[Xen-devel] [PATCH OSSTEST v3 21/22] Debian: Arrange to be able to chainload a xen.efi from grub2

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

Xen cannot (currently) be booted directly via the usual multiboot
path on EFI systems of any arch. Instead it is necessary to either
launch xen.efi direct from the UEFI shell or to chainload it from
grub. In both cases the Xen command line as well as what would
normally be the multiboot modules (kernel+command line, XSM policy,
initrd) must be configured in a Xen configuration file.

By patching overlay/etc/grub.d/20_linux_xen that if a suitable xen.efi
is found in the EFI System Partition (as arrange by a previous patch)
a suitable entry is created in grub.cfg as well.

When parsing the grub.cfg look for such an entry into addition to the
regular/multiboot one and when necessary write the configuration file
based on the regular entry and return the chainload one such that it
gets booted.

This is currently enabled only for Jessie ARM64 systems.

Note that the 20_linux_xen change here is a bit specific to us and not
really generic enough to go upstream IMHO, hence I haven't.

Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
---
v3: Rewrap and reindent to avoid long lines
---
 Osstest/Debian.pm               | 77 +++++++++++++++++++++++++++++++++++++++--
 overlay/etc/grub.d/20_linux_xen | 21 +++++++++++
 2 files changed, 96 insertions(+), 2 deletions(-)

diff --git a/Osstest/Debian.pm b/Osstest/Debian.pm
index d7f8e9c..669cd36 100644
--- a/Osstest/Debian.pm
+++ b/Osstest/Debian.pm
@@ -400,12 +400,18 @@ sub setupboot_grub2 ($$$$) {
 
     my $rmenu= '/boot/grub/grub.cfg';
     my $kernkey= (defined $xenhopt ? 'KernDom0' : 'KernOnly');
- 
+
+    # Grub2 on Jessie/arm* doesn't do multiboot, so we must chainload.
+    my $need_uefi_chainload =
+        get_host_property($ho, "firmware") eq "uefi" &&
+        $ho->{Suite} =~ m/jessie/ && $r{arch} =~ m/^arm/;
+
     my $parsemenu= sub {
         my $f= bl_getmenu_open($ho, $rmenu, "$stash/$ho->{Name}--grub.cfg.1");
     
         my @offsets = (0);
         my $entry;
+        my $chainentry;
         my $submenu;
         while (<$f>) {
             next if m/^\s*\#/ || !m/\S/;
@@ -424,7 +430,13 @@ sub setupboot_grub2 ($$$$) {
                        (defined $xenhopt
                         ? qw(Title Hv KernDom0 KernVer)
                         : qw(Title Hv KernOnly KernVer));
-               if (@missing) {
+               if ($need_uefi_chainload && $entry->{Chainload}) {
+                   # Needs to be before check of @missing, since a
+                   # chained entry doesn't have anything useful in it
+                   logm("Found chainload entry at $entry->{StartLine}..$.");
+                   die "already got one" if $chainentry;
+                   $chainentry = $entry;
+               } elsif (@missing) {
                    logm("(skipping entry at $entry->{StartLine}..$.;".
                         " no @missing)");
                } elsif ($entry->{Hv} =~ m/xen-syms/) {
@@ -456,9 +468,15 @@ sub setupboot_grub2 ($$$$) {
                 $submenu={ StartLine =>$., MenuEntryPath => join ">", @offsets 
};
                 push @offsets,(0);
             }
+            if (m/^\s*chainloader\s*\/EFI\/osstest\/xen.efi/) {
+                die unless $entry;
+                $entry->{Hv}= $1;
+                $entry->{Chainload} = 1;
+            }
             if (m/^\s*multiboot\s*(?:\/boot)?\/(xen\S+)/) {
                 die unless $entry;
                 $entry->{Hv}= $1;
+                $entry->{Chainload} = 0;
             }
             if (m/^\s*multiboot\s*(?:\/boot)?\/(vmlinu[xz]-(\S+))\s+(.*)/) {
                 die unless $entry;
@@ -490,13 +508,68 @@ sub setupboot_grub2 ($$$$) {
            die unless $entry->{Hv};
        }
 
