7dbdee2e9a
Roland Dreier found that a section that contained only a weak function in one of the staging drivers and this caused recordmcount.pl to spit out a warning and fail. Although it is strange that a driver would have a weak function, and this function only be used in one place, it should not be something to make recordmcount.pl fail. This patch fixes the issue in a simple manner: if only weak functions exist in a section, then that section will not be recorded. Reported-by: Roland Dreier <rdreier@cisco.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
514 lines
14 KiB
Perl
Executable file
514 lines
14 KiB
Perl
Executable file
#!/usr/bin/perl -w
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# (c) 2008, Steven Rostedt <srostedt@redhat.com>
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# Licensed under the terms of the GNU GPL License version 2
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#
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# recordmcount.pl - makes a section called __mcount_loc that holds
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# all the offsets to the calls to mcount.
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#
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#
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# What we want to end up with is a section in vmlinux called
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# __mcount_loc that contains a list of pointers to all the
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# call sites in the kernel that call mcount. Later on boot up, the kernel
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# will read this list, save the locations and turn them into nops.
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# When tracing or profiling is later enabled, these locations will then
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# be converted back to pointers to some function.
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#
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# This is no easy feat. This script is called just after the original
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# object is compiled and before it is linked.
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#
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# The references to the call sites are offsets from the section of text
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# that the call site is in. Hence, all functions in a section that
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# has a call site to mcount, will have the offset from the beginning of
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# the section and not the beginning of the function.
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#
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# The trick is to find a way to record the beginning of the section.
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# The way we do this is to look at the first function in the section
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# which will also be the location of that section after final link.
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# e.g.
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#
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# .section ".sched.text", "ax"
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# .globl my_func
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# my_func:
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# [...]
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# call mcount (offset: 0x5)
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# [...]
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# ret
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# other_func:
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# [...]
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# call mcount (offset: 0x1b)
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# [...]
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#
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# Both relocation offsets for the mcounts in the above example will be
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# offset from .sched.text. If we make another file called tmp.s with:
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#
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# .section __mcount_loc
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# .quad my_func + 0x5
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# .quad my_func + 0x1b
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#
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# We can then compile this tmp.s into tmp.o, and link it to the original
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# object.
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#
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# But this gets hard if my_func is not globl (a static function).
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# In such a case we have:
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#
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# .section ".sched.text", "ax"
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# my_func:
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# [...]
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# call mcount (offset: 0x5)
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# [...]
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# ret
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# .globl my_func
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# other_func:
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# [...]
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# call mcount (offset: 0x1b)
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# [...]
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#
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# If we make the tmp.s the same as above, when we link together with
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# the original object, we will end up with two symbols for my_func:
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# one local, one global. After final compile, we will end up with
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# an undefined reference to my_func.
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#
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# Since local objects can reference local variables, we need to find
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# a way to make tmp.o reference the local objects of the original object
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# file after it is linked together. To do this, we convert the my_func
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# into a global symbol before linking tmp.o. Then after we link tmp.o
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# we will only have a single symbol for my_func that is global.
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# We can convert my_func back into a local symbol and we are done.
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#
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# Here are the steps we take:
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#
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# 1) Record all the local symbols by using 'nm'
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# 2) Use objdump to find all the call site offsets and sections for
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# mcount.
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# 3) Compile the list into its own object.
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# 4) Do we have to deal with local functions? If not, go to step 8.
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# 5) Make an object that converts these local functions to global symbols
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# with objcopy.
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# 6) Link together this new object with the list object.
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# 7) Convert the local functions back to local symbols and rename
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# the result as the original object.
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# End.
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# 8) Link the object with the list object.
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# 9) Move the result back to the original object.
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# End.
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#
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use strict;
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my $P = $0;
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$P =~ s@.*/@@g;
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my $V = '0.1';
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if ($#ARGV < 7) {
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print "usage: $P arch bits objdump objcopy cc ld nm rm mv is_module inputfile\n";
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print "version: $V\n";
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exit(1);
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}
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my ($arch, $bits, $objdump, $objcopy, $cc,
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$ld, $nm, $rm, $mv, $is_module, $inputfile) = @ARGV;
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# This file refers to mcount and shouldn't be ftraced, so lets' ignore it
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if ($inputfile eq "kernel/trace/ftrace.o") {
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exit(0);
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}
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# Acceptable sections to record.
