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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
109 use strict;
110
111 my $P = $0;
112 $P =~ s@.*/@@g;
113
114 my $V = '0.1';
115
116 if ($#ARGV != 11) {
117 print "usage: $P arch endian bits objdump objcopy cc ld nm rm mv is_module inputfile\n";
118 print "version: $V\n";
119 exit(1);
120 }
121
122 my ($arch, $endian, $bits, $objdump, $objcopy, $cc,
123 $ld, $nm, $rm, $mv, $is_module, $inputfile) = @ARGV;
124
125 # This file refers to mcount and shouldn't be ftraced, so lets' ignore it
126 if ($inputfile =~ m,kernel/trace/ftrace\.o$,) {
127 exit(0);
128 }
129
130 # Acceptable sections to record.
131 my %text_sections = (
132 ".text" => 1,
133 ".init.text" => 1,
134 ".ref.text" => 1,
135 ".sched.text" => 1,
136 ".spinlock.text" => 1,
137 ".irqentry.text" => 1,
138 ".softirqentry.text" => 1,
139 ".kprobes.text" => 1,
140 ".cpuidle.text" => 1,
141 ".text.unlikely" => 1,
142 );
143
144 # Note: we are nice to C-programmers here, thus we skip the '||='-idiom.
145 $objdump = 'objdump' if (!$objdump);
146 $objcopy = 'objcopy' if (!$objcopy);
147 $cc = 'gcc' if (!$cc);
148 $ld = 'ld' if (!$ld);
149 $nm = 'nm' if (!$nm);
150 $rm = 'rm' if (!$rm);
151 $mv = 'mv' if (!$mv);
152
153 #print STDERR "running: $P '$arch' '$objdump' '$objcopy' '$cc' '$ld' " .
154 # "'$nm' '$rm' '$mv' '$inputfile'\n";
155
156 my %locals; # List of local (static) functions
157 my %weak; # List of weak functions
158 my %convert; # List of local functions used that needs conversion
159
160 my $type;
161 my $local_regex; # Match a local function (return function)
162 my $weak_regex; # Match a weak function (return function)
163 my $section_regex; # Find the start of a section
164 my $function_regex; # Find the name of a function
165 # (return offset and func name)
166 my $mcount_regex; # Find the call site to mcount (return offset)
167 my $mcount_adjust; # Address adjustment to mcount offset
168 my $alignment; # The .align value to use for $mcount_section
169 my $section_type; # Section header plus possible alignment command
170 my $can_use_local = 0; # If we can use local function references
171
172 # Shut up recordmcount if user has older objcopy
173 my $quiet_recordmcount = ".tmp_quiet_recordmcount";
174 my $print_warning = 1;
175 $print_warning = 0 if ( -f $quiet_recordmcount);
176
177 ##
178 # check_objcopy - whether objcopy supports --globalize-symbols
179 #
180 # --globalize-symbols came out in 2.17, we must test the version
181 # of objcopy, and if it is less than 2.17, then we can not
182 # record local functions.
183 sub check_objcopy
184 {
185 open (IN, "$objcopy --version |") or die "error running $objcopy";
186 while (<IN>) {
187 if (/objcopy.*\s(\d+)\.(\d+)/) {
188 $can_use_local = 1 if ($1 > 2 || ($1 == 2 && $2 >= 17));
189 last;
190 }
191 }
192 close (IN);
193
194 if (!$can_use_local && $print_warning) {
195 print STDERR "WARNING: could not find objcopy version or version " .
196 "is less than 2.17.\n" .
197 "\tLocal function references are disabled.\n";
198 open (QUIET, ">$quiet_recordmcount");
199 printf QUIET "Disables the warning from recordmcount.pl\n";
200 close QUIET;
201 }
202 }
203
204 if ($arch =~ /(x86(_64)?)|(i386)/) {
205 if ($bits == 64) {
206 $arch = "x86_64";
207 } else {
208 $arch = "i386";
209 }
210 }
211
212 #
213 # We base the defaults off of i386, the other archs may
214 # feel free to change them in the below if statements.
