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Linux/scripts/recordmcount.pl

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

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