Re: [Bug #12608] 2.6.29-rc powerpc G5 Xorg legacy_mem regression

Jesse Barnes
2009-02-07T23:15:20Z

On Friday, February 6, 2009 7:05 pm Benjamin Herrenschmidt wrote:
> On Fri, 2009-02-06 at 14:45 -0800, Jesse Barnes wrote:
> > + if (Base <= 1024*1024) {
> > + /* Try legacy_mem (may not be available or implemented) */
> > + if ((fd = linuxOpenLegacy(dev, "legacy_mem")) < 0) {
> > + addr = mmap(NULL, Size, PROT_READ|PROT_WRITE, MAP_SHARED,
> > fd, Base); + close(fd);
> > + if (addr && addr != MAP_FAILED)
> > + return addr;
> > + }
> > }
> > - return addr;
> > +
> > + /* Fall back to old method if legacy_mem fails or Base >= 1M */
> > + return linuxMapPci(ScreenNum, Flags, dev, Base, Size,
> > PCIIOC_MMAP_IS_MEM); }
>
> I don't like the fallback if legacy_mem exists and returns an error,
> that's an indication that legacy memory is -not- available and thus
> whatever 'fallback' X will try (supposedly using /dev/mem) will be
> horribly broken and will probably end up scribbling all over system
> memory :-)

Yeah, but unless we fix all the callers (and possibly their callers), not
falling back will keep X from starting...

--
Jesse Barnes, Intel Open Source Technology Center