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    SubjectRe: [PATCHv2 2/3] kernel: add support for live patching
    On Wed, Nov 19, 2014 at 04:27:39PM +0100, Miroslav Benes wrote:
    >
    > Hi,
    >
    > during rewriting our code I came across few more things. See below.
    >
    > On Sun, 16 Nov 2014, Seth Jennings wrote:
    >
    > [...]
    >
    > > +/******************************
    > > + * module notifier
    > > + *****************************/
    > > +
    > > +static void lpc_module_notify_coming(struct module *pmod,
    > > + struct lpc_object *obj)
    > > +{
    > > + struct module *mod = obj->mod;
    > > + int ret;
    > > +
    > > + pr_notice("applying patch '%s' to loading module '%s'\n",
    > > + mod->name, pmod->name);
    >
    > This looks strange. I guess the arguments should be swapped.

    Indeed, you are correct :)

    >
    > > + obj->mod = mod;
    >
    > And this is redundant.

    True again!

    >
    > > + ret = lpc_enable_object(pmod, obj);
    > > + if (ret)
    > > + pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
    > > + pmod->name, mod->name, ret);
    > > +}
    > > +
    > > +static void lpc_module_notify_going(struct module *pmod,
    > > + struct lpc_object *obj)
    > > +{
    > > + struct module *mod = obj->mod;
    > > + int ret;
    > > +
    > > + pr_notice("reverting patch '%s' on unloading module '%s'\n",
    > > + pmod->name, mod->name);
    > > + ret = lpc_disable_object(obj);
    > > + if (ret)
    > > + pr_warn("failed to revert patch '%s' on module '%s' (%d)\n",
    > > + pmod->name, mod->name, ret);
    > > + obj->mod = NULL;
    > > +}
    > > +
    > > +static int lpc_module_notify(struct notifier_block *nb, unsigned long action,
    > > + void *data)
    > > +{
    > > + struct module *mod = data;
    > > + struct lpc_patch *patch;
    > > + struct lpc_object *obj;
    > > +
    > > + mutex_lock(&lpc_mutex);
    > > +
    > > + if (action != MODULE_STATE_COMING && action != MODULE_STATE_GOING)
    > > + goto out;
    > > +
    > > + list_for_each_entry(patch, &lpc_patches, list) {
    > > + if (patch->state == LPC_DISABLED)
    > > + continue;
    > > + list_for_each_entry(obj, &patch->objs, list) {
    > > + if (strcmp(obj->name, mod->name))
    > > + continue;
    > > + if (action == MODULE_STATE_COMING) {
    > > + obj->mod = mod;
    > > + lpc_module_notify_coming(patch->mod, obj);
    > > + } else /* MODULE_STATE_GOING */
    > > + lpc_module_notify_going(patch->mod, obj);
    > > + break;
    > > + }
    > > + }
    > > +out:
    > > + mutex_unlock(&lpc_mutex);
    > > + return 0;
    > > +}
    >
    > [...]
    >
    > > +static struct lpc_object *lpc_create_object(struct kobject *root,
    > > + struct lp_object *userobj)
    > > +{
    > > + struct lpc_object *obj;
    > > + int ret;
    > > +
    > > + /* alloc */
    > > + obj = kzalloc(sizeof(*obj), GFP_KERNEL);
    > > + if (!obj)
    > > + return NULL;
    > > +
    > > + /* init */
    > > + INIT_LIST_HEAD(&obj->list);
    > > + obj->name = userobj->name;
    > > + obj->relocs = userobj->relocs;
    > > + obj->state = LPC_DISABLED;
    > > + /* obj->mod set by lpc_object_module_get() */
    > > + INIT_LIST_HEAD(&obj->funcs);
    >
    > There is nothing like lpc_object_module_get() in the code. Did you mean
    > lpc_find_object_module()?

    Yes, this comment should be removed or updated.

    Thanks,
    Seth

    >
    > Thank you,
    > --
    > Miroslav Benes
    > SUSE Labs


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