On Tue, 2024-07-16 at 15:38 -0700, Yonghong Song wrote:
[...]
> diff --git a/tools/testing/selftests/bpf/prog_tests/reg_bounds.c b/tools/testing/selftests/bpf/prog_tests/reg_bounds.c
> index eb74363f9f70..c88602908cfe 100644
> --- a/tools/testing/selftests/bpf/prog_tests/reg_bounds.c
> +++ b/tools/testing/selftests/bpf/prog_tests/reg_bounds.c
> @@ -441,6 +441,22 @@ static struct range range_refine(enum num_t x_t, struct range x, enum num_t y_t,
> if (t_is_32(y_t) && !t_is_32(x_t)) {
> struct range x_swap;
>
> + /* If we know that
> + * - *x* is in the range of signed 32bit value
> + * - *y_cast* range is 32-bit sign non-negative, and
> + * then *x* range can be narrowed to the interaction of
> + * *x* and *y_cast*. Otherwise, if the new range for *x*
> + * allows upper 32-bit 0xffffffff then the eventual new
> + * range for *x* will be out of signed 32-bit range
> + * which violates the origin *x* range.
> + */
> + if (x_t == S64 && y_t == S32 &&
> + !(y_cast.a & 0xffffffff80000000ULL) && !(y_cast.b & 0xffffffff80000000) &&
> + (long long)x.a >= S32_MIN && (long long)x.b <= S32_MAX) {
> + return range(S64, max_t(S64, y_cast.a, x.a),
> + min_t(S64, y_cast.b, x.b));
> + }
> +
> /* some combinations of upper 32 bits and sign bit can lead to
> * invalid ranges, in such cases it's easier to detect them
> * after cast/swap than try to enumerate all the conditions
> @@ -2108,6 +2124,9 @@ static struct subtest_case crafted_cases[] = {
> {S32, U32, {(u32)S32_MIN, 0}, {0, 0}},
> {S32, U32, {(u32)S32_MIN, 0}, {(u32)S32_MIN, (u32)S32_MIN}},
> {S32, U32, {(u32)S32_MIN, S32_MAX}, {S32_MAX, S32_MAX}},
> + {S64, U32, {0x0, 0x1f}, {0xffffffff80000000ULL, 0x000000007fffffffULL}},
> + {S64, U32, {0x0, 0x1f}, {0xffffffffffff8000ULL, 0x0000000000007fffULL}},
> + {S64, U32, {0x0, 0x1f}, {0xffffffffffffff80ULL, 0x000000000000007fULL}},
> };
>
> /* Go over crafted hard-coded cases. This is fast, so we do it as part of
>
> The logic is very similar to kernel implementation but has a difference in generating
> the final range. In reg_bounds implementation, the range is narrowed by intersecting
> y_cast and x range which are necessary.
>
> In kernel implementation, there is no interection since we only have one register
> and two register has been compared before.
>
> Eduard, could you take a look at the above code?
I think this change is correct.
The return clause could be simplified a bit:
return range_improve(x_t, x, y_cast);
[...]
