[PATCH v4 4/8] arm64: uaccess: Add additional userspace GCS accessors

[Catalin Marinas]

On Fri, Jul 18, 2025 at 11:37:36PM -0500, Jeremy Linton wrote:
> +/*
> + * Unlike put_user_gcs() above, the use of copy_from_user() may provide
> + * an opening for non GCS pages to be used to source data. Therefore this
> + * should only be used in contexts where that is acceptable.
> + */

Even in user space, the GCS pages can be read with normal loads, so
already usable as a data source if one wants to (not that it's of much
use). So not sure the comment here is needed.

> +static inline u64 load_user_gcs(unsigned long __user *addr, int *err)

Nitpick: name this get_user_gcs() for symmetry with put_user_gcs().

> +{
> +	unsigned long ret;
> +	u64 load = 0;
> +
> +	gcsb_dsync();

Might be worth a comment here, see the one in gcs_restore_signal().

> +	ret = copy_from_user(&load, addr, sizeof(load));
> +	if (ret != 0)
> +		*err = ret;
> +	return load;
> +}

Otherwise the patch looks fine:

Reviewed-by: Catalin Marinas <catalin.marinas at arm.com>