Re: [RFC] [PATCH 1/7] User Space Breakpoint Assistance Layer (UBP)

From: Avi Kivity
Date: Sun Jan 17 2010 - 14:34:35 EST

On 01/17/2010 05:03 PM, Peter Zijlstra wrote:

btw, an alternative is to require the caller to provide the address
space for this. If the caller is in another process, we need to allow
it to play with the target's address space (i.e. mmap_process()). I
don't think uprobes justifies this by itself, but mmap_process() can be
very useful for sandboxing with seccomp.
mmap_process() sounds utterly gross, one process playing with another
process's address space.. yuck!

This is debugging. We're playing with registers, we're playing with the cpu, we're playing with memory contents. Why not the address space as well?

For seccomp, this really should be generalized. Run a system call on behalf of another process, but don't let that process do anything to affect it. I think Google is doing something clever with one thread in seccomp mode and another unconstrained, but that's very hacky - you have to stop the constrained thread so it can't interfere with the live one.

Do not meddle in the internals of kernels, for they are subtle and quick to panic.

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