linux-kernel - [RFC PATCH v5 16/28] dyndbg: add _index to struct

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Date:   Tue, 11 May 2021 12:50:45 -0600
From:   Jim Cromie <jim.cromie@...il.com>
To:     Jason Baron <jbaron@...mai.com>, linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, Jim Cromie <jim.cromie@...il.com>
Subject: [RFC PATCH v5 16/28] dyndbg: add _index to struct _ddebug

We currently use dp->site to map: &__dyndbg[N] -> &__dyndbg_sites[N].
We want to drop site; new _ddebug._index provides the N.  This just
initializes that index.

ddebug_add_module()'s new job is to initialize _index.  In order to
handle builtin modules (sections contain catenated blocks of modules'
callsites) it gets a new base arg to monotonically increment _index
over multiple modules.  Since ddebug_add_module() is used indirectly
by module.c, the new arg is hidden in __ddebug_add_module(), and
defaults to 0 in the wrapper.

Signed-off-by: Jim Cromie <jim.cromie@...il.com>
---
 include/linux/dynamic_debug.h |  2 ++
 lib/dynamic_debug.c           | 25 ++++++++++++++++++++-----
 2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index 868e0769b72d..a15e417cbba8 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
@@ -52,6 +53,7 @@ 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 77c5135879c2..c5927b6c1c0c 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -1028,10 +1028,12 @@ 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 int numdbgs, unsigned int base,
+			       const char *modname)
 {
 	struct ddebug_table *dt;
+	int i;
 
 	v3pr_info("add-module: %s.%d sites\n", modname, numdbgs);
 	if (!numdbgs) {
@@ -1055,6 +1057,12 @@ int ddebug_add_module(struct _ddebug *tab, struct _ddebug_site *sites,
 	dt->ddebugs = tab;
 	dt->sites = sites;
 
+	for (i = 0; i < numdbgs; i++, base++) {
+		tab[i]._index = base;
+		v3pr_info(" %d %d %s.%s.%d\n", i, base, modname,
+			  tab[i].site->function, tab[i].lineno);
+	}
+
 	mutex_lock(&ddebug_lock);
 	list_add(&dt->link, &ddebug_tables);
 	mutex_unlock(&ddebug_lock);
@@ -1063,6 +1071,12 @@ 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 +1191,7 @@ 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 +1215,8 @@ 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 +1226,7 @@ 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;
 
-- 
2.31.1