Jakub Kicinski writes:
> On Fri, 12 Apr 2019 22:59:38 +0100, Jiong Wang wrote:
>> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
>> index c722015..3c5ca00 100644
>> --- a/kernel/bpf/verifier.c
>> +++ b/kernel/bpf/verifier.c
>> @@ -1135,7 +1135,7 @@ static int check_subprogs(struct bpf_verifier_env *env)
>> */
>> static int mark_reg_read(struct bpf_verifier_env *env,
>> const struct bpf_reg_state *state,
>> - struct bpf_reg_state *parent)
>> + struct bpf_reg_state *parent, u8 flags)
>> {
>> bool writes = parent == state->parent; /* Observe write marks */
>> int cnt = 0;
>> @@ -1150,17 +1150,17 @@ static int mark_reg_read(struct bpf_verifier_env *env,
>> parent->var_off.value, parent->off);
>> return -EFAULT;
>> }
>> - if (parent->live & REG_LIVE_READ)
>> + if ((parent->live & REG_LIVE_READ) == flags)
>> /* The parentage chain never changes and
>> - * this parent was already marked as LIVE_READ.
>> + * this parent was already marked with all read bits.
>
> No big deal, but I though said you'd modify this patch here...
Ouch, sorry, I created one internal branch before start the test
changes. Looks like the branch is v10 which listed before v2~v9 that
somehow later I switched v9 for the test changing thought it is the latest
branch.
Regards,
Jiong
>
>> * There is no need to keep walking the chain again and
>> - * keep re-marking all parents as LIVE_READ.
>> + * keep re-marking all parents with reads bits in flags.
>> * This case happens when the same register is read
>> * multiple times without writes into it in-between.
>> */
>> break;
>> /* ... then we depend on parent's value */
>> - parent->live |= REG_LIVE_READ;
>> + parent->live |= flags;
>> state = parent;
>> parent = state->parent;
>> writes = true;
>
>> @@ -6227,12 +6317,19 @@ static int propagate_liveness_reg(struct bpf_verifier_env *env,
>> struct bpf_reg_state *reg,
>> struct bpf_reg_state *parent_reg)
>> {
>> + u8 parent_bits = parent_reg->live & REG_LIVE_READ;
>> + u8 bits = reg->live & REG_LIVE_READ;
>> + u8 bits_diff = parent_bits ^ bits;
>> + u8 bits_prop = bits_diff & bits;
>> int err;
>>
>> - if (parent_reg->live & REG_LIVE_READ || !(reg->live & REG_LIVE_READ))
>> + /* "reg" and "parent_reg" has the same read bits, or the bit doesn't
>> + * belong to "reg".
>> + */
>> + if (!bits_diff || !bits_prop)
>> return 0;
>
> .. and here?
