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      ".sched.text" => 1,
 134      ".spinlock.text" => 1,
 135      ".irqentry.text" => 1,
 136      ".text.unlikely" => 1,
 137 );
 138
 139 $objdump = "objdump" if ((length $objdump) == 0);
 140 $objcopy = "objcopy" if ((length $objcopy) == 0);
 141 $cc = "gcc" if ((length $cc) == 0);
 142 $ld = "ld" if ((length $ld) == 0);
 143 $nm = "nm" if ((length $nm) == 0);
 144 $rm = "rm" if ((length $rm) == 0);
 145 $mv = "mv" if ((length $mv) == 0);
 146
 147 #print STDERR "running: $P '$arch' '$objdump' '$objcopy' '$cc' '$ld' " .
 148 #    "'$nm' '$rm' '$mv' '$inputfile'\n";
 149
 150 my %locals;             # List of local (static) functions
 151 my %weak;               # List of weak functions
 152 my %convert;            # List of local functions used that needs conversion
 153
 154 my $type;
 155 my $local_regex;        # Match a local function (return function)
 156 my $weak_regex;         # Match a weak function (return function)
 157 my $section_regex;      # Find the start of a section
 158 my $function_regex;     # Find the name of a function
 159                         #    (return offset and func name)
 160 my $mcount_regex;       # Find the call site to mcount (return offset)
 161 my $alignment;          # The .align value to use for $mcount_section
 162 my $section_type;       # Section header plus possible alignment command
 163 my $can_use_local = 0;  # If we can use local function references
 164
 165 # Shut up recordmcount if user has older objcopy
 166 my $quiet_recordmcount = ".tmp_quiet_recordmcount";
 167 my $print_warning = 1;
 168 $print_warning = 0 if ( -f $quiet_recordmcount);
 169
 170 ##
 171 # check_objcopy - whether objcopy supports --globalize-symbols
 172 #
 173 #  --globalize-symbols came out in 2.17, we must test the version
 174 #  of objcopy, and if it is less than 2.17, then we can not
 175 #  record local functions.
 176 sub check_objcopy
 177 {
 178     open (IN, "$objcopy --version |") or die "error running $objcopy";
 179     while (<IN>) {
 180         if (/objcopy.*\s(\d+)\.(\d+)/) {
 181             $can_use_local = 1 if ($1 > 2 || ($1 == 2 && $2 >= 17));
 182             last;
 183         }
 184     }
 185     close (IN);
 186
 187     if (!$can_use_local && $print_warning) {
 188         print STDERR "WARNING: could not find objcopy version or version " .
 189             "is less than 2.17.\n" .
 190             "\tLocal function references are disabled.\n";
 191         open (QUIET, ">$quiet_recordmcount");
 192         printf QUIET "Disables the warning from recordmcount.pl\n";
 193         close QUIET;
 194     }
 195 }
 196
 197 if ($arch =~ /(x86(_64)?)|(i386)/) {
 198     if ($bits == 64) {
 199         $arch = "x86_64";
 200     } else {
 201         $arch = "i386";
 202     }
 203 }
 204
 205 #
 206 # We base the defaults off of i386, the other archs may
 207 # feel free to change them in the below if statements.
