Re: [patches] e500 prctl usage

[Daniel Jacobowitz <dan@xxxxxxxxxxxxxxxx>]

On Fri, Aug 31, 2007 at 11:56:47AM -0400, Daniel Jacobowitz wrote:
> Secondly, while looking at this, I had to wonder: what's the point of
> using prctl for this?  Glibc directly writes the SPEFSCR to set the
> rounding mode, so it obviously can do so.  I would expect the FINXE,
> FINVE, FDBZE, FUNFE, and FOVFE bits to be writable too and to be both
> necessary and sufficient.  Right now nothing is setting them so I
> don't know why we would end up with a trap.
> 
> I couldn't find a big-picture comment anywhere explaining that,
> but there's probably a reason I'm not familiar with.

Here's a guess at the answer: do we need the exceptions enabled all
the time in order to reach the kernel IEEE754 emulation, and then the
kernel has to sort out whether to turn that into a SIGFPE?

-- 
Daniel Jacobowitz
CodeSourcery