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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 $V = '0.1';
102
Shaohua Li18c167f2009-01-12 10:00:51 +0800103if ($#ARGV < 7) {
104 print "usage: $P arch objdump objcopy cc ld nm rm mv is_module inputfile\n";
Steven Rostedt8da38212008-08-14 15:45:07 -0400105 print "version: $V\n";
106 exit(1);
107}
108
Steven Rostedtdce9d182008-10-23 09:32:57 -0400109my ($arch, $bits, $objdump, $objcopy, $cc,
Shaohua Li18c167f2009-01-12 10:00:51 +0800110 $ld, $nm, $rm, $mv, $is_module, $inputfile) = @ARGV;
Steven Rostedt8da38212008-08-14 15:45:07 -0400111
Shaohua Li25aac9d2009-01-09 11:29:40 +0800112# This file refers to mcount and shouldn't be ftraced, so lets' ignore it
113if ($inputfile eq "kernel/trace/ftrace.o") {
114 exit(0);
115}
116
Steven Rostedt34698bc2008-10-23 09:32:58 -0400117# Acceptable sections to record.
118my %text_sections = (
119 ".text" => 1,
Liming Wangd144d5e2008-11-26 10:29:26 +0800120 ".sched.text" => 1,
121 ".spinlock.text" => 1,
Frederic Weisbeckera0343e82008-12-09 23:53:16 +0100122 ".irqentry.text" => 1,
Steven Rostedt34698bc2008-10-23 09:32:58 -0400123);
124
Steven Rostedt8da38212008-08-14 15:45:07 -0400125$objdump = "objdump" if ((length $objdump) == 0);
126$objcopy = "objcopy" if ((length $objcopy) == 0);
127$cc = "gcc" if ((length $cc) == 0);
128$ld = "ld" if ((length $ld) == 0);
129$nm = "nm" if ((length $nm) == 0);
130$rm = "rm" if ((length $rm) == 0);
131$mv = "mv" if ((length $mv) == 0);
132
133#print STDERR "running: $P '$arch' '$objdump' '$objcopy' '$cc' '$ld' " .
134# "'$nm' '$rm' '$mv' '$inputfile'\n";
135
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400136my %locals; # List of local (static) functions
137my %weak; # List of weak functions
138my %convert; # List of local functions used that needs conversion
Steven Rostedt8da38212008-08-14 15:45:07 -0400139
140my $type;
Steven Rostedt42e007d2008-11-20 07:16:16 -0800141my $nm_regex; # Find the local functions (return function)
Steven Rostedt8da38212008-08-14 15:45:07 -0400142my $section_regex; # Find the start of a section
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400143my $function_regex; # Find the name of a function
144 # (return offset and func name)
Steven Rostedt8da38212008-08-14 15:45:07 -0400145my $mcount_regex; # Find the call site to mcount (return offset)
Matt Fleming3a3d04a2008-11-20 21:49:52 +0000146my $alignment; # The .align value to use for $mcount_section
Jim Radforde58918a2008-11-20 19:48:39 -0800147my $section_type; # Section header plus possible alignment command
Steven Rostedt8da38212008-08-14 15:45:07 -0400148
Steven Rostedtdce9d182008-10-23 09:32:57 -0400149if ($arch eq "x86") {
150 if ($bits == 64) {
151 $arch = "x86_64";
152 } else {
153 $arch = "i386";
154 }
155}
156
Steven Rostedtc204f722008-11-20 15:07:34 -0500157#
158# We base the defaults off of i386, the other archs may
159# feel free to change them in the below if statements.
