[PATCH] modules: add version and srcversion to sysfs

This patch adds version and srcversion files to
/sys/module/${modulename} containing the version and srcversion fields
of the module's modinfo section (if present).

/sys/module/e1000
|-- srcversion
`-- version

This patch differs slightly from the version posted in January, as it
now uses the new kstrdup() call in -mm.

Why put this in sysfs?

a) Tools like DKMS, which deal with changing out individual kernel
   modules without replacing the whole kernel, can behave smarter if they
   can tell the version of a given module.  The autoinstaller feature, for
   example, which determines if your system has a "good" version of a
   driver (i.e.  if the one provided by DKMS has a newer verson than that
   provided by the kernel package installed), and to automatically compile
   and install a newer version if DKMS has it but your kernel doesn't yet
   have that version.

b) Because sysadmins manually, or with tools like DKMS, can switch out
   modules on the file system, you can't count on 'modinfo foo.ko', which
   looks at /lib/modules/${kernelver}/...  actually matching what is loaded
   into the kernel already.  Hence asking sysfs for this.

c) as the unbind-driver-from-device work takes shape, it will be
   possible to rebind a driver that's built-in (no .ko to modinfo for the
   version) to a newly loaded module.  sysfs will have the
   currently-built-in version info, for comparison.

d) tech support scripts can then easily grab the version info for what's
   running presently - a question I get often.

There has been renewed interest in this patch on linux-scsi by driver
authors.

As the idea originated from GregKH, I leave his Signed-off-by: intact,
though the implementation is nearly completely new.  Compiled and run on
x86 and x86_64.

From: Matthew Dobson <colpatch@us.ibm.com>

      build fix

From: Thierry Vignaud <tvignaud@mandriva.com>

      build fix

From: Matthew Dobson <colpatch@us.ibm.com>

      warning fix
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>
Signed-off-by: Matt Domsch <Matt_Domsch@dell.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/module.h

@@ -51,6 +51,9 @@ struct module_attribute {
         ssize_t (*show)(struct module_attribute *, struct module *, char *);
         ssize_t (*store)(struct module_attribute *, struct module *,
 			 const char *, size_t count);
+	void (*setup)(struct module *, const char *);
+	int (*test)(struct module *);
+	void (*free)(struct module *);
 };
 
 struct module_kobject
@@ -239,6 +242,8 @@ struct module
 	/* Sysfs stuff. */
 	struct module_kobject mkobj;
 	struct module_param_attrs *param_attrs;
+	const char *version;
+	const char *srcversion;
 
 	/* Exported symbols */
 	const struct kernel_symbol *syms;

kernel/module.c

@@ -35,6 +35,7 @@
 #include <linux/notifier.h>
 #include <linux/stop_machine.h>
 #include <linux/device.h>
+#include <linux/string.h>
 #include <asm/uaccess.h>
 #include <asm/semaphore.h>
 #include <asm/cacheflush.h>
@@ -370,6 +371,43 @@ static inline void percpu_modcopy(void *pcpudst, const void *src,
 #endif /* CONFIG_SMP */
 
