linux-kernel - Updating kernel.org cross compilers?

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Message-ID: <92b5ff36-ad2b-10bc-de4f-4774babd9625@arm.com>
Date:   Wed, 26 Apr 2017 15:14:16 +0100
From:   Andre Przywara <andre.przywara@....com>
To:     Tony Breeds <tony@...eyournoodle.com>
Cc:     Segher Boessenkool <segher@...nel.crashing.org>,
        Guenter Roeck <linux@...ck-us.net>,
        LKML <linux-kernel@...r.kernel.org>,
        LAKML <linux-arm-kernel@...ts.infradead.org>,
        Arnd Bergmann <arnd@...db.de>
Subject: Updating kernel.org cross compilers?

Hi!

(Tony: I've seen you redirecting to "Chris" in an older email, but the
web archive doesn't have his email address)

It seems that many people (even outside the Linux kernel community) use
the cross compilers provided at kernel.org/pub/tools/crosstool.
The latest compiler I find there is 4.9.0, which celebrated its third
birthday at the weekend, also has been superseded by 4.9.4 meanwhile.

So I took Segher's buildall scripts from [1] and threw binutils 2.28 and
GCC 6.3.0 at them. After removing --enable-sjlj-exceptions from
build-gcc and adding --disable-multilib (for building x86-64 on a x86-64
box without 32-bit libs) I was able to build (bare-metal) toolchains for
all architectures except arc, m68k, tilegx and tilepro.
Now my understanding is that a baremetal/stage 1 compiler should be
build with "all-gcc" instead of the implicit "all" make target, and
"install-gcc" instead of "install". And indeed adding this to build-gcc
makes all toolchains build now - except arc, which needs an explicit
"--with-cpu=arc700" on the GCC configure command line.

So after those changes, the sequence:
$ ./buildall --toolchain
$ PATH=$PATH:/opt/cross/bin
$ ./buildall --kernel
worked reasonably well for me (binutils 2.28, GCC 6.3.0, Linux 4.11-rc8
on an Intel host with Ubuntu 14.04.5). Just tilegx/pro is still broken
due to toolchain issues.

So I wonder what the process is to get those compilers updated?

And what is a good build setup, so that the binaries run on as many
systems as possible?

Also the web page (https://www.kernel.org/pub/tools/crosstool) seems to
only link outdated builds (4.6.3, mostly), is that on purpose?

Cheers,
Andre.

[1] http://git.infradead.org/users/segher/buildall.git/