Re: [PATCH bpf-next v5 7/9] selftests/bpf: Test kptr arrays and kptrs in nested struct fields.

[Eduard Zingerman <eddyz87@gmail.com>]

On Fri, 2024-05-10 at 14:59 -0700, Kui-Feng Lee wrote:
> 
> For the sake of completeness, would it be possible to create a test
> > case where there are several struct arrays following each other?
> > E.g. as below:
> > 
> > struct foo {
> >    ... __kptr *a;
> >    ... __kptr *b;
> > }
> > 
> > struct bar {
> >    ... __kptr *c;
> > }
> > 
> > struct {
> >    struct foo foos[3];
> >    struct bar bars[2];
> > }
> > 
> > Just to check that offset is propagated correctly.
> 
> Sure!

Great, thank you

> > Also, in the tests below you check that a pointer to some object could
> > be put into an array at different indexes. Tbh, I find it not very
> > interesting if we want to check that offsets are correct.
> > Would it be possible to create an array of object kptrs,
> > put specific references at specific indexes and somehow check which
> > object ended up where? (not necessarily 'bpf_cpumask').
> 
> Do you mean checking index in the way like the following code?
> 
>   if (array[0] != ref0 || array[1] != ref1 || array[2] != ref2 ....)
>     return err;

Probably, but I'd need your help here.
There goal is to verify that offsets of __kptr's in the 'info' array
had been set correctly. Where is this information is used later on?
E.g. I'd like to trigger some action that "touches" __kptr at index N
and verify that all others had not been "touched".
But this "touch" action has to use offset stored in the 'info'.

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