[PATCH bpf-next v4 0/5] writable contexts for bpf raw tracepoints

[Matt Mullins]

This adds an opt-in interface for tracepoints to expose a writable context to
BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE programs that are attached, while
supporting read-only access from existing BPF_PROG_TYPE_RAW_TRACEPOINT
programs, as well as from non-BPF-based tracepoints.

The initial motivation is to support tracing that can be observed from the
remote end of an NBD socket, e.g. by adding flags to the struct nbd_request
header.  Earlier attempts included adding an NBD-specific tracepoint fd, but in
code review, I was recommended to implement it more generically -- as a result,
this patchset is far simpler than my initial try.

v3->v4:
  * fixed a silly copy/paste typo in include/trace/events/bpf_test_run.h
    (_TRACE_NBD_H -> _TRACE_BPF_TEST_RUN_H)
  * fixed incorrect/misleading wording in patch 1's commit message,
    since the pointer cannot be directly dereferenced in a
    BPF_PROG_TYPE_RAW_TRACEPOINT
  * cleaned up the error message wording if the prog_tests fail
  * Addressed feedback from Yonghong
    * reject non-pointer-sized accesses to the buffer pointer
    * use sizeof(struct nbd_request) as one-byte-past-the-end in
      raw_tp_writable_reject_nbd_invalid.c
    * use BPF_MOV64_IMM instead of BPF_LD_IMM64

v2->v3:
  * Andrew addressed Josef's comments:
    * C-style commenting in nbd.c
    * Collapsed identical events into a single DECLARE_EVENT_CLASS.
      This saves about 2kB of kernel text

v1->v2:
  * add selftests
    * sync tools/include/uapi/linux/bpf.h
  * reject variable offset into the buffer
  * add string representation of PTR_TO_TP_BUFFER to reg_type_str

Andrew Hall (1):
  nbd: add tracepoints for send/receive timing

Matt Mullins (4):
  bpf: add writable context for raw tracepoints
  nbd: trace sending nbd requests
  tools: sync bpf.h
  selftests: bpf: test writable buffers in raw tps

 MAINTAINERS                                   |   1 +
 drivers/block/nbd.c                           |  13 +++
 include/linux/bpf.h                           |   2 +
 include/linux/bpf_types.h                     |   1 +
 include/linux/tracepoint-defs.h               |   1 +
 include/trace/bpf_probe.h                     |  27 ++++-
 include/trace/events/bpf_test_run.h           |  50 ++++++++
 include/trace/events/nbd.h                    | 107 ++++++++++++++++++
 include/uapi/linux/bpf.h                      |   1 +
 kernel/bpf/syscall.c                          |   8 +-
 kernel/bpf/verifier.c                         |  31 +++++
 kernel/trace/bpf_trace.c                      |  24 ++++
 net/bpf/test_run.c                            |   4 +
 tools/include/uapi/linux/bpf.h                |   1 +
 tools/lib/bpf/libbpf.c                        |   1 +
 tools/lib/bpf/libbpf_probes.c                 |   1 +
 .../raw_tp_writable_reject_nbd_invalid.c      |  42 +++++++
 .../bpf/prog_tests/raw_tp_writable_test_run.c |  80 +++++++++++++
 .../selftests/bpf/verifier/raw_tp_writable.c  |  34 ++++++
 19 files changed, 425 insertions(+), 4 deletions(-)
 create mode 100644 include/trace/events/bpf_test_run.h
 create mode 100644 include/trace/events/nbd.h
 create mode 100644 tools/testing/selftests/bpf/prog_tests/raw_tp_writable_reject_nbd_invalid.c
 create mode 100644 tools/testing/selftests/bpf/prog_tests/raw_tp_writable_test_run.c
 create mode 100644 tools/testing/selftests/bpf/verifier/raw_tp_writable.c

-- 
2.17.1