linux-kernel - [PATCH 02/13] module: add a module

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Date:   Thu, 21 Jan 2021 08:49:48 +0100
From:   Christoph Hellwig <hch@....de>
To:     Frederic Barrat <fbarrat@...ux.ibm.com>,
        Andrew Donnellan <ajd@...ux.ibm.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, Jessica Yu <jeyu@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jiri Kosina <jikos@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Petr Mladek <pmladek@...e.com>,
        Joe Lawrence <joe.lawrence@...hat.com>
Cc:     Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        dri-devel@...ts.freedesktop.org, live-patching@...r.kernel.org,
        linux-kbuild@...r.kernel.org
Subject: [PATCH 02/13] module: add a module_loaded helper

Add a helper that takes modules_mutex and uses find_module to check if a
given module is loaded.  This provides a better abstraction for the two
callers, and allows to unexport modules_mutex and find_module.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 drivers/gpu/drm/drm_fb_helper.c |  7 +------
 include/linux/module.h          |  3 +++
 kernel/module.c                 | 14 ++++++++++++--
 kernel/trace/trace_kprobe.c     |  4 +---
 4 files changed, 17 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 4b81195106875d..ce6d63ca75c32a 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -2508,13 +2508,8 @@ int __init drm_fb_helper_modinit(void)
 {
 #if defined(CONFIG_FRAMEBUFFER_CONSOLE_MODULE) && !defined(CONFIG_EXPERT)
 	const char name[] = "fbcon";
-	struct module *fbcon;
 
-	mutex_lock(&module_mutex);
-	fbcon = find_module(name);
-	mutex_unlock(&module_mutex);
-
-	if (!fbcon)
+	if (!module_loaded(name))
 		request_module_nowait(name);
 #endif
 	return 0;
diff --git a/include/linux/module.h b/include/linux/module.h
index 7a0bcb5b1ffccd..b4654f8a408134 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -589,6 +589,9 @@ static inline bool within_module(unsigned long addr, const struct module *mod)
 /* Search for module by name: must hold module_mutex. */
 struct module *find_module(const char *name);
 
+/* Check if a module is loaded. */
+bool module_loaded(const char *name);
+
 struct symsearch {
 	const struct kernel_symbol *start, *stop;
 	const s32 *crcs;
diff --git a/kernel/module.c b/kernel/module.c
index 4bf30e4b3eaaa1..619ea682e64cd1 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -88,7 +88,6 @@
  * (delete and add uses RCU list operations).
  */
 DEFINE_MUTEX(module_mutex);
-EXPORT_SYMBOL_GPL(module_mutex);
 static LIST_HEAD(modules);
 
 /* Work queue for freeing init sections in success case */
@@ -672,7 +671,18 @@ struct module *find_module(const char *name)
 	module_assert_mutex();
 	return find_module_all(name, strlen(name), false);
 }
-EXPORT_SYMBOL_GPL(find_module);
+
+bool module_loaded(const char *name)
+{
+	bool ret;
+
+	mutex_lock(&module_mutex);
+	ret = !!find_module(name);
+	mutex_unlock(&module_mutex);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(module_loaded);
 
 #ifdef CONFIG_SMP
 
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index e6fba1798771b4..c2e453f88bce70 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -124,9 +124,7 @@ static nokprobe_inline bool trace_kprobe_module_exist(struct trace_kprobe *tk)
 	if (!p)
 		return true;
 	*p = '\0';
-	mutex_lock(&module_mutex);
-	ret = !!find_module(tk->symbol);
-	mutex_unlock(&module_mutex);
+	ret = module_loaded(tk->symbol);
 	*p = ':';
 
 	return ret;
-- 
2.29.2