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 is long callback_fn(map, key, val, callback_ctx) In the rest of series, Patches 1/2/3 did some refactoring. Patch 4 implemented core kernel support for the helper. Patches 5 and 6 added hashmap and arraymap support. Patches 7/8 added libbpf support. Patch 9 added bpftool support. Patches 10 and 11 added selftests for hashmap and arraymap. [1]: https://lore.kernel.org/bpf/20210122205415.113822-1-xiyou.wangcong@xxxxxxxxx/ Yonghong Song (11): bpf: factor out visit_func_call_insn() in check_cfg() bpf: factor out verbose_invalid_scalar() bpf: refactor check_func_call() to allow callback 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: move function is_ldimm64() earlier in libbpf.c 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 | 17 + include/linux/bpf_verifier.h | 3 + include/uapi/linux/bpf.h | 29 +- kernel/bpf/arraymap.c | 39 ++ kernel/bpf/bpf_iter.c | 16 + kernel/bpf/hashtab.c | 63 ++++ kernel/bpf/helpers.c | 2 + kernel/bpf/verifier.c | 346 +++++++++++++++--- kernel/trace/bpf_trace.c | 2 + tools/bpf/bpftool/xlated_dumper.c | 3 + tools/include/uapi/linux/bpf.h | 29 +- tools/lib/bpf/libbpf.c | 52 ++- .../selftests/bpf/prog_tests/for_each.c | 132 +++++++ .../bpf/progs/for_each_array_map_elem.c | 61 +++ .../bpf/progs/for_each_hash_map_elem.c | 95 +++++ 15 files changed, 829 insertions(+), 60 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
