From: Yonghong Song <yhs@fb.com>
To: <bpf@vger.kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>,
Cong Wang <xiyou.wangcong@gmail.com>,
Daniel Borkmann <daniel@iogearbox.net>, <kernel-team@fb.com>
Subject: [PATCH bpf-next v5 00/12] bpf: add bpf_for_each_map_elem() helper
Date: Fri, 26 Feb 2021 12:49:20 -0800 [thread overview]
Message-ID: <20210226204920.3884074-1-yhs@fb.com> (raw)
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@gmail.com/
Changelogs:
v4 -> v5:
- rebase on top of bpf-next.
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 | 38 ++
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 | 38 ++
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(+), 64 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
next reply other threads:[~2021-02-26 20:50 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-26 20:49 Yonghong Song [this message]
2021-02-26 20:49 ` [PATCH bpf-next v5 01/12] bpf: factor out visit_func_call_insn() in check_cfg() Yonghong Song
2021-02-26 20:49 ` [PATCH bpf-next v5 02/12] bpf: factor out verbose_invalid_scalar() Yonghong Song
2021-02-26 20:49 ` [PATCH bpf-next v5 03/12] bpf: refactor check_func_call() to allow callback function Yonghong Song
2021-02-26 20:49 ` [PATCH bpf-next v5 04/12] bpf: change return value of verifier function add_subprog() Yonghong Song
2021-02-26 20:49 ` [PATCH bpf-next v5 05/12] bpf: add bpf_for_each_map_elem() helper Yonghong Song
2021-02-26 21:29 ` Alexei Starovoitov
2021-02-26 20:49 ` [PATCH bpf-next v5 06/12] bpf: add hashtab support for " Yonghong Song
2021-02-26 20:49 ` [PATCH bpf-next v5 07/12] bpf: add arraymap " Yonghong Song
2021-02-26 20:49 ` [PATCH bpf-next v5 08/12] libbpf: move function is_ldimm64() earlier in libbpf.c Yonghong Song
2021-02-26 20:49 ` [PATCH bpf-next v5 09/12] libbpf: support subprog address relocation Yonghong Song
2021-02-26 20:49 ` [PATCH bpf-next v5 10/12] bpftool: print subprog address properly Yonghong Song
2021-02-26 20:49 ` [PATCH bpf-next v5 11/12] selftests/bpf: add hashmap test for bpf_for_each_map_elem() helper Yonghong Song
2021-02-26 20:49 ` [PATCH bpf-next v5 12/12] selftests/bpf: add arraymap " Yonghong Song
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