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 109use strict; 110 111my $P = $0; 112$P =~ s@.*/@@g; 113 114my $V = '0.1'; 115 116if ($#ARGV != 11) { 117 print "usage: $P arch endian bits objdump objcopy cc ld nm rm mv is_module inputfile\n"; 118 print "version: $V\n"; 119 exit(1); 120} 121 122my ($arch, $endian, $bits, $objdump, $objcopy, $cc, 123 $ld, $nm, $rm, $mv, $is_module, $inputfile) = @ARGV; 124 125# This file refers to mcount and shouldn't be ftraced, so lets' ignore it 126if ($inputfile =~ m,kernel/trace/ftrace\.o$,) { 127 exit(0); 128} 129 130# Acceptable sections to record. 131my %text_sections = ( 132 ".text" => 1, 133 ".ref.text" => 1, 134 ".sched.text" => 1, 135 ".spinlock.text" => 1, 136 ".irqentry.text" => 1, 137 ".kprobes.text" => 1, 138 ".text.unlikely" => 1, 139); 140 141# Note: we are nice to C-programmers here, thus we skip the '||='-idiom. 142$objdump = 'objdump' if (!$objdump); 143$objcopy = 'objcopy' if (!$objcopy); 144$cc = 'gcc' if (!$cc); 145$ld = 'ld' if (!$ld); 146$nm = 'nm' if (!$nm); 147$rm = 'rm' if (!$rm); 148$mv = 'mv' if (!$mv); 149 150#print STDERR "running: $P '$arch' '$objdump' '$objcopy' '$cc' '$ld' " . 151# "'$nm' '$rm' '$mv' '$inputfile'\n"; 152 153my %locals; # List of local (static) functions 154my %weak; # List of weak functions 155my %convert; # List of local functions used that needs conversion 156 157my $type; 158my $local_regex; # Match a local function (return function) 159my $weak_regex; # Match a weak function (return function) 160my $section_regex; # Find the start of a section 161my $function_regex; # Find the name of a function 162 # (return offset and func name) 163my $mcount_regex; # Find the call site to mcount (return offset) 164my $mcount_adjust; # Address adjustment to mcount offset 165my $alignment; # The .align value to use for $mcount_section 166my $section_type; # Section header plus possible alignment command 167my $can_use_local = 0; # If we can use local function references 168 169# Shut up recordmcount if user has older objcopy 170my $quiet_recordmcount = ".tmp_quiet_recordmcount"; 171my $print_warning = 1; 172$print_warning = 0 if ( -f $quiet_recordmcount); 173 174## 175# check_objcopy - whether objcopy supports --globalize-symbols 176# 177# --globalize-symbols came out in 2.17, we must test the version 178# of objcopy, and if it is less than 2.17, then we can not 179# record local functions. 180sub check_objcopy 181{ 182 open (IN, "$objcopy --version |") or die "error running $objcopy"; 183 while (<IN>) { 184 if (/objcopy.*\s(\d+)\.(\d+)/) { 185 $can_use_local = 1 if ($1 > 2 || ($1 == 2 && $2 >= 17)); 186 last; 187 } 188 } 189 close (IN); 190 191 if (!$can_use_local && $print_warning) { 192 print STDERR "WARNING: could not find objcopy version or version " . 193 "is less than 2.17.\n" . 194 "\tLocal function references are disabled.\n"; 195 open (QUIET, ">$quiet_recordmcount"); 196 printf QUIET "Disables the warning from recordmcount.pl\n"; 197 close QUIET; 198 } 199} 200 201if ($arch =~ /(x86(_64)?)|(i386)/) { 202 if ($bits == 64) { 203 $arch = "x86_64"; 204 } else { 205 $arch = "i386"; 206 } 207} 208 209# 210# We base the defaults off of i386, the other archs may 211# feel free to change them in the below if statements. 212# 213$local_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\S+)"; 214$weak_regex = "^[0-9a-fA-F]+\\s+([wW])\\s+(\\S+)"; 215$section_regex = "Disassembly of section\\s+(\\S+):"; 216$function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:"; 217$mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount\$"; 218$section_type = '@progbits'; 219$mcount_adjust = 0; 220$type = ".long"; 221 222if ($arch eq "x86_64") { 223 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount([+-]0x[0-9a-zA-Z]+)?