 208 #
 209 $local_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\S+)";
 210 $weak_regex = "^[0-9a-fA-F]+\\s+([wW])\\s+(\\S+)";
 211 $section_regex = "Disassembly of section\\s+(\\S+):";
 212 $function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
 213 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount\$";
 214 $section_type = '@progbits';
 215 $type = ".long";
 216
 217 if ($arch eq "x86_64") {
 218     $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount([+-]0x[0-9a-zA-Z]+)?\$";
 219     $type = ".quad";
 220     $alignment = 8;
 221
 222     # force flags for this arch
 223     $ld .= " -m elf_x86_64";
 224     $objdump .= " -M x86-64";
 225     $objcopy .= " -O elf64-x86-64";
 226     $cc .= " -m64";
 227
 228 } elsif ($arch eq "i386") {
 229     $alignment = 4;
 230
 231     # force flags for this arch
 232     $ld .= " -m elf_i386";
 233     $objdump .= " -M i386";
 234     $objcopy .= " -O elf32-i386";
 235     $cc .= " -m32";
 236
 237 } elsif ($arch eq "s390" && $bits == 32) {
 238     $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_390_32\\s+_mcount\$";
 239     $alignment = 4;
 240     $ld .= " -m elf_s390";
 241     $cc .= " -m31";
 242
 243 } elsif ($arch eq "s390" && $bits == 64) {
 244     $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_390_(PC|PLT)32DBL\\s+_mcount\\+0x2\$";
 245     $alignment = 8;
 246     $type = ".quad";
 247     $ld .= " -m elf64_s390";
 248     $cc .= " -m64";
 249
 250 } elsif ($arch eq "sh") {
 251     $alignment = 2;
 252
 253     # force flags for this arch
 254     $ld .= " -m shlelf_linux";
 255     $objcopy .= " -O elf32-sh-linux";
 256     $cc .= " -m32";
 257
 258 } elsif ($arch eq "powerpc") {
 259     $local_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\.?\\S+)";
 260     $function_regex = "^([0-9a-fA-F]+)\\s+<(\\.?.*?)>:";
 261     $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s\\.?_mcount\$";
 262
 263     if ($bits == 64) {
 264         $type = ".quad";
 265     }
 266
 267 } elsif ($arch eq "arm") {
 268     $alignment = 2;
 269     $section_type = '%progbits';
 270
 271 } elsif ($arch eq "ia64") {
 272     $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
 273     $type = "data8";
 274
 275     if ($is_module eq "0") {
 276         $cc .= " -mconstant-gp";
 277     }
 278 } elsif ($arch eq "sparc64") {
 279     # In the objdump output there are giblets like:
 280     # 0000000000000000 <igmp_net_exit-0x18>:
 281     # As there's some data blobs that get emitted into the
 282     # text section before the first instructions and the first
 283     # real symbols.  We don't want to match that, so to combat
 284     # this we use '\w' so we'll match just plain symbol names,
 285     # and not those that also include hex offsets inside of the
 286     # '<>' brackets.  Actually the generic function_regex setting
 287     # could safely use this too.
 288     $function_regex = "^([0-9a-fA-F]+)\\s+<(\\w*?)>:";
 289
 290     # Sparc64 calls '_mcount' instead of plain 'mcount'.
 291     $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
 292
 293     $alignment = 8;
 294     $type = ".xword";
 295     $ld .= " -m elf64_sparc";
 296     $cc .= " -m64";
 297     $objcopy .= " -O elf64-sparc";
 298 } elsif ($arch eq "mips") {
 299     # To enable module support, we need to enable the -mlong-calls option
 300     # of gcc for module, after using this option, we can not get the real
 301     # offset of the calling to _mcount, but the offset of the lui
 302     # instruction or the addiu one. herein, we record the address of the
 303     # first one, and then we can replace this instruction by a branch
 304     # instruction to jump over the profiling function to filter the
 305     # indicated functions, or swith back to the lui instruction to trace
 306     # them, which means dynamic tracing.
 307     #
 308     #       c:  3c030000        lui     v1,0x0
 309     #                   c: R_MIPS_HI16  _mcount
 310     #                   c: R_MIPS_NONE  *ABS*
 311     #                   c: R_MIPS_NONE  *ABS*
 312     #      10:  64630000        daddiu  v1,v1,0
 313     #                   10: R_MIPS_LO16 _mcount
 314     #                   10: R_MIPS_NONE *ABS*
 315     #                   10: R_MIPS_NONE *ABS*
 316     #      14:  03e0082d        move    at,ra
 317     #      18:  0060f809        jalr    v1
 318     #
 319     # for the kernel:
 320     #
 321     #     10:   03e0082d        move    at,ra
 322     #     14:   0c000000        jal     0 <loongson_halt>
 323     #                    14: R_MIPS_26   _mcount
 324     #                    14: R_MIPS_NONE *ABS*
 325     #                    14: R_MIPS_NONE *ABS*
 326     #    18:   00020021        nop
 327     if ($is_module eq "0") {
 328             $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
 329     } else {
 330             $mcount_regex = "^\\s*([0-9a-fA-F]+): R_MIPS_HI16\\s+_mcount\$";
 331     }
 332     $objdump .= " -Melf-trad".$endian."mips ";
 333
 334     if ($endian eq "big") {
 335             $endian = " -EB ";
 336             $ld .= " -melf".$bits."btsmip";
 337     } else {
 338             $endian = " -EL ";
 339             $ld .= " -melf".$bits."ltsmip";
 340     }
 341
 342     $cc .= " -mno-abicalls -fno-pic -mabi=" . $bits . $endian;
 343     $ld .= $endian;
 344
 345     if ($bits == 64) {
 346             $function_regex =
 347                 "^([0-9a-fA-F]+)\\s+<(.|[^\$]L.*?|\$[^L].*?|[^\$][^L].*?)>:";
 348             $type = ".dword";
 349     }
 350 } elsif ($arch eq "microblaze") {
 351     # Microblaze calls '_mcount' instead of plain 'mcount'.
