Re: [PATCH for-4.16 v3] efi: fix alignment of function parameters in compat mode

[Jan Beulich <jbeulich@xxxxxxxx>]

On 19.11.2021 18:09, Ian Jackson wrote:
> Andrew Cooper writes ("Re: [PATCH for-4.16 v3] efi: fix alignment of function 
> parameters in compat mode"):
>> Some hardtabs appear to have slipped in.
> 
> Thanks.  Fixed.
> 
>> Jan gave a conditional R-by which permitted a change along these lines,
>> but he's left the office now too, so you'll have to take him up on that
>> offer if you want this committing before Monday.
> 
> Right.
> 
> FTAOD I think I have done what Jan approved, and Andy double checked
> that.  So I am about to push this.  For the record, final version
> below.

Right, thanks. Nevertheless I think for 4.17 we will want to ...

> --- a/xen/common/efi/runtime.c
> +++ b/xen/common/efi/runtime.c
> @@ -607,6 +607,9 @@ int efi_runtime_call(struct xenpf_efi_runtime_call *op)
>      break;
>  
>      case XEN_EFI_query_variable_info:
> +    {
> +        uint64_t max_store_size, remain_store_size, max_size;
> +
>          if ( op->misc & ~XEN_EFI_VARINFO_BOOT_SNAPSHOT )
>              return -EINVAL;
>  
> @@ -638,16 +641,36 @@ int efi_runtime_call(struct xenpf_efi_runtime_call *op)
>  
>          if ( !efi_enabled(EFI_RS) || (efi_rs->Hdr.Revision >> 16) < 2 )
>              return -EOPNOTSUPP;
> +
> +        /*
> +         * Bounce the variables onto the stack to make them 8 byte aligned 
> when
> +         * called from the compat handler, as their placement in
> +         * compat_pf_efi_runtime_call will make them 4 byte aligned instead 
> and
> +         * and compilers may validly complain.
> +         *
> +         * Note that while the function parameters are OUT only, copy the
> +         * values here anyway just in case. This is done regardless of 
> whether
> +         * called from the compat handler or not, as it's not worth the extra
> +         * logic to differentiate.
> +         */
> +        max_store_size = op->u.query_variable_info.max_store_size;
> +        remain_store_size = op->u.query_variable_info.remain_store_size;
> +        max_size = op->u.query_variable_info.max_size;

... eliminate these.

Jan