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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: $V\n";
106 exit(1);
107}
108
109my ($arch, $objdump, $objcopy, $cc, $ld, $nm, $rm, $mv, $inputfile) = @ARGV;
110
Steven Rostedt8da38212008-08-14 15:45:07 -0400111$objdump = "objdump" if ((length $objdump) == 0);
112$objcopy = "objcopy" if ((length $objcopy) == 0);
113$cc = "gcc" if ((length $cc) == 0);
114$ld = "ld" if ((length $ld) == 0);
115$nm = "nm" if ((length $nm) == 0);
116$rm = "rm" if ((length $rm) == 0);
117$mv = "mv" if ((length $mv) == 0);
118
119#print STDERR "running: $P '$arch' '$objdump' '$objcopy' '$cc' '$ld' " .
120# "'$nm' '$rm' '$mv' '$inputfile'\n";
121
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400122my %locals; # List of local (static) functions
123my %weak; # List of weak functions
124my %convert; # List of local functions used that needs conversion
Steven Rostedt8da38212008-08-14 15:45:07 -0400125
126my $type;
127my $section_regex; # Find the start of a section
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400128my $function_regex; # Find the name of a function
129 # (return offset and func name)
Steven Rostedt8da38212008-08-14 15:45:07 -0400130my $mcount_regex; # Find the call site to mcount (return offset)
131
132if ($arch eq "x86_64") {
133 $section_regex = "Disassembly of section";
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400134 $function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
Steven Rostedt8da38212008-08-14 15:45:07 -0400135 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount([+-]0x[0-9a-zA-Z]+)?\$";
136 $type = ".quad";
Steven Rostedtd74fcd12008-08-15 11:40:24 -0400137
138 # force flags for this arch
139 $ld .= " -m elf_x86_64";
140 $objdump .= " -M x86-64";
141 $objcopy .= " -O elf64-x86-64";
142 $cc .= " -m64";
143
Steven Rostedt8da38212008-08-14 15:45:07 -0400144} elsif ($arch eq "i386") {
145 $section_regex = "Disassembly of section";
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400146 $function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
Steven Rostedt8da38212008-08-14 15:45:07 -0400147 $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount\$";
148 $type = ".long";
Steven Rostedtd74fcd12008-08-15 11:40:24 -0400149
150 # force flags for this arch
151 $ld .= " -m elf_i386";
152 $objdump .= " -M i386";
153 $objcopy .= " -O elf32-i386";
154 $cc .= " -m32";
155
Steven Rostedt8da38212008-08-14 15:45:07 -0400156} else {
157 die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD";
158}
159
160my $text_found = 0;
161my $read_function = 0;
162my $opened = 0;
Steven Rostedt8da38212008-08-14 15:45:07 -0400163my $mcount_section = "__mcount_loc";
164
165my $dirname;
166my $filename;
167my $prefix;
168my $ext;
169
170if ($inputfile =~ m,^(.*)/([^/]*)$,) {
171 $dirname = $1;
172 $filename = $2;
173} else {
174 $dirname = ".";
175 $filename = $inputfile;
176}
177
178if ($filename =~ m,^(.*)(\.\S),) {
179 $prefix = $1;
180 $ext = $2;
181} else {
182 $prefix = $filename;
183 $ext = "";
184}
185
186my $mcount_s = $dirname . "/.tmp_mc_" . $prefix . ".s";
187my $mcount_o = $dirname . "/.tmp_mc_" . $prefix . ".o";
188
189#
Steven Rostedtf2f84582008-08-25 14:52:11 -0400190# --globalize-symbols came out in 2.17, we must test the version
191# of objcopy, and if it is less than 2.17, then we can not
192# record local functions.
193my $use_locals = 01;
194my $local_warn_once = 0;
195my $found_version = 0;
196
197open (IN, "$objcopy --version |") || die "error running $objcopy";
198while (<IN>) {
199 if (/objcopy.*\s(\d+)\.(\d+)/) {
200 my $major = $1;
201 my $minor = $2;
202
203 $found_version = 1;
204 if ($major < 2 ||
205 ($major == 2 && $minor < 17)) {
206 $use_locals = 0;
207 }
208 last;
209 }
210}
211close (IN);
212
213if (!$found_version) {
214 print STDERR "WARNING: could not find objcopy version.\n" .
215 "\tDisabling local function references.\n";
216}
217
218
219#
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400220# Step 1: find all the local (static functions) and weak symbols.
221# 't' is local, 'w/W' is weak (we never use a weak function)
Steven Rostedt8da38212008-08-14 15:45:07 -0400222#
223open (IN, "$nm $inputfile|") || die "error running $nm";
224while (<IN>) {
225 if (/^[0-9a-fA-F]+\s+t\s+(\S+)/) {
226 $locals{$1} = 1;
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400227 } elsif (/^[0-9a-fA-F]+\s+([wW])\s+(\S+)/) {
228 $weak{$2} = $1;
Steven Rostedt8da38212008-08-14 15:45:07 -0400229 }
230}
231close(IN);
232
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400233my @offsets; # Array of offsets of mcount callers
234my $ref_func; # reference function to use for offsets
235my $offset = 0; # offset of ref_func to section beginning
236
237##
238# update_funcs - print out the current mcount callers
239#
240# Go through the list of offsets to callers and write them to
241# the output file in a format that can be read by an assembler.
242#
243sub update_funcs
244{
245 return if ($#offsets < 0);
246
247 defined($ref_func) || die "No function to reference";
248
249 # A section only had a weak function, to represent it.
250 # Unfortunately, a weak function may be overwritten by another
251 # function of the same name, making all these offsets incorrect.
252 # To be safe, we simply print a warning and bail.
253 if (defined $weak{$ref_func}) {
254 print STDERR
255 "$inputfile: WARNING: referencing weak function" .
256 " $ref_func for mcount\n";
257 return;
258 }
259
260 # is this function static? If so, note this fact.
261 if (defined $locals{$ref_func}) {
Steven Rostedtf2f84582008-08-25 14:52:11 -0400262
263 # only use locals if objcopy supports globalize-symbols
264 if (!$use_locals) {
Steven Rostedtf2f84582008-08-25 14:52:11 -0400265 return;
266 }
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400267 $convert{$ref_func} = 1;
268 }
269
270 # Loop through all the mcount caller offsets and print a reference
271 # to the caller based from the ref_func.
272 for (my $i=0; $i <= $#offsets; $i++) {
273 if (!$opened) {
274 open(FILE, ">$mcount_s") || die "can't create $mcount_s\n";
275 $opened = 1;
276 print FILE "\t.section $mcount_section,\"a\",\@progbits\n";
277 }
278 printf FILE "\t%s %s + %d\n", $type, $ref_func, $offsets[$i] - $offset;
279 }
280}
281
Steven Rostedt8da38212008-08-14 15:45:07 -0400282#
283# Step 2: find the sections and mcount call sites
284#
285open(IN, "$objdump -dr $inputfile|") || die "error running $objdump";
286
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400287my $text;
288
Steven Rostedt8da38212008-08-14 15:45:07 -0400289while (<IN>) {
290 # is it a section?
291 if (/$section_regex/) {
292 $read_function = 1;
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400293 # print out any recorded offsets
294 update_funcs() if ($text_found);
295
296 # reset all markers and arrays
Steven Rostedt8da38212008-08-14 15:45:07 -0400297 $text_found = 0;
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400298 undef($ref_func);
299 undef(@offsets);
300
Steven Rostedt8da38212008-08-14 15:45:07 -0400301 # section found, now is this a start of a function?
302 } elsif ($read_function && /$function_regex/) {
Steven Rostedt8da38212008-08-14 15:45:07 -0400303 $text_found = 1;
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400304 $offset = hex $1;
305 $text = $2;
306
307 # if this is either a local function or a weak function
308 # keep looking for functions that are global that
309 # we can use safely.
310 if (!defined($locals{$text}) && !defined($weak{$text})) {
311 $ref_func = $text;
312 $read_function = 0;
313 } else {
314 # if we already have a function, and this is weak, skip it
315 if (!defined($ref_func) || !defined($weak{$text})) {
316 $ref_func = $text;
317 }
Steven Rostedt8da38212008-08-14 15:45:07 -0400318 }
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400319 }
320
321 # is this a call site to mcount? If so, record it to print later
322 if ($text_found && /$mcount_regex/) {
323 $offsets[$#offsets + 1] = hex $1;
Steven Rostedt8da38212008-08-14 15:45:07 -0400324 }
325}
326
Steven Rostedt8feff1c2008-08-20 10:07:35 -0400327# dump out anymore offsets that may have been found
328update_funcs() if ($text_found);
329
Steven Rostedt8da38212008-08-14 15:45:07 -0400330# If we did not find any mcount callers, we are done (do nothing).
331if (!$opened) {
332 exit(0);
333}
334
335close(FILE);
336
337#
338# Step 3: Compile the file that holds the list of call sites to mcount.
339#
340`$cc -o $mcount_o -c $mcount_s`;
341
342my @converts = keys %convert;
343
344#
345# Step 4: Do we have sections that started with local functions?
346#
347if ($#converts >= 0) {
348 my $globallist = "";
349 my $locallist = "";
350
351 foreach my $con (@converts) {
352 $globallist .= " --globalize-symbol $con";
353 $locallist .= " --localize-symbol $con";
354 }
355
356 my $globalobj = $dirname . "/.tmp_gl_" . $filename;
357 my $globalmix = $dirname . "/.tmp_mx_" . $filename;
358
359 #
360 # Step 5: set up each local function as a global
361 #
362 `$objcopy $globallist $inputfile $globalobj`;
363
364 #
365 # Step 6: Link the global version to our list.
366 #
367 `$ld -r $globalobj $mcount_o -o $globalmix`;
368
369 #
370 # Step 7: Convert the local functions back into local symbols
371 #
372 `$objcopy $locallist $globalmix $inputfile`;
373
374 # Remove the temp files
375 `$rm $globalobj $globalmix`;
376
377} else {
378
379 my $mix = $dirname . "/.tmp_mx_" . $filename;
380
381 #
382 # Step 8: Link the object with our list of call sites object.
383 #
384 `$ld -r $inputfile $mcount_o -o $mix`;
385
386 #
387 # Step 9: Move the result back to the original object.
388 #
389 `$mv $mix $inputfile`;
390}
391
392# Clean up the temp files
393`$rm $mcount_o $mcount_s`;
394
395exit(0);