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

On Tue, Mar 6, 2018 at 1:34 AM, Alexei Starovoitov [off-list ref] 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.