Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20220126171442.1338740-1-aurelien@aurel32.net>
In-Reply-To: <20220126171442.1338740-1-aurelien@aurel32.net>
From:   Alexandre Ghiti <alexandre.ghiti@canonical.com>
Date:   Fri, 28 Jan 2022 11:05:26 +0100
Message-ID: <CA+zEjCvwsM=DaUqB8Hv_=dXRdauz6hjeFE1MK_A6=QjrsW2EyQ@mail.gmail.com>
Subject: Re: [PATCH] riscv: fix build with binutils 2.38
To:     Aurelien Jarno <aurelien@aurel32.net>
Cc:     linux-kernel@vger.kernel.org, stable@vger.kernel.org,
        Kito Cheng <kito.cheng@gmail.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        "open list:RISC-V ARCHITECTURE" <linux-riscv@lists.infradead.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Hi Aurelien,

On Wed, Jan 26, 2022 at 6:41 PM Aurelien Jarno <aurelien@aurel32.net> 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@vger.kernel.org # 4.15+
> Cc: Kito Cheng <kito.cheng@gmail.com>
> Signed-off-by: Aurelien Jarno <aurelien@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)
>
> --
> 2.34.1
>
>

That fixes our kernel build with the new binutils, so you can add:

Tested-by: Alexandre Ghiti <alexandre.ghiti@canonical.com>

Thanks for working on this!

Alex

> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv