linux-kernel - Re: [PATCH v13 08/12] livepatch: Add atomic replace

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Date:   Fri, 23 Nov 2018 13:00:35 +0100 (CET)
From:   Miroslav Benes <mbenes@...e.cz>
To:     Petr Mladek <pmladek@...e.com>
cc:     Jiri Kosina <jikos@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jason Baron <jbaron@...mai.com>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        Evgenii Shatokhin <eshatokhin@...tuozzo.com>,
        live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jessica Yu <jeyu@...nel.org>
Subject: Re: [PATCH v13 08/12] livepatch: Add atomic replace

On Mon, 15 Oct 2018, Petr Mladek wrote:

> +static int klp_add_object_nops(struct klp_patch *patch,
> +			       struct klp_object *old_obj)
> +{
> +	struct klp_object *obj;
> +	struct klp_func *func, *old_func;
> +
> +	obj = klp_find_object(patch, old_obj);
> +
> +	if (!obj) {
> +		obj = klp_alloc_object_dynamic(old_obj->name);
> +		if (!obj)
> +			return -ENOMEM;
> +
> +		list_add(&obj->node, &patch->obj_list);
> +	}
> +
> +	klp_for_each_func(old_obj, old_func) {
> +		func = klp_find_func(obj, old_func);
> +		if (func)
> +			continue;
> +
> +		func = klp_alloc_func_nop(old_func, obj);
> +		if (!func)
> +			return -ENOMEM;
> +
> +		list_add(&func->node, &obj->func_list);
> +	}
> +
> +	return 0;
> +}

Maybe you should consider list_add_tail() here too.

> +
> +/*
> + * Add 'nop' functions which simply return to the caller to run
> + * the original function. The 'nop' functions are added to a
> + * patch to facilitate a 'replace' mode.
> + */
> +static int klp_add_nops(struct klp_patch *patch)
> +{
> +	struct klp_patch *old_patch;
> +	struct klp_object *old_obj;
> +	int err = 0;

The initialization is unnecessary.

> +	list_for_each_entry(old_patch, &klp_patches, list) {
> +		klp_for_each_object(old_patch, old_obj) {
> +			err = klp_add_object_nops(patch, old_obj);
> +			if (err)
> +				return err;
> +		}
> +	}
> +
> +	return 0;
> +}

Miroslav