This patch set introduced bpf_for_each_map_elem() helper. The helper permits bpf program iterates through all elements for a particular map. The work originally inspired by an internal discussion where firewall rules are kept in a map and bpf prog wants to check packet 5 tuples against all rules in the map. A bounded loop can be used but it has a few drawbacks. As the loop iteration goes up, verification time goes up too. For really large maps, verification may fail. A helper which abstracts out the loop itself will not have verification time issue. A recent discussion in [1] involves to iterate all hash map elements in bpf program. Currently iterating all hashmap elements in bpf program is not easy if key space is really big. Having a helper to abstract out the loop itself is even more meaningful. The proposed helper signature looks like: long bpf_for_each_map_elem(map, callback_fn, callback_ctx, flags) where callback_fn is a static function and callback_ctx is a piece of data allocated on the caller stack which can be accessed by the callback_fn. The callback_fn signature might be different for different maps. For example, for hash/array maps, the signature might be long callback_fn(map, key, val, callback_ctx) In the rest of series, Patch 1 did some refactoring. Patch 2 implemented core kernel support for the helper. Patches 3 and 4 added hashmap and arraymap support. Patches 5 and 6 added libbpf and bpftool support. Patches 7 and 8 added selftests for hashmap and arraymap. [1]: https://lore.kernel.org/bpf/20210122205415.113822-1-xiyou.wangcong@xxxxxxxxx/ Yonghong Song (8): bpf: refactor BPF_PSEUDO_CALL checking as a helper function bpf: add bpf_for_each_map_elem() helper bpf: add hashtab support for bpf_for_each_map_elem() helper bpf: add arraymap support for bpf_for_each_map_elem() helper libbpf: support local function pointer relocation bpftool: print local function pointer properly selftests/bpf: add hashmap test for bpf_for_each_map_elem() helper selftests/bpf: add arraymap test for bpf_for_each_map_elem() helper include/linux/bpf.h | 18 ++ include/linux/bpf_verifier.h | 3 + include/uapi/linux/bpf.h | 28 ++ kernel/bpf/arraymap.c | 36 +++ kernel/bpf/bpf_iter.c | 16 + kernel/bpf/hashtab.c | 57 ++++ kernel/bpf/helpers.c | 2 + kernel/bpf/verifier.c | 299 ++++++++++++++++-- kernel/trace/bpf_trace.c | 2 + tools/bpf/bpftool/xlated_dumper.c | 3 + tools/include/uapi/linux/bpf.h | 28 ++ tools/lib/bpf/libbpf.c | 33 +- .../selftests/bpf/prog_tests/for_each.c | 145 +++++++++ .../bpf/progs/for_each_array_map_elem.c | 71 +++++ .../bpf/progs/for_each_hash_map_elem.c | 103 ++++++ 15 files changed, 811 insertions(+), 33 deletions(-) create mode 100644 tools/testing/selftests/bpf/prog_tests/for_each.c create mode 100644 tools/testing/selftests/bpf/progs/for_each_array_map_elem.c create mode 100644 tools/testing/selftests/bpf/progs/for_each_hash_map_elem.c -- 2.24.1
