[PATCH] ARM: drop cc-option fallbacks for architecture selection

From: Arnd Bergmann <arnd@kernel.org>
To: Russell King <linux@armlinux.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Antonio Terceiro <antonio.terceiro@linaro.org>,
	Naresh Kamboju <naresh.kamboju@linaro.org>,
	Sebastian Andrzej Siewior <sebastian@breakpoint.cc>,
	Matthias Klose <doko@debian.org>,
	stable@vger.kernel.org, Masahiro Yamada <masahiroy@kernel.org>,
	Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH] ARM: drop cc-option fallbacks for architecture selection
Date: Mon, 18 Oct 2021 16:07:12 +0200	[thread overview]
Message-ID: <20211018140735.3714254-1-arnd@kernel.org> (raw)

From: Arnd Bergmann <arnd@arndb.de>

Naresh and Antonio ran into a build failure with latest Debian
armhf compilers, with lots of output like

 tmp/ccY3nOAs.s:2215: Error: selected processor does not support `cpsid i' in ARM mode

As it turns out, $(cc-option) fails early here when the FPU is not
selected before CPU architecture is selected, as the compiler
option check runs before enabling -msoft-float, which causes
a problem when testing a target architecture level without an FPU:

cc1: error: '-mfloat-abi=hard': selected architecture lacks an FPU

Passing e.g. -march=armv6k+fp in place of -march=armv6k would avoid this
issue, but the fallback logic is already broken because all supported
compilers (gcc-5 and higher) are much more recent than these options,
and building with -march=armv5t as a fallback no longer works.

The best way forward that I see is to just remove all the checks, which
also has the nice side-effect of slightly improving the startup time for
'make'.

The -mtune=marvell-f option was apparently never supported by any mainline
compiler, and the custom Codesourcery gcc build that did support is
now too old to build kernels, so just use -mtune=xscale unconditionally
for those.

This should be safe to apply on all stable kernels, and will be required
in order to keep building them with gcc-11 and higher.

Reported-by: Antonio Terceiro <antonio.terceiro@linaro.org>
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Reported-by: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
Link: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=996419
Cc: Matthias Klose <doko@debian.org>
Cc: stable@vger.kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 arch/arm/Makefile | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 847c31e7c368..fa45837b8065 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -60,15 +60,15 @@ KBUILD_CFLAGS	+= $(call cc-option,-fno-ipa-sra)
 # Note that GCC does not numerically define an architecture version
 # macro, but instead defines a whole series of macros which makes
 # testing for a specific architecture or later rather impossible.
-arch-$(CONFIG_CPU_32v7M)	=-D__LINUX_ARM_ARCH__=7 -march=armv7-m -Wa,-march=armv7-m
-arch-$(CONFIG_CPU_32v7)		=-D__LINUX_ARM_ARCH__=7 $(call cc-option,-march=armv7-a,-march=armv5t -Wa$(comma)-march=armv7-a)
-arch-$(CONFIG_CPU_32v6)		=-D__LINUX_ARM_ARCH__=6 $(call cc-option,-march=armv6,-march=armv5t -Wa$(comma)-march=armv6)
+arch-$(CONFIG_CPU_32v7M)	=-D__LINUX_ARM_ARCH__=7 -march=armv7-m
+arch-$(CONFIG_CPU_32v7)		=-D__LINUX_ARM_ARCH__=7 -march=armv7-a
+arch-$(CONFIG_CPU_32v6)		=-D__LINUX_ARM_ARCH__=6 -march=armv6
 # Only override the compiler option if ARMv6. The ARMv6K extensions are
 # always available in ARMv7
 ifeq ($(CONFIG_CPU_32v6),y)
-arch-$(CONFIG_CPU_32v6K)	=-D__LINUX_ARM_ARCH__=6 $(call cc-option,-march=armv6k,-march=armv5t -Wa$(comma)-march=armv6k)
+arch-$(CONFIG_CPU_32v6K)	=-D__LINUX_ARM_ARCH__=6 -march=armv6k
 endif
-arch-$(CONFIG_CPU_32v5)		=-D__LINUX_ARM_ARCH__=5 $(call cc-option,-march=armv5te,-march=armv4t)
+arch-$(CONFIG_CPU_32v5)		=-D__LINUX_ARM_ARCH__=5 -march=armv5te
 arch-$(CONFIG_CPU_32v4T)	=-D__LINUX_ARM_ARCH__=4 -march=armv4t
 arch-$(CONFIG_CPU_32v4)		=-D__LINUX_ARM_ARCH__=4 -march=armv4
 arch-$(CONFIG_CPU_32v3)		=-D__LINUX_ARM_ARCH__=3 -march=armv3m
@@ -82,7 +82,7 @@ tune-$(CONFIG_CPU_ARM720T)	=-mtune=arm7tdmi
 tune-$(CONFIG_CPU_ARM740T)	=-mtune=arm7tdmi
 tune-$(CONFIG_CPU_ARM9TDMI)	=-mtune=arm9tdmi
 tune-$(CONFIG_CPU_ARM940T)	=-mtune=arm9tdmi
-tune-$(CONFIG_CPU_ARM946E)	=$(call cc-option,-mtune=arm9e,-mtune=arm9tdmi)
+tune-$(CONFIG_CPU_ARM946E)	=-mtune=arm9e
 tune-$(CONFIG_CPU_ARM920T)	=-mtune=arm9tdmi
 tune-$(CONFIG_CPU_ARM922T)	=-mtune=arm9tdmi
 tune-$(CONFIG_CPU_ARM925T)	=-mtune=arm9tdmi
@@ -90,11 +90,11 @@ tune-$(CONFIG_CPU_ARM926T)	=-mtune=arm9tdmi
 tune-$(CONFIG_CPU_FA526)	=-mtune=arm9tdmi
 tune-$(CONFIG_CPU_SA110)	=-mtune=strongarm110
 tune-$(CONFIG_CPU_SA1100)	=-mtune=strongarm1100
-tune-$(CONFIG_CPU_XSCALE)	=$(call cc-option,-mtune=xscale,-mtune=strongarm110) -Wa,-mcpu=xscale
-tune-$(CONFIG_CPU_XSC3)		=$(call cc-option,-mtune=xscale,-mtune=strongarm110) -Wa,-mcpu=xscale
-tune-$(CONFIG_CPU_FEROCEON)	=$(call cc-option,-mtune=marvell-f,-mtune=xscale)
-tune-$(CONFIG_CPU_V6)		=$(call cc-option,-mtune=arm1136j-s,-mtune=strongarm)
-tune-$(CONFIG_CPU_V6K)		=$(call cc-option,-mtune=arm1136j-s,-mtune=strongarm)
+tune-$(CONFIG_CPU_XSCALE)	=-mtune=xscale
+tune-$(CONFIG_CPU_XSC3)		=-mtune=xscale
+tune-$(CONFIG_CPU_FEROCEON)	=-mtune=xscale
+tune-$(CONFIG_CPU_V6)		=-mtune=arm1136j-s
+tune-$(CONFIG_CPU_V6K)		=-mtune=arm1136j-s
 
 # Evaluate tune cc-option calls now
 tune-y := $(tune-y)
-- 
2.29.2


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