[PATCH] riscv: fix build with binutils 2.38

[Marc Kleine-Budde]

On 26.01.2022 18:14:42, Aurelien Jarno wrote:
> From version 2.38, binutils default to ISA spec version 20191213. This
> means that the csr read/write (csrr*/csrw*) instructions and fence.i
> instruction has separated from the `I` extension, become two standalone
> extensions: Zicsr and Zifencei. As the kernel uses those instruction,
> this causes the following build failure:
> 
>   CC      arch/riscv/kernel/vdso/vgettimeofday.o
>   <<BUILDDIR>>/arch/riscv/include/asm/vdso/gettimeofday.h: Assembler messages:
>   <<BUILDDIR>>/arch/riscv/include/asm/vdso/gettimeofday.h:71: Error: unrecognized opcode `csrr a5,0xc01'
>   <<BUILDDIR>>/arch/riscv/include/asm/vdso/gettimeofday.h:71: Error: unrecognized opcode `csrr a5,0xc01'
>   <<BUILDDIR>>/arch/riscv/include/asm/vdso/gettimeofday.h:71: Error: unrecognized opcode `csrr a5,0xc01'
>   <<BUILDDIR>>/arch/riscv/include/asm/vdso/gettimeofday.h:71: Error: unrecognized opcode `csrr a5,0xc01'
> 
> The fix is to specify those extensions explicitely in -march. However as
> older binutils version do not support this, we first need to detect
> that.
> 
> Cc: stable at vger.kernel.org # 4.15+
> Cc: Kito Cheng <kito.cheng at gmail.com>
> Signed-off-by: Aurelien Jarno <aurelien at aurel32.net>
> ---
>  arch/riscv/Makefile | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
> index 8a107ed18b0d..7d81102cffd4 100644
> --- a/arch/riscv/Makefile
> +++ b/arch/riscv/Makefile
> @@ -50,6 +50,12 @@ riscv-march-$(CONFIG_ARCH_RV32I)	:= rv32ima
>  riscv-march-$(CONFIG_ARCH_RV64I)	:= rv64ima
>  riscv-march-$(CONFIG_FPU)		:= $(riscv-march-y)fd
>  riscv-march-$(CONFIG_RISCV_ISA_C)	:= $(riscv-march-y)c
> +
> +# Newer binutils versions default to ISA spec version 20191213 which moves some
> +# instructions from the I extension to the Zicsr and Zifencei extensions.
> +toolchain-need-zicsr-zifencei := $(call cc-option-yn, -march=$(riscv-march-y)_zicsr_zifencei)
> +riscv-march-$(toolchain-need-zicsr-zifencei) := $(riscv-march-y)_zicsr_zifencei
> +
>  KBUILD_CFLAGS += -march=$(subst fd,,$(riscv-march-y))
>  KBUILD_AFLAGS += -march=$(riscv-march-y)

I'm on current linus/master, this change breaks on current Debian
testing with:

| make: Leaving directory 'linux'
|   SYNC    include/config/auto.conf.cmd
|   GEN     Makefile
|   GEN     Makefile
|   CC      scripts/mod/empty.o
|   CHECK   linux/scripts/mod/empty.c
| invalid argument to '-march': '_zicsr_zifencei'

Used components:

| $ riscv64-linux-gnu-gcc -v
| Using built-in specs.
| COLLECT_GCC=/usr/bin/riscv64-linux-gnu-gcc
| COLLECT_LTO_WRAPPER=/usr/lib/gcc-cross/riscv64-linux-gnu/11/lto-wrapper
| Target: riscv64-linux-gnu
| Configured with: ../src/configure -v --with-pkgversion='Debian 11.2.0-9' --with-bugurl=file:///usr/share/doc/gcc-11/README.Bugs --enable-languages=c,ada,c++,go,d,fortran,objc,obj-c++,m2 --prefix=/usr --with-gcc-major-version-only --program-suffix=-11 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-libitm --disable-libquadmath --disable-libquadmath-support --enable-plugin --enable-default-pie --with-system-zlib --enable-libphobos-checking=release --without-target-system-zlib --enable-multiarch --disable-werror --disable-multilib --with-arch=rv64imafdc --with-abi=lp64d --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=riscv64-linux-gnu --program-prefix=riscv64-linux-gnu- --includedir=/usr/riscv64-linux-gnu/include --with-build-config=bootstrap-lto-lean --enable-link-serialization=2
| Thread model: posix
| Supported LTO compression algorithms: zlib zstd
| gcc version 11.2.0 (Debian 11.2.0-9) 
| $ riscv64-linux-gnu-ld -v
| GNU ld (GNU Binutils for Debian) 2.38

regards,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |
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