Le 08/02/2023 à 04:21, 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, but does not advertise the fact with preprocessor macros. To > avoid production of duplicate symbols, do not build the stubs on xtensa. > A future patch will remove the xtensa implementation of these stubs. > > Signed-off-by: Rohan McLure <rmcl...@linux.ibm.com> > --- > v4: New patch > --- > kernel/kcsan/Makefile | 3 ++ > kernel/kcsan/stubs.c | 78 +++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 81 insertions(+) > create mode 100644 kernel/kcsan/stubs.c
I think it would be better to merge patch 1 and patch 2, that way we would keep the history and see that stubs.c almost comes from xtensa. The summary would then be: arch/xtensa/lib/Makefile | 1 - kernel/kcsan/Makefile | 2 +- arch/xtensa/lib/kcsan-stubs.c => kernel/kcsan/stubs.c | 26 +++++++++++++++++++++++++- 3 files changed, 26 insertions(+), 3 deletions(-) > > diff --git a/kernel/kcsan/Makefile b/kernel/kcsan/Makefile > index 8cf70f068d92..5dfc5825aae9 100644 > --- a/kernel/kcsan/Makefile > +++ b/kernel/kcsan/Makefile > @@ -12,6 +12,9 @@ CFLAGS_core.o := $(call cc-option,-fno-conserve-stack) \ > -fno-stack-protector -DDISABLE_BRANCH_PROFILING > > obj-y := core.o debugfs.o report.o > +ifndef XTENSA > + obj-y += stubs.o obj-$(CONFIG_32BIT) += stubs.o That would avoid the #if CONFIG_32BIT in stubs.c > +endif > > KCSAN_INSTRUMENT_BARRIERS_selftest.o := y > obj-$(CONFIG_KCSAN_SELFTEST) += selftest.o > diff --git a/kernel/kcsan/stubs.c b/kernel/kcsan/stubs.c > new file mode 100644 > index 000000000000..ec5cd99be422 > --- /dev/null > +++ b/kernel/kcsan/stubs.c > @@ -0,0 +1,78 @@ > +// SPDX-License Identifier: GPL-2.0 Missing - between License and Identifier ? > + > +#include <linux/bug.h> > +#include <linux/types.h> > + > +#ifdef CONFIG_32BIT Should be handled in Makefile > + > +#if !__has_builtin(__atomic_store_8) Does any 32 bit ARCH support that ? Is that #if required ? If yes, do we really need the #if for each and every function, can't we just check for one and assume that if we don't have __atomic_store_8 we don't have any of the functions ? > +void __atomic_store_8(volatile void *p, u64 v, int i) > +{ > + BUG(); > +} > +#endif > + > +#if !__has_builtin(__atomic_load_8) > +u64 __atomic_load_8(const volatile void *p, int i) > +{ > + BUG(); > +} > +#endif > + > +#if !__has_builtin(__atomic_exchange_8) > +u64 __atomic_exchange_8(volatile void *p, u64 v, int i) > +{ > + BUG(); > +} > +#endif > + > +#if !__has_builtin(__atomic_compare_exchange_8) > +bool __atomic_compare_exchange_8(volatile void *p1, void *p2, u64 v, bool b, > int i1, int i2) > +{ > + BUG(); > +} > +#endif > + > +#if !__has_builtin(__atomic_fetch_add_8) > +u64 __atomic_fetch_add_8(volatile void *p, u64 v, int i) > +{ > + BUG(); > +} > +#endif > + > +#if !__has_builtin(__atomic_fetch_sub_8) > +u64 __atomic_fetch_sub_8(volatile void *p, u64 v, int i) > +{ > + BUG(); > +} > +#endif > + > +#if !__has_builtin(__atomic_fetch_and_8) > +u64 __atomic_fetch_and_8(volatile void *p, u64 v, int i) > +{ > + BUG(); > +} > +#endif > + > +#if !__has_builtin(__atomic_fetch_or_8) > +u64 __atomic_fetch_or_8(volatile void *p, u64 v, int i) > +{ > + BUG(); > +} > +#endif > + > +#if !__has_builtin(__atomic_fetch_xor_8) > +u64 __atomic_fetch_xor_8(volatile void *p, u64 v, int i) > +{ > + BUG(); > +} > +#endif > + > +#if !__has_builtin(__atomic_fetch_nand_8) > +u64 __atomic_fetch_nand_8(volatile void *p, u64 v, int i) > +{ > + BUG(); > +} > +#endif > + > +#endif /* CONFIG_32BIT */