From mboxrd@z Thu Jan  1 00:00:00 1970
From: mikpelinux@gmail.com (Mikael Pettersson)
Date: Tue, 28 Jan 2014 15:38:14 +0100
Subject: Building with gcc 4.6.4
In-Reply-To: <20140128120150.GG15937@n2100.arm.linux.org.uk>
References: <20140128120150.GG15937@n2100.arm.linux.org.uk>
Message-ID: <21223.49366.479579.145000@gargle.gargle.HOWL>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

Russell King - ARM Linux writes:
 > So, yesterday I built gcc 4.6.4 (mainline) for the autobuilder, and the
 > result is that every build failed with the same error:
 > 
 > scripts/mod/empty.c:1:0: error: FPA is unsupported in the AAPCS
 > 
 > This seems to be because linux-elf targets default to fpe3 in mainline
 > gcc, but specifying -mabi=aapcs-linux switches us into EABI mode where
 > the compiler errors out with the default FPU.
 > 
 > Hence, I believe we need this to ensure that a compatible VFP is
 > selected.  One can argue that building EABI ARMv4 with VFP is silly,
 > but it seems that's what the gcc folk have decided (rightly or
 > wrongly.)
 > 
 > Maybe this is a bug in mainline GCC - which begs the question why
 > (presumably, since no one has picked this up) Linaro's toolchain
 > has fixes but mainline GCC doesn't.
 > 
 > Comments?

Perhaps because most ARM EABI toolchains default to soft-float,
and the hardfloat ones usually select v6 or v7 + vfp-d16 or neon
as their defaults, so the archaic FPA is never the default.

Or are you using an OABI toolchain to compile an EABI kernel?

/Mikael