Root/scripts/recordmcount.pl

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 this is that each object file will have a
10# section called __mcount_loc that will hold the list of pointers to mcount
11# callers. After final linking, the vmlinux will have within .init.data the
12# list of all callers to mcount between __start_mcount_loc and __stop_mcount_loc.
13# Later on boot up, the kernel will read this list, save the locations and turn
14# them into nops. When tracing or profiling is later enabled, these locations
15# will then be converted back to pointers to some function.
16#
17# This is no easy feat. This script is called just after the original
18# object is compiled and before it is linked.
19#
20# When parse this object file using 'objdump', the references to the call
21# sites are offsets from the section that the call site is in. Hence, all
22# functions in a section that has a call site to mcount, will have the
23# offset from the beginning of the section and not the beginning of the
24# function.
25#
26# But where this section will reside finally in vmlinx is undetermined at
27# this point. So we can't use this kind of offsets to record the final
28# address of this call site.
29#
30# The trick is to change the call offset referring the start of a section to
31# referring a function symbol in this section. During the link step, 'ld' will
32# compute the final address according to the information we record.
33#
34# e.g.
35#
36# .section ".sched.text", "ax"
37# [...]
38# func1:
39# [...]
40# call mcount (offset: 0x10)
41# [...]
42# ret
43# .globl fun2
44# func2: (offset: 0x20)
45# [...]
46# [...]
47# ret
48# func3:
49# [...]
50# call mcount (offset: 0x30)
51# [...]
52#
53# Both relocation offsets for the mcounts in the above example will be
54# offset from .sched.text. If we choose global symbol func2 as a reference and
55# make another file called tmp.s with the new offsets:
56#
57# .section __mcount_loc
58# .quad func2 - 0x10
59# .quad func2 + 0x10
60#
61# We can then compile this tmp.s into tmp.o, and link it back to the original
62# object.
63#
64# In our algorithm, we will choose the first global function we meet in this
65# section as the reference. But this gets hard if there is no global functions
66# in this section. In such a case we have to select a local one. E.g. func1:
67#
68# .section ".sched.text", "ax"
69# func1:
70# [...]
71# call mcount (offset: 0x10)
72# [...]
73# ret
74# func2:
75# [...]
76# call mcount (offset: 0x20)
77# [...]
78# .section "other.section"
79#
80# If we make the tmp.s the same as above, when we link together with
81# the original object, we will end up with two symbols for func1:
82# one local, one global. After final compile, we will end up with
83# an undefined reference to func1 or a wrong reference to another global
84# func1 in other files.
85#
86# Since local objects can reference local variables, we need to find
87# a way to make tmp.o reference the local objects of the original object
88# file after it is linked together. To do this, we convert func1
89# into a global symbol before linking tmp.o. Then after we link tmp.o
90# we will only have a single symbol for func1 that is global.
91# We can convert func1 back into a local symbol and we are done.
92#
93# Here are the steps we take:
94#
95# 1) Record all the local and weak symbols by using 'nm'
96# 2) Use objdump to find all the call site offsets and sections for
97# mcount.
98# 3) Compile the list into its own object.
99# 4) Do we have to deal with local functions? If not, go to step 8.
100# 5) Make an object that converts these local functions to global symbols
101# with objcopy.
102# 6) Link together this new object with the list object.
103# 7) Convert the local functions back to local symbols and rename
104# the result as the original object.
105# 8) Link the object with the list object.
106# 9) Move the result back to the original object.
107#
108
109use strict;
110
111my $P = $0;
112$P =~ s@.*/@@g;
113
114my $V = '0.1';
115
116if ($#ARGV != 11) {
117    print "usage: $P arch endian bits objdump objcopy cc ld nm rm mv is_module inputfile\n";
118    print "version: $V\n";
119    exit(1);
120}
121
122my ($arch, $endian, $bits, $objdump, $objcopy, $cc,
123    $ld, $nm, $rm, $mv, $is_module, $inputfile) = @ARGV;
124
125# This file refers to mcount and shouldn't be ftraced, so lets' ignore it
126if ($inputfile =~ m,kernel/trace/ftrace\.o$,) {
127    exit(0);
128}
129
130# Acceptable sections to record.