215 #
216 $local_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\S+)";
217 $weak_regex = "^[0-9a-fA-F]+\\s+([wW])\\s+(\\S+)";
218 $section_regex = "Disassembly of section\\s+(\\S+):";
219 $function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
220 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s(mcount|__fentry__)\$";
221 $section_type = '@progbits';
222 $mcount_adjust = 0;
223 $type = ".long";
224
225 if ($arch eq "x86_64") {
226 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s(mcount|__fentry__)([+-]0x[0-9a-zA-Z]+)?\$";
227 $type = ".quad";
228 $alignment = 8;
229 $mcount_adjust = -1;
230
231 # force flags for this arch
232 $ld .= " -m elf_x86_64";
233 $objdump .= " -M x86-64";
234 $objcopy .= " -O elf64-x86-64";
235 $cc .= " -m64";
236
237 } elsif ($arch eq "i386") {
238 $alignment = 4;
239 $mcount_adjust = -1;
240
241 # force flags for this arch
242 $ld .= " -m elf_i386";
243 $objdump .= " -M i386";
244 $objcopy .= " -O elf32-i386";
245 $cc .= " -m32";
246
247 } elsif ($arch eq "s390" && $bits == 64) {
248 if ($cc =~ /-DCC_USING_HOTPATCH/) {
249 $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*c0 04 00 00 00 00\\s*brcl\\s*0,[0-9a-f]+ <([^\+]*)>\$";
250 $mcount_adjust = 0;
251 } else {
252 $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_390_(PC|PLT)32DBL\\s+_mcount\\+0x2\$";
253 $mcount_adjust = -14;
254 }
255 $alignment = 8;
256 $type = ".quad";
257 $ld .= " -m elf64_s390";
258 $cc .= " -m64";
259
260 } elsif ($arch eq "sh") {
261 $alignment = 2;
262
263 # force flags for this arch
264 $ld .= " -m shlelf_linux";
265 $objcopy .= " -O elf32-sh-linux";
266
267 } elsif ($arch eq "powerpc") {
268 $local_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\.?\\S+)";
269 # See comment in the sparc64 section for why we use '\w'.
270 $function_regex = "^([0-9a-fA-F]+)\\s+<(\\.?\\w*?)>:";
271 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s\\.?_mcount\$";
272
273 if ($bits == 64) {
274 $type = ".quad";
275 }
276
277 } elsif ($arch eq "arm") {
278 $alignment = 2;
279 $section_type = '%progbits';
280 $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_ARM_(CALL|PC24|THM_CALL)" .
281 "\\s+(__gnu_mcount_nc|mcount)\$";
282
283 } elsif ($arch eq "arm64") {
284 $alignment = 3;
285 $section_type = '%progbits';
286 $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_AARCH64_CALL26\\s+_mcount\$";
287 $type = ".quad";
288 } elsif ($arch eq "ia64") {
289 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
290 $type = "data8";
291
292 if ($is_module eq "0") {
293 $cc .= " -mconstant-gp";
294 }
295 } elsif ($arch eq "sparc64") {
296 # In the objdump output there are giblets like:
297 # 0000000000000000 <igmp_net_exit-0x18>:
298 # As there's some data blobs that get emitted into the
299 # text section before the first instructions and the first
300 # real symbols. We don't want to match that, so to combat
301 # this we use '\w' so we'll match just plain symbol names,
302 # and not those that also include hex offsets inside of the
303 # '<>' brackets. Actually the generic function_regex setting
304 # could safely use this too.
305 $function_regex = "^([0-9a-fA-F]+)\\s+<(\\w*?)>:";
306
307 # Sparc64 calls '_mcount' instead of plain 'mcount'.
308 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
309
310 $alignment = 8;
311 $type = ".xword";
312 $ld .= " -m elf64_sparc";
313 $cc .= " -m64";
314 $objcopy .= " -O elf64-sparc";
315 } elsif ($arch eq "mips") {
316 # To enable module support, we need to enable the -mlong-calls option
317 # of gcc for module, after using this option, we can not get the real
318 # offset of the calling to _mcount, but the offset of the lui
319 # instruction or the addiu one. herein, we record the address of the
320 # first one, and then we can replace this instruction by a branch
321 # instruction to jump over the profiling function to filter the
322 # indicated functions, or switch back to the lui instruction to trace
323 # them, which means dynamic tracing.
