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 ".text.sched" 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 .text.sched. 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 ".text.sched" 55# my_func: 56# [...] 57# call mcount (offset: 0x5) 58# [...] 59# ret 60# .globl my_func 61# other_func: 62# [...] 63# call mcount (offset: 0x1b) 64# [...] 65# 66# If we make the tmp.s the same as above, when we link together with 67# the original object, we will end up with two symbols for my_func: 68# one local, one global. After final compile, we will end up with 69# an undefined reference to my_func. 70# 71# Since local objects can reference local variables, we need to find 72# a way to make tmp.o reference the local objects of the original object 73# file after it is linked together. To do this, we convert the my_func 74# into a global symbol before linking tmp.o. Then after we link tmp.o 75# we will only have a single symbol for my_func that is global. 76# We can convert my_func back into a local symbol and we are done. 77# 78# Here are the steps we take: 79# 80# 1) Record all the local symbols by using 'nm' 81# 2) Use objdump to find all the call site offsets and sections for 82# mcount. 83# 3) Compile the list into its own object. 84# 4) Do we have to deal with local functions? If not, go to step 8. 85# 5) Make an object that converts these local functions to global symbols 86# with objcopy. 87# 6) Link together this new object with the list object. 88# 7) Convert the local functions back to local symbols and rename 89# the result as the original object. 90# End. 91# 8) Link the object with the list object. 92# 9) Move the result back to the original object. 93# End. 94# 95 96use strict; 97 98my $P = $0; 99$P =~ s@.*/@@g; 100 101my $V = '0.1'; 102 103if ($#ARGV < 6) { 104 print "usage: $P arch objdump objcopy cc ld nm rm mv inputfile\n"; 105 print "version: $V\n"; 106 exit(1); 107} 108 109my ($arch, $bits, $objdump, $objcopy, $cc, 110 $ld, $nm, $rm, $mv, $inputfile) = @ARGV; 111 112# Acceptable sections to record. 113my %text_sections = ( 114 ".text" => 1, 115 ".sched.text" => 1, 116 ".spinlock.text" => 1, 117); 118 119$objdump = "objdump" if ((length $objdump) == 0); 120$objcopy = "objcopy" if ((length $objcopy) == 0); 121$cc = "gcc" if ((length $cc) == 0); 122$ld = "ld" if ((length $ld) == 0); 123$nm = "nm" if ((length $nm) == 0); 124$rm = "rm" if ((length $rm) == 0); 125$mv = "mv" if ((length $mv) == 0); 126 127#print STDERR "running: $P '$arch' '$objdump' '$objcopy' '$cc' '$ld' " . 128# "'$nm' '$rm' '$mv' '$inputfile'\n"; 129 130my %locals; # List of local (static) functions 131my %weak; # List of weak functions 132my %convert; # List of local functions used that needs conversion 133 134my $type; 135my $nm_regex; # Find the local functions (return function) 136my $section_regex; # Find the start of a section 137my $function_regex; # Find the name of a function 138 # (return offset and func name) 139my $mcount_regex; # Find the call site to mcount (return offset) 140my $alignment; # The .align value to use for $mcount_section 141my $section_type; # Section header plus possible alignment command 142 143if ($arch eq "x86") { 144 if ($bits == 64) { 145 $arch = "x86_64"; 146 } else { 147 $arch = "i386"; 148 } 149} 150 151# 152# We base the defaults off of i386, the other archs may 153# feel free to change them in the below if statements. 154# 155$nm_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\S+)"; 156$section_regex = "Disassembly of section\\s+(\\S+):"; 157$function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:"; 158$mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount\$"; 159$section_type = '@progbits'; 160$type = ".long"; 161 162if ($arch eq "x86_64") { 163 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount([+-]0x[0-9a-zA-Z]+)?