LXR linux/scripts/recordmcount.pl

   1#!/usr/bin/env perl
   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
 109use warnings;
 110use strict;
 111
 112my $P = $0;
 113$P =~ s@.*/@@g;
 114
 115my $V = '0.1';
 116
 117if ($#ARGV != 11) {
 118        print "usage: $P arch endian bits objdump objcopy cc ld nm rm mv is_module inputfile\n";
 119        print "version: $V\n";
 120        exit(1);
 121}
 122
 123my ($arch, $endian, $bits, $objdump, $objcopy, $cc,
 124    $ld, $nm, $rm, $mv, $is_module, $inputfile) = @ARGV;
 125
 126# This file refers to mcount and shouldn't be ftraced, so lets' ignore it
 127if ($inputfile =~ m,kernel/trace/ftrace\.o$,) {
 128    exit(0);
 129}
 130
 131# Acceptable sections to record.
 132my %text_sections = (
 133     ".text" => 1,
 134     ".init.text" => 1,
 135     ".ref.text" => 1,
 136     ".sched.text" => 1,
 137     ".spinlock.text" => 1,
 138     ".irqentry.text" => 1,
 139     ".softirqentry.text" => 1,
 140     ".kprobes.text" => 1,
 141     ".cpuidle.text" => 1,
 142     ".text.unlikely" => 1,
 143);
 144
 145# Note: we are nice to C-programmers here, thus we skip the '||='-idiom.
 146$objdump = 'objdump' if (!$objdump);
 147$objcopy = 'objcopy' if (!$objcopy);
 148$cc = 'gcc' if (!$cc);
 149$ld = 'ld' if (!$ld);
 150$nm = 'nm' if (!$nm);
 151$rm = 'rm' if (!$rm);
 152$mv = 'mv' if (!$mv);
 153
 154#print STDERR "running: $P '$arch' '$objdump' '$objcopy' '$cc' '$ld' " .
 155#    "'$nm' '$rm' '$mv' '$inputfile'\n";
 156
 157my %locals;             # List of local (static) functions
 158my %weak;               # List of weak functions
 159my %convert;            # List of local functions used that needs conversion
 160
 161my $type;
 162my $local_regex;        # Match a local function (return function)
 163my $weak_regex;         # Match a weak function (return function)
 164my $section_regex;      # Find the start of a section
 165my $function_regex;     # Find the name of a function
 166                        #    (return offset and func name)
 167my $mcount_regex;       # Find the call site to mcount (return offset)
 168my $mcount_adjust;      # Address adjustment to mcount offset
 169my $alignment;          # The .align value to use for $mcount_section
 170my $section_type;       # Section header plus possible alignment command
 171my $can_use_local = 0;  # If we can use local function references
 172
 173# Shut up recordmcount if user has older objcopy
 174my $quiet_recordmcount = ".tmp_quiet_recordmcount";
 175my $print_warning = 1;
 176$print_warning = 0 if ( -f $quiet_recordmcount);
 177
 178##
 179# check_objcopy - whether objcopy supports --globalize-symbols
 180#
 181#  --globalize-symbols came out in 2.17, we must test the version
 182#  of objcopy, and if it is less than 2.17, then we can not
 183#  record local functions.
 184sub check_objcopy
 185{
 186    open (IN, "$objcopy --version |") or die "error running $objcopy";
 187    while (<IN>) {
 188        if (/objcopy.*\s(\d+)\.(\d+)/) {
 189            $can_use_local = 1 if ($1 > 2 || ($1 == 2 && $2 >= 17));
 190            last;
 191        }
 192    }
 193    close (IN);
 194
 195    if (!$can_use_local && $print_warning) {
 196        print STDERR "WARNING: could not find objcopy version or version " .
 197            "is less than 2.17.\n" .