160#
161$nm_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\S+)";
162$section_regex = "Disassembly of section\\s+(\\S+):";
163$function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
164$mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount\$";
Jim Radforde58918a2008-11-20 19:48:39 -0800165$section_type = '@progbits';
Steven Rostedtc204f722008-11-20 15:07:34 -0500166$type = ".long";
167
Steven Rostedt8da38212008-08-14 15:45:07 -0400168if ($arch eq "x86_64") {
Steven Rostedt8da38212008-08-14 15:45:07 -0400169 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount([+-]0x[0-9a-zA-Z]+)?\$";
170 $type = ".quad";
Matt Fleming7d5222a2008-11-07 13:26:25 +0000171 $alignment = 8;
Steven Rostedtd74fcd12008-08-15 11:40:24 -0400172
173 # force flags for this arch
174 $ld .= " -m elf_x86_64";
175 $objdump .= " -M x86-64";
176 $objcopy .= " -O elf64-x86-64";
177 $cc .= " -m64";
178
Steven Rostedt8da38212008-08-14 15:45:07 -0400179} elsif ($arch eq "i386") {
Matt Fleming7d5222a2008-11-07 13:26:25 +0000180 $alignment = 4;
Steven Rostedtd74fcd12008-08-15 11:40:24 -0400181
182 # force flags for this arch
183 $ld .= " -m elf_i386";
184 $objdump .= " -M i386";
185 $objcopy .= " -O elf32-i386";
186 $cc .= " -m32";
187
Matt Fleming0da85c02008-11-12 20:11:47 +0900188} elsif ($arch eq "sh") {
Matt Fleming3a3d04a2008-11-20 21:49:52 +0000189 $alignment = 2;
Matt Fleming0da85c02008-11-12 20:11:47 +0900190
191 # force flags for this arch
192 $ld .= " -m shlelf_linux";
193 $objcopy .= " -O elf32-sh-linux";
194 $cc .= " -m32";
195
Steven Rostedt42e007d2008-11-20 07:16:16 -0800196} elsif ($arch eq "powerpc") {
197 $nm_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\.?\\S+)";
Steven Rostedt42e007d2008-11-20 07:16:16 -0800198 $function_regex = "^([0-9a-fA-F]+)\\s+<(\\.?.*?)>:";
199 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s\\.?_mcount\$";
Steven Rostedtc204f722008-11-20 15:07:34 -0500200
Steven Rostedt42e007d2008-11-20 07:16:16 -0800201 if ($bits == 64) {
202 $type = ".quad";
Steven Rostedt42e007d2008-11-20 07:16:16 -0800203 }
204
Jim Radforde58918a2008-11-20 19:48:39 -0800205} elsif ($arch eq "arm") {
206 $alignment = 2;
207 $section_type = '%progbits';
208
Shaohua Li418071e2009-01-09 11:29:44 +0800209} elsif ($arch eq "ia64") {
210 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
211 $type = "data8";
212
213 if ($is_module eq "0") {
214 $cc .= " -mconstant-gp";
215 }
Steven Rostedt8da38212008-08-14 15:45:07 -0400216} else {
217 die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD";
218}
219
220my $text_found = 0;
221my $read_function = 0;
222my $opened = 0;
Steven Rostedt8da38212008-08-14 15:45:07 -0400223my $mcount_section = "__mcount_loc";
224
225my $dirname;
226my $filename;
227my $prefix;
228my $ext;
229
230if ($inputfile =~ m,^(.*)/([^/]*)$,) {
231 $dirname = $1;
232 $filename = $2;
233} else {
234 $dirname = ".";
235 $filename = $inputfile;
236}
237
238if ($filename =~ m,^(.*)(\.\S),) {
239 $prefix = $1;
240 $ext = $2;
241} else {
242 $prefix = $filename;
243 $ext = "";
244}
245
246my $mcount_s = $dirname . "/.tmp_mc_" . $prefix . ".s";
247my $mcount_o = $dirname . "/.tmp_mc_" . $prefix . ".o";
248
249#
Steven Rostedtf2f84582008-08-25 14:52:11 -0400250# --globalize-symbols came out in 2.17, we must test the version
251# of objcopy, and if it is less than 2.17, then we can not
252# record local functions.
253my $use_locals = 01;
254my $local_warn_once = 0;
255my $found_version = 0;
256
257open (IN, "$objcopy --version |") || die "error running $objcopy";
258while (<IN>) {
259 if (/objcopy.*\s(\d+)\.(\d+)/) {
260 my $major = $1;
261 my $minor = $2;
262
263 $found_version = 1;
264 if ($major < 2 ||
265 ($major == 2 && $minor < 17)) {
266 $use_locals = 0;
267 }
268 last;
269 }
270}
271close (IN);
272
273if (!$found_version) {
274 print STDERR "WARNING: could not find objcopy version.\n" .
275 "\tDisabling local function references.\n";
276}
277
278
279#
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400280# Step 1: find all the local (static functions) and weak symbols.
281# 't' is local, 'w/W' is weak (we never use a weak function)
Steven Rostedt8da38212008-08-14 15:45:07 -0400282#
283open (IN, "$nm $inputfile|") || die "error running $nm";
284while (<IN>) {
Steven Rostedt42e007d2008-11-20 07:16:16 -0800285 if (/$nm_regex/) {
Steven Rostedt8da38212008-08-14 15:45:07 -0400286 $locals{$1} = 1;
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400287 } elsif (/^[0-9a-fA-F]+\s+([wW])\s+(\S+)/) {
288 $weak{$2} = $1;
Steven Rostedt8da38212008-08-14 15:45:07 -0400289 }
290}
291close(IN);
292
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400293my @offsets; # Array of offsets of mcount callers
294my $ref_func; # reference function to use for offsets
295my $offset = 0; # offset of ref_func to section beginning
296
297##
298# update_funcs - print out the current mcount callers
299#
300# Go through the list of offsets to callers and write them to
301# the output file in a format that can be read by an assembler.
302#
303sub update_funcs
304{
305 return if ($#offsets < 0);
306
307 defined($ref_func) || die "No function to reference";
308
309 # A section only had a weak function, to represent it.
310 # Unfortunately, a weak function may be overwritten by another
311 # function of the same name, making all these offsets incorrect.
312 # To be safe, we simply print a warning and bail.
313 if (defined $weak{$ref_func}) {
314 print STDERR
315 "$inputfile: WARNING: referencing weak function" .
316 " $ref_func for mcount\n";
317 return;
318 }
319
320 # is this function static? If so, note this fact.
