linux-kernel - Re: ld.lld: error: relocation R_RISCV_HI20 cannot be used against symbol 'misaligned_access

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Date:   Tue, 13 Jun 2023 10:16:54 +0200
From:   Alexandre Ghiti <alexghiti@...osinc.com>
To:     kernel test robot <lkp@...el.com>
Cc:     llvm@...ts.linux.dev, oe-kbuild-all@...ts.linux.dev,
        linux-kernel@...r.kernel.org, Palmer Dabbelt <palmer@...osinc.com>
Subject: Re: ld.lld: error: relocation R_RISCV_HI20 cannot be used against
 symbol 'misaligned_access_speed'; recompile with -fPIC

On Sun, Jun 11, 2023 at 2:11 AM kernel test robot <lkp@...el.com> wrote:
>
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   022ce8862dff83c859089cd14bc4dca0733e2f90
> commit: 8dc2a7e8027fbeca0c7df81d4c82e735a59b5741 riscv: Fix relocatable kernels with early alternatives using -fno-pie
> date:   10 days ago
> config: riscv-randconfig-r022-20230611 (https://download.01.org/0day-ci/archive/20230611/202306110855.7TlBCIzI-lkp@intel.com/config)
> compiler: clang version 16.0.4 (https://github.com/llvm/llvm-project.git ae42196bc493ffe877a7e3dff8be32035dea4d07)
> reproduce (this is a W=1 build):
>         mkdir -p ~/bin
>         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://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=8dc2a7e8027fbeca0c7df81d4c82e735a59b5741
>         git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
>         git fetch --no-tags linus master
>         git checkout 8dc2a7e8027fbeca0c7df81d4c82e735a59b5741
>         # save the config file
>         mkdir build_dir && cp config build_dir/.config
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang ~/bin/make.cross W=1 O=build_dir ARCH=riscv olddefconfig
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang ~/bin/make.cross W=1 O=build_dir ARCH=riscv SHELL=/bin/bash
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@...el.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202306110855.7TlBCIzI-lkp@intel.com/
>
> All errors (new ones prefixed by >>):
>
> >> ld.lld: error: relocation R_RISCV_HI20 cannot be used against symbol 'misaligned_access_speed'; recompile with -fPIC
>    >>> defined in vmlinux.a(arch/riscv/kernel/cpufeature.o)
>    >>> referenced by errata.c:42 (arch/riscv/errata/thead/errata.c:42)
>    >>>               arch/riscv/errata/thead/errata.o:(thead_feature_probe_func) in archive vmlinux.a
> --
> >> ld.lld: error: relocation R_RISCV_LO12_I cannot be used against symbol 'misaligned_access_speed'; recompile with -fPIC
>    >>> defined in vmlinux.a(arch/riscv/kernel/cpufeature.o)
>    >>> referenced by errata.c:42 (arch/riscv/errata/thead/errata.c:42)
>    >>>               arch/riscv/errata/thead/errata.o:(thead_feature_probe_func) in archive vmlinux.a
> --
> >> ld.lld: error: relocation R_RISCV_HI20 cannot be used against symbol 'riscv_cbom_block_size'; recompile with -fPIC
>    >>> defined in vmlinux.a(arch/riscv/mm/cacheflush.o)
>    >>> referenced by errata.c:42 (arch/riscv/errata/thead/errata.c:42)
>    >>>               arch/riscv/errata/thead/errata.o:(thead_errata_patch_func) in archive vmlinux.a
> --
> >> ld.lld: error: relocation R_RISCV_LO12_S cannot be used against symbol 'riscv_cbom_block_size'; recompile with -fPIC
>    >>> defined in vmlinux.a(arch/riscv/mm/cacheflush.o)
>    >>> referenced by errata.c:42 (arch/riscv/errata/thead/errata.c:42)
>    >>>               arch/riscv/errata/thead/errata.o:(thead_errata_patch_func) in archive vmlinux.a
> --
> >> ld.lld: error: relocation R_RISCV_HI20 cannot be used against symbol '__per_cpu_offset'; recompile with -fPIC
>    >>> defined in vmlinux.a(mm/percpu.o)
>    >>> referenced by errata.c:42 (arch/riscv/errata/thead/errata.c:42)
>    >>>               arch/riscv/errata/thead/errata.o:(thead_feature_probe_func) in archive vmlinux.a
> --
> >> ld.lld: error: relocation R_RISCV_LO12_I cannot be used against symbol '__per_cpu_offset'; recompile with -fPIC
>    >>> defined in vmlinux.a(mm/percpu.o)
>    >>> referenced by errata.c:42 (arch/riscv/errata/thead/errata.c:42)
>    >>>               arch/riscv/errata/thead/errata.o:(thead_feature_probe_func) in archive vmlinux.a
>

So I looked into those errors, the config is basically = RELOCATABLE +
MEDLOW - EARLY_ALTERNATIVES. Then errata/thead is not compiled as
medany, which makes sense since we only need this code to be medany
when EARLY_ALTERNATIVES is enabled (because the code would be executed
with mmu off, which is not the case here).

I can fix those errors by adding the medany flag, but I'm not sure
actually we want to do that since we do not need it and gcc does not
complain: any idea?

Alex



> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki