linux-kernel - Re: [PATCH v2] x86/boot: Rename overlapping memcpy() to memmove()

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Message-ID: <20160428093741.GA23251@gmail.com>
Date:	Thu, 28 Apr 2016 11:37:41 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Kees Cook <keescook@...omium.org>
Cc:	Yinghai Lu <yinghai@...nel.org>, Baoquan He <bhe@...hat.com>,
	Borislav Petkov <bp@...e.de>, Ingo Molnar <mingo@...hat.com>,
	"x86@...nel.org" <x86@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrey Ryabinin <aryabinin@...tuozzo.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	"H.J. Lu" <hjl.tools@...il.com>,
	Josh Poimboeuf <jpoimboe@...hat.com>,
	Andy Lutomirski <luto@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] x86/boot: Rename overlapping memcpy() to memmove()


* Kees Cook <keescook@...omium.org> wrote:

> On Thu, Apr 28, 2016 at 2:04 AM, Ingo Molnar <mingo@...nel.org> wrote:
> >
> > * Kees Cook <keescook@...omium.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