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Replace grub-menu-builder with a much faster version
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The old GRUB menu builder script is quite slow, typically taking
several seconds.  This is a real annoyance since it's run every time
you switch to a new configuration.  Therefore this patch replaces the
Bash script with a much faster Perl script.  In a VirtualBox test, the
execution time went from 2.7s to 0.1s.  The Perl version is also more
correct because it uses XML to get the GRUB configuration (through
builtins.toXML), so there are no shell escaping issues.

The new script currently lacks support for subconfigurations defined
through "nesting.children".
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@edolstra
edolstra committed Jul 24, 2012
1 parent b3b6b8a commit f07f221
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217 changes: 217 additions & 0 deletions modules/installer/grub/grub-menu-builder.pl
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use strict;
use warnings;
use XML::LibXML;
use File::Basename;
use File::Path;
use File::stat;
use File::Copy;
use IO::File;
use POSIX;
use Cwd;

my $defaultConfig = $ARGV[1] or die;

my $dom = XML::LibXML->load_xml(location => $ARGV[0]);

sub get { my ($name) = @_; return $dom->findvalue("/expr/attrs/attr[\@name = '$name']/*/\@value"); }

my $grub = get("grub");
my $grubVersion = int(get("version"));
my $extraConfig = get("extraConfig");
my $extraPerEntryConfig = get("extraPerEntryConfig");
my $extraEntries = get("extraEntries");
my $extraEntriesBeforeNixOS = get("extraEntriesBeforeNixOS") eq "true";
my $splashImage = get("splashImage");
my $configurationLimit = int(get("configurationLimit"));
my $copyKernels = get("copyKernels") eq "true";
my $timeout = int(get("timeout"));
my $defaultEntry = int(get("default"));

die "unsupported GRUB version\n" if $grubVersion != 1 && $grubVersion != 2;

mkpath("/boot/grub", 0, 0700);


# Discover whether /boot is on the same filesystem as / and
# /nix/store. If not, then all kernels and initrds must be copied to
# /boot, and all paths in the GRUB config file must be relative to the
# root of the /boot filesystem. `$bootRoot' is the path to be
# prepended to paths under /boot.
my $bootRoot = "/boot";
if (stat("/")->dev != stat("/boot")->dev) {
$bootRoot = "";
$copyKernels = 1;
} elsif (stat("/boot")->dev != stat("/nix/store")->dev) {
$copyKernels = 1;
}


# Generate the header.
my $conf .= "# Automatically generated. DO NOT EDIT THIS FILE!\n";

if ($grubVersion == 1) {
$conf .= "
default $defaultEntry
timeout $timeout
";
if ($splashImage) {
copy $splashImage, "/boot/background.xpm.gz" or die "cannot copy $splashImage to /boot\n";
$conf .= "splashimage $bootRoot/background.xpm.gz\n";
}
}

else {
copy "$grub/share/grub/unicode.pf2", "/boot/grub/unicode.pf2" or die "cannot copy unicode.pf2 to /boot/grub: $!\n";

$conf .= "
if [ -s \$prefix/grubenv ]; then
load_env
fi
# ‘grub-reboot’ sets a one-time saved entry, which we process here and
# then delete.
if [ \"\${saved_entry}\" ]; then
# The next line *has* to look exactly like this, otherwise KDM's
# reboot feature won't work properly with GRUB 2.
set default=\"\${saved_entry}\"
set saved_entry=
set prev_saved_entry=
save_env saved_entry
save_env prev_saved_entry
set timeout=1
else
set default=$defaultEntry
set timeout=$timeout
fi
if loadfont $bootRoot/grub/unicode.pf2; then
set gfxmode=640x480
insmod gfxterm
insmod vbe
terminal_output gfxterm
fi
";

if ($splashImage) {
# FIXME: GRUB 1.97 doesn't resize the background image if it
# doesn't match the video resolution.
copy $splashImage, "/boot/background.png" or die "cannot copy $splashImage to /boot\n";
$conf .= "
insmod png
if background_image $bootRoot/background.png; then
set color_normal=white/black
set color_highlight=black/white
else
set menu_color_normal=cyan/blue
set menu_color_highlight=white/blue
fi
";
}
}

$conf .= "$extraConfig\n";


