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Steven Rostedt8da38212008-08-14 15:45:07 -04001#!/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 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.
15#
16# This is no easy feat. This script is called just after the original
17# object is compiled and before it is linked.
18#
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.
23#
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.
28#
29# .section ".text.sched"
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# [...]
40#
41# Both relocation offsets for the mcounts in the above example will be
42# offset from .text.sched. If we make another file called tmp.s with:
43#
44# .section __mcount_loc
45# .quad my_func + 0x5
46# .quad my_func + 0x1b
47#
48# We can then compile this tmp.s into tmp.o, and link it to the original
49# object.
50#
51# But this gets hard if my_func is not globl (a static function).
52# In such a case we have:
53#
54# .section ".text.sched"
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# [...]
65#
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.
70#
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.
77#
78# Here are the steps we take:
79#
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.
94#
95
96use strict;
97
98my $P = $0;
99$P =~ s@.*/@@g;
100
101my $V = '0.1';
102
103if ($#ARGV < 6) {
104 print "usage: $P arch objdump objcopy cc ld nm rm mv inputfile\n";
105 print "version: $V\n";
106 exit(1);
107}
108
Steven Rostedtdce9d182008-10-23 09:32:57 -0400109my ($arch, $bits, $objdump, $objcopy, $cc,
110 $ld, $nm, $rm, $mv, $inputfile) = @ARGV;
Steven Rostedt8da38212008-08-14 15:45:07 -0400111
Steven Rostedt34698bc2008-10-23 09:32:58 -0400112# Acceptable sections to record.
113my %text_sections = (
114 ".text" => 1,
Liming Wangd144d5e2008-11-26 10:29:26 +0800115 ".sched.text" => 1,
116 ".spinlock.text" => 1,
Frederic Weisbeckera0343e82008-12-09 23:53:16 +0100117 ".irqentry.text" => 1,
Steven Rostedt34698bc2008-10-23 09:32:58 -0400118);
119
Steven Rostedt8da38212008-08-14 15:45:07 -0400120$objdump = "objdump" if ((length $objdump) == 0);
121$objcopy = "objcopy" if ((length $objcopy) == 0);
122$cc = "gcc" if ((length $cc) == 0);
123$ld = "ld" if ((length $ld) == 0);
124$nm = "nm" if ((length $nm) == 0);
125$rm = "rm" if ((length $rm) == 0);
126$mv = "mv" if ((length $mv) == 0);
127
128#print STDERR "running: $P '$arch' '$objdump' '$objcopy' '$cc' '$ld' " .
129# "'$nm' '$rm' '$mv' '$inputfile'\n";
130
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400131my %locals; # List of local (static) functions
132my %weak; # List of weak functions
133my %convert; # List of local functions used that needs conversion
Steven Rostedt8da38212008-08-14 15:45:07 -0400134
135my $type;
Steven Rostedt42e007d2008-11-20 07:16:16 -0800136my $nm_regex; # Find the local functions (return function)
Steven Rostedt8da38212008-08-14 15:45:07 -0400137my $section_regex; # Find the start of a section
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400138my $function_regex; # Find the name of a function
139 # (return offset and func name)
Steven Rostedt8da38212008-08-14 15:45:07 -0400140my $mcount_regex; # Find the call site to mcount (return offset)
Matt Fleming3a3d04a2008-11-20 21:49:52 +0000141my $alignment; # The .align value to use for $mcount_section
Jim Radforde58918a2008-11-20 19:48:39 -0800142my $section_type; # Section header plus possible alignment command
Steven Rostedt8da38212008-08-14 15:45:07 -0400143
Steven Rostedtdce9d182008-10-23 09:32:57 -0400144if ($arch eq "x86") {
145 if ($bits == 64) {
146 $arch = "x86_64";
147 } else {
148 $arch = "i386";
149 }
150}
151
Steven Rostedtc204f722008-11-20 15:07:34 -0500152#
153# We base the defaults off of i386, the other archs may
154# feel free to change them in the below if statements.
