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Date: Thu, 28 Apr 2016 11:37:41 +0200
From: Ingo Molnar <mingo@kernel.org>
To: Kees Cook <keescook@chromium.org>
Cc: Yinghai Lu <yinghai@kernel.org>, Baoquan He <bhe@redhat.com>,
        Borislav Petkov <bp@suse.de>, Ingo Molnar <mingo@redhat.com>,
        "x86@kernel.org" <x86@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
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        Dmitry Vyukov <dvyukov@google.com>, "H.J. Lu" <hjl.tools@gmail.com>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Andy Lutomirski <luto@kernel.org>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] x86/boot: Rename overlapping memcpy() to memmove()
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* Kees Cook <keescook@chromium.org> wrote:

> On Thu, Apr 28, 2016 at 2:04 AM, Ingo Molnar <mingo@kernel.org> wrote:
> >
> > * Kees Cook <keescook@chromium.org> wrote:
> > > +#define memmove              memmove
> >
> > Btw., what's the purpose of this define? If it's already defined then we should
> > get a build warning. If it's not, we won't.
> 
> It's for the decompressor that checks for memmove existing already via
> "ifdef memmove". If this isn't done here, we will end up with two
> memmove implementations.

So:

 triton:~/tip> git grep memmove | grep -i ifdef
 triton:~/tip> 

what am I missing?

> >> +void *memcpy(void *dest, const void *src, size_t n)
> >
> > btw., if there's any doubt about other overlapping uses, we could add this to
> > memcpy():
> >
> >   WARN_ON_ONCE(dest > src && dest-src < n);
> >
> > or so? Does printk() work so early on?
> 
> It does not, but we could use either "error" or the new "warn". Should
> we abort a boot in this case, or just warn about it? (Our
> implementations of memcpy, fwiw, currently seem to support overlap, so
> I would suggest warn.)

Yeah, I'd definitely not try to crash the bootup for the user, but try to 
continue.

Thanks,

	Ingo