 352     $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
 353 } else {
 354     die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD";
 355 }
 356
 357 my $text_found = 0;
 358 my $read_function = 0;
 359 my $opened = 0;
 360 my $mcount_section = "__mcount_loc";
 361
 362 my $dirname;
 363 my $filename;
 364 my $prefix;
 365 my $ext;
 366
 367 if ($inputfile =~ m,^(.*)/([^/]*)$,) {
 368     $dirname = $1;
 369     $filename = $2;
 370 } else {
 371     $dirname = ".";
 372     $filename = $inputfile;
 373 }
 374
 375 if ($filename =~ m,^(.*)(\.\S),) {
 376     $prefix = $1;
 377     $ext = $2;
 378 } else {
 379     $prefix = $filename;
 380     $ext = "";
 381 }
 382
 383 my $mcount_s = $dirname . "/.tmp_mc_" . $prefix . ".s";
 384 my $mcount_o = $dirname . "/.tmp_mc_" . $prefix . ".o";
 385
 386 check_objcopy();
 387
 388 #
 389 # Step 1: find all the local (static functions) and weak symbols.
 390 #         't' is local, 'w/W' is weak
 391 #
 392 open (IN, "$nm $inputfile|") || die "error running $nm";
 393 while (<IN>) {
 394     if (/$local_regex/) {
 395         $locals{$1} = 1;
 396     } elsif (/$weak_regex/) {
 397         $weak{$2} = $1;
 398     }
 399 }
 400 close(IN);
 401
 402 my @offsets;            # Array of offsets of mcount callers
 403 my $ref_func;           # reference function to use for offsets
 404 my $offset = 0;         # offset of ref_func to section beginning
 405
 406 ##
 407 # update_funcs - print out the current mcount callers
 408 #
 409 #  Go through the list of offsets to callers and write them to
 410 #  the output file in a format that can be read by an assembler.
 411 #
 412 sub update_funcs
 413 {
 414     return unless ($ref_func and @offsets);
 415
 416     # Sanity check on weak function. A weak function may be overwritten by
 417     # another function of the same name, making all these offsets incorrect.
 418     if (defined $weak{$ref_func}) {
 419         die "$inputfile: ERROR: referencing weak function" .
 420             " $ref_func for mcount\n";
 421     }
 422
 423     # is this function static? If so, note this fact.
 424     if (defined $locals{$ref_func}) {
 425
 426         # only use locals if objcopy supports globalize-symbols
 427         if (!$can_use_local) {
 428             return;
 429         }
 430         $convert{$ref_func} = 1;
 431     }
 432
 433     # Loop through all the mcount caller offsets and print a reference
 434     # to the caller based from the ref_func.
 435     for (my $i=0; $i <= $#offsets; $i++) {
 436         if (!$opened) {
 437             open(FILE, ">$mcount_s") || die "can't create $mcount_s\n";
 438             $opened = 1;
 439             print FILE "\t.section $mcount_section,\"a\",$section_type\n";
 440             print FILE "\t.align $alignment\n" if (defined($alignment));
 441         }
 442         printf FILE "\t%s %s + %d\n", $type, $ref_func, $offsets[$i] - $offset;
 443     }
 444 }
 445
 446 #
 447 # Step 2: find the sections and mcount call sites
 448 #
 449 open(IN, "$objdump -hdr $inputfile|") || die "error running $objdump";
 450
 451 my $text;
 452
 453
 454 # read headers first
 455 my $read_headers = 1;
 456
 457 while (<IN>) {
 458
 459     if ($read_headers && /$mcount_section/) {
 460         #
 461         # Somehow the make process can execute this script on an
 462         # object twice. If it does, we would duplicate the mcount
 463         # section and it will cause the function tracer self test
 464         # to fail. Check if the mcount section exists, and if it does,
 465         # warn and exit.
