From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <systemtap-return-26627-listarch-systemtap=sources.redhat.com@sourceware.org>
Received: (qmail 39016 invoked by alias); 2 Jul 2019 15:38:56 -0000
Mailing-List: contact systemtap-help@sourceware.org; run by ezmlm
Precedence: bulk
List-Id: <systemtap.sourceware.org>
List-Subscribe: <mailto:systemtap-subscribe@sourceware.org>
List-Post: <mailto:systemtap@sourceware.org>
List-Help: <mailto:systemtap-help@sourceware.org>, <http://sourceware.org/lists.html#faqs>
Sender: systemtap-owner@sourceware.org
Received: (qmail 38981 invoked by uid 48); 2 Jul 2019 15:38:52 -0000
From: "me at serhei dot io" <sourceware-bugzilla@sourceware.org>
To: systemtap@sourceware.org
Subject: [Bug bpf/24758] New: stapbpf-next: more robust and generous userspace interpreter
Date: Tue, 02 Jul 2019 15:38:00 -0000
X-Bugzilla-Reason: AssignedTo
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: systemtap
X-Bugzilla-Component: bpf
X-Bugzilla-Version: unspecified
X-Bugzilla-Keywords:
X-Bugzilla-Severity: normal
X-Bugzilla-Who: me at serhei dot io
X-Bugzilla-Status: NEW
X-Bugzilla-Resolution:
X-Bugzilla-Priority: P2
X-Bugzilla-Assigned-To: systemtap at sourceware dot org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags:
X-Bugzilla-Changed-Fields: bug_id short_desc product version bug_status bug_severity priority component assigned_to reporter target_milestone
Message-ID: <bug-24758-6586@http.sourceware.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://sourceware.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
X-SW-Source: 2019-q3/txt/msg00000.txt.bz2

https://sourceware.org/bugzilla/show_bug.cgi?id=3D24758

            Bug ID: 24758
           Summary: stapbpf-next: more robust and generous userspace
                    interpreter
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: bpf
          Assignee: systemtap at sourceware dot org
          Reporter: me at serhei dot io
  Target Milestone: ---

The BPF interpreter (in stapbpf/bpfinterp.cxx) is still a cobbled-together
thing with some holes and probable bugs lurking. It needs a pass over the c=
ode
to be brought up to standard bytecode-interpreter 'best practice'. No need =
for
fancy performance tricks, but:
- It could be more robust (runtime errors handled properly, memory manageme=
nt
with fewer pitfalls).
- It could be more generous (some of the kernel bpf restrictions are still
duplicated in userspace where there's no need for them -- pr24528 allows us=
 to
generate different code for userspace probes).
- It could maybe use fewer hacky C++ interfaces.
- It could maybe do with refactoring to include some code from the lkm runt=
ime
where functionality is being duplicated. (We already use lkm code in-usersp=
ace
for the dyninst backend, so reusing it here is not totally shocking.)

The only thing that's needed for certain is 'more robust' so I am filing ju=
st
one PR for now to track this work.

--=20
You are receiving this mail because:
You are the assignee for the bug.