On 1 Jul 2024, at 20:36, Miguel Ojeda wrote: > Rust 1.79.0 has introduced a new codegen flag, `-Zub-checks` [1], to > allow to independently configure (from `-Cdebug-assertions`) whether the > extra runtime checks for UB are emitted, in a similar fashion to > `-Coverflow-checks`. > > This allows to configure the kernel with only the UB checks enabled, > but not the `debug_assert!`s; or vice versa, e.g. [2]. > > It also showcases how `RUSTC_VERSION` and the Kbuild macros, introduced > in the previous commit, can be used. > > Link: https://github.com/rust-lang/compiler-team/issues/725 [1] > Link: https://godbolt.org/z/jY69ezx5K [2] > Signed-off-by: Miguel Ojeda <ojeda@xxxxxxxxxx> Reviewed-by: Finn Behrens <me@xxxxxxxxxx> > --- > Makefile | 9 +++++++-- > lib/Kconfig.debug | 18 ++++++++++++++++++ > 2 files changed, 25 insertions(+), 2 deletions(-) > > diff --git a/Makefile b/Makefile > index 3f43f03f855e..c0cb5c237c26 100644 > --- a/Makefile > +++ b/Makefile > @@ -820,10 +820,15 @@ KBUILD_CFLAGS += -Os > KBUILD_RUSTFLAGS += -Copt-level=s > endif > > -# Always set `debug-assertions` and `overflow-checks` because their default > -# depends on `opt-level` and `debug-assertions`, respectively. > +# Always set `debug-assertions` because its default depends on `opt-level`. > KBUILD_RUSTFLAGS += -Cdebug-assertions=$(if $(CONFIG_RUST_DEBUG_ASSERTIONS),y,n) > + > +# Always set `overflow-checks` and `ub-checks` because their default depends on > +# `debug-assertions`. > KBUILD_RUSTFLAGS += -Coverflow-checks=$(if $(CONFIG_RUST_OVERFLOW_CHECKS),y,n) > +ifeq ($(call rustc-min-version, 107900),y) > +KBUILD_RUSTFLAGS += -Zub-checks=$(if $(CONFIG_RUST_UNDEFINED_BEHAVIOR_CHECKS),y,n) > +endif > > # Tell gcc to never replace conditional load with a non-conditional one > ifdef CONFIG_CC_IS_GCC > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > index 59b6765d86b8..6b4f512f9e13 100644 > --- a/lib/Kconfig.debug > +++ b/lib/Kconfig.debug > @@ -3020,6 +3020,24 @@ config RUST_OVERFLOW_CHECKS > > If unsure, say Y. > > +config RUST_UNDEFINED_BEHAVIOR_CHECKS > + bool "Undefined Behavior checks" > + depends on RUST && RUSTC_VERSION >= 107900 > + help > + Enables rustc's `-Zub-checks` codegen option. > + > + This flag allows you to control whether additional runtime checks that > + detect some causes of Undefined Behavior at runtime will be emitted. > + When enabled, a Rust panic will occur if UB is detected. > + > + All checks are generated on a best-effort basis; even if there is a check > + implemented for some cause of Undefined Behavior, it may be possible for > + the check to not fire. > + > + Note that this will apply to all Rust code, including `core`. > + > + If unsure, say N. > + > config RUST_BUILD_ASSERT_ALLOW > bool "Allow unoptimized build-time assertions" > depends on RUST > -- > 2.45.2
