On Thu, May 24, 2001 at 03:42:56PM +0200, Maciej W. Rozycki wrote:
> On Wed, 23 May 2001, Daniel Jacobowitz wrote:
> > The ll/sc constructs in the kernel use ".set noat" to inhibit use of $at,
> > and proceed to use it themselves. This is fine, except for one problem: the
> > constraints on memory operands are "o" and "=o", which means offsettable
> > memory references. If I'm not mistaken, the assembler will (always?)
> > turn these into uses of $at if the offset is not 0 - at least, it certainly
> > seems to do that here (gcc 2.95.3, binutils 126.96.36.199.2). Just being honest
> > with the compiler and asking for a real memory reference does the trick.
> Both "m" and "o" seem to be incorrect here as both are the same for MIPS;
> "R" seems to be appropriate, OTOH. Still gcc 2.95.3 doesn't handle "R"
> fine for all cases, but it works most of the time and emits a warning
> otherwise. I can't comment on 3.0.
They aren't the same for MIPS, though. I exhibit as evidence the fact
that my patch fixed the problem I was seeing. I didn't know about 'R';
I suppose that it is more correct. 'm' at least is closer than 'o',
If 'R' will behave correctly, could that be applied to CVS, then?
> Note that if noat is in effect and at is to be used, gas should bail out
> with an error. There is a bug, if it doesn't.
It issues a warning, currently (188.8.131.52.2 - I think 2.11 behaves the
Daniel Jacobowitz Debian GNU/Linux Developer
Monta Vista Software Debian Security Team