[Libguestfs] [PATCH] v2v: linux: improve archtecture detection from modules (RHBZ#1690574)

[Richard W.M. Jones]

On Wed, Mar 20, 2019 at 12:36:16PM +0100, Pino Toscano wrote:
> Try to look for a well known kernel module (so far only virtio, or kvm)
> to use for detecting the architecture of a kernel.  This way, we can
> avoid picking 3rd party modules that cause troubles.
> ---
>  v2v/linux_kernels.ml | 30 +++++++++++++++++++++++++++---
>  1 file changed, 27 insertions(+), 3 deletions(-)
> 
> diff --git a/v2v/linux_kernels.ml b/v2v/linux_kernels.ml
> index 3313aabc7..f1b9bdd97 100644
> --- a/v2v/linux_kernels.ml
> +++ b/v2v/linux_kernels.ml
> @@ -185,11 +185,35 @@ let detect_kernels (g : G.guestfs) inspect family bootloader =
>               assert (List.length modules > 0);
>  
>               (* Determine the kernel architecture by looking at the
> -              * architecture of an arbitrary kernel module.
> +              * architecture of a kernel module.
> +              *
> +              * To avoid architecture detection issues with 3rd party
> +              * modules (RHBZ#1690574), try to pick one of the well
> +              * known modules, if available.  Otherwise, an arbitrary
> +              * module is used.
>                *)
>               let arch =
> -               let any_module = modpath ^ List.hd modules in
> -               g#file_architecture any_module in
> +               (* Well known kernel modules. *)
> +               let candidates = [ "virtio"; "kvm" ] in
> +               let all_candidates = List.flatten (
> +                 List.map (
> +                   fun f ->
> +                     [ "/" ^ f ^ ".o"; "/" ^ f ^ ".ko"; "/" ^ f ^ ".ko.xz" ]
> +                 ) candidates
> +               ) in
> +               let candidate =
> +                 try
> +                   List.find (
> +                     fun m ->
> +                       List.exists (String.is_suffix m) all_candidates
> +                   ) modules
> +                 with Not_found ->
> +                   (* No known module found, pick an arbitrary one
> +                    * (the first).
> +                    *)
> +                   List.hd modules in
> +               let candidate = modpath ^ candidate in
> +               g#file_architecture candidate in
>  
>               (* Just return the module names, without path or extension. *)
>               let modules = List.filter_map (

ACK.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-builder quickly builds VMs from scratch
http://libguestfs.org/virt-builder.1.html