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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; | |
133 | my $section_regex; # Find the start of a section | |
8feff1ca SR |
134 | my $function_regex; # Find the name of a function |
135 | # (return offset and func name) | |
8da3821b | 136 | my $mcount_regex; # Find the call site to mcount (return offset) |
7d5222a6 | 137 | my $alignment; # The .align value to use for $mcount_section |
8da3821b | 138 | |
dce9d18a SR |
139 | if ($arch eq "x86") { |
140 | if ($bits == 64) { | |
141 | $arch = "x86_64"; | |
142 | } else { | |
143 | $arch = "i386"; | |
144 | } | |
145 | } | |
146 | ||
8da3821b | 147 | if ($arch eq "x86_64") { |
34698bcb | 148 | $section_regex = "Disassembly of section\\s+(\\S+):"; |
8feff1ca | 149 | $function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:"; |
8da3821b SR |
150 | $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount([+-]0x[0-9a-zA-Z]+)?\$"; |
151 | $type = ".quad"; | |
7d5222a6 | 152 | $alignment = 8; |
d74fcd1e SR |
153 | |
154 | # force flags for this arch | |
155 | $ld .= " -m elf_x86_64"; | |
156 | $objdump .= " -M x86-64"; | |
157 | $objcopy .= " -O elf64-x86-64"; | |
158 | $cc .= " -m64"; | |
159 | ||
8da3821b | 160 | } elsif ($arch eq "i386") { |
34698bcb | 161 | $section_regex = "Disassembly of section\\s+(\\S+):"; |
8feff1ca | 162 | $function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:"; |
8da3821b SR |
163 | $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount\$"; |
164 | $type = ".long"; | |
7d5222a6 | 165 | $alignment = 4; |
d74fcd1e SR |
166 | |
167 | # force flags for this arch | |
168 | $ld .= " -m elf_i386"; | |
169 | $objdump .= " -M i386"; | |
170 | $objcopy .= " -O elf32-i386"; | |
171 | $cc .= " -m32"; | |
172 | ||
0da85c09 MF |
173 | } elsif ($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 | ||
8da3821b SR |
184 | } else { |
185 | die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD"; | |
186 | } | |
187 | ||
188 | my $text_found = 0; | |
189 | my $read_function = 0; | |
190 | my $opened = 0; | |
8da3821b SR |
191 | my $mcount_section = "__mcount_loc"; |
192 | ||
193 | my $dirname; | |
194 | my $filename; | |
195 | my $prefix; | |
196 | my $ext; | |
197 | ||
198 | if ($inputfile =~ m,^(.*)/([^/]*)$,) { | |
199 | $dirname = $1; | |
200 | $filename = $2; | |
201 | } else { | |
202 | $dirname = "."; | |
203 | $filename = $inputfile; | |
204 | } | |
205 | ||
206 | if ($filename =~ m,^(.*)(\.\S),) { | |
207 | $prefix = $1; | |
208 | $ext = $2; | |
209 | } else { | |
210 | $prefix = $filename; | |
211 | $ext = ""; | |
212 | } | |
213 | ||
214 | my $mcount_s = $dirname . "/.tmp_mc_" . $prefix . ".s"; | |
215 | my $mcount_o = $dirname . "/.tmp_mc_" . $prefix . ".o"; | |
216 | ||
f2f8458e SR |
217 | # |
218 | # --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. | |
221 | my $use_locals = 01; | |
222 | my $local_warn_once = 0; | |
223 | my $found_version = 0; | |
224 | ||
225 | open (IN, "$objcopy --version |") || die "error running $objcopy"; | |
226 | while (<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 | $use_locals = 0; | |
235 | } | |
236 | last; | |
237 | } | |
238 | } | |
239 | close (IN); | |
240 | ||
241 | if (!$found_version) { | |
242 | print STDERR "WARNING: could not find objcopy version.\n" . | |
243 | "\tDisabling local function references.\n"; | |
244 | } | |
245 | ||
246 | ||
8da3821b | 247 | # |
8feff1ca SR |
