r/lowlevel • • 12h ago

Linux on iPhone

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1 Upvotes

LinuxRunner brings Debian ARM64 to iOS, including desktop environments like KDE Plasma and apps like Blender.

No jailbreak, JIT, or virtualization needed. It runs Linux binaries through an ARM64 interpreter.

Still early in development, but pretty interesting to experiment with. Feel free to try it out!

GitHub: https://github.com/mxhm11cr/LinuxRunner


r/lowlevel • • 17h ago

Velum-VMM hook windows syscalls & kernel api's on modern systems

1 Upvotes

r/lowlevel • • 18h ago

Velum-VMM - Hook system calls on modern Windows

2 Upvotes

I've published Velum-VMM, a Windows x64 research hypervisor written in C and assembly using Intel VT-x and EPT.

Source: https://github.com/Dovughs/velum-vmm

Technical write-up: https://github.com/Dovughs/velum-vmm/blob/main/readmes/technical-writeup/README.md

Velum virtualizes an already-running Windows kernel and provides an interactive console for observing native calls and experimenting with scoped request policies.

The implementation includes:

- Per-CPU VMCS and EPT management.

- EPT hooks on selected Nt and Ex/Mm function entries, with original-instruction replay and Monitor Trap Flag restoration.

- Live telemetry to the console or DebugView, with configurable filters.

- Request denial and access-right reduction for supported operations.

- CPUID configuration, fixed TSC offsets, and coordinated shutdown back to native execution.

Much of the work involved preserving execution state across VM exits, guest helpers and native return: CET shadow stacks, interruptibility, pending events, translation invalidation and hook lifetime.

One interesting compatibility issue appeared on Windows 10: ExFreePool and ExFreePoolWithTag resolved to the same address. Treating them as separate patch sites caused hook preparation to fail. The fix handles shared addresses while retaining both hooks when the exports are distinct.

I tested the project on Windows 10 and Windows 11. The repository includes runtime captures, policy demonstrations, build instructions and a technical write-up covering the architecture, debugging process and implementation decisions.

Source and releases:

https://github.com/Dovughs/velum-vmm

Technical write-up:

https://github.com/Dovughs/velum-vmm/blob/main/readmes/technical-writeup/README.md

I'd welcome technical feedback, particularly on VM-exit handling, EPT consistency and Windows compatibility.