Date:	Fri, 18 Jan 2008 17:54:55 +0800
From:	"rae l" <crquan@...il.com>
To:	"Rusty Russell" <rusty@...tcorp.com.au>
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] module: add modinfo support for all built-in modules

On Jan 16, 2008 8:25 PM, Rusty Russell <rusty@...tcorp.com.au> wrote:
> I'd love to see patches.  module_parm showed it's possible, if messy.
>
> Thanks!
> Rusty.

here's the patch, I added .modinfo section to the vmlinux, to collect
built-in module information.

I have just define __MODULE_INFO to another meaning while
CONFIG_MODULES undefined
(modules compiled built-in), instead of nothing; and so the
MODULE_LICENSE, MODULE_AUTHOR,
MODULE_DESCRIPTION's meaning also changed, each macro would define one
struct kernel_modinfo
entry in the .modinfo section of vmlinux; and one __initcall converts
all these information to read-only
files under /sys/modules/<module-name>/...

but the MODULE_PARM_DESC macro is still different:
it generates entries with the same tag, that would confuse
sys_create_group, so I skipped them in the __initcall,
since the parameters had been in /sys/modules/<>/parameters/(with perm
non-zero) or didn't appear(with perm 0);
I think the parameter description might be only useful for external
module files, not needed in memory(under /sys/module/),
so a better solution is define MODULE_PARM_DESC to nothing while
CONFIG_MODULES undefined.

Another possible defect is that it compares two modname with
(km->modname != modname),
that depends on a gcc feature: keep same constant string only one copy
in the image,
this did work on my test machines, but I'm not sure it's standard or
not; and if not, I would change it to strcmp.

Apperantly this approach will increase the kernel image size. on a
moderate system(with 1.8MB bzImage),
this patch would increase vmlinux 46KB and after compression increase
bzImage 9.2KB.
and in the increment of vmlinux, the .modinfo section occupied 5.3KB
and others are constant strings.

However, the iscsid can now work well when scsi_transport_iscsi module
built-in without the problem refered in my former email.

please give comments.

>From 50831a260b1ad2c8b495854a58408c1fbc75a3fe Mon Sep 17 00:00:00 2001
From: Denis Cheng <crquan@...il.com>
Date: Fri, 18 Jan 2008 16:37:35 +0800
Subject: [PATCH] module: add modinfo support for all built-in modules

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@...il.com>
---
 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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