+       if ($need_uefi_chainload) {
+           die 'chainload entry not found' unless $chainentry;
+
+            # Propagate relevant fields of the main entry over to the
+            # chain entry for use of subsequent code.
+            foreach (qw(KernVer KernDom0 KernOnly KernOpts
+                        Initrd Xenpolicy)) {
+               next unless $entry->{$_};
+               die if $chainentry->{$_};
+               $chainentry->{$_} = $entry->{$_};
+            }
+
+            $entry = $chainentry;
+       }
+
         return $entry;
     };
 
 
     $bl->{UpdateConfig}= sub {
        my ( $ho ) = @_;
+
+        target_editfile_root($ho, '/etc/default/grub', sub {
+            while (<::EI>) {
+                next if m/^export GRUB_ENABLE_XEN_UEFI_CHAINLOAD\=/;
+                print ::EO;
+            }
+           print ::EO "export GRUB_ENABLE_XEN_UEFI_CHAINLOAD=\"osstest\"\n"
+               if $need_uefi_chainload;
+       });
+
        target_cmd_root($ho, "update-grub");
+
+       if ($need_uefi_chainload) {
+           my $entry= $parsemenu->();
+           my $xencfg = <<END;
+[global]
+default=osstest
+
+[osstest]
+options=$xenhopt
+kernel=vmlinuz $entry->{KernOpts}
+END
+            $xencfg .= "ramdisk=initrd.gz\n" if $entry->{Initrd};
+            $xencfg .= "xsm=xenpolicy\n" if $entry->{Xenpolicy};
+
+            target_putfilecontents_root_stash($ho,30,$xencfg,
+                               "/boot/efi/EFI/osstest/xen.cfg");
+
+            # /boot/efi should be a mounted EFI system partition, and
+            # /boot/efi/EFI/osstest/xen.efi should already exist. Hence no 
mkdir
+            # here.
+            target_cmd_root($ho,
+               
<<END.($entry->{Initrd}?<<END:"").($entry->{Xenpolicy}?<<END:""));
+set -ex
+cp -vL /boot/$entry->{KernDom0} /boot/efi/EFI/osstest/vmlinuz #/
+END
+cp -vL /boot/$entry->{Initrd} /boot/efi/EFI/osstest/initrd.gz #/
+END
+cp -vL /boot/$entry->{Xenpolicy} /boot/efi/EFI/osstest/xenpolicy #/
+END
+       }
     };
 
     $bl->{GetBootKern}= sub { return $parsemenu->()->{$kernkey}; };
diff --git a/overlay/etc/grub.d/20_linux_xen b/overlay/etc/grub.d/20_linux_xen
index aaead1b..30bdfc8 100755
--- a/overlay/etc/grub.d/20_linux_xen
+++ b/overlay/etc/grub.d/20_linux_xen
@@ -142,6 +142,27 @@ EOF
 }
 EOF
 }
+chain_xen_entry () {
+    vendor="$1"
+    if [ ! -f /boot/efi/EFI/$vendor/xen.efi ] ; then
+       return
+    fi
+    title=$(gettext_quoted "Chainload $vendor Xen")
+    xmessage="$(gettext_printf "Chainloading $vendor Xen ...")"
+    printf "menuentry '${title}' ${CLASS} {\n"
+    prepare_grub_to_access_device \
+       `${grub_probe} --target=device /boot/efi/EFI/$vendor/xen.efi` \
+       | grub_add_tab
+    cat <<EOF
+       echo    '$xmessage'
+       chainloader     /EFI/$vendor/xen.efi
+}
+EOF
+}
+
+for i in ${GRUB_ENABLE_XEN_UEFI_CHAINLOAD} ; do
+    chain_xen_entry $i
+done
 
 linux_list=`for i in /boot/vmlinu[xz]-* /vmlinu[xz]-* /boot/kernel-*; do
     if grub_file_is_not_garbage "$i"; then
-- 
2.1.4


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