param: add a free hook to kernel_param_ops.

This allows us to generalize the KPARAM_KMALLOCED flag, by calling a function
on every parameter when a module is unloaded.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Tested-by: Phil Carmody <ext-phil.2.carmody@nokia.com>

2 files changed, 18 insertions, 1 deletions

diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h
index 02e5090ce32f..9f51568f51c8 100644
--- a/include/linux/moduleparam.h
+++ b/include/linux/moduleparam.h
@@ -36,6 +36,8 @@ struct kernel_param_ops {
         int (*set)(const char *val, const struct kernel_param *kp);
         /* Returns length written or -errno.  Buffer is 4k (ie. be short!) */
         int (*get)(char *buffer, const struct kernel_param *kp);
+        /* Optional function to free kp->arg when module unloaded. */
+        void (*free)(void *arg);
 };
 
 /* Flag bits for kernel_param.flags */
diff --git a/kernel/params.c b/kernel/params.c
index a550698ae02d..458a09b886c4 100644
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -399,9 +399,20 @@ static int param_array_get(char *buffer, const struct kernel_param *kp)
         return off;
 }
 
+static void param_array_free(void *arg)
+{
+        unsigned int i;
+        const struct kparam_array *arr = arg;
+
+        if (arr->ops->free)
+                for (i = 0; i < (arr->num ? *arr->num : arr->max); i++)
+                        arr->ops->free(arr->elem + arr->elemsize * i);
+}
+
 struct kernel_param_ops param_array_ops = {
         .set = param_array_set,
         .get = param_array_get,
+        .free = param_array_free,
 };
 EXPORT_SYMBOL(param_array_ops);
 
@@ -634,7 +645,11 @@ void module_param_sysfs_remove(struct module *mod)
 
 void destroy_params(const struct kernel_param *params, unsigned num)
 {
-        /* FIXME: This should free kmalloced charp parameters.  It doesn't. */
+        unsigned int i;
+
+        for (i = 0; i < num; i++)
+                if (params[i].ops->free)
+                        params[i].ops->free(params[i].arg);
 }
 
 static void __init kernel_add_sysfs_param(const char *name,