diff options
Diffstat (limited to 'kernel/bpf/cnum.c')
| -rw-r--r-- | kernel/bpf/cnum.c | 36 |
1 files changed, 36 insertions, 0 deletions
diff --git a/kernel/bpf/cnum.c b/kernel/bpf/cnum.c index 86142cb2aee5..8ec5187d7c75 100644 --- a/kernel/bpf/cnum.c +++ b/kernel/bpf/cnum.c @@ -2,6 +2,7 @@ /* Copyright (c) 2026 Meta Platforms, Inc. and affiliates. */ #include <linux/bits.h> +#include <linux/bpf_verifier.h> /* for imod() */ #define T 32 #include "cnum_defs.h" @@ -118,3 +119,38 @@ struct cnum64 cnum64_cnum32_intersect(struct cnum64 a, struct cnum32 b) } return t; } + +/* Intersect 'in' with the set of integers defined by equation 'base + step * k'. */ +struct cnum64 cnum64_intersect_linear(struct cnum64 in, u16 base, u16 step) +{ + s64 smin = cnum64_smin(in); + s64 smax = cnum64_smax(in); + s64 lo, hi; + u16 d; + + if (step <= 1 || cnum64_is_empty(in) || cnum64_srange_overflow(in)) + return in; + /* + * Round smin up to the next value congruent to 'base' modulo 'step', + * i.e. increase smin by d = (base - smin) mod step: + * + * |<---- d ---->| + * |-----------|=============|... + * base+step*k smin base+step*(k+1) + */ + d = imod(base - imod(smin, step), step); + if ((u64)smax - (u64)smin < d) + return CNUM64_EMPTY; + lo = smin + d; + /* + * Round smax down to the previous value congruent to 'base' modulo 'step', + * i.e. decrease smax by d = (smax - base) mod step: + * + * |<--- d --->| + * ...|===========|-------------| + * base+step*k smax base+step*(k+1) + */ + d = imod(imod(smax, step) - base, step); + hi = smax - d; + return cnum64_from_srange(lo, hi); +} |