Re: [RFC PATCH bpf-next 10/11] bpf: Introduce PTR_ITER and PTR_ITER_END type flags

[Dave Marchevsky <davemarchevsky@fb.com>]

On 8/1/22 6:44 PM, Alexei Starovoitov wrote:   
> On 7/22/22 11:34 AM, Dave Marchevsky wrote:
>>       if (__is_pointer_value(false, reg)) {
>> +        if (__is_iter_end(reg) && val == 0) {
>> +            __mark_reg_const_zero(reg);
>> +            switch (opcode) {
>> +            case BPF_JEQ:
>> +                return 1;
>> +            case BPF_JNE:
>> +                return 0;
>> +            default:
>> +                return -1;
>> +            }
>> +        }
> 
> as discussed the verifying the loop twice is not safe.
> This needs more advanced verifier hacking.
> Maybe let's postpone rbtree iters for now and resolve all the rest?
> Or do iters with a callback, since that's more or less a clear path fwd?
> 
Yep, I will drop and move to callback-based approach for now. As we discussed
over VC, getting open-coded iteration right will take a long time and hold up
the rest of the patchset.