[Buildroot] [PATCH v3 1/3] Makefile: add tainting support

[Angelo Compagnucci]

Hi Thomas,

On Wed, Sep 5, 2018 at 9:37 PM, Thomas Petazzoni
<thomas.petazzoni at bootlin.com> wrote:
> Hello,
>
> +Yann/Arnout in Cc.
>
> On Wed,  5 Sep 2018 18:06:34 +0200, Angelo Compagnucci wrote:
>
>> diff --git a/package/pkg-generic.mk b/package/pkg-generic.mk
>> index 91b61c6..bcb4acd 100644
>> --- a/package/pkg-generic.mk
>> +++ b/package/pkg-generic.mk
>> @@ -551,6 +551,10 @@ ifndef $(2)_REDISTRIBUTE
>>   endif
>>  endif
>>
>> +ifdef $(2)_TAINTS
>> +BR2_TAINTED_BY+=$$($(2)_RAWNAME)
>> +endif
>
> I was almost going to apply and push this, but then I found a fairly
> major problem. With your implementation, as soon as a package sets
> <pkg>_TAINTS = YES, it will be part of the BR2_TAINTED_BY list,
> regardless of whether the package is enabled or not.
>
> It happens to work OK with nodejs, because the NODEJS_TAINTS = YES is
> inside a condition that NODEJS_MODULES_LIST != "". However, if you put
> NODEJS_TAINTS = YES outside of that condition in nodejs.mk, you will
> see that the build is always tainted by nodejs, regardless of whether
> nodejs is enabled or not. Not good.

Thank you so much for finding this.

> This can easily be fixed by moving the BR2_TAINTED_BY += line inside
> the:
>
>   ifeq ($$($$($(2)_KCONFIG_VAR)),y)
>
> condition, which is true only when the package is really enabled.

Yes, it works like a charm!

> However, this only works for target packages. What about host
> packages ? Can they taint the build ? If so, how do we handle that ?
>
> When I was about to apply, I had added something like this in
> pkg-generic.mk:
>
> ifndef $(2)_TAINTS
>  ifdef $(3)_TAINTS
>   $(2)_TAINTS = $$($(3)_TAINTS)
>  endif
> endif
>
> so that HOST_<pkg>_TAINTS is automatically defined to the same value as
> <pkg>_TAINTS. However, we have no way to know if a host package is
> enabled or not, since most host packages don't have any
> corresponding Config.in option.
>
> So: do we care about host packages for "tainting" ? If we do care, how
> do we handle this ?

I think we can demand the decision to when we will have a host package
that needs tainting support.

Moreover, I don't think the demand for host packages that needs
tainting support will be high in the future.

I'll send an updated patch.

>
> Best regards,
>
> Thomas
> --
> Thomas Petazzoni, CTO, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com