Re: [Xen-devel] [PATCH] [RFC] xsm: add a default policy to .init.data

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 23/05/16 15:51, Daniel De Graaf wrote:
> diff --git a/xen/xsm/xsm_core.c b/xen/xsm/xsm_core.c
> index 634ec98..af1d86f 100644
> --- a/xen/xsm/xsm_core.c
> +++ b/xen/xsm/xsm_core.c
> @@ -47,6 +47,17 @@ static void __init do_xsm_initcalls(void)
>      }
>  }
>  
> +extern char __xsm_init_policy_start[], __xsm_init_policy_end[];
> +
> +static void __init xsm_policy_init(void)
> +{
> +    if ( policy_size == 0 )
> +    {
> +        policy_buffer = __xsm_init_policy_start;
> +        policy_size = __xsm_init_policy_end - __xsm_init_policy_start;
> +    }

Logic like this is slightly problematic if there is no policy.

With these changes, we presumably always expect to have an embedded policy.

It would be cleaner to have a linker ASSERT(__xsm_init_policy_start !=
__xsm_init_policy_end) to guarentee that something is present, at which
point policy_buffer can unilaterally point at __xsm_init_policy_start,
and size can be initialised to __xsm_init_policy_end -
__xsm_init_policy_start.

~Andrew

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