Re: [PATCH] Remove kretprobe_trampoline_holder.

On Tue, 2016-03-29 at 15:34 -0300, Thiago Jung Bauermann wrote:

Am Dienstag, 29 März 2016, 10:45:57 schrieb Michael Ellerman:

quoted

On Mon, 2016-03-28 at 17:29 -0300, Thiago Jung Bauermann wrote:

quoted

If I do s/_do_fork/._do_fork/ in kprobe_ftrace.tc then all ftrace kprobe
tests pass:

OK. We fixed that in 'perf probe', but not if you're using the sysfs file
directly.

Do you want to write a patch for ftracetest to try and handle it? I guess
you'd try "_do_fork" and if that fails then try "._do_fork", and maybe
only if uname -m says you're running on ppc64?

I did write a patch yesterday (included below for reference), but then I
noticed that the other ftrace tests use _do_fork and they work fine (I guess
because of the fix you mentioned). I think that ideally the ftrace filter
mechanism should work with dot symbols as well as regular symbols.

I think this could work by creating a mechanism analogous to the
ARCH_HAS_SYSCALL_MATCH_SYM_NAME one in trace_syscalls.c. Ftrace_match_record
could call it to adjust the symbol name (like kprobe_lookup_name) before
calling ftrace_match.

But I’m wondering if it’s really worth the effort and maybe patching the
testcase is enough? Also, I don’t know whether my idea would have any
side effects.

It'd be nice if it worked properly. Reusing kprobe_lookup_name() looks like it
would be the right fix, given this is "kprobe events".

cheers