131my %text_sections = (
132     ".text" => 1,
133     ".ref.text" => 1,
134     ".sched.text" => 1,
135     ".spinlock.text" => 1,
136     ".irqentry.text" => 1,
137     ".kprobes.text" => 1,
138     ".text.unlikely" => 1,
139);
140
141# Note: we are nice to C-programmers here, thus we skip the '||='-idiom.
142$objdump = 'objdump' if (!$objdump);
143$objcopy = 'objcopy' if (!$objcopy);
144$cc = 'gcc' if (!$cc);
145$ld = 'ld' if (!$ld);
146$nm = 'nm' if (!$nm);
147$rm = 'rm' if (!$rm);
148$mv = 'mv' if (!$mv);
149
150#print STDERR "running: $P '$arch' '$objdump' '$objcopy' '$cc' '$ld' " .
151# "'$nm' '$rm' '$mv' '$inputfile'\n";
152
153my %locals; # List of local (static) functions
154my %weak; # List of weak functions
155my %convert; # List of local functions used that needs conversion
156
157my $type;
158my $local_regex; # Match a local function (return function)
159my $weak_regex; # Match a weak function (return function)
160my $section_regex; # Find the start of a section
161my $function_regex; # Find the name of a function
162            # (return offset and func name)
163my $mcount_regex; # Find the call site to mcount (return offset)
164my $mcount_adjust; # Address adjustment to mcount offset
165my $alignment; # The .align value to use for $mcount_section
166my $section_type; # Section header plus possible alignment command
167my $can_use_local = 0; # If we can use local function references
168
169# Shut up recordmcount if user has older objcopy
170my $quiet_recordmcount = ".tmp_quiet_recordmcount";
171my $print_warning = 1;
172$print_warning = 0 if ( -f $quiet_recordmcount);
173
174##
175# check_objcopy - whether objcopy supports --globalize-symbols
176#
177# --globalize-symbols came out in 2.17, we must test the version
178# of objcopy, and if it is less than 2.17, then we can not
179# record local functions.
180sub check_objcopy
181{
182    open (IN, "$objcopy --version |") or die "error running $objcopy";
183    while (<IN>) {
184    if (/objcopy.*\s(\d+)\.(\d+)/) {
185        $can_use_local = 1 if ($1 > 2 || ($1 == 2 && $2 >= 17));
186        last;
187    }
188    }
189    close (IN);
190
191    if (!$can_use_local && $print_warning) {
192    print STDERR "WARNING: could not find objcopy version or version " .
193        "is less than 2.17.\n" .
194        "\tLocal function references are disabled.\n";
195    open (QUIET, ">$quiet_recordmcount");
196    printf QUIET "Disables the warning from recordmcount.pl\n";
197    close QUIET;
198    }
199}
200
201if ($arch =~ /(x86(_64)?)|(i386)/) {
202    if ($bits == 64) {
203    $arch = "x86_64";
204    } else {
205    $arch = "i386";
206    }
207}
208
209#
210# We base the defaults off of i386, the other archs may
211# feel free to change them in the below if statements.
