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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: $V\n"; | |
106 | exit(1); | |
107 | } | |
108 | ||
109 | my ($arch, $objdump, $objcopy, $cc, $ld, $nm, $rm, $mv, $inputfile) = @ARGV; | |
110 | ||
111 | $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 | ||
8feff1ca SR |
122 | my %locals; # List of local (static) functions |
123 | my %weak; # List of weak functions | |
124 | my %convert; # List of local functions used that needs conversion | |
8da3821b SR |
125 | |
126 | my $type; | |
127 | my $section_regex; # Find the start of a section | |
8feff1ca SR |
128 | my $function_regex; # Find the name of a function |
129 | # (return offset and func name) | |
8da3821b SR |
130 | my $mcount_regex; # Find the call site to mcount (return offset) |
131 | ||
132 | if ($arch eq "x86_64") { | |
133 | $section_regex = "Disassembly of section"; | |
8feff1ca | 134 | $function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:"; |
8da3821b SR |
135 | $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount([+-]0x[0-9a-zA-Z]+)?\$"; |
136 | $type = ".quad"; | |
d74fcd1e SR |
137 | |
138 | # force flags for this arch | |
139 | $ld .= " -m elf_x86_64"; | |
140 | $objdump .= " -M x86-64"; | |
141 | $objcopy .= " -O elf64-x86-64"; | |
142 | $cc .= " -m64"; | |
143 | ||
8da3821b SR |
144 | } elsif ($arch eq "i386") { |
145 | $section_regex = "Disassembly of section"; | |
8feff1ca | 146 | $function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:"; |
8da3821b SR |
147 | $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount\$"; |
148 | $type = ".long"; | |
d74fcd1e SR |
149 | |
150 | # force flags for this arch | |
151 | $ld .= " -m elf_i386"; | |
152 | $objdump .= " -M i386"; | |
153 | $objcopy .= " -O elf32-i386"; | |
154 | $cc .= " -m32"; | |
155 | ||
8da3821b SR |
156 | } else { |
157 | die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD"; | |
158 | } | |
159 | ||
160 | my $text_found = 0; | |
161 | my $read_function = 0; | |
162 | my $opened = 0; | |
8da3821b SR |
163 | my $mcount_section = "__mcount_loc"; |
164 | ||
165 | my $dirname; | |
166 | my $filename; | |
167 | my $prefix; | |
168 | my $ext; | |
169 | ||
170 | if ($inputfile =~ m,^(.*)/([^/]*)$,) { | |
171 | $dirname = $1; | |
172 | $filename = $2; | |
173 | } else { | |
174 | $dirname = "."; | |
175 | $filename = $inputfile; | |
176 | } | |
177 | ||
178 | if ($filename =~ m,^(.*)(\.\S),) { | |
179 | $prefix = $1; | |
180 | $ext = $2; | |
181 | } else { | |
182 | $prefix = $filename; | |
183 | $ext = ""; | |
184 | } | |
185 | ||
186 | my $mcount_s = $dirname . "/.tmp_mc_" . $prefix . ".s"; | |
187 | my $mcount_o = $dirname . "/.tmp_mc_" . $prefix . ".o"; | |
188 | ||
189 | # | |
8feff1ca SR |
190 | # Step 1: find all the local (static functions) and weak symbols. |
191 | # 't' is local, 'w/W' is weak (we never use a weak function) | |
8da3821b SR |
192 | # |
193 | open (IN, "$nm $inputfile|") || die "error running $nm"; | |
194 | while (<IN>) { | |
195 | if (/^[0-9a-fA-F]+\s+t\s+(\S+)/) { | |
196 | $locals{$1} = 1; | |
8feff1ca SR |
197 | } elsif (/^[0-9a-fA-F]+\s+([wW])\s+(\S+)/) { |
198 | $weak{$2} = $1; | |
8da3821b SR |
199 | } |
200 | } | |
201 | close(IN); | |
202 | ||
8feff1ca SR |
203 | my @offsets; # Array of offsets of mcount callers |
204 | my $ref_func; # reference function to use for offsets | |
205 | my $offset = 0; # offset of ref_func to section beginning | |
206 | ||
207 | ## | |
208 | # update_funcs - print out the current mcount callers | |
209 | # | |
210 | # Go through the list of offsets to callers and write them to | |
211 | # the output file in a format that can be read by an assembler. | |
212 | # | |
213 | sub update_funcs | |
214 | { | |
215 | return if ($#offsets < 0); | |
216 | ||
217 | defined($ref_func) || die "No function to reference"; | |
218 | ||
219 | # A section only had a weak function, to represent it. | |
220 | # Unfortunately, a weak function may be overwritten by another | |
221 | # function of the same name, making all these offsets incorrect. | |
222 | # To be safe, we simply print a warning and bail. | |
223 | if (defined $weak{$ref_func}) { | |
224 | print STDERR | |
225 | "$inputfile: WARNING: referencing weak function" . | |
226 | " $ref_func for mcount\n"; | |
227 | return; | |
