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From:   Mingzheng Xing <xingmingzheng@iscas.ac.cn>
To:     Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Tom Rix <trix@redhat.com>
Cc:     Bin Meng <bmeng@tinylab.org>, linux-riscv@lists.infradead.org,
        linux-kernel@vger.kernel.org, llvm@lists.linux.dev,
        Mingzheng Xing <xingmingzheng@iscas.ac.cn>
Subject: [PATCH] riscv: Handle zicsr/zifencei issue between gcc and binutils
Date:   Wed, 26 Jul 2023 01:04:05 +0800
Message-Id: <20230725170405.251011-1-xingmingzheng@iscas.ac.cn>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
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When compiling the kernel with the toolchain composed of GCC >= 12.1.0 and
binutils < 2.38, default ISA spec used when building binutils and GCC, the
following build failure will appear because the
CONFIG_TOOLCHAIN_NEEDS_EXPLICIT_ZICSR_ZIFENCEI is not turned on.
(i.e, gcc-12.1.0 and binutils-2.36, or gcc-12.3.0 and binutils-2.37, use
default ISA spec.)

  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:79: Error: unrecognized opcode `csrr a5,0xc01'

Binutils has updated the default ISA spec version, and the community has
responded well to this[1][2][3], but it appears that this is not over yet.

We also need to consider the situation of binutils < 2.38 but
GCC >= 12.1.0, since the combination between different versions of GCC and
binutils is not unique, which is to some extent flexible. GCC release
12.1.0 updated the default ISA spec version in GCC commit[4].

For more information, please refer to:

commit 6df2a016c0c8 ("riscv: fix build with binutils 2.38")
commit e89c2e815e76 ("riscv: Handle zicsr/zifencei issues between clang and binutils")

[1]: https://groups.google.com/a/groups.riscv.org/g/sw-dev/c/aE1ZeHHCYf4
[2]: https://lore.kernel.org/all/20230308220842.1231003-1-conor@kernel.org
[3]: https://lore.kernel.org/all/20230223220546.52879-1-conor@kernel.org
[4]: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=98416dbb0a62579d4a7a4a76bab51b5b52fec2cd

Signed-off-by: Mingzheng Xing <xingmingzheng@iscas.ac.cn>
---
 arch/riscv/Kconfig | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 4c07b9189c86..b49cea30f6cc 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -570,11 +570,15 @@ config TOOLCHAIN_HAS_ZIHINTPAUSE
 config TOOLCHAIN_NEEDS_EXPLICIT_ZICSR_ZIFENCEI
 	def_bool y
 	# https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=aed44286efa8ae8717a77d94b51ac3614e2ca6dc
-	depends on AS_IS_GNU && AS_VERSION >= 23800
+	# https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=98416dbb0a62579d4a7a4a76bab51b5b52fec2cd
+	depends on CC_IS_GCC && GCC_VERSION >= 120100 || \
+		   AS_IS_GNU && AS_VERSION >= 23800
 	help
 	  Newer binutils versions default to ISA spec version 20191213 which
 	  moves some instructions from the I extension to the Zicsr and Zifencei
 	  extensions.
+	  Similarly, GCC release 12.1.0 has changed the default ISA spec version to
+	  20191213, so the above situation requires this option to be enabled.
 
 config TOOLCHAIN_NEEDS_OLD_ISA_SPEC
 	def_bool y
-- 
2.34.1