Re: [PATCH v6 net-next 1/6] net: filter: add "load 64-bit immediate" eBPF instruction

[David Miller]

From: Alexei Starovoitov <ast@xxxxxxxxxxxx>
Date: Mon, 25 Aug 2014 18:00:53 -0700

> add BPF_LD_IMM64 instruction to load 64-bit immediate value into a register.

I think you need to rethink this.

I understand that you want to be able to compile arbitrary C code into
eBPF, but you have to restrict strongly what data the eBPF code can get
to.

Arbitrary pointer loads is asking for trouble.

Instead I would rather you look into a model like what the quake
engine uses for it's VM.

Namely, the program can do loads and stores from/to a data section,
but all of them are validated to be in the range of the VM program's
image.

eBPF programs should only be able to access things using either:

1) Well defined entry/exit points for control transfer

2) Load/Store within a private limited data segment range used
   only by the eBPF program

I don't want the eBPF program to be able to get "out of it's box"
in any way shape or form.

And besides, you're only making this thing as an optimization right?
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