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From: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Date: Sat, 2 Oct 2021 19:32:15 +0200
Message-ID: <CAM1=_QTaf0fhK4js=2=dZ2MXh6zHoUDzwn3Y-mXY5Fxo=rygpA@mail.gmail.com>
Subject: Re: [PATCH 5/9] powerpc/bpf: Fix BPF_MOD when imm == 1
To: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
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On Fri, Oct 1, 2021 at 11:15 PM Naveen N. Rao
<naveen.n.rao@linux.vnet.ibm.com> wrote:
>
> Only ignore the operation if dividing by 1.
>
> Fixes: 156d0e290e969c ("powerpc/ebpf/jit: Implement JIT compiler for extended BPF")
> Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>

Acked-by: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Tested-by: Johan Almbladh <johan.almbladh@anyfinetworks.com>

> ---
>  arch/powerpc/net/bpf_jit_comp64.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
> index 3351a866ef6207..ffb7a2877a8469 100644
> --- a/arch/powerpc/net/bpf_jit_comp64.c
> +++ b/arch/powerpc/net/bpf_jit_comp64.c
> @@ -391,8 +391,14 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
>                 case BPF_ALU64 | BPF_DIV | BPF_K: /* dst /= imm */
>                         if (imm == 0)
>                                 return -EINVAL;
> -                       else if (imm == 1)
> -                               goto bpf_alu32_trunc;
> +                       if (imm == 1) {
> +                               if (BPF_OP(code) == BPF_DIV) {
> +                                       goto bpf_alu32_trunc;
> +                               } else {
> +                                       EMIT(PPC_RAW_LI(dst_reg, 0));
> +                                       break;
> +                               }
> +                       }
>
>                         PPC_LI32(b2p[TMP_REG_1], imm);
>                         switch (BPF_CLASS(code)) {
> --
> 2.33.0
>