Re: [PATCH v10 1/9] mm: Introduce memfd_restricted system call to create restricted user memory

[Chao Peng]

> > int restrictedmem_bind(struct file *file, pgoff_t start, pgoff_t end,
> >                    struct restrictedmem_notifier *notifier, bool exclusive)
> > {
> >     struct restrictedmem *rm = file->f_mapping->private_data;
> >     int ret = -EINVAL;
> > 
> >     down_write(&rm->lock);
> > 
> >     /* Non-exclusive mappings are not yet implemented. */
> >     if (!exclusive)
> >             goto out_unlock;
> > 
> >     if (!xa_empty(&rm->bindings)) {
> >             if (exclusive != rm->exclusive)
> >                     goto out_unlock;
> > 
> >             if (exclusive && xa_find(&rm->bindings, &start, end, 
> > XA_PRESENT))
> >                     goto out_unlock;
> >     }
> > 
> >     xa_store_range(&rm->bindings, start, end, notifier, GFP_KERNEL);
> 
> 
> || ld: mm/restrictedmem.o: in function `restrictedmem_bind':
> mm/restrictedmem.c|295| undefined reference to `xa_store_range'

Right, xa_store_range() is only available for XARRAY_MULTI.

> 
> 
> This is missing:
> ===
> diff --git a/mm/Kconfig b/mm/Kconfig
> index f952d0172080..03aca542c0da 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -1087,6 +1087,7 @@ config SECRETMEM
>  config RESTRICTEDMEM
>         bool
>         depends on TMPFS
> +       select XARRAY_MULTI
> ===
> 
> Thanks,
> 
> 
> 
> >     rm->exclusive = exclusive;
> >     ret = 0;
> > out_unlock:
> >     up_write(&rm->lock);
> >     return ret;
> > }
> > EXPORT_SYMBOL_GPL(restrictedmem_bind);
> > 
> > void restrictedmem_unbind(struct file *file, pgoff_t start, pgoff_t end,
> >                       struct restrictedmem_notifier *notifier)
> > {
> >     struct restrictedmem *rm = file->f_mapping->private_data;
> > 
> >     down_write(&rm->lock);
> >     xa_store_range(&rm->bindings, start, end, NULL, GFP_KERNEL);
> >     synchronize_rcu();
> >     up_write(&rm->lock);
> > }
> > EXPORT_SYMBOL_GPL(restrictedmem_unbind);
> 
> -- 
> Alexey