[PATCH] ARM: makefile: use ARMv3M mode for RiscPC
From: Ard Biesheuvel <hidden>
Date: 2018-10-02 13:28:40
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On 2 October 2018 at 15:20, Jason A. Donenfeld [off-list ref] wrote:
The purpose of CONFIG_CPU_32v3 is to avoid ldrh/strh on the RiscPC, which is pretty much an ARMv4 device, except its bus will choke on the half-words. The way to make the C compiler not output ldrh/strh is with -march=armv3, which doesn't support them in the ISA. However, this prevents certain cryptography code from working that uses instructions like umull. Fortunately there's also -march=armv3m that does support those, making it possible to continue assembling optimized cryptography routines for our beloved RiscPC. Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Cc: Ard Biesheuvel <redacted> Cc: Russell King <linux@armlinux.org.uk> Cc: Arnd Bergmann <arnd@arndb.de>
Acked-by: Ard Biesheuvel <redacted>
quoted hunk ↗ jump to hunk
--- arch/arm/Makefile | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/arch/arm/Makefile b/arch/arm/Makefile index d1516f85f25d..7fd4bcaf0721 100644 --- a/arch/arm/Makefile +++ b/arch/arm/Makefile@@ -74,7 +74,7 @@ endif arch-$(CONFIG_CPU_32v5) =-D__LINUX_ARM_ARCH__=5 $(call cc-option,-march=armv5te,-march=armv4t) arch-$(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=armv3 +arch-$(CONFIG_CPU_32v3) =-D__LINUX_ARM_ARCH__=3 -march=armv3m # Evaluate arch cc-option calls now arch-y := $(arch-y) --2.19.0