linux-kernel - [PATCH 5.15 79/89] x86/xen: Fix initialisation in hypercall

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Message-Id: <20220722091137.764504078@linuxfoundation.org>
Date:   Fri, 22 Jul 2022 11:11:53 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ben Hutchings <ben@...adent.org.uk>
Subject: [PATCH 5.15 79/89] x86/xen: Fix initialisation in hypercall_page after rethunk

From: Ben Hutchings <ben@...adent.org.uk>

The hypercall_page is special and the RETs there should not be changed
into rethunk calls (but can have SLS mitigation).  Change the initial
instructions to ret + int3 padding, as was done in upstream commit
5b2fc51576ef "x86/ibt,xen: Sprinkle the ENDBR".

Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/x86/xen/xen-head.S |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/x86/xen/xen-head.S
+++ b/arch/x86/xen/xen-head.S
@@ -69,9 +69,9 @@ SYM_CODE_END(asm_cpu_bringup_and_idle)
 SYM_CODE_START(hypercall_page)
 	.rept (PAGE_SIZE / 32)
 		UNWIND_HINT_FUNC
-		.skip 31, 0x90
 		ANNOTATE_UNRET_SAFE
-		RET
+		ret
+		.skip 31, 0xcc
 	.endr
 
 #define HYPERCALL(n) \