{{Header}}
{{Title|title=
Debugging Systemd Seccomp
}}
{{#seo:
|description=Seccomp Issues
}}
<div class="mininav">
* [[systemd|systemd]]
* [[seccomp|seccomp]]
</div>
{{intro|
Seccomp Issues
}}
Depends on architecture. What works on Intel/AMD64 (<code>amd64</code>) might not work on <code>arm64</code>, and vice versa.

{{IconSet|h1|1}} Install <code>auditd</code>.

{{Install_Package|package=
auditd
}}

{{IconSet|h1|2}} To monitor systemd seccomp issues:

{{CodeSelect|code=
sudo journalctl _AUDIT_TYPE_NAME=SECCOMP -f
}}

{{IconSet|h1|3}} Sample issue

'''Bold''' added.

<blockquote>SECCOMP auid=4294967295 uid=108 gid=118 ses=4294967295 subj==/usr/bin/sdwdate (enforce) pid=9740 comm="sdwdate" exe="/usr/bin/python3.7" sig=31 arch=c0000015 '''syscall=140''' compat=0 ip=0x7fff96cc7df4 code=0x0</blockquote>

{{IconSet|h1|4}} Find out the syscall number.

The relevant part of the log output snippet above is <code>syscall=<u>140</u></code>. The syscall number will very likely be different in your case.

{{IconSet|h1|5}} Translate syscall number into syscall name.

This can be done with the <code>ausyscall</code> tool.

* <u>Note:</u> Replace <code>140</code> with the actual syscall number.
* [https://manpages.debian.org//ausyscall <code>ausyscall</code>] man page.

{{CodeSelect|code=
ausyscall 140
}}

{{IconSet|h1|6}} Expected output.

Sample output. Example:

<pre>
getpriority
</pre>

In this example, the name of the syscall is <code>getpriority</code>. In your case, the name of the syscall will likely be different.

{{IconSet|h1|7}} Add syscall name to systemd unit file.

Once you have the syscall name, add it to the system call whitelist in the systemd unit of the malfunctioning process.

<u>Note:</u> Replace <code>sdwdate</code> with the systemd unit name you are debugging.

sdwdate example:

* {{CodeSelect|code=
sudoedit /usr/lib/systemd/system/sdwdate.service && sudo systemctl daemon-reload && sudo systemctl restart sdwdate && sudo systemctl --no-pager --full status sdwdate
}}

kloak example:

* {{CodeSelect|code=
sudoedit /usr/lib/systemd/system/kloak.service && sudo systemctl daemon-reload && sudo systemctl restart kloak && sudo systemctl --no-pager --full status kloak
}}

The <code>SystemCallFilter=</code> value needs to be adjusted. Append the missing syscall name. <ref>
{{IconSet|h1|7}} Reload the systemd manager configuration.

This makes systemd re-read unit files after you edited them.

{{CodeSelect|code=
sudo systemctl daemon-reload
}}

{{IconSet|h1|8}} Restart the service to apply the changes.

This stops and starts <code>kloak</code> so it runs with the updated systemd unit settings (such as an adjusted <code>SystemCallFilter=</code>).

{{CodeSelect|code=
sudo systemctl restart kloak
}}

{{IconSet|h1|9}} Check service status and logs for errors.

This shows whether <code>kloak</code> is active, and displays recent journal output that can reveal remaining seccomp denials or other failures.

{{CodeSelect|code=
sudo systemctl --no-pager --full status kloak
}}

{{IconSet|h1|10}} Done.

Systemd has reloaded unit files, the <code>kloak</code> service was restarted, and its status was checked.
</ref>

{{IconSet|h1|8}} Check.

If the systemd unit is functional now, everything is okay. Otherwise, rinse and repeat.

See also: [https://github.com/Whonix/kloak/pull/1 Whonix kloak pull request 1]

= Other Syscall Number to Name Lookup Methods =
Usually not required. <ref>
The syscall table for your particular machine is defined in a header file. Open {{CodeSelect|inline=true|code=
/usr/include/ARCH-linux-gnu/asm/unistd.h
}}, replacing <code>ARCH</code>. This should give you a pointer (in the form of a <code>#include</code> statement) to the file containing the syscall table. You may have to "dig" more than one level deep to find it. The correct file will contain a list of numbers and syscall names that looks something like this:

{{CodeSelect|code=
#define __NR_read 0
#define __NR_write 1
#define __NR_open 2
#define __NR_close 3
#define __NR_stat 4
#define __NR_fstat 5
#define __NR_lstat 6
}}

In this case we know that <code>read</code> has syscall number <code>0</code>, <code>write</code> has syscall number <code>1</code>, etc. Find the syscall number reported in the journal, and determine its corresponding name from the list.

If you cannot find the syscall table on your system, you may need to install <code>linux-libc-dev</code>.
</ref> <ref>
There are online syscall tables, such as [https://chromium.googlesource.com/chromiumos/docs/+/master/constants/syscalls.md Chromium OS syscall tables] and [https://marcin.juszkiewicz.com.pl/download/tables/syscalls.html Marcin Juszkiewicz syscall tables]. However, these are not guaranteed to be accurate for your system. It is highly recommended to use the syscall table for your distribution as documented above.
</ref>

= Footnotes =
<references/>
{{Footer}}
[[Category:Documentation]]