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 is a section in vmlinux called 10# __mcount_loc that contains a list of pointers to all the 11# call sites in the kernel that call mcount. Later on boot up, the kernel 12# will read this list, save the locations and turn them into nops. 13# When tracing or profiling is later enabled, these locations will then 14# be converted back to pointers to some function. 15# 16# This is no easy feat. This script is called just after the original 17# object is compiled and before it is linked. 18# 19# The references to the call sites are offsets from the section of text 20# that the call site is in. Hence, all functions in a section that 21# has a call site to mcount, will have the offset from the beginning of 22# the section and not the beginning of the function. 23# 24# The trick is to find a way to record the beginning of the section. 25# The way we do this is to look at the first function in the section 26# which will also be the location of that section after final link. 27# e.g. 28# 29# .section ".sched.text", "ax" 30# .globl my_func 31# my_func: 32# [...] 33# call mcount (offset: 0x5) 34# [...] 35# ret 36# other_func: 37# [...] 38# call mcount (offset: 0x1b) 39# [...] 40# 41# Both relocation offsets for the mcounts in the above example will be 42# offset from .sched.text. If we make another file called tmp.s with: 43# 44# .section __mcount_loc 45# .quad my_func + 0x5 46# .quad my_func + 0x1b 47# 48# We can then compile this tmp.s into tmp.o, and link it to the original 49# object. 50# 51# But this gets hard if my_func is not globl (a static function). 52# In such a case we have: 53# 54# .section ".sched.text", "ax" 55# my_func: 56# [...] 57# call mcount (offset: 0x5) 58# [...] 59# ret 60# other_func: 61# [...] 62# call mcount (offset: 0x1b) 63# [...] 64# 65# If we make the tmp.s the same as above, when we link together with 66# the original object, we will end up with two symbols for my_func: 67# one local, one global. After final compile, we will end up with 68# an undefined reference to my_func. 69# 70# Since local objects can reference local variables, we need to find 71# a way to make tmp.o reference the local objects of the original object 72# file after it is linked together. To do this, we convert the my_func 73# into a global symbol before linking tmp.o. Then after we link tmp.o 74# we will only have a single symbol for my_func that is global. 75# We can convert my_func back into a local symbol and we are done. 76# 77# Here are the steps we take: 78# 79# 1) Record all the local symbols by using 'nm' 80# 2) Use objdump to find all the call site offsets and sections for 81# mcount. 82# 3) Compile the list into its own object. 83# 4) Do we have to deal with local functions? If not, go to step 8. 84# 5) Make an object that converts these local functions to global symbols 85# with objcopy. 86# 6) Link together this new object with the list object. 87# 7) Convert the local functions back to local symbols and rename 88# the result as the original object. 89# End. 90# 8) Link the object with the list object. 91# 9) Move the result back to the original object. 92# End. 93# 94 95use strict; 96 97my $P = $0; 98$P =~ s@.*/@@g; 99 100my $V = '0.1'; 101 102if ($#ARGV < 7) { 103 print "usage: $P arch bits objdump objcopy cc ld nm rm mv is_module inputfile\n"; 104 print "version: $V\n"; 105 exit(1); 106} 107 108my ($arch, $bits, $objdump, $objcopy, $cc, 109 $ld, $nm, $rm, $mv, $is_module, $inputfile) = @ARGV; 110 111# This file refers to mcount and shouldn't be ftraced, so lets' ignore it 112if ($inputfile eq "kernel/trace/ftrace.o") { 113 exit(0); 114} 115 116# Acceptable sections to record. 