212#
213$local_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\S+)";
214$weak_regex = "^[0-9a-fA-F]+\\s+([wW])\\s+(\\S+)";
215$section_regex = "Disassembly of section\\s+(\\S+):";
216$function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
217$mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount\$";
218$section_type = '@progbits';
219$mcount_adjust = 0;
220$type = ".long";
221
222if ($arch eq "x86_64") {
223    $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount([+-]0x[0-9a-zA-Z]+)?\$";
224    $type = ".quad";
225    $alignment = 8;
226    $mcount_adjust = -1;
227
228    # force flags for this arch
229    $ld .= " -m elf_x86_64";
230    $objdump .= " -M x86-64";
231    $objcopy .= " -O elf64-x86-64";
232    $cc .= " -m64";
233
234} elsif ($arch eq "i386") {
235    $alignment = 4;
236    $mcount_adjust = -1;
237
238    # force flags for this arch
239    $ld .= " -m elf_i386";
240    $objdump .= " -M i386";
241    $objcopy .= " -O elf32-i386";
242    $cc .= " -m32";
243
244} elsif ($arch eq "s390" && $bits == 32) {
245    $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_390_32\\s+_mcount\$";
246    $mcount_adjust = -4;
247    $alignment = 4;
248    $ld .= " -m elf_s390";
249    $cc .= " -m31";
250
251} elsif ($arch eq "s390" && $bits == 64) {
252    $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_390_(PC|PLT)32DBL\\s+_mcount\\+0x2\$";
253    $mcount_adjust = -8;
254    $alignment = 8;
255    $type = ".quad";
256    $ld .= " -m elf64_s390";
257    $cc .= " -m64";
258
259} elsif ($arch eq "sh") {
260    $alignment = 2;
261
262    # force flags for this arch
263    $ld .= " -m shlelf_linux";
264    $objcopy .= " -O elf32-sh-linux";
265    $cc .= " -m32";
266
267} elsif ($arch eq "powerpc") {
268    $local_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\.?\\S+)";
269    $function_regex = "^([0-9a-fA-F]+)\\s+<(\\.?.*?)>:";
270    $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s\\.?_mcount\$";
271
272    if ($bits == 64) {
273    $type = ".quad";
274    }
275
276} elsif ($arch eq "arm") {
277    $alignment = 2;
278    $section_type = '%progbits';
279    $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_ARM_(CALL|PC24|THM_CALL)" .
280            "\\s+(__gnu_mcount_nc|mcount)\$";
281
282} elsif ($arch eq "ia64") {
283    $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
284    $type = "data8";
285
286    if ($is_module eq "0") {
287        $cc .= " -mconstant-gp";
288    }
289} elsif ($arch eq "sparc64") {
290    # In the objdump output there are giblets like:
291    # 0000000000000000 <igmp_net_exit-0x18>:
292    # As there's some data blobs that get emitted into the
293    # text section before the first instructions and the first
294    # real symbols. We don't want to match that, so to combat
295    # this we use '\w' so we'll match just plain symbol names,
296    # and not those that also include hex offsets inside of the
297    # '<>' brackets. Actually the generic function_regex setting
298    # could safely use this too.
299    $function_regex = "^([0-9a-fA-F]+)\\s+<(\\w*?)>:";
300
301    # Sparc64 calls '_mcount' instead of plain 'mcount'.
302    $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
303
304    $alignment = 8;
305    $type = ".xword";
306    $ld .= " -m elf64_sparc";
307    $cc .= " -m64";
308    $objcopy .= " -O elf64-sparc";
309} elsif ($arch eq "mips") {
310    # To enable module support, we need to enable the -mlong-calls option
311    # of gcc for module, after using this option, we can not get the real
312    # offset of the calling to _mcount, but the offset of the lui
313    # instruction or the addiu one. herein, we record the address of the
314    # first one, and then we can replace this instruction by a branch
315    # instruction to jump over the profiling function to filter the
316    # indicated functions, or swith back to the lui instruction to trace
317    # them, which means dynamic tracing.
318    #
319    # c: 3c030000 lui v1,0x0
320    # c: R_MIPS_HI16 _mcount
321    # c: R_MIPS_NONE *ABS*
322    # c: R_MIPS_NONE *ABS*
323    # 10: 64630000 daddiu v1,v1,0
324    # 10: R_MIPS_LO16 _mcount
325    # 10: R_MIPS_NONE *ABS*
326    # 10: R_MIPS_NONE *ABS*
327    # 14: 03e0082d move at,ra
328    # 18: 0060f809 jalr v1
329    #
330    # for the kernel:
331    #
332    # 10: 03e0082d move at,ra
333    # 14: 0c000000 jal 0 <loongson_halt>
334    # 14: R_MIPS_26 _mcount
335    # 14: R_MIPS_NONE *ABS*
336    # 14: R_MIPS_NONE *ABS*
337    # 18: 00020021 nop
338    if ($is_module eq "0") {
339        $mcount_regex = "^\\s*([0-9a-fA-F]+): R_MIPS_26\\s+_mcount\$";
340    } else {
341        $mcount_regex = "^\\s*([0-9a-fA-F]+): R_MIPS_HI16\\s+_mcount\$";
342    }
343    $objdump .= " -Melf-trad".$endian."mips ";
344
345    if ($endian eq "big") {
346        $endian = " -EB ";
347        $ld .= " -melf".$bits."btsmip";
348    } else {
349        $endian = " -EL ";
350        $ld .= " -melf".$bits."ltsmip";
351    }
352
353    $cc .= " -mno-abicalls -fno-pic -mabi=" . $bits . $endian;
354    $ld .= $endian;
355
356    if ($bits == 64) {
357        $function_regex =
358        "^([0-9a-fA-F]+)\\s+<(.|[^\$]L.*?|\$[^L].*?|[^\$][^L].*?)>:";
359        $type = ".dword";
360    }
361} elsif ($arch eq "microblaze") {
362    # Microblaze calls '_mcount' instead of plain 'mcount'.
