[PATCH v3 38/59] x86/Kconfig: Add CONFIG_CALL_THUNKS

Peter Zijlstra
2022-09-15T11:42:20Z

From: Thomas Gleixner <tglx@linutronix.de>

In preparation for mitigating the Intel SKL RSB underflow issue in
software, add a new configuration symbol which allows to build the
required call thunk infrastructure conditionally.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/Kconfig | 8 ++++++++
1 file changed, 8 insertions(+)

--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2429,6 +2429,14 @@ config CC_HAS_SLS
config CC_HAS_RETURN_THUNK
def_bool $(cc-option,-mfunction-return=thunk-extern)

+config HAVE_CALL_THUNKS
+ def_bool y
+ depends on RETHUNK && OBJTOOL
+
+config CALL_THUNKS
+ def_bool n
+ select FUNCTION_ALIGNMENT_16B
+
menuconfig SPECULATION_MITIGATIONS
bool "Mitigations for speculative execution vulnerabilities"
default y