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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, $inputfile) = @ARGV;
Steven Rostedt8da38212008-08-14 15:45:07 -0400111
Steven Rostedt34698bc2008-10-23 09:32:58 -0400112# Acceptable sections to record.
113my %text_sections = (
114 ".text" => 1,
115);
116
Steven Rostedt8da38212008-08-14 15:45:07 -0400117$objdump = "objdump" if ((length $objdump) == 0);
118$objcopy = "objcopy" if ((length $objcopy) == 0);
119$cc = "gcc" if ((length $cc) == 0);
120$ld = "ld" if ((length $ld) == 0);
121$nm = "nm" if ((length $nm) == 0);
122$rm = "rm" if ((length $rm) == 0);
123$mv = "mv" if ((length $mv) == 0);
124
125#print STDERR "running: $P '$arch' '$objdump' '$objcopy' '$cc' '$ld' " .
126# "'$nm' '$rm' '$mv' '$inputfile'\n";
127
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400128my %locals; # List of local (static) functions
129my %weak; # List of weak functions
130my %convert; # List of local functions used that needs conversion
Steven Rostedt8da38212008-08-14 15:45:07 -0400131
132my $type;
133my $section_regex; # Find the start of a section
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400134my $function_regex; # Find the name of a function
135 # (return offset and func name)
Steven Rostedt8da38212008-08-14 15:45:07 -0400136my $mcount_regex; # Find the call site to mcount (return offset)
Matt Fleming7d5222a2008-11-07 13:26:25 +0000137my $alignment; # The .align value to use for $mcount_section
Steven Rostedt8da38212008-08-14 15:45:07 -0400138
Steven Rostedtdce9d182008-10-23 09:32:57 -0400139if ($arch eq "x86") {
140 if ($bits == 64) {
141 $arch = "x86_64";
142 } else {
143 $arch = "i386";
144 }
145}
146
Steven Rostedt8da38212008-08-14 15:45:07 -0400147if ($arch eq "x86_64") {
Steven Rostedt34698bc2008-10-23 09:32:58 -0400148 $section_regex = "Disassembly of section\\s+(\\S+):";
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400149 $function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
Steven Rostedt8da38212008-08-14 15:45:07 -0400150 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount([+-]0x[0-9a-zA-Z]+)?\$";
151 $type = ".quad";
Matt Fleming7d5222a2008-11-07 13:26:25 +0000152 $alignment = 8;
Steven Rostedtd74fcd12008-08-15 11:40:24 -0400153
154 # force flags for this arch
155 $ld .= " -m elf_x86_64";
156 $objdump .= " -M x86-64";
157 $objcopy .= " -O elf64-x86-64";
158 $cc .= " -m64";
159
Steven Rostedt8da38212008-08-14 15:45:07 -0400160} elsif ($arch eq "i386") {
Steven Rostedt34698bc2008-10-23 09:32:58 -0400161 $section_regex = "Disassembly of section\\s+(\\S+):";
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400162 $function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
Steven Rostedt8da38212008-08-14 15:45:07 -0400163 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount\$";
164 $type = ".long";
Matt Fleming7d5222a2008-11-07 13:26:25 +0000165 $alignment = 4;
Steven Rostedtd74fcd12008-08-15 11:40:24 -0400166
167 # force flags for this arch
168 $ld .= " -m elf_i386";
169 $objdump .= " -M i386";
170 $objcopy .= " -O elf32-i386";
171 $cc .= " -m32";
172
Matt Fleming0da85c02008-11-12 20:11:47 +0900173} elsif ($arch eq "sh") {
174 $section_regex = "Disassembly of section\\s+(\\S+):";
175 $function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
176 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount\$";
177 $type = ".long";
178
179 # force flags for this arch
180 $ld .= " -m shlelf_linux";
181 $objcopy .= " -O elf32-sh-linux";
182 $cc .= " -m32";
183
Steven Rostedt8da38212008-08-14 15:45:07 -0400184} else {
185 die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD";
186}
187
188my $text_found = 0;
189my $read_function = 0;
190my $opened = 0;
Steven Rostedt8da38212008-08-14 15:45:07 -0400191my $mcount_section = "__mcount_loc";
192
193my $dirname;
194my $filename;
195my $prefix;
196my $ext;
197
198if ($inputfile =~ m,^(.*)/([^/]*)$,) {
199 $dirname = $1;
200 $filename = $2;
201} else {
202 $dirname = ".";
203 $filename = $inputfile;
204}
205
206if ($filename =~ m,^(.*)(\.\S),) {
207 $prefix = $1;
208 $ext = $2;
209} else {
210 $prefix = $filename;
211 $ext = "";
212}
213
214my $mcount_s = $dirname . "/.tmp_mc_" . $prefix . ".s";
215my $mcount_o = $dirname . "/.tmp_mc_" . $prefix . ".o";
216
217#
Steven Rostedtf2f84582008-08-25 14:52:11 -0400218# --globalize-symbols came out in 2.17, we must test the version
219# of objcopy, and if it is less than 2.17, then we can not
220# record local functions.
221my $use_locals = 01;
222my $local_warn_once = 0;
223my $found_version = 0;
224
225open (IN, "$objcopy --version |") || die "error running $objcopy";
226while (<IN>) {
227 if (/objcopy.*\s(\d+)\.(\d+)/) {
228 my $major = $1;
229 my $minor = $2;
230
231 $found_version = 1;
232 if ($major < 2 ||
233 ($major == 2 && $minor < 17)) {
234 $use_locals = 0;
235 }
236 last;
237 }
238}
239close (IN);
240
241if (!$found_version) {
242 print STDERR "WARNING: could not find objcopy version.\n" .
243 "\tDisabling local function references.\n";
244}
245
246
247#
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400248# Step 1: find all the local (static functions) and weak symbols.
249# 't' is local, 'w/W' is weak (we never use a weak function)
Steven Rostedt8da38212008-08-14 15:45:07 -0400250#
251open (IN, "$nm $inputfile|") || die "error running $nm";
252while (<IN>) {
253 if (/^[0-9a-fA-F]+\s+t\s+(\S+)/) {
254 $locals{$1} = 1;
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400255 } elsif (/^[0-9a-fA-F]+\s+([wW])\s+(\S+)/) {
256 $weak{$2} = $1;
Steven Rostedt8da38212008-08-14 15:45:07 -0400257 }
258}
259close(IN);
260
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400261my @offsets; # Array of offsets of mcount callers
262my $ref_func; # reference function to use for offsets
263my $offset = 0; # offset of ref_func to section beginning
264
265##
266# update_funcs - print out the current mcount callers
267#
268# Go through the list of offsets to callers and write them to
269# the output file in a format that can be read by an assembler.
270#
271sub update_funcs
272{
273 return if ($#offsets < 0);
274
275 defined($ref_func) || die "No function to reference";
276
277 # A section only had a weak function, to represent it.
278 # Unfortunately, a weak function may be overwritten by another
279 # function of the same name, making all these offsets incorrect.
280 # To be safe, we simply print a warning and bail.
281 if (defined $weak{$ref_func}) {
282 print STDERR
283 "$inputfile: WARNING: referencing weak function" .
284 " $ref_func for mcount\n";
285 return;
286 }
287
288 # is this function static? If so, note this fact.
289 if (defined $locals{$ref_func}) {
Steven Rostedtf2f84582008-08-25 14:52:11 -0400290
291 # only use locals if objcopy supports globalize-symbols
292 if (!$use_locals) {
Steven Rostedtf2f84582008-08-25 14:52:11 -0400293 return;
294 }
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400295 $convert{$ref_func} = 1;
296 }
297
298 # Loop through all the mcount caller offsets and print a reference
299 # to the caller based from the ref_func.
