"H . J . Lu" wrote:
> On Thu, Jan 17, 2002 at 02:34:37PM +0100, Carsten Langgaard wrote:
> > I posted the following problem on the list almost a year ago, but it
> > still hasn't made into the SGI CVS.
> > I think there is a bug in the _save_fp_context function in
> > arch/mips/kernel/r4k_fpu.S
> > The problem is the following piece of code:
> > jr ra
> > .set nomacro
> > EX(sw t0,SC_FPC_EIR(a0))
> > .set macro
> > We do not handle entries in the __ex_table which is located in a branch
> > delay.
> > So we need to handle the situation where we take a page fault on an
> > instruction which is located in a brach delay slot, or we don't put the
> > "potential" faulting instruction in a delay slot.
> > This situation probably doesn't generally hit people since it hasn't
> > been fix yet, but if you try run something nasty like Crashme, you will
> > get hit by this problem.
> > I suggest the following patch.
> > /Carsten
> > --
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> > Index: arch/mips/kernel/r4k_fpu.S
> > ===================================================================
> > RCS file: /cvs/linux/arch/mips/kernel/r4k_fpu.S,v
> > retrieving revision 1.12
> > diff -u -r1.12 r4k_fpu.S
> > --- arch/mips/kernel/r4k_fpu.S 2001/04/11 05:19:46 1.12
> > +++ arch/mips/kernel/r4k_fpu.S 2002/01/17 14:21:09
> > @@ -50,11 +50,10 @@
> > EX(sdc1 $f30,(SC_FPREGS+240)(a0))
> > EX(sw t1,SC_FPC_CSR(a0))
> > cfc1 t0,$0 # implementation/version
> > + EX(sw t0,SC_FPC_EIR(a0))
> > jr ra
> > - .set nomacro
> > - EX(sw t0,SC_FPC_EIR(a0))
> > - .set macro
> > + nop
> > END(_save_fp_context)
> > /*
> Do we still need this patch for 2.4 on OSS?
No, this fix is not needed any more, as we now handle entries in the
__ex_table which is located in a branch delay.