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 = (
134 ".spinlock.text" => 1,
135 ".irqentry.text" => 1,
136 ".text.unlikely" => 1,
139 $objdump = "objdump" if ((length $objdump) == 0);
140 $objcopy = "objcopy" if ((length $objcopy) == 0);
141 $cc = "gcc" if ((length $cc) == 0);
142 $ld = "ld" if ((length $ld) == 0);
143 $nm = "nm" if ((length $nm) == 0);
144 $rm = "rm" if ((length $rm) == 0);
145 $mv = "mv" if ((length $mv) == 0);
147 #print STDERR "running: $P '$arch' '$objdump' '$objcopy' '$cc' '$ld' " .
148 # "'$nm' '$rm' '$mv' '$inputfile'\n";
150 my %locals; # List of local (static) functions
151 my %weak; # List of weak functions
152 my %convert; # List of local functions used that needs conversion
155 my $local_regex; # Match a local function (return function)
156 my $weak_regex; # Match a weak function (return function)
157 my $section_regex; # Find the start of a section
158 my $function_regex; # Find the name of a function
159 # (return offset and func name)
160 my $mcount_regex; # Find the call site to mcount (return offset)
161 my $alignment; # The .align value to use for $mcount_section
162 my $section_type; # Section header plus possible alignment command
163 my $can_use_local = 0; # If we can use local function references
165 # Shut up recordmcount if user has older objcopy
166 my $quiet_recordmcount = ".tmp_quiet_recordmcount";
167 my $print_warning = 1;
168 $print_warning = 0 if ( -f
$quiet_recordmcount);
171 # check_objcopy - whether objcopy supports --globalize-symbols
173 # --globalize-symbols came out in 2.17, we must test the version
174 # of objcopy, and if it is less than 2.17, then we can not
175 # record local functions.
178 open (IN
, "$objcopy --version |") or die "error running $objcopy";
180 if (/objcopy.*\s(\d+)\.(\d+)/) {
181 $can_use_local = 1 if ($1 > 2 || ($1 == 2 && $2 >= 17));
187 if (!$can_use_local && $print_warning) {
188 print STDERR
"WARNING: could not find objcopy version or version " .
189 "is less than 2.17.\n" .
190 "\tLocal function references are disabled.\n";
191 open (QUIET
, ">$quiet_recordmcount");
192 printf QUIET
"Disables the warning from recordmcount.pl\n";
197 if ($arch eq "x86") {
206 # We base the defaults off of i386, the other archs may
207 # feel free to change them in the below if statements.
209 $local_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\S+)";
210 $weak_regex = "^[0-9a-fA-F]+\\s+([wW])\\s+(\\S+)";
211 $section_regex = "Disassembly of section\\s+(\\S+):";
212 $function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
213 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount\$";
214 $section_type = '@progbits';
217 if ($arch eq "x86_64") {
218 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount([+-]0x[0-9a-zA-Z]+)?\$";
222 # force flags for this arch
223 $ld .= " -m elf_x86_64";
224 $objdump .= " -M x86-64";
225 $objcopy .= " -O elf64-x86-64";
228 } elsif ($arch eq "i386") {
231 # force flags for this arch
232 $ld .= " -m elf_i386";
233 $objdump .= " -M i386";
234 $objcopy .= " -O elf32-i386";
237 } elsif ($arch eq "s390" && $bits == 32) {
238 $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_390_32\\s+_mcount\$";
240 $ld .= " -m elf_s390";
243 } elsif ($arch eq "s390" && $bits == 64) {
244 $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_390_(PC|PLT)32DBL\\s+_mcount\\+0x2\$";
247 $ld .= " -m elf64_s390";
250 } elsif ($arch eq "sh") {
253 # force flags for this arch
254 $ld .= " -m shlelf_linux";
255 $objcopy .= " -O elf32-sh-linux";
258 } elsif ($arch eq "powerpc") {
259 $local_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\.?\\S+)";
260 $function_regex = "^([0-9a-fA-F]+)\\s+<(\\.?.*?)>:";
261 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s\\.?_mcount\$";
267 } elsif ($arch eq "arm") {
269 $section_type = '%progbits';
271 } elsif ($arch eq "ia64") {
272 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
275 if ($is_module eq "0") {
276 $cc .= " -mconstant-gp";
278 } elsif ($arch eq "sparc64") {
279 # In the objdump output there are giblets like:
280 # 0000000000000000 <igmp_net_exit-0x18>:
281 # As there's some data blobs that get emitted into the
282 # text section before the first instructions and the first
283 # real symbols. We don't want to match that, so to combat
284 # this we use '\w' so we'll match just plain symbol names,
285 # and not those that also include hex offsets inside of the
286 # '<>' brackets. Actually the generic function_regex setting
287 # could safely use this too.
288 $function_regex = "^([0-9a-fA-F]+)\\s+<(\\w*?)>:";
290 # Sparc64 calls '_mcount' instead of plain 'mcount'.
291 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
295 $ld .= " -m elf64_sparc";
297 $objcopy .= " -O elf64-sparc";
298 } elsif ($arch eq "microblaze") {
299 # Microblaze calls '_mcount' instead of plain 'mcount'.
