bpf: enable BPF_J{LT, LE, SLT, SLE} opcodes in verifier

Enable the newly added jump opcodes, main parts are in two
different areas, namely direct packet access and dynamic map
value access. For the direct packet access, we now allow for
the following two new patterns to match in order to trigger
markings with find_good_pkt_pointers():

Variant 1 (access ok when taking the branch):

  0: (61) r2 = *(u32 *)(r1 +76)
  1: (61) r3 = *(u32 *)(r1 +80)
  2: (bf) r0 = r2
  3: (07) r0 += 8
  4: (ad) if r0 < r3 goto pc+2
  R0=pkt(id=0,off=8,r=0) R1=ctx R2=pkt(id=0,off=0,r=0)
  R3=pkt_end R10=fp
  5: (b7) r0 = 0
  6: (95) exit

  from 4 to 7: R0=pkt(id=0,off=8,r=8) R1=ctx
               R2=pkt(id=0,off=0,r=8) R3=pkt_end R10=fp
  7: (71) r0 = *(u8 *)(r2 +0)
  8: (05) goto pc-4
  5: (b7) r0 = 0
  6: (95) exit
  processed 11 insns, stack depth 0

Variant 2 (access ok on fall-through):

  0: (61) r2 = *(u32 *)(r1 +76)
  1: (61) r3 = *(u32 *)(r1 +80)
  2: (bf) r0 = r2
  3: (07) r0 += 8
  4: (bd) if r3 <= r0 goto pc+1
  R0=pkt(id=0,off=8,r=8) R1=ctx R2=pkt(id=0,off=0,r=8)
  R3=pkt_end R10=fp
  5: (71) r0 = *(u8 *)(r2 +0)
  6: (b7) r0 = 1
  7: (95) exit

  from 4 to 6: R0=pkt(id=0,off=8,r=0) R1=ctx
               R2=pkt(id=0,off=0,r=0) R3=pkt_end R10=fp
  6: (b7) r0 = 1
  7: (95) exit
  processed 10 insns, stack depth 0

The above two basically just swap the branches where we need
to handle an exception and allow packet access compared to the
two already existing variants for find_good_pkt_pointers().

For the dynamic map value access, we add the new instructions
to reg_set_min_max() and reg_set_min_max_inv() in order to
learn bounds. Verifier test cases for both are added in a
follow-up patch.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>