Re: [PATCH bpf-next v8 09/10] tools/bpf: add a test for bpf_get_stack with raw tracepoint prog

From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Y Song <ys114321@gmail.com>
Cc: Yonghong Song <yhs@fb.com>, Alexei Starovoitov <ast@fb.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	netdev <netdev@vger.kernel.org>,
	kernel-team@fb.com
Subject: Re: [PATCH bpf-next v8 09/10] tools/bpf: add a test for bpf_get_stack with raw tracepoint prog
Date: Sat, 28 Apr 2018 12:06:23 -0700	[thread overview]
Message-ID: <20180428190622.7cxrsqmxwn33cscf@ast-mbp> (raw)
In-Reply-To: <CAH3MdRVpmJE9gqz=41fddmxjRw_ZF0sAqiewEHnYxWYij0jfew@mail.gmail.com>

On Sat, Apr 28, 2018 at 11:17:30AM -0700, Y Song wrote:
> On Sat, Apr 28, 2018 at 9:56 AM, Alexei Starovoitov
> <alexei.starovoitov@gmail.com> wrote:
> > On Sat, Apr 28, 2018 at 12:02:04AM -0700, Yonghong Song wrote:
> >> The test attached a raw_tracepoint program to sched/sched_switch.
> >> It tested to get stack for user space, kernel space and user
> >> space with build_id request. It also tested to get user
> >> and kernel stack into the same buffer with back-to-back
> >> bpf_get_stack helper calls.
> >>
> >> Whenever the kernel stack is available, the user space
> >> application will check to ensure that the kernel function
> >> for raw_tracepoint ___bpf_prog_run is part of the stack.
> >>
> >> Signed-off-by: Yonghong Song <yhs@fb.com>
> > ...
> >> +static int get_stack_print_output(void *data, int size)
> >> +{
> >> +     bool good_kern_stack = false, good_user_stack = false;
> >> +     const char *expected_func = "___bpf_prog_run";
> >
> > so the test works with interpreter only?
> > I guess that's ok for now, but needs to fixed for
> > configs with CONFIG_BPF_JIT_ALWAYS_ON=y
> 
> I did not test CONFIG_BPF_JIT_ALWAYS_ON=y.
> I can have a followup patch for this if the patch set does not need respin.

I was thinking to apply the set and do the fix in the follow up,
but testing it with jit_enable=1 I don't see it's failing,
so something is wrong with the test.
Also get_stack_raw_tp_action() keeps spawning new 'dd' in the background
which is not killed after test stops.
Please fix both issues in respin.