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 <l...@intel.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
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