Run PowerJoular on Intel/AMD Linux without root/sudo

[adelnoureddine]

Access to RAPL data is restricted in Linux kernel to only privileged users (sudo/root), in order to avoid the PLATYPUS vulnerability.

To avoid running PowerJoular with sudo or root, a proposed approach is to set RAPL files to read for all users. Read status is reset on reboot, so the proposition is to add this right to /etc/sysfs.conf : mode class/powercap/intel-rapl:0/energy_uj = 0444.

In PowerJoular, we read 2 files for each RAPL domain: name and energy_uj. Both files need to have read rights.

Mainly theses files (if they exist):

/sys/class/powercap/intel-rapl/intel-rapl:1/energy_uj
/sys/class/powercap/intel-rapl/intel-rapl:0/energy_uj
/sys/class/powercap/intel-rapl/intel-rapl:0/intel-rapl:0:2/energy_uj
/sys/class/powercap/intel-rapl/intel-rapl:1/name
/sys/class/powercap/intel-rapl/intel-rapl:0/name
/sys/class/powercap/intel-rapl/intel-rapl:0/intel-rapl:0:2/name

If you only use the PowerJoular systemd service, which needs to be enabled and run as root/sudo as all systemd services, then you can keep your system unchanged as the service will run with privileged rights and writes data to /tmp folder as we explained in the project's page.

• Add workaround for sysfs.conf in documentation page & readme
• Add a script or simpler documentation to change permissions for RAPL file on boot for sysf.conf.