Re: [PATCH v7 25/39] arm64/signal: Expose GCS state in signal frames

[Thiago Jung Bauermann]

Mark Brown <broonie@xxxxxxxxxx> writes:

> +static int preserve_gcs_context(struct gcs_context __user *ctx)
> +{
> +	int err = 0;
> +	u64 gcspr;
> +
> +	/*
> +	 * We will add a cap token to the frame, include it in the
> +	 * GCSPR_EL0 we report to support stack switching via
> +	 * sigreturn.
> +	 */
> +	gcs_preserve_current_state();
> +	gcspr = current->thread.gcspr_el0;
> +	if (task_gcs_el0_enabled(current))
> +		gcspr -= 8;
> +
> +	__put_user_error(GCS_MAGIC, &ctx->head.magic, err);
> +	__put_user_error(sizeof(*ctx), &ctx->head.size, err);
> +	__put_user_error(gcspr, &ctx->gcspr, err);
> +	__put_user_error(current->thread.gcs_el0_mode,
> +			 &ctx->features_enabled, err);

Other preserve_<foo>_context() functions zero the reserved fields in
ctx. I suggest doing the same here. It helps with backward
compatibility.

> +
> +	return err;
> +}


-- 
Thiago