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From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Tue, 5 Dec 2023 14:14:55 -0800
Message-ID: <CAKwvOdmFJ=ZGN8ZScS5oQpXnAL0wwtTDCeNNGpBKZXzQ4kRAVA@mail.gmail.com>
Subject: Re: [PATCH] lib/string: shrink lib/string.i via IWYU
To:     Greg KH <greg@kroah.com>
Cc:     Al Viro <viro@zeniv.linux.org.uk>, tanzirh@google.com,
        Kees Cook <keescook@chromium.org>,
        Andy Shevchenko <andy@kernel.org>,
        linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org,
        Nick DeSaulniers <nnn@google.com>,
        Andrew Morton <akpm@linux-foundation.org>, llvm@lists.linux.dev
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On Tue, Dec 5, 2023 at 1:59=E2=80=AFPM Greg KH <greg@kroah.com> wrote:
>
> On Tue, Dec 05, 2023 at 01:51:10PM -0800, Nick Desaulniers wrote:
> > On Tue, Dec 5, 2023 at 1:38=E2=80=AFPM Al Viro <viro@zeniv.linux.org.uk=
> wrote:
> > >
> > > It also breeds includes of asm/*.h, by the look of the output, which =
is
> > > not a good thing in general ;-/  E.g. #include <asm/uaccess.h> *anywh=
ere*
> > > outside of linux/uaccess.h is a bad idea.
> >
> > It's not clear to me when it's ok to #include <asm/*.h>.  Is there a
> > convention here that I'm missing?
>
> General rule, NEVER include asm/*.h, there should be a include/*.h
> instead that works.  So much so that checkpatch.pl should catch this,
> right?

ah, shoot, I was showing Tanzir how to use `b4` for patch development,
and forgot to check this.  Indeed it does.

I can see how the check works (scripts/checkpatch.pl L5881).  Decoding
that will probably help us improve the tooling.

>
> But of course, it doesn't always hold true, there are a few minor
> exceptions, but they are rare.

$ grep -r \\#include lib | grep asm

shows quite a few exceptions, and just in lib/.

For example, lib/math/int_log.c includes asm/bug.h.  Is that a case
where lib/math/int_log.c should be #include 'ing linux/bug.h rather
than asm/bug.h?
--=20
Thanks,
~Nick Desaulniers