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Message-Id: <20220513142229.512910493@linuxfoundation.org>
Date: Fri, 13 May 2022 16:23:38 +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, Masami Hiramatsu <mhiramat@...nel.org>,
"Peter Zijlstra (Intel)" <peterz@...radead.org>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Juergen Gross <jgross@...e.com>, x86@...nel.org,
Boris Ostrovsky <boris.ostrovsky@...cle.com>,
Ingo Molnar <mingo@...nel.org>,
Stefano Stabellini <sstabellini@...nel.org>,
Andrew Cooper <andrew.cooper3@...rix.com>,
Borislav Petkov <bp@...en8.de>, xen-devel@...ts.xenproject.org,
Randy Dunlap <rdunlap@...radead.org>,
Maximilian Heyne <mheyne@...zon.de>
Subject: [PATCH 5.4 12/18] x86: xen: insn: Decode Xen and KVM emulate-prefix signature
From: Masami Hiramatsu <mhiramat@...nel.org>
commit 4d65adfcd1196818659d3bd9b42dccab291e1751 upstream.
Decode Xen and KVM's emulate-prefix signature by x86 insn decoder.
It is called "prefix" but actually not x86 instruction prefix, so
this adds insn.emulate_prefix_size field instead of reusing
insn.prefixes.
If x86 decoder finds a special sequence of instructions of
XEN_EMULATE_PREFIX and 'ud2a; .ascii "kvm"', it just counts the
length, set insn.emulate_prefix_size and fold it with the next
instruction. In other words, the signature and the next instruction
is treated as a single instruction.
Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Juergen Gross <jgross@...e.com>
Cc: x86@...nel.org
Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Stefano Stabellini <sstabellini@...nel.org>
Cc: Andrew Cooper <andrew.cooper3@...rix.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: xen-devel@...ts.xenproject.org
Cc: Randy Dunlap <rdunlap@...radead.org>
Link: https://lkml.kernel.org/r/156777564986.25081.4964537658500952557.stgit@devnote2
[mheyne: resolved contextual conflict in tools/objtools/sync-check.sh]
Signed-off-by: Maximilian Heyne <mheyne@...zon.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
arch/x86/include/asm/insn.h | 6 ++++
arch/x86/lib/insn.c | 34 ++++++++++++++++++++++++++++
tools/arch/x86/include/asm/emulate_prefix.h | 14 +++++++++++
tools/arch/x86/include/asm/insn.h | 6 ++++
tools/arch/x86/lib/insn.c | 34 ++++++++++++++++++++++++++++
tools/objtool/sync-check.sh | 3 +-
tools/perf/check-headers.sh | 3 +-
7 files changed, 98 insertions(+), 2 deletions(-)
create mode 100644 tools/arch/x86/include/asm/emulate_prefix.h
--- a/arch/x86/include/asm/insn.h
+++ b/arch/x86/include/asm/insn.h
@@ -45,6 +45,7 @@ struct insn {
struct insn_field immediate2; /* for 64bit imm or seg16 */
};
+ int emulate_prefix_size;
insn_attr_t attr;
unsigned char opnd_bytes;
unsigned char addr_bytes;
@@ -128,6 +129,11 @@ static inline int insn_is_evex(struct in
return (insn->vex_prefix.nbytes == 4);
}
+static inline int insn_has_emulate_prefix(struct insn *insn)
+{
+ return !!insn->emulate_prefix_size;
+}
+
/* Ensure this instruction is decoded completely */
static inline int insn_complete(struct insn *insn)
{
--- a/arch/x86/lib/insn.c
+++ b/arch/x86/lib/insn.c
@@ -13,6 +13,8 @@
#include <asm/inat.h>
#include <asm/insn.h>
+#include <asm/emulate_prefix.h>
+
/* Verify next sizeof(t) bytes can be on the same instruction */
#define validate_next(t, insn, n) \
((insn)->next_byte + sizeof(t) + n <= (insn)->end_kaddr)
@@ -58,6 +60,36 @@ void insn_init(struct insn *insn, const
insn->addr_bytes = 4;
}
+static const insn_byte_t xen_prefix[] = { __XEN_EMULATE_PREFIX };
+static const insn_byte_t kvm_prefix[] = { __KVM_EMULATE_PREFIX };
+
+static int __insn_get_emulate_prefix(struct insn *insn,
+ const insn_byte_t *prefix, size_t len)
+{
+ size_t i;
+
+ for (i = 0; i < len; i++) {
+ if (peek_nbyte_next(insn_byte_t, insn, i) != prefix[i])
+ goto err_out;
+ }
+
+ insn->emulate_prefix_size = len;
+ insn->next_byte += len;
+
+ return 1;
+
+err_out:
+ return 0;
+}
+
+static void insn_get_emulate_prefix(struct insn *insn)
+{
+ if (__insn_get_emulate_prefix(insn, xen_prefix, sizeof(xen_prefix)))
+ return;
+
+ __insn_get_emulate_prefix(insn, kvm_prefix, sizeof(kvm_prefix));
+}
+
/**
* insn_get_prefixes - scan x86 instruction prefix bytes
