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 1/2/3/4 did some refactoring. Patch 5 implemented core kernel support for the helper. Patches 6 and 7 added hashmap and arraymap support. Patches 8/9 added libbpf support. Patch 10 added bpftool support. Patches 11 and 12 added selftests for hashmap and arraymap. [1]: https://lore.kernel.org/bpf/20210122205415.113822-1-xiyou.wangcong@xxxxxxxxx/ Changelogs: v3 -> v4: - better refactoring of check_func_call(), calculate subprogno outside of __check_func_call() helper. (Andrii) - better documentation (like the list of supported maps and their callback signatures) in uapi header. (Andrii) - implement and use ASSERT_LT in selftests. (Andrii) - a few other minor changes. v2 -> v3: - add comments in retrieve_ptr_limit(), which is in sanitize_ptr_alu(), to clarify the code is not executed for PTR_TO_MAP_KEY handling, but code is manually tested. (Alexei) - require BTF for callback function. (Alexei) - simplify hashmap/arraymap callback return handling as return value [0, 1] has been enforced by the verifier. (Alexei) - also mark global subprog (if used in ld_imm64) as RELO_SUBPROG_ADDR. (Andrii) - handle the condition to mark RELO_SUBPROG_ADDR properly. (Andrii) - make bpftool subprog insn offset dumping consist with pcrel calls. (Andrii) v1 -> v2: - setup callee frame in check_helper_call() and then proceed to verify helper return value as normal (Alexei) - use meta data to keep track of map/func pointer to avoid hard coding the register number (Alexei) - verify callback_fn return value range [0, 1]. (Alexei) - add migrate_{disable, enable} to ensure percpu value is the one bpf program expects to see. (Alexei) - change bpf_for_each_map_elem() return value to the number of iterated elements. (Andrii) - Change libbpf pseudo_func relo name to RELO_SUBPROG_ADDR and use more rigid checking for the relocation. (Andrii) - Better format to print out subprog address with bpftool. (Andrii) - Use bpf_prog_test_run to trigger bpf run, instead of bpf_iter. (Andrii) - Other misc changes. Yonghong Song (12): 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: change return value of verifier function add_subprog() 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 subprog address relocation bpftool: print subprog address 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 | 39 +- kernel/bpf/arraymap.c | 40 ++ kernel/bpf/bpf_iter.c | 16 + kernel/bpf/hashtab.c | 65 ++++ kernel/bpf/helpers.c | 2 + kernel/bpf/verifier.c | 364 +++++++++++++++--- kernel/trace/bpf_trace.c | 2 + tools/bpf/bpftool/xlated_dumper.c | 3 + tools/include/uapi/linux/bpf.h | 39 +- tools/lib/bpf/libbpf.c | 76 +++- .../selftests/bpf/prog_tests/for_each.c | 130 +++++++ .../bpf/progs/for_each_array_map_elem.c | 61 +++ .../bpf/progs/for_each_hash_map_elem.c | 95 +++++ tools/testing/selftests/bpf/test_progs.h | 11 + 16 files changed, 897 insertions(+), 66 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