 198            "\tLocal function references are disabled.\n";
 199        open (QUIET, ">$quiet_recordmcount");
 200        printf QUIET "Disables the warning from recordmcount.pl\n";
 201        close QUIET;
 202    }
 203}
 204
 205if ($arch =~ /(x86(_64)?)|(i386)/) {
 206    if ($bits == 64) {
 207        $arch = "x86_64";
 208    } else {
 209        $arch = "i386";
 210    }
 211}
 212
 213#
 214# We base the defaults off of i386, the other archs may
 215# feel free to change them in the below if statements.
 216#
 217$local_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\S+)";
 218$weak_regex = "^[0-9a-fA-F]+\\s+([wW])\\s+(\\S+)";
 219$section_regex = "Disassembly of section\\s+(\\S+):";
 220$function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
 221$mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s(mcount|__fentry__)\$";
 222$section_type = '@progbits';
 223$mcount_adjust = 0;
 224$type = ".long";
 225
 226if ($arch eq "x86_64") {
 227    $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s(mcount|__fentry__)([+-]0x[0-9a-zA-Z]+)?\$";
 228    $type = ".quad";
 229    $alignment = 8;
 230    $mcount_adjust = -1;
 231
 232    # force flags for this arch
 233    $ld .= " -m elf_x86_64";
 234    $objdump .= " -M x86-64";
 235    $objcopy .= " -O elf64-x86-64";
 236    $cc .= " -m64";
 237
 238} elsif ($arch eq "i386") {
 239    $alignment = 4;
 240    $mcount_adjust = -1;
 241
 242    # force flags for this arch
 243    $ld .= " -m elf_i386";
 244    $objdump .= " -M i386";
 245    $objcopy .= " -O elf32-i386";
 246    $cc .= " -m32";
 247
 248} elsif ($arch eq "s390" && $bits == 64) {
 249    if ($cc =~ /-DCC_USING_HOTPATCH/) {
 250        $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*c0 04 00 00 00 00\\s*brcl\\s*0,[0-9a-f]+ <([^\+]*)>\$";
 251        $mcount_adjust = 0;
 252    } else {
 253        $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_390_(PC|PLT)32DBL\\s+_mcount\\+0x2\$";
 254        $mcount_adjust = -14;
 255    }
 256    $alignment = 8;
 257    $type = ".quad";
 258    $ld .= " -m elf64_s390";
 259    $cc .= " -m64";
 260
 261} elsif ($arch eq "sh") {
 262    $alignment = 2;
 263
 264    # force flags for this arch
 265    $ld .= " -m shlelf_linux";
 266    $objcopy .= " -O elf32-sh-linux";
 267
 268} elsif ($arch eq "powerpc") {
 269    my $ldemulation;
 270
 271    $local_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\.?\\S+)";
 272    # See comment in the sparc64 section for why we use '\w'.
 273    $function_regex = "^([0-9a-fA-F]+)\\s+<(\\.?\\w*?)>:";
 274    $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s\\.?_mcount\$";
 275
 276    if ($endian eq "big") {
 277            $cc .= " -mbig-endian ";
 278            $ld .= " -EB ";
 279            $ldemulation = "ppc"
 280    } else {
 281            $cc .= " -mlittle-endian ";
 282            $ld .= " -EL ";
 283            $ldemulation = "lppc"
 284    }
 285    if ($bits == 64) {
 286        $type = ".quad";
 287        $cc .= " -m64 ";
 288        $ld .= " -m elf64".$ldemulation." ";
 289    } else {
 290        $cc .= " -m32 ";
 291        $ld .= " -m elf32".$ldemulation." ";
 292    }
 293
 294} elsif ($arch eq "arm") {
 295    $alignment = 2;
 296    $section_type = '%progbits';
 297    $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_ARM_(CALL|PC24|THM_CALL)" .
