[PATCH 2/2] powerpc/math-emu: keep track of the instructions unimplemented by FPU

[Kevin Hao]

On Thu, Jul 11, 2013 at 10:45:21PM +1000, Benjamin Herrenschmidt wrote:
> On Thu, 2013-07-11 at 20:21 +0800, Kevin Hao wrote:
> > Some cores (such as Freescale BookE) don't implement all floating
> > point instructions in ISA. But some gcc versions do use these
> > instructions. So we would have to enable the math emulation in this
> > case. Add this to emulated instructions tracking statistics so that
> > the user has a way to know that its toolcahin emit these unimplemented
> > floating point instructions.
> 
> That patch is gross, it makes the function even more nasty than it
> already is. Besides, CONFIG_PPC_FPU doesn't mean you have a HW FPU,
> you need to check the CPU feature bits.
> 
> Also the caller already does PPC_WARN_EMULATED, so this patch makes
> you call it twice or am I missing something ?

There are two invocations of do_mathemu() in the traps.c. The one in the
function program_check_exception() doesn't call the PPC_WARN_EMULATED.
This is also the one I try to fix. Of course my patch will definitely corrupt
the one in function SoftwareEmulation(). I will respin a new patch to
fix this. Sorry for my mistake.

Thanks,
Kevin

> 
> Cheers,
> Ben.
> 
> > Signed-off-by: Kevin Hao <haokexin at gmail.com>
> > ---
> >  arch/powerpc/math-emu/math.c | 50 +++++++++++++++++++++++++++-----------------
> >  1 file changed, 31 insertions(+), 19 deletions(-)
> > 
> > diff --git a/arch/powerpc/math-emu/math.c b/arch/powerpc/math-emu/math.c
> > index 18ce6a7..9a98b6c 100644
> > --- a/arch/powerpc/math-emu/math.c
> > +++ b/arch/powerpc/math-emu/math.c
> > @@ -10,6 +10,7 @@
> >  
> >  #include <asm/sfp-machine.h>
> >  #include <math-emu/double.h>
> > +#include <asm/emulated_ops.h>
> >  
> >  #define FLOATFUNC(x)	extern int x(void *, void *, void *, void *)
> >  
> > @@ -222,10 +223,17 @@ do_mathemu(struct pt_regs *regs)
> >  	int idx = 0;
> >  	int (*func)(void *, void *, void *, void *);
> >  	int type = 0;
> > -	int eflag, trap;
> > +	int eflag, trap, ret = -ENOSYS;
> > +	int has_hw_fpu = 0;
> >  
> > -	if (get_user(insn, (u32 *)pc))
> > -		return -EFAULT;
> > +#ifdef CONFIG_PPC_FPU
> > +	has_hw_fpu = 1;
> > +#endif
> > +
> > +	if (get_user(insn, (u32 *)pc)) {
> > +		ret = -EFAULT;
> > +		goto out;
> > +	}
> >  
> >  	switch (insn >> 26) {
> >  	case LFS:	func = lfs;	type = D;	break;
> > @@ -249,7 +257,7 @@ do_mathemu(struct pt_regs *regs)
> >  		case STFDUX:	func = stfd;	type = XEU;	break;
> >  		case STFIWX:	func = stfiwx;	type = XE;	break;
> >  		default:
> > -			goto illegal;
> > +			goto out;
> >  		}
> >  		break;
> >  
> > @@ -267,7 +275,7 @@ do_mathemu(struct pt_regs *regs)
> >  		case FNMSUBS:	func = fnmsubs;	type = ABC;	break;
> >  		case FNMADDS:	func = fnmadds;	type = ABC;	break;
> >  		default:
> > -			goto illegal;
> > +			goto out;
> >  		}
> >  		break;
> >  
> > @@ -287,7 +295,7 @@ do_mathemu(struct pt_regs *regs)
> >  			case FNMSUB:	func = fnmsub;	type = ABC;	break;
> >  			case FNMADD:	func = fnmadd;	type = ABC;	break;
> >  			default:
> > -				goto illegal;
> > +				goto out;
> >  			}
> >  			break;
> >  		}
> > @@ -309,12 +317,12 @@ do_mathemu(struct pt_regs *regs)
> >  		case MFFS:	func = mffs;	type = X;	break;
> >  		case MTFSF:	func = mtfsf;	type = XFLB;	break;
> >  		default:
> > -			goto illegal;
> > +			goto out;
> >  		}
> >  		break;
> >  
> >  	default:
> > -		goto illegal;
> > +		goto out;
> >  	}
> >  
> >  	switch (type) {
> > @@ -347,7 +355,7 @@ do_mathemu(struct pt_regs *regs)
> >  	case DU:
> >  		idx = (insn >> 16) & 0x1f;
> >  		if (!idx)
> > -			goto illegal;
> > +			goto out;
> >  
> >  		sdisp = (insn & 0xffff);
> >  		op0 = (void *)&current->thread.TS_FPR((insn >> 21) & 0x1f);
> > @@ -375,7 +383,7 @@ do_mathemu(struct pt_regs *regs)
> >  			if (((insn >> 1) & 0x3ff) == STFIWX)
> >  				op1 = (void *)(regs->gpr[(insn >> 11) & 0x1f]);
> >  			else
> > -				goto illegal;
> > +				goto out;
> >  		} else {
> >  			op1 = (void *)(regs->gpr[idx] + regs->gpr[(insn >> 11) & 0x1f]);
> >  		}
> > @@ -417,7 +425,7 @@ do_mathemu(struct pt_regs *regs)
> >  		break;
> >  
> >  	default:
> > -		goto illegal;
> > +		goto out;
> >  	}
> >  
> >  	/*
> > @@ -425,9 +433,8 @@ do_mathemu(struct pt_regs *regs)
> >  	 * if flushed into the thread_struct before attempting
> >  	 * emulation
> >  	 */
> > -#ifdef CONFIG_PPC_FPU
> > -	flush_fp_to_thread(current);
> > -#endif
> > +	if (has_hw_fpu)
> > +		flush_fp_to_thread(current);
> >  
> >  	eflag = func(op0, op1, op2, op3);
> >  
> > @@ -437,8 +444,10 @@ do_mathemu(struct pt_regs *regs)
> >  	}
> >  
> >  	trap = record_exception(regs, eflag);
> > -	if (trap)
> > -		return 1;
> > +	if (trap) {
> > +		ret = 1;
> > +		goto out;
> > +	}
> >  
> >  	switch (type) {
> >  	case DU:
> > @@ -451,8 +460,11 @@ do_mathemu(struct pt_regs *regs)
> >  	}
> >  
> >  	regs->nip += 4;
> > -	return 0;
> > +	ret = 0;
> > +
> > +out:
> > +	if (has_hw_fpu && ret >= 0)
> > +		PPC_WARN_EMULATED(math, regs);
> >  
> > -illegal:
> > -	return -ENOSYS;
> > +	return ret;
> >  }
> 
> 
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