\$"; 164 $type = ".quad"; 165 $alignment = 8; 166 167 # force flags for this arch 168 $ld .= " -m elf_x86_64"; 169 $objdump .= " -M x86-64"; 170 $objcopy .= " -O elf64-x86-64"; 171 $cc .= " -m64"; 172 173} elsif ($arch eq "i386") { 174 $alignment = 4; 175 176 # force flags for this arch 177 $ld .= " -m elf_i386"; 178 $objdump .= " -M i386"; 179 $objcopy .= " -O elf32-i386"; 180 $cc .= " -m32"; 181 182} elsif ($arch eq "sh") { 183 $alignment = 2; 184 185 # force flags for this arch 186 $ld .= " -m shlelf_linux"; 187 $objcopy .= " -O elf32-sh-linux"; 188 $cc .= " -m32"; 189 190} elsif ($arch eq "powerpc") { 191 $nm_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\.?\\S+)"; 192 $function_regex = "^([0-9a-fA-F]+)\\s+<(\\.?.*?)>:"; 193 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s\\.?_mcount\$"; 194 195 if ($bits == 64) { 196 $type = ".quad"; 197 } 198 199} elsif ($arch eq "arm") { 200 $alignment = 2; 201 $section_type = '%progbits'; 202 203} else { 204 die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD"; 205} 206 207my $text_found = 0; 208my $read_function = 0; 209my $opened = 0; 210my $mcount_section = "__mcount_loc"; 211 212my $dirname; 213my $filename; 214my $prefix; 215my $ext; 216 217if ($inputfile =~ m,^(.*)/([^/]*)$,) { 218 $dirname = $1; 219 $filename = $2; 220} else { 221 $dirname = "."; 222 $filename = $inputfile; 223} 224 225if ($filename =~ m,^(.*)(\.\S),) { 226 $prefix = $1; 227 $ext = $2; 228} else { 229 $prefix = $filename; 230 $ext = ""; 231} 232 233my $mcount_s = $dirname . "/.tmp_mc_" . $prefix . ".s"; 234my $mcount_o = $dirname . "/.tmp_mc_" . $prefix . ".o"; 235 236# 237# --globalize-symbols came out in 2.17, we must test the version 238# of objcopy, and if it is less than 2.17, then we can not 239# record local functions. 240my $use_locals = 01; 241my $local_warn_once = 0; 242my $found_version = 0; 243 244open (IN, "$objcopy --version |") || die "error running $objcopy"; 245while (<IN>) { 246 if (/objcopy.*\s(\d+)\.(\d+)/) { 247 my $major = $1; 248 my $minor = $2; 249 250 $found_version = 1; 251 if ($major < 2 || 252 ($major == 2 && $minor < 17)) { 253 $use_locals = 0; 254 } 255 last; 256 } 257} 258close (IN); 259 260if (!$found_version) { 261 print STDERR "WARNING: could not find objcopy version.\n" . 262 "\tDisabling local function references.\n"; 263} 264 265 266# 267# Step 1: find all the local (static functions) and weak symbols. 268# 't' is local, 'w/W' is weak (we never use a weak function) 269# 270open (IN, "$nm $inputfile|") || die "error running $nm"; 271while (<IN>) { 272 if (/$nm_regex/) { 273 $locals{$1} = 1; 274 } elsif (/^[0-9a-fA-F]+\s+([wW])\s+(\S+)/) { 275 $weak{$2} = $1; 276 } 277} 278close(IN); 279 280my @offsets; # Array of offsets of mcount callers 281my $ref_func; # reference function to use for offsets 282my $offset = 0; # offset of ref_func to section beginning 283 284## 285# update_funcs - print out the current mcount callers 286# 287# Go through the list of offsets to callers and write them to 288# the output file in a format that can be read by an assembler. 289# 290sub update_funcs 291{ 292 return if ($#offsets < 0); 293 294 defined($ref_func) || die "No function to reference"; 295 296 # A section only had a weak function, to represent it. 297 # Unfortunately, a weak function may be overwritten by another 298 # function of the same name, making all these offsets incorrect. 299 # To be safe, we simply print a warning and bail. 300 if (defined $weak{$ref_func}) { 301 print STDERR 302 "$inputfile: WARNING: referencing weak function" . 