117my %text_sections = ( 118 ".text" => 1, 119 ".sched.text" => 1, 120 ".spinlock.text" => 1, 121 ".irqentry.text" => 1, 122); 123 124$objdump = "objdump" if ((length $objdump) == 0); 125$objcopy = "objcopy" if ((length $objcopy) == 0); 126$cc = "gcc" if ((length $cc) == 0); 127$ld = "ld" if ((length $ld) == 0); 128$nm = "nm" if ((length $nm) == 0); 129$rm = "rm" if ((length $rm) == 0); 130$mv = "mv" if ((length $mv) == 0); 131 132#print STDERR "running: $P '$arch' '$objdump' '$objcopy' '$cc' '$ld' " . 133# "'$nm' '$rm' '$mv' '$inputfile'\n"; 134 135my %locals; # List of local (static) functions 136my %weak; # List of weak functions 137my %convert; # List of local functions used that needs conversion 138 139my $type; 140my $nm_regex; # Find the local functions (return function) 141my $section_regex; # Find the start of a section 142my $function_regex; # Find the name of a function 143 # (return offset and func name) 144my $mcount_regex; # Find the call site to mcount (return offset) 145my $alignment; # The .align value to use for $mcount_section 146my $section_type; # Section header plus possible alignment command 147 148if ($arch eq "x86") { 149 if ($bits == 64) { 150 $arch = "x86_64"; 151 } else { 152 $arch = "i386"; 153 } 154} 155 156# 157# We base the defaults off of i386, the other archs may 158# feel free to change them in the below if statements. 159# 160$nm_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\S+)"; 161$section_regex = "Disassembly of section\\s+(\\S+):"; 162$function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:"; 163$mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount\$"; 164$section_type = '@progbits'; 165$type = ".long"; 166 167if ($arch eq "x86_64") { 168 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount([+-]0x[0-9a-zA-Z]+)?\$"; 169 $type = ".quad"; 170 $alignment = 8; 171 172 # force flags for this arch 173 $ld .= " -m elf_x86_64"; 174 $objdump .= " -M x86-64"; 175 $objcopy .= " -O elf64-x86-64"; 176 $cc .= " -m64"; 177 178} elsif ($arch eq "i386") { 179 $alignment = 4; 180 181 # force flags for this arch 182 $ld .= " -m elf_i386"; 183 $objdump .= " -M i386"; 184 $objcopy .= " -O elf32-i386"; 185 $cc .= " -m32"; 186 187} elsif ($arch eq "s390" && $bits == 32) { 188 $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_390_32\\s+_mcount\$"; 189 $alignment = 4; 190 $ld .= " -m elf_s390"; 191 $cc .= " -m31"; 192 193} elsif ($arch eq "s390" && $bits == 64) { 194 $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_390_(PC|PLT)32DBL\\s+_mcount\\+0x2\$"; 195 $alignment = 8; 196 $type = ".quad"; 197 $ld .= " -m elf64_s390"; 198 $cc .= " -m64"; 199 200} elsif ($arch eq "sh") { 201 $alignment = 2; 202 203 # force flags for this arch 204 $ld .= " -m shlelf_linux"; 205 $objcopy .= " -O elf32-sh-linux"; 206 $cc .= " -m32"; 207 208} elsif ($arch eq "powerpc") { 209 $nm_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\.?\\S+)"; 210 $function_regex = "^([0-9a-fA-F]+)\\s+<(\\.?.*?)>:"; 211 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s\\.?_mcount\$"; 212 213 if ($bits == 64) { 214 $type = ".quad"; 215 } 216 217} elsif ($arch eq "arm") { 218 $alignment = 2; 219 $section_type = '%progbits'; 220 221} elsif ($arch eq "ia64") { 222 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$"; 223 $type = "data8"; 224 225 if ($is_module eq "0") { 226 $cc .= " -mconstant-gp"; 227 } 228} elsif ($arch eq "sparc64") { 229 # In the objdump output there are giblets like: 230 # 0000000000000000 <igmp_net_exit-0x18>: 231 # As there's some data blobs that get emitted into the 232 # text section before the first instructions and the first 233 # real symbols. We don't want to match that, so to combat 234 # this we use '\w' so we'll match just plain symbol names, 235 # and not those that also include hex offsets inside of the 236 # '<>' brackets. Actually the generic function_regex setting 237 # could safely use this too. 238 $function_regex = "^([0-9a-fA-F]+)\\s+<(\\w*?)