Re: -EBUSY with some selftests on 5.7-rcX

[Mikko Ylinen <mikko.ylinen@linux.intel.com>]

On 06/05/2020 23:18, Andrii Nakryiko wrote:
> On Wed, May 6, 2020 at 12:28 PM Mikko Ylinen
> <mikko.ylinen@linux.intel.com> wrote:
>> The error seems to come from register_fentry() but I don't yet have
>> good logs what goes wrong.
> 
> Ok, this is actually useful. It's still few possibilities, but most
> seem to be related to ftrace subsystem. So here's portion of my
> Kconfig with FTRACE settings, see if you have some of those disabled
> and try to enable them, it might help. For instance, if you don't have
> a 5-byte preample in kernel functions (not sure which setting turns
> this on), bpf_arch_text_poke would also return EBUSY. Some of
> ftrace-specific code returns EBUSY in multiple places as well. So I'd
> start with trying to enable a lot of FTRACE stuff first:

With the following config changes:

-# CONFIG_FUNCTION_TRACER is not set
+CONFIG_FUNCTION_TRACER=y
+CONFIG_FUNCTION_GRAPH_TRACER=y
+CONFIG_DYNAMIC_FTRACE=y
+CONFIG_DYNAMIC_FTRACE_WITH_REGS=y
+CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS=y
+# CONFIG_FUNCTION_PROFILER is not set

# ./test_progs -t fentry_fexit
#13 fentry_fexit:OK
Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED
# ./test_progs -t test_lsm
#70 test_lsm:OK
Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED

Thanks!

Perhaps there could be a check whether the operation
is supported and if not,-ENOTSUPP is returned?

-- Mikko