ksplice-create.in

   1 #!/usr/bin/perl
   2
   3 # Copyright (C) 2008  Jeffrey Brian Arnold <jbarnold@mit.edu>
   4 #
   5 # This program is free software; you can redistribute it and/or modify
   6 # it under the terms of the GNU General Public License, version 2.
   7 #
   8 # This program is distributed in the hope that it will be useful,
   9 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  10 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11 # GNU General Public License for more details.
  12 #
  13 # You should have received a copy of the GNU General Public License
  14 # along with this program; if not, write to the Free Software
  15 # Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA
  16 # 02110-1301, USA.
  17
  18 use Getopt::Long;
  19 use Cwd 'abs_path', 'getcwd';
  20 use Pod::Usage;
  21 use strict;
  22 use warnings;
  23 use lib 'KSPLICE_DATA_DIR';
  24 use ksplice;
  25
  26 my ($patchfile, $diffext, $orig_config_dir, $postdir, $jobs);
  27 my ($help, $wantversion, $prebuild, $skip_prebuild, $apply, $patch_opt) = (0, 0, 0, 0, 0, "-p1");
  28 Getopt::Long::Configure("bundling");
  29 GetOptions("help|?" => \$help,
  30         "version" => \$wantversion,
  31         "verbose|v!" => \$verbose,
  32         "patch=s" => \$patchfile,
  33         "diffext=s" => \$diffext,
  34         "prebuild" => \$prebuild,
  35         "skip-prebuild" => \$skip_prebuild,
  36         "jobs|j:i" => \$jobs,
  37         "config=s" => \$orig_config_dir,
  38         "apply" => \$apply,
  39         "postdir=s" => \$postdir,
  40         "patch-opt=s@" => \$patch_opt) or pod2usage(1);
  41
  42 if($wantversion) {
  43         print $version_str;
  44         exit(0);
  45 }
  46 pod2usage(1) if($help || scalar(@ARGV) != 1);
  47 my $actions = (defined $patchfile) + (defined $diffext) + ($prebuild);
  48 pod2usage(1) if($actions != 1);
  49
  50 my ($linuxtree) = (abs_path($ARGV[0]));
  51
  52 my $tmpdir = init_tmpdir();
  53 runval("cp", "--", $patchfile, "$tmpdir/patch") if(defined $patchfile);
  54 $patchfile = "$tmpdir/patch";
  55
  56 $patch_opt = "-p0" if(defined $diffext);
  57 $patch_opt = join(" ", @$patch_opt) if(ref $patch_opt);
  58
  59 if(!defined $orig_config_dir) {
  60         $orig_config_dir = "$linuxtree/ksplice";
  61 }
  62 else {
  63         $orig_config_dir = abs_path($orig_config_dir);
  64         if($orig_config_dir =~ $linuxtree) {
  65                 die "Aborting: User-specified ORIG_CONFIG cannot be KERNEL_SOURCE or a subdirectory";
  66         }
  67 }
  68 if(!defined $orig_config_dir || ! -d $orig_config_dir) {
  69         die "Failed to find ORIG_CONFIG directory ($orig_config_dir)";
  70 }
  71 if(! -e "$orig_config_dir/.config") {
  72         die "Failed to find .config file in ORIG_CONFIG directory";
  73 }
  74 if(! -e "$orig_config_dir/System.map") {
  75         die "Failed to find System.map file in ORIG_CONFIG directory";
  76 }
  77
  78 if(!defined $postdir) {
  79         $postdir = "$orig_config_dir/post";
  80 }
  81 elsif($postdir =~ $linuxtree) {
  82         die "Aborting: User-specified postdir cannot be KERNEL_SOURCE or a subdirectory";
  83 }
  84
  85 runval("cp", "--", "$orig_config_dir/.config", $linuxtree);
  86
  87 my @chars = ('a'..'z', 0..9);
  88 my $kid = "";
  89 for(my $z = 0; $z < 8; $z++) {
  90         $kid .= $chars[int(rand(36))];
  91 }
  92 my $ksplice = "ksplice-$kid";
  93
  94 my %syms;
  95 load_system_map();
  96
  97 # Some versions of Fedora have System.map files whose symbol addresses disagree
  98 # with the running kernel by a constant address offset.  Here, Ksplice notes the
  99 # System.map address for printk so that it can later compare this address against
 100 # the kernel's address for printk.  This comparison helps Ksplice work around
 101 # this Fedora problem, and this comparison also helps Ksplice detect whether
 102 # the user has provided an incorrect System.map file.
