Re: [PATCH 3/5]explictly ignore a file in recordmcount.pl

[Shaohua Li <shaohua.li@intel.com>]

On Tue, Dec 23, 2008 at 10:22:04PM +0800, Steven Rostedt wrote:
> 
> On Tue, 2008-12-23 at 14:08 +0800, Shaohua Li wrote:
> > In IA64, a function pointer isn't a 'unsigned long' but a
> > 'struct {unsigned long ip, unsigned long gp}'. MCOUNT_ADDR is determined
> > at link time not compile time, so explictly ignore kernel/trace/ftrace.o
> > in recordmcount.pl.
> > 
> > Signed-off-by: Shaohua Li <shaohua.li@intel.com>
> > ---
> >  kernel/trace/ftrace.c   |   10 +---------
> >  scripts/recordmcount.pl |    5 +++++
> >  2 files changed, 6 insertions(+), 9 deletions(-)
> > 
> > Index: linux/kernel/trace/ftrace.c
> > =================================> > --- linux.orig/kernel/trace/ftrace.c	2008-12-23 13:11:28.000000000 +0800
> > +++ linux/kernel/trace/ftrace.c	2008-12-23 13:24:59.000000000 +0800
> > @@ -263,14 +263,6 @@ static void ftrace_update_pid_func(void)
> >  # error Dynamic ftrace depends on MCOUNT_RECORD
> >  #endif
> >  
> > -/*
> > - * Since MCOUNT_ADDR may point to mcount itself, we do not want
> > - * to get it confused by reading a reference in the code as we
> > - * are parsing on objcopy output of text. Use a variable for
> > - * it instead.
> > - */
> > -static unsigned long mcount_addr = MCOUNT_ADDR;
> > -
> >  enum {
> >  	FTRACE_ENABLE_CALLS		= (1 << 0),
> >  	FTRACE_DISABLE_CALLS		= (1 << 1),
> > @@ -575,7 +567,7 @@ ftrace_code_disable(struct module *mod, 
> >  
> >  	ip = rec->ip;
> >  
> > -	ret = ftrace_make_nop(mod, rec, mcount_addr);
> > +	ret = ftrace_make_nop(mod, rec, MCOUNT_ADDR);
> 
> This change will make dynamic ftrace fail on other archs (ppc and x86).
> Please read the comment you deleted. By using MCOUNT_ADDR directly in
> the code, you will create a reference to mcount in a text section that
> will confuse recordmcount.pl. It will think this reference is a call to
> mcount and when it tries to modify it, it will fail because the code is
> not a call.
Did you read the changes just at the bottom? I explictly ignored
kernel/trace/ftrace.o in recordmcount.pl.

Thanks,
Shaohua

> 
> >  	if (ret) {
> >  		ftrace_bug(ret, ip);
> >  		rec->flags |= FTRACE_FL_FAILED;
> > Index: linux/scripts/recordmcount.pl
> > =================================> > --- linux.orig/scripts/recordmcount.pl	2008-12-23 13:24:38.000000000 +0800
> > +++ linux/scripts/recordmcount.pl	2008-12-23 13:24:59.000000000 +0800
> > @@ -109,6 +109,11 @@ if ($#ARGV < 7) {
> >  my ($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") {
> > +    exit(0);
> > +}
> > +
> >  # Acceptable sections to record.
> >  my %text_sections = (
> >       ".text" => 1,
> > 
> > 
>