From: Ben Hutchings <ben@decadent.org.uk>
Date: Wed, 13 Jul 2022 22:39:33 +0000 (+0200)
Subject: x86/xen: Fix initialisation in hypercall_page after rethunk
X-Git-Tag: v5.10.133~16
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=668cb1ddf0ae7fcffcfc2ac1cfec9f770c8191fc;p=users%2Fdwmw2%2Flinux.git

x86/xen: Fix initialisation in hypercall_page after rethunk

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@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S
index 38b73e7e54ba7..2a3ef5fcba34b 100644
--- 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) \