 103 my $map_printk = (find_sym_system_map("printk"))[0];
 104
 105 my @rmsyms = qw(
 106         bust_spinlocks
 107         task_curr
 108         __kernel_text_address
 109         tasklist_lock
 110         stop_machine_run
 111         init_mm
 112         kallsyms_addresses
 113         kallsyms_num_syms
 114         kallsyms_names
 115         kallsyms_token_table
 116         kallsyms_token_index
 117 );
 118
 119 print "Starting kernel builds (this process might take a long time)...\n";
 120 if(!$verbose) {
 121         print "For output during this process, run ksplice-create with the option -v\n";
 122 }
 123
 124 ###################################################################
 125 # PHASE 1: Determine which object files are modified by the patch #
 126 # - performs the pre and post kernel builds                       #
 127 # - uses objdiff to identify which ELF sections have changed and  #
 128 #   which ELF symbols are entry points to those sections          #
 129 ###################################################################
 130
 131 # We will refer to the object files modified by the patch as the "target object
 132 # files", the ELF sections changed by the patch as the "target sections", and
 133 # the entry points of those sections as the "target entry points".
 134
 135 my $origdir = getcwd();
 136 runcd($linuxtree);
 137 if(defined $diffext) {
 138         runval("$libexecdir/ksplice-gendiff-reversed >$patchfile . $diffext");
 139 }
 140
 141 my @jlevel = (defined $ENV{CONCURRENCY_LEVEL} ? ("-j$ENV{CONCURRENCY_LEVEL}") : ());
 142 @jlevel = ("-j$jobs") if(defined $jobs);
 143 my @make_ksplice = ("make", "-f", "$datadir/Makefile.ksplice", @jlevel);
 144
 145 sub revert_orig() {
 146         for (split(/\0/, runstr(qw(find -name *.KSPLICE_pre -print0)))) {
 147                 s/\.KSPLICE_pre$//;
 148                 rename("$_.KSPLICE_pre", $_);
 149                 unlink("$_.KSPLICE") if(-e "$_.KSPLICE");
 150         }
 151 }
 152 revert_orig();
 153
 154 if(!$skip_prebuild &&
 155    runval_raw(@make_ksplice, "KSPLICE_MODE=snap") != 0) {
 156         die "Aborting: Prebuild failed";
 157 }
 158 exit(0) if($prebuild);
 159 runval("patch $patch_opt -bz .KSPLICE_pre < $patchfile");
 160 if(runval_raw(@make_ksplice, "KSPLICE_MODE=diff") != 0) {
 161         revert_orig();
 162         die "Aborting: Applying the patch appears to break the kernel build";
 163 }
 164
 165 runval("mkdir", "-p", "--", "$tmpdir/collect");
 166
 167 my @modules = ();
 168 foreach(glob(".tmp_versions/*.mod.KSPLICE")) {
 169         open MOD, '<', $_;
 170         chomp(my $module = <MOD>);
 171         close MOD;
 172         runval("cp", "$module.o.KSPLICE", "$tmpdir/collect/");
 173         runval("cp", "$module.o.KSPLICE_primary", "$tmpdir/collect/");
 174         runval("cp", "$module.o.KSPLICE_helper", "$tmpdir/collect/");
 175         $module =~ s/^.*\///;
 176         push @modules, $module;
 177 }
 178
 179 if(!@modules) {
 180         revert_orig();
 181         die "Aborting: No changes detected";
 182 }
 183
 184 revert_orig();
 185
 186 my $word;
 187 for my $module (@modules) {
 188         runcd("$tmpdir/collect");
 189         open IN, '<', "$module.o.KSPLICE";
 190         chomp(my $bits = <IN>);
 191         die if($bits != 32 && $bits != 64);
 192         $word = ($bits == 64 ? "quad" : "long");
 193
 194         my ($patchlist, $relocs_primary, $relocs_helper) = ('', '', '');
 195         $patchlist .= $_ while (($_ = <IN>) ne "\n");
 196         $relocs_primary .= $_ while (($_ = <IN>) ne "\n");
 197         $relocs_helper .= $_ while (($_ = <IN>) ne "\n");
 198
 199         close IN;
 200
 201 ################################################################################
 202 # PHASE 3: Combine the target object files and prepare for kernel module build #
 203 # - links the many target object files into two "collection" object files      #
 204 # - saves the reloc info extracted earlier in ELF sect .ksplice.ksplice_relocs #