300 for (my $i=0; $i <= $#offsets; $i++) {
301 if (!$opened) {
302 open(FILE, ">$mcount_s") || die "can't create $mcount_s\n";
303 $opened = 1;
304 print FILE "\t.section $mcount_section,\"a\",\@progbits\n";
Matt Fleming7d5222a2008-11-07 13:26:25 +0000305 print FILE "\t.align $alignment\n";
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400306 }
307 printf FILE "\t%s %s + %d\n", $type, $ref_func, $offsets[$i] - $offset;
308 }
309}
310
Steven Rostedt8da38212008-08-14 15:45:07 -0400311#
312# Step 2: find the sections and mcount call sites
313#
314open(IN, "$objdump -dr $inputfile|") || die "error running $objdump";
315
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400316my $text;
317
Steven Rostedt8da38212008-08-14 15:45:07 -0400318while (<IN>) {
319 # is it a section?
320 if (/$section_regex/) {
Steven Rostedt34698bc2008-10-23 09:32:58 -0400321
322 # Only record text sections that we know are safe
323 if (defined($text_sections{$1})) {
324 $read_function = 1;
325 } else {
326 $read_function = 0;
327 }
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400328 # print out any recorded offsets
329 update_funcs() if ($text_found);
330
331 # reset all markers and arrays
Steven Rostedt8da38212008-08-14 15:45:07 -0400332 $text_found = 0;
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400333 undef($ref_func);
334 undef(@offsets);
335
Steven Rostedt8da38212008-08-14 15:45:07 -0400336 # section found, now is this a start of a function?
337 } elsif ($read_function && /$function_regex/) {
Steven Rostedt8da38212008-08-14 15:45:07 -0400338 $text_found = 1;
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400339 $offset = hex $1;
340 $text = $2;
341
342 # if this is either a local function or a weak function
343 # keep looking for functions that are global that
344 # we can use safely.
345 if (!defined($locals{$text}) && !defined($weak{$text})) {
346 $ref_func = $text;
347 $read_function = 0;
348 } else {
349 # if we already have a function, and this is weak, skip it
350 if (!defined($ref_func) || !defined($weak{$text})) {
351 $ref_func = $text;
352 }
Steven Rostedt8da38212008-08-14 15:45:07 -0400353 }
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400354 }
355
356 # is this a call site to mcount? If so, record it to print later
357 if ($text_found && /$mcount_regex/) {
358 $offsets[$#offsets + 1] = hex $1;
Steven Rostedt8da38212008-08-14 15:45:07 -0400359 }
360}
361
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400362# dump out anymore offsets that may have been found
363update_funcs() if ($text_found);
364
Steven Rostedt8da38212008-08-14 15:45:07 -0400365# If we did not find any mcount callers, we are done (do nothing).
366if (!$opened) {
367 exit(0);
368}
369
370close(FILE);
371
372#
373# Step 3: Compile the file that holds the list of call sites to mcount.
374#
375`$cc -o $mcount_o -c $mcount_s`;
376
377my @converts = keys %convert;
378
379#
380# Step 4: Do we have sections that started with local functions?
381#
382if ($#converts >= 0) {
383 my $globallist = "";
384 my $locallist = "";
385
386 foreach my $con (@converts) {
387 $globallist .= " --globalize-symbol $con";
388 $locallist .= " --localize-symbol $con";
389 }
390
391 my $globalobj = $dirname . "/.tmp_gl_" . $filename;
392 my $globalmix = $dirname . "/.tmp_mx_" . $filename;
393
394 #
395 # Step 5: set up each local function as a global
396 #
397 `$objcopy $globallist $inputfile $globalobj`;
398
399 #
400 # Step 6: Link the global version to our list.
401 #
402 `$ld -r $globalobj $mcount_o -o $globalmix`;
403
404 #
405 # Step 7: Convert the local functions back into local symbols
406 #
407 `$objcopy $locallist $globalmix $inputfile`;
408
409 # Remove the temp files
410 `$rm $globalobj $globalmix`;
411
412} else {
413
414 my $mix = $dirname . "/.tmp_mx_" . $filename;
415
416 #
417 # Step 8: Link the object with our list of call sites object.
418 #
419 `$ld -r $inputfile $mcount_o -o $mix`;
420
421 #
422 # Step 9: Move the result back to the original object.
423 #
424 `$mv $mix $inputfile`;
425}
426
427# Clean up the temp files
428`$rm $mcount_o $mcount_s`;
429
430exit(0);