363    $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
364} elsif ($arch eq "blackfin") {
365    $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s__mcount\$";
366    $mcount_adjust = -4;
367} elsif ($arch eq "tilegx") {
368    $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s__mcount\$";
369    $type = ".quad";
370    $alignment = 8;
371} else {
372    die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD";
373}
374
375my $text_found = 0;
376my $read_function = 0;
377my $opened = 0;
378my $mcount_section = "__mcount_loc";
379
380my $dirname;
381my $filename;
382my $prefix;
383my $ext;
384
385if ($inputfile =~ m,^(.*)/([^/]*)$,) {
386    $dirname = $1;
387    $filename = $2;
388} else {
389    $dirname = ".";
390    $filename = $inputfile;
391}
392
393if ($filename =~ m,^(.*)(\.\S),) {
394    $prefix = $1;
395    $ext = $2;
396} else {
397    $prefix = $filename;
398    $ext = "";
399}
400
401my $mcount_s = $dirname . "/.tmp_mc_" . $prefix . ".s";
402my $mcount_o = $dirname . "/.tmp_mc_" . $prefix . ".o";
403
404check_objcopy();
405
406#
407# Step 1: find all the local (static functions) and weak symbols.
408# 't' is local, 'w/W' is weak
409#
410open (IN, "$nm $inputfile|") || die "error running $nm";
411while (<IN>) {
412    if (/$local_regex/) {
413    $locals{$1} = 1;
414    } elsif (/$weak_regex/) {
415    $weak{$2} = $1;
416    }
417}
418close(IN);
419
420my @offsets; # Array of offsets of mcount callers
421my $ref_func; # reference function to use for offsets
422my $offset = 0; # offset of ref_func to section beginning
423
424##
425# update_funcs - print out the current mcount callers
426#
427# Go through the list of offsets to callers and write them to
428# the output file in a format that can be read by an assembler.
429#
430sub update_funcs
431{
432    return unless ($ref_func and @offsets);
433
434    # Sanity check on weak function. A weak function may be overwritten by
435    # another function of the same name, making all these offsets incorrect.
436    if (defined $weak{$ref_func}) {
437    die "$inputfile: ERROR: referencing weak function" .
438        " $ref_func for mcount\n";
439    }
440
441    # is this function static? If so, note this fact.
442    if (defined $locals{$ref_func}) {
443
444    # only use locals if objcopy supports globalize-symbols
445    if (!$can_use_local) {
446        return;
447    }
448    $convert{$ref_func} = 1;
449    }
450
451    # Loop through all the mcount caller offsets and print a reference
452    # to the caller based from the ref_func.
453    if (!$opened) {
454    open(FILE, ">$mcount_s") || die "can't create $mcount_s\n";
455    $opened = 1;
456    print FILE "\t.section $mcount_section,\"a\",$section_type\n";
457    print FILE "\t.align $alignment\n" if (defined($alignment));
458    }
459    foreach my $cur_offset (@offsets) {
460    printf FILE "\t%s %s + %d\n", $type, $ref_func, $cur_offset - $offset;
461    }
462}
463
464#
465# Step 2: find the sections and mcount call sites
466#
467open(IN, "$objdump -hdr $inputfile|") || die "error running $objdump";
468
469my $text;
470
471
472# read headers first
473my $read_headers = 1;
474
475while (<IN>) {
476
477    if ($read_headers && /$mcount_section/) {
478    #
479    # Somehow the make process can execute this script on an
480    # object twice. If it does, we would duplicate the mcount
481    # section and it will cause the function tracer self test
482    # to fail. Check if the mcount section exists, and if it does,
483    # warn and exit.