 205 # - uses objmanip's sizelist mode to save the names and sizes of target funcs  #
 206 # - uses ld-script to aggregate all ELF text sections into .text               #
 207 # - saves the list of target entry syms in ELF sect .ksplice.ksplice_patches   #
 208 ################################################################################
 209
 210         parse_and_save(\&parse_relocs, $relocs_primary, "$module.o.KSPLICE_primary",
 211                        "ksplice_relocs", "_global");
 212         parse_and_save(\&parse_relocs, $relocs_helper, "$module.o.KSPLICE_helper",
 213                        "ksplice_relocs", "_global");
 214
 215         runcd($tmpdir);
 216         runval("cp", "-a", "--", "$datadir/kmodsrc", "kmodsrc-$module");
 217         runval("mv", "collect/$module.o.KSPLICE_primary", "kmodsrc-$module/collection.o.primary");
 218         runval("mv", "collect/$module.o.KSPLICE_helper", "kmodsrc-$module/collection.o.helper");
 219         runcd("kmodsrc-$module");
 220
 221         my $sizelist_primary = runsuc("objmanip", "collection.o.primary", "sizelist");
 222         parse_and_save(\&parse_sizelist, $sizelist_primary, "collection.o.primary", "ksplice_sizes");
 223         my $sizelist_helper = runsuc("objmanip", "collection.o.helper", "sizelist");
 224         parse_and_save(\&parse_sizelist, $sizelist_helper, "collection.o.helper", "ksplice_sizes");
 225
 226         runval("ld", "--script=ld-script", "-r", "-o", "collection.o.primary.postld", "collection.o.primary");
 227         runval("cp", "collection.o.primary.postld", "collection.o.primary");
 228         runval("ld", "--script=ld-script", "-r", "-o", "collection.o.helper.postld", "collection.o.helper");
 229         runval("cp", "collection.o.helper.postld", "collection.o.helper");
 230
 231         parse_and_save(\&parse_patchlist, $patchlist, "collection.o.primary", "ksplice_patches");
 232
 233 ###############################################################################
 234 # PHASE 4: Build the kernel modules and create the update tarball             #
 235 # - builds primary and helper kernel modules                                  #
 236 # - uses objmanip's rmsyms mode to remove relocations to non-exported symbols #
 237 # - creates a tarball of the primary module and the helper module             #
 238 ###############################################################################
 239
 240         my $kid_m = "${kid}_$module";
 241         $kid_m =~ s/-/_/g;
 242         my $ksplice_m = "ksplice-$kid_m";
 243         runval("make", "modules", "KSPLICE_ID=$kid_m", "map_printk=$map_printk", "KERNELSRC=$linuxtree");
 244
 245         my $relocs = runsuc("objmanip", "$ksplice_m.ko", "rmsyms", @rmsyms);
 246         parse_and_save(\&parse_relocs, $relocs, "$ksplice_m.ko", "ksplice_init_relocs", "");
 247 }
 248
 249 runcd($tmpdir);
 250 runval("mkdir", $ksplice);
 251 runval("mv", "--", $patchfile, $ksplice);
 252 for my $module (@modules) {
 253         my $kid_m = "${kid}_$module";
 254         $kid_m =~ s/-/_/g;
 255         my $ksplice_m = "ksplice-$kid_m";
 256         runval("mv", "--", "kmodsrc-$module/$ksplice_m.ko", "kmodsrc-$module/$ksplice_m-helper.ko", $ksplice);
 257 }
 258 runval("mkdir", "$ksplice/debug");
 259 runval("mv", "collect", "$ksplice/debug");
 260 for my $module (@modules) {
 261         runval("mv", "kmodsrc-$module", "$ksplice/debug");
 262 }
 263 runval("tar", "czf", "$ksplice.tar.gz", "--", $ksplice);
 264 runval("cp", "--", "$ksplice.tar.gz", $origdir);
 265 runcd($origdir);
 266 runval("rm", "-rf", "--", "$tmpdir");
 267
 268 print "Ksplice update tarball written to $ksplice.tar.gz\n";
 269
 270 if($apply) {
 271         print "Now running ksplice-apply to apply update...\n";
 272         exec("ksplice-apply", $ksplice) || die;
 273 }
 274
 275 exit(0);
 276
 277 sub load_system_map {
 278         open(SYMS, "<", "$orig_config_dir/System.map") or die;
 279         my $line;
 280         while(defined($line = <SYMS>)) {
 281                 my ($addr, $type, $sym, $mod) = split(/\s+/, $line);
