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.
I think it sets up a great base to parallelize further work.
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
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 work will be super useful for all bpf tracing too.
Sleepable progs are useful for tracing as well.
