linux-kernel - [PATCH 5.4 11/18] x86: xen: kvm: Gather the definition of emulate prefixes

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20220513142229.483992618@linuxfoundation.org>
Date:   Fri, 13 May 2022 16:23:37 +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, Peter Zijlstra <peterz@...radead.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Juergen Gross <jgross@...e.com>, x86@...nel.org,
        Ingo Molnar <mingo@...nel.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Andrew Cooper <andrew.cooper3@...rix.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Borislav Petkov <bp@...en8.de>, xen-devel@...ts.xenproject.org,
        Randy Dunlap <rdunlap@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Maximilian Heyne <mheyne@...zon.de>
Subject: [PATCH 5.4 11/18] x86: xen: kvm: Gather the definition of emulate prefixes

From: Masami Hiramatsu <mhiramat@...nel.org>

commit b3dc0695fa40c3b280230fb6fb7fb7a94ce28bf4 upstream.

Gather the emulate prefixes, which forcibly make the following
instruction emulated on virtualization, in one place.

Suggested-by: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Juergen Gross <jgross@...e.com>
Cc: x86@...nel.org
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc: Andrew Cooper <andrew.cooper3@...rix.com>
Cc: Stefano Stabellini <sstabellini@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: xen-devel@...ts.xenproject.org
Cc: Randy Dunlap <rdunlap@...radead.org>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Link: https://lkml.kernel.org/r/156777563917.25081.7286628561790289995.stgit@devnote2
Signed-off-by: Maximilian Heyne <mheyne@...zon.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/x86/include/asm/emulate_prefix.h |   14 ++++++++++++++
 arch/x86/include/asm/xen/interface.h  |   11 ++++-------
 arch/x86/kvm/x86.c                    |    4 +++-
 3 files changed, 21 insertions(+), 8 deletions(-)
 create mode 100644 arch/x86/include/asm/emulate_prefix.h

--- /dev/null
+++ b/arch/x86/include/asm/emulate_prefix.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_EMULATE_PREFIX_H
+#define _ASM_X86_EMULATE_PREFIX_H
+
+/*
+ * Virt escape sequences to trigger instruction emulation;
+ * ideally these would decode to 'whole' instruction and not destroy
+ * the instruction stream; sadly this is not true for the 'kvm' one :/
+ */
+
+#define __XEN_EMULATE_PREFIX  0x0f,0x0b,0x78,0x65,0x6e  /* ud2 ; .ascii "xen" */
+#define __KVM_EMULATE_PREFIX  0x0f,0x0b,0x6b,0x76,0x6d	/* ud2 ; .ascii "kvm" */
+
+#endif
--- a/arch/x86/include/asm/xen/interface.h
+++ b/arch/x86/include/asm/xen/interface.h
@@ -379,12 +379,9 @@ struct xen_pmu_arch {
  * Prefix forces emulation of some non-trapping instructions.
  * Currently only CPUID.
  */
-#ifdef __ASSEMBLY__
-#define XEN_EMULATE_PREFIX .byte 0x0f,0x0b,0x78,0x65,0x6e ;
-#define XEN_CPUID          XEN_EMULATE_PREFIX cpuid
-#else
-#define XEN_EMULATE_PREFIX ".byte 0x0f,0x0b,0x78,0x65,0x6e ; "
-#define XEN_CPUID          XEN_EMULATE_PREFIX "cpuid"
-#endif
+#include <asm/emulate_prefix.h>
+
+#define XEN_EMULATE_PREFIX __ASM_FORM(.byte __XEN_EMULATE_PREFIX ;)
+#define XEN_CPUID          XEN_EMULATE_PREFIX __ASM_FORM(cpuid)
 
 #endif /* _ASM_X86_XEN_INTERFACE_H */
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -68,6 +68,7 @@
 #include <asm/mshyperv.h>
 #include <asm/hypervisor.h>
 #include <asm/intel_pt.h>
+#include <asm/emulate_prefix.h>
 #include <clocksource/hyperv_timer.h>
 
 #define CREATE_TRACE_POINTS
@@ -5583,6 +5584,7 @@ EXPORT_SYMBOL_GPL(kvm_write_guest_virt_s
 
 int handle_ud(struct kvm_vcpu *vcpu)
 {
+	static const char kvm_emulate_prefix[] = { __KVM_EMULATE_PREFIX };
 	int emul_type = EMULTYPE_TRAP_UD;
 	char sig[5]; /* ud2; .ascii "kvm" */
 	struct x86_exception e;
@@ -5590,7 +5592,7 @@ int handle_ud(struct kvm_vcpu *vcpu)
 	if (force_emulation_prefix &&
 	    kvm_read_guest_virt(vcpu, kvm_get_linear_rip(vcpu),
 				sig, sizeof(sig), &e) == 0 &&
-	    memcmp(sig, "\xf\xbkvm", sizeof(sig)) == 0) {
+	    memcmp(sig, kvm_emulate_prefix, sizeof(sig)) == 0) {
 		kvm_rip_write(vcpu, kvm_rip_read(vcpu) + sizeof(sig));
 		emul_type = EMULTYPE_TRAP_UD_FORCED;
 	}