 298                        "\\s+(__gnu_mcount_nc|mcount)\$";
 299
 300} elsif ($arch eq "arm64") {
 301    $alignment = 3;
 302    $section_type = '%progbits';
 303    $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_AARCH64_CALL26\\s+_mcount\$";
 304    $type = ".quad";
 305} elsif ($arch eq "ia64") {
 306    $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
 307    $type = "data8";
 308
 309    if ($is_module eq "0") {
 310        $cc .= " -mconstant-gp";
 311    }
 312} elsif ($arch eq "sparc64") {
 313    # In the objdump output there are giblets like:
 314    # 0000000000000000 <igmp_net_exit-0x18>:
 315    # As there's some data blobs that get emitted into the
 316    # text section before the first instructions and the first
 317    # real symbols.  We don't want to match that, so to combat
 318    # this we use '\w' so we'll match just plain symbol names,
 319    # and not those that also include hex offsets inside of the
 320    # '<>' brackets.  Actually the generic function_regex setting
 321    # could safely use this too.
 322    $function_regex = "^([0-9a-fA-F]+)\\s+<(\\w*?)>:";
 323
 324    # Sparc64 calls '_mcount' instead of plain 'mcount'.
 325    $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
 326
 327    $alignment = 8;
 328    $type = ".xword";
 329    $ld .= " -m elf64_sparc";
 330    $cc .= " -m64";
 331    $objcopy .= " -O elf64-sparc";
 332} elsif ($arch eq "mips") {
 333    # To enable module support, we need to enable the -mlong-calls option
 334    # of gcc for module, after using this option, we can not get the real
 335    # offset of the calling to _mcount, but the offset of the lui
 336    # instruction or the addiu one. herein, we record the address of the
 337    # first one, and then we can replace this instruction by a branch
 338    # instruction to jump over the profiling function to filter the
 339    # indicated functions, or switch back to the lui instruction to trace
 340    # them, which means dynamic tracing.
 341    #
 342    #       c:  3c030000        lui     v1,0x0
 343    #                   c: R_MIPS_HI16  _mcount
 344    #                   c: R_MIPS_NONE  *ABS*
 345    #                   c: R_MIPS_NONE  *ABS*
 346    #      10:  64630000        daddiu  v1,v1,0
 347    #                   10: R_MIPS_LO16 _mcount
 348    #                   10: R_MIPS_NONE *ABS*
 349    #                   10: R_MIPS_NONE *ABS*
 350    #      14:  03e0082d        move    at,ra
 351    #      18:  0060f809        jalr    v1
 352    #
 353    # for the kernel:
 354    #
 355    #     10:   03e0082d        move    at,ra
 356    #     14:   0c000000        jal     0 <loongson_halt>
 357    #                    14: R_MIPS_26   _mcount
 358    #                    14: R_MIPS_NONE *ABS*
 359    #                    14: R_MIPS_NONE *ABS*
 360    #    18:   00020021        nop
 361    if ($is_module eq "0") {
 362            $mcount_regex = "^\\s*([0-9a-fA-F]+): R_MIPS_26\\s+_mcount\$";
 363    } else {
 364            $mcount_regex = "^\\s*([0-9a-fA-F]+): R_MIPS_HI16\\s+_mcount\$";
 365    }
 366    $objdump .= " -Melf-trad".$endian."mips ";
 367
 368    if ($endian eq "big") {
 369            $endian = " -EB ";
 370            $ld .= " -melf".$bits."btsmip";
 371    } else {
 372            $endian = " -EL ";
 373            $ld .= " -melf".$bits."ltsmip";
 374    }
 375
 376    $cc .= " -mno-abicalls -fno-pic -mabi=" . $bits . $endian;
 377    $ld .= $endian;
 378
 379    if ($bits == 64) {
 380            $function_regex =
 381                "^([0-9a-fA-F]+)\\s+<(.|[^\$]L.*?|\$[^L].*?|[^\$][^L].*?)>:";
 382            $type = ".dword";
 383    }
 384} elsif ($arch eq "microblaze") {
 385    # Microblaze calls '_mcount' instead of plain 'mcount'.
