Re: [Qemu-devel] [PATCH] minor x86-64 corrections

[Filip Navara]

Fabrice Bellard wrote:

> Filip Navara wrote:
>
> > Changelog:
> >
> > 2005-01-21 Filip Navara <address@hidden>
> >
> > * Add support for CR8 register.
> > * Don't throw exception when assigning zero to SS register
> > in 64-bit mode.
> >
> > BTW, the callgate support for x86-64 in long mode is broken. See 
> > "AMD64 Architecture Programmer’s Manual Volume 3: General-Purpose and 
> > System Instructions", page 90. Anybody cares to fix it?
>
>
> No time yet. It would be interesting to find the problem for the Linux 
> user code too.

Ok, I'll try to fix it myself. BTW the same issue is present also in the 
protected mode JMP code.

> > +++ target-i386/helper.c    21 Jan 2005 20:13:30 -0000
> > @@ -1454,8 +1454,13 @@
> >      selector &= 0xffff;
> >      if ((selector & 0xfffc) == 0) {
> >          /* null selector case */
> > -        if (seg_reg == R_SS)
> > +        if (seg_reg == R_SS) {
> > +#ifdef TARGET_X86_64
> > +            if (env->hflags & HF_CS64_MASK)
> > +                return;
> > +#endif
> >              raise_exception_err(EXCP0D_GPF, 0);
> > +        }
> >          cpu_x86_load_seg_cache(env, seg_reg, selector, 0, 0, 0);
>
> --- target-i386/helper.c    16 Jan 2005 23:35:43 -0000    1.40
>
> Maybe the SS segment cache should be set to zero ?

I'm not sure really, but I guess you're right.

MOV documentation:
... "It is possible to move a null segment selector value (0000–0003h) 
into the DS, ES, FS,
or GS register. This action does not cause a general protection fault, 
but a subsequent
reference to such a segment does cause a #GP exception. For more 
information about
segment selectors, see “Segment Selectors and Registers” on page 84." ...

GPF is exception is thrown if ... "The SS register was loaded with a 
null segment selector in non-64-bit mode or while CPL = 3." ...

> > +void OPPROTO op_movtl_T0_cr7(void)
> > +{
> > +    T0 = (cpu_get_apic_tpr(env) & 0xf) >> 4;
> > +}
>
> Why do you call it cr7 ? 

Actually that's a typo.

Filip Navara
address@hidden