tracing: do not use functions starting with .L in recordmcount.pl
[linux-2.6/linux-2.6-openrd.git] / scripts / recordmcount.pl
blob4889c44d71b5d3e5907cb886577f81aea63dab8c
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
5 # recordmcount.pl - makes a section called __mcount_loc that holds
6 # all the offsets to the calls to mcount.
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.
16 # This is no easy feat. This script is called just after the original
17 # object is compiled and before it is linked.
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.
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.
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 # [...]
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:
44 # .section __mcount_loc
45 # .quad my_func + 0x5
46 # .quad my_func + 0x1b
48 # We can then compile this tmp.s into tmp.o, and link it to the original
49 # object.
51 # But this gets hard if my_func is not globl (a static function).
52 # In such a case we have:
54 # .section ".sched.text", "ax"
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 # [...]
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.
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.
78 # Here are the steps we take:
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.
96 use strict;
98 my $P = $0;
99 $P =~ s@.*/@@g;
101 my $V = '0.1';
103 if ($#ARGV < 7) {
104 print "usage: $P arch bits objdump objcopy cc ld nm rm mv is_module inputfile\n";
105 print "version: $V\n";
106 exit(1);
109 my ($arch, $bits, $objdump, $objcopy, $cc,
110 $ld, $nm, $rm, $mv, $is_module, $inputfile) = @ARGV;
112 # This file refers to mcount and shouldn't be ftraced, so lets' ignore it
113 if ($inputfile eq "kernel/trace/ftrace.o") {
114 exit(0);
117 # Acceptable sections to record.
118 my %text_sections = (
119 ".text" => 1,
120 ".sched.text" => 1,
121 ".spinlock.text" => 1,
122 ".irqentry.text" => 1,
125 $objdump = "objdump" if ((length $objdump) == 0);
126 $objcopy = "objcopy" if ((length $objcopy) == 0);
127 $cc = "gcc" if ((length $cc) == 0);
128 $ld = "ld" if ((length $ld) == 0);
129 $nm = "nm" if ((length $nm) == 0);
130 $rm = "rm" if ((length $rm) == 0);
131 $mv = "mv" if ((length $mv) == 0);
133 #print STDERR "running: $P '$arch' '$objdump' '$objcopy' '$cc' '$ld' " .
134 # "'$nm' '$rm' '$mv' '$inputfile'\n";
136 my %locals; # List of local (static) functions
137 my %weak; # List of weak functions
138 my %convert; # List of local functions used that needs conversion
140 my $type;
141 my $nm_regex; # Find the local functions (return function)
142 my $section_regex; # Find the start of a section
143 my $function_regex; # Find the name of a function
144 # (return offset and func name)
145 my $mcount_regex; # Find the call site to mcount (return offset)
146 my $alignment; # The .align value to use for $mcount_section
147 my $section_type; # Section header plus possible alignment command
149 if ($arch eq "x86") {
150 if ($bits == 64) {
151 $arch = "x86_64";
152 } else {
153 $arch = "i386";
158 # We base the defaults off of i386, the other archs may
159 # feel free to change them in the below if statements.
161 $nm_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\S+)";
162 $section_regex = "Disassembly of section\\s+(\\S+):";
163 $function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
164 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount\$";
165 $section_type = '@progbits';
166 $type = ".long";
168 if ($arch eq "x86_64") {
169 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount([+-]0x[0-9a-zA-Z]+)?\$";
170 $type = ".quad";
171 $alignment = 8;
173 # force flags for this arch
174 $ld .= " -m elf_x86_64";
175 $objdump .= " -M x86-64";
176 $objcopy .= " -O elf64-x86-64";
177 $cc .= " -m64";
179 } elsif ($arch eq "i386") {
180 $alignment = 4;
182 # force flags for this arch
183 $ld .= " -m elf_i386";
184 $objdump .= " -M i386";
185 $objcopy .= " -O elf32-i386";
186 $cc .= " -m32";
188 } elsif ($arch eq "s390" && $bits == 32) {
189 $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_390_32\\s+_mcount\$";
190 $alignment = 4;
191 $ld .= " -m elf_s390";
192 $cc .= " -m31";
194 } elsif ($arch eq "s390" && $bits == 64) {
195 $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_390_(PC|PLT)32DBL\\s+_mcount\\+0x2\$";
196 $alignment = 8;
197 $type = ".quad";
198 $ld .= " -m elf64_s390";
199 $cc .= " -m64";
201 } elsif ($arch eq "sh") {
202 $alignment = 2;
204 # force flags for this arch
205 $ld .= " -m shlelf_linux";
206 $objcopy .= " -O elf32-sh-linux";
207 $cc .= " -m32";
209 } elsif ($arch eq "powerpc") {
210 $nm_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\.?\\S+)";
211 $function_regex = "^([0-9a-fA-F]+)\\s+<(\\.?.*?)>:";
212 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s\\.?_mcount\$";
214 if ($bits == 64) {
215 $type = ".quad";
218 } elsif ($arch eq "arm") {
219 $alignment = 2;
220 $section_type = '%progbits';
222 } elsif ($arch eq "ia64") {
223 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
224 $type = "data8";
226 if ($is_module eq "0") {
227 $cc .= " -mconstant-gp";
229 } elsif ($arch eq "sparc64") {
230 # In the objdump output there are giblets like:
231 # 0000000000000000 <igmp_net_exit-0x18>:
232 # As there's some data blobs that get emitted into the
233 # text section before the first instructions and the first
234 # real symbols. We don't want to match that, so to combat
235 # this we use '\w' so we'll match just plain symbol names,
236 # and not those that also include hex offsets inside of the
237 # '<>' brackets. Actually the generic function_regex setting
238 # could safely use this too.
