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Date:      Mon, 14 Feb 2022 11:03:47 +0000
From:      Amit kumar <akamit91@hotmail.com>
To:        "freebsd-dtrace@FreeBSD.org" <freebsd-dtrace@FreeBSD.org>, "freebsd-arch@freebsd.org" <freebsd-arch@freebsd.org>
Cc:        "markj@FreeBSD.org" <markj@FreeBSD.org>
Subject:   dtrace fails to trace on FreeBSD-14(CURRENT) with ASLR and W^X
Message-ID:  <SJ0PR18MB49326C3D1DF915EB841CC2D8DC339@SJ0PR18MB4932.namprd18.prod.outlook.com>

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[-- Attachment #1 --]
Encountered this issue while running https://github.com/freebsd/freebsd-src/blob/main/cddl/contrib/opensolaris/cmd/dtrace/test/tst/common/pid/tst.emptystack.d

a somewhat simpler method to reproduce

configuration
file /usr/bin/find
/usr/bin/find: ELF 64-bit LSB shared object, x86-64, <.....>

kern.elf64.allow_wx: 0
kern.elf64.aslr.pie_enable: 1
kern.elf64.aslr.enable: 1

# dtrace -n pid92817:::entry
dtrace: description 'pid92817:::entry' matched 4380 probes
[2]  + trace trap (core dumped)  exec find / > /dev/null 2>&1

# exec find / > /dev/null 2>&1 &
[1] 85293
# dtrace -n pid85293:a.out::
dtrace: description 'pid85293:a.out::' matched 6828 probes
[1] + trace trap (core dumped) exec find / > /dev/null 2>&1
CPU ID FUNCTION:NAME
1 89149 find_execute:1f8

looking at find core in gdb
(gdb) p $_siginfo
$1 = {
  si_signo = 5,
  si_errno = 0,
  si_code = 3,
  .
  .
  .

Can someone help me understand why am I seeing core due to SIGTRAP TRAP_DTRACE ?

Regards
Amit

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<div style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
Encountered this issue while running&nbsp;<a href="https://github.com/freebsd/freebsd-src/blob/main/cddl/contrib/opensolaris/cmd/dtrace/test/tst/common/pid/tst.emptystack.d" id="LPNoLPOWALinkPreview">https://github.com/freebsd/freebsd-src/blob/main/cddl/contrib/opensolaris/cmd/dtrace/test/tst/common/pid/tst.emptystack.d</a></div>;
<div class="_Entity _EType_OWALinkPreview _EId_OWALinkPreview _EReadonly_1"></div>
<div style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
a somewhat simpler method to reproduce&nbsp;</div>
<div style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
configuration</div>
<div style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<span style="margin:0px;font-size:12pt">file&nbsp;<span style="margin:0px;background-color:rgb(255, 255, 255);display:inline !important">/usr/bin/find</span></span><br>
<span style="margin:0px;font-size:12pt">/usr/bin/find: ELF 64-bit LSB shared object, x86-64, &lt;.....&gt;</span><br>
</div>
<div style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<span style="margin:0px;font-size:12pt"><br>
</span></div>
<div style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
kern.elf64.allow_wx: 0
<div>kern.elf64.aslr.pie_enable: 1<br>
</div>
<div>kern.elf64.aslr.enable: 1</div>
<div><br>
</div>
</div>
<div style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
# dtrace -n pid92817:::entry
<div>dtrace: description 'pid92817:::entry' matched 4380 probes</div>
<span>[2] &nbsp;+ trace trap (core dumped) &nbsp;exec find / &gt; /dev/null 2&gt;&amp;1</span><br>
</div>
<div style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<span><br>
</span></div>
<div style=""><span style="display: inline !important; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"># exec find / &gt; /dev/null 2&gt;&amp;1 &amp;</span><br>
<span style="display: inline !important; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">[1] 85293</span><br style="box-sizing: border-box;">
<span style="display: inline !important; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"># dtrace -n pid85293:a.out::</span><br style="box-sizing: border-box;">
<span style="display: inline !important; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">dtrace: description 'pid85293:a.out::' matched 6828 probes</span><br style="box-sizing: border-box;">
<span style="display: inline !important; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">[1] + trace trap (core dumped) exec find / &gt; /dev/null 2&gt;&amp;1</span><br style="box-sizing: border-box;">
<span style="display: inline !important; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">CPU ID FUNCTION:NAME</span><br style="box-sizing: border-box;">
<span style="display: inline !important; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">1 89149 find_execute:1f8</span><br>
</div>
<div style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<span><br>
</span></div>
<div style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<span>looking at find core in gdb</span></div>
<div style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<span>(gdb) p $_siginfo
<div>$1 = {</div>
<div>&nbsp; si_signo = 5,</div>
<div>&nbsp; si_errno = 0,</div>
<div>&nbsp; si_code = 3,</div>
<div>&nbsp; .<br>
</div>
<div>&nbsp; .</div>
<div>&nbsp; .</div>
</span></div>
<div>
<div style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div style=""><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">Can someone help me understand why am I seeing core due to&nbsp;</span><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">SIGTRAP
 TRAP_DTRACE ?</span></div>
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<div style="font-family:Calibri,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
Regards</div>
<div style="font-family:Calibri,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
Amit</div>
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