On 13/12/18 03:41, Jakub Kicinski wrote:
> Some JITs (nfp) try to optimize code on their own. It could make
> sense in case of BPF_JSET instruction which is currently not interpreted
> by the verifier, meaning for instance that dead could would not be
> detected if it was under BPF_JSET branch.
>
> Teach the verifier basics of BPF_JSET, JIT optimizations will be
> removed shortly.
>
> Signed-off-by: Jakub Kicinski <jakub.kicin...@netronome.com>
> Reviewed-by: Jiong Wang <jiong.w...@netronome.com>
> ---
Acked-by: Edward Cree <ec...@solarflare.com>
> kernel/bpf/verifier.c | 20 ++++++++++++++++++++
> 1 file changed, 20 insertions(+)
>
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 8b511a4fe84a..50bb45aa4f26 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -3788,6 +3788,12 @@ static int is_branch_taken(struct bpf_reg_state *reg,
> u64 val, u8 opcode)
> if (tnum_is_const(reg->var_off))
> return !tnum_equals_const(reg->var_off, val);
> break;
> + case BPF_JSET:
> + if ((~reg->var_off.mask & reg->var_off.value) & val)
> + return 1;
> + if (!((reg->var_off.mask | reg->var_off.value) & val))
> + return 0;
> + break;
> case BPF_JGT:
> if (reg->umin_value > val)
> return 1;
> @@ -3872,6 +3878,13 @@ static void reg_set_min_max(struct bpf_reg_state
> *true_reg,
> */
> __mark_reg_known(false_reg, val);
> break;
> + case BPF_JSET:
> + false_reg->var_off = tnum_and(false_reg->var_off,
> + tnum_const(~val));
> + if (is_power_of_2(val))
> + true_reg->var_off = tnum_or(true_reg->var_off,
> + tnum_const(val));
> + break;
> case BPF_JGT:
> false_reg->umax_value = min(false_reg->umax_value, val);
> true_reg->umin_value = max(true_reg->umin_value, val + 1);
> @@ -3944,6 +3957,13 @@ static void reg_set_min_max_inv(struct bpf_reg_state
> *true_reg,
> */
> __mark_reg_known(false_reg, val);
> break;
> + case BPF_JSET:
> + false_reg->var_off = tnum_and(false_reg->var_off,
> + tnum_const(~val));
> + if (is_power_of_2(val))
> + true_reg->var_off = tnum_or(true_reg->var_off,
> + tnum_const(val));
> + break;
> case BPF_JGT:
> true_reg->umax_value = min(true_reg->umax_value, val - 1);
> false_reg->umin_value = max(false_reg->umin_value, val);