239 $function_regex = "^([0-9a-fA-F]+)\\s+<(\\w*?)>:";
241 # Sparc64 calls '_mcount' instead of plain 'mcount'.
242 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
244 $alignment = 8;
245 $type = ".xword";
246 $ld .= " -m elf64_sparc";
247 $cc .= " -m64";
248 $objcopy .= " -O elf64-sparc";
249 } else {
250 die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD";
253 my $text_found = 0;
254 my $read_function = 0;
255 my $opened = 0;
256 my $mcount_section = "__mcount_loc";
258 my $dirname;
259 my $filename;
260 my $prefix;
261 my $ext;
263 if ($inputfile =~ m,^(.*)/([^/]*)$,) {
264 $dirname = $1;
265 $filename = $2;
266 } else {
267 $dirname = ".";
268 $filename = $inputfile;
271 if ($filename =~ m,^(.*)(\.\S),) {
272 $prefix = $1;
273 $ext = $2;
274 } else {
275 $prefix = $filename;
276 $ext = "";
279 my $mcount_s = $dirname . "/.tmp_mc_" . $prefix . ".s";
280 my $mcount_o = $dirname . "/.tmp_mc_" . $prefix . ".o";
283 # --globalize-symbols came out in 2.17, we must test the version
284 # of objcopy, and if it is less than 2.17, then we can not
285 # record local functions.
286 my $use_locals = 01;
287 my $local_warn_once = 0;
288 my $found_version = 0;
290 open (IN, "$objcopy --version |") || die "error running $objcopy";
291 while (<IN>) {
292 if (/objcopy.*\s(\d+)\.(\d+)/) {
293 my $major = $1;
294 my $minor = $2;
296 $found_version = 1;
297 if ($major < 2 ||
298 ($major == 2 && $minor < 17)) {
299 $use_locals = 0;
301 last;
304 close (IN);
306 if (!$found_version) {
307 print STDERR "WARNING: could not find objcopy version.\n" .
308 "\tDisabling local function references.\n";
312 # Step 1: find all the local (static functions) and weak symbols.
313 # 't' is local, 'w/W' is weak (we never use a weak function)
315 open (IN, "$nm $inputfile|") || die "error running $nm";
316 while (<IN>) {
317 if (/$nm_regex/) {
318 $locals{$1} = 1;
319 } elsif (/^[0-9a-fA-F]+\s+([wW])\s+(\S+)/) {
320 $weak{$2} = $1;
323 close(IN);
325 my @offsets; # Array of offsets of mcount callers
326 my $ref_func; # reference function to use for offsets
327 my $offset = 0; # offset of ref_func to section beginning
330 # update_funcs - print out the current mcount callers
332 # Go through the list of offsets to callers and write them to
333 # the output file in a format that can be read by an assembler.
335 sub update_funcs
337 return if ($#offsets < 0);
339 defined($ref_func) || die "No function to reference";
341 # A section only had a weak function, to represent it.
342 # Unfortunately, a weak function may be overwritten by another
343 # function of the same name, making all these offsets incorrect.
344 # To be safe, we simply print a warning and bail.
345 if (defined $weak{$ref_func}) {
346 print STDERR
347 "$inputfile: WARNING: referencing weak function" .
348 " $ref_func for mcount\n";
349 return;
352 # is this function static? If so, note this fact.
