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 != 10) { 117 print "usage: $P arch bits objdump objcopy cc ld nm rm mv is_module inputfile\n"; 118 print "version: $V\n"; 119 exit(1); 120} 121 122my ($arch, $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$,) { 127 exit(0); 128} 129 130# Acceptable sections to record. 131my %text_sections = ( 132 ".text" => 1, 133 ".sched.text" => 1, 134 ".spinlock.text" => 1, 135 ".irqentry.text" => 1, 136 ".text.unlikely" => 1, 137); 138 139$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 150my %locals; # List of local (static) functions 151my %weak; # List of weak functions 152my %convert; # List of local functions used that needs conversion 153 154my $type; 155my $local_regex; # Match a local function (return function) 156my $weak_regex; # Match a weak function (return function) 157my $section_regex; # Find the start of a section 158my $function_regex; # Find the name of a function 159 # (return offset and func name) 160my $mcount_regex; # Find the call site to mcount (return offset) 161my $alignment; # The .align value to use for $mcount_section 162my $section_type; # Section header plus possible alignment command 163my $can_use_local = 0; # If we can use local function references 164 165# Shut up recordmcount if user has older objcopy 166my $quiet_recordmcount = ".tmp_quiet_recordmcount"; 167my $print_warning = 1; 168$print_warning = 0 if ( -f $quiet_recordmcount); 169 170## 171# check_objcopy - whether objcopy supports --globalize-symbols 172# 173# --globalize-symbols came out in 2.17, we must test the version 174# of objcopy, and if it is less than 2.17, then we can not 175# record local functions. 176sub check_objcopy 177{ 178 open (IN, "$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 197if ($arch eq "x86") { 198 if ($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 217if ($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} else { 299 die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD"; 300} 301 302my $text_found = 0; 303my $read_function = 0; 304my $opened = 0; 305my $mcount_section = "__mcount_loc"; 306 307my $dirname; 308my $filename; 309my $prefix; 310my $ext; 311 312if ($inputfile =~ m,^(.*)/([^/]*)$,) { 313 $dirname = $1; 314 $filename = $2; 315} else { 316 $dirname = "."; 317 $filename = $inputfile; 318} 319 320if ($filename =~ m,^(.*)(\.\S),) { 321 $prefix = $1; 322 $ext = $2; 323} else { 324 $prefix = $filename; 325 $ext = ""; 326} 327 328my $mcount_s = $dirname . "/.tmp_mc_" . $prefix . ".s"; 329my $mcount_o = $dirname . "/.tmp_mc_" . $prefix . ".o"; 330 331check_objcopy(); 332 333# 334# Step 1: find all the local (static functions) and weak symbols. 335# 't' is local, 'w/W' is weak 336# 337open (IN, "$nm $inputfile|") || die "error running $nm"; 338while (<IN>) { 339 if (/$local_regex/) { 340 $locals{$1} = 1; 341 } elsif (/$weak_regex/) { 342 $weak{$2} = $1; 343 } 344} 345close(IN); 346 347my @offsets; # Array of offsets of mcount callers 348my $ref_func; # reference function to use for offsets 349my $offset = 0; # offset of ref_func to section beginning 350 351## 352# update_funcs - print out the current mcount callers 353# 354# Go through the list of offsets to callers and write them to 355# the output file in a format that can be read by an assembler. 356# 357sub update_funcs 358{ 359 return unless ($ref_func and @offsets); 360 361 # Sanity check on weak function. A weak function may be overwritten by 362 # another function of the same name, making all these offsets incorrect. 363 if (defined $weak{$ref_func}) { 364 die "$inputfile: ERROR: referencing weak function" . 365 " $ref_func for mcount\n"; 366 } 367 368 # is this function static? If so, note this fact. 369 if (defined $locals{$ref_func}) { 370 371 # only use locals if objcopy supports globalize-symbols 372 if (!$can_use_local) { 373 return; 374 } 375 $convert{$ref_func} = 1; 376 } 377 378 # Loop through all the mcount caller offsets and print a reference 379 # to the caller based from the ref_func. 380 for (my $i=0; $i <= $#offsets; $i++) { 381 if (!