Libguestfs - Mar 2019 - [PATCH] v2v: linux: improve archtecture detection from modules (RHBZ#1690574)

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 (
-- 
2.20.1

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
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