324 #
325 # c: 3c030000 lui v1,0x0
326 # c: R_MIPS_HI16 _mcount
327 # c: R_MIPS_NONE *ABS*
328 # c: R_MIPS_NONE *ABS*
329 # 10: 64630000 daddiu v1,v1,0
330 # 10: R_MIPS_LO16 _mcount
331 # 10: R_MIPS_NONE *ABS*
332 # 10: R_MIPS_NONE *ABS*
333 # 14: 03e0082d move at,ra
334 # 18: 0060f809 jalr v1
335 #
336 # for the kernel:
337 #
338 # 10: 03e0082d move at,ra
339 # 14: 0c000000 jal 0 <loongson_halt>
340 # 14: R_MIPS_26 _mcount
341 # 14: R_MIPS_NONE *ABS*
342 # 14: R_MIPS_NONE *ABS*
343 # 18: 00020021 nop
344 if ($is_module eq "0") {
345 $mcount_regex = "^\\s*([0-9a-fA-F]+): R_MIPS_26\\s+_mcount\$";
346 } else {
347 $mcount_regex = "^\\s*([0-9a-fA-F]+): R_MIPS_HI16\\s+_mcount\$";
348 }
349 $objdump .= " -Melf-trad".$endian."mips ";
350
351 if ($endian eq "big") {
352 $endian = " -EB ";
353 $ld .= " -melf".$bits."btsmip";
354 } else {
355 $endian = " -EL ";
356 $ld .= " -melf".$bits."ltsmip";
357 }
358
359 $cc .= " -mno-abicalls -fno-pic -mabi=" . $bits . $endian;
360 $ld .= $endian;
361
362 if ($bits == 64) {
363 $function_regex =
364 "^([0-9a-fA-F]+)\\s+<(.|[^\$]L.*?|\$[^L].*?|[^\$][^L].*?)>:";
365 $type = ".dword";
366 }
367 } elsif ($arch eq "microblaze") {
368 # Microblaze calls '_mcount' instead of plain 'mcount'.
369 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
370 } elsif ($arch eq "blackfin") {
371 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s__mcount\$";
372 $mcount_adjust = -4;
373 } elsif ($arch eq "tilegx" || $arch eq "tile") {
374 # Default to the newer TILE-Gx architecture if only "tile" is given.
375 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s__mcount\$";
376 $type = ".quad";
377 $alignment = 8;
378 } else {
379 die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD";
380 }
381
382 my $text_found = 0;
383 my $read_function = 0;
384 my $opened = 0;
385 my $mcount_section = "__mcount_loc";
386
387 my $dirname;
388 my $filename;
389 my $prefix;
390 my $ext;
391
392 if ($inputfile =~ m,^(.*)/([^/]*)$,) {
393 $dirname = $1;
394 $filename = $2;
395 } else {
396 $dirname = ".";
397 $filename = $inputfile;
398 }
399
400 if ($filename =~ m,^(.*)(\.\S),) {
401 $prefix = $1;
402 $ext = $2;
403 } else {
404 $prefix = $filename;
405 $ext = "";
406 }
407
408 my $mcount_s = $dirname . "/.tmp_mc_" . $prefix . ".s";
409 my $mcount_o = $dirname . "/.tmp_mc_" . $prefix . ".o";
410
411 check_objcopy();
412
413 #
414 # Step 1: find all the local (static functions) and weak symbols.
415 # 't' is local, 'w/W' is weak
416 #
417 open (IN, "$nm $inputfile|") || die "error running $nm";
418 while (<IN>) {
419 if (/$local_regex/) {
420 $locals{$1} = 1;
421 } elsif (/$weak_regex/) {
422 $weak{$2} = $1;
423 }
424 }
425 close(IN);
426
427 my @offsets; # Array of offsets of mcount callers
428 my $ref_func; # reference function to use for offsets
429 my $offset = 0; # offset of ref_func to section beginning
430
431 ##
432 # update_funcs - print out the current mcount callers
433 #
434 # Go through the list of offsets to callers and write them to
435 # the output file in a format that can be read by an assembler.
436 #
437 sub update_funcs
438 {
439 return unless ($ref_func and @offsets);
440
441 # Sanity check on weak function. A weak function may be overwritten by
442 # another function of the same name, making all these offsets incorrect.
443 if (defined $weak{$ref_func}) {
444 die "$inputfile: ERROR: referencing weak function" .
445 " $ref_func for mcount\n";
446 }
447
448 # is this function static? If so, note this fact.
449 if (defined $locals{$ref_func}) {
450
451 # only use locals if objcopy supports globalize-symbols
452 if (!$can_use_local) {
453 return;
454 }
455 $convert{$ref_func} = 1;
456 }
457
458 # Loop through all the mcount caller offsets and print a reference
459 # to the caller based from the ref_func.