>:"; 239 240 # Sparc64 calls '_mcount' instead of plain 'mcount'. 241 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$"; 242 243 $alignment = 8; 244 $type = ".xword"; 245 $ld .= " -m elf64_sparc"; 246 $cc .= " -m64"; 247 $objcopy .= " -O elf64-sparc"; 248} else { 249 die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD"; 250} 251 252my $text_found = 0; 253my $read_function = 0; 254my $opened = 0; 255my $mcount_section = "__mcount_loc"; 256 257my $dirname; 258my $filename; 259my $prefix; 260my $ext; 261 262if ($inputfile =~ m,^(.*)/([^/]*)$,) { 263 $dirname = $1; 264 $filename = $2; 265} else { 266 $dirname = "."; 267 $filename = $inputfile; 268} 269 270if ($filename =~ m,^(.*)(\.\S),) { 271 $prefix = $1; 272 $ext = $2; 273} else { 274 $prefix = $filename; 275 $ext = ""; 276} 277 278my $mcount_s = $dirname . "/.tmp_mc_" . $prefix . ".s"; 279my $mcount_o = $dirname . "/.tmp_mc_" . $prefix . ".o"; 280 281# 282# --globalize-symbols came out in 2.17, we must test the version 283# of objcopy, and if it is less than 2.17, then we can not 284# record local functions. 285my $use_locals = 01; 286my $local_warn_once = 0; 287my $found_version = 0; 288 289open (IN, "$objcopy --version |") || die "error running $objcopy"; 290while (<IN>) { 291 if (/objcopy.*\s(\d+)\.(\d+)/) { 292 my $major = $1; 293 my $minor = $2; 294 295 $found_version = 1; 296 if ($major < 2 || 297 ($major == 2 && $minor < 17)) { 298 $use_locals = 0; 299 } 300 last; 301 } 302} 303close (IN); 304 305if (!$found_version) { 306 print STDERR "WARNING: could not find objcopy version.\n" . 307 "\tDisabling local function references.\n"; 308} 309 310# 311# Step 1: find all the local (static functions) and weak symbols. 312# 't' is local, 'w/W' is weak (we never use a weak function) 313# 314open (IN, "$nm $inputfile|") || die "error running $nm"; 315while (<IN>) { 316 if (/$nm_regex/) { 317 $locals{$1} = 1; 318 } elsif (/^[0-9a-fA-F]+\s+([wW])\s+(\S+)/) { 319 $weak{$2} = $1; 320 } 321} 322close(IN); 323 324my @offsets; # Array of offsets of mcount callers 325my $ref_func; # reference function to use for offsets 326my $offset = 0; # offset of ref_func to section beginning 327 328## 329# update_funcs - print out the current mcount callers 330# 331# Go through the list of offsets to callers and write them to 332# the output file in a format that can be read by an assembler. 333# 334sub update_funcs 335{ 336 return if ($#offsets < 0); 337 338 defined($ref_func) || die "No function to reference"; 339 340 # A section only had a weak function, to represent it. 341 # Unfortunately, a weak function may be overwritten by another 342 # function of the same name, making all these offsets incorrect. 343 # To be safe, we simply print a warning and bail. 344 if (defined $weak{$ref_func}) { 345 print STDERR 346 "$inputfile: WARNING: referencing weak function" . 347 " $ref_func for mcount\n"; 348 return; 349 } 350 351 # is this function static? If so, note this fact. 352 if (defined $locals{$ref_func}) { 353 354 # only use locals if objcopy supports globalize-symbols 355 if (!$use_locals) { 356 return; 357 } 358 $convert{$ref_func} = 1; 359 } 360 361 # Loop through all the mcount caller offsets and print a reference 362 # to the caller based from the ref_func. 363 for (my $i=0; $i <= $#offsets; $i++) { 364 if (!$opened) { 365 open(FILE, ">$mcount_s") || die "can't create $mcount_s\n"; 366 $opened = 1; 367 print FILE "\t.section $mcount_section,\"a\",$section_type\n"; 368 print FILE "\t.align $alignment\n" if (defined($alignment)); 369 } 370 printf FILE "\t%s %s + %d\n", $type, $ref_func, $offsets[$i] - $offset; 371 } 372} 373 374# 375# Step 2: find the sections and mcount call sites 376# 377open(IN, "$objdump -hdr $inputfile|") || die "error running $objdump"; 378 379my $text; 380 381my $read_headers = 1; 382 383while (<IN>) { 384 # is it a section? 