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
