On Tue, Dec 14, 2021 at 05:20:14PM +0100, Alexander Potapenko wrote: > The new attribute maps to > __attribute__((disable_sanitizer_instrumentation)), which will be > supported by Clang >= 14.0. Future support in GCC is also possible. > > This attribute disables compiler instrumentation for kernel sanitizer > tools, making it easier to implement noinstr. It is different from the > existing __no_sanitize* attributes, which may still allow certain types > of instrumentation to prevent false positives. When you say the __no_sanitize* attributes allow some instrumentation, does that apply to any of the existing KASAN/KCSAN/KCOV support, or just for KMSAN? The documentation just says the same as the commit message: | This is not the same as __attribute__((no_sanitize(...))), which depending on | the tool may still insert instrumentation to prevent false positive reports. ... which implies the other instrumentation might not be suprressed. I ask because architectures which select ARCH_WANTS_NO_INSTR *need* to be able to suppress all instrumentation. It's fine if that means they need a new version of clang for KMSAN, but if there's latent instrumentation we have more bugs to fix first... Thanks, Mark. > Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx> > --- > Link: https://linux-review.googlesource.com/id/Ic0123ce99b33ab7d5ed1ae90593425be8d3d774a > --- > include/linux/compiler_attributes.h | 18 ++++++++++++++++++ > 1 file changed, 18 insertions(+) > > diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h > index b9121afd87331..37e2600202216 100644 > --- a/include/linux/compiler_attributes.h > +++ b/include/linux/compiler_attributes.h > @@ -308,6 +308,24 @@ > # define __compiletime_warning(msg) > #endif > > +/* > + * Optional: only supported since clang >= 14.0 > + * > + * clang: https://clang.llvm.org/docs/AttributeReference.html#disable-sanitizer-instrumentation > + * > + * disable_sanitizer_instrumentation is not always similar to > + * no_sanitize((<sanitizer-name>)): the latter may still let specific sanitizers > + * insert code into functions to prevent false positives. Unlike that, > + * disable_sanitizer_instrumentation prevents all kinds of instrumentation to > + * functions with the attribute. > + */ > +#if __has_attribute(disable_sanitizer_instrumentation) > +# define __disable_sanitizer_instrumentation \ > + __attribute__((disable_sanitizer_instrumentation)) > +#else > +# define __disable_sanitizer_instrumentation > +#endif > + > /* > * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute > * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute > -- > 2.34.1.173.g76aa8bc2d0-goog >
