From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <sourceware-bugzilla@sourceware.org>
Received: by sourceware.org (Postfix, from userid 48)
 id C93963894C05; Sun, 27 Sep 2020 18:48:21 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org C93963894C05
From: "barrdetwix at gmail dot com" <sourceware-bugzilla@sourceware.org>
To: systemtap@sourceware.org
Subject: [Bug translator/26670] New: In "end" probe, symbol lookup for user
 stacks is broken (print_usyms/print_ustack functions)
Date: Sun, 27 Sep 2020 18:48:21 +0000
X-Bugzilla-Reason: AssignedTo
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: systemtap
X-Bugzilla-Component: translator
X-Bugzilla-Version: unspecified
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: barrdetwix at gmail dot com
X-Bugzilla-Status: UNCONFIRMED
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-26670-6586@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-BeenThere: systemtap@sourceware.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Systemtap mailing list <systemtap.sourceware.org>
List-Unsubscribe: <https://sourceware.org/mailman/options/systemtap>,
 <mailto:systemtap-request@sourceware.org?subject=unsubscribe>
List-Archive: <https://sourceware.org/pipermail/systemtap/>
List-Help: <mailto:systemtap-request@sourceware.org?subject=help>
List-Subscribe: <https://sourceware.org/mailman/listinfo/systemtap>,
 <mailto:systemtap-request@sourceware.org?subject=subscribe>
X-List-Received-Date: Sun, 27 Sep 2020 18:48:21 -0000

https://sourceware.org/bugzilla/show_bug.cgi?id=3D26670

            Bug ID: 26670
           Summary: In "end" probe, symbol lookup for user stacks is
                    broken (print_usyms/print_ustack functions)
           Product: systemtap
           Version: unspecified
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: translator
          Assignee: systemtap at sourceware dot org
          Reporter: barrdetwix at gmail dot com
  Target Milestone: ---

I have a script that saves backtraces and tries defers resolving symbols un=
til
the end, to reduce the overhead.

But it seems that resolving user symbols only works in regular probes, not =
in
the "end" probe. There is no error, the symbols just fail to resolve.
Note that there is no such problem for kernel stacks.

Version info:
Systemtap translator/driver (version 4.4/0.181, commit
release-4.3-75-g747902edd81a)
Linux 5.8.0-2-amd64 #1 SMP Debian 5.8.10-1 (2020-09-19) x86_64

Please see the following reproducer script (and the output I get below):

// stap_end_userstack.stp
global ustack;

probe vfs.read {
    ustack =3D ubacktrace();

    println("--- In vfs probe");
    print_usyms(ustack);
    exit();
}

probe end {
    println("--- In end probe");
    print_usyms(ustack);
}


$ sudo stap -d /bin/ntfs-3g -d /lib/x86_64-linux-gnu/libpthread-2.31.so -v
stap_end_userstack.stp
Pass 1: parsed user script and 476 library scripts using
93152virt/78928res/9964shr/69012data kb, in 140usr/30sys/170real ms.
Pass 2: analyzed script: 2 probes, 6 functions, 6 embeds, 1 global using
253976virt/241524res/11684shr/229836data kb, in 1500usr/130sys/1642real ms.
Pass 3: translated to C into
"/tmp/stapri4GCL/stap_7a0d3cf3937b410061615c1e75142f3c_4334_src.c" using
253976virt/241720res/11880shr/229836data kb, in 330usr/20sys/343real ms.
Pass 4: compiled C into "stap_7a0d3cf3937b410061615c1e75142f3c_4334.ko" in
8990usr/570sys/6673real ms.
Pass 5: starting run.
WARNING: Missing unwind data for a module, rerun with 'stap -d
/lib/x86_64-linux-gnu/libc-2.31.so'
--- In vfs probe
 0x7f65a1cb504e : __read+0xe/0xa0 [/lib/x86_64-linux-gnu/libpthread-2.31.so]
 0x55b8595b3012 : 0x55b8595b3012 [/bin/ntfs-3g+0x1a012/0x23000]
 0x55b8595ad26d : 0x55b8595ad26d [/bin/ntfs-3g+0x1426d/0x23000]
 0x55b85959f35f : 0x55b85959f35f [/bin/ntfs-3g+0x635f/0x23000]
 0x7f65a1aafcca : 0x7f65a1aafcca
[/lib/x86_64-linux-gnu/libc-2.31.so+0x26cca/0x1c1000]
--- In end probe
 0x7f65a1cb504e : 0x7f65a1cb504e
 0x55b8595b3012 : 0x55b8595b3012
 0x55b8595ad26d : 0x55b8595ad26d
 0x55b85959f35f : 0x55b85959f35f
 0x7f65a1aafcca : 0x7f65a1aafcca
Pass 5: run completed in 10usr/70sys/677real ms.

As you can see, the user stack resolves correctly in a regular probe, but n=
ot
in the end probe.

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