scripts/recordmcount.pl

   1 #!/usr/bin/perl -w
   2 # (c) 2008, Steven Rostedt <srostedt@redhat.com>
   3 # Licensed under the terms of the GNU GPL License version 2
   4 #
   5 # recordmcount.pl - makes a section called __mcount_loc that holds
   6 #                   all the offsets to the calls to mcount.
   7 #
   8 #
   9 # What we want to end up with this is that each object file will have a
  10 # section called __mcount_loc that will hold the list of pointers to mcount
  11 # callers. After final linking, the vmlinux will have within .init.data the
  12 # list of all callers to mcount between __start_mcount_loc and __stop_mcount_loc.
  13 # Later on boot up, the kernel will read this list, save the locations and turn
  14 # them into nops. When tracing or profiling is later enabled, these locations
  15 # will then be converted back to pointers to some function.
  16 #
  17 # This is no easy feat. This script is called just after the original
  18 # object is compiled and before it is linked.
  19 #
  20 # When parse this object file using 'objdump', the references to the call
  21 # sites are offsets from the section that the call site is in. Hence, all
  22 # functions in a section that has a call site to mcount, will have the
  23 # offset from the beginning of the section and not the beginning of the
  24 # function.
  25 #
  26 # But where this section will reside finally in vmlinx is undetermined at
  27 # this point. So we can't use this kind of offsets to record the final
  28 # address of this call site.
  29 #
  30 # The trick is to change the call offset referring the start of a section to
  31 # referring a function symbol in this section. During the link step, 'ld' will
  32 # compute the final address according to the information we record.
  33 #
  34 # e.g.
  35 #
  36 #  .section ".sched.text", "ax"
  37 #        [...]
  38 #  func1:
  39 #        [...]
  40 #        call mcount  (offset: 0x10)
  41 #        [...]
  42 #        ret
  43 #  .globl fun2
  44 #  func2:             (offset: 0x20)
  45 #        [...]
  46 #        [...]
  47 #        ret
  48 #  func3:
  49 #        [...]
  50 #        call mcount (offset: 0x30)
  51 #        [...]
  52 #
  53 # Both relocation offsets for the mcounts in the above example will be
  54 # offset from .sched.text. If we choose global symbol func2 as a reference and
  55 # make another file called tmp.s with the new offsets:
  56 #
  57 #  .section __mcount_loc
  58 #  .quad  func2 - 0x10
  59 #  .quad  func2 + 0x10
  60 #
  61 # We can then compile this tmp.s into tmp.o, and link it back to the original
  62 # object.
  63 #
  64 # In our algorithm, we will choose the first global function we meet in this
  65 # section as the reference. But this gets hard if there is no global functions
  66 # in this section. In such a case we have to select a local one. E.g. func1:
  67 #
  68 #  .section ".sched.text", "ax"
  69 #  func1:
  70 #        [...]
  71 #        call mcount  (offset: 0x10)
  72 #        [...]
  73 #        ret
  74 #  func2:
  75 #        [...]
  76 #        call mcount (offset: 0x20)
  77 #        [...]
  78 #  .section "other.section"
  79 #
  80 # If we make the tmp.s the same as above, when we link together with
  81 # the original object, we will end up with two symbols for func1:
  82 # one local, one global.  After final compile, we will end up with
  83 # an undefined reference to func1 or a wrong reference to another global
  84 # func1 in other files.
  85 #
  86 # Since local objects can reference local variables, we need to find
  87 # a way to make tmp.o reference the local objects of the original object
  88 # file after it is linked together. To do this, we convert func1
  89 # into a global symbol before linking tmp.o. Then after we link tmp.o
  90 # we will only have a single symbol for func1 that is global.
  91 # We can convert func1 back into a local symbol and we are done.
  92 #
  93 # Here are the steps we take:
  94 #
  95 # 1) Record all the local and weak symbols by using 'nm'
  96 # 2) Use objdump to find all the call site offsets and sections for
  97 #    mcount.
