Get the latest tech news

The NX bit is not just about security

While I’m taking a short break from low-level programming, here’s a story by a friend of mine, Sonya, about debugging a seemingly impossible bug in ARM code. This bug hunting saga started several months ago. While developing a bare-metal hypervisor on ARM64 for postmarketOS, I hit a strange bug: if I enabled the CTR_EL0 intercept (which was the whole purpose of the HV, so could not be skipped), the phone would randomly lock itself up. After a few seconds, the watchdog kicked in and reset the system. At first I thought that the boot got slowed down so much that the system simply did not have enough time to boot, but disabling the watchdog did not help either (fortunately, the phone in question had removable battery, and I didn’t have to wait several hours for it to discharge). So, I started digging deeper.

None

Get the Android app