xref: /openbmc/linux/scripts/recordmcount.pl (revision 6774def6)
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]+):.*\\s(mcount|__fentry__)\$";
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]+):.*\\s(mcount|__fentry__)([+-]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 == 64) {
245    $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_390_(PC|PLT)32DBL\\s+_mcount\\+0x2\$";
246    $mcount_adjust = -8;
247    $alignment = 8;
248    $type = ".quad";
249    $ld .= " -m elf64_s390";
250    $cc .= " -m64";
251
252} elsif ($arch eq "sh") {
253    $alignment = 2;
254
255    # force flags for this arch
256    $ld .= " -m shlelf_linux";
257    $objcopy .= " -O elf32-sh-linux";
258    $cc .= " -m32";
259
260} elsif ($arch eq "powerpc") {
261    $local_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\.?\\S+)";
262    $function_regex = "^([0-9a-fA-F]+)\\s+<(\\.?.*?)>:";
263    $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s\\.?_mcount\$";
264
265    if ($bits == 64) {
266	$type = ".quad";
267    }
268
269} elsif ($arch eq "arm") {
270    $alignment = 2;
271    $section_type = '%progbits';
272    $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_ARM_(CALL|PC24|THM_CALL)" .
273			"\\s+(__gnu_mcount_nc|mcount)\$";
274
275} elsif ($arch eq "arm64") {
276    $alignment = 3;
277    $section_type = '%progbits';
278    $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_AARCH64_CALL26\\s+_mcount\$";
279    $type = ".quad";
280} elsif ($arch eq "ia64") {
281    $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
282    $type = "data8";
283
284    if ($is_module eq "0") {
285        $cc .= " -mconstant-gp";
286    }
287} elsif ($arch eq "sparc64") {
288    # In the objdump output there are giblets like:
289    # 0000000000000000 <igmp_net_exit-0x18>:
290    # As there's some data blobs that get emitted into the
291    # text section before the first instructions and the first
292    # real symbols.  We don't want to match that, so to combat
293    # this we use '\w' so we'll match just plain symbol names,
294    # and not those that also include hex offsets inside of the
295    # '<>' brackets.  Actually the generic function_regex setting
296    # could safely use this too.
297    $function_regex = "^([0-9a-fA-F]+)\\s+<(\\w*?)>:";
298
299    # Sparc64 calls '_mcount' instead of plain 'mcount'.
300    $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
301
302    $alignment = 8;
303    $type = ".xword";
304    $ld .= " -m elf64_sparc";
305    $cc .= " -m64";
306    $objcopy .= " -O elf64-sparc";
307} elsif ($arch eq "mips") {
308    # To enable module support, we need to enable the -mlong-calls option
309    # of gcc for module, after using this option, we can not get the real
310    # offset of the calling to _mcount, but the offset of the lui
311    # instruction or the addiu one. herein, we record the address of the
312    # first one, and then we can replace this instruction by a branch
313    # instruction to jump over the profiling function to filter the
314    # indicated functions, or swith back to the lui instruction to trace
315    # them, which means dynamic tracing.
316    #
317    #       c:	3c030000 	lui	v1,0x0
318    #			c: R_MIPS_HI16	_mcount
319    #			c: R_MIPS_NONE	*ABS*
320    #			c: R_MIPS_NONE	*ABS*
321    #      10:	64630000 	daddiu	v1,v1,0
322    #			10: R_MIPS_LO16	_mcount
323    #			10: R_MIPS_NONE	*ABS*
324    #			10: R_MIPS_NONE	*ABS*
325    #      14:	03e0082d 	move	at,ra
326    #      18:	0060f809 	jalr	v1
327    #
328    # for the kernel:
329    #
330    #     10:   03e0082d        move    at,ra
331    #	  14:   0c000000        jal     0 <loongson_halt>
332    #                    14: R_MIPS_26   _mcount
333    #                    14: R_MIPS_NONE *ABS*
334    #                    14: R_MIPS_NONE *ABS*
335    #	 18:   00020021        nop
336    if ($is_module eq "0") {
337	    $mcount_regex = "^\\s*([0-9a-fA-F]+): R_MIPS_26\\s+_mcount\$";
338    } else {
339	    $mcount_regex = "^\\s*([0-9a-fA-F]+): R_MIPS_HI16\\s+_mcount\$";
340    }
341    $objdump .= " -Melf-trad".$endian."mips ";
342
343    if ($endian eq "big") {
344	    $endian = " -EB ";
345	    $ld .= " -melf".$bits."btsmip";
346    } else {
347	    $endian = " -EL ";
348	    $ld .= " -melf".$bits."ltsmip";
349    }
350
351    $cc .= " -mno-abicalls -fno-pic -mabi=" . $bits . $endian;
352    $ld .= $endian;
353
354    if ($bits == 64) {
355	    $function_regex =
356		"^([0-9a-fA-F]+)\\s+<(.|[^\$]L.*?|\$[^L].*?|[^\$][^L].*?)>:";
357	    $type = ".dword";
358    }
359} elsif ($arch eq "microblaze") {
360    # Microblaze calls '_mcount' instead of plain 'mcount'.
