rust: SHADOW_CALL_STACK is incompatible with Rust

When using the shadow call stack sanitizer, all code must be compiled
with the -ffixed-x18 flag, but this flag is not currently being passed
to Rust. This results in crashes that are extremely difficult to debug.

To ensure that nobody else has to go through the same debugging session
that I had to, prevent configurations that enable both SHADOW_CALL_STACK
and RUST.

It is rather common for people to backport 724a75ac9542 ("arm64: rust:
Enable Rust support for AArch64"), so I recommend applying this fix all
the way back to 6.1.

Cc: stable@vger.kernel.org # 6.1 and later
Fixes: 724a75ac9542 ("arm64: rust: Enable Rust support for AArch64")
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://lore.kernel.org/r/20240729-shadow-call-stack-v4-1-2a664b082ea4@google.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/init/Kconfig b/init/Kconfig
index a465ea9525bd590c2b60dd4a4a08c90015bf17f5..37260d17267e43fcda364b4075cfc70dad3095fb 100644 (file)
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1902,6 +1902,7 @@ config RUST
        depends on !MODVERSIONS
        depends on !GCC_PLUGINS
        depends on !RANDSTRUCT
+       depends on !SHADOW_CALL_STACK
        depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE
        help
          Enables Rust support in the kernel.