538f19526e
With dynamic function tracer, by default, _mcount is defined as an
"empty" function, it returns directly without any more action . When
enabling it in user-space, it will jump to a real tracing
function(ftrace_caller), and do the real job for us.
Differ from the static function tracer, dynamic function tracer provides
two functions ftrace_make_call()/ftrace_make_nop() to enable/disable the
tracing of some indicated kernel functions(set_ftrace_filter).
In the -v4 version, the implementation of this support is basically the same as
X86 version does: _mcount is implemented as an empty function and ftrace_caller
is implemented as a real tracing function respectively.
But in this version, to support module tracing with the help of
-mlong-calls in arch/mips/Makefile:
MODFLAGS += -mlong-calls.
The stuff becomes a little more complex. We need to cope with two
different type of calling to _mcount.
For the kernel part, the calling to _mcount(result of "objdump -hdr
vmlinux"). is like this:
108: 03e0082d move at,ra
10c: 0c000000 jal 0 <fpcsr_pending>
10c: R_MIPS_26 _mcount
10c: R_MIPS_NONE *ABS*
10c: R_MIPS_NONE *ABS*
110: 00020021 nop
For the module with -mlong-calls, it looks like this:
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
In the kernel version, there is only one "_mcount" string for every
kernel function, so, we just need to match this one in mcount_regex of
scripts/recordmcount.pl, but in the module version, we need to choose
one of the two to match. Herein, I choose the first one with
"R_MIPS_HI16 _mcount".
and In the kernel verion, without module tracing support, we just need
to replace "jal _mcount" by "jal ftrace_caller" to do real tracing, and
filter the tracing of some kernel functions via replacing it by a nop
instruction.
but as we have described before, the instruction "jal ftrace_caller" only left
32bit length for the address of ftrace_caller, it will fail when calling from
the module space. so, herein, we must replace something else.
the basic idea is loading the address of ftrace_caller to v1 via changing these
two instructions:
lui v1,0x0
addiu v1,v1,0
If we want to enable the tracing, we need to replace the above instructions to:
lui v1, HI_16BIT_ftrace_caller
addiu v1, v1, LOW_16BIT_ftrace_caller
If we want to stop the tracing of the indicated kernel functions, we
just need to replace the "jalr v1" to a nop instruction. but we need to
replace two instructions and encode the above two instructions
oursevles.
Is there a simpler solution? Yes! Here it is, in this version, we put _mcount
and ftrace_caller together, which means the address of _mcount and
ftrace_caller is the same:
_mcount:
ftrace_caller:
j ftrace_stub
nop
...(do real tracing here)...
ftrace_stub:
jr ra
move ra, at
By default, the kernel functions call _mcount, and then jump to ftrace_stub and
return. and when we want to do real tracing, we just need to remove that "j
ftrace_stub", and it will run through the two "nop" instructions and then do
the real tracing job.
what about filtering job? we just need to do this:
lui v1, hi_16bit_of_mcount <--> b 1f (0x10000004)
addiu v1, v1, low_16bit_of_mcount
move at, ra
jalr v1
nop
1f: (rec->ip + 12)
In linux-mips64, there will be some local symbols, whose name are
prefixed by $L, which need to be filtered. thanks goes to Steven for
writing the mips64-specific function_regex.
In a conclusion, with RISC, things becomes easier with such a "stupid"
trick, RISC is something like K.I.S.S, and also, there are lots of
"simple" tricks in the whole ftrace support, thanks goes to Steven and
the other folks for providing such a wonderful tracing framework!
Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
Cc: Nicholas Mc Guire <der.herr@hofr.at>
Cc: zhangfx@lemote.com
Cc: Wu Zhangjin <wuzhangjin@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: http://patchwork.linux-mips.org/patch/675/
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
590 lines
17 KiB
Perl
Executable File
590 lines
17 KiB
Perl
Executable File
#!/usr/bin/perl -w
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# (c) 2008, Steven Rostedt <srostedt@redhat.com>
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# Licensed under the terms of the GNU GPL License version 2
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#
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# recordmcount.pl - makes a section called __mcount_loc that holds
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# all the offsets to the calls to mcount.
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#
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#
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# What we want to end up with this is that each object file will have a
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# section called __mcount_loc that will hold the list of pointers to mcount
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# callers. After final linking, the vmlinux will have within .init.data the
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# list of all callers to mcount between __start_mcount_loc and __stop_mcount_loc.
