diff options
Diffstat (limited to 'scripts/recordmcount.pl')
| -rwxr-xr-x | scripts/recordmcount.pl | 603 |
1 files changed, 603 insertions, 0 deletions
diff --git a/scripts/recordmcount.pl b/scripts/recordmcount.pl new file mode 100755 index 000000000..6a4645a57 --- /dev/null +++ b/scripts/recordmcount.pl @@ -0,0 +1,603 @@ +#!/usr/bin/env perl +# SPDX-License-Identifier: GPL-2.0-only +# (c) 2008, Steven Rostedt <srostedt@redhat.com> +# +# 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 this is that each object file will have a +# section called __mcount_loc that will hold the list of pointers to mcount +# callers. After final linking, the vmlinux will have within .init.data the +# list of all callers to mcount between __start_mcount_loc and __stop_mcount_loc. +# 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. +# +# When parse this object file using 'objdump', the references to the call +# sites are offsets from the section 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. +# +# But where this section will reside finally in vmlinx is undetermined at +# this point. So we can't use this kind of offsets to record the final +# address of this call site. +# +# The trick is to change the call offset referring the start of a section to +# referring a function symbol in this section. During the link step, 'ld' will +# compute the final address according to the information we record. +# +# e.g. +# +# .section ".sched.text", "ax" +# [...] +# func1: +# [...] +# call mcount (offset: 0x10) +# [...] +# ret +# .globl fun2 +# func2: (offset: 0x20) +# [...] +# [...] +# ret +# func3: +# [...] +# call mcount (offset: 0x30) +# [...] +# +# Both relocation offsets for the mcounts in the above example will be +# offset from .sched.text. If we choose global symbol func2 as a reference and +# make another file called tmp.s with the new offsets: +# +# .section __mcount_loc +# .quad func2 - 0x10 +# .quad func2 + 0x10 +# +# We can then compile this tmp.s into tmp.o, and link it back to the original +# object. +# +# In our algorithm, we will choose the first global function we meet in this +# section as the reference. But this gets hard if there is no global functions +# in this section. In such a case we have to select a local one. E.g. func1: +# +# .section ".sched.text", "ax" +# func1: +# [...] +# call mcount (offset: 0x10) +# [...] +# ret +# func2: +# [...] +# call mcount (offset: 0x20) +# [...] +# .section "other.section" +# +# 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 func1: +# one local, one global. After final compile, we will end up with +# an undefined reference to func1 or a wrong reference to another global +# func1 in other files. +# +# 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 func1 +# into a global symbol before linking tmp.o. Then after we link tmp.o +# we will only have a single symbol for func1 that is global. +# We can convert func1 back into a local symbol and we are done. +# +# Here are the steps we take: +# +# 1) Record all the local and weak 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. +# 8) Link the object with the list object. +# 9) Move the result back to the original object. +# + +use warnings; +use strict; + +my $P = $0; +$P =~ s@.*/@@g; + +my $V = '0.1'; + +if ($#ARGV != 11) { + print "usage: $P arch endian bits objdump objcopy cc ld nm rm mv is_module inputfile\n"; + print "version: $V\n"; + exit(1); +} + +my ($arch, $endian, $bits, $objdump, $objcopy, $cc, + $ld, $nm, $rm, $mv, $is_module, $inputfile) = @ARGV; + +# This file refers to mcount and shouldn't be ftraced, so lets' ignore it +if ($inputfile =~ m,kernel/trace/ftrace\.o$,) { + exit(0); +} + +# Acceptable sections to record. +my %text_sections = ( + ".text" => 1, + ".init.text" => 1, + ".ref.text" => 1, + ".sched.text" => 1, + ".spinlock.text" => 1, + ".irqentry.text" => 1, + ".softirqentry.text" => 1, + ".kprobes.text" => 1, + ".cpuidle.text" => 1, + ".text.unlikely" => 1, +); + +# Acceptable section-prefixes to record. +my %text_section_prefixes = ( + ".text." => 1, +); + +# Note: we are nice to C-programmers here, thus we skip the '||='-idiom. +$objdump = 'objdump' if (!