On Tue, 19 Nov 2019, Randy Dunlap wrote: > On 11/19/19 8:12 AM, Marco Elver wrote: > > On Tue, 19 Nov 2019 at 16:11, Randy Dunlap <rdunlap@xxxxxxxxxxxxx> wrote: > >> > >> On 11/19/19 12:46 AM, Stephen Rothwell wrote: > >>> Hi all, > >>> > >>> Changes since 20191118: > >>> > >> > >> on x86_64: > >> > >> It seems that this function can already be known by the compiler as a > >> builtin: > >> > >> ../kernel/kcsan/core.c:619:6: warning: conflicting types for built-in function ‘__tsan_func_exit’ [-Wbuiltin-declaration-mismatch] > >> void __tsan_func_exit(void) > >> ^~~~~~~~~~~~~~~~ > >> > >> > >> $ gcc --version > >> gcc (SUSE Linux) 7.4.1 20190905 [gcc-7-branch revision 275407] > > > > Interesting. Could you share the .config? So far I haven't been able > > to reproduce. > > Sure, it's attached. Thanks, the config did the trick, even for gcc 9.0.0. The problem is CONFIG_UBSAN=y. We haven't explicitly disallowed it like with KASAN. In principle there should be nothing wrong with KCSAN+UBSAN. There are 3 options: 1. Just disable UBSAN for KCSAN, and also disable KCSAN for UBSAN. 2. Restrict the config to not allow combining KCSAN and UBSAN. 3. Leave things as-is. Option 1 probably makes most sense, and I'll send a patch for that unless there are major objections. > > I can get the warning if I manually add -fsanitize=thread to flags for > > kcsan/core.c (but normally disabled via KCSAN_SANITIZE := n). If > > possible could you also share the output of `make V=1` for > > kcsan/core.c? > > here: > gcc -Wp,-MD,kernel/kcsan/.core.o.d -nostdinc -isystem /usr/lib64/gcc/x86_64-suse-linux/7/include -I../arch/x86/include -I./arch/x86/include/generated -I../include -I./include -I../arch/x86/include/uapi -I./arch/x86/include/generated/uapi -I../include/uapi -I./include/generated/uapi -include ../include/linux/kconfig.h -include ../include/linux/compiler_types.h -D__KERNEL__ -Wall -Wundef -Werror=strict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common -fshort-wchar -fno-PIE -Werror=implicit-function-declaration -Werror=implicit-int -Wno-format-security -std=gnu89 -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx -m64 -falign-jumps=1 -falign-loops=1 -mno-80387 -mno-fp-ret-in-387 -mpreferred-stack-boundary=3 -mskip-rax-setup -mtune=generic -mno-red-zone -mcmodel=kernel -DCONFIG_AS_CFI=1 -DCONFIG_AS_CFI_SIGNAL_FRAME=1 -DCONFIG_AS_CFI_SECTIONS=1 -DCONFIG_AS_SSSE3=1 -DCONFIG_AS_AVX=1 -DCONFIG_AS_AVX2=1 -DCONFIG_AS_AVX512=1 -DCONFIG_AS_SHA1_NI=1 -DCONFIG_AS_SHA256_NI=1 -Wno-sign-compare -fno-asynchronous-unwind-tables -fno-delete-null-pointer-checks -Wno-frame-address -Wno-format-truncation -Wno-format-overflow -O2 --param=allow-store-data-races=0 -Wframe-larger-than=2048 -fno-stack-protector -Wno-unused-but-set-variable -Wimplicit-fallthrough -Wno-unused-const-variable -fno-omit-frame-pointer -fno-optimize-sibling-calls -fno-var-tracking-assignments -Wdeclaration-after-statement -Wvla -Wno-pointer-sign -fno-strict-overflow -fno-merge-all-constants -fmerge-constants -fno-stack-check -fconserve-stack -Werror=date-time -Werror=incompatible-pointer-types -Werror=designated-init -fno-conserve-stack -fno-stack-protector -fprofile-arcs -ftest-coverage -fno-tree-loop-im -Wno-maybe-uninitialized -fsanitize=shift -fsanitize=integer-divide-by-zero -fsanitize=unreachable -fsanitize=signed-integer-overflow -fsanitize=bounds -fsanitize=object-size -fsanitize=bool -fsanitize=enum -Wno-maybe-uninitialized -I ../kernel/kcsan -I ./kernel/kcsan -DKBUILD_BASENAME='"core"' -DKBUILD_MODNAME='"core"' -c -o kernel/kcsan/core.o ../kernel/kcsan/core.c > ../kernel/kcsan/core.c:619:6: warning: conflicting types for built-in function ‘__tsan_func_exit’ [-Wbuiltin-declaration-mismatch] Adding '-fsanitize=<anything>' seems to make gcc think that these are builtins. So this is partially also a gcc problem, but if we disable all sanitizers with the runtime, then this goes away. Thanks, -- Marco
