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 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.
17 # This is no easy feat. This script is called just after the original
18 # object is compiled and before it is linked.
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
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.
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.
36 # .section ".sched.text", "ax"
40 # call mcount (offset: 0x10)
44 # func2: (offset: 0x20)
50 # call mcount (offset: 0x30)
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:
57 # .section __mcount_loc
61 # We can then compile this tmp.s into tmp.o, and link it back to the original
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:
68 # .section ".sched.text", "ax"
71 # call mcount (offset: 0x10)
76 # call mcount (offset: 0x20)
78 # .section "other.section"
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.
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.
93 # Here are the steps we take:
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
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
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.
117 print "usage: $P arch endian bits objdump objcopy cc ld nm rm mv is_module inputfile\n";
118 print "version: $V\n";
122 my ($arch, $endian, $bits, $objdump, $objcopy, $cc,
123 $ld, $nm, $rm, $mv, $is_module, $inputfile) = @ARGV;
125 # This file refers to mcount and shouldn't be ftraced, so lets' ignore it
126 if ($inputfile =~ m,kernel/trace/ftrace\.o$,) {
130 # Acceptable sections to record.
131 my %text_sections = (
135 ".spinlock.text" => 1,
136 ".irqentry.text" => 1,
137 ".kprobes.text" => 1,
138 ".text.unlikely" => 1,
141 # Acceptable section-prefixes to record.
142 my %text_section_prefixes = (
146 # Note: we are nice to C-programmers here, thus we skip the '||='-idiom.
147 $objdump = 'objdump' if (!$objdump);
148 $objcopy = 'objcopy' if (!$objcopy);
149 $cc = 'gcc' if (!$cc);
150 $ld = 'ld' if (!$ld);
151 $nm = 'nm' if (!$nm);
152 $rm = 'rm' if (!$rm);
153 $mv = 'mv' if (!$mv);
155 #print STDERR "running: $P '$arch' '$objdump' '$objcopy' '$cc' '$ld' " .
156 # "'$nm' '$rm' '$mv' '$inputfile'\n";
158 my %locals; # List of local (static) functions
159 my %weak; # List of weak functions
160 my %convert; # List of local functions used that needs conversion
163 my $local_regex; # Match a local function (return function)
164 my $weak_regex; # Match a weak function (return function)
165 my $section_regex; # Find the start of a section
166 my $function_regex; # Find the name of a function
167 # (return offset and func name)
168 my $mcount_regex; # Find the call site to mcount (return offset)
169 my $mcount_adjust; # Address adjustment to mcount offset
170 my $alignment; # The .align value to use for $mcount_section
171 my $section_type; # Section header plus possible alignment command
172 my $can_use_local = 0; # If we can use local function references
174 # Shut up recordmcount if user has older objcopy
175 my $quiet_recordmcount = ".tmp_quiet_recordmcount";
176 my $print_warning = 1;
177 $print_warning = 0 if ( -f $quiet_recordmcount);
180 # check_objcopy - whether objcopy supports --globalize-symbols
182 # --globalize-symbols came out in 2.17, we must test the version
183 # of objcopy, and if it is less than 2.17, then we can not
184 # record local functions.
187 open (IN, "$objcopy --version |") or die "error running $objcopy";
189 if (/objcopy.*\s(\d+)\.(\d+)/) {
190 $can_use_local = 1 if ($1 > 2 || ($1 == 2 && $2 >= 17));
196 if (!$can_use_local && $print_warning) {
197 print STDERR "WARNING: could not find objcopy version or version " .
198 "is less than 2.17.\n" .
199 "\tLocal function references are disabled.\n";
200 open (QUIET, ">$quiet_recordmcount");
201 printf QUIET "Disables the warning from recordmcount.pl\n";
206 if ($arch =~ /(x86(_64)?)|(i386)/) {
215 # We base the defaults off of i386, the other archs may
216 # feel free to change them in the below if statements.
218 $local_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\S+)";
219 $weak_regex = "^[0-9a-fA-F]+\\s+([wW])\\s+(\\S+)";
220 $section_regex = "Disassembly of section\\s+(\\S+):";
221 $function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
222 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s(mcount|__fentry__)\$";
223 $section_type = '@progbits';
227 if ($arch eq "x86_64") {
228 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s(mcount|__fentry__)([+-]0x[0-9a-zA-Z]+)?\$";
233 # force flags for this arch
234 $ld .= " -m elf_x86_64";
235 $objdump .= " -M x86-64";
236 $objcopy .= " -O elf64-x86-64";
239 } elsif ($arch eq "i386") {
243 # force flags for this arch
244 $ld .= " -m elf_i386";
245 $objdump .= " -M i386";
246 $objcopy .= " -O elf32-i386";
249 } elsif ($arch eq "s390" && $bits == 64) {
250 if ($cc =~ /-DCC_USING_HOTPATCH/) {
251 $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*c0 04 00 00 00 00\\s*brcl\\s*0,[0-9a-f]+ <([^\+]*)>\$";
254 $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_390_(PC|PLT)32DBL\\s+_mcount\\+0x2\$";
255 $mcount_adjust = -14;
259 $ld .= " -m elf64_s390";
262 } elsif ($arch eq "sh") {
265 # force flags for this arch
266 $ld .= " -m shlelf_linux";
267 if ($endian eq "big") {
268 $objcopy .= " -O elf32-shbig-linux";
270 $objcopy .= " -O elf32-sh-linux";
273 } elsif ($arch eq "powerpc") {
274 $local_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\.?\\S+)";
275 # See comment in the sparc64 section for why we use '\w'.
