Libguestfs - Aug 2020 - Re: [PATCH v2] v2v: fix UEFI bootloader for linux guests

v2:
  Rich, I hope I've done all modifications according to your comments,
namely:
    * moved the code from linux_bootloaders to convert_linux
    * made minor code modifications 
---

Not all UEFI guests can survive conversion, because of lost bootloader
information in UEFI NVRAM. But some guest can cope with this because they
have a fallback bootloader and use UEFI Removable Media Boot Behavior to load
(see https://uefi.org/sites/default/files/resources/UEFI_Spec_2_8_A_Feb14.pdf
3.5.1.1 Removable Media Boot Behavior). If UEFI firmware can't find
a bootloader in its settings it uses the removable media boot behavior to
find a bootloader.

We can fix the guests which don't have such a fallback loader by providing
a temporary one. This bootloader is used for the first boot only, then the
conversion script restores the initial bootloader settings and removes the
temporary loader.

Signed-off-by: Denis Plotnikov <dplotnikov@virtuozzo.com>
---
 v2v/convert_linux.ml      | 123 ++++++++++++++++++++++++++++++++++++++
 v2v/linux_bootloaders.ml  |   7 +++
 v2v/linux_bootloaders.mli |   4 ++
 3 files changed, 134 insertions(+)

diff --git a/v2v/convert_linux.ml b/v2v/convert_linux.ml
index e91ae120f..045afa98b 100644
--- a/v2v/convert_linux.ml
+++ b/v2v/convert_linux.ml
@@ -1122,6 +1122,129 @@ shutdown -h -P +0
       Linux.augeas_reload g
     );
 
+    (* Some linux uefi setups can't boot after conversion because of
+       lost uefi boot entries. The uefi boot entries are stored in uefi
+       NVRAM. The NVRAM content isn't a part of vm disk content and
+       usualy can't be converted alongside the vm.
+       If a vm doesn't have uefi fallback path
(/EFI/BOOT/BOOT<arch>.efi)
+       the vm is unbootable after conversion.
+       The following code tries to make an uefi fallback path for
+       a uefi linux vm.
+    *)
+    match inspect.i_firmware with
+    | I_UEFI _ -> (
+      (* Standard uefi fallback path *)
+      let uefi_fallback_path = "/boot/efi/EFI/BOOT/" in
+
+      (* Helper function checks if 'source' contains 's' *)
+      let contains source s = (
+        let re = Str.regexp_string s in
+        try
+          ignore (Str.search_forward re source 0);
+          true
+        with Not_found -> false
+      ) in
+
+      let cant_fix_uefi () +        info (f_"Can't fix UEFI
bootloader. VM may not boot.")
+      in
+
+      let get_uefi_arch_suffix = function
+        | "x86_64" -> Some "X64"
+        | "x86_32" -> Some "X32"
+        | _ -> None
+      in
+
+      match get_uefi_arch_suffix inspect.i_arch with
+      | None -> cant_fix_uefi ()
+      | Some suffix -> (
+        let uefi_fallback_name +          sprintf "%sBOOT%s.EFI"
uefi_fallback_path suffix in
+
+        let file_exists file +          if g#exists file then
+            true
+          else (
+            info (f_"Can't find file: '%s' needed for UEFI
fixing")
+                 file;
+            false )
+        in
+
+        let grub_config = bootloader#get_config_file () in
+
+        let grub_path +          String.sub grub_config 0 (String.rindex
grub_config '/') in
+
+        if g#exists uefi_fallback_name then
+          (* don't do anything if uefi fallback exists *)
+          ()
+        else (
+          info (f_"Fixing UEFI bootloader.");
+          match inspect.i_distro, inspect.i_major_version with
+            | "centos", 6 ->
+              (* to make a bootable uefi centos 6 we need to
+               * copy grub.efi and grub.conf to UEFI fallback path
+               * and rename them to BOOT<arch>.efi and
BOOT<arch>.conf
+               * correspondingly *)
+              let uefi_grub_name = String.concat "" [grub_path;
"/grub.efi"] in
+              let uefi_grub_conf = String.concat "" [
+                                     String.sub uefi_fallback_name 0
+                                     (String.rindex uefi_fallback_name
'.');
+                                     ".conf" ] in
+              if file_exists uefi_grub_name && file_exists grub_config
then (
+                g#mkdir_p uefi_fallback_path;
+                g#cp uefi_grub_name uefi_fallback_name;
+                g#cp grub_config uefi_grub_conf;
+                let fix_script = sprintf
+"#!/bin/bash
+efibootmgr -c -L \"CentOS 6\"
+rm -rf %s" uefi_fallback_path in
+                Firstboot.add_firstboot_script
+                  g inspect.i_root "fix uefi boot" fix_script)
+              else
+                cant_fix_uefi ()
+            | "ubuntu", 14 ->
+              (* to make a bootable uefi ubuntu 14 we need to
+               * copy shim<arch>.efi to UEFI fallback path
+               * and rename it to BOOT<arch>.efi, also we copy
+               * grub.efi and grub.cfg to UEFI fallback path without renaming
*)
+              let arch_suffix = String.lowercase_ascii suffix in
+
+              let shim +                String.concat "" [grub_path;
"/shim"; arch_suffix; ".efi"] in
+              let uefi_grub_name +                String.concat ""
[grub_path; "/grub"; arch_suffix; ".efi"] in
+
+              if file_exists shim && file_exists uefi_grub_name
+                                  && file_exists grub_config then (
+                g#mkdir_p uefi_fallback_path;
+                g#cp shim uefi_fallback_name;
+                g#cp uefi_grub_name uefi_fallback_path;
+                g#cp grub_config uefi_fallback_path;
+                (* if the shim is at the standard path, clean up uefi fixing
+                 * if not, then just don't clean up and leave the temp
loader
+                 * at UEFI fallback path for simplicity
+                 *)
+                if contains shim "/boot/efi/EFI/ubuntu/shim" then
+                  let fix_script = sprintf
+"#!/bin/bash
+sudo efibootmgr -c -L ubuntu -l \\\\EFI\\\\ubuntu\\\\shim%s.efi
+rm -rf %s" arch_suffix uefi_fallback_path in
+                  Firstboot.add_firstboot_script
+                    g inspect.i_root "fix uefi boot" fix_script
+                else
+                  ())
+              else
+                cant_fix_uefi ()
+          | _, _ ->
+            info (f_"No UEFI fix rule for %s %d")
+                 inspect.i_distro inspect.i_major_version;
+            cant_fix_uefi ()
+        )
+      )
+    )
+    | I_BIOS -> ();
+
     (* Delete blkid caches if they exist, since they will refer to the old
      * device names.  blkid will rebuild these on demand.
      *
diff --git a/v2v/linux_bootloaders.ml b/v2v/linux_bootloaders.ml
index de3d107e9..4ca28782b 100644
--- a/v2v/linux_bootloaders.ml
+++ b/v2v/linux_bootloaders.ml
@@ -36,6 +36,7 @@ class virtual bootloader = object
   method virtual configure_console : unit -> unit
   method virtual remove_console : unit -> unit
   method update () = ()
+  method virtual get_config_file : unit -> string
 end
 
