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[net-next,v8,01/28] ARM: makefile: use ARMv3M mode for RiscPC

Message ID 20181018145712.7538-2-Jason@zx2c4.com (mailing list archive)
State Not Applicable
Delegated to: Herbert Xu
Headers show
Series WireGuard: Secure Network Tunnel | expand

Commit Message

Jason A. Donenfeld Oct. 18, 2018, 2:56 p.m. UTC 
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>
---

Notes:
    This commit has been submitted to the proper ARM tree and is working its
    way upstream. It's included in this series here so that kbuild 0-day bot
    doesn't get too nervous about RiscPC, but is already entering the tree
    through arm-next.

 arch/arm/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
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Patch

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)