linux-kernel - Re: [PATCH 11/12] perf tools: Reuse shared eBPF dso objects

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Message-ID: <ed2f881b-c1b2-e6da-5c23-fc1eb4db131f@intel.com>
Date:   Wed, 17 Apr 2019 09:55:25 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Andi Kleen <ak@...ux.intel.com>,
        Song Liu <songliubraving@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [PATCH 11/12] perf tools: Reuse shared eBPF dso objects

On 17/04/19 9:51 AM, Jiri Olsa wrote:
> On Wed, Apr 17, 2019 at 09:35:32AM +0300, Adrian Hunter wrote:
>> On 16/04/19 7:01 PM, Jiri Olsa wrote:
>>> The eBPF program can be loaded multiple times
>>> with the same name (tag). We can share dso
>>> objects for those programs.
>>
>> Doesn't a eBPF program get recompiled differently every time it is loaded?
> 
> yes, but those with same tag are identical

But won't recompiled eBPF programs be different due to blinded constants?
Or perhaps in the future other code randomization?

> 
> jirka
> 
>>
>>>
>>> Link: http://lkml.kernel.org/n/tip-3damf8vq1dryhtpbk5b06jpt@git.kernel.org
>>> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
>>> ---
>>>  tools/perf/util/machine.c | 14 +++++++++++---
>>>  1 file changed, 11 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
>>> index d4aa44489011..a60653827891 100644
>>> --- a/tools/perf/util/machine.c
>>> +++ b/tools/perf/util/machine.c
>>> @@ -23,6 +23,7 @@
>>>  #include "linux/hash.h"
>>>  #include "asm/bug.h"
>>>  #include "bpf-event.h"
>>> +#include "dso.h"
>>>  
>>>  #include "sane_ctype.h"
>>>  #include <symbol/kallsyms.h>
>>> @@ -699,11 +700,18 @@ static int machine__process_ksymbol_register(struct machine *machine,
>>>  
>>>  	map = map_groups__find(&machine->kmaps, event->ksymbol_event.addr);
>>>  	if (!map) {
>>> -		map = dso__new_map(event->ksymbol_event.name);
>>> -		if (!map)
>>> +		struct dso *dso;
>>> +
>>> +		dso = dsos__findnew(&machine->dsos, event->ksymbol_event.name);
>>> +		if (!dso)
>>>  			return -ENOMEM;
>>>  
>>> -		map->start = event->ksymbol_event.addr;
>>> +		map = map__new2(event->ksymbol_event.addr, dso);
>>> +		if (!map) {
>>> +			dso__put(dso);
>>> +			return -ENOMEM;
>>> +		}
>>> +
>>>  		map->end = map->start + event->ksymbol_event.len;
>>>  		map_groups__insert(&machine->kmaps, map);
>>>  	}
>>>
>>
>