[bpf-next,v2,0/5] bpf, x86: allow function arguments up to 14 for TRACING

Message

Menglong Dong June 2, 2023, 6:59 a.m. UTC

From: Menglong Dong <[e-mail]>

For now, the BPF program of type BPF_PROG_TYPE_TRACING can only be used
on the kernel functions whose arguments count less than 6. This is not
friendly at all, as too many functions have arguments count more than 6.

Therefore, let's enhance it by increasing the function arguments count
allowed in arch_prepare_bpf_trampoline(), for now, only x86_64.

In the 1th patch, we make MAX_BPF_FUNC_ARGS 14, according to our
statistics.

In the 2th patch, we make arch_prepare_bpf_trampoline() support to copy
function arguments in stack for x86 arch. Therefore, the maximum
arguments can be up to MAX_BPF_FUNC_ARGS for FENTRY and FEXIT.

And the 3-5th patches are for the testcases of the 2th patch.

Changes since v1:
- change the maximun function arguments to 14 from 12
- add testcases (Jiri Olsa)
- instead EMIT4 with EMIT3_off32 for "lea" to prevent overflow

Menglong Dong (5):
  bpf: make MAX_BPF_FUNC_ARGS 14
  bpf, x86: allow function arguments up to 14 for TRACING
  libbpf: make BPF_PROG support 15 function arguments
  selftests/bpf: rename bpf_fentry_test{7,8,9} to bpf_fentry_test_ptr*
  selftests/bpf: add testcase for FENTRY/FEXIT with 6+ arguments

 arch/x86/net/bpf_jit_comp.c                   | 96 ++++++++++++++++---
 include/linux/bpf.h                           |  9 +-
 net/bpf/test_run.c                            | 40 ++++++--
 tools/lib/bpf/bpf_helpers.h                   |  9 +-
 tools/lib/bpf/bpf_tracing.h                   | 10 +-
 .../selftests/bpf/prog_tests/bpf_cookie.c     | 24 ++---
 .../bpf/prog_tests/kprobe_multi_test.c        | 16 ++--
 .../testing/selftests/bpf/progs/fentry_test.c | 50 ++++++++--
 .../testing/selftests/bpf/progs/fexit_test.c  | 51 ++++++++--
 .../selftests/bpf/progs/get_func_ip_test.c    |  2 +-
 .../selftests/bpf/progs/kprobe_multi.c        | 12 +--
 .../bpf/progs/verifier_btf_ctx_access.c       |  2 +-
 .../selftests/bpf/verifier/atomic_fetch_add.c |  4 +-
 13 files changed, 249 insertions(+), 76 deletions(-)