  98 # 3) Compile the list into its own object.
  99 # 4) Do we have to deal with local functions? If not, go to step 8.
 100 # 5) Make an object that converts these local functions to global symbols
 101 #    with objcopy.
 102 # 6) Link together this new object with the list object.
 103 # 7) Convert the local functions back to local symbols and rename
 104 #    the result as the original object.
 105 # 8) Link the object with the list object.
 106 # 9) Move the result back to the original object.
 107 #
 108
 109 use strict;
 110
 111 my $P = $0;
 112 $P =~ s@.*/@@g;
 113
 114 my $V = '0.1';
 115
 116 if ($#ARGV != 11) {
 117         print "usage: $P arch endian bits objdump objcopy cc ld nm rm mv is_module inputfile\n";
 118         print "version: $V\n";
 119         exit(1);
 120 }
 121
 122 my ($arch, $endian, $bits, $objdump, $objcopy, $cc,
 123     $ld, $nm, $rm, $mv, $is_module, $inputfile) = @ARGV;
 124
 125 # This file refers to mcount and shouldn't be ftraced, so lets' ignore it
 126 if ($inputfile =~ m,kernel/trace/ftrace\.o$,) {
 127     exit(0);
 128 }
 129
 130 # Acceptable sections to record.
 131 my %text_sections = (
 132      ".text" => 1,
 133      ".init.text" => 1,
 134      ".ref.text" => 1,
 135      ".sched.text" => 1,
 136      ".spinlock.text" => 1,
 137      ".irqentry.text" => 1,
 138      ".softirqentry.text" => 1,
 139      ".kprobes.text" => 1,
 140      ".cpuidle.text" => 1,
 141      ".text.unlikely" => 1,
 142 );
 143
 144 # Note: we are nice to C-programmers here, thus we skip the '||='-idiom.
 145 $objdump = 'objdump' if (!$objdump);
 146 $objcopy = 'objcopy' if (!$objcopy);
 147 $cc = 'gcc' if (!$cc);
 148 $ld = 'ld' if (!$ld);
 149 $nm = 'nm' if (!$nm);
 150 $rm = 'rm' if (!$rm);
 151 $mv = 'mv' if (!$mv);
 152
 153 #print STDERR "running: $P '$arch' '$objdump' '$objcopy' '$cc' '$ld' " .
 154 #    "'$nm' '$rm' '$mv' '$inputfile'\n";
 155
 156 my %locals;             # List of local (static) functions
 157 my %weak;               # List of weak functions
 158 my %convert;            # List of local functions used that needs conversion
 159
 160 my $type;
 161 my $local_regex;        # Match a local function (return function)
 162 my $weak_regex;         # Match a weak function (return function)
 163 my $section_regex;      # Find the start of a section
 164 my $function_regex;     # Find the name of a function
 165                         #    (return offset and func name)
 166 my $mcount_regex;       # Find the call site to mcount (return offset)
 167 my $mcount_adjust;      # Address adjustment to mcount offset
 168 my $alignment;          # The .align value to use for $mcount_section
 169 my $section_type;       # Section header plus possible alignment command
 170 my $can_use_local = 0;  # If we can use local function references
 171
 172 # Shut up recordmcount if user has older objcopy
 173 my $quiet_recordmcount = ".tmp_quiet_recordmcount";
 174 my $print_warning = 1;
 175 $print_warning = 0 if ( -f $quiet_recordmcount);
 176
 177 ##
 178 # check_objcopy - whether objcopy supports --globalize-symbols
 179 #
 180 #  --globalize-symbols came out in 2.17, we must test the version
 181 #  of objcopy, and if it is less than 2.17, then we can not
 182 #  record local functions.
