Re: [PATCH 1/2] linux-mainline: Fix riscv64 build with binutils 2.38

[Jan Kiszka <jan.kiszka@siemens.com>]

On 01.09.22 06:52, Uladzimir Bely wrote:
> Backport of https://github.com/torvalds/linux/commit/6df2a016c0c8
> from linux-5.17.

NACK. We need to update the kernel then, either to the latest 5.4.y if
that fixes it or to a newer LTS kernel that does. We don't want to
maintain patches here for this demo purpose.

Jan

> 
> Signed-off-by: Uladzimir Bely <ubely@ilbers.de>
> ---
>  ...1-riscv-fix-build-with-binutils-2.38.patch | 50 +++++++++++++++++++
>  .../linux/linux-mainline_5.4.70.bb            |  2 +
>  2 files changed, 52 insertions(+)
>  create mode 100644 meta-isar/recipes-kernel/linux/files/0001-riscv-fix-build-with-binutils-2.38.patch
> 
> diff --git a/meta-isar/recipes-kernel/linux/files/0001-riscv-fix-build-with-binutils-2.38.patch b/meta-isar/recipes-kernel/linux/files/0001-riscv-fix-build-with-binutils-2.38.patch
> new file mode 100644
> index 00000000..d0920e54
> --- /dev/null
> +++ b/meta-isar/recipes-kernel/linux/files/0001-riscv-fix-build-with-binutils-2.38.patch
> @@ -0,0 +1,50 @@
> +From 6df2a016c0c8a3d0933ef33dd192ea6606b115e3 Mon Sep 17 00:00:00 2001
> +From: Aurelien Jarno <aurelien@aurel32.net>
> +Date: Wed, 26 Jan 2022 18:14:42 +0100
> +Subject: [PATCH] riscv: fix build with binutils 2.38
> +
> +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.
> +
> +Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
> +Tested-by: Alexandre Ghiti <alexandre.ghiti@canonical.com>
> +Cc: stable@vger.kernel.org
> +Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
> +---
> + 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)
> + 
> +-- 
> +2.35.1
> +
> diff --git a/meta-isar/recipes-kernel/linux/linux-mainline_5.4.70.bb b/meta-isar/recipes-kernel/linux/linux-mainline_5.4.70.bb
> index 644535e8..b1ae6e60 100644
> --- a/meta-isar/recipes-kernel/linux/linux-mainline_5.4.70.bb
> +++ b/meta-isar/recipes-kernel/linux/linux-mainline_5.4.70.bb
> @@ -15,6 +15,8 @@ SRC_URI += " \
>      file://no-ubifs-fs.cfg \
>      file://no-root-nfs.cfg;apply=no"
>  
> +SRC_URI_append_riscv64 = " file://0001-riscv-fix-build-with-binutils-2.38.patch"
> +
>  SRC_URI[sha256sum] = "c0b3d8085c5ba235df38b00b740e053659709e8a5ca21957a239f6bc22c45007"
>  
>  S = "${WORKDIR}/linux-${ARCHIVE_VERSION}"

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