On Tue, Aug 20, 2024 at 9:49 PM Matthew Maurer <mmaurer@xxxxxxxxxx> wrote:
>
> Rust supports KASAN via LLVM, but prior to this patch, the flags aren't
> set properly.
>
> Suggested-by: Miguel Ojeda <ojeda@xxxxxxxxxx>
> Signed-off-by: Matthew Maurer <mmaurer@xxxxxxxxxx>
> ---
> scripts/Makefile.kasan | 57 ++++++++++++++++++++++++---------
> scripts/Makefile.lib | 3 ++
> scripts/generate_rust_target.rs | 1 +
> 3 files changed, 45 insertions(+), 16 deletions(-)
>
> diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
> index aab4154af00a..97570df40a98 100644
> --- a/scripts/Makefile.kasan
> +++ b/scripts/Makefile.kasan
> @@ -12,6 +12,11 @@ endif
> KASAN_SHADOW_OFFSET ?= $(CONFIG_KASAN_SHADOW_OFFSET)
>
> cc-param = $(call cc-option, -mllvm -$(1), $(call cc-option, --param $(1)))
> +rustc-param = $(call rustc-option, -Cllvm-args=-$(1),)
> +
> +check-args = $(foreach arg,$(2),$(call $(1),$(arg)))
> +
> +kasan_params :=
>
> ifdef CONFIG_KASAN_STACK
> stack_enable := 1
> @@ -41,39 +46,59 @@ CFLAGS_KASAN := $(call cc-option, -fsanitize=kernel-address \
> $(call cc-option, -fsanitize=kernel-address \
> -mllvm -asan-mapping-offset=$(KASAN_SHADOW_OFFSET)))
>
> -# Now, add other parameters enabled similarly in both GCC and Clang.
> -# As some of them are not supported by older compilers, use cc-param.
> -CFLAGS_KASAN += $(call cc-param,asan-instrumentation-with-call-threshold=$(call_threshold)) \
> - $(call cc-param,asan-stack=$(stack_enable)) \
> - $(call cc-param,asan-instrument-allocas=1) \
> - $(call cc-param,asan-globals=1)
> +# The minimum supported `rustc` version has a minimum supported LLVM
> +# version late enough that we can assume support for -asan-mapping-offset.
> +RUSTFLAGS_KASAN := -Zsanitizer=kernel-address \
> + -Zsanitizer-recover=kernel-address \
> + -Cllvm-args=-asan-mapping-offset=$(KASAN_SHADOW_OFFSET)
> +
> +# Now, add other parameters enabled similarly in GCC, Clang, and rustc.
> +# As some of them are not supported by older compilers, these will be filtered
> +# through `cc-param` or `rust-param` as applicable.
> +kasan_params += asan-instrumentation-with-call-threshold=$(call_threshold) \
> + asan-stack=$(stack_enable) \
> + asan-instrument-allocas=1 \
> + asan-globals=1
>
> # Instrument memcpy/memset/memmove calls by using instrumented __asan_mem*()
> # instead. With compilers that don't support this option, compiler-inserted
> # memintrinsics won't be checked by KASAN on GENERIC_ENTRY architectures.
> -CFLAGS_KASAN += $(call cc-param,asan-kernel-mem-intrinsic-prefix=1)
> +kasan_params += asan-kernel-mem-intrinsic-prefix=1
>
> endif # CONFIG_KASAN_GENERIC
>
> ifdef CONFIG_KASAN_SW_TAGS
>
> +CFLAGS_KASAN := -fsanitize=kernel-hwaddress
> +
> +# This sets flags that will enable KHWASAN once enabled in Rust. These will
Nit: the kernel doesn't use the term KHWASAN, it's SW_TAGS KASAN or
Software Tag-Based KASAN.
> +# not work today, and is guarded against in dependencies for CONFIG_RUST.
> +RUSTFLAGS_KASAN := -Zsanitizer=kernel-hwaddress \
> + -Zsanitizer-recover=kernel-hwaddress
> +
> ifdef CONFIG_KASAN_INLINE
> - instrumentation_flags := $(call cc-param,hwasan-mapping-offset=$(KASAN_SHADOW_OFFSET))
> + kasan_params += hwasan-mapping-offset=$(KASAN_SHADOW_OFFSET)
> else
> - instrumentation_flags := $(call cc-param,hwasan-instrument-with-calls=1)
> + kasan_params += hwasan-instrument-with-calls=1
> endif
>
> -CFLAGS_KASAN := -fsanitize=kernel-hwaddress \
> - $(call cc-param,hwasan-instrument-stack=$(stack_enable)) \
> - $(call cc-param,hwasan-use-short-granules=0) \
> - $(call cc-param,hwasan-inline-all-checks=0) \
> - $(instrumentation_flags)
> +kasan_params += hwasan-instrument-stack=$(stack_enable) \
> + hwasan-use-short-granules=0 \
> + hwasan-inline-all-checks=0
>
> # Instrument memcpy/memset/memmove calls by using instrumented __hwasan_mem*().
> ifeq ($(call clang-min-version, 150000)$(call gcc-min-version, 130000),y)
> - CFLAGS_KASAN += $(call cc-param,hwasan-kernel-mem-intrinsic-prefix=1)
> + kasan_params += hwasan-kernel-mem-intrinsic-prefix=1
> endif
>
> endif # CONFIG_KASAN_SW_TAGS
>
> -export CFLAGS_KASAN CFLAGS_KASAN_NOSANITIZE
> +# Add all as-supported KASAN LLVM parameters requested by the configuration.
> +CFLAGS_KASAN += $(call check-args, cc-param, $(kasan_params))
> +
> +ifdef CONFIG_RUST
> + # Avoid calling `rustc-param` unless Rust is enabled.
> + RUSTFLAGS_KASAN += $(call check-args, rustc-param, $(kasan_params))
> +endif # CONFIG_RUST
> +
> +export CFLAGS_KASAN CFLAGS_KASAN_NOSANITIZE RUSTFLAGS_KASAN
> diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> index 9f06f6aaf7fc..4a58636705e0 100644
> --- a/scripts/Makefile.lib
> +++ b/scripts/Makefile.lib
> @@ -167,6 +167,9 @@ ifneq ($(CONFIG_KASAN_HW_TAGS),y)
> _c_flags += $(if $(patsubst n%,, \
> $(KASAN_SANITIZE_$(target-stem).o)$(KASAN_SANITIZE)$(is-kernel-object)), \
> $(CFLAGS_KASAN), $(CFLAGS_KASAN_NOSANITIZE))
> +_rust_flags += $(if $(patsubst n%,, \
> + $(KASAN_SANITIZE_$(target-stem).o)$(KASAN_SANITIZE)$(is-kernel-object)), \
> + $(RUSTFLAGS_KASAN))
> endif
> endif
>
> diff --git a/scripts/generate_rust_target.rs b/scripts/generate_rust_target.rs
> index ced405d35c5d..c24c2abd67db 100644
> --- a/scripts/generate_rust_target.rs
> +++ b/scripts/generate_rust_target.rs
> @@ -192,6 +192,7 @@ fn main() {
> }
> ts.push("features", features);
> ts.push("llvm-target", "x86_64-linux-gnu");
> + ts.push("supported-sanitizers", ["kernel-address"]);
> ts.push("target-pointer-width", "64");
> } else if cfg.has("LOONGARCH") {
> panic!("loongarch uses the builtin rustc loongarch64-unknown-none-softfloat target");
> --
> 2.46.0.184.g6999bdac58-goog
>