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my %text_sections = (
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".text" => 1,
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".sched.text" => 1,
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".spinlock.text" => 1,
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".irqentry.text" => 1,
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);
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$objdump = "objdump" if ((length $objdump) == 0);
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$objcopy = "objcopy" if ((length $objcopy) == 0);
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$cc = "gcc" if ((length $cc) == 0);
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$ld = "ld" if ((length $ld) == 0);
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$nm = "nm" if ((length $nm) == 0);
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$rm = "rm" if ((length $rm) == 0);
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$mv = "mv" if ((length $mv) == 0);
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#print STDERR "running: $P '$arch' '$objdump' '$objcopy' '$cc' '$ld' " .
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# "'$nm' '$rm' '$mv' '$inputfile'\n";
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my %locals; # List of local (static) functions
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my %weak; # List of weak functions
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my %convert; # List of local functions used that needs conversion
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my $type;
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my $nm_regex; # Find the local functions (return function)
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my $section_regex; # Find the start of a section
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my $function_regex; # Find the name of a function
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# (return offset and func name)
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my $mcount_regex; # Find the call site to mcount (return offset)
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my $alignment; # The .align value to use for $mcount_section
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my $section_type; # Section header plus possible alignment command
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if ($arch eq "x86") {
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if ($bits == 64) {
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$arch = "x86_64";
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} else {
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$arch = "i386";
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}
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}
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#
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# We base the defaults off of i386, the other archs may
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# feel free to change them in the below if statements.
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#
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$nm_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\S+)";
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$section_regex = "Disassembly of section\\s+(\\S+):";
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$function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
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$mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount\$";
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$section_type = '@progbits';
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$type = ".long";
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if ($arch eq "x86_64") {
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$mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount([+-]0x[0-9a-zA-Z]+)?\$";
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$type = ".quad";
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$alignment = 8;
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# force flags for this arch
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$ld .= " -m elf_x86_64";
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$objdump .= " -M x86-64";
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$objcopy .= " -O elf64-x86-64";
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$cc .= " -m64";
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} elsif ($arch eq "i386") {
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$alignment = 4;
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# force flags for this arch
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$ld .= " -m elf_i386";
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$objdump .= " -M i386";
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$objcopy .= " -O elf32-i386";
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$cc .= " -m32";
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} elsif ($arch eq "s390" && $bits == 32) {
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$mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_390_32\\s+_mcount\$";
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$alignment = 4;
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$ld .= " -m elf_s390";
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$cc .= " -m31";
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} elsif ($arch eq "s390" && $bits == 64) {
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$mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_390_(PC|PLT)32DBL\\s+_mcount\\+0x2\$";
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$alignment = 8;
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$type = ".quad";
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$ld .= " -m elf64_s390";
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$cc .= " -m64";
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} elsif ($arch eq "sh") {
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$alignment = 2;
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# force flags for this arch
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$ld .= " -m shlelf_linux";
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$objcopy .= " -O elf32-sh-linux";
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$cc .= " -m32";
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} elsif ($arch eq "powerpc") {
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$nm_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\.?\\S+)";
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$function_regex = "^([0-9a-fA-F]+)\\s+<(\\.?.*?)>:";
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$mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s\\.?_mcount\$";
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if ($bits == 64) {
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$type = ".quad";
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}
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} elsif ($arch eq "arm") {
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$alignment = 2;
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$section_type = '%progbits';
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} elsif ($arch eq "ia64") {
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$mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
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$type = "data8";
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if ($is_module eq "0") {
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$cc .= " -mconstant-gp";
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}
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} elsif ($arch eq "sparc64") {
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# In the objdump output there are giblets like:
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# 0000000000000000 <igmp_net_exit-0x18>:
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# As there's some data blobs that get emitted into the
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# text section before the first instructions and the first
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# real symbols. We don't want to match that, so to combat
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# this we use '\w' so we'll match just plain symbol names,
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# and not those that also include hex offsets inside of the
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# '<>' brackets. Actually the generic function_regex setting
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# could safely use this too.