321 if (defined $locals{$ref_func}) {
Steven Rostedtf2f84582008-08-25 14:52:11 -0400322
323 # only use locals if objcopy supports globalize-symbols
324 if (!$use_locals) {
Steven Rostedtf2f84582008-08-25 14:52:11 -0400325 return;
326 }
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400327 $convert{$ref_func} = 1;
328 }
329
330 # Loop through all the mcount caller offsets and print a reference
331 # to the caller based from the ref_func.
332 for (my $i=0; $i <= $#offsets; $i++) {
333 if (!$opened) {
334 open(FILE, ">$mcount_s") || die "can't create $mcount_s\n";
335 $opened = 1;
Jim Radforde58918a2008-11-20 19:48:39 -0800336 print FILE "\t.section $mcount_section,\"a\",$section_type\n";
Steven Rostedt42e007d2008-11-20 07:16:16 -0800337 print FILE "\t.align $alignment\n" if (defined($alignment));
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400338 }
339 printf FILE "\t%s %s + %d\n", $type, $ref_func, $offsets[$i] - $offset;
340 }
341}
342
Steven Rostedt8da38212008-08-14 15:45:07 -0400343#
344# Step 2: find the sections and mcount call sites
345#
346open(IN, "$objdump -dr $inputfile|") || die "error running $objdump";
347
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400348my $text;
349
Steven Rostedt8da38212008-08-14 15:45:07 -0400350while (<IN>) {
351 # is it a section?
352 if (/$section_regex/) {
Steven Rostedt34698bc2008-10-23 09:32:58 -0400353
354 # Only record text sections that we know are safe
355 if (defined($text_sections{$1})) {
356 $read_function = 1;
357 } else {
358 $read_function = 0;
359 }
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400360 # print out any recorded offsets
361 update_funcs() if ($text_found);
362
363 # reset all markers and arrays
Steven Rostedt8da38212008-08-14 15:45:07 -0400364 $text_found = 0;
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400365 undef($ref_func);
366 undef(@offsets);
367
Steven Rostedt8da38212008-08-14 15:45:07 -0400368 # section found, now is this a start of a function?
369 } elsif ($read_function && /$function_regex/) {
Steven Rostedt8da38212008-08-14 15:45:07 -0400370 $text_found = 1;
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400371 $offset = hex $1;
372 $text = $2;
373
374 # if this is either a local function or a weak function
375 # keep looking for functions that are global that
376 # we can use safely.
377 if (!defined($locals{$text}) && !defined($weak{$text})) {
378 $ref_func = $text;
379 $read_function = 0;
380 } else {
381 # if we already have a function, and this is weak, skip it
382 if (!defined($ref_func) || !defined($weak{$text})) {
383 $ref_func = $text;
384 }
Steven Rostedt8da38212008-08-14 15:45:07 -0400385 }
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400386 }
387
388 # is this a call site to mcount? If so, record it to print later
389 if ($text_found && /$mcount_regex/) {
390 $offsets[$#offsets + 1] = hex $1;
Steven Rostedt8da38212008-08-14 15:45:07 -0400391 }
392}
393
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400394# dump out anymore offsets that may have been found
395update_funcs() if ($text_found);
396
Steven Rostedt8da38212008-08-14 15:45:07 -0400397# If we did not find any mcount callers, we are done (do nothing).
398if (!$opened) {
399 exit(0);
400}
401
402close(FILE);
403
404#
405# Step 3: Compile the file that holds the list of call sites to mcount.
406#
407`$cc -o $mcount_o -c $mcount_s`;
408
409my @converts = keys %convert;
410
411#
412# Step 4: Do we have sections that started with local functions?
413#
414if ($#converts >= 0) {
415 my $globallist = "";
416 my $locallist = "";
417
418 foreach my $con (@converts) {
419 $globallist .= " --globalize-symbol $con";
420 $locallist .= " --localize-symbol $con";
421 }
422
423 my $globalobj = $dirname . "/.tmp_gl_" . $filename;
424 my $globalmix = $dirname . "/.tmp_mx_" . $filename;
425
426 #
427 # Step 5: set up each local function as a global
428 #
429 `$objcopy $globallist $inputfile $globalobj`;
430
431 #
432 # Step 6: Link the global version to our list.
433 #
434 `$ld -r $globalobj $mcount_o -o $globalmix`;
435
436 #
437 # Step 7: Convert the local functions back into local symbols
438 #
439 `$objcopy $locallist $globalmix $inputfile`;
440
441 # Remove the temp files
442 `$rm $globalobj $globalmix`;
443
444} else {
445
446 my $mix = $dirname . "/.tmp_mx_" . $filename;
447
448 #
449 # Step 8: Link the object with our list of call sites object.
450 #
451 `$ld -r $inputfile $mcount_o -o $mix`;
452
453 #
454 # Step 9: Move the result back to the original object.
455 #
456 `$mv $mix $inputfile`;
457}
458
459# Clean up the temp files
460`$rm $mcount_o $mcount_s`;
461
462exit(0);