linux-kernel - Re: [PATCH] scripts/recordmcount.pl: Support build with -ffunction-sections.

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Date:	Tue, 30 Oct 2012 11:05:17 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Will Newton <will.newton@...il.com>
Cc:	Linux Kernel list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] scripts/recordmcount.pl: Support build with
 -ffunction-sections.

On Tue, 2012-10-30 at 14:51 +0000, Will Newton wrote:
> Scan any text section whose name begins with ".text." so
> we will find all the functions in a kernel built with
> -ffunction-sections.

A couple of things.

First, I'm very paranoid about a blanket "ok" on sections. We must
guarantee that all sections that starts with ".text" never is freed. And
if it is freed, that it must inform ftrace that it's about to free it
before it does. If we can not guarantee this, then we can't do it.

Second, most archs today do not use recordmcount.pl. They use the new
recordmcount.c file.

-- Steve

> 
> Signed-off-by: Will Newton <will.newton@...tec.com>
> ---
>  scripts/recordmcount.pl |    8 ++++++--
>  1 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/scripts/recordmcount.pl b/scripts/recordmcount.pl
> index b33446c..89461c4 100755
> --- a/scripts/recordmcount.pl
> +++ b/scripts/recordmcount.pl
> @@ -135,9 +135,13 @@ my %text_sections = (
>       ".spinlock.text" => 1,
>       ".irqentry.text" => 1,
>       ".kprobes.text" => 1,
> -     ".text.unlikely" => 1,
>  );
> 
> +sub is_valid_section
> +{
> +    return defined($text_sections{$1}) || $1 =~ m/^\.text\./;
> +}
> +
>  # Note: we are nice to C-programmers here, thus we skip the '||='-idiom.
>  $objdump = 'objdump' if (!$objdump);
>  $objcopy = 'objcopy' if (!$objcopy);
> @@ -502,7 +506,7 @@ while (<IN>) {
>  	$read_headers = 0;
> 
>  	# Only record text sections that we know are safe
> -	$read_function = defined($text_sections{$1});
> +	$read_function = is_valid_section($1);
>  	# print out any recorded offsets
>  	update_funcs();
> 


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