\$"; 224 $type = ".quad"; 225 $alignment = 8; 226 $mcount_adjust = -1; 227 228 # force flags for this arch 229 $ld .= " -m elf_x86_64"; 230 $objdump .= " -M x86-64"; 231 $objcopy .= " -O elf64-x86-64"; 232 $cc .= " -m64"; 233 234} elsif ($arch eq "i386") { 235 $alignment = 4; 236 $mcount_adjust = -1; 237 238 # force flags for this arch 239 $ld .= " -m elf_i386"; 240 $objdump .= " -M i386"; 241 $objcopy .= " -O elf32-i386"; 242 $cc .= " -m32"; 243 244} elsif ($arch eq "s390" && $bits == 32) { 245 $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_390_32\\s+_mcount\$"; 246 $mcount_adjust = -4; 247 $alignment = 4; 248 $ld .= " -m elf_s390"; 249 $cc .= " -m31"; 250 251} elsif ($arch eq "s390" && $bits == 64) { 252 $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_390_(PC|PLT)32DBL\\s+_mcount\\+0x2\$"; 253 $mcount_adjust = -8; 254 $alignment = 8; 255 $type = ".quad"; 256 $ld .= " -m elf64_s390"; 257 $cc .= " -m64"; 258 259} elsif ($arch eq "sh") { 260 $alignment = 2; 261 262 # force flags for this arch 263 $ld .= " -m shlelf_linux"; 264 $objcopy .= " -O elf32-sh-linux"; 265 $cc .= " -m32"; 266 267} elsif ($arch eq "powerpc") { 268 $local_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\.?\\S+)"; 269 $function_regex = "^([0-9a-fA-F]+)\\s+<(\\.?.*?)>:"; 270 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s\\.?_mcount\$"; 271 272 if ($bits == 64) { 273 $type = ".quad"; 274 } 275 276} elsif ($arch eq "arm") { 277 $alignment = 2; 278 $section_type = '%progbits'; 279 $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_ARM_(CALL|PC24|THM_CALL)" . 280 "\\s+(__gnu_mcount_nc|mcount)\$"; 281 282} elsif ($arch eq "ia64") { 283 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$"; 284 $type = "data8"; 285 286 if ($is_module eq "0") { 287 $cc .= " -mconstant-gp"; 288 } 289} elsif ($arch eq "sparc64") { 290 # In the objdump output there are giblets like: 291 # 0000000000000000 <igmp_net_exit-0x18>: 292 # As there's some data blobs that get emitted into the 293 # text section before the first instructions and the first 294 # real symbols. We don't want to match that, so to combat 295 # this we use '\w' so we'll match just plain symbol names, 296 # and not those that also include hex offsets inside of the 297 # '<>' brackets. Actually the generic function_regex setting 298 # could safely use this too. 299 $function_regex = "^([0-9a-fA-F]+)\\s+<(\\w*?)>:"; 300 301 # Sparc64 calls '_mcount' instead of plain 'mcount'. 302 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$"; 303 304 $alignment = 8; 305 $type = ".xword"; 306 $ld .= " -m elf64_sparc"; 307 $cc .= " -m64"; 308 $objcopy .= " -O elf64-sparc"; 309} elsif ($arch eq "mips") { 310 # To enable module support, we need to enable the -mlong-calls option 311 # of gcc for module, after using this option, we can not get the real 312 # offset of the calling to _mcount, but the offset of the lui 313 # instruction or the addiu one. herein, we record the address of the 314 # first one, and then we can replace this instruction by a branch 315 # instruction to jump over the profiling function to filter the 316 # indicated functions, or swith back to the lui instruction to trace 317 # them, which means dynamic tracing. 