On Thu, Feb 16, 2023 at 07:12AM +0000, Christophe Leroy wrote: > > > Le 16/02/2023 à 06:09, Rohan McLure a écrit : > > KCSAN instruments calls to atomic builtins, and will in turn call these > > builtins itself. As such, architectures supporting KCSAN must have > > compiler support for these atomic primitives. > > > > Since 32-bit systems are unlikely to have 64-bit compiler builtins, > > provide a stub for each missing builtin, and use BUG() to assert > > unreachability. > > > > In commit 725aea873261 ("xtensa: enable KCSAN"), xtensa implements these > > locally. Move these definitions to be accessible to all 32-bit > > architectures that do not provide the necessary builtins, with opt in > > for PowerPC and xtensa. > > > > Signed-off-by: Rohan McLure <rmcl...@linux.ibm.com> > > Reviewed-by: Max Filippov <jcmvb...@gmail.com> > > This series should also be addressed to KCSAN Maintainers, shouldn't it ? > > KCSAN > M: Marco Elver <el...@google.com> > R: Dmitry Vyukov <dvyu...@google.com> > L: kasan-...@googlegroups.com > S: Maintained > F: Documentation/dev-tools/kcsan.rst > F: include/linux/kcsan*.h > F: kernel/kcsan/ > F: lib/Kconfig.kcsan > F: scripts/Makefile.kcsan > > > > --- > > Previously issued as a part of a patch series adding KCSAN support to > > 64-bit. > > Link: > > https://lore.kernel.org/linuxppc-dev/167646486000.1421441.10070059569986228558.b4...@ellerman.id.au/T/#t > > v1: Remove __has_builtin check, as gcc is not obligated to inline > > builtins detected using this check, but instead is permitted to supply > > them in libatomic: > > Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108734 > > Instead, opt-in PPC32 and xtensa. > > --- > > arch/xtensa/lib/Makefile | 1 - > > kernel/kcsan/Makefile | 2 ++ > > arch/xtensa/lib/kcsan-stubs.c => kernel/kcsan/stubs.c | 0 > > 3 files changed, 2 insertions(+), 1 deletion(-) > > rename arch/xtensa/lib/kcsan-stubs.c => kernel/kcsan/stubs.c (100%) > > > > diff --git a/arch/xtensa/lib/Makefile b/arch/xtensa/lib/Makefile > > index 7ecef0519a27..d69356dc97df 100644 > > --- a/arch/xtensa/lib/Makefile > > +++ b/arch/xtensa/lib/Makefile > > @@ -8,5 +8,4 @@ lib-y += memcopy.o memset.o checksum.o \ > > divsi3.o udivsi3.o modsi3.o umodsi3.o mulsi3.o umulsidi3.o \ > > usercopy.o strncpy_user.o strnlen_user.o > > lib-$(CONFIG_PCI) += pci-auto.o > > -lib-$(CONFIG_KCSAN) += kcsan-stubs.o > > KCSAN_SANITIZE_kcsan-stubs.o := n > > diff --git a/kernel/kcsan/Makefile b/kernel/kcsan/Makefile > > index 8cf70f068d92..86dd713d8855 100644 > > --- a/kernel/kcsan/Makefile > > +++ b/kernel/kcsan/Makefile > > @@ -12,6 +12,8 @@ CFLAGS_core.o := $(call cc-option,-fno-conserve-stack) \ > > -fno-stack-protector -DDISABLE_BRANCH_PROFILING > > > > obj-y := core.o debugfs.o report.o > > +obj-$(CONFIG_PPC32) += stubs.o > > +obj-$(CONFIG_XTENSA) += stubs.o > > Not sure it is acceptable to do it that way. > > There should likely be something like a CONFIG_ARCH_WANTS_KCSAN_STUBS in > KCSAN's Kconfig then PPC32 and XTENSA should select it.
The longer I think about it, since these stubs all BUG() anyway, perhaps we ought to just avoid them altogether. If you delete all the stubs from ppc and xtensa, but do this: | diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c | index 54d077e1a2dc..8169d6dadd0e 100644 | --- a/kernel/kcsan/core.c | +++ b/kernel/kcsan/core.c | @@ -1261,7 +1261,9 @@ static __always_inline void kcsan_atomic_builtin_memorder(int memorder) | DEFINE_TSAN_ATOMIC_OPS(8); | DEFINE_TSAN_ATOMIC_OPS(16); | DEFINE_TSAN_ATOMIC_OPS(32); | +#ifdef CONFIG_64BIT | DEFINE_TSAN_ATOMIC_OPS(64); | +#endif | | void __tsan_atomic_thread_fence(int memorder); | void __tsan_atomic_thread_fence(int memorder) Does that work?