Re: [XEN PATCH v6 17/31] build: convert binfile use to if_changed

[Jan Beulich <jbeulich@xxxxxxxx>]

On 12.07.2021 18:32, Anthony PERARD wrote:
> On Wed, Jul 07, 2021 at 05:48:57PM +0200, Jan Beulich wrote:
>> On 01.07.2021 16:09, Anthony PERARD wrote:
>>> --- a/xen/common/Makefile
>>> +++ b/xen/common/Makefile
>>> @@ -80,8 +80,12 @@ config.gz: $(CONF_FILE)
>>>  
>>>  config_data.o: config.gz
>>>  
>>> -config_data.S: $(BASEDIR)/tools/binfile
>>> -   $(SHELL) $(BASEDIR)/tools/binfile $@ config.gz xen_config_data
>>> +quiet_cmd_binfile = BINFILE $@
>>> +cmd_binfile = $(SHELL) $< $@ config.gz xen_config_data
>>
>> This is an abuse of $< which I consider overly confusing:
>> $(BASEDIR)/tools/binfile is not the input file to the rule. Instead
>> the script generates an assembly file "out of thin air", with not
>> input files at all. The rule and ...
>>
>>> +config_data.S: $(BASEDIR)/tools/binfile FORCE
>>
>> ... dependency shouldn't give a different impression. What would
>> be nice (without having checked how difficult this might be) would
>> be if quiet_cmd_binfile and cmd_binfile could move to xen/Rules.mk
>> and merely be used from here (and the other location, where the
>> same concern obviously applies).
> 
> I've though of having cmd_binfile in Rules.mk, but it's made more
> complicated by having a "-i" flag used in flask/.
> 
> So one things I've writen was:
> 
> config_data.S: $(BASEDIR)/tools/binfile FORCE
>        $(call if_changed,binfile,,config.gz xen_config_data)
> flask-policy.S: $(BASEDIR)/tools/binfile FORCE
>        $(call if_changed,binfile,-i,policy.bin xsm_flask_init_policy)
> 
> with:
> cmd_binfile = $(SHELL) $(BASEDIR)/tools/binfile $(2) $@ $(3)
> 
> I thought this would be confusing, so I avoid it.

Indeed that's why I did write "without having checked how difficult
this might be", because I definitely didn't want to suggest such
anomalies to get introduced. It's unhelpful that options have to
come first.

> But maybe with the lists of flags at the end, it would be better:
>    $(call if_changed,binfile,policy.bin xsm_flask_init_policy,-i)

Yes, this is a little better imo, but still not pretty.

> Still want to move cmd_binfile to Rules.mk?

I'd still like it to be moved, but without resulting in a rule
that's not consistent with others. Maybe we should have a
BINFILE_FLAGS variable (paralleling e.g. CFLAGS)?

Jan