 282                 next if($sym =~ /init_module/ ||
 283                         $sym =~ /cleanup_module/ ||
 284                         $sym =~ /this_module/);
 285
 286                 $syms{$sym}{$addr} = 1;
 287         }
 288         close(SYMS);
 289 }
 290
 291 sub find_sym_system_map {
 292         my ($sym) = @_;
 293         $sym =~ s/[.]text[.]//g;
 294         $sym =~ s/[.]bss[.]//g;
 295         $sym =~ s/[.]data[.]//g;
 296         $sym =~ s/____.*//g;
 297         if(defined $syms{$sym}) {
 298                 return keys(%{$syms{$sym}});
 299         }
 300         return ();
 301 }
 302
 303 sub parse_and_save {
 304         my ($funcref, $entries, $objfile, $suffix, @other) = @_;
 305         my @entries = split(/\n/, $entries);
 306
 307         my @tosave;
 308         foreach my $entry (@entries) {
 309                 print $entry, "\n" if($verbose);
 310                 &$funcref(\@tosave, $entry, @other);
 311         }
 312         save_using_asm(\@tosave, $objfile, $suffix);
 313 }
 314
 315 BEGIN { # to make asm_id a static local variable
 316 my ${asm_id} = "0";
 317 sub save_using_asm {
 318         my ($tosaveref, $objfile, $suffix) = @_;
 319
 320         open(ASM, ">", "asm${asm_id}.s");
 321         print ASM ".section .ksplice.${suffix}_str, \"a\"\n";
 322         print ASM "${suffix}_str:\n";
 323         print ASM ".section .ksplice.${suffix}, \"a\"\n";
 324         print ASM "${suffix}:\n";
 325
 326         my $num = 0;
 327         foreach my $entryref (@$tosaveref) {
 328                 my @entry = @{$entryref};
 329
 330                 if($entry[0] eq "str") {
 331                         print ASM ".section .ksplice.${suffix}_str, \"a\"\n";
 332                         print ASM $suffix, $num, ": .string \"", $entry[1], "\"\n";
 333                         print ASM ".section .ksplice.${suffix}, \"a\"\n";
 334                         print ASM ".$word ${suffix}", $num++, "\n";
 335                 }
 336                 elsif($entry[0] eq "array" && scalar(@entry) == 1) {
 337                         print ASM ".section .ksplice.${suffix}, \"a\"\n";
 338                         print ASM ".$word 0x0\n";
 339                 }
 340                 elsif($entry[0] eq "array") {
 341                         print ASM ".section .ksplice.${suffix}_array, \"a\"\n";
 342                         print ASM $suffix, $num, ":\n";
 343                         for(my $i = 1; $i < scalar(@entry); $i++) {
 344                                 print ASM ".$word 0x", $entry[$i], "\n";
 345                         }
 346                         print ASM ".section .ksplice.${suffix}, \"a\"\n";
 347                         print ASM ".$word ${suffix}", $num++, "\n";
 348                 }
 349                 elsif($entry[0] eq "word") {
 350                         print ASM ".section .ksplice.${suffix}, \"a\"\n";
 351                         print ASM ".$word 0x", $entry[1], "\n";
 352                 }
 353                 elsif($entry[0] eq "ptr") {
 354                         print ASM ".section .ksplice.${suffix}, \"a\"\n";
 355                         print ASM ".$word ", $entry[1], "\n";
 356                 }
 357                 else { die; }
 358         }
 359         print ASM ".section .ksplice.${suffix}, \"a\"\n";
 360         print ASM ".$word 0\n";
 361         print ASM ".globl ${suffix}\n";
 362         close(ASM);
 363
 364         runval("gcc", "-mcmodel=kernel", "-c", "asm${asm_id}.s", "-o", "asm${asm_id}.o");
 365         runval("ld", "-r", "-o", "$objfile.new", $objfile, "asm${asm_id}.o");
 366         runval("mv", "$objfile.new", $objfile);
 367         ${asm_id}++;
 368 }
 369 } # close BEGIN
 370
 371 sub parse_relocs {
 372         my ($tosaveref, $entry, $globalizer) = @_;
 373         my ($sym, $sect, $addr, $pcrel, $addend, $size) = split(/\s/, $entry);
 374
 375         my ($func) = ($sect =~ /(.*)____/);
 376         $sym =~ s/([.]data[.]__func__[.])\d+/$1${func}/g;
 377
 378         my @symvals = find_sym_system_map($sym);