 386    $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
 387} elsif ($arch eq "riscv") {
 388    $function_regex = "^([0-9a-fA-F]+)\\s+<([^.0-9][0-9a-zA-Z_\\.]+)>:";
 389    $mcount_regex = "^\\s*([0-9a-fA-F]+):\\sR_RISCV_CALL\\s_mcount\$";
 390    $type = ".quad";
 391    $alignment = 2;
 392} else {
 393    die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD";
 394}
 395
 396my $text_found = 0;
 397my $read_function = 0;
 398my $opened = 0;
 399my $mcount_section = "__mcount_loc";
 400
 401my $dirname;
 402my $filename;
 403my $prefix;
 404my $ext;
 405
 406if ($inputfile =~ m,^(.*)/([^/]*)$,) {
 407    $dirname = $1;
 408    $filename = $2;
 409} else {
 410    $dirname = ".";
 411    $filename = $inputfile;
 412}
 413
 414if ($filename =~ m,^(.*)(\.\S),) {
 415    $prefix = $1;
 416    $ext = $2;
 417} else {
 418    $prefix = $filename;
 419    $ext = "";
 420}
 421
 422my $mcount_s = $dirname . "/.tmp_mc_" . $prefix . ".s";
 423my $mcount_o = $dirname . "/.tmp_mc_" . $prefix . ".o";
 424
 425check_objcopy();
 426
 427#
 428# Step 1: find all the local (static functions) and weak symbols.
 429#         't' is local, 'w/W' is weak
 430#
 431open (IN, "$nm $inputfile|") || die "error running $nm";
 432while (<IN>) {
 433    if (/$local_regex/) {
 434        $locals{$1} = 1;
 435    } elsif (/$weak_regex/) {
 436        $weak{$2} = $1;
 437    }
 438}
 439close(IN);
 440
 441my @offsets;            # Array of offsets of mcount callers
 442my $ref_func;           # reference function to use for offsets
 443my $offset = 0;         # offset of ref_func to section beginning
 444
 445##
 446# update_funcs - print out the current mcount callers
 447#
 448#  Go through the list of offsets to callers and write them to
 449#  the output file in a format that can be read by an assembler.
 450#
 451sub update_funcs
 452{
 453    return unless ($ref_func and @offsets);
 454
 455    # Sanity check on weak function. A weak function may be overwritten by
 456    # another function of the same name, making all these offsets incorrect.
 457    if (defined $weak{$ref_func}) {
 458        die "$inputfile: ERROR: referencing weak function" .
 459            " $ref_func for mcount\n";
 460    }
 461
 462    # is this function static? If so, note this fact.
 463    if (defined $locals{$ref_func}) {
 464
 465        # only use locals if objcopy supports globalize-symbols
 466        if (!$can_use_local) {
 467            return;
 468        }
 469        $convert{$ref_func} = 1;
 470    }
 471
 472    # Loop through all the mcount caller offsets and print a reference
 473    # to the caller based from the ref_func.
 474    if (!$opened) {
 475        open(FILE, ">$mcount_s") || die "can't create $mcount_s\n";
 476        $opened = 1;
 477        print FILE "\t.section $mcount_section,\"a\",$section_type\n";
 478        print FILE "\t.align $alignment\n" if (defined($alignment));
 479    }
 480    foreach my $cur_offset (@offsets) {
 481        printf FILE "\t%s %s + %d\n", $type, $ref_func, $cur_offset - $offset;
 482    }
 483}
 484
 485#
 486# Step 2: find the sections and mcount call sites
 487#
 488open(IN, "$objdump -hdr $inputfile|") || die "error running $objdump";
 489
 490my $text;
 491
 492
 493# read headers first
 494my $read_headers = 1;
 495
 496while (<IN>) {
 497
 498    if ($read_headers && /$mcount_section/) {
 499        #
 500        # Somehow the make process can execute this script on an
 501        # object twice. If it does, we would duplicate the mcount
 502        # section and it will cause the function tracer self test
 503        # to fail. Check if the mcount section exists, and if it does,
 504        # warn and exit.
