linux-kernel - Re: [PATCH v4 4/6] perf arm-spe: Assign kernel time to synthesized event

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 15 Apr 2021 17:46:31 +0300
From:   James Clark <james.clark@....com>
To:     Leo Yan <leo.yan@...aro.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Al Grant <Al.Grant@....com>,
        John Garry <john.garry@...wei.com>,
        Will Deacon <will@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Dave Martin <Dave.Martin@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 4/6] perf arm-spe: Assign kernel time to synthesized
 event



On 12/04/2021 12:10, Leo Yan wrote:
> In current code, it assigns the arch timer counter to the synthesized
> samples Arm SPE trace, thus the samples don't contain the kernel time
> but only contain the raw counter value.
> 
> To fix the issue, this patch converts the timer counter to kernel time
> and assigns it to sample timestamp.
> 
> Signed-off-by: Leo Yan <leo.yan@...aro.org>
> ---
>  tools/perf/util/arm-spe.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/arm-spe.c b/tools/perf/util/arm-spe.c
> index 23714cf0380e..c13a89f06ab8 100644
> --- a/tools/perf/util/arm-spe.c
> +++ b/tools/perf/util/arm-spe.c
> @@ -234,7 +234,7 @@ static void arm_spe_prep_sample(struct arm_spe *spe,
>  	struct arm_spe_record *record = &speq->decoder->record;
>  
>  	if (!spe->timeless_decoding)
> -		sample->time = speq->timestamp;
> +		sample->time = tsc_to_perf_time(record->timestamp, &spe->tc);


I noticed that in arm_spe_recording_options() the TIME sample bit is set regardless of any options.
I don't know of a way to remove this, and if there isn't, does that mean that all the code in this
file that looks at spe->timeless_decoding is untested and has never been hit?

Unless there is a way to get a perf file with only the AUXTRACE event and no others? I think that one
might have no timestamp set. Otherwise other events will always have timestamps so spe->timeless_decoding
is always false.



>  
>  	sample->ip = record->from_ip;
>  	sample->cpumode = arm_spe_cpumode(spe, sample->ip);
>