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

Adrian Hunter
2019-04-17T06:56:49Z

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@kernel.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);
>>> }
>>>
>>
>