netdev - Re: [PATCH 5/5] bpf: Allow to resolve bpf trampoline in unwind

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Message-ID: <20200107130546.GI290055@krava>
Date:   Tue, 7 Jan 2020 14:05:46 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Jiri Olsa <jolsa@...nel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, Andrii Nakryiko <andriin@...com>,
        Yonghong Song <yhs@...com>, Martin KaFai Lau <kafai@...com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        David Miller <davem@...hat.com>, bjorn.topel@...el.com
Subject: Re: [PATCH 5/5] bpf: Allow to resolve bpf trampoline in unwind

On Mon, Jan 06, 2020 at 03:46:40PM -0800, Alexei Starovoitov wrote:
> On Sun, Dec 29, 2019 at 03:37:40PM +0100, Jiri Olsa wrote:
> > When unwinding the stack we need to identify each
> > address to successfully continue. Adding latch tree
> > to keep trampolines for quick lookup during the
> > unwind.
> > 
> > Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> ...
> > +bool is_bpf_trampoline(void *addr)
> > +{
> > +	return latch_tree_find(addr, &tree, &tree_ops) != NULL;
> > +}
> > +
> >  struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
> >  {
> >  	struct bpf_trampoline *tr;
> > @@ -65,6 +98,7 @@ struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
> >  	for (i = 0; i < BPF_TRAMP_MAX; i++)
> >  		INIT_HLIST_HEAD(&tr->progs_hlist[i]);
> >  	tr->image = image;
> > +	latch_tree_insert(&tr->tnode, &tree, &tree_ops);
> 
> Thanks for the fix. I was thinking to apply it, but then realized that bpf
> dispatcher logic has the same issue.
> Could you generalize the fix for both?
> May be bpf_jit_alloc_exec_page() can do latch_tree_insert() ?
> and new version of bpf_jit_free_exec() is needed that will do latch_tree_erase().
> Wdyt?

I need to check the dispatcher code, but seems ok.. will check

jirka