Re: [PATCH v2 6/7] flask: drop dead compat translation code

[Jan Beulich <jbeulich@suse.com>]

On 14.07.2020 16:58, Roger Pau Monné wrote:
> On Wed, Jul 01, 2020 at 12:28:07PM +0200, Jan Beulich wrote:
>> Translation macros aren't needed at all (or else a devicetree_label
>> entry would have been missing), and userlist has been removed quite some
>> time ago.
>>
>> No functional change.
>>
>> Signed-off-by: Jan Beulich <jbeulich@suse.com>
>>
>> --- a/xen/include/xlat.lst
>> +++ b/xen/include/xlat.lst
>> @@ -148,14 +148,11 @@
>>  ?	xenoprof_init			xenoprof.h
>>  ?	xenoprof_passive		xenoprof.h
>>  ?	flask_access			xsm/flask_op.h
>> -!	flask_boolean			xsm/flask_op.h
>>  ?	flask_cache_stats		xsm/flask_op.h
>>  ?	flask_hash_stats		xsm/flask_op.h
>> -!	flask_load			xsm/flask_op.h
>>  ?	flask_ocontext			xsm/flask_op.h
>>  ?	flask_peersid			xsm/flask_op.h
>>  ?	flask_relabel			xsm/flask_op.h
>>  ?	flask_setavc_threshold		xsm/flask_op.h
>>  ?	flask_setenforce		xsm/flask_op.h
>> -!	flask_sid_context		xsm/flask_op.h
>>  ?	flask_transition		xsm/flask_op.h
> 
> Shouldn't those become checks then?

No, checking will never succeed for structures containing
XEN_GUEST_HANDLE(). But there's no point in generating xlat macros
when they're never used. There are two fundamentally different
strategies for handling the compat hypercalls: One is to wrap a
translation layer around the native hypercall. That's where the
xlat macros come into play. The other, used here, is to compile
the entire hypercall function a second time, arranging for the
compat structures to get used in place of the native ones. There
are no xlat macros involved here, all that's needed are correctly
translated structures. (For completeness, x86's MCA hypercall
uses yet another, quite adhoc strategy for handling, but also not
involving any xlat macro use. Hence the consideration there to
possibly drop the respective lines from the file here.)

Jan