 183 sub check_objcopy
 184 {
 185     open (IN, "$objcopy --version |") or die "error running $objcopy";
 186     while (<IN>) {
 187         if (/objcopy.*\s(\d+)\.(\d+)/) {
 188             $can_use_local = 1 if ($1 > 2 || ($1 == 2 && $2 >= 17));
 189             last;
 190         }
 191     }
 192     close (IN);
 193
 194     if (!$can_use_local && $print_warning) {
 195         print STDERR "WARNING: could not find objcopy version or version " .
 196             "is less than 2.17.\n" .
 197             "\tLocal function references are disabled.\n";
 198         open (QUIET, ">$quiet_recordmcount");
 199         printf QUIET "Disables the warning from recordmcount.pl\n";
 200         close QUIET;
 201     }
 202 }
 203
 204 if ($arch =~ /(x86(_64)?)|(i386)/) {
 205     if ($bits == 64) {
 206         $arch = "x86_64";
 207     } else {
 208         $arch = "i386";
 209     }
 210 }
 211
 212 #
 213 # We base the defaults off of i386, the other archs may
 214 # feel free to change them in the below if statements.
 215 #
 216 $local_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\S+)";
 217 $weak_regex = "^[0-9a-fA-F]+\\s+([wW])\\s+(\\S+)";
 218 $section_regex = "Disassembly of section\\s+(\\S+):";
 219 $function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
 220 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s(mcount|__fentry__)\$";
 221 $section_type = '@progbits';
 222 $mcount_adjust = 0;
 223 $type = ".long";
 224
 225 if ($arch eq "x86_64") {
 226     $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s(mcount|__fentry__)([+-]0x[0-9a-zA-Z]+)?\$";
 227     $type = ".quad";
 228     $alignment = 8;
 229     $mcount_adjust = -1;
 230
 231     # force flags for this arch
 232     $ld .= " -m elf_x86_64";
 233     $objdump .= " -M x86-64";
 234     $objcopy .= " -O elf64-x86-64";
 235     $cc .= " -m64";
 236
 237 } elsif ($arch eq "i386") {
 238     $alignment = 4;
 239     $mcount_adjust = -1;
 240
 241     # force flags for this arch
 242     $ld .= " -m elf_i386";
 243     $objdump .= " -M i386";
 244     $objcopy .= " -O elf32-i386";
 245     $cc .= " -m32";
 246
 247 } elsif ($arch eq "s390" && $bits == 64) {
 248     if ($cc =~ /-DCC_USING_HOTPATCH/) {
 249         $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*c0 04 00 00 00 00\\s*brcl\\s*0,[0-9a-f]+ <([^\+]*)>\$";
 250         $mcount_adjust = 0;
 251     } else {
 252         $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_390_(PC|PLT)32DBL\\s+_mcount\\+0x2\$";
 253         $mcount_adjust = -14;
 254     }
 255     $alignment = 8;
 256     $type = ".quad";
 257     $ld .= " -m elf64_s390";
 258     $cc .= " -m64";
 259
 260 } elsif ($arch eq "sh") {
 261     $alignment = 2;
 262
 263     # force flags for this arch
 264     $ld .= " -m shlelf_linux";
 265     $objcopy .= " -O elf32-sh-linux";
 266
 267 } elsif ($arch eq "powerpc") {
 268     $local_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\.?\\S+)";
 269     # See comment in the sparc64 section for why we use '\w'.
 270     $function_regex = "^([0-9a-fA-F]+)\\s+<(\\.?\\w*?)>:";
 271     $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s\\.?_mcount\$";
 272
 273     if ($bits == 64) {
 274         $type = ".quad";
 275     }
 276
 277 } elsif ($arch eq "arm") {
 278     $alignment = 2;
 279     $section_type = '%progbits';
 280     $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_ARM_(CALL|PC24|THM_CALL)" .
