[PATCH v2 bpf-next 0/4] Fix global subprog PTR_TO_CTX arg handling

[Andrii Nakryiko <andrii@kernel.org>]

Fix confusing and incorrect inference of PTR_TO_CTX argument type in BPF
global subprogs. For some program types (iters, tracepoint, any program type
that doesn't have fixed named "canonical" context type) when user uses (in
a correct and valid way) a pointer argument to user-defined anonymous struct
type, verifier will incorrectly assume that it has to be PTR_TO_CTX argument.
While it should be just a PTR_TO_MEM argument with allowed size calculated
from user-provided (even if anonymous) struct.

This did come up in practice and was very confusing to users, so let's prevent
this going forward. We had to do a slight refactoring of
btf_get_prog_ctx_type() to make it easy to support a special s390x KPROBE use
cases. See details in respective patches.

v1->v2:
  - special-case typedef bpf_user_pt_regs_t handling for KPROBE programs,
    fixing s390x after changes in patch #2.

Andrii Nakryiko (4):
  bpf: simplify btf_get_prog_ctx_type() into btf_is_prog_ctx_type()
  bpf: handle bpf_user_pt_regs_t typedef explicitly for PTR_TO_CTX
    global arg
  bpf: don't infer PTR_TO_CTX for programs with unnamed context type
  selftests/bpf: add anonymous user struct as global subprog arg test

 include/linux/btf.h                           | 17 ++++---
 kernel/bpf/btf.c                              | 45 +++++++++++++------
 kernel/bpf/verifier.c                         |  2 +-
 .../bpf/progs/test_global_func_ctx_args.c     | 19 ++++++++
 .../bpf/progs/verifier_global_subprogs.c      | 29 ++++++++++++
 5 files changed, 88 insertions(+), 24 deletions(-)

-- 
2.39.3