Kage: Google Experimenting With Linux Driver Isolation Using In-Kernel LFI Sandboxes

Google engineers are experimenting with Linux kernel device driver isolation using in-kernel sandboxes leveraging LLVM's Lightweight Fault Isolation (LFI) functionality. Google engineers have been spearheading the work on Kage as a kernel subsystem offering in-kernel sandboxes that are backed by LLVM's new Lightweight Fault Isolation technology. Lightweight Fault Isolation is a software-based fault isolation tech originally developed by Stanford with Google's support for in-process isolation of native code and lower overhead than traditional sandboxes. LLVM LFI is fully upstream for AArch64 while the x86/x86_64 LFI support is aiming to be finished by LLVM 24. The Kage'd drivers have the same hardware privilege level and address space as the rest of the Linux kernel but via the compiler-based LFI is confined to a subset of the virtual memory space. Pairing Kage with VirtIO in an inverted manner of traditional VirtIO use, or "VKage", has already been used to prototype working NVMe, network, and WiFi in the driver sandboxed environments. But more testing needs to be done on the performance side and also exploring if sandboxing GPU drivers would be feasible. Google may be looking at (V)Kage moving forward for Android device drivers. Those curious about Google's Kage for Linux device driver isolation can learn more via the LPC 2026 presentation. There is also this ACM.org paper from over the summer outlining Kage.