484    #
485    print STDERR "ERROR: $mcount_section already in $inputfile\n" .
486        "\tThis may be an indication that your build is corrupted.\n" .
487        "\tDelete $inputfile and try again. If the same object file\n" .
488        "\tstill causes an issue, then disable CONFIG_DYNAMIC_FTRACE.\n";
489    exit(-1);
490    }
491
492    # is it a section?
493    if (/$section_regex/) {
494    $read_headers = 0;
495
496    # Only record text sections that we know are safe
497    $read_function = defined($text_sections{$1});
498    # print out any recorded offsets
499    update_funcs();
500
501    # reset all markers and arrays
502    $text_found = 0;
503    undef($ref_func);
504    undef(@offsets);
505
506    # section found, now is this a start of a function?
507    } elsif ($read_function && /$function_regex/) {
508    $text_found = 1;
509    $text = $2;
510
511    # if this is either a local function or a weak function
512    # keep looking for functions that are global that
513    # we can use safely.
514    if (!defined($locals{$text}) && !defined($weak{$text})) {
515        $ref_func = $text;
516        $read_function = 0;
517        $offset = hex $1;
518    } else {
519        # if we already have a function, and this is weak, skip it
520        if (!defined($ref_func) && !defined($weak{$text}) &&
521         # PPC64 can have symbols that start with .L and
522         # gcc considers these special. Don't use them!
523         $text !~ /^\.L/) {
524        $ref_func = $text;
525        $offset = hex $1;
526        }
527    }
528    }
529    # is this a call site to mcount? If so, record it to print later
530    if ($text_found && /$mcount_regex/) {
531    push(@offsets, (hex $1) + $mcount_adjust);
532    }
533}
534
535# dump out anymore offsets that may have been found
536update_funcs();
537
538# If we did not find any mcount callers, we are done (do nothing).
539if (!$opened) {
540    exit(0);
541}
542
543close(FILE);
544
545#
546# Step 3: Compile the file that holds the list of call sites to mcount.
547#
548`$cc -o $mcount_o -c $mcount_s`;
549
550my @converts = keys %convert;
551
552#
553# Step 4: Do we have sections that started with local functions?
554#
555if ($#converts >= 0) {
556    my $globallist = "";
557    my $locallist = "";
558
559    foreach my $con (@converts) {
560    $globallist .= " --globalize-symbol $con";
561    $locallist .= " --localize-symbol $con";
562    }
563
564    my $globalobj = $dirname . "/.tmp_gl_" . $filename;
565    my $globalmix = $dirname . "/.tmp_mx_" . $filename;
566
567    #
568    # Step 5: set up each local function as a global
569    #
570    `$objcopy $globallist $inputfile $globalobj`;
571
572    #
573    # Step 6: Link the global version to our list.
574    #
575    `$ld -r $globalobj $mcount_o -o $globalmix`;
576
577    #
578    # Step 7: Convert the local functions back into local symbols
579    #
580    `$objcopy $locallist $globalmix $inputfile`;
581
582    # Remove the temp files
583    `$rm $globalobj $globalmix`;
584
585} else {
586
587    my $mix = $dirname . "/.tmp_mx_" . $filename;
588
589    #
590    # Step 8: Link the object with our list of call sites object.
591    #
592    `$ld -r $inputfile $mcount_o -o $mix`;
593
594    #
595    # Step 9: Move the result back to the original object.
596    #
597    `$mv $mix $inputfile`;
598}
599
600# Clean up the temp files
601`$rm $mcount_o $mcount_s`;
602
603exit(0);
604

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jz-3.5
jz-3.6
jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master

Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9



interactive