On 04-Mar 14:17, Alexei Starovoitov wrote:
> On Wed, Mar 04, 2020 at 08:18:46PM +0100, KP Singh wrote:
> >
> > Here is an example of how a fmod_ret program behaves:
> >
> > int func_to_be_attached(int a, int b)
> V> { <--- do_fentry
> >
> > do_fmod_ret:
> > <update ret by calling fmod_ret>
> > if (ret != 0)
> > goto do_fexit;
> >
> > original_function:
> >
> > <side_effects_happen_here>
> >
> > } <--- do_fexit
> >
> > ALLOW_ERROR_INJECTION(func_to_be_attached, ERRNO)
> >
> > The fmod_ret program attached to this function can be defined as:
> >
> > SEC("fmod_ret/func_to_be_attached")
> > int BPF_PROG(func_name, int a, int b, int ret)
> > {
> > // This will skip the original function logic.
> > return -1;
> > }
>
> Applied to bpf-next. Thanks.
Thanks.
>
> I think it sets up a great base to parallelize further work.
Totally Agreed!
>
> 1. I'm rebasing my sleepable BPF patches on top.
> It's necessary to read enviroment variables without the
> 'opportunistic copy before hand' hack I saw in your github tree
:) Sleepable BPF would indeed make it much simpler.
> to do bpf_get_env_var() helper.
>
> 2. please continue on LSM_HOOK patches to go via security tree.
>
> 3. we need a volunteer to generalize bpf_sk_storage to task and inode structs.
This is quite important, especially for some of the examples we had
brought up.
I can take a look at the generalization of bpf_sk_storage.
Thanks!
- KP
> This work will be super useful for all bpf tracing too.
> Sleepable progs are useful for tracing as well.
