On 7/26/23 01:23, Nathan Chancellor wrote:
Hi Mingzheng,
Thanks for the patch!
On Wed, Jul 26, 2023 at 01:04:05AM +0800, Mingzheng Xing wrote:
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'
The gift that keeps on giving :/
Yeah, but things will get better :)
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].
I suspect this combination is not too common because binutils 2.38 came out before GCC 12.1.0 but as you note, it is obviously possible. What toolchain has this combination in the wild, which would be helpful for documentation purposes?
Actually, this issue was discovered during the upgrade of the distribution openEuler for RISC-V. It is a temporary phenomenon caused by inconsistent upgrade speeds of packages such as GCC and binutils. From my limited understanding, GCC and binutils are not strictly version-bound in some other distributions, so I can't rule out this issue happening in other scenarios. But once it happens it can cause problems with compiling the kernel.
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")
Signed-off-by: Mingzheng Xingxingmingzheng@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%3Ba=commit%3Bh=aed44286efa8ae...
- depends on AS_IS_GNU && AS_VERSION >= 23800
- #https://gcc.gnu.org/git/?p=gcc.git%3Ba=commit%3Bh=98416dbb0a62579d4a7a4a76ba...
- depends on CC_IS_GCC && GCC_VERSION >= 120100 || \
AS_IS_GNU && AS_VERSION >= 23800
GCC_VERSION will be 0 for clang, so you don't need the CC_IS_GCC check. With that change, this should be able to stay on one line:
depends on GCC_VERSION >= 120100 || (AS_IS_GNU && AS_VERSION >= 23800)
OK, I'll change it in v2.
Thanks, Mingzheng.
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
Cheers, Nathan
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