Re: [PATCH net-next] modules: allow modprobe load regular elf binaries

[Andy Lutomirski]

On Tue, Mar 6, 2018 at 1:34 AM, Alexei Starovoitov <ast@xxxxxxxxxx> wrote:
> As the first step in development of bpfilter project [1] the request_module()
> code is extended to allow user mode helpers to be invoked. Idea is that
> user mode helpers are built as part of the kernel build and installed as
> traditional kernel modules with .ko file extension into distro specified
> location, such that from a distribution point of view, they are no different
> than regular kernel modules. Thus, allow request_module() logic to load such
> user mode helper (umh) modules via:
>
>   request_module("foo") ->
>     call_umh("modprobe foo") ->
>       sys_finit_module(FD of /lib/modules/.../foo.ko) ->
>         call_umh(struct file)
>

I assume I'm missing some context here, but why does this need to be
handled by the kernel rather than, say, a change to how modprobe
works?  I imagine that usermode tooling needs to change regardless
because the existing tools may get rather confused if a .ko "module"
is really a dynamically liked program.  I notice that you're using
ET_EXEC in your example, and that will probably avoid problems, but I
imagine that some distros would much rather use ET_DYN.