Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | Date | Fri, 15 Dec 2023 19:39:57 +0000 | Subject | [PATCH] x86: rust: Disable entry padding with Rust | From | Matthew Maurer <> |
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rustc-1.73.0 used by Linux does not support entry padding. Mark entry padding support as explicitly incompatible with Rust.
Signed-off-by: Matthew Maurer <mmaurer@google.com> ---
This is temporary - upstream in the Rust compiler, I have:
* A MCP[1] to enable the feature as an unstable flag * A RFC[2] to stabilize it and add the attribute * An initial implementation[3] for the MCP and RFC once accepted
Once at least unstable support is merged, we can detect this in a future patch.
Even once those are merged and Linux is using a newer rustc, we will still want a separate HAVE_ENTRY_PADDING config, as Rust's gcc backend will not initially support it.
While this is a temporary patch, I still think it's worth carrying because it prevents us from selecting build configurations that will fail at runtime.
[1]: https://github.com/rust-lang/compiler-team/issues/704 [2]: https://github.com/rust-lang/rfcs/pull/3543 [3]: https://github.com/maurer/rust/tree/patchable-function-entries arch/x86/Kconfig | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 18b9fb7df95b..a9d48709f7db 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2452,6 +2452,9 @@ config CC_HAS_RETURN_THUNK config CC_HAS_ENTRY_PADDING def_bool $(cc-option,-fpatchable-function-entry=16,16) +config HAVE_ENTRY_PADDING + def_bool CC_HAS_ENTRY_PADDING && !RUST + config FUNCTION_PADDING_CFI int default 59 if FUNCTION_ALIGNMENT_64B @@ -2469,17 +2472,17 @@ config FUNCTION_PADDING_BYTES config CALL_PADDING def_bool n - depends on CC_HAS_ENTRY_PADDING && OBJTOOL + depends on HAVE_ENTRY_PADDING && OBJTOOL select FUNCTION_ALIGNMENT_16B config FINEIBT def_bool y - depends on X86_KERNEL_IBT && CFI_CLANG && RETPOLINE + depends on X86_KERNEL_IBT && CFI_CLANG && RETPOLINE && HAVE_ENTRY_PADDING select CALL_PADDING config HAVE_CALL_THUNKS def_bool y - depends on CC_HAS_ENTRY_PADDING && RETHUNK && OBJTOOL + depends on HAVE_ENTRY_PADDING && RETHUNK && OBJTOOL config CALL_THUNKS def_bool n -- 2.43.0.472.g3155946c3a-goog
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