[PATCH] module: add modinfo support for all built-in modules

[Denis Cheng]

the current modinfo support is for external modules only, it provided module
information under /sys/module/<XYZ>/, such as verion, ...;
now some application(such as iscsid of open-iscsi) has been designed to
use this module information; but built-in modules don't have modinfo support,
so these apps would break if modules they depend on are compiled built-in.

this patch add modinfo support for all built-in modules, so now no matter
whether modules they depends on are built-in or external, modules' information
could always be accessed from /sys/module/<XYZ>/version, apps won't break.

Signed-off-by: Denis Cheng <crquan@xxxxxxxxx>
---
 include/asm-generic/vmlinux.lds.h |    7 ++
 include/linux/moduleparam.h       |   18 ++++-
 kernel/module.c                   |  147 +++++++++++++++++++++++++++++++++++++
 3 files changed, 170 insertions(+), 2 deletions(-)

diff --git a/include/asm-generic/vmlinux.lds.h
b/include/asm-generic/vmlinux.lds.h
index 9f584cc..896f0fe 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -137,6 +137,13 @@
 		VMLINUX_SYMBOL(__start___param) = .;			\
 		*(__param)						\
 		VMLINUX_SYMBOL(__stop___param) = .;			\
+	}								\
+									\
+	/* Built-in module information. */				\
+	.modinfo : AT(ADDR(.modinfo) - LOAD_OFFSET) {			\
+		VMLINUX_SYMBOL(__start___modinfo) = .;			\
+		*(.modinfo)						\
+		VMLINUX_SYMBOL(__stop___modinfo) = .;			\
 		VMLINUX_SYMBOL(__end_rodata) = .;			\
 	}								\
 									\
diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h
index 13410b2..86ddbd4 100644
--- a/include/linux/moduleparam.h
+++ b/include/linux/moduleparam.h
@@ -13,16 +13,30 @@
 #define MODULE_PARAM_PREFIX KBUILD_MODNAME "."
 #endif

-#ifdef MODULE
 #define ___module_cat(a,b) __mod_ ## a ## b
 #define __module_cat(a,b) ___module_cat(a,b)
+
+#ifdef MODULE
 #define __MODULE_INFO(tag, name, info)					  \
 static const char __module_cat(name,__LINE__)[]				  \
   __attribute_used__							  \
   __attribute__((section(".modinfo"),unused)) = __stringify(tag) "=" info
 #else  /* !MODULE */
-#define __MODULE_INFO(tag, name, info)
+struct kernel_modinfo {
+	char *modname;
+	char *tag;
+	char *info;
+};
+#define __MODULE_INFO(tag, name, info)					  \
+static const struct kernel_modinfo __module_cat(name, __LINE__)	  \
+  __attribute_used__							  \
+  __attribute__((section(".modinfo"), unused)) =			  \
+  { KBUILD_MODNAME, __stringify(tag), info }
+
+extern const struct kernel_modinfo __start___modinfo[], __stop___modinfo[];
+
 #endif
+
 #define __MODULE_PARM_TYPE(name, _type)					  \
   __MODULE_INFO(parmtype, name##type, #name ":" _type)

