netdev - Re: [PATCH v5 perf,bpf 08/15] perf, bpf: save btf in a rbtree in perf

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Date:   Mon, 4 Mar 2019 21:31:32 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Song Liu <songliubraving@...com>
Cc:     Networking <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "ast@...nel.org" <ast@...nel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        Kernel Team <Kernel-team@...com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "acme@...hat.com" <acme@...hat.com>,
        "jolsa@...nel.org" <jolsa@...nel.org>,
        "namhyung@...nel.org" <namhyung@...nel.org>
Subject: Re: [PATCH v5 perf,bpf 08/15] perf, bpf: save btf in a rbtree in
 perf_env

On Mon, Mar 04, 2019 at 07:43:50PM +0000, Song Liu wrote:
> 
> 
> > On Mar 4, 2019, at 5:52 AM, Jiri Olsa <jolsa@...hat.com> wrote:
> > 
> > On Wed, Feb 27, 2019 at 09:06:36PM -0800, Song Liu wrote:
> >> btf contains information necessary to annotate bpf programs. This patch
> >> saves btf for bpf programs loaded in the system.
> >> 
> >> Signed-off-by: Song Liu <songliubraving@...com>
> >> ---
> >> tools/perf/util/bpf-event.c | 24 ++++++++++++++
> >> tools/perf/util/bpf-event.h |  7 ++++
> >> tools/perf/util/env.c       | 65 +++++++++++++++++++++++++++++++++++++
> >> tools/perf/util/env.h       |  4 +++
> >> 4 files changed, 100 insertions(+)
> >> 
> >> diff --git a/tools/perf/util/bpf-event.c b/tools/perf/util/bpf-event.c
> >> index ce81b2c43a51..370b830f2433 100644
> >> --- a/tools/perf/util/bpf-event.c
> >> +++ b/tools/perf/util/bpf-event.c
> >> @@ -34,6 +34,29 @@ int machine__process_bpf_event(struct machine *machine __maybe_unused,
> >> 	return 0;
> >> }
> >> 
> >> +static int perf_env__fetch_btf(struct perf_env *env,
> >> +			       u32 btf_id,
> >> +			       struct btf *btf)
> >> +{
> >> +	struct btf_node *node;
> >> +	u32 data_size;
> >> +	const void *data;
> >> +
> >> +	data = btf__get_raw_data(btf, &data_size);
> >> +
> >> +	node = malloc(data_size + sizeof(struct btf_node));
> >> +
> >> +	if (!node)
> >> +		return -1;
> >> +
> >> +	node->id = btf_id;
> >> +	node->data_size = data_size;
> >> +	memcpy(node->data, data, data_size);
> > 
> > why don't we store just struct btf itself?
> > 
> > thanks,
> > jirka
> 
> In current libbpf design, definition of "struct btf" is private 
> to tools/lib/bpf/btf.c. So we cannot copy the struct itself. 

ok

jirka