# 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 ".sched.text", "ax"
-# .globl my_func
-# my_func:
# [...]
-# call mcount (offset: 0x5)
+# func1:
+# [...]
+# 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 .sched.text. 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 ".sched.text", "ax"
-# my_func:
+# 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 < 7) {
+if ($#ARGV != 10) {
print "usage: $P arch bits objdump objcopy cc ld nm rm mv is_module inputfile\n";
print "version: $V\n";
exit(1);
$ld, $nm, $rm, $mv, $is_module, $inputfile) = @ARGV;
# This file refers to mcount and shouldn't be ftraced, so lets' ignore it
-if ($inputfile eq "kernel/trace/ftrace.o") {
+if ($inputfile =~ m,kernel/trace/ftrace\.o$,) {
exit(0);
}
".sched.text" => 1,
".spinlock.text" => 1,
".irqentry.text" => 1,
+ ".text.unlikely" => 1,
);
$objdump = "objdump" if ((length $objdump) == 0);
my %convert; # List of local functions used that needs conversion
my $type;
-my $nm_regex; # Find the local functions (return function)
+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 $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 ($arch eq "x86") {
if ($bits == 64) {
# We base the defaults off of i386, the other archs may
# feel free to change them in the below if statements.
#
-$nm_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\S+)";
+$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\$";
$cc .= " -m32";
} elsif ($arch eq "powerpc") {
- $nm_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\.?\\S+)";
+ $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\$";
$ld .= " -m elf64_sparc";
$cc .= " -m64";
$objcopy .= " -O elf64-sparc";
+} elsif ($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 $mcount_s = $dirname . "/.tmp_mc_" . $prefix . ".s";
my $mcount_o = $dirname . "/.tmp_mc_" . $prefix . ".o";
-#
-# --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.
-my $use_locals = 01;
-my $local_warn_once = 0;
-my $found_version = 0;
-
-open (IN, "$objcopy --version |") || die "error running $objcopy";
-while (<IN>) {
- if (/objcopy.*\s(\d+)\.(\d+)/) {
- my $major = $1;
- my $minor = $2;
-
- $found_version = 1;
- if ($major < 2 ||
- ($major == 2 && $minor < 17)) {
- $use_locals = 0;
- }
- last;
- }
-}
-close (IN);
-
-if (!$found_version) {
- print STDERR "WARNING: could not find objcopy version.\n" .
- "\tDisabling local function references.\n";
-}
+check_objcopy();
#
# Step 1: find all the local (static functions) and weak symbols.
-# 't' is local, 'w/W' is weak (we never use a weak function)
+# 't' is local, 'w/W' is weak
#
open (IN, "$nm $inputfile|") || die "error running $nm";
while (<IN>) {
- if (/$nm_regex/) {
+ if (/$local_regex/) {
$locals{$1} = 1;
- } elsif (/^[0-9a-fA-F]+\s+([wW])\s+(\S+)/) {
+ } elsif (/$weak_regex/) {
$weak{$2} = $1;
}
}
#
sub update_funcs
{
- return if ($#offsets < 0);
+ return unless ($ref_func and @offsets);
- defined($ref_func) || die "No function to reference";
-
- # A section only had a weak function, to represent it.
- # Unfortunately, a weak function may be overwritten by another
- # function of the same name, making all these offsets incorrect.
- # To be safe, we simply print a warning and bail.
+ # 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}) {
- print STDERR
- "$inputfile: WARNING: referencing weak function" .
+ die "$inputfile: ERROR: referencing weak function" .
" $ref_func for mcount\n";
- return;
}
# is this function static? If so, note this fact.
if (defined $locals{$ref_func}) {
# only use locals if objcopy supports globalize-symbols
- if (!$use_locals) {
+ if (!$can_use_local) {
return;
}
$convert{$ref_func} = 1;
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;
$read_function = 0;
}
# print out any recorded offsets
- update_funcs() if ($text_found);
+ update_funcs();
# reset all markers and arrays
$text_found = 0;
# section found, now is this a start of a function?
} elsif ($read_function && /$function_regex/) {
$text_found = 1;
- $offset = hex $1;
$text = $2;
# if this is either a local function or a weak function
if (!defined($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})) {
+ 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 $1;
}
}
- } elsif ($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 $inputfile and try again. If the same object file\n" .
- "\tstill causes an issue, then disable CONFIG_DYNAMIC_FTRACE.\n";
- exit(-1);
}
-
# is this a call site to mcount? If so, record it to print later
if ($text_found && /$mcount_regex/) {
$offsets[$#offsets + 1] = hex $1;
}
# dump out anymore offsets that may have been found
-update_funcs() if ($text_found);
+update_funcs();
# If we did not find any mcount callers, we are done (do nothing).
if (!$opened) {
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff