cfi: fix conditions for HAVE_CFI_ICALL_NORMALIZE_INTEGERS

The HAVE_CFI_ICALL_NORMALIZE_INTEGERS option has some tricky conditions
when KASAN or GCOV are turned on, as in that case we need some clang and
rustc fixes [1][2] to avoid boot failures. The intent with the current
setup is that you should be able to override the check and turn on the
option if your clang/rustc has the fix. However, this override does not
work in practice. Thus, use the new RUSTC_LLVM_VERSION to correctly
implement the check for whether the fix is available.

Additionally, remove KASAN_HW_TAGS from the list of incompatible
options. The CFI_ICALL_NORMALIZE_INTEGERS option is incompatible with
KASAN because LLVM will emit some constructors when using KASAN that are
assigned incorrect CFI tags. These constructors are emitted due to use
of -fsanitize=kernel-address or -fsanitize=kernel-hwaddress that are
respectively passed when KASAN_GENERIC or KASAN_SW_TAGS are enabled.
However, the KASAN_HW_TAGS option relies on hardware support for MTE
instead and does not pass either flag. (Note also that KASAN_HW_TAGS
does not `select CONSTRUCTORS`.)

Link: https://github.com/llvm/llvm-project/pull/104826
Link: https://github.com/rust-lang/rust/pull/129373
Fixes: 4c66f8307ac0 ("cfi: encode cfi normalized integers + kasan/gcov bug in Kconfig")
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Link: https://lore.kernel.org/r/20241010-icall-detect-vers-v1-2-8f114956aa88@google.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

diff --git a/arch/Kconfig b/arch/Kconfig
index 8af374ea1adc245b3aa341314a1dcb51865d03d1..00163e4a237c1b56d0bc27f4bc147f19620e4907 100644 (file)
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -838,7 +838,7 @@ config CFI_CLANG
 config CFI_ICALL_NORMALIZE_INTEGERS
        bool "Normalize CFI tags for integers"
        depends on CFI_CLANG
-       depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS
+       depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG
        help
          This option normalizes the CFI tags for integer types so that all
          integer types of the same size and signedness receive the same CFI
@@ -851,21 +851,19 @@ config CFI_ICALL_NORMALIZE_INTEGERS
 
          This option is necessary for using CFI with Rust. If unsure, say N.
 
-config HAVE_CFI_ICALL_NORMALIZE_INTEGERS
-       def_bool !GCOV_KERNEL && !KASAN
-       depends on CFI_CLANG
+config HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG
+       def_bool y
        depends on $(cc-option,-fsanitize=kcfi -fsanitize-cfi-icall-experimental-normalize-integers)
-       help
-         Is CFI_ICALL_NORMALIZE_INTEGERS supported with the set of compilers
-         currently in use?
+       # With GCOV/KASAN we need this fix: https://github.com/llvm/llvm-project/pull/104826
+       depends on CLANG_VERSION >= 190000 || (!GCOV_KERNEL && !KASAN_GENERIC && !KASAN_SW_TAGS)
 
-         This option defaults to false if GCOV or KASAN is enabled, as there is
-         an LLVM bug that makes normalized integers tags incompatible with
-         KASAN and GCOV. Kconfig currently does not have the infrastructure to
-         detect whether your rustc compiler contains the fix for this bug, so
-         it is assumed that it doesn't. If your compiler has the fix, you can
-         explicitly enable this option in your config file. The Kconfig logic
-         needed to detect this will be added in a future kernel release.
+config HAVE_CFI_ICALL_NORMALIZE_INTEGERS_RUSTC
+       def_bool y
+       depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG
+       depends on RUSTC_VERSION >= 107900
+       # With GCOV/KASAN we need this fix: https://github.com/rust-lang/rust/pull/129373
+       depends on (RUSTC_LLVM_VERSION >= 190000 && RUSTC_VERSION >= 108200) || \
+               (!GCOV_KERNEL && !KASAN_GENERIC && !KASAN_SW_TAGS)
 
 config CFI_PERMISSIVE
        bool "Use CFI in permissive mode"

diff --git a/init/Kconfig b/init/Kconfig
index 98cf859d58c2dd3e8bbb45b7365943c0ea9b6daf..c521e1421ad4abd80080bce8cf1c68389cb65c69 100644 (file)
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1950,7 +1950,7 @@ config RUST
        depends on !GCC_PLUGIN_RANDSTRUCT
        depends on !RANDSTRUCT
        depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE
-       depends on !CFI_CLANG || RUSTC_VERSION >= 107900 && HAVE_CFI_ICALL_NORMALIZE_INTEGERS
+       depends on !CFI_CLANG || HAVE_CFI_ICALL_NORMALIZE_INTEGERS_RUSTC
        select CFI_ICALL_NORMALIZE_INTEGERS if CFI_CLANG
        depends on !CALL_PADDING || RUSTC_VERSION >= 108100
        depends on !KASAN_SW_TAGS