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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 $mcount_regex; # Find the call site to mcount (return offset)
137
Steven Rostedtdce9d182008-10-23 09:32:57 -0400138if ($arch eq "x86") {
139 if ($bits == 64) {
140 $arch = "x86_64";
141 } else {
142 $arch = "i386";
143 }
144}
145
Steven Rostedt8da38212008-08-14 15:45:07 -0400146if ($arch eq "x86_64") {
Steven Rostedt34698bc2008-10-23 09:32:58 -0400147 $section_regex = "Disassembly of section\\s+(\\S+):";
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400148 $function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
Steven Rostedt8da38212008-08-14 15:45:07 -0400149 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount([+-]0x[0-9a-zA-Z]+)?\$";
150 $type = ".quad";
Steven Rostedtd74fcd12008-08-15 11:40:24 -0400151
152 # force flags for this arch
153 $ld .= " -m elf_x86_64";
154 $objdump .= " -M x86-64";
155 $objcopy .= " -O elf64-x86-64";
156 $cc .= " -m64";
157
Steven Rostedt8da38212008-08-14 15:45:07 -0400158} elsif ($arch eq "i386") {
Steven Rostedt34698bc2008-10-23 09:32:58 -0400159 $section_regex = "Disassembly of section\\s+(\\S+):";
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400160 $function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
Steven Rostedt8da38212008-08-14 15:45:07 -0400161 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount\$";
162 $type = ".long";
Steven Rostedtd74fcd12008-08-15 11:40:24 -0400163
164 # force flags for this arch
165 $ld .= " -m elf_i386";
166 $objdump .= " -M i386";
167 $objcopy .= " -O elf32-i386";
168 $cc .= " -m32";
169
Steven Rostedt8da38212008-08-14 15:45:07 -0400170} else {
171 die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD";
172}
173
174my $text_found = 0;
175my $read_function = 0;
176my $opened = 0;
Steven Rostedt8da38212008-08-14 15:45:07 -0400177my $mcount_section = "__mcount_loc";
178
179my $dirname;
180my $filename;
181my $prefix;
182my $ext;
183
184if ($inputfile =~ m,^(.*)/([^/]*)$,) {
185 $dirname = $1;
186 $filename = $2;
187} else {
188 $dirname = ".";
189 $filename = $inputfile;
190}
191
192if ($filename =~ m,^(.*)(\.\S),) {
193 $prefix = $1;
194 $ext = $2;
195} else {
196 $prefix = $filename;
197 $ext = "";
198}
199
200my $mcount_s = $dirname . "/.tmp_mc_" . $prefix . ".s";
201my $mcount_o = $dirname . "/.tmp_mc_" . $prefix . ".o";
202
203#
Steven Rostedtf2f84582008-08-25 14:52:11 -0400204# --globalize-symbols came out in 2.17, we must test the version
205# of objcopy, and if it is less than 2.17, then we can not
206# record local functions.
207my $use_locals = 01;
208my $local_warn_once = 0;
209my $found_version = 0;
210
211open (IN, "$objcopy --version |") || die "error running $objcopy";
212while (<IN>) {
213 if (/objcopy.*\s(\d+)\.(\d+)/) {
214 my $major = $1;
215 my $minor = $2;
216
217 $found_version = 1;
218 if ($major < 2 ||
219 ($major == 2 && $minor < 17)) {
220 $use_locals = 0;
221 }
222 last;
223 }
224}
225close (IN);
226
227if (!$found_version) {
228 print STDERR "WARNING: could not find objcopy version.\n" .
229 "\tDisabling local function references.\n";
230}
231
232
233#
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400234# Step 1: find all the local (static functions) and weak symbols.
235# 't' is local, 'w/W' is weak (we never use a weak function)
Steven Rostedt8da38212008-08-14 15:45:07 -0400236#
237open (IN, "$nm $inputfile|") || die "error running $nm";
238while (<IN>) {
239 if (/^[0-9a-fA-F]+\s+t\s+(\S+)/) {
240 $locals{$1} = 1;
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400241 } elsif (/^[0-9a-fA-F]+\s+([wW])\s+(\S+)/) {
242 $weak{$2} = $1;
Steven Rostedt8da38212008-08-14 15:45:07 -0400243 }
244}
245close(IN);
246
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400247my @offsets; # Array of offsets of mcount callers
248my $ref_func; # reference function to use for offsets
249my $offset = 0; # offset of ref_func to section beginning
250
251##
252# update_funcs - print out the current mcount callers
253#
254# Go through the list of offsets to callers and write them to
255# the output file in a format that can be read by an assembler.
256#
257sub update_funcs
258{
259 return if ($#offsets < 0);
260
261 defined($ref_func) || die "No function to reference";
262
263 # A section only had a weak function, to represent it.
264 # Unfortunately, a weak function may be overwritten by another
265 # function of the same name, making all these offsets incorrect.
266 # To be safe, we simply print a warning and bail.
