Re: Too many PMC implementations

[David Holland <dholland-tech%netbsd.org@localhost>]

On Sat, Aug 25, 2018 at 11:26:07AM +0100, Alexander Nasonov wrote:
 > > There is already a Lua-powered solution for traces in Linux: ktap. It
 > > uses nice rules written natively in Lua.. however it seems to be
 > > abandoned in favor of eBPF.
 > 
 > I see two potential problems with using Lua bytecode:
 > 
 > 1. It's not standartised and it will very likely change in future versions

That doesn't really matter as long as you're only using one version at
a time...

 > 2. There is no bpf_validate for Lua bytecode. In fact, Lua team abandoned
 >    an idea of bytecode validation few years ago. From Lua 5.3 manual:
 > 
 >    Lua does not check the consistency of binary chunks. Maliciously
 >    crafted binary chunks can crash the interpreter.

Are we talking about installing untrusted/unprivileged kernel trace
logic? Because that seems like a bad idea, or at least a very hard
thing to get right... and if not, it doesn't matter if there's a
validator.

(Also, isn't EBPF not really validatable either, or am I mixing it
up with something else?)

-- 
David A. Holland
dholland%netbsd.org@localhost