 379         my @sectvals = find_sym_system_map($sect);
 380
 381         push @$tosaveref, (["str", $sym], ["str", $sect],
 382                         ["ptr", "${sect}${globalizer}"],
 383                         ["word", $addr],
 384                         ["word", scalar(@symvals)],
 385                         ["array", @symvals],
 386                         ["word", scalar(@sectvals)],
 387                         ["array", @sectvals],
 388                         ["word", $pcrel],
 389                         ["word", $addend],
 390                         ["word", $size]);
 391 }
 392
 393 sub parse_sizelist {
 394         my ($tosaveref, $entry) = @_;
 395         # grab the size and the symbol name from the end of the line
 396         my ($size, $sym) = ($entry =~ /\s([a-z0-9]+)\s+(\S+)$/);
 397
 398         my @vals = find_sym_system_map($sym);
 399
 400         push @$tosaveref, (["str", $sym], ["word", $size],
 401                 ["ptr", "${sym}_global"], ["word", scalar(@vals)],
 402                 ["array", @vals]);
 403 }
 404
 405 sub parse_patchlist {
 406         my ($tosaveref, $entry) = @_;
 407         my ($oldsym, $replsym) = split(/\s/, $entry);
 408
 409         my $oldaddr = 0;
 410         my @vals = find_sym_system_map($oldsym);
 411         $oldaddr = $vals[0] if(scalar(@vals) == 1);
 412
 413         push @$tosaveref, (["str", $oldsym], ["str", $replsym],
 414                 ["word", $oldaddr], ["ptr", "${replsym}_global"],
 415                 ["word", 0]);
 416 }
 417
 418 =head1 NAME
 419
 420 ksplice-create - Create a set of kernel modules for a rebootless kernel update
 421
 422 =head1 SYNOPSIS
 423
 424 B<ksplice-create> [B<--config=>I<ORIG_CONFIG>] B<--patch=>I<PATCH_FILE> I<KERNEL_SOURCE>
 425
 426 B<ksplice-create> [B<--config=>I<ORIG_CONFIG>] B<--diffext=>I<EXTENSION> I<KERNEL_SOURCE>
 427
 428 B<ksplice-create> [B<--config=>I<ORIG_CONFIG>] B<--prebuild> I<KERNEL_SOURCE>
 429
 430 =head1 DESCRIPTION
 431
 432 B<ksplice-create> creates a set of Ksplice kernel modules that, when loaded,
 433 will apply a user-specified source code patch to the running binary kernel.
 434
 435 Before you use B<ksplice-create> on a patch, you should confirm that the
 436 desired source code change does not make any semantic changes to kernel data
 437 structures--that is, changes that would require existing instances of kernel
 438 data structures to be transformed (e.g., a patch that adds a field to a global
 439 data structure would require the existing data structures to change).  If you
 440 use Ksplice on a patch that changes data structure semantics, Ksplice will not
 441 detect the problem and you could experience kernel problems as a result.
 442
 443 The to-be-applied source code patch can be specified by providing a L<patch(1)>
 444 file (B<--patch=>I<PATCH_FILE>) or by providing a file extension
 445 (B<--diffext=>I<EXTENSION>).
 446
 447 If a file extension is specified, then the desired source code patch will be
 448 determined by comparing all of the files in the I<KERNEL_SOURCE> directory tree
 449 whose names end with the extra extension I<EXTENSION> against the corresponding
 450 files without the extra extension.  Only the new files containing the extra
 451 extension in their filenames should be modified.
 452
 453 Here is an example of using a file extension to specify a patch:
 454
 455  $ cp KERNEL_SOURCE/kernel/sys.c KERNEL_SOURCE/kernel/sys.c.prctl_fixed
 456  [edit sys.c.prctl_fixed to include the desired changes]
 457  $ ksplice-create --diffext=.prctl_fixed KERNEL_SOURCE
 458
 459 KERNEL_SOURCE must be a directory containing the to-be-updated kernel's
 460 original source code.  If your Linux distribution applies patches to the Linux
 461 kernel during the kernel build process, then those patches must be applied to
 462 the I<KERNEL_SOURCE> directory before invoking B<ksplice-create> on that
 463 directory.  B<ksplice-create> will not modify the source code in the
 464 I<KERNEL_SOURCE> directory tree, but it will perform a kernel build in that
 465 directory tree.
