"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 > > > > > > -- > > _ _ ____ ___ Carsten Langgaard Mailto:carstenl@mips.com > > |\ /|||___)(___ MIPS Denmark Direct: +45 4486 5527 > > | \/ ||| ____) Lautrupvang 4B Switch: +45 4486 5555 > > TECHNOLOGIES 2750 Ballerup Fax...: +45 4486 5556 > > Denmark http://www.mips.com > > > > > > > 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? > > H.J. No, this fix is not needed any more, as we now handle entries in the __ex_table which is located in a branch delay.