 281                         "\\s+(__gnu_mcount_nc|mcount)\$";
 282
 283 } elsif ($arch eq "arm64") {
 284     $alignment = 3;
 285     $section_type = '%progbits';
 286     $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_AARCH64_CALL26\\s+_mcount\$";
 287     $type = ".quad";
 288 } elsif ($arch eq "ia64") {
 289     $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
 290     $type = "data8";
 291
 292     if ($is_module eq "0") {
 293         $cc .= " -mconstant-gp";
 294     }
 295 } elsif ($arch eq "sparc64") {
 296     # In the objdump output there are giblets like:
 297     # 0000000000000000 <igmp_net_exit-0x18>:
 298     # As there's some data blobs that get emitted into the
 299     # text section before the first instructions and the first
 300     # real symbols.  We don't want to match that, so to combat
 301     # this we use '\w' so we'll match just plain symbol names,
 302     # and not those that also include hex offsets inside of the
 303     # '<>' brackets.  Actually the generic function_regex setting
 304     # could safely use this too.
 305     $function_regex = "^([0-9a-fA-F]+)\\s+<(\\w*?)>:";
 306
 307     # Sparc64 calls '_mcount' instead of plain 'mcount'.
 308     $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
 309
 310     $alignment = 8;
 311     $type = ".xword";
 312     $ld .= " -m elf64_sparc";
 313     $cc .= " -m64";
 314     $objcopy .= " -O elf64-sparc";
 315 } elsif ($arch eq "mips") {
 316     # To enable module support, we need to enable the -mlong-calls option
 317     # of gcc for module, after using this option, we can not get the real
 318     # offset of the calling to _mcount, but the offset of the lui
 319     # instruction or the addiu one. herein, we record the address of the
 320     # first one, and then we can replace this instruction by a branch
 321     # instruction to jump over the profiling function to filter the
 322     # indicated functions, or switch back to the lui instruction to trace
 323     # them, which means dynamic tracing.
 324     #
 325     #       c:  3c030000        lui     v1,0x0
 326     #                   c: R_MIPS_HI16  _mcount
 327     #                   c: R_MIPS_NONE  *ABS*
 328     #                   c: R_MIPS_NONE  *ABS*
 329     #      10:  64630000        daddiu  v1,v1,0
 330     #                   10: R_MIPS_LO16 _mcount
 331     #                   10: R_MIPS_NONE *ABS*
 332     #                   10: R_MIPS_NONE *ABS*
 333     #      14:  03e0082d        move    at,ra
 334     #      18:  0060f809        jalr    v1
 335     #
 336     # for the kernel:
 337     #
 338     #     10:   03e0082d        move    at,ra
 339     #     14:   0c000000        jal     0 <loongson_halt>
 340     #                    14: R_MIPS_26   _mcount
 341     #                    14: R_MIPS_NONE *ABS*
 342     #                    14: R_MIPS_NONE *ABS*
 343     #    18:   00020021        nop
 344     if ($is_module eq "0") {
 345             $mcount_regex = "^\\s*([0-9a-fA-F]+): R_MIPS_26\\s+_mcount\$";
 346     } else {
 347             $mcount_regex = "^\\s*([0-9a-fA-F]+): R_MIPS_HI16\\s+_mcount\$";
 348     }
 349     $objdump .= " -Melf-trad".$endian."mips ";
 350
 351     if ($endian eq "big") {
 352             $endian = " -EB ";
 353             $ld .= " -melf".$bits."btsmip";
 354     } else {
 355             $endian = " -EL ";
 356             $ld .= " -melf".$bits."ltsmip";
 357     }
 358
 359     $cc .= " -mno-abicalls -fno-pic -mabi=" . $bits . $endian;
 360     $ld .= $endian;
 361
 362     if ($bits == 64) {
 363             $function_regex =
 364                 "^([0-9a-fA-F]+)\\s+<(.|[^\$]L.*?|\$[^L].*?|[^\$][^L].*?)>:";
 365             $type = ".dword";
 366     }
 367 } elsif ($arch eq "microblaze") {
 368     # Microblaze calls '_mcount' instead of plain 'mcount'.
 369     $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
 370 } elsif ($arch eq "blackfin") {
 371     $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s__mcount\$";
 372     $mcount_adjust = -4;
 373 } elsif ($arch eq "tilegx" || $arch eq "tile") {
 374     # Default to the newer TILE-Gx architecture if only "tile" is given.
