linux-kernel - Re: [PATCH 0/5] perf: add support for capturing skid IP

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]

Message-ID: <20170616160630.GE4789@tassilo.jf.intel.com>
Date:   Fri, 16 Jun 2017 09:06:30 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     Stephane Eranian <eranian@...gle.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "mingo@...e.hu" <mingo@...e.hu>,
        "Liang, Kan" <kan.liang@...el.com>, Jiri Olsa <jolsa@...hat.com>
Subject: Re: [PATCH 0/5] perf: add support for capturing skid IP

On Thu, Jun 15, 2017 at 11:52:07PM -0700, Stephane Eranian wrote:
> Andi,
> 
> On Thu, Jun 15, 2017 at 4:18 PM, Andi Kleen <ak@...ux.intel.com> wrote:
> >> Looking at this approach, the user interface is straightforward,
> >> implementation in the x86 code is a bit more hairy because of the way
> >> the branch_stack is captured, via the cpuc->lbr_entries. If you assume
> >> that SKID_IP cannot be used with any other branch stack mode, then it
> >> is easy. It becomes messy if you don't.
> >
> > That should be fine. After all if you have real LBRs you don't need
> > the skid IP.
> >
> Yes, you still do. This is not the same thing. LBR captures only taken branches.
> I care about taken AND non-taken branches and I don't want to sample on a
> non-taken event, assuming it is available.

Ok that's a reasonable argument for reporting it separately, like
in your original patch.

-Andi