[ahartmetz]

I've had some ideas about avoiding format validation in IPC receivers if the data is encoded by trusted code, which is also the only code that has rights to send the IPC data / to connect to the receiver. I can't really think of an important problem that it would solve, though. DBus always validates received data, but it's not really meant or very suitable for large amounts of data anyway.

[twoodfin]

What I’m looking for is a way for a process to de/re-escalate its privileges to access memory, without an expensive context switch being required at the transition. The CPU would simply enforce different rules based on (say) the high-order bits of the instruction pointer.

Imagine a server process that wants to run some elaborate third-party content parser. It’d be great to be sure that no matter how buggy or malicious that code, it can’t leak the TLS keys.

Today, high-security architectures must use process isolation to achieve this kind of architectural guarantee, but even finely tuned IPC like L4’s is an order of magnitude slower than a predictable jump.

[gpderetta]

For a brief moment Intel supported MPX which did something similar.

You can also play tricks with the virtualization hardware, bit it need kernel support.

Eventually we will get segments back again.