361    $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
362} elsif ($arch eq "blackfin") {
363    $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s__mcount\$";
364    $mcount_adjust = -4;
365} elsif ($arch eq "tilegx" || $arch eq "tile") {
366    # Default to the newer TILE-Gx architecture if only "tile" is given.
367    $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s__mcount\$";
368    $type = ".quad";
369    $alignment = 8;
370} else {
371    die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD";
372}
373
374my $text_found = 0;
375my $read_function = 0;
376my $opened = 0;
377my $mcount_section = "__mcount_loc";
378
379my $dirname;
380my $filename;
381my $prefix;
382my $ext;
383
384if ($inputfile =~ m,^(.*)/([^/]*)$,) {
385    $dirname = $1;
386    $filename = $2;
387} else {
388    $dirname = ".";
389    $filename = $inputfile;
390}
391
392if ($filename =~ m,^(.*)(\.\S),) {
393    $prefix = $1;
394    $ext = $2;
395} else {
396    $prefix = $filename;
397    $ext = "";
398}
399
400my $mcount_s = $dirname . "/.tmp_mc_" . $prefix . ".s";
401my $mcount_o = $dirname . "/.tmp_mc_" . $prefix . ".o";
402
403check_objcopy();
404
405#
406# Step 1: find all the local (static functions) and weak symbols.
407#         't' is local, 'w/W' is weak
408#
409open (IN, "$nm $inputfile|") || die "error running $nm";
410while (<IN>) {
411    if (/$local_regex/) {
412	$locals{$1} = 1;
413    } elsif (/$weak_regex/) {
414	$weak{$2} = $1;
415    }
416}
417close(IN);
418
419my @offsets;		# Array of offsets of mcount callers
420my $ref_func;		# reference function to use for offsets
421my $offset = 0;		# offset of ref_func to section beginning
422
423##
424# update_funcs - print out the current mcount callers
425#
426#  Go through the list of offsets to callers and write them to
427#  the output file in a format that can be read by an assembler.
428#
429sub update_funcs
430{
431    return unless ($ref_func and @offsets);
432
433    # Sanity check on weak function. A weak function may be overwritten by
434    # another function of the same name, making all these offsets incorrect.
435    if (defined $weak{$ref_func}) {
436	die "$inputfile: ERROR: referencing weak function" .
437	    " $ref_func for mcount\n";
438    }
439
440    # is this function static? If so, note this fact.
441    if (defined $locals{$ref_func}) {
442
443	# only use locals if objcopy supports globalize-symbols
444	if (!$can_use_local) {
445	    return;
446	}
447	$convert{$ref_func} = 1;
448    }
449
450    # Loop through all the mcount caller offsets and print a reference
451    # to the caller based from the ref_func.