$opened) { 382 open(FILE, ">$mcount_s") || die "can't create $mcount_s\n"; 383 $opened = 1; 384 print FILE "\t.section $mcount_section,\"a\",$section_type\n"; 385 print FILE "\t.align $alignment\n" if (defined($alignment)); 386 } 387 printf FILE "\t%s %s + %d\n", $type, $ref_func, $offsets[$i] - $offset; 388 } 389} 390 391# 392# Step 2: find the sections and mcount call sites 393# 394open(IN, "$objdump -hdr $inputfile|") || die "error running $objdump"; 395 396my $text; 397 398 399# read headers first 400my $read_headers = 1; 401 402while (<IN>) { 403 404 if ($read_headers && /$mcount_section/) { 405 # 406 # Somehow the make process can execute this script on an 407 # object twice. If it does, we would duplicate the mcount 408 # section and it will cause the function tracer self test 409 # to fail. Check if the mcount section exists, and if it does, 410 # warn and exit. 411 # 412 print STDERR "ERROR: $mcount_section already in $inputfile\n" . 413 "\tThis may be an indication that your build is corrupted.\n" . 414 "\tDelete $inputfile and try again. If the same object file\n" . 415 "\tstill causes an issue, then disable CONFIG_DYNAMIC_FTRACE.\n"; 416 exit(-1); 417 } 418 419 # is it a section? 420 if (/$section_regex/) { 421 $read_headers = 0; 422 423 # Only record text sections that we know are safe 424 if (defined($text_sections{$1})) { 425 $read_function = 1; 426 } else { 427 $read_function = 0; 428 } 429 # print out any recorded offsets 430 update_funcs(); 431 432 # reset all markers and arrays 433 $text_found = 0; 434 undef($ref_func); 435 undef(@offsets); 436 437 # section found, now is this a start of a function? 438 } elsif ($read_function && /$function_regex/) { 439 $text_found = 1; 440 $text = $2; 441 442 # if this is either a local function or a weak function 443 # keep looking for functions that are global that 444 # we can use safely. 445 if (!defined($locals{$text}) && !defined($weak{$text})) { 446 $ref_func = $text; 447 $read_function = 0; 448 $offset = hex $1; 449 } else { 450 # if we already have a function, and this is weak, skip it 451 if (!defined($ref_func) && !defined($weak{$text}) && 452 # PPC64 can have symbols that start with .L and 453 # gcc considers these special. Don't use them! 454 $text !~ /^\.L/) { 455 $ref_func = $text; 456 $offset = hex $1; 457 } 458 } 459 } 460 # is this a call site to mcount? If so, record it to print later 461 if ($text_found && /$mcount_regex/) { 462 $offsets[$#offsets + 1] = hex $1; 463 } 464} 465 466# dump out anymore offsets that may have been found 467update_funcs(); 468 469# If we did not find any mcount callers, we are done (do nothing). 470if (!$opened) { 471 exit(0); 472} 473 474close(FILE); 475 476# 477# Step 3: Compile the file that holds the list of call sites to mcount. 478# 479`$cc -o $mcount_o -c $mcount_s`; 480 481my @converts = keys %convert; 482 483# 484# Step 4: Do we have sections that started with local functions? 485# 486if ($#converts >= 0) { 487 my $globallist = ""; 488 my $locallist = ""; 489 490 foreach my $con (@converts) { 491 $globallist .= " --globalize-symbol $con"; 492 $locallist .= " --localize-symbol $con"; 493 } 494 495 my $globalobj = $dirname . "/.tmp_gl_" . $filename; 496 my $globalmix = $dirname . "/.tmp_mx_" . $filename; 497 498 # 499 # Step 5: set up each local function as a global 500 # 501 `$objcopy $globallist $inputfile $globalobj`; 502 503 # 504 # Step 6: Link the global version to our list. 505 # 506 `$ld -r $globalobj $mcount_o -o $globalmix`; 507 508 # 509 # Step 7: Convert the local functions back into local symbols 510 # 511 `$objcopy $locallist $globalmix $inputfile`; 512 513 # Remove the temp files 514 `$rm $globalobj $globalmix`; 515 516} else { 517 518 my $mix = $dirname . "/.tmp_mx_" . $filename; 519 520 # 521 # Step 8: Link the object with our list of call sites object. 522 # 523 `$ld -r $inputfile $mcount_o -o $mix`; 524 525 # 526 # Step 9: Move the result back to the original object. 527 # 528 `$mv $mix $inputfile`; 529} 530 531# Clean up the temp files 532`$rm $mcount_o $mcount_s`; 533 534exit(0); 535