267 if (defined $weak{$ref_func}) {
268 print STDERR
269 "$inputfile: WARNING: referencing weak function" .
270 " $ref_func for mcount\n";
271 return;
272 }
273
274 # is this function static? If so, note this fact.
275 if (defined $locals{$ref_func}) {
Steven Rostedtf2f84582008-08-25 14:52:11 -0400276
277 # only use locals if objcopy supports globalize-symbols
278 if (!$use_locals) {
Steven Rostedtf2f84582008-08-25 14:52:11 -0400279 return;
280 }
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400281 $convert{$ref_func} = 1;
282 }
283
284 # Loop through all the mcount caller offsets and print a reference
285 # to the caller based from the ref_func.
286 for (my $i=0; $i <= $#offsets; $i++) {
287 if (!$opened) {
288 open(FILE, ">$mcount_s") || die "can't create $mcount_s\n";
289 $opened = 1;
290 print FILE "\t.section $mcount_section,\"a\",\@progbits\n";
291 }
292 printf FILE "\t%s %s + %d\n", $type, $ref_func, $offsets[$i] - $offset;
293 }
294}
295
Steven Rostedt8da38212008-08-14 15:45:07 -0400296#
297# Step 2: find the sections and mcount call sites
298#
299open(IN, "$objdump -dr $inputfile|") || die "error running $objdump";
300
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400301my $text;
302
Steven Rostedt8da38212008-08-14 15:45:07 -0400303while (<IN>) {
304 # is it a section?
305 if (/$section_regex/) {
Steven Rostedt34698bc2008-10-23 09:32:58 -0400306
307 # Only record text sections that we know are safe
308 if (defined($text_sections{$1})) {
309 $read_function = 1;
310 } else {
311 $read_function = 0;
312 }
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400313 # print out any recorded offsets
314 update_funcs() if ($text_found);
315
316 # reset all markers and arrays
Steven Rostedt8da38212008-08-14 15:45:07 -0400317 $text_found = 0;
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400318 undef($ref_func);
319 undef(@offsets);
320
Steven Rostedt8da38212008-08-14 15:45:07 -0400321 # section found, now is this a start of a function?
322 } elsif ($read_function && /$function_regex/) {
Steven Rostedt8da38212008-08-14 15:45:07 -0400323 $text_found = 1;
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400324 $offset = hex $1;
325 $text = $2;
326
327 # if this is either a local function or a weak function
328 # keep looking for functions that are global that
329 # we can use safely.
330 if (!defined($locals{$text}) && !defined($weak{$text})) {
331 $ref_func = $text;
332 $read_function = 0;
333 } else {
334 # if we already have a function, and this is weak, skip it
335 if (!defined($ref_func) || !defined($weak{$text})) {
336 $ref_func = $text;
337 }
Steven Rostedt8da38212008-08-14 15:45:07 -0400338 }
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400339 }
340
341 # is this a call site to mcount? If so, record it to print later
342 if ($text_found && /$mcount_regex/) {
343 $offsets[$#offsets + 1] = hex $1;
Steven Rostedt8da38212008-08-14 15:45:07 -0400344 }
345}
346
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400347# dump out anymore offsets that may have been found
348update_funcs() if ($text_found);
349
Steven Rostedt8da38212008-08-14 15:45:07 -0400350# If we did not find any mcount callers, we are done (do nothing).
351if (!$opened) {
352 exit(0);
353}
354
355close(FILE);
356
357#
358# Step 3: Compile the file that holds the list of call sites to mcount.
359#
360`$cc -o $mcount_o -c $mcount_s`;
361
362my @converts = keys %convert;
363
364#
365# Step 4: Do we have sections that started with local functions?
366#
367if ($#converts >= 0) {
368 my $globallist = "";
369 my $locallist = "";
370
371 foreach my $con (@converts) {
372 $globallist .= " --globalize-symbol $con";
373 $locallist .= " --localize-symbol $con";
374 }
375
376 my $globalobj = $dirname . "/.tmp_gl_" . $filename;
377 my $globalmix = $dirname . "/.tmp_mx_" . $filename;
378
379 #
380 # Step 5: set up each local function as a global
381 #
382 `$objcopy $globallist $inputfile $globalobj`;
383
384 #
385 # Step 6: Link the global version to our list.
386 #
387 `$ld -r $globalobj $mcount_o -o $globalmix`;
388
389 #
390 # Step 7: Convert the local functions back into local symbols
391 #
392 `$objcopy $locallist $globalmix $inputfile`;
393
394 # Remove the temp files
395 `$rm $globalobj $globalmix`;
396
397} else {
398
399 my $mix = $dirname . "/.tmp_mx_" . $filename;
400
401 #
402 # Step 8: Link the object with our list of call sites object.
403 #
404 `$ld -r $inputfile $mcount_o -o $mix`;
405
406 #
407 # Step 9: Move the result back to the original object.
408 #
409 `$mv $mix $inputfile`;
410}
411
412# Clean up the temp files
413`$rm $mcount_o $mcount_s`;
414
415exit(0);