 #ifdef CONFIG_MODULE_UNLOAD
+#define MODINFO_ATTR(field)	\
+static void setup_modinfo_##field(struct module *mod, const char *s)  \
+{                                                                     \
+	mod->field = kstrdup(s, GFP_KERNEL);                          \
+}                                                                     \
+static ssize_t show_modinfo_##field(struct module_attribute *mattr,   \
+	                struct module *mod, char *buffer)             \
+{                                                                     \
+	return sprintf(buffer, "%s\n", mod->field);                   \
+}                                                                     \
+static int modinfo_##field##_exists(struct module *mod)               \
+{                                                                     \
+	return mod->field != NULL;                                    \
+}                                                                     \
+static void free_modinfo_##field(struct module *mod)                  \
+{                                                                     \
+        kfree(mod->field);                                            \
+        mod->field = NULL;                                            \
+}                                                                     \
+static struct module_attribute modinfo_##field = {                    \
+	.attr = { .name = __stringify(field), .mode = 0444,           \
+		  .owner = THIS_MODULE },                             \
+	.show = show_modinfo_##field,                                 \
+	.setup = setup_modinfo_##field,                               \
+	.test = modinfo_##field##_exists,                             \
+	.free = free_modinfo_##field,                                 \
+};
+
+MODINFO_ATTR(version);
+MODINFO_ATTR(srcversion);
+
+static struct module_attribute *modinfo_attrs[] = {
+	&modinfo_version,
+	&modinfo_srcversion,
+	NULL,
+};
+
 /* Init the unload section of the module. */
 static void module_unload_init(struct module *mod)
 {
@@ -1031,6 +1069,32 @@ static void module_remove_refcnt_attr(struct module *mod)
 }
 #endif
 
+#ifdef CONFIG_MODULE_UNLOAD
+static int module_add_modinfo_attrs(struct module *mod)
+{
+	struct module_attribute *attr;
+	int error = 0;
+	int i;
+
+	for (i = 0; (attr = modinfo_attrs[i]) && !error; i++) {
+		if (!attr->test ||
+		    (attr->test && attr->test(mod)))
+			error = sysfs_create_file(&mod->mkobj.kobj,&attr->attr);
+	}
+	return error;
+}
+
+static void module_remove_modinfo_attrs(struct module *mod)
+{
+	struct module_attribute *attr;
+	int i;
+
+	for (i = 0; (attr = modinfo_attrs[i]); i++) {
+		sysfs_remove_file(&mod->mkobj.kobj,&attr->attr);
+		attr->free(mod);
+	}
+}
+#endif
 
 static int mod_sysfs_setup(struct module *mod,
 			   struct kernel_param *kparam,
@@ -1056,6 +1120,12 @@ static int mod_sysfs_setup(struct module *mod,
 	if (err)
 		goto out_unreg;
 
+#ifdef CONFIG_MODULE_UNLOAD
+	err = module_add_modinfo_attrs(mod);
+	if (err)
+		goto out_unreg;
+#endif
+
 	return 0;
 
 out_unreg:
@@ -1066,6 +1136,9 @@ static int mod_sysfs_setup(struct module *mod,
 
 static void mod_kobject_remove(struct module *mod)
 {
+#ifdef CONFIG_MODULE_UNLOAD
+	module_remove_modinfo_attrs(mod);
+#endif
 	module_remove_refcnt_attr(mod);
 	module_param_sysfs_remove(mod);
 
@@ -1311,6 +1384,23 @@ static char *get_modinfo(Elf_Shdr *sechdrs,
 	return NULL;
 }
 
+#ifdef CONFIG_MODULE_UNLOAD
+static void setup_modinfo(struct module *mod, Elf_Shdr *sechdrs,
+			  unsigned int infoindex)
+{
+	struct module_attribute *attr;
+	int i;
+
+	for (i = 0; (attr = modinfo_attrs[i]); i++) {
+		if (attr->setup)
+			attr->setup(mod,
+				    get_modinfo(sechdrs,
+						infoindex,
+						attr->attr.name));
+	}
+}
+#endif
+
 #ifdef CONFIG_KALLSYMS
 int is_exported(const char *name, const struct module *mod)
 {
@@ -1615,6 +1705,11 @@ static struct module *load_module(void __user *umod,
 	/* Set up license info based on the info section */
 	set_license(mod, get_modinfo(sechdrs, infoindex, "license"));
 
+#ifdef CONFIG_MODULE_UNLOAD
+	/* Set up MODINFO_ATTR fields */
+	setup_modinfo(mod, sechdrs, infoindex);
+#endif
+
 	/* Fix up syms, so that st_value is a pointer to location. */
 	err = simplify_symbols(sechdrs, symindex, strtab, versindex, pcpuindex,
 			       mod);