linux-kernel - Re: linux-next: build failure after merge of the origin tree

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Message-ID: <CAHk-=wjK8+12i8iDC41LXfZBcMjGsF+WyW_+ncPFmrexRT0yxw@mail.gmail.com>
Date:   Wed, 29 Jul 2020 16:43:04 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Stephen Rothwell <sfr@...b.auug.org.au>,
        Emese Revfy <re.emese@...il.com>,
        Kees Cook <keescook@...omium.org>
Cc:     Linux Next Mailing List <linux-next@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Willy Tarreau <w@....eu>
Subject: Re: linux-next: build failure after merge of the origin tree

On Wed, Jul 29, 2020 at 4:08 PM Stephen Rothwell <sfr@...b.auug.org.au> wrote:
>
> include/linux/random.h:123:24: error: variable 'net_rand_state' with 'latent_entropy' attribute must not be local
>   123 | DECLARE_PER_CPU(struct rnd_state, net_rand_state) __latent_entropy;

Hmm.

Ok, this shows a limitation of my allmodconfig testing (and all my
normal builds) - no plugins. So that problem wasn't as obvious as it
should have been.

That error isn't very helpful, in that I think it actually is very
wrong. The variable really isn't local at all.

I think what the plugin *means* by "local" is "automatic", and I think
it uses the wrong test for it. IOW, looking at the plugin, it does

                if (!TREE_STATIC(*node)) {
                        *no_add_attrs = true;
                        error("variable %qD with %qE attribute must
not be local",
                                *node, name);

and what I think it really wants is that it has a static address - so
a global variable is fine - as opposed to being an actual static
declaration.

Also looking at the plugin, I suspect it is going to be very unhappy
about the fact that the attribute is there both on a declaration and
on the actual definition. The code later seems to really only want to
work on the definition, since it's creating an initializer..

IOW, I get the feeling that the plugin is confused, and it so happened
that the only variables we'd marked for latent entropy were static
ones. But I haven't done gcc plugins, so...

Adding the gcc plugin people. Otherwise the only option seems to be to
just remove that __latent_entropy marker.

                    Linus