Re: [CRYPTO]: Miscompiling sha256.c by gcc 3.2.3 and arch pentium3,4

[Bill Davidsen]

Jakub Jelinek wrote:
> On Fri, Jan 30, 2004 at 11:14:07AM -0600, Andy Isaacson wrote:
>
> > On Fri, Jan 30, 2004 at 11:35:20AM -0500, James Morris wrote:
> >
> > > -	const u8 padding[64] = { 0x80, };
> > > +	static u8 padding[64] = { 0x80, };
> >
> > The RedHat bug suggests 'static const' as the appropriate replacement.
> >
> > https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=114610#c4
> >
> > Unfortunately that probably means an extra 64 bytes of text, rather than
> > the 10 or so bytes of instructions to do the memset and store.  Ideally
> > padding[] would be allocated in BSS rather than text or the stack (and
> > initialized with { 0x80, } at runtime), but I guess you can't have
> > everything.
>
>
> Or you can use
> 	u8 padding[64] = { 0x80 };
> if you really want to initialize it at runtime and want to work around the
> compiler bug.  It shouldn't be any less efficient than
> 	const u8 padding[64] = { 0x80 };
> since it is used just once, passed to non-inlined function.

I like this, as it avoids bloating the 64 bytes into the kernel.


--
bill davidsen <davidsen@xxxxxxx>
  CTO TMR Associates, Inc
  Doing interesting things with small computers since 1979
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