 375     $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s__mcount\$";
 376     $type = ".quad";
 377     $alignment = 8;
 378 } else {
 379     die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD";
 380 }
 381
 382 my $text_found = 0;
 383 my $read_function = 0;
 384 my $opened = 0;
 385 my $mcount_section = "__mcount_loc";
 386
 387 my $dirname;
 388 my $filename;
 389 my $prefix;
 390 my $ext;
 391
 392 if ($inputfile =~ m,^(.*)/([^/]*)$,) {
 393     $dirname = $1;
 394     $filename = $2;
 395 } else {
 396     $dirname = ".";
 397     $filename = $inputfile;
 398 }
 399
 400 if ($filename =~ m,^(.*)(\.\S),) {
 401     $prefix = $1;
 402     $ext = $2;
 403 } else {
 404     $prefix = $filename;
 405     $ext = "";
 406 }
 407
 408 my $mcount_s = $dirname . "/.tmp_mc_" . $prefix . ".s";
 409 my $mcount_o = $dirname . "/.tmp_mc_" . $prefix . ".o";
 410
 411 check_objcopy();
 412
 413 #
 414 # Step 1: find all the local (static functions) and weak symbols.
 415 #         't' is local, 'w/W' is weak
 416 #
 417 open (IN, "$nm $inputfile|") || die "error running $nm";
 418 while (<IN>) {
 419     if (/$local_regex/) {
 420         $locals{$1} = 1;
 421     } elsif (/$weak_regex/) {
 422         $weak{$2} = $1;
 423     }
 424 }
 425 close(IN);
 426
 427 my @offsets;            # Array of offsets of mcount callers
 428 my $ref_func;           # reference function to use for offsets
 429 my $offset = 0;         # offset of ref_func to section beginning
 430
 431 ##
 432 # update_funcs - print out the current mcount callers
 433 #
 434 #  Go through the list of offsets to callers and write them to
 435 #  the output file in a format that can be read by an assembler.
 436 #
 437 sub update_funcs
 438 {
 439     return unless ($ref_func and @offsets);
 440
 441     # Sanity check on weak function. A weak function may be overwritten by
 442     # another function of the same name, making all these offsets incorrect.
 443     if (defined $weak{$ref_func}) {
 444         die "$inputfile: ERROR: referencing weak function" .
 445             " $ref_func for mcount\n";
 446     }
 447
 448     # is this function static? If so, note this fact.
 449     if (defined $locals{$ref_func}) {
 450
 451         # only use locals if objcopy supports globalize-symbols
 452         if (!$can_use_local) {
 453             return;
 454         }
 455         $convert{$ref_func} = 1;
 456     }
 457
 458     # Loop through all the mcount caller offsets and print a reference
 459     # to the caller based from the ref_func.
 460     if (!$opened) {
 461         open(FILE, ">$mcount_s") || die "can't create $mcount_s\n";
 462         $opened = 1;
 463         print FILE "\t.section $mcount_section,\"a\",$section_type\n";
 464         print FILE "\t.align $alignment\n" if (defined($alignment));
 465     }
 466     foreach my $cur_offset (@offsets) {
 467         printf FILE "\t%s %s + %d\n", $type, $ref_func, $cur_offset - $offset;
 468     }
 469 }
 470
 471 #
 472 # Step 2: find the sections and mcount call sites
 473 #
 474 open(IN, "$objdump -hdr $inputfile|") || die "error running $objdump";
 475
 476 my $text;
 477
 478
 479 # read headers first
 480 my $read_headers = 1;
 481
 482 while (<IN>) {
 483
 484     if ($read_headers && /$mcount_section/) {
 485         #
 486         # Somehow the make process can execute this script on an
 487         # object twice. If it does, we would duplicate the mcount
 488         # section and it will cause the function tracer self test
 489         # to fail. Check if the mcount section exists, and if it does,
 490         # warn and exit.
