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Message-ID: <CA+fCnZeA_GOdqidEhP81TvwiSSgJNEoXa85ooqVpfPOk3v4S0w@mail.gmail.com>
Date: Tue, 20 Aug 2024 19:30:41 +0200
From: Andrey Konovalov <andreyknvl@...il.com>
To: Matthew Maurer <mmaurer@...gle.com>
Cc: dvyukov@...gle.com, ojeda@...nel.org,
Andrey Ryabinin <ryabinin.a.a@...il.com>, Masahiro Yamada <masahiroy@...nel.org>,
Alex Gaynor <alex.gaynor@...il.com>, Wedson Almeida Filho <wedsonaf@...il.com>,
Nathan Chancellor <nathan@...nel.org>, aliceryhl@...gle.com, samitolvanen@...gle.com,
kasan-dev@...glegroups.com, linux-mm@...ck.org, glider@...gle.com,
Nicolas Schier <nicolas@...sle.eu>, Vincenzo Frascino <vincenzo.frascino@....com>,
Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
Björn Roy Baron <bjorn3_gh@...tonmail.com>,
Benno Lossin <benno.lossin@...ton.me>, Andreas Hindborg <a.hindborg@...sung.com>,
Nick Desaulniers <ndesaulniers@...gle.com>, Bill Wendling <morbo@...gle.com>,
Justin Stitt <justinstitt@...gle.com>, linux-kbuild@...r.kernel.org,
linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org,
llvm@...ts.linux.dev
Subject: Re: [PATCH v3 2/4] kbuild: rust: Enable KASAN support
On Mon, Aug 19, 2024 at 11:35 PM Matthew Maurer <mmaurer@...gle.com> wrote:
>
> Rust supports KASAN via LLVM, but prior to this patch, the flags aren't
> set properly.
>
> Rust hasn't yet enabled software-tagged KWHASAN (only regular HWASAN),
> so explicitly prevent Rust from being selected when it is enabled.
This is done in the next patch, not in this one.
> Suggested-by: Miguel Ojeda <ojeda@...nel.org>
> Signed-off-by: Matthew Maurer <mmaurer@...gle.com>
> ---
> scripts/Makefile.kasan | 54 +++++++++++++++++++++++----------
> scripts/Makefile.lib | 3 ++
> scripts/generate_rust_target.rs | 1 +
> 3 files changed, 42 insertions(+), 16 deletions(-)
>
> diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
> index aab4154af00a..163640fdefa0 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 +46,56 @@ 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) \
> - $(call cc-param,asan-globals=1)
> +# The minimum supported `rustc` version has a minimum supported LLVM
> +# version late enough that we can assume support for -asan-mapping-offset
Nit: dot at the end.
> +RUSTFLAGS_KASAN := -Zsanitizer=kernel-address \
> + -Zsanitizer-recover=kernel-address \
> + -Cllvm-args=-asan-mapping-offset=$(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
>
> 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
Let's put these kasan_params parts after CFLAGS_KASAN.
> +
> +CFLAGS_KASAN := -fsanitize=kernel-hwaddress
> +RUSTFLAGS_KASAN := -Zsanitizer=kernel-hwaddress \
> + -Zsanitizer-recover=kernel-hwaddress
What's the intention of defining RUSTFLAGS_KASAN for SW_TAGS if it's
not supported by Rust? Should this be removed?
If this is just a foundation for potential future support of
Rust+SW_TAGS, please add a comment explaining this. And also please
put the patch that disallows Rust+SW_TAGS before this one, if you keep
RUSTFLAGS_KASAN.
> # 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
Nit: dot at the end.
> +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
>
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