linux-kernel - [PATCH 1/2] module: add a function to add module references

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Date:   Fri, 29 Apr 2022 07:31:15 +0100
From:   Mauro Carvalho Chehab <mchehab@...nel.org>
To:     Luis Chamberlain <mcgrof@...nel.org>
Cc:     mauro.chehab@...el.com, Mauro Carvalho Chehab <mchehab@...nel.org>,
        "Kai Vehmanen" <kai.vehmanen@...el.com>,
        "Lucas De Marchi" <lucas.demarchi@...el.com>,
        "Pierre-Louis Bossart" <pierre-louis.bossart@...el.com>,
        dri-devel@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, linux-modules@...r.kernel.org,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Dan Williams <dan.j.williams@...el.com>
Subject: [PATCH 1/2] module: add a function to add module references

Sometimes, device drivers are bound using indirect references,
which is not visible when looking at /proc/modules or lsmod.

Add a function to allow setting up module references for such
cases.

Reviewed-by: Dan Williams <dan.j.williams@...el.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@...nel.org>
---

See [PATCH 0/2] at: https://lore.kernel.org/all/cover.1651212016.git.mchehab@kernel.org/

 include/linux/module.h |  7 +++++++
 kernel/module/main.c   | 31 +++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/include/linux/module.h b/include/linux/module.h
index 46d4d5f2516e..be74f807e41d 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -596,6 +596,8 @@ static inline bool within_module(unsigned long addr, const struct module *mod)
 /* Search for module by name: must be in a RCU-sched critical section. */
 struct module *find_module(const char *name);
 
+int module_add_named_dependency(const char *name, struct module *this);
+
 /* Returns 0 and fills in value, defined and namebuf, or -ERANGE if
    symnum out of range. */
 int module_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
@@ -772,6 +774,11 @@ static inline int lookup_module_symbol_attrs(unsigned long addr, unsigned long *
 	return -ERANGE;
 }
 
+static inline int module_add_named_dependency(const char *name, struct module *this)
+{
+	return 0;
+}
+
 static inline int module_get_kallsym(unsigned int symnum, unsigned long *value,
 					char *type, char *name,
 					char *module_name, int *exported)
diff --git a/kernel/module/main.c b/kernel/module/main.c
index 05a42d8fcd7a..dbd577ccc38c 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -631,6 +631,37 @@ static int ref_module(struct module *a, struct module *b)
 	return 0;
 }
 
+int module_add_named_dependency(const char *name, struct module *this)
+{
+	struct module *mod;
+	int ret;
+
+	if (!name || !this || !this->name) {
+		return -EINVAL;
+	}
+
+	mutex_lock(&module_mutex);
+	mod = find_module(name);
+	if (!mod) {
+		ret = -EINVAL;
+		goto ret;
+	}
+
+	ret = ref_module(this, mod);
+	if (ret)
+		goto ret;
+
+#ifdef CONFIG_MODULE_UNLOAD
+	ret = sysfs_create_link(mod->holders_dir,
+				&this->mkobj.kobj, this->name);
+#endif
+
+ret:
+	mutex_unlock(&module_mutex);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(module_add_named_dependency);
+
 /* Clear the unload stuff of the module. */
 static void module_unload_free(struct module *mod)
 {
-- 
2.35.1