$objdump); +$objcopy = 'objcopy' if (!$objcopy); +$cc = 'gcc' if (!$cc); +$ld = 'ld' if (!$ld); +$nm = 'nm' if (!$nm); +$rm = 'rm' if (!$rm); +$mv = 'mv' if (!$mv); + +#print STDERR "running: $P '$arch' '$objdump' '$objcopy' '$cc' '$ld' " . +# "'$nm' '$rm' '$mv' '$inputfile'\n"; + +my %locals; # List of local (static) functions +my %weak; # List of weak functions +my %convert; # List of local functions used that needs conversion + +my $type; +my $local_regex; # Match a local function (return function) +my $weak_regex; # Match a weak function (return function) +my $section_regex; # Find the start of a section +my $function_regex; # Find the name of a function + # (return offset and func name) +my $mcount_regex; # Find the call site to mcount (return offset) +my $mcount_adjust; # Address adjustment to mcount offset +my $alignment; # The .align value to use for $mcount_section +my $section_type; # Section header plus possible alignment command + +if ($arch =~ /(x86(_64)?)|(i386)/) { + if ($bits == 64) { + $arch = "x86_64"; + } else { + $arch = "i386"; + } +} + +# +# We base the defaults off of i386, the other archs may +# feel free to change them in the below if statements. +# +$local_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\S+)"; +$weak_regex = "^[0-9a-fA-F]+\\s+([wW])\\s+(\\S+)"; +$section_regex = "Disassembly of section\\s+(\\S+):"; +$function_regex = "^([0-9a-fA-F]+)\\s+<([^^]*?)>:"; +$mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s(mcount|__fentry__)\$"; +$section_type = '@progbits'; +$mcount_adjust = 0; +$type = ".long"; + +if ($arch eq "x86_64") { + $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s(mcount|__fentry__)([+-]0x[0-9a-zA-Z]+)?\$"; + $type = ".quad"; + $alignment = 8; + $mcount_adjust = -1; + + # force flags for this arch + $ld .= " -m elf_x86_64"; + $objdump .= " -M x86-64"; + $objcopy .= " -O elf64-x86-64"; + $cc .= " -m64"; + +} elsif ($arch eq "i386") { + $alignment = 4; + $mcount_adjust = -1; + + # force flags for this arch + $ld .= " -m elf_i386"; + $objdump .= " -M i386"; + $objcopy .= " -O elf32-i386"; + $cc .= " -m32"; + +} elsif ($arch eq "s390" && $bits == 64) { + if ($cc =~ /-DCC_USING_HOTPATCH/) { + $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*c0 04 00 00 00 00\\s*(brcl\\s*0,|jgnop\\s*)[0-9a-f]+ <([^\+]*)>\$"; + $mcount_adjust = 0; + } + $alignment = 8; + $type = ".quad"; + $ld .= " -m elf64_s390"; + $cc .= " -m64"; + +} elsif ($arch eq "sh") { + $alignment = 2; + + # force flags for this arch + $ld .= " -m shlelf_linux"; + if ($endian eq "big") { + $objcopy .= " -O elf32-shbig-linux"; + } else { + $objcopy .= " -O elf32-sh-linux"; + } + +} elsif ($arch eq "powerpc") { + my $ldemulation; + + $local_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\.?\\S+)"; + # See comment in the sparc64 section for why we use '\w'. + $function_regex = "^([0-9a-fA-F]+)\\s+<(\\.?\\w*?)>:"; + $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s\\.?_mcount\$"; + + if ($endian eq "big") { + $cc .= " -mbig-endian "; + $ld .= " -EB "; + $ldemulation = "ppc" + } else { + $cc .= " -mlittle-endian "; + $ld .= " -EL "; + $ldemulation = "lppc" + } + if ($bits == 64) { + $type = ".quad"; + $cc .= " -m64 "; + $ld .= " -m elf64".$ldemulation." "; + } else { + $cc .= " -m32 "; + $ld .= " -m elf32".