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8da3821b SR |
1 | #!/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 | ||
96 | use strict; | |
97 | ||
98 | my $P = $0; | |
99 | $P =~ s@.*/@@g; | |
100 | ||
101 | my $V = '0.1'; | |
102 | ||
103 | if ($#ARGV < 6) { | |
104 | print "usage: $P arch objdump objcopy cc ld nm rm mv inputfile\n"; | |
105 | print "version: $V\n"; | |
106 | exit(1); | |
107 | } | |
108 | ||
dce9d18a SR |
109 | my ($arch, $bits, $objdump, $objcopy, $cc, |
110 | $ld, $nm, $rm, $mv, $inputfile) = @ARGV; | |
8da3821b | 111 | |
34698bcb SR |
112 | # Acceptable sections to record. |
113 | my %text_sections = ( | |
114 | ".text" => 1, | |
115 | ); | |
116 | ||
8da3821b SR |
117 | $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 | ||
8feff1ca SR |
128 | my %locals; # List of local (static) functions |
129 | my %weak; # List of weak functions | |
130 | my %convert; # List of local functions used that needs conversion | |
8da3821b SR |
131 | |
132 | my $type; | |
42e007d0 | 133 | my $nm_regex; # Find the local functions (return function) |
8da3821b | 134 | my $section_regex; # Find the start of a section |
8feff1ca SR |
135 | my $function_regex; # Find the name of a function |
136 | # (return offset and func name) | |
8da3821b | 137 | my $mcount_regex; # Find the call site to mcount (return offset) |
3a3d04ae | 138 | my $alignment; # The .align value to use for $mcount_section |
8da3821b | 139 | |
dce9d18a SR |
140 | if ($arch eq "x86") { |
141 | if ($bits == 64) { | |
142 | $arch = "x86_64"; | |
143 | } else { | |
144 | $arch = "i386"; | |
145 | } | |
146 | } | |
147 | ||
c204f726 SR |
148 | # |
149 | # We base the defaults off of i386, the other archs may | |
150 | # feel free to change them in the below if statements. | |
151 | # | |
152 | $nm_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\S+)"; | |
153 | $section_regex = "Disassembly of section\\s+(\\S+):"; | |
154 | $function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:"; | |
155 | $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount\$"; | |
156 | $type = ".long"; | |
157 | ||
8da3821b | 158 | if ($arch eq "x86_64") { |
8da3821b SR |
159 | $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount([+-]0x[0-9a-zA-Z]+)?\$"; |
160 | $type = ".quad"; | |
7d5222a6 | 161 | $alignment = 8; |
d74fcd1e SR |
162 | |
163 | # force flags for this arch | |
164 | $ld .= " -m elf_x86_64"; | |
165 | $objdump .= " -M x86-64"; | |
166 | $objcopy .= " -O elf64-x86-64"; | |
167 | $cc .= " -m64"; | |
168 | ||
8da3821b | 169 | } elsif ($arch eq "i386") { |
7d5222a6 | 170 | $alignment = 4; |
d74fcd1e SR |
171 | |
172 | # force flags for this arch | |
173 | $ld .= " -m elf_i386"; | |
174 | $objdump .= " -M i386"; | |
175 | $objcopy .= " -O elf32-i386"; | |
176 | $cc .= " -m32"; | |
177 | ||
0da85c09 | 178 | } elsif ($arch eq "sh") { |
3a3d04ae | 179 | $alignment = 2; |
0da85c09 MF |
180 | |
181 | # force flags for this arch | |
182 | $ld .= " -m shlelf_linux"; | |
183 | $objcopy .= " -O elf32-sh-linux"; | |
184 | $cc .= " -m32"; | |
185 | ||
42e007d0 SR |
186 | } elsif ($arch eq "powerpc") { |
187 | $nm_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\.?\\S+)"; | |
42e007d0 SR |
188 | $function_regex = "^([0-9a-fA-F]+)\\s+<(\\.?.*?)>:"; |
189 | $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s\\.?_mcount\$"; | |
c204f726 | 190 | |
42e007d0 SR |
191 | if ($bits == 64) { |
192 | $type = ".quad"; | |
42e007d0 SR |
193 | } |
194 | ||
8da3821b SR |
195 | } else { |
196 | die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD"; | |
197 | } | |
198 | ||
199 | my $text_found = 0; | |
200 | my $read_function = 0; | |
201 | my $opened = 0; | |
8da3821b SR |
202 | my $mcount_section = "__mcount_loc"; |
203 | ||
204 | my $dirname; | |
205 | my $filename; | |
206 | my $prefix; | |
207 | my $ext; | |
208 | ||
209 | if ($inputfile =~ m,^(.*)/([^/]*)$,) { | |
