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> --- 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
