Re: [PATCH v9 13/14] module: Move kdb_modules list out of core code

[Christoph Hellwig <hch@infradead.org>]

On Thu, Mar 03, 2022 at 02:59:49PM +0000, Daniel Thompson wrote:
> 
> One of the best ways that we can common up code might be to dust
> off some code I wrote a while back to display seq_files from
> kdb.
> 
> The basic idea worked well enough but it often needs special
> start/stop operatings to ensure the start meeds kdb's rather
> odd locking restrictions. If there is a willingness for
> something like the below to be included in the module code then we
> could replace kdb_lsmod() with something that reused the code to
>  format /proc/modules.

Displaying seq_files sounds nice to have, but in the short term I'm
just thinking of something like this:

diff --git a/include/linux/kdb.h b/include/linux/kdb.h
index ea0f5e580fac2..07dfb6a20a1c4 100644
--- a/include/linux/kdb.h
+++ b/include/linux/kdb.h
@@ -222,5 +222,6 @@ enum {
 
 extern int kdbgetintenv(const char *, int *);
 extern int kdb_set(int, const char **);
+int kdb_lsmod(int argc, const char **argv);
 
 #endif	/* !_KDB_H */
diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index 0852a537dad4c..292a407118a4f 100644
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -2004,54 +2004,6 @@ static int kdb_ef(int argc, const char **argv)
 	return 0;
 }
 
-#if defined(CONFIG_MODULES)
-/*
- * kdb_lsmod - This function implements the 'lsmod' command.  Lists
- *	currently loaded kernel modules.
- *	Mostly taken from userland lsmod.
- */
-static int kdb_lsmod(int argc, const char **argv)
-{
-	struct module *mod;
-
-	if (argc != 0)
-		return KDB_ARGCOUNT;
-
-	kdb_printf("Module                  Size  modstruct     Used by\n");
-	list_for_each_entry(mod, kdb_modules, list) {
-		if (mod->state == MODULE_STATE_UNFORMED)
-			continue;
-
-		kdb_printf("%-20s%8u  0x%px ", mod->name,
-			   mod->core_layout.size, (void *)mod);
-#ifdef CONFIG_MODULE_UNLOAD
-		kdb_printf("%4d ", module_refcount(mod));
-#endif
-		if (mod->state == MODULE_STATE_GOING)
-			kdb_printf(" (Unloading)");
-		else if (mod->state == MODULE_STATE_COMING)
-			kdb_printf(" (Loading)");
-		else
-			kdb_printf(" (Live)");
-		kdb_printf(" 0x%px", mod->core_layout.base);
-
-#ifdef CONFIG_MODULE_UNLOAD
-		{
-			struct module_use *use;
-			kdb_printf(" [ ");
-			list_for_each_entry(use, &mod->source_list,
-					    source_list)
-				kdb_printf("%s ", use->target->name);
-			kdb_printf("]\n");
-		}
-#endif
-	}
-
-	return 0;
-}
-
-#endif	/* CONFIG_MODULES */
-
 /*
  * kdb_env - This function implements the 'env' command.  Display the
  *	current environment variables.
diff --git a/kernel/debug/kdb/kdb_private.h b/kernel/debug/kdb/kdb_private.h
index 0d2f9feea0a46..1f8c519a5f81c 100644
--- a/kernel/debug/kdb/kdb_private.h
+++ b/kernel/debug/kdb/kdb_private.h
@@ -226,10 +226,6 @@ extern void kdb_kbd_cleanup_state(void);
 #define kdb_kbd_cleanup_state()
 #endif /* ! CONFIG_KDB_KEYBOARD */
 
-#ifdef CONFIG_MODULES
-extern struct list_head *kdb_modules;
-#endif /* CONFIG_MODULES */
-
 extern char kdb_prompt_str[];
 
 #define	KDB_WORD_SIZE	((int)sizeof(unsigned long))
diff --git a/kernel/module.c b/kernel/module.c
index 6cea788fd965c..754ec20aab4f1 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -57,6 +57,7 @@
 #include <linux/bsearch.h>
 #include <linux/dynamic_debug.h>
 #include <linux/audit.h>
+#include <linux/kdb.h>
 #include <uapi/linux/module.h>
 #include "module-internal.h"
 
@@ -252,10 +253,6 @@ static void mod_update_bounds(struct module *mod)
 		__mod_update_bounds(mod->init_layout.base, mod->init_layout.size);
 }
 
-#ifdef CONFIG_KGDB_KDB
-struct list_head *kdb_modules = &modules; /* kdb needs the list of modules */
-#endif /* CONFIG_KGDB_KDB */
-
 static void module_assert_mutex_or_preempt(void)
 {
 #ifdef CONFIG_LOCKDEP
@@ -4808,3 +4805,45 @@ void module_layout(struct module *mod,
 }
 EXPORT_SYMBOL(module_layout);
 #endif
+
+#ifdef CONFIG_KGDB_KDB
+int kdb_lsmod(int argc, const char **argv)
+{
+	struct module *mod;
+
+	if (argc != 0)
+		return KDB_ARGCOUNT;
+
+	kdb_printf("Module                  Size  modstruct     Used by\n");
+	list_for_each_entry(mod, &modules, list) {
+		if (mod->state == MODULE_STATE_UNFORMED)
+			continue;
+
+		kdb_printf("%-20s%8u  0x%px ", mod->name,
+			   mod->core_layout.size, (void *)mod);
+#ifdef CONFIG_MODULE_UNLOAD
+		kdb_printf("%4d ", module_refcount(mod));
+#endif
+		if (mod->state == MODULE_STATE_GOING)
+			kdb_printf(" (Unloading)");
+		else if (mod->state == MODULE_STATE_COMING)
+			kdb_printf(" (Loading)");
+		else
+			kdb_printf(" (Live)");
+		kdb_printf(" 0x%px", mod->core_layout.base);
+
+#ifdef CONFIG_MODULE_UNLOAD
+		{
+			struct module_use *use;
+			kdb_printf(" [ ");
+			list_for_each_entry(use, &mod->source_list,
+					    source_list)
+				kdb_printf("%s ", use->target->name);
+			kdb_printf("]\n");
+		}
+#endif
+	}
+
+	return 0;
+}
+#endif	/* CONFIG_KGDB_KDB */