# 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.
+# 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.
#
-# 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.
+# 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.
#
-# 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:
+# .section ".sched.text", "ax"
+# [...]
+# func1:
# [...]
-# call mcount (offset: 0x5)
+# call mcount (offset: 0x10)
# [...]
# ret
-# other_func:
+# .globl fun2
+# func2: (offset: 0x20)
# [...]
-# call mcount (offset: 0x1b)
+# [...]
+# ret
+# func3:
+# [...]
+# call mcount (offset: 0x30)
# [...]
#
# 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:
+# 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 my_func + 0x5
-# .quad my_func + 0x1b
+# .quad func2 - 0x10
+# .quad func2 + 0x10
#
-# We can then compile this tmp.s into tmp.o, and link it to the original
+# We can then compile this tmp.s into tmp.o, and link it back to the original
# object.
#
-# But this gets hard if my_func is not globl (a static function).
-# In such a case we have:
+# 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 ".text.sched"
-# my_func:
+# .section ".sched.text", "ax"
+# func1:
# [...]
-# call mcount (offset: 0x5)
+# call mcount (offset: 0x10)
# [...]
# ret
-# .globl my_func
-# other_func:
+# func2:
# [...]
-# call mcount (offset: 0x1b)
+# 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 my_func:
+# 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 my_func.
+# 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 the my_func
+# 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 my_func that is global.
-# We can convert my_func back into a local symbol and we are done.
+# 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 symbols by using 'nm'
+# 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.
# 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 $V = '0.1';
-if ($#ARGV < 6) {
- print "usage: $P arch objdump objcopy cc ld nm rm mv inputfile\n";
+if ($#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, $objdump, $objcopy, $cc, $ld, $nm, $rm, $mv, $inputfile) = @ARGV;
-
-if ($arch eq "i386") {
- $ld = "ld -m elf_i386";
- $objdump = "objdump -M i386";
- $objcopy = "objcopy -O elf32-i386";
- $cc = "gcc -m32";
-}
+my ($arch, $endian, $bits, $objdump, $objcopy, $cc,
+ $ld, $nm, $rm, $mv, $is_module, $inputfile) = @ARGV;
-if ($arch eq "x86_64") {
- $ld = "ld -m elf_x86_64";
- $objdump = "objdump -M x86-64";
- $objcopy = "objcopy -O elf64-x86-64";
- $cc = "gcc -m64";
+# This file refers to mcount and shouldn't be ftraced, so lets' ignore it
+if ($inputfile =~ m,kernel/trace/ftrace\.o$,) {
+ exit(0);
}
-$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 $mv) == 0);
+# Acceptable sections to record.
+my %text_sections = (
+ ".text" => 1,
+ ".sched.text" => 1,
+ ".spinlock.text" => 1,
+ ".irqentry.text" => 1,
+ ".text.unlikely" => 1,
+);
+
+# Note: we are nice to C-programmers here, thus we skip the '||='-idiom.
+$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;
-my %convert;
+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 func name)
+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 $alignment; # The .align value to use for $mcount_section
+my $section_type; # Section header plus possible alignment command
+my $can_use_local = 0; # If we can use local function references
+
+# Shut up recordmcount if user has older objcopy
+my $quiet_recordmcount = ".tmp_quiet_recordmcount";
+my $print_warning = 1;
+$print_warning = 0 if ( -f $quiet_recordmcount);
+
+##
+# check_objcopy - whether objcopy supports --globalize-symbols
+#
+# --globalize-symbols came out in 2.17, we must test the version
+# of objcopy, and if it is less than 2.17, then we can not
+# record local functions.
+sub check_objcopy
+{
+ open (IN, "$objcopy --version |") or die "error running $objcopy";
+ while (<IN>) {
+ if (/objcopy.*\s(\d+)\.(\d+)/) {
+ $can_use_local = 1 if ($1 > 2 || ($1 == 2 && $2 >= 17));
+ last;
+ }
+ }
+ close (IN);
+
+ if (!$can_use_local && $print_warning) {
+ print STDERR "WARNING: could not find objcopy version or version " .
+ "is less than 2.17.\n" .
+ "\tLocal function references are disabled.\n";
+ open (QUIET, ">$quiet_recordmcount");
+ printf QUIET "Disables the warning from recordmcount.pl\n";
+ close QUIET;
+ }
+}
+
+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]+):.*\\smcount\$";
+$section_type = '@progbits';
+$type = ".long";
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";
+ $alignment = 8;
+
+ # 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") {
- $section_regex = "Disassembly of section";
- $function_regex = "<(.*?)>:";
- $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount\$";
- $type = ".long";
+ $alignment = 4;
+
+ # force flags for this arch
+ $ld .= " -m elf_i386";
+ $objdump .= " -M i386";
+ $objcopy .= " -O elf32-i386";
+ $cc .= " -m32";
+
+} elsif ($arch eq "s390" && $bits == 32) {
+ $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_390_32\\s+_mcount\$";
+ $alignment = 4;
+ $ld .= " -m elf_s390";
+ $cc .= " -m31";
+
+} elsif ($arch eq "s390" && $bits == 64) {
+ $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_390_(PC|PLT)32DBL\\s+_mcount\\+0x2\$";
+ $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";
+ $objcopy .= " -O elf32-sh-linux";
+ $cc .= " -m32";
+
+} elsif ($arch eq "powerpc") {
+ $local_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\.?\\S+)";
+ $function_regex = "^([0-9a-fA-F]+)\\s+<(\\.?.*?)>:";
+ $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s\\.?_mcount\$";
+
+ if ($bits == 64) {
+ $type = ".quad";
+ }
+
+} elsif ($arch eq "arm") {
+ $alignment = 2;
+ $section_type = '%progbits';
+
+} elsif ($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 swith 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]+):.*\\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\$";
} 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 $mcount_s = $dirname . "/.tmp_mc_" . $prefix . ".s";
my $mcount_o = $dirname . "/.tmp_mc_" . $prefix . ".o";
+check_objcopy();
+
#
-# Step 1: find all the local symbols (static functions).
+# Step 1: find all the local (static functions) and weak symbols.
+# 't' is local, 'w/W' is weak
#
open (IN, "$nm $inputfile|") || die "error running $nm";
while (<IN>) {
- if (/^[0-9a-fA-F]+\s+t\s+(\S+)/) {
+ if (/$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}) {
+
+ # only use locals if objcopy supports globalize-symbols
+ if (!$can_use_local) {
+ return;
+ }
+ $convert{$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 - $offset;
+ }
+}
+
#
# Step 2: find the sections and mcount call sites
#
-open(IN, "$objdump -dr $inputfile|") || die "error running $objdump";
+open(IN, "$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_function = 1;
+ $read_headers = 0;
+
+ # Only record text sections that we know are safe
+ $read_function = defined($text_sections{$1});
+ # 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/) {
- $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";
+ $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 $1;
+ }
}
- print FILE "\t$type $text + 0x$1\n";
+ }
+ # is this a call site to mcount? If so, record it to print later
+ if ($text_found && /$mcount_regex/) {
+ push(@offsets, hex $1);
}
}
+# dump out anymore offsets that may have been found
+update_funcs();
+
# If we did not find any mcount callers, we are done (do nothing).
if (!$opened) {
exit(0);