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$function_regex = "^([0-9a-fA-F]+)\\s+<(\\w*?)>:";
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# Sparc64 calls '_mcount' instead of plain 'mcount'.
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$mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
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$alignment = 8;
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$type = ".xword";
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$ld .= " -m elf64_sparc";
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$cc .= " -m64";
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$objcopy .= " -O elf64-sparc";
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} else {
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die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD";
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}
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my $text_found = 0;
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my $read_function = 0;
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my $opened = 0;
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my $mcount_section = "__mcount_loc";
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my $dirname;
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my $filename;
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my $prefix;
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my $ext;
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if ($inputfile =~ m,^(.*)/([^/]*)$,) {
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$dirname = $1;
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$filename = $2;
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} else {
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$dirname = ".";
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$filename = $inputfile;
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}
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if ($filename =~ m,^(.*)(\.\S),) {
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$prefix = $1;
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$ext = $2;
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} else {
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$prefix = $filename;
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$ext = "";
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}
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my $mcount_s = $dirname . "/.tmp_mc_" . $prefix . ".s";
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my $mcount_o = $dirname . "/.tmp_mc_" . $prefix . ".o";
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#
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# --globalize-symbols came out in 2.17, we must test the version
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# of objcopy, and if it is less than 2.17, then we can not
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# record local functions.
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my $use_locals = 01;
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my $local_warn_once = 0;
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my $found_version = 0;
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open (IN, "$objcopy --version |") || die "error running $objcopy";
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while (<IN>) {
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if (/objcopy.*\s(\d+)\.(\d+)/) {
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my $major = $1;
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my $minor = $2;
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$found_version = 1;
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if ($major < 2 ||
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($major == 2 && $minor < 17)) {
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$use_locals = 0;
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}
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last;
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}
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}
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close (IN);
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if (!$found_version) {
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print STDERR "WARNING: could not find objcopy version.\n" .
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"\tDisabling local function references.\n";
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}
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#
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# Step 1: find all the local (static functions) and weak symbols.
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# 't' is local, 'w/W' is weak (we never use a weak function)
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#
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open (IN, "$nm $inputfile|") || die "error running $nm";
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while (<IN>) {
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if (/$nm_regex/) {
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$locals{$1} = 1;
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} elsif (/^[0-9a-fA-F]+\s+([wW])\s+(\S+)/) {
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$weak{$2} = $1;
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}
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}
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close(IN);
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my @offsets; # Array of offsets of mcount callers
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my $ref_func; # reference function to use for offsets
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my $offset = 0; # offset of ref_func to section beginning
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##
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# update_funcs - print out the current mcount callers
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#
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# Go through the list of offsets to callers and write them to
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# the output file in a format that can be read by an assembler.
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#
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sub update_funcs
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{
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return if ($#offsets < 0);
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defined($ref_func) || die "No function to reference";
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# A section only had a weak function, to represent it.
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# Unfortunately, a weak function may be overwritten by another
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# function of the same name, making all these offsets incorrect.
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# To be safe, we simply print a warning and bail.
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if (defined $weak{$ref_func}) {
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print STDERR
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"$inputfile: WARNING: referencing weak function" .
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" $ref_func for mcount\n";
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return;
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}
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# is this function static? If so, note this fact.
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if (defined $locals{$ref_func}) {
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# only use locals if objcopy supports globalize-symbols
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if (!$use_locals) {
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return;
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}
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$convert{$ref_func} = 1;
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}
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# Loop through all the mcount caller offsets and print a reference
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# to the caller based from the ref_func.
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for (my $i=0; $i <= $#offsets; $i++) {
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if (!$opened) {
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open(FILE, ">$mcount_s") || die "can't create $mcount_s\n";
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$opened = 1;
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print FILE "\t.section $mcount_section,\"a\",$section_type\n";
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print FILE "\t.align $alignment\n" if (defined($alignment));
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}
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printf FILE "\t%s %s + %d\n", $type, $ref_func, $offsets[$i] - $offset;
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}
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}
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#
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# Step 2: find the sections and mcount call sites
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#
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open(IN, "$objdump -hdr $inputfile|") || die "error running $objdump";
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my $text;
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my $read_headers = 1;
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while (<IN>) {
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# is it a section?
