On Fri, Apr 1, 2022 at 6:59 PM Joanne Koong <joannekoong@xxxxxx> wrote: > > From: Joanne Koong <joannelkoong@xxxxxxxxx> > > This patchset implements the basics of dynamic pointers in bpf. > > A dynamic pointer (struct bpf_dynptr) is a pointer that stores extra metadata > alongside the address it points to. This abstraction is useful in bpf, given > that every memory access in a bpf program must be safe. The verifier and bpf > helper functions can use the metadata to enforce safety guarantees for things > such as dynamically sized strings and kernel heap allocations. > > From the program side, the bpf_dynptr is an opaque struct and the verifier > will enforce that its contents are never written to by the program. > It can only be written to through specific bpf helper functions. > > There are several uses cases for dynamic pointers in bpf programs. A list of > some are: dynamically sized ringbuf reservations without any extra memcpys, > dynamic string parsing and memory comparisons, dynamic memory allocations that > can be persisted in a map, and dynamic parsing of sk_buff and xdp_md packet > data. > > At a high-level, the patches are as follows: > 1/7 - Adds MEM_UNINIT as a bpf_type_flag > 2/7 - Adds MEM_RELEASE as a bpf_type_flag > 3/7 - Adds bpf_dynptr_from_mem, bpf_malloc, and bpf_free > 4/7 - Adds bpf_dynptr_read and bpf_dynptr_write > 5/7 - Adds dynptr data slices (ptr to underlying dynptr memory) > 6/7 - Adds dynptr support for ring buffers > 7/7 - Tests to check that verifier rejects certain fail cases and passes > certain success cases > > This is the first dynptr patchset in a larger series. The next series of > patches will add persisting dynamic memory allocations in maps, parsing packet > data through dynptrs, dynptrs to referenced objects, convenience helpers for > using dynptrs as iterators, and more helper functions for interacting with > strings and memory dynamically. > > Joanne Koong (7): > bpf: Add MEM_UNINIT as a bpf_type_flag > bpf: Add MEM_RELEASE as a bpf_type_flag > bpf: Add bpf_dynptr_from_mem, bpf_malloc, bpf_free > bpf: Add bpf_dynptr_read and bpf_dynptr_write > bpf: Add dynptr data slices > bpf: Dynptr support for ring buffers > bpf: Dynptr tests > > include/linux/bpf.h | 107 +++- > include/linux/bpf_verifier.h | 23 +- > include/uapi/linux/bpf.h | 100 ++++ > kernel/bpf/bpf_lsm.c | 4 +- > kernel/bpf/btf.c | 3 +- > kernel/bpf/cgroup.c | 4 +- > kernel/bpf/helpers.c | 190 ++++++- > kernel/bpf/ringbuf.c | 75 ++- > kernel/bpf/stackmap.c | 6 +- > kernel/bpf/verifier.c | 406 ++++++++++++-- > kernel/trace/bpf_trace.c | 20 +- > net/core/filter.c | 28 +- > scripts/bpf_doc.py | 2 + > tools/include/uapi/linux/bpf.h | 100 ++++ > .../testing/selftests/bpf/prog_tests/dynptr.c | 303 ++++++++++ > .../testing/selftests/bpf/progs/dynptr_fail.c | 527 ++++++++++++++++++ > .../selftests/bpf/progs/dynptr_success.c | 147 +++++ > 17 files changed, 1955 insertions(+), 90 deletions(-) > create mode 100644 tools/testing/selftests/bpf/prog_tests/dynptr.c > create mode 100644 tools/testing/selftests/bpf/progs/dynptr_fail.c > create mode 100644 tools/testing/selftests/bpf/progs/dynptr_success.c > KP, Florent, Brendan, You always wanted a way to work with runtime-sized BPF ringbuf samples without extra copies. This is the way we can finally do this with good usability and simplicity. Please take a look and provide feedback. Thanks! > -- > 2.30.2 >