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# Later on boot up, the kernel will read this list, save the locations and turn
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# them into nops. When tracing or profiling is later enabled, these locations
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# will then be converted back to pointers to some function.
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#
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# This is no easy feat. This script is called just after the original
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# object is compiled and before it is linked.
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#
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# When parse this object file using 'objdump', the references to the call
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# sites are offsets from the section that the call site is in. Hence, all
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# functions in a section that has a call site to mcount, will have the
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# offset from the beginning of the section and not the beginning of the
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# function.
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#
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# But where this section will reside finally in vmlinx is undetermined at
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# this point. So we can't use this kind of offsets to record the final
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# address of this call site.
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#
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# The trick is to change the call offset referring the start of a section to
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# referring a function symbol in this section. During the link step, 'ld' will
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# compute the final address according to the information we record.
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#
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# e.g.
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#
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# .section ".sched.text", "ax"
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# [...]
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# func1:
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# [...]
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# call mcount (offset: 0x10)
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# [...]
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# ret
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# .globl fun2
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# func2: (offset: 0x20)
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# [...]
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# [...]
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# ret
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# func3:
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# [...]
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# call mcount (offset: 0x30)
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# [...]
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#
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# Both relocation offsets for the mcounts in the above example will be
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# offset from .sched.text. If we choose global symbol func2 as a reference and
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# make another file called tmp.s with the new offsets:
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#
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# .section __mcount_loc
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# .quad func2 - 0x10
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# .quad func2 + 0x10
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#
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# We can then compile this tmp.s into tmp.o, and link it back to the original
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# object.
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#
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# In our algorithm, we will choose the first global function we meet in this
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# section as the reference. But this gets hard if there is no global functions
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# in this section. In such a case we have to select a local one. E.g. func1:
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#
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# .section ".sched.text", "ax"
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# func1:
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# [...]
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# call mcount (offset: 0x10)
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# [...]
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# ret
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# func2:
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# [...]
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# call mcount (offset: 0x20)
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# [...]
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# .section "other.section"
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#
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# If we make the tmp.s the same as above, when we link together with
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# the original object, we will end up with two symbols for func1:
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# one local, one global. After final compile, we will end up with
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# an undefined reference to func1 or a wrong reference to another global
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# func1 in other files.
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#
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# Since local objects can reference local variables, we need to find
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# a way to make tmp.o reference the local objects of the original object
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# file after it is linked together. To do this, we convert func1
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# into a global symbol before linking tmp.o. Then after we link tmp.o
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# we will only have a single symbol for func1 that is global.
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# We can convert func1 back into a local symbol and we are done.
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#
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# Here are the steps we take:
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#
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# 1) Record all the local and weak symbols by using 'nm'
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# 2) Use objdump to find all the call site offsets and sections for
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# mcount.
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# 3) Compile the list into its own object.
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# 4) Do we have to deal with local functions? If not, go to step 8.
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# 5) Make an object that converts these local functions to global symbols
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# with objcopy.
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# 6) Link together this new object with the list object.
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# 7) Convert the local functions back to local symbols and rename
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# the result as the original object.
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# 8) Link the object with the list object.
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# 9) Move the result back to the original object.
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#
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use strict;
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my $P = $0;
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$P =~ s@.*/@@g;
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my $V = '0.1';
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if ($#ARGV != 11) {
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print "usage: $P arch endian bits objdump objcopy cc ld nm rm mv is_module inputfile\n";
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print "version: $V\n";
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exit(1);
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}
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my ($arch, $endian, $bits, $objdump, $objcopy, $cc,
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$ld, $nm, $rm, $mv, $is_module, $inputfile) = @ARGV;
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# This file refers to mcount and shouldn't be ftraced, so lets' ignore it
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if ($inputfile =~ m,kernel/trace/ftrace\.o$,) {
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exit(0);
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}
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# Acceptable sections to record.
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my %text_sections = (
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".text" => 1,
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".sched.text" => 1,
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".spinlock.text" => 1,
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".irqentry.text" => 1,
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".text.unlikely" => 1,
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);
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$objdump = "objdump" if ((length $objdump) == 0);
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$objcopy = "objcopy" if ((length $objcopy) == 0);
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$cc = "gcc" if ((length $cc) == 0);
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$ld = "ld" if ((length $ld) == 0);
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$nm = "nm" if ((length $nm) == 0);
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$rm = "rm" if ((length $rm) == 0);
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$mv = "mv" if ((length $mv) == 0);
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#print STDERR "running: $P '$arch' '$objdump' '$objcopy' '$cc' '$ld' " .