276 $function_regex = "^([0-9a-fA-F]+)\\s+<(\\.?\\w*?)>:";
277 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s\\.?_mcount\$";
283 } elsif ($arch eq "arm") {
285 $section_type = '%progbits';
286 $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_ARM_(CALL|PC24|THM_CALL)" .
287 "\\s+(__gnu_mcount_nc|mcount)\$";
289 } elsif ($arch eq "arm64") {
291 $section_type = '%progbits';
292 $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_AARCH64_CALL26\\s+_mcount\$";
294 } elsif ($arch eq "ia64") {
295 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
298 if ($is_module eq "0") {
299 $cc .= " -mconstant-gp";
301 } elsif ($arch eq "sparc64") {
302 # In the objdump output there are giblets like:
303 # 0000000000000000 <igmp_net_exit-0x18>:
304 # As there's some data blobs that get emitted into the
305 # text section before the first instructions and the first
306 # real symbols. We don't want to match that, so to combat
307 # this we use '\w' so we'll match just plain symbol names,
308 # and not those that also include hex offsets inside of the
309 # '<>' brackets. Actually the generic function_regex setting
310 # could safely use this too.
311 $function_regex = "^([0-9a-fA-F]+)\\s+<(\\w*?)>:";
313 # Sparc64 calls '_mcount' instead of plain 'mcount'.
314 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
318 $ld .= " -m elf64_sparc";
320 $objcopy .= " -O elf64-sparc";
321 } elsif ($arch eq "mips") {
322 # To enable module support, we need to enable the -mlong-calls option
323 # of gcc for module, after using this option, we can not get the real
324 # offset of the calling to _mcount, but the offset of the lui
325 # instruction or the addiu one. herein, we record the address of the
326 # first one, and then we can replace this instruction by a branch
327 # instruction to jump over the profiling function to filter the
328 # indicated functions, or swith back to the lui instruction to trace
329 # them, which means dynamic tracing.
331 # c: 3c030000 lui v1,0x0
332 # c: R_MIPS_HI16 _mcount
333 # c: R_MIPS_NONE *ABS*
334 # c: R_MIPS_NONE *ABS*
335 # 10: 64630000 daddiu v1,v1,0
336 # 10: R_MIPS_LO16 _mcount
337 # 10: R_MIPS_NONE *ABS*
338 # 10: R_MIPS_NONE *ABS*
339 # 14: 03e0082d move at,ra
340 # 18: 0060f809 jalr v1
344 # 10: 03e0082d move at,ra
345 # 14: 0c000000 jal 0 <loongson_halt>
346 # 14: R_MIPS_26 _mcount
347 # 14: R_MIPS_NONE *ABS*
348 # 14: R_MIPS_NONE *ABS*
350 if ($is_module eq "0") {
351 $mcount_regex = "^\\s*([0-9a-fA-F]+): R_MIPS_26\\s+_mcount\$";
353 $mcount_regex = "^\\s*([0-9a-fA-F]+): R_MIPS_HI16\\s+_mcount\$";
355 $objdump .= " -Melf-trad".$endian."mips ";
357 if ($endian eq "big") {
359 $ld .= " -melf".$bits."btsmip";
362 $ld .= " -melf".$bits."ltsmip";
365 $cc .= " -mno-abicalls -fno-pic -mabi=" . $bits . $endian;
370 "^([0-9a-fA-F]+)\\s+<(.|[^\$]L.*?|\$[^L].*?|[^\$][^L].*?)>:";
373 } elsif ($arch eq "microblaze") {
374 # Microblaze calls '_mcount' instead of plain 'mcount'.
375 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
376 } elsif ($arch eq "blackfin") {
377 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s__mcount\$";
379 } elsif ($arch eq "tilegx" || $arch eq "tile") {
380 # Default to the newer TILE-Gx architecture if only "tile" is given.
381 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s__mcount\$";
385 die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD";
389 my $read_function = 0;
391 my $mcount_section = "__mcount_loc";
398 if ($inputfile =~ m,^(.*)/([^/]*)$,) {
403 $filename = $inputfile;
406 if ($filename =~ m,^(.*)(\.\S),) {
414 my $mcount_s = $dirname . "/.tmp_mc_" . $prefix . ".s";
415 my $mcount_o = $dirname . "/.tmp_mc_" . $prefix . ".o";
420 # Step 1: find all the local (static functions) and weak symbols.
