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...
> * 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?