353 if (defined $locals{$ref_func}) {
355 # only use locals if objcopy supports globalize-symbols
356 if (!$use_locals) {
357 return;
359 $convert{$ref_func} = 1;
362 # Loop through all the mcount caller offsets and print a reference
363 # to the caller based from the ref_func.
364 for (my $i=0; $i <= $#offsets; $i++) {
365 if (!$opened) {
366 open(FILE, ">$mcount_s") || die "can't create $mcount_s\n";
367 $opened = 1;
368 print FILE "\t.section $mcount_section,\"a\",$section_type\n";
369 print FILE "\t.align $alignment\n" if (defined($alignment));
371 printf FILE "\t%s %s + %d\n", $type, $ref_func, $offsets[$i] - $offset;
376 # Step 2: find the sections and mcount call sites
378 open(IN, "$objdump -hdr $inputfile|") || die "error running $objdump";
380 my $text;
382 my $read_headers = 1;
384 while (<IN>) {
385 # is it a section?
386 if (/$section_regex/) {
387 $read_headers = 0;
389 # Only record text sections that we know are safe
390 if (defined($text_sections{$1})) {
391 $read_function = 1;
392 } else {
393 $read_function = 0;
395 # print out any recorded offsets
396 update_funcs() if ($text_found);
398 # reset all markers and arrays
399 $text_found = 0;
400 undef($ref_func);
401 undef(@offsets);
403 # section found, now is this a start of a function?
404 } elsif ($read_function && /$function_regex/) {
405 $text_found = 1;
406 $text = $2;
408 # if this is either a local function or a weak function
409 # keep looking for functions that are global that
410 # we can use safely.
411 if (!defined($locals{$text}) && !defined($weak{$text})) {
412 $ref_func = $text;
413 $read_function = 0;
414 $offset = hex $1;
415 } else {
416 # if we already have a function, and this is weak, skip it
417 if (!defined($ref_func) && !defined($weak{$text}) &&
418 # PPC64 can have symbols that start with .L and
419 # gcc considers these special. Don't use them!
420 $text !~ /^\.L/) {
421 $ref_func = $text;
422 $offset = hex $1;
425 } elsif ($read_headers && /$mcount_section/) {
427 # Somehow the make process can execute this script on an
428 # object twice. If it does, we would duplicate the mcount
429 # section and it will cause the function tracer self test
430 # to fail. Check if the mcount section exists, and if it does,
431 # warn and exit.
433 print STDERR "ERROR: $mcount_section already in $inputfile\n" .
434 "\tThis may be an indication that your build is corrupted.\n" .
435 "\tDelete $inputfile and try again. If the same object file\n" .
436 "\tstill causes an issue, then disable CONFIG_DYNAMIC_FTRACE.\n";
437 exit(-1);
440 # is this a call site to mcount? If so, record it to print later
441 if ($text_found && /$mcount_regex/) {
442 $offsets[$#offsets + 1] = hex $1;
446 # dump out anymore offsets that may have been found
447 update_funcs() if ($text_found);
449 # If we did not find any mcount callers, we are done (do nothing).
450 if (!$opened) {
451 exit(0);
454 close(FILE);
457 # Step 3: Compile the file that holds the list of call sites to mcount.
459 `$cc -o $mcount_o -c $mcount_s`;
461 my @converts = keys %convert;
464 # Step 4: Do we have sections that started with local functions?
466 if ($#converts >= 0) {
467 my $globallist = "";
468 my $locallist = "";
470 foreach my $con (@converts) {
471 $globallist .= " --globalize-symbol $con";
472 $locallist .= " --localize-symbol $con";
475 my $globalobj = $dirname . "/.tmp_gl_" . $filename;
476 my $globalmix = $dirname . "/.tmp_mx_" . $filename;
479 # Step 5: set up each local function as a global
481 `$objcopy $globallist $inputfile $globalobj`;
484 # Step 6: Link the global version to our list.
486 `$ld -r $globalobj $mcount_o -o $globalmix`;
489 # Step 7: Convert the local functions back into local symbols
491 `$objcopy $locallist $globalmix $inputfile`;
493 # Remove the temp files
494 `$rm $globalobj $globalmix`;
496 } else {
498 my $mix = $dirname . "/.tmp_mx_" . $filename;
501 # Step 8: Link the object with our list of call sites object.
503 `$ld -r $inputfile $mcount_o -o $mix`;
506 # Step 9: Move the result back to the original object.
508 `$mv $mix $inputfile`;
511 # Clean up the temp files
512 `$rm $mcount_o $mcount_s`;
514 exit(0);