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Diffstat (limited to 'scripts/recordmcount.pl')
| -rwxr-xr-x | scripts/recordmcount.pl | 280 |
1 files changed, 280 insertions, 0 deletions
diff --git a/scripts/recordmcount.pl b/scripts/recordmcount.pl new file mode 100755 index 00000000000..44b4b23e91b --- /dev/null +++ b/scripts/recordmcount.pl @@ -0,0 +1,280 @@ +#!/usr/bin/perl -w +# (c) 2008, Steven Rostedt <srostedt@redhat.com> +# Licensed under the terms of the GNU GPL License version 2 +# +# recordmcount.pl - makes a section called __mcount_loc that holds +# all the offsets to the calls to mcount. +# +# +# What we want to end up with is a section in vmlinux called +# __mcount_loc that contains a list of pointers to all the +# call sites in the kernel that call mcount. Later on boot up, the kernel +# will read this list, save the locations and turn them into nops. +# When tracing or profiling is later enabled, these locations will then +# be converted back to pointers to some function. +# +# This is no easy feat. This script is called just after the original +# object is compiled and before it is linked. +# +# The references to the call sites are offsets from the section of text +# that the call site is in. Hence, all functions in a section that +# has a call site to mcount, will have the offset from the beginning of +# the section and not the beginning of the function. +# +# The trick is to find a way to record the beginning of the section. +# The way we do this is to look at the first function in the section +# which will also be the location of that section after final link. +# e.g. +# +# .section ".text.sched" +# .globl my_func +# my_func: +# [...] +# call mcount (offset: 0x5) +# [...] +# ret +# other_func: +# [...] +# call mcount (offset: 0x1b) +# [...] +# +# Both relocation offsets for the mcounts in the above example will be +# offset from .text.sched. If we make another file called tmp.s with: +# +# .section __mcount_loc +# .quad my_func + 0x5 +# .quad my_func + 0x1b +# +# We can then compile this tmp.s into tmp.o, and link it to the original +# object. +# +# But this gets hard if my_func is not globl (a static function). +# In such a case we have: +# +# .section ".text.sched" +# my_func: +# [...] +# call mcount (offset: 0x5) +# [...] +# ret +# .globl my_func +# other_func: +# [...] +# call mcount (offset: 0x1b) +# [...] +# +# If we make the tmp.s the same as above, when we link together with +# the original object, we will end up with two symbols for my_func: +# one local, one global. After final compile, we will end up with +# an undefined reference to my_func. +# +# Since local objects can reference local variables, we need to find +# a way to make tmp.o reference the local objects of the original object +# file after it is linked together. To do this, we convert the my_func +# into a global symbol before linking tmp.o. Then after we link tmp.o +# we will only have a single symbol for my_func that is global. +# We can convert my_func back into a local symbol and we are done. +# +# Here are the steps we take: +# +# 1) Record all the local symbols by using 'nm' +# 2) Use objdump to find all the call site offsets and sections for +# mcount. +# 3) Compile the list into its own object. +# 4) Do we have to deal with local functions? If not, go to step 8. +# 5) Make an object that converts these local functions to global symbols +# with objcopy. +# 6) Link together this new object with the list object. +# 7) Convert the local functions back to local symbols and rename +# the result as the original object. +# End. +# 8) Link the object with the list object. +# 9) Move the result back to the original object. +# End. +# + +use strict; + +my $P = $0; +$P =~ s@.*/@@g; + +my $V = '0.1'; + +if ($#ARGV < 6) { + print "usage: $P arch objdump objcopy cc ld nm rm mv inputfile\n"; + print "version: $V\n"; + exit(1); +} + +my ($arch, $objdump, $objcopy, $cc, $ld, $nm, $rm, $mv, $inputfile) = @ARGV; + +$objdump = "objdump" if ((length $objdump) == 0); +$objcopy = "objcopy" if ((length $objcopy) == 0); +$cc = "gcc" if ((length $cc) == 0); +$ld = "ld" if ((length $ld) == 0); +$nm = "nm" if ((length $nm) == 0); +$rm = "rm" if ((length $rm) == 0); +$mv = "mv" if ((length $mv) == 0); + +#print STDERR "running: $P '$arch' '$objdump' '$objcopy' '$cc' '$ld' " . +# "'$nm' '$rm' '$mv' '$inputfile'\n"; + +my %locals; +my %convert; + +my $type; +my $section_regex; # Find the start of a section +my $function_regex; # Find the name of a function (return func name) +my $mcount_regex; # Find the call site to mcount (return offset) + +if ($arch eq "x86_64") { + $section_regex = "Disassembly of section"; + $function_regex = "<(.*?)>:"; + $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount([+-]0x[0-9a-zA-Z]+)?\$"; + $type = ".quad"; +} elsif ($arch eq "i386") { + $section_regex = "Disassembly of section"; + $function_regex = "<(.*?)>:"; + $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount\$"; + $type = ".long"; +} else { + die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD"; +} + +my $text_found = 0; +my $read_function = 0; +my $opened = 0; +my $text = ""; +my $mcount_section = "__mcount_loc"; + +my $dirname; +my $filename; +my $prefix; +my $ext; + +if ($inputfile =~ m,^(.*)/([^/]*)$,) { + $dirname = $1; + $filename = $2; +} else { + $dirname = "."; + $filename = $inputfile; +} + +if ($filename =~ m,^(.*)(\.\S),) { + $prefix = $1; + $ext = $2; +} else { + $prefix = $filename; + $ext = ""; +} + +my $mcount_s = $dirname . "/.tmp_mc_" . $prefix . ".s"; +my $mcount_o = $dirname . "/.tmp_mc_" . $prefix . ".o"; + +# +# Step 1: find all the local symbols (static functions). +# +open (IN, "$nm $inputfile|") || die "error running $nm"; +while (<IN>) { + if (/^[0-9a-fA-F]+\s+t\s+(\S+)/) { + $locals{$1} = 1; + } +} +close(IN); + +# +# Step 2: find the sections and mcount call sites +# +open(IN, "$objdump -dr $inputfile|") || die "error running $objdump"; + +while (<IN>) { + # is it a section? + if (/$section_regex/) { + $read_function = 1; + $text_found = 0; + # section found, now is this a start of a function? + } elsif ($read_function && /$function_regex/) { + $read_function = 0; + $text_found = 1; + $text = $1; + # is this function static? If so, note this fact. + if (defined $locals{$text}) { + $convert{$text} = 1; + } + # is this a call site to mcount? If so, print the offset from the section + } elsif ($text_found && /$mcount_regex/) { + if (!$opened) { + open(FILE, ">$mcount_s") || die "can't create $mcount_s\n"; + $opened = 1; + print FILE "\t.section $mcount_section,\"a\",\@progbits\n"; + } + print FILE "\t$type $text + 0x$1\n"; + } +} + +# If we did not find any mcount callers, we are done (do nothing). +if (!$opened) { + exit(0); +} + +close(FILE); + +# +# Step 3: Compile the file that holds the list of call sites to mcount. +# +`$cc -o $mcount_o -c $mcount_s`; + +my @converts = keys %convert; + +# +# Step 4: Do we have sections that started with local functions? +# +if ($#converts >= 0) { + my $globallist = ""; + my $locallist = ""; + + 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); |