[PATCH] x86/Kconfig: rust: Patchable function Rust compat

[Matthew Maurer]

Rust doesn't yet support patchable entry, but likely will soon. Disable
function padding when Rust is used but doesn't support it, and propagate
the flag when it does.

Signed-off-by: Matthew Maurer <mmaurer@xxxxxxxxxx>
---
 arch/x86/Kconfig  | 6 +++++-
 arch/x86/Makefile | 2 ++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 18b9fb7df95b..e9f1814217b5 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2452,6 +2452,10 @@ config CC_HAS_RETURN_THUNK
 config CC_HAS_ENTRY_PADDING
 	def_bool $(cc-option,-fpatchable-function-entry=16,16)
 
+config RUSTC_HAS_ENTRY_PADDING
+	depends RUST
+	def_bool $(rs-option,-Zpatchable-function-entry=16,16)
+
 config FUNCTION_PADDING_CFI
 	int
 	default 59 if FUNCTION_ALIGNMENT_64B
@@ -2469,7 +2473,7 @@ config FUNCTION_PADDING_BYTES
 
 config CALL_PADDING
 	def_bool n
-	depends on CC_HAS_ENTRY_PADDING && OBJTOOL
+	depends on CC_HAS_ENTRY_PADDING && (!RUST || RUST_HAS_ENTRY_PADDING) && OBJTOOL
 	select FUNCTION_ALIGNMENT_16B
 
 config FINEIBT
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 1a068de12a56..0228af62742e 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -211,7 +211,9 @@ endif
 
 ifdef CONFIG_CALL_PADDING
 PADDING_CFLAGS := -fpatchable-function-entry=$(CONFIG_FUNCTION_PADDING_BYTES),$(CONFIG_FUNCTION_PADDING_BYTES)
+PADDING_RUSTFLAGS := -Zpatchable-function-entry=$(CONFIG_FUNCTION_PADDING_BYTES),$(CONFIG_FUNCTION_PADDING_BYTES)
 KBUILD_CFLAGS += $(PADDING_CFLAGS)
+KBUILD_RUSTFLAGS += $(PADDING_RUSTFLAGS)
 export PADDING_CFLAGS
 endif
 
-- 
2.43.0.472.g3155946c3a-goog