Re: [PATCH] thermal: core: Move initial num_trips assignment before memcpy()

Nathan Chancellor
2024-02-28T16:56:54Z

On Wed, Feb 28, 2024 at 08:41:07AM +0000, Lukasz Luba wrote:
> Hi Nathan and Kees,
>
> On 2/27/24 17:00, Kees Cook wrote:
> > On Tue, Feb 27, 2024 at 05:47:44PM +0100, Daniel Lezcano wrote:
> > > Ok my misunderstanding was I thought sizeof() was calling _bdos under the
> > > hood, so when calling sizeof(flex_array), it was returning the computed size
> > > inferring from the __counted_by field.
> >
> > Yeah, sizeof() has a very limited scope. __builtin_object_size() has
> > more flexibility (via the 2nd argument, "type"), but it was still
> > compile-time only. __builtin_dynamic_object_size() was added to bring
> > runtime evaluations into the mix (initially to support the alloc_size
> > attribute, and now includes the counted_by attribute too).
> >
>
> Thanks for your earlier emails explaining these stuff.
> Do you have maybe some presentation about those features
> for the kernel (ideally w/ a video from some conference)?

I think Kees's 2022 and 2023 talks at LPC are a good place to start:

https://youtu.be/tQwv79i02ks?si=Nj9hpvmQwPB4K3Y4&t=452
https://youtu.be/OEFFqhP5sts?si=u6RnOP641S8FkouD&t=614

https://outflux.net/slides/2022/lpc/features.pdf
https://outflux.net/slides/2023/lpc/features.pdf

Cheers,
Nathan