248 | # 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) | |
8da3821b SR |
250 | # |
251 | open (IN, "$nm $inputfile|") || die "error running $nm"; | |
252 | while (<IN>) { | |
253 | if (/^[0-9a-fA-F]+\s+t\s+(\S+)/) { | |
254 | $locals{$1} = 1; | |
8feff1ca SR |
255 | } elsif (/^[0-9a-fA-F]+\s+([wW])\s+(\S+)/) { |
256 | $weak{$2} = $1; | |
8da3821b SR |
257 | } |
258 | } | |
259 | close(IN); | |
260 | ||
8feff1ca SR |
261 | my @offsets; # Array of offsets of mcount callers |
262 | my $ref_func; # reference function to use for offsets | |
263 | my $offset = 0; # offset of ref_func to section beginning | |
264 | ||
265 | ## | |
266 | # update_funcs - print out the current mcount callers | |
267 | # | |
268 | # Go through the list of offsets to callers and write them to | |
269 | # the output file in a format that can be read by an assembler. | |
270 | # | |
271 | sub update_funcs | |
272 | { | |
273 | return if ($#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}) { | |
f2f8458e SR |
290 | |
291 | # only use locals if objcopy supports globalize-symbols | |
292 | if (!$use_locals) { | |
f2f8458e SR |
293 | return; |
294 | } | |
8feff1ca SR |
295 | $convert{$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"; | |
7d5222a6 | 305 | print FILE "\t.align $alignment\n"; |
8feff1ca SR |
306 | } |
307 | printf FILE "\t%s %s + %d\n", $type, $ref_func, $offsets[$i] - $offset; | |
308 | } | |
309 | } | |
310 | ||
8da3821b SR |
311 | # |
312 | # Step 2: find the sections and mcount call sites | |
313 | # | |
314 | open(IN, "$objdump -dr $inputfile|") || die "error running $objdump"; | |
315 | ||
8feff1ca SR |
316 | my $text; |
317 | ||
8da3821b SR |
318 | while (<IN>) { |
319 | # is it a section? | |
320 | if (/$section_regex/) { | |
34698bcb SR |
321 | |
322 | # Only record text sections that we know are safe | |
323 | if (defined($text_sections{$1})) { | |
324 | $read_function = 1; | |
325 | } else { | |
326 | $read_function = 0; | |
327 | } | |
8feff1ca SR |
328 | # print out any recorded offsets |
329 | update_funcs() if ($text_found); | |
330 | ||
331 | # reset all markers and arrays | |
8da3821b | 332 | $text_found = 0; |
8feff1ca SR |
333 | undef($ref_func); |
334 | undef(@offsets); | |
335 | ||
8da3821b SR |
336 | # section found, now is this a start of a function? |
337 | } elsif ($read_function && /$function_regex/) { | |
8da3821b | 338 | $text_found = 1; |
8feff1ca SR |
339 | $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 = $text; | |
352 | } | |
8da3821b | 353 | } |
8feff1ca SR |
354 | } |
355 | ||
356 | # is this a call site to mcount? If so, record it to print later | |
357 | if ($text_found && /$mcount_regex/) { | |
358 | $offsets[$#offsets + 1] = hex $1; | |
8da3821b SR |
359 | } |
360 | } | |
361 | ||
8feff1ca SR |
362 | # dump out anymore offsets that may have been found |
363 | update_funcs() if ($text_found); | |
364 | ||
8da3821b SR |
365 | # If we did not find any mcount callers, we are done (do nothing). |
366 | if (!$opened) { | |
367 | exit(0); | |
368 | } | |
369 | ||
370 | close(FILE); | |
371 | ||
372 | # | |
373 | # Step 3: Compile the file that holds the list of call sites to mcount. | |
374 | # | |
375 | `$cc -o $mcount_o -c $mcount_s`; | |
376 | ||
377 | my @converts = keys %convert; | |
378 | ||
379 | # | |
380 | # Step 4: Do we have sections that started with local functions? | |
381 | # | |
382 | if ($#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 | ||
430 | exit(0); |