db24c7dcf4
Move the mcount section check to the beginning of the objdump read loop. This makes the code easier to follow since the search for the mcount section is performed first before the mcount callers are processed. Signed-off-by: Li Hong <lihong.hi@gmail.com> LKML-Reference: <20091028050523.GE30758@uhli> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
531 lines
15 KiB
Perl
Executable File
531 lines
15 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 this is that each object file will have a
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# section called __mcount_loc that will hold the list of pointers to mcount
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# callers. After final linking, the vmlinux will have within .init.data the
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# list of all callers to mcount between __start_mcount_loc and __stop_mcount_loc.
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# Later on boot up, the kernel will read this list, save the locations and turn
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# them into nops. When tracing or profiling is later enabled, these locations
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# will then 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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# When parse this object file using 'objdump', the references to the call
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# sites are offsets from the section that the call site is in. Hence, all
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# functions in a section that has a call site to mcount, will have the
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# offset from the beginning of the section and not the beginning of the
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# function.
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#
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# But where this section will reside finally in vmlinx is undetermined at
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# this point. So we can't use this kind of offsets to record the final
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# address of this call site.
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#
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# The trick is to change the call offset referring the start of a section to
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# referring a function symbol in this section. During the link step, 'ld' will
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# compute the final address according to the information we record.
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#
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# e.g.
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#
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# .section ".sched.text", "ax"
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# [...]
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# func1:
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# [...]
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# call mcount (offset: 0x10)
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# [...]
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# ret
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# .globl fun2
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# func2: (offset: 0x20)
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# [...]
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# [...]
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# ret
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# func3:
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# [...]
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# call mcount (offset: 0x30)
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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 choose global symbol func2 as a reference and
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# make another file called tmp.s with the new offsets:
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#
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# .section __mcount_loc
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# .quad func2 - 0x10
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# .quad func2 + 0x10
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#
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# We can then compile this tmp.s into tmp.o, and link it back to the original
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# object.
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#
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# In our algorithm, we will choose the first global function we meet in this
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# section as the reference. But this gets hard if there is no global functions
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# in this section. In such a case we have to select a local one. E.g. func1:
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#
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# .section ".sched.text", "ax"
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# func1:
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# [...]
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# call mcount (offset: 0x10)
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# [...]
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# ret
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# func2:
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# [...]
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# call mcount (offset: 0x20)
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# [...]
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# .section "other.section"
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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 func1:
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# one local, one global. After final compile, we will end up with
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# an undefined reference to func1 or a wrong reference to another global
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# func1 in other files.
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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 func1
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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 func1 that is global.
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# We can convert func1 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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# 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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#
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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 != 10) {
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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 =~ m,kernel/trace/ftrace\.o$,) {
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exit(0);
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}
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# Acceptable sections to record.
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my %text_sections = (
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".text" => 1,
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".sched.text" => 1,
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".spinlock.text" => 1,
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".irqentry.text" => 1,
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".text.unlikely" => 1,
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);
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$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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my $can_use_local = 0; # If we can use local function references
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##
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# check_objcopy - whether objcopy supports --globalize-symbols
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#
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# --globalize-symbols came out in 2.17, we must test the version
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# of objcopy, and if it is less than 2.17, then we can not
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# record local functions.
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sub check_objcopy
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{
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open (IN, "$objcopy --version |") or die "error running $objcopy";
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while (<IN>) {
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if (/objcopy.*\s(\d+)\.(\d+)/) {
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$can_use_local = 1 if ($1 > 2 || ($1 == 2 && $2 >= 17));
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last;
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}
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}
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close (IN);
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if (!$can_use_local) {
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print STDERR "WARNING: could not find objcopy version or version " .
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"is less than 2.17.\n" .
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"\tLocal function references is disabled.\n";
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}
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}
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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_" . $prefix . ".o";
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check_objcopy();
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#
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# Step 1: find all the local (static functions) and weak symbols.
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# 't' is local, 'w/W' is weak (we never use a weak function)
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#
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open (IN, "$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 (!$can_use_local) {
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return;
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}
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$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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# read headers first
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my $read_headers = 1;
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while (<IN>) {
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if ($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 $inputfile and try again. If the same object file\n" .
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"\tstill causes an issue, then disable CONFIG_DYNAMIC_FTRACE.\n";
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exit(-1);
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}
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# is it a section?
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if (/$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 $1;
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}
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}
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}
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# is this a call site to mcount? If so, record it to print later
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if ($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) {
|
|
$globallist .= " --globalize-symbol $con";
|
|
$locallist .= " --localize-symbol $con";
|
|
}
|
|
|
|
my $globalobj = $dirname . "/.tmp_gl_" . $filename;
|
|
my $globalmix = $dirname . "/.tmp_mx_" . $filename;
|
|
|
|
#
|
|
# Step 5: set up each local function as a global
|
|
#
|
|
`$objcopy $globallist $inputfile $globalobj`;
|
|
|
|
#
|
|
# Step 6: Link the global version to our list.
|
|
#
|
|
`$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);
|