$ldemulation." "; + } + +} elsif ($arch eq "arm") { + $alignment = 2; + $section_type = '%progbits'; + $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_ARM_(CALL|PC24|THM_CALL)" . + "\\s+(__gnu_mcount_nc|mcount)\$"; + +} elsif ($arch eq "arm64") { + $alignment = 3; + $section_type = '%progbits'; + $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_AARCH64_CALL26\\s+_mcount\$"; + $type = ".quad"; +} elsif ($arch eq "ia64") { + $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$"; + $type = "data8"; + + if ($is_module eq "0") { + $cc .= " -mconstant-gp"; + } +} elsif ($arch eq "sparc64") { + # In the objdump output there are giblets like: + # 0000000000000000 <igmp_net_exit-0x18>: + # As there's some data blobs that get emitted into the + # text section before the first instructions and the first + # real symbols. We don't want to match that, so to combat + # this we use '\w' so we'll match just plain symbol names, + # and not those that also include hex offsets inside of the + # '<>' brackets. Actually the generic function_regex setting + # could safely use this too. + $function_regex = "^([0-9a-fA-F]+)\\s+<(\\w*?)>:"; + + # Sparc64 calls '_mcount' instead of plain 'mcount'. + $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$"; + + $alignment = 8; + $type = ".xword"; + $ld .= " -m elf64_sparc"; + $cc .= " -m64"; + $objcopy .= " -O elf64-sparc"; +} elsif ($arch eq "mips") { + # To enable module support, we need to enable the -mlong-calls option + # of gcc for module, after using this option, we can not get the real + # offset of the calling to _mcount, but the offset of the lui + # instruction or the addiu one. herein, we record the address of the + # first one, and then we can replace this instruction by a branch + # instruction to jump over the profiling function to filter the + # indicated functions, or switch back to the lui instruction to trace + # them, which means dynamic tracing. + # + # c: 3c030000 lui v1,0x0 + # c: R_MIPS_HI16 _mcount + # c: R_MIPS_NONE *ABS* + # c: R_MIPS_NONE *ABS* + # 10: 64630000 daddiu v1,v1,0 + # 10: R_MIPS_LO16 _mcount + # 10: R_MIPS_NONE *ABS* + # 10: R_MIPS_NONE *ABS* + # 14: 03e0082d move at,ra + # 18: 0060f809 jalr v1 + # + # for the kernel: + # + # 10: 03e0082d move at,ra + # 14: 0c000000 jal 0 <loongson_halt> + # 14: R_MIPS_26 _mcount + # 14: R_MIPS_NONE *ABS* + # 14: R_MIPS_NONE *ABS* + # 18: 00020021 nop + if ($is_module eq "0") { + $mcount_regex = "^\\s*([0-9a-fA-F]+): R_MIPS_26\\s+_mcount\$"; + } else { + $mcount_regex = "^\\s*([0-9a-fA-F]+): R_MIPS_HI16\\s+_mcount\$"; + } + $objdump .= " -Melf-trad".$endian."mips "; + + if ($endian eq "big") { + $endian = " -EB "; + $ld .= " -melf".$bits."btsmip"; + } else { + $endian = " -EL "; + $ld .= " -melf".$bits."ltsmip"; + } + + $cc .= " -mno-abicalls -fno-pic -mabi=" . $bits . $endian; + $ld .= $endian; + + if ($bits == 64) { + $function_regex = + "^([0-9a-fA-F]+)\\s+<(.|[^\$]L.*?|\$[^L].*?|[^\$][^L].*?)>:"; + $type = ".dword"; + } +} elsif ($arch eq "microblaze") { + # Microblaze calls '_mcount' instead of plain 'mcount'. + $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$"; +} elsif ($arch eq "riscv") { + $function_regex = "^([0-9a-fA-F]+)\\s+<([^.0-9][0-9a-zA-Z_\\.]+)>:"; + $mcount_regex = "^\\s*([0-9a-fA-F]+):\\sR_RISCV_CALL(_PLT)?\\s_?mcount\$"; + $type = ".quad"; + $alignment = 2; +} elsif ($arch eq "csky") { + $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_CKCORE_PCREL_JSR_IMM26BY2\\s+_mcount\$"; + $alignment = 2; +} else { + die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD"; +} + +my $text_found = 0; +my $read_function = 0; +my $opened = 0; +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_" . $prefix . ".o"; + +# +# Step 1: find all the local (static functions) and weak symbols. +# 't' is local, 'w/W' is weak +# +open (IN, "$nm $inputfile|") || die "error running $nm"; +while (<IN>) { + if (/$local_regex/) { + $locals{$1} = 1; + } elsif (/$weak_regex/) { + $weak{$2} = $1; + } +} +close(IN); + +my @offsets; # Array of offsets of mcount callers +my $ref_func; # reference function to use for offsets +my $offset = 0; # offset of ref_func to section beginning + +## +# update_funcs - print out the current mcount callers +# +# Go through the list of offsets to callers and write them to +# the output file in a format that can be read by an assembler. +# +sub update_funcs +{ + return unless ($ref_func and @offsets); + + # Sanity check on weak function. A weak function may be overwritten by + # another function of the same name, making all these offsets incorrect. + if (defined $weak{$ref_func}) { + die "$inputfile: ERROR: referencing weak function" . + " $ref_func for mcount\n"; + } + + # is this function static? If so, note this fact. + if (defined $locals{$ref_func}) { + $convert{$ref_func} = 1; + } + + # Loop through all the mcount caller offsets and print a reference + # to the caller based from the ref_func. + if (!$opened) { + open(FILE, ">$mcount_s") || die "can't create $mcount_s\n"; + $opened = 1; + print FILE "\t.section $mcount_section,\"a\",$section_type\n"; + print FILE "\t.align $alignment\n" if (defined($alignment)); + } + foreach my $cur_offset (@offsets) { + printf FILE "\t%s %s + %d\n", $type, $ref_func, $cur_offset - $offset; + } +} + +# +# Step 2: find the sections and mcount call sites +# +open(IN, "LC_ALL=C $objdump -hdr $inputfile|") || die "error running $objdump"; + +my $text; + + +# read headers first +my $read_headers = 1; + +while (<IN>) { + + if ($read_headers && /$mcount_section/) { + # + # Somehow the make process can execute this script on an + # object twice. If it does, we would duplicate the mcount + # section and it will cause the function tracer self test + # to fail. Check if the mcount section exists, and if it does, + # warn and exit. + # + print STDERR "ERROR: $mcount_section already in $inputfile\n" . + "\tThis may be an indication that your build is corrupted.\n" . + "\tDelete $inputfile and try again. If the same object file\n" . + "\tstill causes an issue, then disable CONFIG_DYNAMIC_FTRACE.\n"; + exit(-1); + } + + # is it a section? + if (/$section_regex/) { + $read_headers = 0; + + # Only record text sections that we know are safe + $read_function = defined($text_sections{$1}); + if (!$read_function) { + foreach my $prefix (keys %text_section_prefixes) { + if (substr($1, 0, length $prefix) eq $prefix) { + $read_function = 1; + last; + } + } + } + # print out any recorded offsets + update_funcs(); + + # reset all markers and arrays + $text_found = 0; + undef($ref_func); + undef(@offsets); + + # section found, now is this a start of a function? + } elsif ($read_function && /$function_regex/) { + $text_found = 1; + $text = $2; + + # if this is either a local function or a weak function + # keep looking for functions that are global that + # we can use safely. + if (!defined($locals{$text}) && !defined($weak{$text})) { + $ref_func = $text; + $read_function = 0; + $offset = hex $1; + } else { + # if we already have a function, and this is weak, skip it + if (!defined($ref_func) && !defined($weak{$text}) && + # PPC64 can have symbols that start with .L and + # gcc considers these special. Don't use them! + $text !~ /^\.L/) { + $ref_func = $text; + $offset = hex $1; + } + } + } + # is this a call site to mcount? If so, record it to print later + if ($text_found && /$mcount_regex/) { + push(@offsets, (hex $1) + $mcount_adjust); + } +} + +# dump out anymore offsets that may have been found +update_funcs(); + +# If we did not find any mcount callers, we are done (do nothing). +if (!$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); + +# vim: softtabstop=4 |