Rust supports ThreadSanitizer instrumentation via LLVM, which is what KCSAN relies on; however, Rust code is not currently instrumented.
Pass -Zsanitizer=thread and the same TSan backend options used for C code to rustc. Wire up KCSAN_SANITIZE in scripts/Makefile.lib for parity with C (though rustc currently rejects linking crates with mismatched instrumentation). rustc only accepts -Zsanitizer=thread for targets that declare support for it. Of the targets used by the kernel, this is only possible for the generated x86_64 target specification, so restrict instrumentation of Rust code to x86_64 for now via HAVE_KCSAN_RUSTC. On other architectures Rust code remains uninstrumented as before. All TSan options used are supported by the LLVM versions of the minimum supported rustc, so no rustc-option checks are needed (they would also fail, because x86_64-unknown-none used for option checks does not support -Zsanitizer=thread). With this enabled we can detect data races in kernel Rust code and between Rust and C code. Signed-off-by: Marco Elver <[email protected]> --- Documentation/dev-tools/kcsan.rst | 7 +++++++ lib/Kconfig.kcsan | 7 +++++++ scripts/Makefile.kcsan | 13 +++++++++++++ scripts/Makefile.lib | 3 +++ scripts/generate_rust_target.rs | 2 +- 5 files changed, 31 insertions(+), 1 deletion(-) diff --git a/Documentation/dev-tools/kcsan.rst b/Documentation/dev-tools/kcsan.rst index 8575178aa87f..3bb8754f844b 100644 --- a/Documentation/dev-tools/kcsan.rst +++ b/Documentation/dev-tools/kcsan.rst @@ -14,6 +14,9 @@ Usage KCSAN is supported by both GCC and Clang. With GCC we require version 11 or later, and with Clang also require version 11 or later. +Rust code is instrumented as well on architectures whose Rust target supports +it (currently only x86_64; see ``CONFIG_HAVE_KCSAN_RUSTC``). + To enable KCSAN configure the kernel with:: CONFIG_KCSAN = y @@ -121,6 +124,10 @@ the below options are available: KCSAN_SANITIZE := n + Note that ``rustc`` rejects linking crates built with and without KCSAN + instrumentation, so ``KCSAN_SANITIZE`` and ``KCSAN_SANITIZE_<target>.o`` + cannot currently be used for Rust code. + .. _"Marking Shared-Memory Accesses" in the LKMM: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/memory-model/Documentation/access-marking.txt Furthermore, it is possible to tell KCSAN to show or hide entire classes of diff --git a/lib/Kconfig.kcsan b/lib/Kconfig.kcsan index 4ce4b0c0109c..f0096e1c8b61 100644 --- a/lib/Kconfig.kcsan +++ b/lib/Kconfig.kcsan @@ -10,6 +10,13 @@ config HAVE_KCSAN_COMPILER For the list of compilers that support KCSAN, please see <file:Documentation/dev-tools/kcsan.rst>. +config HAVE_KCSAN_RUSTC + def_bool RUST && X86_64 + help + rustc only accepts -Zsanitizer=thread for targets that declare + support for it; of the kernel's Rust targets, only x86_64 does. + Elsewhere, Rust code is not instrumented. + menuconfig KCSAN bool "KCSAN: dynamic data race detector" depends on HAVE_ARCH_KCSAN && HAVE_KCSAN_COMPILER diff --git a/scripts/Makefile.kcsan b/scripts/Makefile.kcsan index 19f693b68a96..01af6fd71006 100644 --- a/scripts/Makefile.kcsan +++ b/scripts/Makefile.kcsan @@ -24,3 +24,16 @@ kcsan-cflags += $(call cc-option,$(call cc-param,tsan-instrument-func-entry-exit endif export CFLAGS_KCSAN := $(kcsan-cflags) + +ifdef CONFIG_HAVE_KCSAN_RUSTC +# The minimum supported rustc's LLVM supports all of these options. +rustc-param = -Cllvm-args=-$(1) +kcsan-rustflags := -Zsanitizer=thread \ + $(call rustc-param,tsan-compound-read-before-write=1) \ + $(call rustc-param,tsan-distinguish-volatile=1) +ifndef CONFIG_KCSAN_WEAK_MEMORY +kcsan-rustflags += $(call rustc-param,tsan-instrument-func-entry-exit=0) +endif +endif + +export RUSTFLAGS_KCSAN := $(kcsan-rustflags) diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib index 0a4fdd8bd975..78f1c23e54be 100644 --- a/scripts/Makefile.lib +++ b/scripts/Makefile.lib @@ -98,6 +98,9 @@ ifeq ($(CONFIG_KCSAN),y) _c_flags += $(if $(patsubst n%,, \ $(KCSAN_SANITIZE_$(target-stem).o)$(KCSAN_SANITIZE)$(is-kernel-object)), \ $(CFLAGS_KCSAN)) +_rust_flags += $(if $(patsubst n%,, \ + $(KCSAN_SANITIZE_$(target-stem).o)$(KCSAN_SANITIZE)$(is-kernel-object)), \ + $(RUSTFLAGS_KCSAN)) # Some uninstrumented files provide implied barriers required to avoid false # positives: set KCSAN_INSTRUMENT_BARRIERS for barrier instrumentation only. _c_flags += $(if $(patsubst n%,, \ diff --git a/scripts/generate_rust_target.rs b/scripts/generate_rust_target.rs index 7687b0dd5474..4b02bffa6b46 100644 --- a/scripts/generate_rust_target.rs +++ b/scripts/generate_rust_target.rs @@ -231,7 +231,7 @@ fn main() { } ts.push("features", features); ts.push("llvm-target", "x86_64-linux-gnu"); - ts.push("supported-sanitizers", ["kcfi", "kernel-address"]); + ts.push("supported-sanitizers", ["kcfi", "kernel-address", "thread"]); if cfg.rustc_version_atleast(1, 91, 0) { ts.push("target-pointer-width", 64); } else { -- 2.56.0.385.gd3acb90ef8-goog