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# "'$nm' '$rm' '$mv' '$inputfile'\n";
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my %locals; # List of local (static) functions
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my %weak; # List of weak functions
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my %convert; # List of local functions used that needs conversion
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my $type;
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my $local_regex; # Match a local function (return function)
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my $weak_regex; # Match a weak function (return function)
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my $section_regex; # Find the start of a section
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my $function_regex; # Find the name of a function
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# (return offset and func name)
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my $mcount_regex; # Find the call site to mcount (return offset)
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my $alignment; # The .align value to use for $mcount_section
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my $section_type; # Section header plus possible alignment command
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my $can_use_local = 0; # If we can use local function references
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# Shut up recordmcount if user has older objcopy
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my $quiet_recordmcount = ".tmp_quiet_recordmcount";
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my $print_warning = 1;
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$print_warning = 0 if ( -f $quiet_recordmcount);
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##
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# check_objcopy - whether objcopy supports --globalize-symbols
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#
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# --globalize-symbols came out in 2.17, we must test the version
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# of objcopy, and if it is less than 2.17, then we can not
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# record local functions.
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sub check_objcopy
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{
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open (IN, "$objcopy --version |") or die "error running $objcopy";
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while (<IN>) {
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if (/objcopy.*\s(\d+)\.(\d+)/) {
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$can_use_local = 1 if ($1 > 2 || ($1 == 2 && $2 >= 17));
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last;
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}
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}
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close (IN);
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if (!$can_use_local && $print_warning) {
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print STDERR "WARNING: could not find objcopy version or version " .
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"is less than 2.17.\n" .
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"\tLocal function references are disabled.\n";
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open (QUIET, ">$quiet_recordmcount");
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printf QUIET "Disables the warning from recordmcount.pl\n";
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close QUIET;
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}
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}
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if ($arch eq "x86") {
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if ($bits == 64) {
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$arch = "x86_64";
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} else {
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$arch = "i386";
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}
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}
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#
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# We base the defaults off of i386, the other archs may
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# feel free to change them in the below if statements.
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#
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$local_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\S+)";
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$weak_regex = "^[0-9a-fA-F]+\\s+([wW])\\s+(\\S+)";
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$section_regex = "Disassembly of section\\s+(\\S+):";
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$function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
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$mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount\$";
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$section_type = '@progbits';
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$type = ".long";
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if ($arch eq "x86_64") {
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$mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount([+-]0x[0-9a-zA-Z]+)?\$";
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$type = ".quad";
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$alignment = 8;
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# force flags for this arch
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$ld .= " -m elf_x86_64";
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$objdump .= " -M x86-64";
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$objcopy .= " -O elf64-x86-64";
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$cc .= " -m64";
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} elsif ($arch eq "i386") {
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$alignment = 4;
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# force flags for this arch
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$ld .= " -m elf_i386";
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$objdump .= " -M i386";
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$objcopy .= " -O elf32-i386";
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$cc .= " -m32";
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} elsif ($arch eq "s390" && $bits == 32) {
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$mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_390_32\\s+_mcount\$";
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$alignment = 4;
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$ld .= " -m elf_s390";
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$cc .= " -m31";
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} elsif ($arch eq "s390" && $bits == 64) {
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$mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_390_(PC|PLT)32DBL\\s+_mcount\\+0x2\$";
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$alignment = 8;
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$type = ".quad";
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$ld .= " -m elf64_s390";
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$cc .= " -m64";
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} elsif ($arch eq "sh") {
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$alignment = 2;
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# force flags for this arch
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$ld .= " -m shlelf_linux";
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$objcopy .= " -O elf32-sh-linux";
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$cc .= " -m32";
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} elsif ($arch eq "powerpc") {
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$local_regex = "^[0-9a-fA-F]+\\s+t\\s+(\\.?\\S+)";
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$function_regex = "^([0-9a-fA-F]+)\\s+<(\\.?.*?)>:";
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$mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s\\.?_mcount\$";
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if ($bits == 64) {
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$type = ".quad";
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}
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} elsif ($arch eq "arm") {
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$alignment = 2;
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$section_type = '%progbits';
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} elsif ($arch eq "ia64") {
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$mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
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$type = "data8";
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if ($is_module eq "0") {
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$cc .= " -mconstant-gp";
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}
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} elsif ($arch eq "sparc64") {
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# In the objdump output there are giblets like:
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# 0000000000000000 <igmp_net_exit-0x18>:
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# As there's some data blobs that get emitted into the
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# text section before the first instructions and the first
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# real symbols. We don't want to match that, so to combat
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# this we use '\w' so we'll match just plain symbol names,
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# and not those that also include hex offsets inside of the
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# '<>' brackets. Actually the generic function_regex setting
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# could safely use this too.