155#
156$nm_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\S+)";
157$section_regex = "Disassembly of section\\s+(\\S+):";
158$function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
159$mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount\$";
Jim Radforde58918a2008-11-20 19:48:39 -0800160$section_type = '@progbits';
Steven Rostedtc204f722008-11-20 15:07:34 -0500161$type = ".long";
162
Steven Rostedt8da38212008-08-14 15:45:07 -0400163if ($arch eq "x86_64") {
Steven Rostedt8da38212008-08-14 15:45:07 -0400164 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount([+-]0x[0-9a-zA-Z]+)?\$";
165 $type = ".quad";
Matt Fleming7d5222a2008-11-07 13:26:25 +0000166 $alignment = 8;
Steven Rostedtd74fcd12008-08-15 11:40:24 -0400167
168 # force flags for this arch
169 $ld .= " -m elf_x86_64";
170 $objdump .= " -M x86-64";
171 $objcopy .= " -O elf64-x86-64";
172 $cc .= " -m64";
173
Steven Rostedt8da38212008-08-14 15:45:07 -0400174} elsif ($arch eq "i386") {
Matt Fleming7d5222a2008-11-07 13:26:25 +0000175 $alignment = 4;
Steven Rostedtd74fcd12008-08-15 11:40:24 -0400176
177 # force flags for this arch
178 $ld .= " -m elf_i386";
179 $objdump .= " -M i386";
180 $objcopy .= " -O elf32-i386";
181 $cc .= " -m32";
182
Matt Fleming0da85c02008-11-12 20:11:47 +0900183} elsif ($arch eq "sh") {
Matt Fleming3a3d04a2008-11-20 21:49:52 +0000184 $alignment = 2;
Matt Fleming0da85c02008-11-12 20:11:47 +0900185
186 # force flags for this arch
187 $ld .= " -m shlelf_linux";
188 $objcopy .= " -O elf32-sh-linux";
189 $cc .= " -m32";
190
Steven Rostedt42e007d2008-11-20 07:16:16 -0800191} elsif ($arch eq "powerpc") {
192 $nm_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\.?\\S+)";
Steven Rostedt42e007d2008-11-20 07:16:16 -0800193 $function_regex = "^([0-9a-fA-F]+)\\s+<(\\.?.*?)>:";
194 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s\\.?_mcount\$";
Steven Rostedtc204f722008-11-20 15:07:34 -0500195
Steven Rostedt42e007d2008-11-20 07:16:16 -0800196 if ($bits == 64) {
197 $type = ".quad";
Steven Rostedt42e007d2008-11-20 07:16:16 -0800198 }
199
Jim Radforde58918a2008-11-20 19:48:39 -0800200} elsif ($arch eq "arm") {
201 $alignment = 2;
202 $section_type = '%progbits';
203
Steven Rostedt8da38212008-08-14 15:45:07 -0400204} else {
205 die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD";
206}
207
208my $text_found = 0;
209my $read_function = 0;
210my $opened = 0;
Steven Rostedt8da38212008-08-14 15:45:07 -0400211my $mcount_section = "__mcount_loc";
212
213my $dirname;
214my $filename;
215my $prefix;
216my $ext;
217
218if ($inputfile =~ m,^(.*)/([^/]*)$,) {
219 $dirname = $1;
220 $filename = $2;
221} else {
222 $dirname = ".";
223 $filename = $inputfile;
224}
225
226if ($filename =~ m,^(.*)(\.\S),) {
227 $prefix = $1;
228 $ext = $2;
229} else {
230 $prefix = $filename;
231 $ext = "";
232}
233
234my $mcount_s = $dirname . "/.tmp_mc_" . $prefix . ".s";
235my $mcount_o = $dirname . "/.tmp_mc_" . $prefix . ".o";
236
237#
Steven Rostedtf2f84582008-08-25 14:52:11 -0400238# --globalize-symbols came out in 2.17, we must test the version
239# of objcopy, and if it is less than 2.17, then we can not
240# record local functions.
241my $use_locals = 01;
242my $local_warn_once = 0;
243my $found_version = 0;
244
245open (IN, "$objcopy --version |") || die "error running $objcopy";
246while (<IN>) {
247 if (/objcopy.*\s(\d+)\.(\d+)/) {
248 my $major = $1;
249 my $minor = $2;
250
251 $found_version = 1;
252 if ($major < 2 ||
253 ($major == 2 && $minor < 17)) {
254 $use_locals = 0;
255 }
256 last;
257 }
258}
259close (IN);
260
261if (!$found_version) {
262 print STDERR "WARNING: could not find objcopy version.\n" .
263 "\tDisabling local function references.\n";
264}
265
266
267#
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400268# Step 1: find all the local (static functions) and weak symbols.
269# 't' is local, 'w/W' is weak (we never use a weak function)
Steven Rostedt8da38212008-08-14 15:45:07 -0400270#
271open (IN, "$nm $inputfile|") || die "error running $nm";
272while (<IN>) {
Steven Rostedt42e007d2008-11-20 07:16:16 -0800273 if (/$nm_regex/) {
Steven Rostedt8da38212008-08-14 15:45:07 -0400274 $locals{$1} = 1;
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400275 } elsif (/^[0-9a-fA-F]+\s+([wW])\s+(\S+)/) {
276 $weak{$2} = $1;
Steven Rostedt8da38212008-08-14 15:45:07 -0400277 }
278}
279close(IN);
280
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400281my @offsets; # Array of offsets of mcount callers
282my $ref_func; # reference function to use for offsets
283my $offset = 0; # offset of ref_func to section beginning
284
285##
286# update_funcs - print out the current mcount callers
287#
288# Go through the list of offsets to callers and write them to
289# the output file in a format that can be read by an assembler.
290#
291sub update_funcs
292{
293 return if ($#offsets < 0);
294
295 defined($ref_func) || die "No function to reference";
296
297 # A section only had a weak function, to represent it.
298 # Unfortunately, a weak function may be overwritten by another
299 # function of the same name, making all these offsets incorrect.
300 # To be safe, we simply print a warning and bail.
301 if (defined $weak{$ref_func}) {
302 print STDERR
303 "$inputfile: WARNING: referencing weak function" .
304 " $ref_func for mcount\n";
305 return;
306 }
307
308 # is this function static? If so, note this fact.
309 if (defined $locals{$ref_func}) {
Steven Rostedtf2f84582008-08-25 14:52:11 -0400310
311 # only use locals if objcopy supports globalize-symbols
312 if (!$use_locals) {
Steven Rostedtf2f84582008-08-25 14:52:11 -0400313 return;
314 }
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400315 $convert{$ref_func} = 1;
316 }
317
318 # Loop through all the mcount caller offsets and print a reference
319 # to the caller based from the ref_func.
320 for (my $i=0; $i <= $#offsets; $i++) {
321 if (!$opened) {
322 open(FILE, ">$mcount_s") || die "can't create $mcount_s\n";
323 $opened = 1;
Jim Radforde58918a2008-11-20 19:48:39 -0800324 print FILE "\t.section $mcount_section,\"a\",$section_type\n";
Steven Rostedt42e007d2008-11-20 07:16:16 -0800325 print FILE "\t.align $alignment\n" if (defined($alignment));
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400326 }
327 printf FILE "\t%s %s + %d\n", $type, $ref_func, $offsets[$i] - $offset;
328 }
329}
330
Steven Rostedt8da38212008-08-14 15:45:07 -0400331#
332# Step 2: find the sections and mcount call sites
333#
334open(IN, "$objdump -dr $inputfile|") || die "error running $objdump";
335
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400336my $text;
337
Steven Rostedt8da38212008-08-14 15:45:07 -0400338while (<IN>) {
339 # is it a section?
340 if (/$section_regex/) {
Steven Rostedt34698bc2008-10-23 09:32:58 -0400341
342 # Only record text sections that we know are safe
343 if (defined($text_sections{$1})) {
344 $read_function = 1;
345 } else {
346 $read_function = 0;
347 }
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400348 # print out any recorded offsets
349 update_funcs() if ($text_found);
350
351 # reset all markers and arrays
Steven Rostedt8da38212008-08-14 15:45:07 -0400352 $text_found = 0;
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400353 undef($ref_func);
354 undef(@offsets);
355
Steven Rostedt8da38212008-08-14 15:45:07 -0400356 # section found, now is this a start of a function?
357 } elsif ($read_function && /$function_regex/) {
Steven Rostedt8da38212008-08-14 15:45:07 -0400358 $text_found = 1;
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400359 $offset = hex $1;
360 $text = $2;
361
362 # if this is either a local function or a weak function
363 # keep looking for functions that are global that
364 # we can use safely.
365 if (!defined($locals{$text}) && !defined($weak{$text})) {
366 $ref_func = $text;
367 $read_function = 0;
368 } else {
369 # if we already have a function, and this is weak, skip it
370 if (!defined($ref_func) || !defined($weak{$text})) {
371 $ref_func = $text;
372 }
Steven Rostedt8da38212008-08-14 15:45:07 -0400373 }
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400374 }
375
376 # is this a call site to mcount? If so, record it to print later
377 if ($text_found && /$mcount_regex/) {
378 $offsets[$#offsets + 1] = hex $1;
Steven Rostedt8da38212008-08-14 15:45:07 -0400379 }
380}
381
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400382# dump out anymore offsets that may have been found
383update_funcs() if ($text_found);
384
Steven Rostedt8da38212008-08-14 15:45:07 -0400385# If we did not find any mcount callers, we are done (do nothing).
386if (!$opened) {
387 exit(0);
388}
389
390close(FILE);
391
392#
393# Step 3: Compile the file that holds the list of call sites to mcount.
394#
395`$cc -o $mcount_o -c $mcount_s`;
396
397my @converts = keys %convert;
398
399#
400# Step 4: Do we have sections that started with local functions?
401#
402if ($#converts >= 0) {
403 my $globallist = "";
404 my $locallist = "";
405
406 foreach my $con (@converts) {
407 $globallist .= " --globalize-symbol $con";
408 $locallist .= " --localize-symbol $con";
409 }
410
411 my $globalobj = $dirname . "/.tmp_gl_" . $filename;
412 my $globalmix = $dirname . "/.tmp_mx_" . $filename;
413
414 #
415 # Step 5: set up each local function as a global
416 #
417 `$objcopy $globallist $inputfile $globalobj`;
418
419 #
420 # Step 6: Link the global version to our list.
421 #
422 `$ld -r $globalobj $mcount_o -o $globalmix`;
423
424 #
425 # Step 7: Convert the local functions back into local symbols
426 #
427 `$objcopy $locallist $globalmix $inputfile`;
428
429 # Remove the temp files
430 `$rm $globalobj $globalmix`;
431
432} else {
433
434 my $mix = $dirname . "/.tmp_mx_" . $filename;
435
436 #
437 # Step 8: Link the object with our list of call sites object.
438 #
439 `$ld -r $inputfile $mcount_o -o $mix`;
440
441 #
442 # Step 9: Move the result back to the original object.
443 #
444 `$mv $mix $inputfile`;
445}
446
447# Clean up the temp files
448`$rm $mcount_o $mcount_s`;
449
450exit(0);