460 if (!$opened) {
461 open(FILE, ">$mcount_s") || die "can't create $mcount_s\n";
462 $opened = 1;
463 print FILE "\t.section $mcount_section,\"a\",$section_type\n";
464 print FILE "\t.align $alignment\n" if (defined($alignment));
465 }
466 foreach my $cur_offset (@offsets) {
467 printf FILE "\t%s %s + %d\n", $type, $ref_func, $cur_offset - $offset;
468 }
469 }
470
471 #
472 # Step 2: find the sections and mcount call sites
473 #
474 open(IN, "$objdump -hdr $inputfile|") || die "error running $objdump";
475
476 my $text;
477
478
479 # read headers first
480 my $read_headers = 1;
481
482 while (<IN>) {
483
484 if ($read_headers && /$mcount_section/) {
485 #
486 # Somehow the make process can execute this script on an
487 # object twice. If it does, we would duplicate the mcount
488 # section and it will cause the function tracer self test
489 # to fail. Check if the mcount section exists, and if it does,
490 # warn and exit.
491 #
492 print STDERR "ERROR: $mcount_section already in $inputfile\n" .
493 "\tThis may be an indication that your build is corrupted.\n" .
494 "\tDelete $inputfile and try again. If the same object file\n" .
495 "\tstill causes an issue, then disable CONFIG_DYNAMIC_FTRACE.\n";
496 exit(-1);
497 }
498
499 # is it a section?
500 if (/$section_regex/) {
501 $read_headers = 0;
502
503 # Only record text sections that we know are safe
504 $read_function = defined($text_sections{$1});
505 # print out any recorded offsets
506 update_funcs();
507
508 # reset all markers and arrays
509 $text_found = 0;
510 undef($ref_func);
511 undef(@offsets);
512
513 # section found, now is this a start of a function?
514 } elsif ($read_function && /$function_regex/) {
515 $text_found = 1;
516 $text = $2;
517
518 # if this is either a local function or a weak function
519 # keep looking for functions that are global that
520 # we can use safely.
521 if (!defined($locals{$text}) && !defined($weak{$text})) {
522 $ref_func = $text;
523 $read_function = 0;
524 $offset = hex $1;
525 } else {
526 # if we already have a function, and this is weak, skip it
527 if (!defined($ref_func) && !defined($weak{$text}) &&
528 # PPC64 can have symbols that start with .L and
529 # gcc considers these special. Don't use them!
530 $text !~ /^\.L/) {
531 $ref_func = $text;
532 $offset = hex $1;
533 }
534 }
535 }
536 # is this a call site to mcount? If so, record it to print later
537 if ($text_found && /$mcount_regex/) {
538 push(@offsets, (hex $1) + $mcount_adjust);
539 }
540 }
541
542 # dump out anymore offsets that may have been found
543 update_funcs();
544
545 # If we did not find any mcount callers, we are done (do nothing).
546 if (!$opened) {
547 exit(0);
548 }
549
550 close(FILE);
551
552 #
553 # Step 3: Compile the file that holds the list of call sites to mcount.
554 #
555 `$cc -o $mcount_o -c $mcount_s`;
556
557 my @converts = keys %convert;
558
559 #
560 # Step 4: Do we have sections that started with local functions?
561 #
562 if ($#converts >= 0) {
563 my $globallist = "";
564 my $locallist = "";
565
566 foreach my $con (@converts) {
567 $globallist .= " --globalize-symbol $con";
568 $locallist .= " --localize-symbol $con";
569 }
570
571 my $globalobj = $dirname . "/.tmp_gl_" . $filename;
572 my $globalmix = $dirname . "/.tmp_mx_" . $filename;
573
574 #
575 # Step 5: set up each local function as a global
576 #
577 `$objcopy $globallist $inputfile $globalobj`;
578
579 #
580 # Step 6: Link the global version to our list.
581 #
582 `$ld -r $globalobj $mcount_o -o $globalmix`;
583
584 #
585 # Step 7: Convert the local functions back into local symbols
586 #
587 `$objcopy $locallist $globalmix $inputfile`;
588
589 # Remove the temp files
590 `$rm $globalobj $globalmix`;
591
592 } else {
593
594 my $mix = $dirname . "/.tmp_mx_" . $filename;
595
596 #
597 # Step 8: Link the object with our list of call sites object.
598 #
599 `$ld -r $inputfile $mcount_o -o $mix`;
600
601 #
602 # Step 9: Move the result back to the original object.
603 #
604 `$mv $mix $inputfile`;
605 }
606
607 # Clean up the temp files
608 `$rm $mcount_o $mcount_s`;
609
610 exit(0);