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From: "wcohen at redhat dot com" <sourceware-bugzilla@sourceware.org>
To: systemtap@sourceware.org
Subject: [Bug translator/25972] New: stap -v -L misses probe points
Date: Mon, 11 May 2020 15:32:03 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D25972

            Bug ID: 25972
           Summary: stap -v -L misses probe points
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: translator
          Assignee: systemtap at sourceware dot org
          Reporter: wcohen at redhat dot com
  Target Milestone: ---

Created attachment 12525
  --> https://sourceware.org/bugzilla/attachment.cgi?id=3D12525&action=3Ded=
it
Reproducer for stap missing statement lines

When debugging pr25549 I noticed that there were some cases where it appear=
ed
systemtap missed listing lines for instruction that had multiple debuginfo
views for the same instruction.  this can be replicated on fedora 32 with t=
he

$ rpm -q gcc systemtap elfutils
gcc-10.1.1-1.fc32.x86_64
systemtap-4.3-0.20200211git91ffb97ad335.fc32.x86_64
elfutils-0.179-2.fc32pr25549.x86_64
$ gcc -O2 -g pr25549b.cxx -o pr25549b
$ stap -v -L 'process("./pr25549b").statement("*@*:*")'
Pass 1: parsed user script and 502 library scripts using
442584virt/211916res/12772shr/199236data kb, in 450usr/70sys/554real ms.
process("/home/wcohen/pr25549b").statement("main@/home/wcohen/pr25549b.cxx:=
10")
/* pc=3D.absolute+0x1040 */ $argc:int $argv:char**
process("/home/wcohen/pr25549b").statement("main@/home/wcohen/pr25549b.cxx:=
12")
/* pc=3D.absolute+0x104e */ $argc:int $argv:char**
Pass 2: analyzed script: 2 probes, 0 functions, 0 embeds, 0 globals using
451284virt/222188res/13700shr/207936data kb, in 60usr/0sys/69real ms.

However, there are multiple views for the instructions:

$ readelf --debug-dump=3Ddecodedline pr25549b
Contents of the .debug_line section:

CU: pr25549b.cxx:
File name                            Line number    Starting address    Vie=
w=20=20=20
Stmt
pr25549b.cxx                                  10            0x401040=20=20=
=20=20=20=20=20=20=20=20=20
   x
pr25549b.cxx                                  11            0x401040       =
1=20=20=20
   x
pr25549b.cxx                                   3            0x401040       =
2=20=20=20
   x
pr25549b.cxx                                   5            0x401040       =
3=20=20=20
   x
pr25549b.cxx                                  10            0x401040       4
pr25549b.cxx                                   5            0x401044=20=20=
=20=20=20=20=20=20
pr25549b.cxx                                   5            0x401049=20=20=
=20=20=20=20=20=20
pr25549b.cxx                                   6            0x40104e=20=20=
=20=20=20=20=20=20=20=20=20
   x
pr25549b.cxx                                  12            0x40104e       =
1=20=20=20
   x
pr25549b.cxx                                  13            0x40104e       2
pr25549b.cxx                                  13            0x401055=20=20=
=20=20=20=20=20=20


gdb allows setting breakpoints at those alternative view for the instructio=
ns.=20
I would expect that systemtap would also allow probe points at those points.

--=20
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