228 | } | |
229 | ||
230 | # is this function static? If so, note this fact. | |
231 | if (defined $locals{$ref_func}) { | |
232 | $convert{$ref_func} = 1; | |
233 | } | |
234 | ||
235 | # Loop through all the mcount caller offsets and print a reference | |
236 | # to the caller based from the ref_func. | |
237 | for (my $i=0; $i <= $#offsets; $i++) { | |
238 | if (!$opened) { | |
239 | open(FILE, ">$mcount_s") || die "can't create $mcount_s\n"; | |
240 | $opened = 1; | |
241 | print FILE "\t.section $mcount_section,\"a\",\@progbits\n"; | |
242 | } | |
243 | printf FILE "\t%s %s + %d\n", $type, $ref_func, $offsets[$i] - $offset; | |
244 | } | |
245 | } | |
246 | ||
8da3821b SR |
247 | # |
248 | # Step 2: find the sections and mcount call sites | |
249 | # | |
250 | open(IN, "$objdump -dr $inputfile|") || die "error running $objdump"; | |
251 | ||
8feff1ca SR |
252 | my $text; |
253 | ||
8da3821b SR |
254 | while (<IN>) { |
255 | # is it a section? | |
256 | if (/$section_regex/) { | |
257 | $read_function = 1; | |
8feff1ca SR |
258 | # print out any recorded offsets |
259 | update_funcs() if ($text_found); | |
260 | ||
261 | # reset all markers and arrays | |
8da3821b | 262 | $text_found = 0; |
8feff1ca SR |
263 | undef($ref_func); |
264 | undef(@offsets); | |
265 | ||
8da3821b SR |
266 | # section found, now is this a start of a function? |
267 | } elsif ($read_function && /$function_regex/) { | |
8da3821b | 268 | $text_found = 1; |
8feff1ca SR |
269 | $offset = hex $1; |
270 | $text = $2; | |
271 | ||
272 | # if this is either a local function or a weak function | |
273 | # keep looking for functions that are global that | |
274 | # we can use safely. | |
275 | if (!defined($locals{$text}) && !defined($weak{$text})) { | |
276 | $ref_func = $text; | |
277 | $read_function = 0; | |
278 | } else { | |
279 | # if we already have a function, and this is weak, skip it | |
280 | if (!defined($ref_func) || !defined($weak{$text})) { | |
281 | $ref_func = $text; | |
282 | } | |
8da3821b | 283 | } |
8feff1ca SR |
284 | } |
285 | ||
286 | # is this a call site to mcount? If so, record it to print later | |
287 | if ($text_found && /$mcount_regex/) { | |
288 | $offsets[$#offsets + 1] = hex $1; | |
8da3821b SR |
289 | } |
290 | } | |
291 | ||
8feff1ca SR |
292 | # dump out anymore offsets that may have been found |
293 | update_funcs() if ($text_found); | |
294 | ||
8da3821b SR |
295 | # If we did not find any mcount callers, we are done (do nothing). |
296 | if (!$opened) { | |
297 | exit(0); | |
298 | } | |
299 | ||
300 | close(FILE); | |
301 | ||
302 | # | |
303 | # Step 3: Compile the file that holds the list of call sites to mcount. | |
304 | # | |
305 | `$cc -o $mcount_o -c $mcount_s`; | |
306 | ||
307 | my @converts = keys %convert; | |
308 | ||
309 | # | |
310 | # Step 4: Do we have sections that started with local functions? | |
311 | # | |
312 | if ($#converts >= 0) { | |
313 | my $globallist = ""; | |
314 | my $locallist = ""; | |
315 | ||
316 | foreach my $con (@converts) { | |
317 | $globallist .= " --globalize-symbol $con"; | |
318 | $locallist .= " --localize-symbol $con"; | |
319 | } | |
320 | ||
321 | my $globalobj = $dirname . "/.tmp_gl_" . $filename; | |
322 | my $globalmix = $dirname . "/.tmp_mx_" . $filename; | |
323 | ||
324 | # | |
325 | # Step 5: set up each local function as a global | |
326 | # | |
327 | `$objcopy $globallist $inputfile $globalobj`; | |
328 | ||
329 | # | |
330 | # Step 6: Link the global version to our list. | |
331 | # | |
332 | `$ld -r $globalobj $mcount_o -o $globalmix`; | |
333 | ||
334 | # | |
335 | # Step 7: Convert the local functions back into local symbols | |
336 | # | |
337 | `$objcopy $locallist $globalmix $inputfile`; | |
338 | ||
339 | # Remove the temp files | |
340 | `$rm $globalobj $globalmix`; | |
341 | ||
342 | } else { | |
343 | ||
344 | my $mix = $dirname . "/.tmp_mx_" . $filename; | |
345 | ||
346 | # | |
347 | # Step 8: Link the object with our list of call sites object. | |
348 | # | |
349 | `$ld -r $inputfile $mcount_o -o $mix`; | |
350 | ||
351 | # | |
352 | # Step 9: Move the result back to the original object. | |
353 | # | |
354 | `$mv $mix $inputfile`; | |
355 | } | |
356 | ||
357 | # Clean up the temp files | |
358 | `$rm $mcount_o $mcount_s`; | |
359 | ||
360 | exit(0); |