 466
 467 I<ORIG_CONFIG> can be used to specify the directory containing the
 468 to-be-updated kernel's original F<.config> file and original F<System.map> file
 469 (the files should have exactly those names).  I<ORIG_CONFIG> defaults to
 470 I<KERNEL_SOURCE>B</ksplice>.
 471
 472 The default L<gcc(1)> compiler and L<as(1)> assembler on the system should be as
 473 close to the compiler and assembler originally used to build the running kernel
 474 as possible.  If the current compiler and linker are too different from the
 475 original compiler and linker, B<ksplice-apply> will abort when applying the
 476 update.
 477
 478 B<ksplice-create> outputs a L<tar(1)> file, compressed with L<gzip(1)>,
 479 containing the desired Ksplice update modules.  This tarball will be created in
 480 the current directory, and it can be manipulated using the other Ksplice
 481 utilities, such as B<ksplice-apply>.
 482
 483 The first time that B<ksplice-create> is invoked on a I<KERNEL_SOURCE>
 484 directory, it must build that kernel from scratch, which is much slower than
 485 the rest of the update-creation process.  B<--prebuild> can be used to perform
 486 this initial kernel build (and set up a tentative B<post> directory tree)
 487 without providing a source code patch.
 488
 489 In order to patch a function that has previously been patched by Ksplice, the
 490 user needs to ensure that the I<KERNEL_SOURCE> directory provided to Ksplice
 491 contains the source for the currently running kernel, including any patches
 492 that have previously been applied by Ksplice.
 493
 494 =head1 OPTIONS
 495
 496 =over 8
 497
 498 =item B<-v>, B<--verbose>
 499
 500 Prints the commands being executed, the output of the commands being executed,
 501 and various other pieces of information.
 502
 503 =item B<-j> I<JOBS>, B<--jobs=>I<JOBS>
 504
 505 Specifies the number of jobs to run simultaneously while performing kernel
 506 builds.  B<ksplice-create> also honors the environment variable
 507 CONCURRENCY_LEVEL.
 508
 509 =item B<--apply>
 510
 511 Immediately applies the generated update to the running kernel by invoking
 512 B<ksplice-apply>.
 513
 514 =item B<--postdir=>I<DIRECTORY>
 515
 516 Specifies a directory that is B<dedicated to Ksplice> to be used as the Ksplice
 517 I<post> directory.  Defaults to I<ORIG_CONFIG>B</post>.  If this directory
 518 exists, the directory's contents will be removed.  If it does not exist, it
 519 will be created.
 520
 521 =item B<--patch-opt=>I<OPTIONS>
 522
 523 Can be used to pass options to L<patch(1)>.  If this option is NOT specified, then
 524 B<-p1> is passed to B<patch>.  If this option is specified, then only the
 525 specified options will be passed to B<patch>.  This option can be repeated in
 526 order to pass multiple options to B<patch>.  This option is ignored when the
 527 to-be-applied source code patch is specified using B<--diffext>.
 528
 529 =back
 530
 531 =head1 BUGS
 532
 533 In this Ksplice version, Ksplice kernel modules do not enforce dependencies.
 534 For example, if you patch a Linux kernel module using Ksplice, you are
 535 responsible for ensuring that you do not remove that module from the kernel
 536 until after you have reversed the Ksplice update.  (If you try to reverse a
 537 Ksplice update after you have already removed the relevant module from the
 538 kernel, this version of Ksplice will write to memory addresses that are no
 539 longer occupied by that module).
 540
 541 Please report bugs to <PACKAGE_BUGREPORT>.
 542
 543 =head1 SEE ALSO
 544
 545 L<ksplice-apply(8)>, L<ksplice-view(8)>, L<ksplice-undo(8)>
 546
 547 =head1 COPYRIGHT
 548
 549 Copyright (C) 2008  Jeffrey Brian Arnold <jbarnold@mit.edu>.
 550
 551 This is free software and documentation.  You can redistribute and/or modify it
 552 under the terms of the GNU General Public License, version 2.
 553
 554 =cut