Messages in this thread | | | Date | Tue, 25 Jul 2023 19:57:54 +0100 | From | Conor Dooley <> | Subject | Re: [PATCH] riscv: Handle zicsr/zifencei issue between gcc and binutils |
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On Tue, Jul 25, 2023 at 10:23:44AM -0700, 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 :/ > > > 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?
Yeah, that'd be great to know, at least the other niche stuff that we are working around had a clear use-case (testing LLVM in debian containers) whereas there's no clear user for this. That's doubly interesting, as this patch seems to break things for binutils < 2.35, and if we have to make a trade-off between those too, then it'd be good to be able to weigh up the options. Do we perhaps need the misa-spec workaround instead for this case? Haven't tested that though, trying to dig myself out of email backlog.
> > 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
btw, please make these regular Link: tags (with a [N] at EOL) and drop the space between them and the sign off. Also, this probably needs to be CC: stable@vger.kernel.org too.
Cheers, Conor.
> > > > 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 > > 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) > > > 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 > >
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