linux-kernel - Re: [RFC v2 3/7] firmware: port built-in section to linker table

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Message-ID: <CAB=NE6XNt8Dwu5Kp=yt0cankemE_5Es1SdwmFo+q5-N466F3Ww@mail.gmail.com>
Date:	Tue, 3 May 2016 10:08:53 -0700
From:	"Luis R. Rodriguez" <mcgrof@...e.com>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	Kees Cook <keescook@...omium.org>,
	David Woodhouse <dwmw2@...radead.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	"x86@...nel.org" <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andy Lutomirski <luto@...capital.net>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	David Vrabel <david.vrabel@...rix.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Michael Brown <mcb30@...e.org>,
	Juergen Gross <jgross@...e.com>,
	Ming Lei <ming.lei@...onical.com>,
	Arnd Bergmann <arnd@...db.de>,
	linux-arch <linux-arch@...r.kernel.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	"benh@...nel.crashing.org" <benh@...nel.crashing.org>,
	jbaron@...mai.com, "ananth@...ibm.com" <ananth@...ibm.com>,
	anil.s.keshavamurthy@...el.com,
	"David S. Miller" <davem@...emloft.net>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>
Subject: Re: [RFC v2 3/7] firmware: port built-in section to linker table

On Mon, May 2, 2016 at 11:41 AM, Greg KH <gregkh@...uxfoundation.org> wrote:
> On Mon, May 02, 2016 at 11:34:33AM -0700, Kees Cook wrote:
>> On Mon, Feb 29, 2016 at 10:56 AM, Luis R. Rodriguez <mcgrof@...e.com> wrote:
>> > On Mon, Feb 29, 2016 at 10:12:50AM +0000, David Woodhouse wrote:
>> >> On Fri, 2016-02-19 at 05:45 -0800, Luis R. Rodriguez wrote:
>> >> > This ports built-in firmware to use linker tables,
>> >> > this replaces the custom section solution with a
>> >> > generic solution.
>> >> >
>> >> > This also demos the use of the .rodata (SECTION_RO)
>> >> > linker tables.
>> >> >
>> >> > Tested with 0 built-in firmware, 1 and 2 built-in
>> >> > firmwares successfully.
>> >>
>> >> I think we'd do better to rip this support out entirely. It just isn't
>> >> needed; firmware can live in an initramfs and don't even need *any*
>> >> actual running userspace support to load it from there these days, do
>> >> we?
>> >
>> > I think this is reasonable if and only if we really don't know of anyone
>> > out there not able to use initramfs. I'm happy to rip it out.
>>
>> The changelog for this doesn't say anything about _why_ the change is
>> being made? (and what about other architectures.) Also, Chrome OS
>> doesn't use an initramfs (and plenty of other things don't too). Being
>> able to build monolithic kernels (e.g. Android and Brillo) with
>> builtin firmware is very handy. Please don't remove built-in firmware
>> support.
>
> I second this, we can't break existing systems at all.  I thought we
> were going to keep built-in firmware, right Luis?

Removing built-in firmware was simply a suggestion by David which we
were evaluating here -- patches were not even yet produced, although I
have them now if we wanted to rip it out. Since Kees noted it has
users, we'll keep it.

 Luis