Subject: Re: [PATCH] ppc: bpf_jit: support MOD operation

From: Benjamin Herrenschmidt <[email-masked]>
Date: Tue, 03 Sep 2013 06:45:50 +1000

On Mon, 2013-09-02 at 19:48 +0200, Vladimir Murzin wrote:
> Ping
> 
> On Wed, Aug 28, 2013 at 02:49:52AM +0400, Vladimir Murzin wrote:
> > commit b6069a9570 (filter: add MOD operation) added generic
> > support for modulus operation in BPF.
> >
Sorry, nobody got a chance to review that yet. Unfortunately Matt
doesn't work for us anymore and none of us has experience with the
BPF code, so somebody (possibly me) will need to spend a bit of time
figuring it out before verifying that is correct.

Do you have a test case/suite by any chance ?

Ben.

> > This patch brings JIT support for PPC64
> > 
> > Signed-off-by: Vladimir Murzin <[email-masked]>
> > ---
> >  arch/powerpc/net/bpf_jit_comp.c | 22 ++++++++++++++++++++++
> >  1 file changed, 22 insertions(+)
> > 
> > diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
> > index bf56e33..96f24dc 100644
> > --- a/arch/powerpc/net/bpf_jit_comp.c
> > +++ b/arch/powerpc/net/bpf_jit_comp.c
> > @@ -193,6 +193,28 @@ static int bpf_jit_build_body(struct sk_filter *fp, u32 *image,
> >  				PPC_MUL(r_A, r_A, r_scratch1);
> >  			}
> >  			break;
> > +		case BPF_S_ALU_MOD_X: /* A %= X; */
> > +			ctx->seen |= SEEN_XREG;
> > +			PPC_CMPWI(r_X, 0);
> > +			if (ctx->pc_ret0 != -1) {
> > +				PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
> > +			} else {
> > +				PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12);
> > +				PPC_LI(r_ret, 0);
> > +				PPC_JMP(exit_addr);
> > +			}
> > +			PPC_DIVWU(r_scratch1, r_A, r_X);
> > +			PPC_MUL(r_scratch1, r_X, r_scratch1);
> > +			PPC_SUB(r_A, r_A, r_scratch1);
> > +			break;
> > +		case BPF_S_ALU_MOD_K: /* A %= K; */
> > +#define r_scratch2 (r_scratch1 + 1)
> > +			PPC_LI32(r_scratch2, K);
> > +			PPC_DIVWU(r_scratch1, r_A, r_scratch2);
> > +			PPC_MUL(r_scratch1, r_scratch2, r_scratch1);
> > +			PPC_SUB(r_A, r_A, r_scratch1);
> > +#undef r_scratch2
> > +			break;
> >  		case BPF_S_ALU_DIV_X: /* A /= X; */
> >  			ctx->seen |= SEEN_XREG;
> >  			PPC_CMPWI(r_X, 0);
> > -- 
> > 1.8.1.5
> >