210 | $dirname = $1; | |
211 | $filename = $2; | |
212 | } else { | |
213 | $dirname = "."; | |
214 | $filename = $inputfile; | |
215 | } | |
216 | ||
217 | if ($filename =~ m,^(.*)(\.\S),) { | |
218 | $prefix = $1; | |
219 | $ext = $2; | |
220 | } else { | |
221 | $prefix = $filename; | |
222 | $ext = ""; | |
223 | } | |
224 | ||
225 | my $mcount_s = $dirname . "/.tmp_mc_" . $prefix . ".s"; | |
226 | my $mcount_o = $dirname . "/.tmp_mc_" . $prefix . ".o"; | |
227 | ||
f2f8458e SR |
228 | # |
229 | # --globalize-symbols came out in 2.17, we must test the version | |
230 | # of objcopy, and if it is less than 2.17, then we can not | |
231 | # record local functions. | |
232 | my $use_locals = 01; | |
233 | my $local_warn_once = 0; | |
234 | my $found_version = 0; | |
235 | ||
236 | open (IN, "$objcopy --version |") || die "error running $objcopy"; | |
237 | while (<IN>) { | |
238 | if (/objcopy.*\s(\d+)\.(\d+)/) { | |
239 | my $major = $1; | |
240 | my $minor = $2; | |
241 | ||
242 | $found_version = 1; | |
243 | if ($major < 2 || | |
244 | ($major == 2 && $minor < 17)) { | |
245 | $use_locals = 0; | |
246 | } | |
247 | last; | |
248 | } | |
249 | } | |
250 | close (IN); | |
251 | ||
252 | if (!$found_version) { | |
253 | print STDERR "WARNING: could not find objcopy version.\n" . | |
254 | "\tDisabling local function references.\n"; | |
255 | } | |
256 | ||
257 | ||
8da3821b | 258 | # |
8feff1ca SR |
259 | # Step 1: find all the local (static functions) and weak symbols. |
260 | # 't' is local, 'w/W' is weak (we never use a weak function) | |
8da3821b SR |
261 | # |
262 | open (IN, "$nm $inputfile|") || die "error running $nm"; | |
263 | while (<IN>) { | |
42e007d0 | 264 | if (/$nm_regex/) { |
8da3821b | 265 | $locals{$1} = 1; |
8feff1ca SR |
266 | } elsif (/^[0-9a-fA-F]+\s+([wW])\s+(\S+)/) { |
267 | $weak{$2} = $1; | |
8da3821b SR |
268 | } |
269 | } | |
270 | close(IN); | |
271 | ||
8feff1ca SR |
272 | my @offsets; # Array of offsets of mcount callers |
273 | my $ref_func; # reference function to use for offsets | |
274 | my $offset = 0; # offset of ref_func to section beginning | |
275 | ||
276 | ## | |
277 | # update_funcs - print out the current mcount callers | |
278 | # | |
279 | # Go through the list of offsets to callers and write them to | |
280 | # the output file in a format that can be read by an assembler. | |
281 | # | |
282 | sub update_funcs | |
283 | { | |
284 | return if ($#offsets < 0); | |
285 | ||
286 | defined($ref_func) || die "No function to reference"; | |
287 | ||
288 | # A section only had a weak function, to represent it. | |
289 | # Unfortunately, a weak function may be overwritten by another | |
290 | # function of the same name, making all these offsets incorrect. | |
291 | # To be safe, we simply print a warning and bail. | |
292 | if (defined $weak{$ref_func}) { | |
293 | print STDERR | |
294 | "$inputfile: WARNING: referencing weak function" . | |
295 | " $ref_func for mcount\n"; | |
296 | return; | |
297 | } | |
298 | ||
299 | # is this function static? If so, note this fact. | |
300 | if (defined $locals{$ref_func}) { | |
f2f8458e SR |
301 | |
302 | # only use locals if objcopy supports globalize-symbols | |
303 | if (!$use_locals) { | |
f2f8458e SR |
304 | return; |
305 | } | |
8feff1ca SR |
306 | $convert{$ref_func} = 1; |
307 | } | |
308 | ||
309 | # Loop through all the mcount caller offsets and print a reference | |
310 | # to the caller based from the ref_func. | |
311 | for (my $i=0; $i <= $#offsets; $i++) { | |
312 | if (!$opened) { | |
313 | open(FILE, ">$mcount_s") || die "can't create $mcount_s\n"; | |
314 | $opened = 1; | |
315 | print FILE "\t.section $mcount_section,\"a\",\@progbits\n"; | |
42e007d0 | 316 | print FILE "\t.align $alignment\n" if (defined($alignment)); |
8feff1ca SR |
317 | } |
318 | printf FILE "\t%s %s + %d\n", $type, $ref_func, $offsets[$i] - $offset; | |
