module: show version information for built-in modules in sysfs

Currently only drivers that are built as modules have their versions
shown in /sys/module/<module_name>/version, but this information might
also be useful for built-in drivers as well. This especially important
for drivers that do not define any parameters - such drivers, if
built-in, are completely invisible from userspace.

This patch changes MODULE_VERSION() macro so that in case when we are
compiling built-in module, version information is stored in a separate
section. Kernel then uses this data to create 'version' sysfs attribute
in the same fashion it creates attributes for module parameters.

Signed-off-by: Dmitry Torokhov <dtor@vmware.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

2 files changed, 34 insertions, 0 deletions

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 68649336c4a..6ebb81030d2 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -364,6 +364,13 @@
                 VMLINUX_SYMBOL(__start___param) = .;                    \
                 *(__param)                                              \
                 VMLINUX_SYMBOL(__stop___param) = .;                     \
+        }                                                               \
+                                                                        \
+        /* Built-in module versions. */                                 \
+        __modver : AT(ADDR(__modver) - LOAD_OFFSET) {                   \
+                VMLINUX_SYMBOL(__start___modver) = .;                   \
+                *(__modver)                                             \
+                VMLINUX_SYMBOL(__stop___modver) = .;                    \
                 . = ALIGN((align));                                     \
                 VMLINUX_SYMBOL(__end_rodata) = .;                       \
         }                                                               \
diff --git a/include/linux/module.h b/include/linux/module.h
index 8b17fd8c790..50efcd3ae85 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -58,6 +58,12 @@ struct module_attribute {
         void (*free)(struct module *);
 };
 
+struct module_version_attribute {
+        struct module_attribute mattr;
+        const char *module_name;
+        const char *version;
+};
+
 struct module_kobject
 {
         struct kobject kobj;
@@ -161,7 +167,28 @@ extern struct module __this_module;
   Using this automatically adds a checksum of the .c files and the
   local headers in "srcversion".
 */
+
+#ifdef MODULE
 #define MODULE_VERSION(_version) MODULE_INFO(version, _version)
+#else
+#define MODULE_VERSION(_version)                                        \
+        extern ssize_t __modver_version_show(struct module_attribute *, \
+                                             struct module *, char *);  \
+        static struct module_version_attribute __modver_version_attr    \
+        __used                                                          \
+    __attribute__ ((__section__ ("__modver"),aligned(sizeof(void *)))) \
+        = {                                                             \
+                .mattr  = {                                             \
+                        .attr   = {                                     \
+                                .name   = "version",                    \
+                                .mode   = S_IRUGO,                      \
+                        },                                              \
+                        .show   = __modver_version_show,                \
+                },                                                      \
+                .module_name    = KBUILD_MODNAME,                       \
+                .version        = _version,                             \
+        }
+#endif
 
 /* Optional firmware file (or files) needed by the module
  * format is simply firmware file name.  Multiple firmware