diff options
Diffstat (limited to 'scripts/recordmcount.pl')
| -rwxr-xr-x | scripts/recordmcount.pl | 219 |
1 files changed, 120 insertions, 99 deletions
diff --git a/scripts/recordmcount.pl b/scripts/recordmcount.pl index 090d300d7394..f0d14452632b 100755 --- a/scripts/recordmcount.pl +++ b/scripts/recordmcount.pl @@ -6,77 +6,93 @@ # 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 -# 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. @@ -86,10 +102,8 @@ # 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; @@ -99,7 +113,7 @@ $P =~ s@.*/@@g; 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: $V\n"; exit(1); @@ -109,7 +123,7 @@ my ($arch, $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 eq "kernel/trace/ftrace.o") { +if ($inputfile =~ m,kernel/trace/ftrace\.o$,) { exit(0); } @@ -119,6 +133,7 @@ my %text_sections = ( ".sched.text" => 1, ".spinlock.text" => 1, ".irqentry.text" => 1, + ".text.unlikely" => 1, ); $objdump = "objdump" if ((length $objdump) == 0); @@ -137,13 +152,47 @@ my %weak; # List of weak functions 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) { @@ -157,7 +206,8 @@ if ($arch eq "x86") { # We base the defaults off of i386, the other archs may # feel free to change them in the below if statements. # -$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+<(.*?)>:"; $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount\$"; @@ -206,7 +256,7 @@ if ($arch eq "x86_64") { $cc .= " -m32"; } elsif ($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+<(\\.?.*?)>:"; $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s\\.?_mcount\$"; @@ -278,44 +328,17 @@ if ($filename =~ m,^(.*)(\.\S),) { 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; } } @@ -333,26 +356,20 @@ my $offset = 0; # offset of ref_func to section beginning # sub update_funcs { - return if ($#offsets < 0); - - defined($ref_func) || die "No function to reference"; + return unless ($ref_func and @offsets); - # 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; @@ -378,9 +395,27 @@ 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_headers = 0; @@ -392,7 +427,7 @@ while (<IN>) { $read_function = 0; } # print out any recorded offsets - update_funcs() if (defined($ref_func)); + update_funcs(); # reset all markers and arrays $text_found = 0; @@ -421,21 +456,7 @@ while (<IN>) { $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 $1; @@ -443,7 +464,7 @@ while (<IN>) { } # dump out anymore offsets that may have been found -update_funcs() if (defined($ref_func)); +update_funcs(); # If we did not find any mcount callers, we are done (do nothing). if (!$opened) { |