319 | } | |
320 | } | |
321 | ||
8da3821b SR |
322 | # |
323 | # Step 2: find the sections and mcount call sites | |
324 | # | |
325 | open(IN, "$objdump -dr $inputfile|") || die "error running $objdump"; | |
326 | ||
8feff1ca SR |
327 | my $text; |
328 | ||
8da3821b SR |
329 | while (<IN>) { |
330 | # is it a section? | |
331 | if (/$section_regex/) { | |
34698bcb SR |
332 | |
333 | # Only record text sections that we know are safe | |
334 | if (defined($text_sections{$1})) { | |
335 | $read_function = 1; | |
336 | } else { | |
337 | $read_function = 0; | |
338 | } | |
8feff1ca SR |
339 | # print out any recorded offsets |
340 | update_funcs() if ($text_found); | |
341 | ||
342 | # reset all markers and arrays | |
8da3821b | 343 | $text_found = 0; |
8feff1ca SR |
344 | undef($ref_func); |
345 | undef(@offsets); | |
346 | ||
8da3821b SR |
347 | # section found, now is this a start of a function? |
348 | } elsif ($read_function && /$function_regex/) { | |
8da3821b | 349 | $text_found = 1; |
8feff1ca SR |
350 | $offset = hex $1; |
351 | $text = $2; | |
352 | ||
353 | # if this is either a local function or a weak function | |
354 | # keep looking for functions that are global that | |
355 | # we can use safely. | |
356 | if (!defined($locals{$text}) && !defined($weak{$text})) { | |
357 | $ref_func = $text; | |
358 | $read_function = 0; | |
359 | } else { | |
360 | # if we already have a function, and this is weak, skip it | |
361 | if (!defined($ref_func) || !defined($weak{$text})) { | |
362 | $ref_func = $text; | |
363 | } | |
8da3821b | 364 | } |
8feff1ca SR |
365 | } |
366 | ||
367 | # is this a call site to mcount? If so, record it to print later | |
368 | if ($text_found && /$mcount_regex/) { | |
369 | $offsets[$#offsets + 1] = hex $1; | |
8da3821b SR |
370 | } |
371 | } | |
372 | ||
8feff1ca SR |
373 | # dump out anymore offsets that may have been found |
374 | update_funcs() if ($text_found); | |
375 | ||
8da3821b SR |
376 | # If we did not find any mcount callers, we are done (do nothing). |
377 | if (!$opened) { | |
378 | exit(0); | |
379 | } | |
380 | ||
381 | close(FILE); | |
382 | ||
383 | # | |
384 | # Step 3: Compile the file that holds the list of call sites to mcount. | |
385 | # | |
386 | `$cc -o $mcount_o -c $mcount_s`; | |
387 | ||
388 | my @converts = keys %convert; | |
389 | ||
390 | # | |
391 | # Step 4: Do we have sections that started with local functions? | |
392 | # | |
393 | if ($#converts >= 0) { | |
394 | my $globallist = ""; | |
395 | my $locallist = ""; | |
396 | ||
397 | foreach my $con (@converts) { | |
398 | $globallist .= " --globalize-symbol $con"; | |
399 | $locallist .= " --localize-symbol $con"; | |
400 | } | |
401 | ||
402 | my $globalobj = $dirname . "/.tmp_gl_" . $filename; | |
403 | my $globalmix = $dirname . "/.tmp_mx_" . $filename; | |
404 | ||
405 | # | |
406 | # Step 5: set up each local function as a global | |
407 | # | |
408 | `$objcopy $globallist $inputfile $globalobj`; | |
409 | ||
410 | # | |
411 | # Step 6: Link the global version to our list. | |
412 | # | |
413 | `$ld -r $globalobj $mcount_o -o $globalmix`; | |
414 | ||
415 | # | |
416 | # Step 7: Convert the local functions back into local symbols | |
417 | # | |
418 | `$objcopy $locallist $globalmix $inputfile`; | |
419 | ||
420 | # Remove the temp files | |
421 | `$rm $globalobj $globalmix`; | |
422 | ||
423 | } else { | |
424 | ||
425 | my $mix = $dirname . "/.tmp_mx_" . $filename; | |
426 | ||
427 | # | |
428 | # Step 8: Link the object with our list of call sites object. | |
429 | # | |
430 | `$ld -r $inputfile $mcount_o -o $mix`; | |
431 | ||
432 | # | |
433 | # Step 9: Move the result back to the original object. | |
434 | # | |
435 | `$mv $mix $inputfile`; | |
436 | } | |
437 | ||
438 | # Clean up the temp files | |
439 | `$rm $mcount_o $mcount_s`; | |
440 | ||
441 | exit(0); |