#!/usr/bin/perl

# Copyright (C) 2007-2021 Oracle and/or its affiliates. All rights reserved.
# Authors: Jeff Arnold, Anders Kaseorg, Tim Abbott
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License, version 2.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA
# 02110-1301, USA.
# Not a Contribution for purposes of the Fedora Project Individual Contributor
# License Agreement

use strict;
use warnings;
use lib '/usr/lib/uptrack';
use Ksplice;
my $have_usleep = eval { require Time::HiRes };

my $debug;
my $debugon = 0;
GetOptions(@common_options,
	"debug" => \$debugon,
	"debugfile=s" => \$debug) or pod2usage(1);

pod2usage(1) if($help || scalar(@ARGV) != 1);
$debugon = 1 if (defined($debug));
$debug = abs_path($debug) if (defined $debug);

my $kid = $ARGV[0];
$kid =~ s/^ksplice[-_]//;
$kid =~ s/[-_].*$//;
my $update = "ksplice_$kid";
my $nounload = runstr("cat /proc/modules") =~ m/- $/m;

chdir("/sys/module");

if (-e "/sys/module/acfs_$update") {
    $update = "acfs_ksplice_$kid";
}

if (!update_loaded($kid)
    && !-e $update && !defined(glob("${update}_*_{o,n,old,new}"))) {
	print "Ksplice id $kid is not present in the kernel\n";
	rmtree("/var/run/ksplice/updates/$kid") if (-e "/var/run/ksplice/updates/$kid");
	exit(1);
}

set_debug_level($kid, $debugon);
my $failed = 0;

foreach my $module (glob("${update}_*_{o,old}")) {
	if (!$nounload && runval_raw('rmmod', $module) != 0) {
		child_error();
		error_die();
	}
}

my $partial = get_partial($kid);
if ($partial && !$nounload) {
	foreach my $module (glob("${update}_*_{n,new}")) {
		if (refcount($module) == 0 && runval_raw('rmmod', $module) != 0) {
			child_error();
			error_die();
		}
	}
}

my $have_sysfs = update_loaded($kid);
my $stage = ($have_sysfs && get_stage($kid));
if ($stage ne 'applied') {
	print "Ksplice id $kid is not applied; just cleaning up\n";
}
else {
	set_stage($kid, "reversed");
}
$stage = ($have_sysfs && get_stage($kid));
($stage eq 'reversed') or !$have_sysfs or error_die();

foreach my $module (glob("${update}_*_{n,new}")) {
	if (!$nounload && runval_raw('rmmod', $module) != 0) {
		child_error();
		error_die();
	}
}

set_stage($kid, "cleanup") if ($have_sysfs);
if ($have_usleep) {
	my $count = 0;
	while (update_loaded($kid) && $count < 5) {
		Time::HiRes::usleep(100000);
		$count++;
	}
} else {
	sleep(1) if (!update_loaded($kid));
}
if (-e "/sys/module/$update") {
	if (!$nounload && runval_raw('rmmod', $update) != 0) {
		child_error();
		error_die();
	}
}

rmtree("/var/run/ksplice/updates/$kid") if (-e "/var/run/ksplice/updates/$kid");

exit(0);

sub error_die {
	if (!update_loaded($kid)) {
		die("Error undoing Ksplice update $kid\n");
	}
	print STDERR "Error undoing Ksplice update $kid:\n" unless $raw_errors;
	print_error($kid);
	if($debugon) {
		get_debug_output($kid, $debug);
	}
	exit(-1);
}

sub print_error {
	my ($kid) = @_;
	my %errors = (
		"code_busy" => <<'END',
Ksplice has aborted the undo operation because it appears that the code that
you are trying to change is continuously in use by the system.  More
specifically, Ksplice has been unable to find a moment when one or more of the
to-be-changed functions is not on a thread's kernel stack.
END
		"module_busy" => <<'END',
Ksplice has aborted the undo operation because it appears that the Ksplice
update that you are trying to unload is in use by another module.  You can find
out what module is using the Ksplice update using the lsmod command.
END
		"unexpected_running_task" => <<'END',
Ksplice has aborted the undo operation because of an unexpected failure during
the kernel stack check.  Please consider reporting a bug to ksplice-support_ww@oracle.com.
END
		"out_of_memory" => <<'END',
Ksplice has aborted the undo operation because the kernel ran out of memory.
END
		"call_failed" => <<'END',
Ksplice has aborted the undo operation at the request of a one of the
pre-application hooks that were included as part of this Ksplice
update.  This is likely the result of a bug in the patch used to
generate this update.
END
		"cold_update_loaded" => <<'END',
Ksplice has aborted the undo operation because the update was applied using the
--partial option, and one of the modules that was changed by the update was loaded
since the update was applied.  You must first unload that (cold patched) module
before you can undo this update.
END
		"unexpected" => <<'END',
Ksplice has aborted because of an unexpected error.
Please consider reporting a bug to ksplice-support_ww@oracle.com.
END
		"UNKNOWN" => <<'END',
The Ksplice kernel component has returned an error code that this version of
ksplice-undo does not understand.
END
		"ok" => <<'END',
Ksplice has aborted the undo operation for unknown reasons.
Please consider reporting a bug to ksplice-support_ww@oracle.com.
END
);
	print_abort_error($kid, %errors);
}

=head1 NAME

ksplice-undo - Undo a Ksplice update that has been applied to the running kernel

=head1 SYNOPSIS

B<ksplice-undo> [I<OPTIONS>] I<KSPLICE_ID>

=head1 DESCRIPTION

B<ksplice-undo> takes as input a Ksplice identification tag, as reported by
L<ksplice-view(8)>, and it reverses that update within the running binary kernel.

=head1 OPTIONS

=over 8

=item B<--debug>

Reverses the update with debugging output enabled.  Recommended only for
debugging.

=item B<--debugfile=>I<filename>

Sets the location where debugging output should be saved.  Implies --debug.

=item B<--raw-errors>

Print only raw error information designed to be machine-readable on
standard error (standard output is still intended to be
human-readable).  If B<ksplice-undo> fails due to an error from the
Ksplice kernel modules, the first line on standard error will be a
Ksplice B<abort code> (see the Ksplice source code for documentation
on these codes).  Further lines will vary depending on the abort code.
If B<ksplice-undo> fails for any other reason, it will output the line
C<"OTHER\n">, followed by a human-readable failure message, to
standard error.

=back

=head1 SEE ALSO

L<ksplice-create(8)>, L<ksplice-apply(8)>, L<ksplice-view(8)>

=head1 BUGS

Please report bugs to <ksplice-support_ww@oracle.com>.

=head1 AUTHORS

Jeff Arnold, Anders Kaseorg, and Tim Abbott

=head1 COPYRIGHT

Copyright (C) 2007-2021 Oracle and/or its affiliates. All rights reserved.

This is free software and documentation.  You can redistribute and/or modify it
under the terms of the GNU General Public License, version 2.

=cut