linux-kernel - [tip: x86/core] x86/Kconfig: Add CONFIG_CALL

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Message-ID: <166601843147.401.3646706448544046869.tip-bot2@tip-bot2>
Date:   Mon, 17 Oct 2022 14:53:51 -0000
From:   "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: x86/core] x86/Kconfig: Add CONFIG_CALL_THUNKS

The following commit has been merged into the x86/core branch of tip:

Commit-ID:     8f7c0d8b23c3f5f740a48db31ebadef28af17a22
Gitweb:        https://git.kernel.org/tip/8f7c0d8b23c3f5f740a48db31ebadef28af17a22
Author:        Thomas Gleixner <tglx@...utronix.de>
AuthorDate:    Thu, 15 Sep 2022 13:11:17 +02:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Mon, 17 Oct 2022 16:41:10 +02:00

x86/Kconfig: Add CONFIG_CALL_THUNKS

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@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lore.kernel.org/r/20220915111146.849523555@infradead.org
---
 arch/x86/Kconfig | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index f408fa8..e18963e 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2446,6 +2446,14 @@ 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