Messages in this thread | | | Date | Thu, 27 Jul 2023 00:55:16 +0800 | From | Mingzheng Xing <> | Subject | Re: [PATCH] riscv: Handle zicsr/zifencei issue between gcc and binutils |
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On 7/26/23 06:17, Conor Dooley wrote: > On Tue, Jul 25, 2023 at 07:57:54PM +0100, Conor Dooley wrote: >> On Tue, Jul 25, 2023 at 10:23:44AM -0700, Nathan Chancellor wrote: >>> 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. > Also, I just noticed this comment. I disagree with the wording "well", > and more like "with weeping and gnashing of teeth" ;) This stuff is a > huge pain in the ass, and mixing toolchains between LLVM & GNU stuff (or > using an older binutils with a newer GCC) really makes it a lot worse. At least in the usual way , except in my unusual case... > Thanks for submitting a fix for this so that Nathan or I didn't have to! Hopefully this patch will make things better. >>>> 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. > I don't think the misa-spec stuff is what we need actually. Instead, the > workaround/fix that this patch implements just needs to be constrained to > versions of GAS greater than 2.35. I'm sorry, I didn't quite understand this, could you provide some more information, thank you very much! I'll change the handling in v2. After testing it myself, it seems to work fine.
Thanks, Mingzheng. > Thanks, > Conor. > >>>> 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. >>>> 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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