452    if (!$opened) {
453	open(FILE, ">$mcount_s") || die "can't create $mcount_s\n";
454	$opened = 1;
455	print FILE "\t.section $mcount_section,\"a\",$section_type\n";
456	print FILE "\t.align $alignment\n" if (defined($alignment));
457    }
458    foreach my $cur_offset (@offsets) {
459	printf FILE "\t%s %s + %d\n", $type, $ref_func, $cur_offset - $offset;
460    }
461}
462
463#
464# Step 2: find the sections and mcount call sites
465#
466open(IN, "$objdump -hdr $inputfile|") || die "error running $objdump";
467
468my $text;
469
470
471# read headers first
472my $read_headers = 1;
473
474while (<IN>) {
475
476    if ($read_headers && /$mcount_section/) {
477	#
478	# Somehow the make process can execute this script on an
479	# object twice. If it does, we would duplicate the mcount
480	# section and it will cause the function tracer self test
481	# to fail. Check if the mcount section exists, and if it does,
482	# warn and exit.
483	#
484	print STDERR "ERROR: $mcount_section already in $inputfile\n" .
485	    "\tThis may be an indication that your build is corrupted.\n" .
486	    "\tDelete $inputfile and try again. If the same object file\n" .
487	    "\tstill causes an issue, then disable CONFIG_DYNAMIC_FTRACE.\n";
488	exit(-1);
489    }
490
491    # is it a section?
492    if (/$section_regex/) {
493	$read_headers = 0;
494
495	# Only record text sections that we know are safe
496	$read_function = defined($text_sections{$1});
497	# print out any recorded offsets
498	update_funcs();
499
500	# reset all markers and arrays
501	$text_found = 0;
502	undef($ref_func);
503	undef(@offsets);
504
505    # section found, now is this a start of a function?
506    } elsif ($read_function && /$function_regex/) {
507	$text_found = 1;
508	$text = $2;
509
510	# if this is either a local function or a weak function
511	# keep looking for functions that are global that
512	# we can use safely.
513	if (!defined($locals{$text}) && !defined($weak{$text})) {
514	    $ref_func = $text;
515	    $read_function = 0;
516	    $offset = hex $1;
517	} else {
518	    # if we already have a function, and this is weak, skip it
519	    if (!defined($ref_func) && !defined($weak{$text}) &&
520		 # PPC64 can have symbols that start with .L and
521		 # gcc considers these special. Don't use them!
522		 $text !~ /^\.L/) {
523		$ref_func = $text;
524		$offset = hex $1;
525	    }
526	}
527    }
528    # is this a call site to mcount? If so, record it to print later
529    if ($text_found && /$mcount_regex/) {
530	push(@offsets, (hex $1) + $mcount_adjust);
531    }
532}
533
534# dump out anymore offsets that may have been found
535update_funcs();
536
537# If we did not find any mcount callers, we are done (do nothing).
538if (!$opened) {
539    exit(0);
540}
541
542close(FILE);
543
544#
545# Step 3: Compile the file that holds the list of call sites to mcount.
546#
547`$cc -o $mcount_o -c $mcount_s`;
548
549my @converts = keys %convert;
550
551#
552# Step 4: Do we have sections that started with local functions?
553#
554if ($#converts >= 0) {
555    my $globallist = "";
556    my $locallist = "";
557
558    foreach my $con (@converts) {
559	$globallist .= " --globalize-symbol $con";
560	$locallist .= " --localize-symbol $con";
561    }
562
563    my $globalobj = $dirname . "/.tmp_gl_" . $filename;
564    my $globalmix = $dirname . "/.tmp_mx_" . $filename;
565
566    #
567    # Step 5: set up each local function as a global
568    #
569    `$objcopy $globallist $inputfile $globalobj`;
570
571    #
572    # Step 6: Link the global version to our list.
573    #
574    `$ld -r $globalobj $mcount_o -o $globalmix`;
575
576    #
577    # Step 7: Convert the local functions back into local symbols
578    #
579    `$objcopy $locallist $globalmix $inputfile`;
580
581    # Remove the temp files
582    `$rm $globalobj $globalmix`;
583
584} else {
585
586    my $mix = $dirname . "/.tmp_mx_" . $filename;
587
588    #
589    # Step 8: Link the object with our list of call sites object.
590    #
591    `$ld -r $inputfile $mcount_o -o $mix`;
592
593    #
594    # Step 9: Move the result back to the original object.
595    #
596    `$mv $mix $inputfile`;
597}
598
599# Clean up the temp files
600`$rm $mcount_o $mcount_s`;
601
602exit(0);
603