 505        #
 506        print STDERR "ERROR: $mcount_section already in $inputfile\n" .
 507            "\tThis may be an indication that your build is corrupted.\n" .
 508            "\tDelete $inputfile and try again. If the same object file\n" .
 509            "\tstill causes an issue, then disable CONFIG_DYNAMIC_FTRACE.\n";
 510        exit(-1);
 511    }
 512
 513    # is it a section?
 514    if (/$section_regex/) {
 515        $read_headers = 0;
 516
 517        # Only record text sections that we know are safe
 518        $read_function = defined($text_sections{$1});
 519        # print out any recorded offsets
 520        update_funcs();
 521
 522        # reset all markers and arrays
 523        $text_found = 0;
 524        undef($ref_func);
 525        undef(@offsets);
 526
 527    # section found, now is this a start of a function?
 528    } elsif ($read_function && /$function_regex/) {
 529        $text_found = 1;
 530        $text = $2;
 531
 532        # if this is either a local function or a weak function
 533        # keep looking for functions that are global that
 534        # we can use safely.
 535        if (!defined($locals{$text}) && !defined($weak{$text})) {
 536            $ref_func = $text;
 537            $read_function = 0;
 538            $offset = hex $1;
 539        } else {
 540            # if we already have a function, and this is weak, skip it
 541            if (!defined($ref_func) && !defined($weak{$text}) &&
 542                 # PPC64 can have symbols that start with .L and
 543                 # gcc considers these special. Don't use them!
 544                 $text !~ /^\.L/) {
 545                $ref_func = $text;
 546                $offset = hex $1;
 547            }
 548        }
 549    }
 550    # is this a call site to mcount? If so, record it to print later
 551    if ($text_found && /$mcount_regex/) {
 552        push(@offsets, (hex $1) + $mcount_adjust);
 553    }
 554}
 555
 556# dump out anymore offsets that may have been found
 557update_funcs();
 558
 559# If we did not find any mcount callers, we are done (do nothing).
 560if (!$opened) {
 561    exit(0);
 562}
 563
 564close(FILE);
 565
 566#
 567# Step 3: Compile the file that holds the list of call sites to mcount.
 568#
 569`$cc -o $mcount_o -c $mcount_s`;
 570
 571my @converts = keys %convert;
 572
 573#
 574# Step 4: Do we have sections that started with local functions?
 575#
 576if ($#converts >= 0) {
 577    my $globallist = "";
 578    my $locallist = "";
 579
 580    foreach my $con (@converts) {
 581        $globallist .= " --globalize-symbol $con";
 582        $locallist .= " --localize-symbol $con";
 583    }
 584
 585    my $globalobj = $dirname . "/.tmp_gl_" . $filename;
 586    my $globalmix = $dirname . "/.tmp_mx_" . $filename;
 587
 588    #
 589    # Step 5: set up each local function as a global
 590    #
 591    `$objcopy $globallist $inputfile $globalobj`;
 592
 593    #
 594    # Step 6: Link the global version to our list.
 595    #
 596    `$ld -r $globalobj $mcount_o -o $globalmix`;
 597
 598    #
 599    # Step 7: Convert the local functions back into local symbols
 600    #
 601    `$objcopy $locallist $globalmix $inputfile`;
 602
 603    # Remove the temp files
 604    `$rm $globalobj $globalmix`;
 605
 606} else {
 607
 608    my $mix = $dirname . "/.tmp_mx_" . $filename;
 609
 610    #
 611    # Step 8: Link the object with our list of call sites object.
 612    #
 613    `$ld -r $inputfile $mcount_o -o $mix`;
 614
 615    #
 616    # Step 9: Move the result back to the original object.
 617    #
 618    `$mv $mix $inputfile`;
 619}
 620
 621# Clean up the temp files
 622`$rm $mcount_o $mcount_s`;
 623
 624exit(0);
 625