318 # 319 # c: 3c030000 lui v1,0x0 320 # c: R_MIPS_HI16 _mcount 321 # c: R_MIPS_NONE *ABS* 322 # c: R_MIPS_NONE *ABS* 323 # 10: 64630000 daddiu v1,v1,0 324 # 10: R_MIPS_LO16 _mcount 325 # 10: R_MIPS_NONE *ABS* 326 # 10: R_MIPS_NONE *ABS* 327 # 14: 03e0082d move at,ra 328 # 18: 0060f809 jalr v1 329 # 330 # for the kernel: 331 # 332 # 10: 03e0082d move at,ra 333 # 14: 0c000000 jal 0 <loongson_halt> 334 # 14: R_MIPS_26 _mcount 335 # 14: R_MIPS_NONE *ABS* 336 # 14: R_MIPS_NONE *ABS* 337 # 18: 00020021 nop 338 if ($is_module eq "0") { 339 $mcount_regex = "^\\s*([0-9a-fA-F]+): R_MIPS_26\\s+_mcount\$"; 340 } else { 341 $mcount_regex = "^\\s*([0-9a-fA-F]+): R_MIPS_HI16\\s+_mcount\$"; 342 } 343 $objdump .= " -Melf-trad".$endian."mips "; 344 345 if ($endian eq "big") { 346 $endian = " -EB "; 347 $ld .= " -melf".$bits."btsmip"; 348 } else { 349 $endian = " -EL "; 350 $ld .= " -melf".$bits."ltsmip"; 351 } 352 353 $cc .= " -mno-abicalls -fno-pic -mabi=" . $bits . $endian; 354 $ld .= $endian; 355 356 if ($bits == 64) { 357 $function_regex = 358 "^([0-9a-fA-F]+)\\s+<(.|[^\$]L.*?|\$[^L].*?|[^\$][^L].*?)>:"; 359 $type = ".dword"; 360 } 361} elsif ($arch eq "microblaze") { 362 # Microblaze calls '_mcount' instead of plain 'mcount'. 363 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$"; 364} elsif ($arch eq "blackfin") { 365 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s__mcount\$"; 366 $mcount_adjust = -4; 367} else { 368 die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD"; 369} 370 371my $text_found = 0; 372my $read_function = 0; 373my $opened = 0; 374my $mcount_section = "__mcount_loc"; 375 376my $dirname; 377my $filename; 378my $prefix; 379my $ext; 380 381if ($inputfile =~ m,^(.*)/([^/]*)$,) { 382 $dirname = $1; 383 $filename = $2; 384} else { 385 $dirname = "."; 386 $filename = $inputfile; 387} 388 389if ($filename =~ m,^(.*)(\.\S),) { 390 $prefix = $1; 391 $ext = $2; 392} else { 393 $prefix = $filename; 394 $ext = ""; 395} 396 397my $mcount_s = $dirname . "/.tmp_mc_" . $prefix . ".s"; 398my $mcount_o = $dirname . "/.tmp_mc_" . $prefix . ".o"; 399 400check_objcopy(); 401 402# 403# Step 1: find all the local (static functions) and weak symbols. 404# 't' is local, 'w/W' is weak 405# 406open (IN, "$nm $inputfile|") || die "error running $nm"; 407while (<IN>) { 408 if (/$local_regex/) { 409 $locals{$1} = 1; 410 } elsif (/$weak_regex/) { 411 $weak{$2} = $1; 412 } 413} 414close(IN); 415 416my @offsets; # Array of offsets of mcount callers 417my $ref_func; # reference function to use for offsets 418my $offset = 0; # offset of ref_func to section beginning 419 420## 421# update_funcs - print out the current mcount callers 422# 423# Go through the list of offsets to callers and write them to 424# the output file in a format that can be read by an assembler. 425# 426sub update_funcs 427{ 428 return unless ($ref_func and @offsets); 429 430 # Sanity check on weak function. A weak function may be overwritten by 431 # another function of the same name, making all these offsets incorrect. 432 if (defined $weak{$ref_func}) { 433 die "$inputfile: ERROR: referencing weak function" . 434 " $ref_func for mcount\n"; 435 } 436 437 # is this function static? If so, note this fact. 438 if (defined $locals{$ref_func}) { 439 440 # only use locals if objcopy supports globalize-symbols 441 if (!$can_use_local) { 442 return; 443 } 444 $convert{$ref_func} = 1; 445 } 446 447 # Loop through all the mcount caller offsets and print a reference 448 # to the caller based from the ref_func. 449 if (!$opened) { 450 open(FILE, ">$mcount_s") || die "can't create $mcount_s\n"; 451 $opened = 1; 452 print FILE "\t.section $mcount_section,\"a\",$section_type\n"; 453 print FILE "\t.align $alignment\n" if (defined($alignment)); 454 } 455 foreach my $cur_offset (@offsets) { 456 printf FILE "\t%s %s + %d\n", $type, $ref_func, $cur_offset - $offset; 457 } 458} 459 460# 461# Step 2: find the sections and mcount call sites 462# 463open(IN, "$objdump -hdr $inputfile|") || die "error running $objdump"; 464 465my $text; 466 467 468# read headers first 469my $read_headers = 1; 470 471while (<IN>) { 472 473 if ($read_headers && /$mcount_section/) { 474 # 475 # Somehow the make process can execute this script on an 476 # object twice. If it does, we would duplicate the mcount 477 # section and it will cause the function tracer self test 478 # to fail. Check if the mcount section exists, and if it does, 479 # warn and exit. 480 # 481 print STDERR "ERROR: $mcount_section already in $inputfile\n" . 482 "\tThis may be an indication that your build is corrupted.\n" . 483 "\tDelete $inputfile and try again. If the same object file\n" . 484 "\tstill causes an issue, then disable CONFIG_DYNAMIC_FTRACE.\n"; 485 exit(-1); 486 } 487 488 # is it a section? 489 if (/$section_regex/) { 490 $read_headers = 0; 491 492 # Only record text sections that we know are safe 493 $read_function = defined($text_sections{$1}); 494 # print out any recorded offsets 495 update_funcs(); 496 497 # reset all markers and arrays 498 $text_found = 0; 499 undef($ref_func); 500 undef(@offsets); 501 502 # section found, now is this a start of a function? 503 } elsif ($read_function && /$function_regex/) { 504 $text_found = 1; 505 $text = $2; 506 507 # if this is either a local function or a weak function 508 # keep looking for functions that are global that 509 # we can use safely. 510 if (!defined($locals{$text}) && !defined($weak{$text})) { 511 $ref_func = $text; 512 $read_function = 0; 513 $offset = hex $1; 514 } else { 515 # if we already have a function, and this is weak, skip it 516 if (!defined($ref_func) && !defined($weak{$text}) && 517 # PPC64 can have symbols that start with .L and 518 # gcc considers these special. Don't use them! 519 $text !~ /^\.L/) { 520 $ref_func = $text; 521 $offset = hex $1; 522 } 523 } 524 } 525 # is this a call site to mcount? If so, record it to print later 526 if ($text_found && /$mcount_regex/) { 527 push(@offsets, (hex $1) + $mcount_adjust); 528 } 529} 530 531# dump out anymore offsets that may have been found 532update_funcs(); 533 534# If we did not find any mcount callers, we are done (do nothing). 535if (!$opened) { 536 exit(0); 537} 538 539close(FILE); 540 541# 542# Step 3: Compile the file that holds the list of call sites to mcount. 543# 544`$cc -o $mcount_o -c $mcount_s`; 545 546my @converts = keys %convert; 547 548# 549# Step 4: Do we have sections that started with local functions? 550# 551if ($#converts >= 0) { 552 my $globallist = ""; 553 my $locallist = ""; 554 555 foreach my $con (@converts) { 556 $globallist .= " --globalize-symbol $con"; 557 $locallist .= " --localize-symbol $con"; 558 } 559 560 my $globalobj = $dirname . "/.tmp_gl_" . $filename; 561 my $globalmix = $dirname . "/.tmp_mx_" . $filename; 562 563 # 564 # Step 5: set up each local function as a global 565 # 566 `$objcopy $globallist $inputfile $globalobj`; 567 568 # 569 # Step 6: Link the global version to our list. 570 # 571 `$ld -r $globalobj $mcount_o -o $globalmix`; 572 573 # 574 # Step 7: Convert the local functions back into local symbols 575 # 576 `$objcopy $locallist $globalmix $inputfile`; 577 578 # Remove the temp files 579 `$rm $globalobj $globalmix`; 580 581} else { 582 583 my $mix = $dirname . "/.tmp_mx_" . $filename; 584 585 # 586 # Step 8: Link the object with our list of call sites object. 587 # 588 `$ld -r $inputfile $mcount_o -o $mix`; 589 590 # 591 # Step 9: Move the result back to the original object. 592 # 593 `$mv $mix $inputfile`; 594} 595 596# Clean up the temp files 597`$rm $mcount_o $mcount_s`; 598 599exit(0); 600