385 if (/$section_regex/) { 386 $read_headers = 0; 387 388 # Only record text sections that we know are safe 389 if (defined($text_sections{$1})) { 390 $read_function = 1; 391 } else { 392 $read_function = 0; 393 } 394 # print out any recorded offsets 395 update_funcs() if (defined($ref_func)); 396 397 # reset all markers and arrays 398 $text_found = 0; 399 undef($ref_func); 400 undef(@offsets); 401 402 # section found, now is this a start of a function? 403 } elsif ($read_function && /$function_regex/) { 404 $text_found = 1; 405 $text = $2; 406 407 # if this is either a local function or a weak function 408 # keep looking for functions that are global that 409 # we can use safely. 410 if (!defined($locals{$text}) && !defined($weak{$text})) { 411 $ref_func = $text; 412 $read_function = 0; 413 $offset = hex $1; 414 } else { 415 # if we already have a function, and this is weak, skip it 416 if (!defined($ref_func) && !defined($weak{$text}) && 417 # PPC64 can have symbols that start with .L and 418 # gcc considers these special. Don't use them! 419 $text !~ /^\.L/) { 420 $ref_func = $text; 421 $offset = hex $1; 422 } 423 } 424 } elsif ($read_headers && /$mcount_section/) { 425 # 426 # Somehow the make process can execute this script on an 427 # object twice. If it does, we would duplicate the mcount 428 # section and it will cause the function tracer self test 429 # to fail. Check if the mcount section exists, and if it does, 430 # warn and exit. 431 # 432 print STDERR "ERROR: $mcount_section already in $inputfile\n" . 433 "\tThis may be an indication that your build is corrupted.\n" . 434 "\tDelete $inputfile and try again. If the same object file\n" . 435 "\tstill causes an issue, then disable CONFIG_DYNAMIC_FTRACE.\n"; 436 exit(-1); 437 } 438 439 # is this a call site to mcount? If so, record it to print later 440 if ($text_found && /$mcount_regex/) { 441 $offsets[$#offsets + 1] = hex $1; 442 } 443} 444 445# dump out anymore offsets that may have been found 446update_funcs() if (defined($ref_func)); 447 448# If we did not find any mcount callers, we are done (do nothing). 449if (!$opened) { 450 exit(0); 451} 452 453close(FILE); 454 455# 456# Step 3: Compile the file that holds the list of call sites to mcount. 457# 458`$cc -o $mcount_o -c $mcount_s`; 459 460my @converts = keys %convert; 461 462# 463# Step 4: Do we have sections that started with local functions? 464# 465if ($#converts >= 0) { 466 my $globallist = ""; 467 my $locallist = ""; 468 469 foreach my $con (@converts) { 470 $globallist .= " --globalize-symbol $con"; 471 $locallist .= " --localize-symbol $con"; 472 } 473 474 my $globalobj = $dirname . "/.tmp_gl_" . $filename; 475 my $globalmix = $dirname . "/.tmp_mx_" . $filename; 476 477 # 478 # Step 5: set up each local function as a global 479 # 480 `$objcopy $globallist $inputfile $globalobj`; 481 482 # 483 # Step 6: Link the global version to our list. 484 # 485 `$ld -r $globalobj $mcount_o -o $globalmix`; 486 487 # 488 # Step 7: Convert the local functions back into local symbols 489 # 490 `$objcopy $locallist $globalmix $inputfile`; 491 492 # Remove the temp files 493 `$rm $globalobj $globalmix`; 494 495} else { 496 497 my $mix = $dirname . "/.tmp_mx_" . $filename; 498 499 # 500 # Step 8: Link the object with our list of call sites object. 501 # 502 `$ld -r $inputfile $mcount_o -o $mix`; 503 504 # 505 # Step 9: Move the result back to the original object. 506 # 507 `$mv $mix $inputfile`; 508} 509 510# Clean up the temp files 511`$rm $mcount_o $mcount_s`; 512 513exit(0); 514