On Sat, Mar 30, 2024 at 8:44 PM Yafang Shao <laoar.shao@xxxxxxxxx> wrote:
>
> Three new kfuncs, namely bpf_iter_bits_{new,next,destroy}, have been
> added for the new bpf_iter_bits functionality. These kfuncs enable the
> iteration of the bits from a given address and a given number of bits.
>
> - bpf_iter_bits_new
> Initialize a new bits iterator for a given memory area. Due to the
> limitation of bpf memalloc, the max number of bits to be iterated
> over is (4096 * 8).
> - bpf_iter_bits_next
> Get the next bit in a bpf_iter_bits
> - bpf_iter_bits_destroy
> Destroy a bpf_iter_bits
>
> The bits iterator can be used in any context and on any address.
>
> Changes:
> - v4->v5:
> - Simplify test cases (Andrii)
hm... I think you oversimplified them :) Your negative tests are good,
but there is now no "positive" test that shows that iterator functions
properly. I'd suggest to add few positive tests (still within
RUN_TESTS framework) using __retval (grep for other use cases using
it) to check actual values.
I think you need to validate that iterator works for:
a) bit mask smaller than 8 bytes (and also maybe number of bits that
are not multiple of 8, e.g., have 20 bit bitmask, but set entire
32-bit value to 1s, check that you get only 20 iterator next()
returns)
b) a typical case of having 8-byte bit mask (you can have some
irregular pattern of bits, like 0b1111000111001101, and calculate a
sum of bit positions, returned for __retval check. This will catch
endianness issues, if there are still any.
c) another typical case where bit mask is > 8 bytes (same idea with
position sum would work, but probably just counting number of bits
would be enough)
pw-bot: cr
> - v3->v4:
> - Fix endianness error on s390x (Andrii)
> - zero-initialize kit->bits_copy and zero out nr_bits (Andrii)
> - v2->v3:
> - Optimization for u64/u32 mask (Andrii)
> - v1->v2:
> - Simplify the CPU number verification code to avoid the failure on s390x
> (Eduard)
> - bpf: Add bpf_iter_cpumask
> https://lwn.net/Articles/961104/
> - bpf: Add new bpf helper bpf_for_each_cpu
> https://lwn.net/Articles/939939/
>
> Yafang Shao (2):
> bpf: Add bits iterator
> selftests/bpf: Add selftest for bits iter
>
> kernel/bpf/helpers.c | 120 ++++++++++++++++++
> .../selftests/bpf/prog_tests/verifier.c | 2 +
> .../selftests/bpf/progs/verifier_bits_iter.c | 57 +++++++++
> 3 files changed, 179 insertions(+)
> create mode 100644 tools/testing/selftests/bpf/progs/verifier_bits_iter.c
>
> --
> 2.39.1
>