diff --git a/kernel/module.c b/kernel/module.c
index c2e3e2e..9828918 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2609,3 +2609,150 @@ void module_update_markers(struct module
*probe_module, int *refcount)
 	mutex_unlock(&module_mutex);
 }
 #endif
+
+#ifdef CONFIG_SYSFS
+struct modinfo_attribute {
+	struct module_attribute mattr;
+	const struct kernel_modinfo *modinfo;
+};
+
+struct module_modinfo_attrs {
+	struct attribute_group grp;
+	struct modinfo_attribute attrs[0];
+};
+
+#define to_modinfo_attr(n) container_of(n, struct modinfo_attribute, mattr)
+
+static ssize_t modinfo_attr_show(struct module_attribute *mattr,
+		struct module *mod, char *buf)
+{
+	const struct kernel_modinfo *km = to_modinfo_attr(mattr)->modinfo;
+	return snprintf(buf, PAGE_SIZE, "%s\n", km->info);
+}
+
+/* skip the parameters' description in .modinfo */
+static __init int modinfo_skip(char *name)
+{
+	return (strlen(name) == 4 && !strncmp(name, "parm", 4)) ||
+		(strlen(name) == 8 && !strncmp(name, "parmtype", 8));
+}
+
+static __init void modinfo_sysfs_setup(struct module_kobject *mk,
+		  const struct kernel_modinfo km_begin[],
+		  unsigned int num_params)
+{
+	struct module_modinfo_attrs *mp;
+	unsigned int valid_attrs = 0;
+	unsigned int i, size[2];
+	struct modinfo_attribute *pattr;
+	struct attribute **gattr;
+
+	for (i = 0; i < num_params; ++i) {
+		if (!modinfo_skip(km_begin[i].tag))
+			valid_attrs++;
+	}
+
+	if (!valid_attrs)
+		return;
+
+	size[0] = ALIGN(sizeof(*mp) +
+			valid_attrs * sizeof(mp->attrs[0]),
+			sizeof(mp->grp.attrs[0]));
+	size[1] = (valid_attrs + 1) * sizeof(mp->grp.attrs[0]);
+
+	mp = kzalloc(size[0] + size[1], GFP_KERNEL);
+	if (!mp)
+		return;
+
+	mp->grp.attrs = (void *)mp + size[0];
+
+	pattr = &mp->attrs[0];
+	gattr = &mp->grp.attrs[0];
+	for (i = 0; i < valid_attrs; i++) {
+		const struct kernel_modinfo *km = &km_begin[i];
+		if (!modinfo_skip(km_begin[i].tag)) {
+			pattr->modinfo = km;
+			pattr->mattr.show = modinfo_attr_show;
+			pattr->mattr.attr.name = km->tag;
+			pattr->mattr.attr.mode = S_IRUGO;
+			*(gattr++) = &(pattr++)->mattr.attr;
+		}
+	}
+
+	if (sysfs_create_group(&mk->kobj, &mp->grp))
+		kfree(mp);
+}
+
+static void __init kernel_modinfo_sysfs_setup(const char *modname,
+		const struct kernel_modinfo km_begin[],
+		unsigned int num_params)
+{
+	struct kobject *mkobj;
+	struct module_kobject *mk;
+	int ret;
+
+	mkobj = kset_find_obj(&module_subsys, modname);
+
+	if (mkobj)
+		mk = container_of(mkobj, struct module_kobject, kobj);
+	else {
+		mk = kzalloc(sizeof(struct module_kobject), GFP_KERNEL);
+
+		kobj_set_kset_s(mk, module_subsys);
+		kobject_set_name(&mk->kobj, modname);
+		kobject_init(&mk->kobj);
+		ret = kobject_add(&mk->kobj);
+		if (ret) {
+			printk(KERN_ERR "Module '%s' failed to be added to"
+					" sysfs, error number %d\n",
+					modname, ret);
+			printk(KERN_ERR	"The system will be unstable now.\n");
+			return;
+		}
+	}
+
+	modinfo_sysfs_setup(mk, km_begin, num_params);
+
+	if (mkobj) {
+		/* kset_find_obj incremental a reference on mkobj */
+		kobject_put(mkobj);
+	} else
+		kobject_uevent(&mk->kobj, KOBJ_ADD);
+}
+
+/*
+ * module_info_sysfs_init is for built-in modules
+ *
+ * __initcall("6") is later than subsys_init
+ */
+static int __init builtin_modinfo_sysfs_init(void)
+{
+	const struct kernel_modinfo *km, *km_begin = NULL;
+	unsigned int count = 0;
+	char *modname = NULL;
+
+	for (km = __start___modinfo; km < __stop___modinfo; km++) {
+		/* new kbuild_modname? */
+		if (km->modname != modname) {
+			/* add a new kobject for previous kernel_modinfo . */
+			if (count)
+				kernel_modinfo_sysfs_setup(modname,
+						km_begin,
+						count);
+
+			modname = km->modname;
+			count = 0;
+			km_begin = km;
+		}
+		count++;
+	}
+
+	/* last kernel_modinfo need to be registered as well */
+	if (count)
+		kernel_modinfo_sysfs_setup(modname, km_begin, count);
+
+	return 0;
+}
+__initcall(builtin_modinfo_sysfs_init);
+
+#endif
-- 
1.5.3.5

-- 
Denis Cheng
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