netdev - Re: [PATCH 12/18] bpf: Add trampolines to kallsyms

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Date:   Thu, 27 Feb 2020 09:08:05 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Martin KaFai Lau <kafai@...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>, Song Liu <songliubraving@...com>,
        Jakub Kicinski <kuba@...nel.org>,
        David Miller <davem@...hat.com>,
        Björn Töpel <bjorn.topel@...el.com>,
        John Fastabend <john.fastabend@...il.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCH 12/18] bpf: Add trampolines to kallsyms

On Wed, Feb 26, 2020 at 10:26:40PM -0800, Martin KaFai Lau wrote:

SNIP

> > +	ksym->start = (unsigned long) data;
> > +	ksym->end = ksym->start + BPF_IMAGE_SIZE;
> > +	bpf_ksym_add(ksym);
> > +	perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF, ksym->start,
> > +			   BPF_IMAGE_SIZE, false, ksym->name);
> > +}
> > +
> > +void bpf_image_ksym_del(struct bpf_ksym *ksym)
> > +{
> > +	bpf_ksym_del(ksym);
> > +	perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF, ksym->start,
> > +			   BPF_IMAGE_SIZE, true, ksym->name);
> > +}
> > +
> >  struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
> >  {
> >  	struct bpf_trampoline *tr;
> > @@ -131,6 +148,7 @@ 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;
> > +	INIT_LIST_HEAD_RCU(&tr->ksym.lnode);
> >  out:
> >  	mutex_unlock(&trampoline_mutex);
> >  	return tr;
> > @@ -267,6 +285,14 @@ static enum bpf_tramp_prog_type bpf_attach_type_to_tramp(enum bpf_attach_type t)
> >  	}
> >  }
> >  
> > +static void bpf_trampoline_ksym_add(struct bpf_trampoline *tr)
> > +{
> > +	struct bpf_ksym *ksym = &tr->ksym;
> > +
> > +	snprintf(ksym->name, KSYM_NAME_LEN, "bpf_trampoline_%llu", tr->key);
> Do you have plan to support struct_ops which is also using
> trampoline (in bpf_struct_ops_map_update_elem())?
> Any idea on the name? bpf_struct_ops_<map_id>? 

right, I was wondering we should also do that,
I'll check on it

jirka