 (* Helper function for SUSE: remove (hdX,X) prefix from a path. *)
@@ -184,6 +185,9 @@ object
     loop paths;
 
     g#aug_save ()
+
+  method get_config_file () +    grub_config
 end
 
 (** The method used to get and set the default kernel in Grub2. *)
@@ -342,6 +346,9 @@ object (self)
 
   method update ()      ignore (g#command [| grub2_mkconfig_cmd;
"-o"; grub_config |])
+
+  method get_config_file () +    grub_config
 end
 
 (* Helper type used in detect_bootloader. *)
diff --git a/v2v/linux_bootloaders.mli b/v2v/linux_bootloaders.mli
index 30cdfe3c7..d9f0be8e1 100644
--- a/v2v/linux_bootloaders.mli
+++ b/v2v/linux_bootloaders.mli
@@ -44,6 +44,10 @@ class virtual bootloader : object
   (** Update the bootloader: For grub2 only this runs the
       [grub2-mkconfig] command to rebuild the configuration.  This
       is not necessary for grub-legacy. *)
+
+  method virtual get_config_file : unit -> string
+  (** Returns the path to the bootloader config file,
+      e.g /boot/grub/grub.cfg *)
 end
 (** Encapsulates a Linux boot loader as object. *)
 
-- 
2.17.0

On Fri, Jul 24, 2020 at 03:36:58PM +0300, Denis Plotnikov
wrote:
> v2:
>   Rich, I hope I've done all modifications according to your comments,
namely:
>     * moved the code from linux_bootloaders to convert_linux
>     * made minor code modifications 
Thanks - I pushed it.

I squashed in some changes which are stylistic only (hopefully - I
hope I correctly understood what the "contains" function was doing).

The diff versus your patch is attached.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
libguestfs lets you edit virtual machines.  Supports shell scripting,
bindings from many languages.  http://libguestfs.org

A bit late but regarding '| "x86_32" -> Some
"X32"',
Is "x86_32" actually a valid i_arch? I was under the impression that
it is
being set to i386.

Thanks!

On Fri, Jul 24, 2020 at 6:20 PM Denis Plotnikov <dplotnikov@virtuozzo.com>
wrote:
>
>
> On 24.07.2020 17:20, Richard W.M. Jones wrote:
> > On Fri, Jul 24, 2020 at 03:36:58PM +0300, Denis Plotnikov wrote:
> >> v2:
> >>    Rich, I hope I've done all modifications according to your
comments,
> namely:
> >>      * moved the code from linux_bootloaders to convert_linux
> >>      * made minor code modifications
> > Thanks - I pushed it.
> >
> > I squashed in some changes which are stylistic only (hopefully - I
> > hope I correctly understood what the "contains" function was
doing).
> >
> > The diff versus your patch is attached.
> >
> > Rich.
> >
> Ok, thanks!
>
> Denis
>
> _______________________________________________
> Libguestfs mailing list
> Libguestfs@redhat.com
> https://www.redhat.com/mailman/listinfo/libguestfs
>
>

On Wed, Aug 26, 2020 at 03:19:22PM +0300, Sam Eiderman
wrote:
> A bit late but regarding '| "x86_32" -> Some
"X32"',
> Is "x86_32" actually a valid i_arch? I was under the impression
that it is
> being set to i386.
You're correct, the only valid value for i_arch on i386 is
"i386":

https://libguestfs.org/guestfs.3.html#guestfs_file_architecture

I guess no one really uses i386, but I'll push a fix shortly, thanks.

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