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$function_regex = "^([0-9a-fA-F]+)\\s+<(\\w*?)>:";
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# Sparc64 calls '_mcount' instead of plain 'mcount'.
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$mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
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$alignment = 8;
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$type = ".xword";
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$ld .= " -m elf64_sparc";
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$cc .= " -m64";
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$objcopy .= " -O elf64-sparc";
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} elsif ($arch eq "mips") {
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# To enable module support, we need to enable the -mlong-calls option
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# of gcc for module, after using this option, we can not get the real
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# offset of the calling to _mcount, but the offset of the lui
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# instruction or the addiu one. herein, we record the address of the
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# first one, and then we can replace this instruction by a branch
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# instruction to jump over the profiling function to filter the
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# indicated functions, or swith back to the lui instruction to trace
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# them, which means dynamic tracing.
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#
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# c: 3c030000 lui v1,0x0
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# c: R_MIPS_HI16 _mcount
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# c: R_MIPS_NONE *ABS*
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# c: R_MIPS_NONE *ABS*
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# 10: 64630000 daddiu v1,v1,0
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# 10: R_MIPS_LO16 _mcount
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# 10: R_MIPS_NONE *ABS*
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# 10: R_MIPS_NONE *ABS*
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# 14: 03e0082d move at,ra
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# 18: 0060f809 jalr v1
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#
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# for the kernel:
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#
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# 10: 03e0082d move at,ra
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# 14: 0c000000 jal 0 <loongson_halt>
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# 14: R_MIPS_26 _mcount
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# 14: R_MIPS_NONE *ABS*
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# 14: R_MIPS_NONE *ABS*
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# 18: 00020021 nop
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if ($is_module eq "0") {
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$mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
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} else {
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$mcount_regex = "^\\s*([0-9a-fA-F]+): R_MIPS_HI16\\s+_mcount\$";
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}
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$objdump .= " -Melf-trad".$endian."mips ";
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if ($endian eq "big") {
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$endian = " -EB ";
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$ld .= " -melf".$bits."btsmip";
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} else {
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$endian = " -EL ";
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$ld .= " -melf".$bits."ltsmip";
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}
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$cc .= " -mno-abicalls -fno-pic -mabi=" . $bits . $endian;
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$ld .= $endian;
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if ($bits == 64) {
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$function_regex =
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"^([0-9a-fA-F]+)\\s+<(.|[^\$]L.*?|\$[^L].*?|[^\$][^L].*?)>:";
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$type = ".dword";
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}
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} elsif ($arch eq "microblaze") {
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# Microblaze calls '_mcount' instead of plain 'mcount'.
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$mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
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} else {
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die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD";
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}
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my $text_found = 0;
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my $read_function = 0;
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my $opened = 0;
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my $mcount_section = "__mcount_loc";
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my $dirname;
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my $filename;
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my $prefix;
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my $ext;
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if ($inputfile =~ m,^(.*)/([^/]*)$,) {
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$dirname = $1;
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$filename = $2;
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} else {
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$dirname = ".";
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$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_" . $prefix . ".o";
|
|
|
|
check_objcopy();
|
|
|
|
#
|
|
# Step 1: find all the local (static functions) and weak symbols.
|
|
# 't' is local, 'w/W' is weak
|
|
#
|
|
open (IN, "$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}) {
|
|
|
|
# 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.
|
|
for (my $i=0; $i <= $#offsets; $i++) {
|
|
if (!$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));
|
|
}
|
|
printf FILE "\t%s %s + %d\n", $type, $ref_func, $offsets[$i] - $offset;
|
|
}
|
|
}
|
|
|
|
#
|
|
# Step 2: find the sections and mcount call sites
|
|
#
|
|
open(IN, "$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/) {
|
|
$read_headers = 0;
|
|
|
|
# Only record text sections that we know are safe
|
|
if (defined($text_sections{$1})) {
|
|
$read_function = 1;
|
|
} else {
|
|
$read_function = 0;
|
|
}
|
|
# 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/) {
|
|
$offsets[$#offsets + 1] = 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);
|
|
}
|
|
|
|
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);
|