421 # 't' is local, 'w/W' is weak
423 open (IN, "$nm $inputfile|") || die "error running $nm";
425 if (/$local_regex/) {
427 } elsif (/$weak_regex/) {
433 my @offsets; # Array of offsets of mcount callers
434 my $ref_func; # reference function to use for offsets
435 my $offset = 0; # offset of ref_func to section beginning
438 # update_funcs - print out the current mcount callers
440 # Go through the list of offsets to callers and write them to
441 # the output file in a format that can be read by an assembler.
445 return unless ($ref_func and @offsets);
447 # Sanity check on weak function. A weak function may be overwritten by
448 # another function of the same name, making all these offsets incorrect.
449 if (defined $weak{$ref_func}) {
450 die "$inputfile: ERROR: referencing weak function" .
451 " $ref_func for mcount\n";
454 # is this function static? If so, note this fact.
455 if (defined $locals{$ref_func}) {
457 # only use locals if objcopy supports globalize-symbols
458 if (!$can_use_local) {
461 $convert{$ref_func} = 1;
464 # Loop through all the mcount caller offsets and print a reference
465 # to the caller based from the ref_func.
467 open(FILE, ">$mcount_s") || die "can't create $mcount_s\n";
469 print FILE "\t.section $mcount_section,\"a\",$section_type\n";
470 print FILE "\t.align $alignment\n" if (defined($alignment));
472 foreach my $cur_offset (@offsets) {
473 printf FILE "\t%s %s + %d\n", $type, $ref_func, $cur_offset - $offset;
478 # Step 2: find the sections and mcount call sites
480 open(IN, "$objdump -hdr $inputfile|") || die "error running $objdump";
486 my $read_headers = 1;
490 if ($read_headers && /$mcount_section/) {
492 # Somehow the make process can execute this script on an
493 # object twice. If it does, we would duplicate the mcount
494 # section and it will cause the function tracer self test
495 # to fail. Check if the mcount section exists, and if it does,
498 print STDERR "ERROR: $mcount_section already in $inputfile\n" .
499 "\tThis may be an indication that your build is corrupted.\n" .
500 "\tDelete $inputfile and try again. If the same object file\n" .
501 "\tstill causes an issue, then disable CONFIG_DYNAMIC_FTRACE.\n";
506 if (/$section_regex/) {
509 # Only record text sections that we know are safe
510 $read_function = defined($text_sections{$1});
511 if (!$read_function) {
512 foreach my $prefix (keys %text_section_prefixes) {
513 if (substr($1, 0, length $prefix) eq $prefix) {
519 # print out any recorded offsets
522 # reset all markers and arrays
527 # section found, now is this a start of a function?
528 } elsif ($read_function && /$function_regex/) {
532 # if this is either a local function or a weak function
533 # keep looking for functions that are global that
535 if (!defined($locals{$text}) && !defined($weak{$text})) {
540 # if we already have a function, and this is weak, skip it
541 if (!defined($ref_func) && !defined($weak{$text}) &&
542 # PPC64 can have symbols that start with .L and
543 # gcc considers these special. Don't use them!
550 # is this a call site to mcount? If so, record it to print later
551 if ($text_found && /$mcount_regex/) {
552 push(@offsets, (hex $1) + $mcount_adjust);
556 # dump out anymore offsets that may have been found
559 # If we did not find any mcount callers, we are done (do nothing).
567 # Step 3: Compile the file that holds the list of call sites to mcount.
569 `$cc -o $mcount_o -c $mcount_s`;
571 my @converts = keys %convert;
574 # Step 4: Do we have sections that started with local functions?
576 if ($#converts >= 0) {
580 foreach my $con (@converts) {
581 $globallist .= " --globalize-symbol $con";
582 $locallist .= " --localize-symbol $con";
585 my $globalobj = $dirname . "/.tmp_gl_" . $filename;
586 my $globalmix = $dirname . "/.tmp_mx_" . $filename;
589 # Step 5: set up each local function as a global
591 `$objcopy $globallist $inputfile $globalobj`;
594 # Step 6: Link the global version to our list.
596 `$ld -r $globalobj $mcount_o -o $globalmix`;
599 # Step 7: Convert the local functions back into local symbols
601 `$objcopy $locallist $globalmix $inputfile`;
603 # Remove the temp files
604 `$rm $globalobj $globalmix`;
608 my $mix = $dirname . "/.tmp_mx_" . $filename;
611 # Step 8: Link the object with our list of call sites object.
613 `$ld -r $inputfile $mcount_o -o $mix`;
616 # Step 9: Move the result back to the original object.
618 `$mv $mix $inputfile`;
621 # Clean up the temp files
622 `$rm $mcount_o $mcount_s`;