From ca627e636551e74b528f150d744f67d9a63f0ae7 Mon Sep 17 00:00:00 2001
From: Matthew Maurer <mmaurer@google.com>
Date: Thu, 12 Sep 2024 21:00:44 +0200
Subject: [PATCH] rust: cfi: add support for CFI_CLANG with Rust
Make it possible to use the Control Flow Integrity (CFI) sanitizer when
Rust is enabled. Enabling CFI with Rust requires that CFI is configured
to normalize integer types so that all integer types of the same size
and signedness are compatible under CFI.
Rust and C use the same LLVM backend for code generation, so Rust KCFI
is compatible with the KCFI used in the kernel for C. In the case of
FineIBT, CFI also depends on -Zpatchable-function-entry for rewriting
the function prologue, so we set that flag for Rust as well. The flag
for FineIBT requires rustc 1.80.0 or later, so include a Kconfig
requirement for that.
Enabling Rust will select CFI_ICALL_NORMALIZE_INTEGERS because the flag
is required to use Rust with CFI. Using select rather than `depends on`
avoids the case where Rust is not visible in menuconfig due to
CFI_ICALL_NORMALIZE_INTEGERS not being enabled. One disadvantage of
select is that RUST must `depends on` all of the things that
CFI_ICALL_NORMALIZE_INTEGERS depends on to avoid invalid configurations.
Alice has been using KCFI on her phone for several months, so it is
reasonably well tested on arm64.
Signed-off-by: Matthew Maurer <mmaurer@google.com>
Co-developed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Tested-by: Gatlin Newhouse <gatlin.newhouse@gmail.com>
Acked-by: Kees Cook <kees@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240801-kcfi-v2-2-c93caed3d121@google.com
[ Replaced `!FINEIBT` requirement with `!CALL_PADDING` to prevent
a build error on older Rust compilers. Fixed typo. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
Makefile | 7 +++++++
arch/x86/Makefile | 4 ++++
init/Kconfig | 4 +++-
rust/Makefile | 2 +-
scripts/generate_rust_target.rs | 1 +
5 files changed, 16 insertions(+), 2 deletions(-)
diff --git a/Makefile b/Makefile
index 35253bff5ca2c..08ba14ef128e3 100644
--- a/Makefile
+++ b/Makefile
@@ -957,6 +957,13 @@ CC_FLAGS_CFI := -fsanitize=kcfi
ifdef CONFIG_CFI_ICALL_NORMALIZE_INTEGERS
CC_FLAGS_CFI += -fsanitize-cfi-icall-experimental-normalize-integers
endif
+ifdef CONFIG_RUST
+ # Always pass -Zsanitizer-cfi-normalize-integers as CONFIG_RUST selects
+ # CONFIG_CFI_ICALL_NORMALIZE_INTEGERS.
+ RUSTC_FLAGS_CFI := -Zsanitizer=kcfi -Zsanitizer-cfi-normalize-integers
+ KBUILD_RUSTFLAGS += $(RUSTC_FLAGS_CFI)
+ export RUSTC_FLAGS_CFI
+endif
KBUILD_CFLAGS += $(CC_FLAGS_CFI)
export CC_FLAGS_CFI
endif
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index a1883a30a5d80..cd75e78a06c10 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -242,6 +242,10 @@ ifdef CONFIG_CALL_PADDING
PADDING_CFLAGS := -fpatchable-function-entry=$(CONFIG_FUNCTION_PADDING_BYTES),$(CONFIG_FUNCTION_PADDING_BYTES)
KBUILD_CFLAGS += $(PADDING_CFLAGS)
export PADDING_CFLAGS
+
+PADDING_RUSTFLAGS := -Zpatchable-function-entry=$(CONFIG_FUNCTION_PADDING_BYTES),$(CONFIG_FUNCTION_PADDING_BYTES)
+KBUILD_RUSTFLAGS += $(PADDING_RUSTFLAGS)
+export PADDING_RUSTFLAGS
endif
KBUILD_LDFLAGS += -m elf_$(UTS_MACHINE)
diff --git a/init/Kconfig b/init/Kconfig
index 9bcda3b0a20f5..53f4589b78472 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1905,11 +1905,13 @@ config RUST
bool "Rust support"
depends on HAVE_RUST
depends on RUST_IS_AVAILABLE
- depends on !CFI_CLANG
depends on !MODVERSIONS
depends on !GCC_PLUGIN_RANDSTRUCT
depends on !RANDSTRUCT
depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE
+ depends on !CFI_CLANG || RUSTC_VERSION >= 107900 && $(cc-option,-fsanitize=kcfi -fsanitize-cfi-icall-experimental-normalize-integers)
+ select CFI_ICALL_NORMALIZE_INTEGERS if CFI_CLANG
+ depends on !CALL_PADDING || RUSTC_VERSION >= 108000
help
Enables Rust support in the kernel.
diff --git a/rust/Makefile b/rust/Makefile
index 4eae318f36ff7..dd76dc27d6667 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -306,7 +306,7 @@ $(obj)/bindings/bindings_helpers_generated.rs: $(src)/helpers/helpers.c FORCE
quiet_cmd_exports = EXPORTS $@
cmd_exports = \
$(NM) -p --defined-only $< \
- | awk '/ (T|R|D) / {printf "EXPORT_SYMBOL_RUST_GPL(%s);\n",$$3}' > $@
+ | awk '$$2~/(T|R|D)/ && $$3!~/__cfi/ {printf "EXPORT_SYMBOL_RUST_GPL(%s);\n",$$3}' > $@
$(obj)/exports_core_generated.h: $(obj)/core.o FORCE
$(call if_changed,exports)
diff --git a/scripts/generate_rust_target.rs b/scripts/generate_rust_target.rs
index fbf723996d201..087c1d13d33ba 100644
--- a/scripts/generate_rust_target.rs
+++ b/scripts/generate_rust_target.rs
@@ -207,6 +207,7 @@ fn main() {
}
ts.push("features", features);
ts.push("llvm-target", "x86_64-linux-gnu");
+ ts.push("supported-sanitizers", ["kcfi"]);
ts.push("target-pointer-width", "64");
} else if cfg.has("X86_32") {
// This only works on UML, as i386 otherwise needs regparm support in rustc
--
GitLab