# Generate the menu entries.
my $curEntry = 0;
$conf .= "\n";

my %copied;
mkpath("/boot/kernels", 0, 0755) if $copyKernels;

sub copyToKernelsDir {
my ($path) = @_;
return $path unless $copyKernels;
$path =~ /\/nix\/store\/(.*)/ or die;
my $name = $1; $name =~ s/\//-/g;
my $dst = "/boot/kernels/$name";
# Don't copy the file if $dst already exists. This means that we
# have to create $dst atomically to prevent partially copied
# kernels or initrd if this script is ever interrupted.
if (! -e $dst) {
my $tmp = "$dst.tmp";
copy $path, $tmp or die "cannot copy $path to $tmp\n";
rename $tmp, $dst or die "cannot rename $tmp to $dst\n";
}
$copied{$dst} = 1;
return "$bootRoot/kernels/$name";
}

sub addEntry {
my ($name, $path) = @_;
return if $curEntry++ > $configurationLimit;
return unless -e "$path/kernel" && -e "$path/initrd";

my $kernel = copyToKernelsDir(Cwd::abs_path("$path/kernel"));
my $initrd = copyToKernelsDir(Cwd::abs_path("$path/initrd"));
my $xen = -e "$path/xen.gz" ? copyToKernelsDir(Cwd::abs_path("$path/xen")) : undef;

# FIXME: $confName

my $kernelParams =
"systemConfig=" . Cwd::abs_path($path) . " " .
"init=" . Cwd::abs_path("$path/init") . " " .
join " ", IO::File->new("$path/kernel-params")->getlines;
my $xenParams = $xen && -e "$path/xen-params" ? join " ", IO::File->new("$path/xen-params")->getlines : "";

if ($grubVersion == 1) {
$conf .= "title $name\n";
$conf .= " $extraPerEntryConfig\n" if $extraPerEntryConfig;
$conf .= " kernel $xen $xenParams\n" if $xen;
$conf .= " " . ($xen ? "module" : "kernel") . " $kernel $kernelParams\n";
$conf .= " " . ($xen ? "module" : "initrd") . " $initrd\n\n";
} else {
$conf .= "menuentry \"$name\" {\n";
$conf .= " $extraPerEntryConfig\n" if $extraPerEntryConfig;
$conf .= " multiboot $xen $xenParams\n" if $xen;
$conf .= " " . ($xen ? "module" : "linux") . " $kernel $kernelParams\n";
$conf .= " " . ($xen ? "module" : "initrd") . " $initrd\n";
$conf .= "}\n\n";
}
}


# Add default entries.
$conf .= "$extraEntries\n" if $extraEntriesBeforeNixOS;

addEntry("NixOS - Default", $defaultConfig);

$conf .= "$extraEntries\n" unless $extraEntriesBeforeNixOS;


# Add entries for all previous generations of the system profile.
$conf .= "submenu \"NixOS - Old configurations\" {\n" if $grubVersion == 2;

sub nrFromGen { my ($x) = @_; $x =~ /system-(.*)-link/; return $1; }

my @links = sort
{ nrFromGen($b) <=> nrFromGen($a) }
(glob "/nix/var/nix/profiles/system-*-link");

foreach my $link (@links) {
my $date = strftime("%F", localtime(lstat($link)->mtime));
my $version =
-e "$link/nixos-version"
? IO::File->new("$link/nixos-version")->getline
: basename((glob(dirname(Cwd::abs_path("$link/kernel")) . "/lib/modules/*"))[0]);
addEntry("NixOS - Configuration " . nrFromGen($link) . " ($date - $version)", $link);
}

$conf .= "}\n" if $grubVersion == 2;


# Atomically update the GRUB config.
my $confFile = $grubVersion == 1 ? "/boot/grub/menu.lst" : "/boot/grub/grub.cfg";
my $tmpFile = $confFile . ".tmp";
open CONF, ">$tmpFile" or die "cannot open $tmpFile for writing\n";
print CONF $conf or die;
close CONF;
rename $tmpFile, $confFile or die "cannot rename $tmpFile to $confFile\n";


# Remove obsolete files from /boot/kernels.
foreach my $fn (glob "/boot/kernels/*") {
next if defined $copied{$fn};
print STDERR "removing obsolete file $fn\n";
unlink $fn;
}

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