linux-kernel - [PATCH 3/3] xen, pvh: fix unbootable VMs by inlining memset in xen_prepare

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Message-ID: <3fe4502f-020e-46de-976a-b32a76de478a@p183>
Date: Fri, 2 Aug 2024 11:53:00 +0300
From: Alexey Dobriyan <adobriyan@...il.com>
To: Juergen Gross <jgross@...e.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc: xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] xen, pvh: fix unbootable VMs by inlining memset in
 xen_prepare_pvh

If this memset() is not inlined than PVH early boot code can call
into KASAN-instrumented memset() which results in unbootable VMs.

Ubuntu's 22.04.4 LTS gcc version 11.4.0 (Ubuntu 11.4.0-1ubuntu1~22.04)
doesn't inline this memset but inlines __builtin_memset.

Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
---

 arch/x86/platform/pvh/enlighten.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/platform/pvh/enlighten.c b/arch/x86/platform/pvh/enlighten.c
index 8c2d4b8de25d..c2f6e202217c 100644
--- a/arch/x86/platform/pvh/enlighten.c
+++ b/arch/x86/platform/pvh/enlighten.c
@@ -133,7 +133,8 @@ void __init xen_prepare_pvh(void)
 		BUG();
 	}
 
-	memset(&pvh_bootparams, 0, sizeof(pvh_bootparams));
+	/* This can compile to "call memset" and memset() can be instrumented. */
+	__builtin_memset(&pvh_bootparams, 0, sizeof(pvh_bootparams));
 
 	hypervisor_specific_init(xen_guest);