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if (/$section_regex/) {
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$read_headers = 0;
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# Only record text sections that we know are safe
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if (defined($text_sections{$1})) {
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$read_function = 1;
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} else {
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$read_function = 0;
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}
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# print out any recorded offsets
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update_funcs() if (defined($ref_func));
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# reset all markers and arrays
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$text_found = 0;
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undef($ref_func);
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undef(@offsets);
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# section found, now is this a start of a function?
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} elsif ($read_function && /$function_regex/) {
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$text_found = 1;
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$text = $2;
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# if this is either a local function or a weak function
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# keep looking for functions that are global that
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# we can use safely.
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if (!defined($locals{$text}) && !defined($weak{$text})) {
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$ref_func = $text;
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$read_function = 0;
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$offset = hex $1;
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} else {
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# if we already have a function, and this is weak, skip it
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if (!defined($ref_func) && !defined($weak{$text}) &&
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# PPC64 can have symbols that start with .L and
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# gcc considers these special. Don't use them!
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$text !~ /^\.L/) {
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$ref_func = $text;
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$offset = hex $1;
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}
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}
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} elsif ($read_headers && /$mcount_section/) {
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#
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# Somehow the make process can execute this script on an
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# object twice. If it does, we would duplicate the mcount
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# section and it will cause the function tracer self test
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# to fail. Check if the mcount section exists, and if it does,
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# warn and exit.
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#
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print STDERR "ERROR: $mcount_section already in $inputfile\n" .
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"\tThis may be an indication that your build is corrupted.\n" .
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"\tDelete $inputfile and try again. If the same object file\n" .
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"\tstill causes an issue, then disable CONFIG_DYNAMIC_FTRACE.\n";
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exit(-1);
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}
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# is this a call site to mcount? If so, record it to print later
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if ($text_found && /$mcount_regex/) {
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$offsets[$#offsets + 1] = hex $1;
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}
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}
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# dump out anymore offsets that may have been found
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update_funcs() if (defined($ref_func));
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# If we did not find any mcount callers, we are done (do nothing).
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if (!$opened) {
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exit(0);
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}
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close(FILE);
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#
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# Step 3: Compile the file that holds the list of call sites to mcount.
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#
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`$cc -o $mcount_o -c $mcount_s`;
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my @converts = keys %convert;
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#
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# Step 4: Do we have sections that started with local functions?
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#
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if ($#converts >= 0) {
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my $globallist = "";
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my $locallist = "";
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foreach my $con (@converts) {
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$globallist .= " --globalize-symbol $con";
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$locallist .= " --localize-symbol $con";
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}
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my $globalobj = $dirname . "/.tmp_gl_" . $filename;
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my $globalmix = $dirname . "/.tmp_mx_" . $filename;
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#
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# Step 5: set up each local function as a global
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#
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`$objcopy $globallist $inputfile $globalobj`;
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#
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# Step 6: Link the global version to our list.
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#
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`$ld -r $globalobj $mcount_o -o $globalmix`;
|
|
|
|
#
|
|
# Step 7: Convert the local functions back into local symbols
|
|
#
|
|
`$objcopy $locallist $globalmix $inputfile`;
|
|
|
|
# Remove the temp files
|
|
`$rm $globalobj $globalmix`;
|
|
|
|
} else {
|
|
|
|
my $mix = $dirname . "/.tmp_mx_" . $filename;
|
|
|
|
#
|
|
# Step 8: Link the object with our list of call sites object.
|
|
#
|
|
`$ld -r $inputfile $mcount_o -o $mix`;
|
|
|
|
#
|
|
# Step 9: Move the result back to the original object.
|
|
#
|
|
`$mv $mix $inputfile`;
|
|
}
|
|
|
|
# Clean up the temp files
|
|
`$rm $mcount_o $mcount_s`;
|
|
|
|
exit(0);
|