* @insn: &struct insn containing instruction
@@ -76,6 +108,8 @@ void insn_get_prefixes(struct insn *insn
if (prefixes->got)
return;
+ insn_get_emulate_prefix(insn);
+
nb = 0;
lb = 0;
b = peek_next(insn_byte_t, insn);
--- /dev/null
+++ b/tools/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/tools/arch/x86/include/asm/insn.h
+++ b/tools/arch/x86/include/asm/insn.h
@@ -45,6 +45,7 @@ struct insn {
struct insn_field immediate2; /* for 64bit imm or seg16 */
};
+ int emulate_prefix_size;
insn_attr_t attr;
unsigned char opnd_bytes;
unsigned char addr_bytes;
@@ -128,6 +129,11 @@ static inline int insn_is_evex(struct in
return (insn->vex_prefix.nbytes == 4);
}
+static inline int insn_has_emulate_prefix(struct insn *insn)
+{
+ return !!insn->emulate_prefix_size;
+}
+
/* Ensure this instruction is decoded completely */
static inline int insn_complete(struct insn *insn)
{
--- a/tools/arch/x86/lib/insn.c
+++ b/tools/arch/x86/lib/insn.c
@@ -13,6 +13,8 @@
#include "../include/asm/inat.h"
#include "../include/asm/insn.h"
+#include "../include/asm/emulate_prefix.h"
+
/* Verify next sizeof(t) bytes can be on the same instruction */
#define validate_next(t, insn, n) \
((insn)->next_byte + sizeof(t) + n <= (insn)->end_kaddr)
@@ -58,6 +60,36 @@ void insn_init(struct insn *insn, const
insn->addr_bytes = 4;
}
+static const insn_byte_t xen_prefix[] = { __XEN_EMULATE_PREFIX };
+static const insn_byte_t kvm_prefix[] = { __KVM_EMULATE_PREFIX };
+
+static int __insn_get_emulate_prefix(struct insn *insn,
+ const insn_byte_t *prefix, size_t len)
+{
+ size_t i;
+
+ for (i = 0; i < len; i++) {
+ if (peek_nbyte_next(insn_byte_t, insn, i) != prefix[i])
+ goto err_out;
+ }
+
+ insn->emulate_prefix_size = len;
+ insn->next_byte += len;
+
+ return 1;
+
+err_out:
+ return 0;
+}
+
+static void insn_get_emulate_prefix(struct insn *insn)
+{
+ if (__insn_get_emulate_prefix(insn, xen_prefix, sizeof(xen_prefix)))
+ return;
+
+ __insn_get_emulate_prefix(insn, kvm_prefix, sizeof(kvm_prefix));
+}
+
/**
* insn_get_prefixes - scan x86 instruction prefix bytes
* @insn: &struct insn containing instruction
@@ -76,6 +108,8 @@ void insn_get_prefixes(struct insn *insn
if (prefixes->got)
return;
+ insn_get_emulate_prefix(insn);
+
nb = 0;
lb = 0;
b = peek_next(insn_byte_t, insn);
--- a/tools/objtool/sync-check.sh
+++ b/tools/objtool/sync-check.sh
@@ -4,6 +4,7 @@
FILES='
arch/x86/include/asm/inat_types.h
arch/x86/include/asm/orc_types.h
+arch/x86/include/asm/emulate_prefix.h
arch/x86/lib/x86-opcode-map.txt
arch/x86/tools/gen-insn-attr-x86.awk
'
@@ -46,4 +47,4 @@ done
check arch/x86/include/asm/inat.h '-I "^#include [\"<]\(asm/\)*inat_types.h[\">]"'
check arch/x86/include/asm/insn.h '-I "^#include [\"<]\(asm/\)*inat.h[\">]"'
check arch/x86/lib/inat.c '-I "^#include [\"<]\(../include/\)*asm/insn.h[\">]"'
-check arch/x86/lib/insn.c '-I "^#include [\"<]\(../include/\)*asm/in\(at\|sn\).h[\">]"'
+check arch/x86/lib/insn.c '-I "^#include [\"<]\(../include/\)*asm/in\(at\|sn\).h[\">]" -I "^#include [\"<]\(../include/\)*asm/emulate_prefix.h[\">]"'
--- a/tools/perf/check-headers.sh
+++ b/tools/perf/check-headers.sh
@@ -28,6 +28,7 @@ arch/x86/include/asm/disabled-features.h
arch/x86/include/asm/required-features.h
arch/x86/include/asm/cpufeatures.h
arch/x86/include/asm/inat_types.h
+arch/x86/include/asm/emulate_prefix.h
arch/x86/include/uapi/asm/prctl.h
arch/x86/lib/x86-opcode-map.txt
arch/x86/tools/gen-insn-attr-x86.awk
@@ -116,7 +117,7 @@ check lib/ctype.c '-I "^EXPORT_SY
check arch/x86/include/asm/inat.h '-I "^#include [\"<]\(asm/\)*inat_types.h[\">]"'
check arch/x86/include/asm/insn.h '-I "^#include [\"<]\(asm/\)*inat.h[\">]"'
check arch/x86/lib/inat.c '-I "^#include [\"<]\(../include/\)*asm/insn.h[\">]"'
-check arch/x86/lib/insn.c '-I "^#include [\"<]\(../include/\)*asm/in\(at\|sn\).h[\">]"'
+check arch/x86/lib/insn.c '-I "^#include [\"<]\(../include/\)*asm/in\(at\|sn\).h[\">]" -I "^#include [\"<]\(../include/\)*asm/emulate_prefix.h[\">]"'
# diff non-symmetric files
check_2 tools/perf/arch/x86/entry/syscalls/syscall_64.tbl arch/x86/entry/syscalls/syscall_64.tbl
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