bpf/verifier: track signed and unsigned min/max values

Allows us to, sometimes, combine information from a signed check of one
 bound and an unsigned check of the other.
We now track the full range of possible values, rather than restricting
 ourselves to [0, 1<<30) and considering anything beyond that as
 unknown.  While this is probably not necessary, it makes the code more
 straightforward and symmetrical between signed and unsigned bounds.

Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/tnum.h

@@ -17,6 +17,8 @@ struct tnum {
 struct tnum tnum_const(u64 value);
 /* A completely unknown value */
 extern const struct tnum tnum_unknown;
+/* A value that's unknown except that @min <= value <= @max */
+struct tnum tnum_range(u64 min, u64 max);
 
 /* Arithmetic and logical ops */
 /* Shift a tnum left (by a fixed shift) */