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Date: Fri, 26 Mar 2021 18:56:29 -0700 From: Fangrui Song <maskray@...gle.com> To: Nathan Chancellor <nathan@...nel.org> Cc: kernel test robot <lkp@...el.com>, Palmer Dabbelt <palmer@...belt.com>, Paul Walmsley <paul.walmsley@...ive.com>, Albert Ou <aou@...s.berkeley.edu>, kbuild-all@...ts.01.org, clang-built-linux@...glegroups.com, linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] riscv: Use $(LD) instead of $(CC) to link vDSO On 2021-03-26, Nathan Chancellor wrote: >On Sat, Mar 27, 2021 at 12:05:34AM +0800, kernel test robot wrote: >> Hi Nathan, >> >> I love your patch! Yet something to improve: >> >> [auto build test ERROR on linus/master] >> [also build test ERROR on v5.12-rc4 next-20210326] >> [If your patch is applied to the wrong git tree, kindly drop us a note. >> And when submitting patch, we suggest to use '--base' as documented in >> https://git-scm.com/docs/git-format-patch] >> >> url: https://github.com/0day-ci/linux/commits/Nathan-Chancellor/riscv-Use-LD-instead-of-CC-to-link-vDSO/20210326-055421 >> base: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 002322402dafd846c424ffa9240a937f49b48c42 >> config: riscv-randconfig-r032-20210326 (attached as .config) >> compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project f490a5969bd52c8a48586f134ff8f02ccbb295b3) >> reproduce (this is a W=1 build): >> wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross >> chmod +x ~/bin/make.cross >> # install riscv cross compiling tool for clang build >> # apt-get install binutils-riscv64-linux-gnu >> # https://github.com/0day-ci/linux/commit/dfdcaf93f40f0d15ffc3f25128442c1688e612d6 >> git remote add linux-review https://github.com/0day-ci/linux >> git fetch --no-tags linux-review Nathan-Chancellor/riscv-Use-LD-instead-of-CC-to-link-vDSO/20210326-055421 >> git checkout dfdcaf93f40f0d15ffc3f25128442c1688e612d6 >> # save the attached .config to linux build tree >> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=riscv > >For the record, I tried to use this script to reproduce but it has a >couple of bugs: > >1. It does not download the right version of clang. This report says >that it is clang-13 but the one that the script downloaded is clang-12. > >2. It does not download it to the right location. The script expects >~/0day/clang-latest but it is downloaded to ~/0day/clang it seems. I >symlinked it to get around it. > >> If you fix the issue, kindly add following tag as appropriate >> Reported-by: kernel test robot <lkp@...el.com> >> >> All errors (new ones prefixed by >>): >> >> >> riscv64-linux-gnu-objcopy: 'arch/riscv/kernel/vdso/vdso.so.dbg': No such file > >This error only occurs because of errors before it that are not shown >due to a denylist: > >ld.lld: error: arch/riscv/kernel/vdso/rt_sigreturn.o:(.text+0x0): relocation R_RISCV_ALIGN requires unimplemented linker relaxation; recompile with -mno-relax >ld.lld: error: arch/riscv/kernel/vdso/getcpu.o:(.text+0x0): relocation R_RISCV_ALIGN requires unimplemented linker relaxation; recompile with -mno-relax >ld.lld: error: arch/riscv/kernel/vdso/flush_icache.o:(.text+0x0): relocation R_RISCV_ALIGN requires unimplemented linker relaxation; recompile with -mno-relax > >My patch only adds another occurrence of this error because we move from >$(CC)'s default linker (in clang's case, ld.bfd) to $(LD), which in the >case of 0day appears to be ld.lld. ld.lld should not be used with RISC-V >in its current form due to errors of this nature, which happen without >my patch as well: > >https://github.com/ClangBuiltLinux/linux/issues/1020 > >Linker relaxation in ld.lld for RISC-V is an ongoing debate/process. >Please give RISC-V the current treatment as s390 with ld.lld for the >time being to get meaningful reports. We will reach out once that issue >has been resolved. >TL;DR: Patch exposes existing issue with LD=ld.lld that would have >happened without it in different areas, the report can be ignored. Yes, lkp frequently reports this error. It can be suppressed by using -mno-relax... if ld.lld is picked. Hmm. This motivated me to file https://github.com/riscv/riscv-elf-psabi-doc/issues/183 R_RISCV_ALIGN friendly to linkers not supporting relaxation (riscv_relax_delete_bytes). >Cheers! >Nathan > >-- >You received this message because you are subscribed to the Google Groups "Clang Built Linux" group. >To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@...glegroups.com. >To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/20210326235839.zgfvmtfxrb3hy6i4%40archlinux-ax161.
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