 466         #
 467         print STDERR "ERROR: $mcount_section already in $inputfile\n" .
 468             "\tThis may be an indication that your build is corrupted.\n" .
 469             "\tDelete $inputfile and try again. If the same object file\n" .
 470             "\tstill causes an issue, then disable CONFIG_DYNAMIC_FTRACE.\n";
 471         exit(-1);
 472     }
 473
 474     # is it a section?
 475     if (/$section_regex/) {
 476         $read_headers = 0;
 477
 478         # Only record text sections that we know are safe
 479         if (defined($text_sections{$1})) {
 480             $read_function = 1;
 481         } else {
 482             $read_function = 0;
 483         }
 484         # print out any recorded offsets
 485         update_funcs();
 486
 487         # reset all markers and arrays
 488         $text_found = 0;
 489         undef($ref_func);
 490         undef(@offsets);
 491
 492     # section found, now is this a start of a function?
 493     } elsif ($read_function && /$function_regex/) {
 494         $text_found = 1;
 495         $text = $2;
 496
 497         # if this is either a local function or a weak function
 498         # keep looking for functions that are global that
 499         # we can use safely.
 500         if (!defined($locals{$text}) && !defined($weak{$text})) {
 501             $ref_func = $text;
 502             $read_function = 0;
 503             $offset = hex $1;
 504         } else {
 505             # if we already have a function, and this is weak, skip it
 506             if (!defined($ref_func) && !defined($weak{$text}) &&
 507                  # PPC64 can have symbols that start with .L and
 508                  # gcc considers these special. Don't use them!
 509                  $text !~ /^\.L/) {
 510                 $ref_func = $text;
 511                 $offset = hex $1;
 512             }
 513         }
 514     }
 515     # is this a call site to mcount? If so, record it to print later
 516     if ($text_found && /$mcount_regex/) {
 517         $offsets[$#offsets + 1] = hex $1;
 518     }
 519 }
 520
 521 # dump out anymore offsets that may have been found
 522 update_funcs();
 523
 524 # If we did not find any mcount callers, we are done (do nothing).
 525 if (!$opened) {
 526     exit(0);
 527 }
 528
 529 close(FILE);
 530
 531 #
 532 # Step 3: Compile the file that holds the list of call sites to mcount.
 533 #
 534 `$cc -o $mcount_o -c $mcount_s`;
 535
 536 my @converts = keys %convert;
 537
 538 #
 539 # Step 4: Do we have sections that started with local functions?
 540 #
 541 if ($#converts >= 0) {
 542     my $globallist = "";
 543     my $locallist = "";
 544
 545     foreach my $con (@converts) {
 546         $globallist .= " --globalize-symbol $con";
 547         $locallist .= " --localize-symbol $con";
 548     }
 549
 550     my $globalobj = $dirname . "/.tmp_gl_" . $filename;
 551     my $globalmix = $dirname . "/.tmp_mx_" . $filename;
 552
 553     #
 554     # Step 5: set up each local function as a global
 555     #
 556     `$objcopy $globallist $inputfile $globalobj`;
 557
 558     #
 559     # Step 6: Link the global version to our list.
 560     #
 561     `$ld -r $globalobj $mcount_o -o $globalmix`;
 562
 563     #
 564     # Step 7: Convert the local functions back into local symbols
 565     #
 566     `$objcopy $locallist $globalmix $inputfile`;
 567
 568     # Remove the temp files
 569     `$rm $globalobj $globalmix`;
 570
 571 } else {
 572
 573     my $mix = $dirname . "/.tmp_mx_" . $filename;
 574
 575     #
 576     # Step 8: Link the object with our list of call sites object.
 577     #
 578     `$ld -r $inputfile $mcount_o -o $mix`;
 579
 580     #
 581     # Step 9: Move the result back to the original object.
 582     #
 583     `$mv $mix $inputfile`;
 584 }
 585
 586 # Clean up the temp files
 587 `$rm $mcount_o $mcount_s`;
 588
 589 exit(0);