Re: BPF memstore and bpf_validate_ext()

[Alexander Nasonov <alnsn%yandex.ru@localhost>]

Sorry for top-posting. I'm replying from my phone.

I've not looked at linux bpf before. I remember taking a quick look at 
bpf_jit_compile function but I didn't like emitting binary machine code with 
macro commands.

I spent few minutes today looking at linux code and I noticed few interesting 
things:

- They use negative offsets to access auxiliary data. So, there is a clear 
distinction between local memory store and external data. I don't think it's a 
new addition, though.
- They have a big enum of commands. Many of them translate to bpf commands but 
there are also special commands like load protocol number into A. There is a 
decoder from bpf but I have no clue how it works.
- Those commands are adapted to work with skbuf data.

Alex


20.12.13, 04:16, "David Laight" <david%l8s.co.uk@localhost>":
> 
> On Fri, Dec 20, 2013 at 01:28:12AM +0200, Mindaugas Rasiukevicius wrote:
> > Alexander Nasonov <alnsn%yandex.ru@localhost> wrote:
> > > 
> > > Well, if it wasn't needed for many year in bpf, why do we need it now? ;-)
> > > 
> > 
> > Because it was decided to use BPF byte-code for more applications and that
> > meant there is a need for improvements.  It is called evolution. :)
> 
> Has anyone here looked closely at the changes linux is making to bpf?
> 
>       David
> 
> -- 
> David Laight: david%l8s.co.uk@localhost


-- 
Alex