303 " $ref_func for mcount\n"; 304 return; 305 } 306 307 # is this function static? If so, note this fact. 308 if (defined $locals{$ref_func}) { 309 310 # only use locals if objcopy supports globalize-symbols 311 if (!$use_locals) { 312 return; 313 } 314 $convert{$ref_func} = 1; 315 } 316 317 # Loop through all the mcount caller offsets and print a reference 318 # to the caller based from the ref_func. 319 for (my $i=0; $i <= $#offsets; $i++) { 320 if (!$opened) { 321 open(FILE, ">$mcount_s") || die "can't create $mcount_s\n"; 322 $opened = 1; 323 print FILE "\t.section $mcount_section,\"a\",$section_type\n"; 324 print FILE "\t.align $alignment\n" if (defined($alignment)); 325 } 326 printf FILE "\t%s %s + %d\n", $type, $ref_func, $offsets[$i] - $offset; 327 } 328} 329 330# 331# Step 2: find the sections and mcount call sites 332# 333open(IN, "$objdump -dr $inputfile|") || die "error running $objdump"; 334 335my $text; 336 337while (<IN>) { 338 # is it a section? 339 if (/$section_regex/) { 340 341 # Only record text sections that we know are safe 342 if (defined($text_sections{$1})) { 343 $read_function = 1; 344 } else { 345 $read_function = 0; 346 } 347 # print out any recorded offsets 348 update_funcs() if ($text_found); 349 350 # reset all markers and arrays 351 $text_found = 0; 352 undef($ref_func); 353 undef(@offsets); 354 355 # section found, now is this a start of a function? 356 } elsif ($read_function && /$function_regex/) { 357 $text_found = 1; 358 $offset = hex $1; 359 $text = $2; 360 361 # if this is either a local function or a weak function 362 # keep looking for functions that are global that 363 # we can use safely. 364 if (!defined($locals{$text}) && !defined($weak{$text})) { 365 $ref_func = $text; 366 $read_function = 0; 367 } else { 368 # if we already have a function, and this is weak, skip it 369 if (!defined($ref_func) || !defined($weak{$text})) { 370 $ref_func = $text; 371 } 372 } 373 } 374 375 # is this a call site to mcount? If so, record it to print later 376 if ($text_found && /$mcount_regex/) { 377 $offsets[$#offsets + 1] = hex $1; 378 } 379} 380 381# dump out anymore offsets that may have been found 382update_funcs() if ($text_found); 383 384# If we did not find any mcount callers, we are done (do nothing). 385if (!$opened) { 386 exit(0); 387} 388 389close(FILE); 390 391# 392# Step 3: Compile the file that holds the list of call sites to mcount. 393# 394`$cc -o $mcount_o -c $mcount_s`; 395 396my @converts = keys %convert; 397 398# 399# Step 4: Do we have sections that started with local functions? 400# 401if ($#converts >= 0) { 402 my $globallist = ""; 403 my $locallist = ""; 404 405 foreach my $con (@converts) { 406 $globallist .= " --globalize-symbol $con"; 407 $locallist .= " --localize-symbol $con"; 408 } 409 410 my $globalobj = $dirname . "/.tmp_gl_" . $filename; 411 my $globalmix = $dirname . "/.tmp_mx_" . $filename; 412 413 # 414 # Step 5: set up each local function as a global 415 # 416 `$objcopy $globallist $inputfile $globalobj`; 417 418 # 419 # Step 6: Link the global version to our list. 420 # 421 `$ld -r $globalobj $mcount_o -o $globalmix`; 422 423 # 424 # Step 7: Convert the local functions back into local symbols 425 # 426 `$objcopy $locallist $globalmix $inputfile`; 427 428 # Remove the temp files 429 `$rm $globalobj $globalmix`; 430 431} else { 432 433 my $mix = $dirname . "/.tmp_mx_" . $filename; 434 435 # 436 # Step 8: Link the object with our list of call sites object. 437 # 438 `$ld -r $inputfile $mcount_o -o $mix`; 439 440 # 441 # Step 9: Move the result back to the original object. 442 # 443 `$mv $mix $inputfile`; 444} 445 446# Clean up the temp files 447`$rm $mcount_o $mcount_s`; 448 449exit(0); 450