300 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
302 die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD";
306 my $read_function = 0;
308 my $mcount_section = "__mcount_loc";
315 if ($inputfile =~ m
,^(.*)/([^/]*)$,) {
320 $filename = $inputfile;
323 if ($filename =~ m
,^(.*)(\
.\S
),) {
331 my $mcount_s = $dirname . "/.tmp_mc_" . $prefix . ".s";
332 my $mcount_o = $dirname . "/.tmp_mc_" . $prefix . ".o";
337 # Step 1: find all the local (static functions) and weak symbols.
338 # 't' is local, 'w/W' is weak
340 open (IN
, "$nm $inputfile|") || die "error running $nm";
342 if (/$local_regex/) {
344 } elsif (/$weak_regex/) {
350 my @offsets; # Array of offsets of mcount callers
351 my $ref_func; # reference function to use for offsets
352 my $offset = 0; # offset of ref_func to section beginning
355 # update_funcs - print out the current mcount callers
357 # Go through the list of offsets to callers and write them to
358 # the output file in a format that can be read by an assembler.
362 return unless ($ref_func and @offsets);
364 # Sanity check on weak function. A weak function may be overwritten by
365 # another function of the same name, making all these offsets incorrect.
366 if (defined $weak{$ref_func}) {
367 die "$inputfile: ERROR: referencing weak function" .
368 " $ref_func for mcount\n";
371 # is this function static? If so, note this fact.
372 if (defined $locals{$ref_func}) {
374 # only use locals if objcopy supports globalize-symbols
375 if (!$can_use_local) {
378 $convert{$ref_func} = 1;
381 # Loop through all the mcount caller offsets and print a reference
382 # to the caller based from the ref_func.
383 for (my $i=0; $i <= $#offsets; $i++) {
385 open(FILE
, ">$mcount_s") || die "can't create $mcount_s\n";
387 print FILE
"\t.section $mcount_section,\"a\",$section_type\n";
388 print FILE
"\t.align $alignment\n" if (defined($alignment));
390 printf FILE
"\t%s %s + %d\n", $type, $ref_func, $offsets[$i] - $offset;
395 # Step 2: find the sections and mcount call sites
397 open(IN
, "$objdump -hdr $inputfile|") || die "error running $objdump";
403 my $read_headers = 1;
407 if ($read_headers && /$mcount_section/) {
409 # Somehow the make process can execute this script on an
410 # object twice. If it does, we would duplicate the mcount
411 # section and it will cause the function tracer self test
412 # to fail. Check if the mcount section exists, and if it does,
415 print STDERR
"ERROR: $mcount_section already in $inputfile\n" .
416 "\tThis may be an indication that your build is corrupted.\n" .
417 "\tDelete $inputfile and try again. If the same object file\n" .
418 "\tstill causes an issue, then disable CONFIG_DYNAMIC_FTRACE.\n";
423 if (/$section_regex/) {
426 # Only record text sections that we know are safe
427 if (defined($text_sections{$1})) {
432 # print out any recorded offsets
435 # reset all markers and arrays
440 # section found, now is this a start of a function?
441 } elsif ($read_function && /$function_regex/) {
445 # if this is either a local function or a weak function
446 # keep looking for functions that are global that
448 if (!defined($locals{$text}) && !defined($weak{$text})) {
453 # if we already have a function, and this is weak, skip it
454 if (!defined($ref_func) && !defined($weak{$text}) &&
455 # PPC64 can have symbols that start with .L and
456 # gcc considers these special. Don't use them!
463 # is this a call site to mcount? If so, record it to print later
464 if ($text_found && /$mcount_regex/) {
465 $offsets[$#offsets + 1] = hex $1;
469 # dump out anymore offsets that may have been found
472 # If we did not find any mcount callers, we are done (do nothing).
480 # Step 3: Compile the file that holds the list of call sites to mcount.
482 `$cc -o $mcount_o -c $mcount_s`;
484 my @converts = keys %convert;
487 # Step 4: Do we have sections that started with local functions?
489 if ($#converts >= 0) {
493 foreach my $con (@converts) {
494 $globallist .= " --globalize-symbol $con";
495 $locallist .= " --localize-symbol $con";
498 my $globalobj = $dirname . "/.tmp_gl_" . $filename;
499 my $globalmix = $dirname . "/.tmp_mx_" . $filename;
502 # Step 5: set up each local function as a global
504 `$objcopy $globallist $inputfile $globalobj`;
507 # Step 6: Link the global version to our list.
509 `$ld -r $globalobj $mcount_o -o $globalmix`;
512 # Step 7: Convert the local functions back into local symbols
514 `$objcopy $locallist $globalmix $inputfile`;
516 # Remove the temp files
517 `$rm $globalobj $globalmix`;
521 my $mix = $dirname . "/.tmp_mx_" . $filename;
524 # Step 8: Link the object with our list of call sites object.
526 `$ld -r $inputfile $mcount_o -o $mix`;
529 # Step 9: Move the result back to the original object.
531 `$mv $mix $inputfile`;
534 # Clean up the temp files
535 `$rm $mcount_o $mcount_s`;