Messages in this thread Patch in this message | | | Date | Thu, 30 Sep 2021 07:47:09 +0200 | From | Marco Elver <> | Subject | Re: [mark:arm64/kcsan 11/13] ld.lld: error: undefined symbol: __tsan_atomic64_fetch_add |
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On Thu, Sep 30, 2021 at 05:48AM +0800, kernel test robot wrote: > tree: https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git arm64/kcsan > head: 4fe9d6c2ef85257d80291086e4514eaaebd3504e > commit: f5bc7f69b328f00a6accd9a11f5981d2d0c11cb5 [11/13] kcsan: remove atomic builtin support > config: x86_64-randconfig-a011-20210929 (attached as .config) > compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project dc6e8dfdfe7efecfda318d43a06fae18b40eb498) > 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 > # https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/commit/?id=f5bc7f69b328f00a6accd9a11f5981d2d0c11cb5 > git remote add mark https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git > git fetch --no-tags mark arm64/kcsan > git checkout f5bc7f69b328f00a6accd9a11f5981d2d0c11cb5 > # save the attached .config to linux build tree > mkdir build_dir > COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash > > If you fix the issue, kindly add following tag as appropriate > Reported-by: kernel test robot <lkp@intel.com> > > All errors (new ones prefixed by >>): > > >> ld.lld: error: undefined symbol: __tsan_atomic64_fetch_add > >>> referenced by initcall.h:10 (include/trace/events/initcall.h:10) > >>> main.o:(__traceiter_initcall_level) in archive init/built-in.a > >>> referenced by initcall.h:10 (include/trace/events/initcall.h:10) > >>> main.o:(__traceiter_initcall_level) in archive init/built-in.a > >>> referenced by initcall.h:10 (include/trace/events/initcall.h:10) > >>> main.o:(__traceiter_initcall_level) in archive init/built-in.a > >>> referenced 744943 more times
This was another reason why I added the __tsan_atomic instrumentation calls -- to avoid chasing the odd driver or however this happened using builtin atomics and the blame always falling on KCSAN. ;-)
This happened more than once, and I just got frustrated and added them, also in preparation of other odd arches wanting it. I think KCSAN isn't meant to be the do-not-use-atomic-builtins linter.
If you can somehow keep them, I would prefer that, just to avoid going back to a world where I have to chase the odd builtin atomic user after they broke the KCSAN build.
Would a $(call cc-option,-mno-outline-atomics) help?
--- a/kernel/kcsan/Makefile +++ b/kernel/kcsan/Makefile @@ -8,7 +8,8 @@ CFLAGS_REMOVE_debugfs.o = $(CC_FLAGS_FTRACE) CFLAGS_REMOVE_report.o = $(CC_FLAGS_FTRACE) CFLAGS_core.o := $(call cc-option,-fno-conserve-stack) \ - -fno-stack-protector -DDISABLE_BRANCH_PROFILING + -fno-stack-protector -DDISABLE_BRANCH_PROFILING \ + $(call cc-option,-mno-outline-atomics) obj-y := core.o debugfs.o report.o obj-$(CONFIG_KCSAN_SELFTEST) += selftest.o A quick test with a compiler version which generated outline atomics suggests that this works.
Thanks, -- Marco
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