Re: [RFC PATCH 0/3] Mark literal strings in __init / __exit code

From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
To: Joe Perches <joe@perches.com>
Cc: Mathias Krause <minipli@googlemail.com>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [RFC PATCH 0/3] Mark literal strings in __init / __exit code
Date: Tue, 24 Jun 2014 16:31:08 +0200	[thread overview]
Message-ID: <87egyeqt03.fsf@rasmusvillemoes.dk> (raw)
In-Reply-To: <1403505219.18747.37.camel@joe-AO725> (Joe Perches's message of "Sun, 22 Jun 2014 23:33:39 -0700")

Joe Perches <joe@perches.com> writes:

> On Mon, 2014-06-23 at 08:23 +0200, Mathias Krause wrote:
>> On 23 June 2014 00:56, Joe Perches <joe@perches.com> wrote:
>> > On Mon, 2014-06-23 at 00:46 +0200, Mathias Krause wrote:
>> >> [...] patch 2 adds some syntactical sugar for the most popular use
>> >> case, by providing pr_<level> alike macros, namely pi_<level> for __init
>> >> code and pe_<level> for __exit code. This hides the use of the marker
>> >> macros behind the commonly known printing functions -- with just a
>> >> single character changed.
>> >>
>> >> Patch 3 exemplarily changes all strings and format strings in
>> >> arch/x86/kernel/acpi/boot.c to use the new macros. It also addresses a
>> >> few styling issues, though. But this already leads to ~1.7 kB of r/o
>> >> data moved to the .init.rodata section, marking it for release after
>> >> init.
>> >>
>> >> [...]
>> >
>> > I once proposed a similar thing.
>> >
>> > https://lkml.org/lkml/2009/7/21/421
>> >
>> > Matt Mackall replied
>> >
>> > https://lkml.org/lkml/2009/7/21/463
>> >
>> 
>> Thanks for the pointers. Have you looked at patch 2 and 3? I don't
>> think it makes the printk() case ugly. In fact, using pi_<level>()
>> should be no less readable then pr_<level>, no?
>
> I don't think it's particularly less readable, but I
> do think using the plug-in mechanism might be a better
> option as it would need no manual markings at all.

gcc already seems to contain infrastructure for this kind of thing, so
maybe it doesn't even require a plugin, but simply a little coordination
with the gcc folks. This snippet from gcc internals seems relevant:

-- Target Hook: section * TARGET_ASM_FUNCTION_RODATA_SECTION (tree
          DECL)
     Return the readonly data section associated with 'DECL_SECTION_NAME
     (DECL)'.  The default version of this function selects
     '.gnu.linkonce.r.name' if the function's section is
     '.gnu.linkonce.t.name', '.rodata.name' if function is in
     '.text.name', and the normal readonly-data section otherwise.

Rasmus