The History of a Security Hole
Summary
A historical analysis of the I/O permission bitmap (IOPB) in the x86 Task State Segment (TSS), detailing how design choices, documentation gaps, and compiler padding led to real security holes across BSD-derived OSes from the 1990s through the Meltdown era. The article connects early Intel decisions to modern security lessons about data structure layout and per-process I/O permissions.