecting 2 tables.

- ddebug_table points to both __dyndbgs & __dyndbg_sites.
  but *ddebugs & *sites are independent.
  no path from ddebugs[n] -> ddebug_sites[n]

If we have a header record in-situ, which keeps the site pointer we
seek to eliminate from _ddebug, and its in element[0] of both vectors,
we can go:

  ddebugs[n] -> ddebugs[0] -> containerof -> site[n]

  union ddebug_table_header {
  	struct ddebug_table *owner;
	struct _ddebug item;
  }
  and
  struct ddebug_table_vector {
  	 struct ddebug_table *owner;
	 struct _ddebug vector[];
  }

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
 include/linux/dynamic_debug.h |  2 ++
 lib/dynamic_debug.c           | 40 +++++++++++++++++++++++++++++------
 2 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index 7d33475d226a..18689db0e2c0 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -29,6 +29,7 @@ struct _ddebug {
 	/* format is always needed, lineno shares word with flags */
 	const char *format;
 	const unsigned lineno:18;
+	unsigned _index:14;
 	/*
 	 * The flags field controls the behaviour at the callsite.
 	 * The bits here are changed dynamically when the user
@@ -56,6 +57,7 @@ struct _ddebug {
 #define _DPRINTK_FLAGS_DEFAULT 0
 #endif
 	unsigned int flags:8;
+
 #ifdef CONFIG_JUMP_LABEL
 	union {
 		struct static_key_true dd_key_true;
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 1f59407b6a83..54737647556c 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -123,6 +123,8 @@ do {								\
 #define vpr_info(fmt, ...)	vnpr_info(1, fmt, ##__VA_ARGS__)
 #define v2pr_info(fmt, ...)	vnpr_info(2, fmt, ##__VA_ARGS__)
 #define v3pr_info(fmt, ...)	vnpr_info(3, fmt, ##__VA_ARGS__)
+#define v4pr_info(fmt, ...)	vnpr_info(4, fmt, ##__VA_ARGS__)
+#define v5pr_info(fmt, ...)	vnpr_info(5, fmt, ##__VA_ARGS__)
 
 static void vpr_info_dq(const struct ddebug_query *query, const char *msg)
 {
@@ -146,7 +148,17 @@ static void vpr_info_dq(const struct ddebug_query *query, const char *msg)
 
 static struct _ddebug_site *ddebug_site_get(struct _ddebug *dp)
 {
-	return dp->site; /* passthru abstraction */
+	v4pr_info("get %d: %s.%s.%d\n", dp->_index, dp->site->modname,
+		  dp->site->function, dp->lineno);
+
+	if (dp >= __start___dyndbg && dp < __stop___dyndbg) {
+		v4pr_info(" is builtin: %d %ld\n", dp->_index, dp - __start___dyndbg);
+		return &__start___dyndbg_sites[ dp - __start___dyndbg ];
+	} else {
+		v3pr_info(" is loaded: %d %ld\n", dp->_index, dp - __start___dyndbg);
+		return dp->site;
+	}
+	return dp->site;
 }
 static inline void ddebug_site_put(struct _ddebug *dp)
 {
@@ -1034,10 +1046,12 @@ static const struct proc_ops proc_fops = {
  * Allocate a new ddebug_table for the given module
  * and add it to the global list.
  */
-int ddebug_add_module(struct _ddebug *tab, struct _ddebug_site *sites,
-		      unsigned int numdbgs, const char *modname)
+static int __ddebug_add_module(struct _ddebug *tab, struct _ddebug_site *sites,
+			       unsigned numdbgs, unsigned base,
+			       const char *modname)
 {
 	struct ddebug_table *dt;
+	int i;
 
 	dt = kzalloc(sizeof(*dt), GFP_KERNEL);
 	if (dt == NULL) {
@@ -1055,6 +1069,13 @@ int ddebug_add_module(struct _ddebug *tab, struct _ddebug_site *sites,
 	dt->ddebugs = tab;
 	dt->sites = sites;
 
+	v3pr_info("add-module: %s\n", modname);
+	for (i = 0; i < numdbgs; i++) {
+		tab[i]._index = base++;
+		v3pr_info(" %d %d %s.%s.%d\n", i, tab[i]._index, modname,
+			  tab[i].site->function, tab[i].lineno);
+	}
+
 	mutex_lock(&ddebug_lock);
 	list_add(&dt->link, &ddebug_tables);
 	mutex_unlock(&ddebug_lock);
@@ -1063,6 +1084,12 @@ int ddebug_add_module(struct _ddebug *tab, struct _ddebug_site *sites,
 	return 0;
 }
 
+int ddebug_add_module(struct _ddebug *tab, struct _ddebug_site *sites,
+		      unsigned int numdbgs, const char *modname)
+{
+	return __ddebug_add_module(tab, sites, numdbgs, 0, modname);
+}
+
 /* helper for ddebug_dyndbg_(boot|module)_param_cb */
 static int ddebug_dyndbg_param_cb(char *param, char *val,
 				const char *modname, int on_err)
@@ -1177,6 +1204,7 @@ static int __init dynamic_debug_init(void)
 	char *cmdline;
 	int ret = 0;
 	int site_ct = 0, entries = 0, modct = 0;
+	int mod_index = 0;
 
 	if (&__start___dyndbg == &__stop___dyndbg) {
 		if (IS_ENABLED(CONFIG_DYNAMIC_DEBUG)) {
@@ -1200,8 +1228,8 @@ static int __init dynamic_debug_init(void)
 		if (strcmp(modname, site->modname)) {
 			modct++;
 
-			ret = ddebug_add_module(iter_mod_start, site_mod_start,
-						site_ct, modname);
+			ret = __ddebug_add_module(iter_mod_start, site_mod_start,
+						  site_ct, mod_index, modname);
 			if (ret)
 				goto out_err;
 			site_ct = 0;
@@ -1211,7 +1239,7 @@ static int __init dynamic_debug_init(void)
 		}
 		site_ct++;
 	}
-	ret = ddebug_add_module(iter_mod_start, site_mod_start, site_ct, modname);
+	ret = __ddebug_add_module(iter_mod_start, site_mod_start, site_ct, mod_index, modname);
 	if (ret)
 		goto out_err;
 
-- 
2.29.2