On Thu, Jun 01, 2017 at 02:25:24PM -0400, Joe Lawrence wrote:
> Add three exported API for livepatch modules:
>
> void *klp_shadow_attach(void *obj, char *var, gfp_t gfp, void *data);
> void klp_shadow_detach(void *obj, char *var);
> void *klp_shadow_get(void *obj, char *var);
>
> that implement "shadow" variables, which allow callers to associate new
> shadow fields to existing data structures.
>
> Signed-off-by: Joe Lawrence <joe.lawrence@xxxxxxxxxx>
Overall the patch looks good to me. It's a simple API but we've found
it to be very useful for certain patches.
One comment below:
> +void *klp_shadow_attach(void *obj, char *var, gfp_t gfp, void *data)
> +{
> + unsigned long flags;
> + struct klp_shadow *shadow;
> +
> + shadow = kmalloc(sizeof(*shadow), gfp);
> + if (!shadow)
> + return NULL;
> +
> + shadow->obj = obj;
> +
> + shadow->var = kstrdup(var, gfp);
> + if (!shadow->var) {
> + kfree(shadow);
> + return NULL;
> + }
> +
> + shadow->data = data;
> +
> + spin_lock_irqsave(&klp_shadow_lock, flags);
> + hash_add_rcu(klp_shadow_hash, &shadow->node, (unsigned long)obj);
> + spin_unlock_irqrestore(&klp_shadow_lock, flags);
> +
> + return shadow->data;
> +}
> +EXPORT_SYMBOL_GPL(klp_shadow_attach);
I wonder if we should worry about people misusing the API by calling
klp_shadow_attach() for a shadow variable that already exists. Maybe we
should add a check and return NULL if it already exists.
--
Josh
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