[PATCH v12 bpf-next 00/10] Add skb + xdp dynptrs

Joanne Koong
2023-02-26T08:51:58Z

This patchset is the 2nd in the dynptr series. The 1st can be found here [0].

This patchset adds skb and xdp type dynptrs, which have two main benefits for
packet parsing:
* allowing operations on sizes that are not statically known at
compile-time (eg variable-sized accesses).
* more ergonomic and less brittle iteration through data (eg does not need
manual if checking for being within bounds of data_end)

When comparing the differences in runtime for packet parsing without dynptrs
vs. with dynptrs, there is no noticeable difference. Patch 9 contains more
details as well as examples of how to use skb and xdp dynptrs.

[0] https://lore.kernel.org/bpf/20220523210712.3641569-1-joannelkoong@gmail.com/

--
Changelog:

v11 = https://lore.kernel.org/bpf/20230222060747.2562549-1-joannelkoong@gmail.com/
v11 -> v12:
* Change constant mem size checking to use "__szk" kfunc annotation
for slices
* Use autoloading for success selftests

v10 = https://lore.kernel.org/bpf/20230216225524.1192789-1-joannelkoong@gmail.com/
v10 -> v11:
* Reject bpf_dynptr_slice_rdwr() for non-writable progs at load time
instead of runtime
* Add additional patch (__uninit kfunc annotation)
* Expand on documentation
* Add bpf_dynptr_write() calls for persisting writes in tests

v9 = https://lore.kernel.org/bpf/20230127191703.3864860-1-joannelkoong@gmail.com/
v9 -> v10:
* Add bpf_dynptr_slice and bpf_dynptr_slice_rdwr interface
* Add some more tests
* Split up patchset into more parts to make it easier to review

v8 = https://lore.kernel.org/bpf/20230126233439.3739120-1-joannelkoong@gmail.com/
v8 -> v9:
* Fix dynptr_get_type() to check non-stack dynptrs

v7 = https://lore.kernel.org/bpf/20221021011510.1890852-1-joannelkoong@gmail.com/
v7 -> v8:
* Change helpers to kfuncs
* Add 2 new patches (1/5 and 2/5)

v6 = https://lore.kernel.org/bpf/20220907183129.745846-1-joannelkoong@gmail.com/
v6 -> v7
* Change bpf_dynptr_data() to return read-only data slices if the skb prog
is read-only (Martin)
* Add test "skb_invalid_write" to test that writes to rd-only data slices
are rejected

v5 = https://lore.kernel.org/bpf/20220831183224.3754305-1-joannelkoong@gmail.com/
v5 -> v6
* Address kernel test robot errors by static inlining

v4 = https://lore.kernel.org/bpf/20220822235649.2218031-1-joannelkoong@gmail.com/
v4 -> v5
* Address kernel test robot errors for configs w/out CONFIG_NET set
* For data slices, return PTR_TO_MEM instead of PTR_TO_PACKET (Kumar)
* Split selftests into subtests (Andrii)
* Remove insn patching. Use rdonly and rdwr protos for dynptr skb
construction (Andrii)
* bpf_dynptr_data() returns NULL for rd-only dynptrs. There will be a
separate bpf_dynptr_data_rdonly() added later (Andrii and Kumar)

v3 = https://lore.kernel.org/bpf/20220822193442.657638-1-joannelkoong@gmail.com/
v3 -> v4
* Forgot to commit --amend the kernel test robot error fixups

v2 = https://lore.kernel.org/bpf/20220811230501.2632393-1-joannelkoong@gmail.com/
v2 -> v3
* Fix kernel test robot build test errors

v1 = https://lore.kernel.org/bpf/20220726184706.954822-1-joannelkoong@gmail.com/
v1 -> v2
* Return data slices to rd-only skb dynptrs (Martin)
* bpf_dynptr_write allows writes to frags for skb dynptrs, but always
invalidates associated data slices (Martin)
* Use switch casing instead of ifs (Andrii)
* Use 0xFD for experimental kind number in the selftest (Zvi)
* Put selftest conversions w/ dynptrs into new files (Alexei)
* Add new selftest "test_cls_redirect_dynptr.c"

Joanne Koong (10):
bpf: Support "sk_buff" and "xdp_buff" as valid kfunc arg types
bpf: Refactor process_dynptr_func
bpf: Allow initializing dynptrs in kfuncs
bpf: Define no-ops for externally called bpf dynptr functions
bpf: Refactor verifier dynptr into get_dynptr_arg_reg
bpf: Add __uninit kfunc annotation
bpf: Add skb dynptrs
bpf: Add xdp dynptrs
bpf: Add bpf_dynptr_slice and bpf_dynptr_slice_rdwr
selftests/bpf: tests for using dynptrs to parse skb and xdp buffers

Documentation/bpf/kfuncs.rst | 17 +
include/linux/bpf.h | 95 +-
include/linux/bpf_verifier.h | 3 -
include/linux/filter.h | 46 +
include/uapi/linux/bpf.h | 18 +-
kernel/bpf/btf.c | 22 +
kernel/bpf/helpers.c | 221 +++-
kernel/bpf/verifier.c | 413 ++++++--
net/core/filter.c | 108 +-
tools/include/uapi/linux/bpf.h | 18 +-
tools/testing/selftests/bpf/bpf_kfuncs.h | 38 +
.../selftests/bpf/prog_tests/cls_redirect.c | 25 +
.../testing/selftests/bpf/prog_tests/dynptr.c | 74 +-
.../selftests/bpf/prog_tests/l4lb_all.c | 2 +
.../bpf/prog_tests/parse_tcp_hdr_opt.c | 93 ++
.../selftests/bpf/prog_tests/xdp_attach.c | 11 +-
.../testing/selftests/bpf/progs/dynptr_fail.c | 287 ++++-
.../selftests/bpf/progs/dynptr_success.c | 55 +-
.../bpf/progs/test_cls_redirect_dynptr.c | 980 ++++++++++++++++++
.../bpf/progs/test_l4lb_noinline_dynptr.c | 487 +++++++++
.../bpf/progs/test_parse_tcp_hdr_opt.c | 119 +++
.../bpf/progs/test_parse_tcp_hdr_opt_dynptr.c | 114 ++
.../selftests/bpf/progs/test_xdp_dynptr.c | 257 +++++
.../selftests/bpf/test_tcp_hdr_options.h | 1 +
24 files changed, 3318 insertions(+), 186 deletions(-)
create mode 100644 tools/testing/selftests/bpf/bpf_kfuncs.h
create mode 100644 tools/testing/selftests/bpf/prog_tests/parse_tcp_hdr_opt.c
create mode 100644 tools/testing/selftests/bpf/progs/test_cls_redirect_dynptr.c
create mode 100644 tools/testing/selftests/bpf/progs/test_l4lb_noinline_dynptr.c
create mode 100644 tools/testing/selftests/bpf/progs/test_parse_tcp_hdr_opt.c
create mode 100644 tools/testing/selftests/bpf/progs/test_parse_tcp_hdr_opt_dynptr.c
create mode 100644 tools/testing/selftests/bpf/progs/test_xdp_dynptr.c

--
2.34.1