 491         #
 492         print STDERR "ERROR: $mcount_section already in $inputfile\n" .
 493             "\tThis may be an indication that your build is corrupted.\n" .
 494             "\tDelete $inputfile and try again. If the same object file\n" .
 495             "\tstill causes an issue, then disable CONFIG_DYNAMIC_FTRACE.\n";
 496         exit(-1);
 497     }
 498
 499     # is it a section?
 500     if (/$section_regex/) {
 501         $read_headers = 0;
 502
 503         # Only record text sections that we know are safe
 504         $read_function = defined($text_sections{$1});
 505         # print out any recorded offsets
 506         update_funcs();
 507
 508         # reset all markers and arrays
 509         $text_found = 0;
 510         undef($ref_func);
 511         undef(@offsets);
 512
 513     # section found, now is this a start of a function?
 514     } elsif ($read_function && /$function_regex/) {
 515         $text_found = 1;
 516         $text = $2;
 517
 518         # if this is either a local function or a weak function
 519         # keep looking for functions that are global that
 520         # we can use safely.
 521         if (!defined($locals{$text}) && !defined($weak{$text})) {
 522             $ref_func = $text;
 523             $read_function = 0;
 524             $offset = hex $1;
 525         } else {
 526             # if we already have a function, and this is weak, skip it
 527             if (!defined($ref_func) && !defined($weak{$text}) &&
 528                  # PPC64 can have symbols that start with .L and
 529                  # gcc considers these special. Don't use them!
 530                  $text !~ /^\.L/) {
 531                 $ref_func = $text;
 532                 $offset = hex $1;
 533             }
 534         }
 535     }
 536     # is this a call site to mcount? If so, record it to print later
 537     if ($text_found && /$mcount_regex/) {
 538         push(@offsets, (hex $1) + $mcount_adjust);
 539     }
 540 }
 541
 542 # dump out anymore offsets that may have been found
 543 update_funcs();
 544
 545 # If we did not find any mcount callers, we are done (do nothing).
 546 if (!$opened) {
 547     exit(0);
 548 }
 549
 550 close(FILE);
 551
 552 #
 553 # Step 3: Compile the file that holds the list of call sites to mcount.
 554 #
 555 `$cc -o $mcount_o -c $mcount_s`;
 556
 557 my @converts = keys %convert;
 558
 559 #
 560 # Step 4: Do we have sections that started with local functions?
 561 #
 562 if ($#converts >= 0) {
 563     my $globallist = "";
 564     my $locallist = "";
 565
 566     foreach my $con (@converts) {
 567         $globallist .= " --globalize-symbol $con";
 568         $locallist .= " --localize-symbol $con";
 569     }
 570
 571     my $globalobj = $dirname . "/.tmp_gl_" . $filename;
 572     my $globalmix = $dirname . "/.tmp_mx_" . $filename;
 573
 574     #
 575     # Step 5: set up each local function as a global
 576     #
 577     `$objcopy $globallist $inputfile $globalobj`;
 578
 579     #
 580     # Step 6: Link the global version to our list.
 581     #
 582     `$ld -r $globalobj $mcount_o -o $globalmix`;
 583
 584     #
 585     # Step 7: Convert the local functions back into local symbols
 586     #
 587     `$objcopy $locallist $globalmix $inputfile`;
 588
 589     # Remove the temp files
 590     `$rm $globalobj $globalmix`;
 591
 592 } else {
 593
 594     my $mix = $dirname . "/.tmp_mx_" . $filename;
 595
 596     #
 597     # Step 8: Link the object with our list of call sites object.
 598     #
 599     `$ld -r $inputfile $mcount_o -o $mix`;
 600
 601     #
 602     # Step 9: Move the result back to the original object.
 603     #
 604     `$mv $mix $inputfile`;
 605 }
 606
 607 # Clean up the temp files
 608 `$rm $mcount_o $mcount_s`;
 609
 610 exit(0);