Re: [RFC PATCH bpf-next 3/3] selftests/bpf: add ftrace_permanent test

On Wed, Jul 29, 2026 at 9:23 AM Jiri Olsa [off-list ref] wrote:

On Tue, Jul 28, 2026 at 08:59:59PM -0400, Andrey Grodzovsky wrote:

quoted

Cover the FTRACE_OPS_FL_PERMANENT fix on BPF trampolines and
ftrace-based kprobes/kretprobes: attach a fentry, fexit, kprobe, and
kretprobe program in turn and confirm kernel.ftrace_enabled=0 is
refused with EBUSY while attached, then succeeds once detached. Also
confirm a new fentry/kprobe attach is itself refused while
ftrace_enabled=0 is already in effect.

kprobe.multi/kretprobe.multi/kprobe.session are intentionally not
covered, matching the production change's scope.

Skip the kprobe/kretprobe subtests when CONFIG_KPROBES_ON_FTRACE is
off (e.g. arm64), read back via skel->kconfig->CONFIG_KPROBES_ON_FTRACE
(same __kconfig idiom as progs/test_fill_link_info.c).

Assisted-by: Claude:claude-sonnet-5
Signed-off-by: Andrey Grodzovsky <redacted>
---

hi,
I have some links active already after boot which makes test to fail:

  [root@qemu-1 bpf]# echo 0 > /proc/sys/kernel/ftrace_enabled
  bash: echo: write error: Device or resource busy

  [root@qemu-1 bpf]# ./test_progs -t ftrace_permanent -v
  bpf_testmod.ko is already unloaded.
  Loading bpf_testmod.ko...
  Successfully loaded bpf_testmod.ko.
  test_ftrace_permanent:PASS:skel_open_and_load 0 nsec
  check_blocks_disable:PASS:attach_fentry 0 nsec
  check_blocks_disable:PASS:disable_refused 0 nsec
  check_blocks_disable:PASS:read_back 0 nsec
  check_blocks_disable:PASS:still_enabled 0 nsec
  check_blocks_disable:FAIL:disable_after_detach unexpected error: -16 (errno 16)
  check_blocks_disable:PASS:reenable 0 nsec
  #145/1   ftrace_permanent/fentry_blocks_disable:FAIL
  check_blocks_disable:PASS:attach_fexit 0 nsec
  check_blocks_disable:PASS:disable_refused 0 nsec
  check_blocks_disable:PASS:read_back 0 nsec
  check_blocks_disable:PASS:still_enabled 0 nsec
  check_blocks_disable:FAIL:disable_after_detach unexpected error: -16 (errno 16)
  check_blocks_disable:PASS:reenable 0 nsec
  #145/2   ftrace_permanent/fexit_blocks_disable:FAIL
  check_blocks_disable:PASS:attach_kprobe 0 nsec
  check_blocks_disable:PASS:disable_refused 0 nsec
  check_blocks_disable:PASS:read_back 0 nsec
  check_blocks_disable:PASS:still_enabled 0 nsec
  check_blocks_disable:FAIL:disable_after_detach unexpected error: -16 (errno 16)
  check_blocks_disable:PASS:reenable 0 nsec
  #145/3   ftrace_permanent/kprobe_blocks_disable:FAIL
  check_blocks_disable:PASS:attach_kretprobe 0 nsec
  check_blocks_disable:PASS:disable_refused 0 nsec
  check_blocks_disable:PASS:read_back 0 nsec
  check_blocks_disable:PASS:still_enabled 0 nsec
  check_blocks_disable:FAIL:disable_after_detach unexpected error: -16 (errno 16)
  check_blocks_disable:PASS:reenable 0 nsec
  #145/4   ftrace_permanent/kretprobe_blocks_disable:FAIL
  check_attach_while_disabled_refused:FAIL:disable unexpected error: -16 (errno 16)
  #145/5   ftrace_permanent/fentry_attach_while_disabled_refused:FAIL
  check_attach_while_disabled_refused:FAIL:disable unexpected error: -16 (errno 16)
  #145/6   ftrace_permanent/kprobe_attach_while_disabled_refused:FAIL
  #145     ftrace_permanent:FAIL
  Summary: 0/0 PASSED, 0 SKIPPED, 1 FAILED
  Successfully unloaded bpf_testmod.ko.

jirka

Thank you, Jiri. I will address this once the decision on whether to
proceed with this
route or, just make ftrace_enabled obsolete, is made.

Andrey