Re: [Xen-devel] [PATCH] x86/hvm/viridian: zero and check vcpu context __pad field

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 30.03.16 at 12:32, <paul.durrant@xxxxxxxxxx> wrote:
> --- a/xen/arch/x86/hvm/viridian.c
> +++ b/xen/arch/x86/hvm/viridian.c
> @@ -824,6 +824,8 @@ static int viridian_save_vcpu_ctxt(struct domain *d, 
> hvm_domain_context_t *h)
>      for_each_vcpu( d, v ) {
>          struct hvm_viridian_vcpu_context ctxt;
>  
> +        memset(&ctxt, 0, sizeof(ctxt));

How about just adding an empty initializer to the declaration?

> @@ -834,6 +836,15 @@ static int viridian_save_vcpu_ctxt(struct domain *d, 
> hvm_domain_context_t *h)
>      return 0;
>  }
>  
> +static bool_t is_zero(void *p, size_t size)

At the very least this wants to be a pointer to const.

> +{
> +    while ( size-- )
> +        if ( *(uint8_t *)p++ != 0 )
> +            return 0;
> +
> +    return 1;
> +}
> +
>  static int viridian_load_vcpu_ctxt(struct domain *d, hvm_domain_context_t *h)
>  {
>      int vcpuid;
> @@ -851,6 +862,9 @@ static int viridian_load_vcpu_ctxt(struct domain *d, 
> hvm_domain_context_t *h)
>      if ( hvm_load_entry_zeroextend(VIRIDIAN_VCPU, h, &ctxt) != 0 )
>          return -EINVAL;
>  
> +    if ( !is_zero(&ctxt._pad, sizeof(ctxt._pad)) )
> +        return -EINVAL;

"memcmp(&ctx._pad, zero_page, sizeof(ctxt._pad))" would be an
alternative not requiring any new helper function.

Jan


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