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linux-next/arch/x86/include/asm/insn.h
Masami Hiramatsu 4d65adfcd1 x86: xen: insn: Decode Xen and KVM emulate-prefix signature 
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@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: x86@kernel.org
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: xen-devel@lists.xenproject.org
Cc: Randy Dunlap <rdunlap@infradead.org>
Link: https://lkml.kernel.org/r/156777564986.25081.4964537658500952557.stgit@devnote2
2019-10-17 21:31:57 +02:00

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/* SPDX-License-Identifier: GPL-2.0-or-later */
#ifndef _ASM_X86_INSN_H
#define _ASM_X86_INSN_H
/*
* x86 instruction analysis
*
* Copyright (C) IBM Corporation, 2009
*/
/* insn_attr_t is defined in inat.h */
#include <asm/inat.h>
struct insn_field {
union {
insn_value_t value;
insn_byte_t bytes[4];
};
/* !0 if we've run insn_get_xxx() for this field */
unsigned char got;
unsigned char nbytes;
};
struct insn {
struct insn_field prefixes; /*
* Prefixes
* prefixes.bytes[3]: last prefix
*/
struct insn_field rex_prefix; /* REX prefix */
struct insn_field vex_prefix; /* VEX prefix */
struct insn_field opcode; /*
* opcode.bytes[0]: opcode1
* opcode.bytes[1]: opcode2
* opcode.bytes[2]: opcode3
*/
struct insn_field modrm;
struct insn_field sib;
struct insn_field displacement;
union {
struct insn_field immediate;
struct insn_field moffset1; /* for 64bit MOV */
struct insn_field immediate1; /* for 64bit imm or off16/32 */
};
union {
struct insn_field moffset2; /* for 64bit MOV */
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;
unsigned char length;
unsigned char x86_64;
const insn_byte_t *kaddr; /* kernel address of insn to analyze */
const insn_byte_t *end_kaddr; /* kernel address of last insn in buffer */
const insn_byte_t *next_byte;
};
#define MAX_INSN_SIZE 15
#define X86_MODRM_MOD(modrm) (((modrm) & 0xc0) >> 6)
#define X86_MODRM_REG(modrm) (((modrm) & 0x38) >> 3)
#define X86_MODRM_RM(modrm) ((modrm) & 0x07)
#define X86_SIB_SCALE(sib) (((sib) & 0xc0) >> 6)
#define X86_SIB_INDEX(sib) (((sib) & 0x38) >> 3)
#define X86_SIB_BASE(sib) ((sib) & 0x07)
#define X86_REX_W(rex) ((rex) & 8)
#define X86_REX_R(rex) ((rex) & 4)
#define X86_REX_X(rex) ((rex) & 2)
#define X86_REX_B(rex) ((rex) & 1)
/* VEX bit flags */
#define X86_VEX_W(vex) ((vex) & 0x80) /* VEX3 Byte2 */
#define X86_VEX_R(vex) ((vex) & 0x80) /* VEX2/3 Byte1 */
#define X86_VEX_X(vex) ((vex) & 0x40) /* VEX3 Byte1 */
#define X86_VEX_B(vex) ((vex) & 0x20) /* VEX3 Byte1 */
#define X86_VEX_L(vex) ((vex) & 0x04) /* VEX3 Byte2, VEX2 Byte1 */
/* VEX bit fields */
#define X86_EVEX_M(vex) ((vex) & 0x03) /* EVEX Byte1 */
#define X86_VEX3_M(vex) ((vex) & 0x1f) /* VEX3 Byte1 */
#define X86_VEX2_M 1 /* VEX2.M always 1 */
#define X86_VEX_V(vex) (((vex) & 0x78) >> 3) /* VEX3 Byte2, VEX2 Byte1 */
#define X86_VEX_P(vex) ((vex) & 0x03) /* VEX3 Byte2, VEX2 Byte1 */
#define X86_VEX_M_MAX 0x1f /* VEX3.M Maximum value */
extern void insn_init(struct insn *insn, const void *kaddr, int buf_len, int x86_64);
extern void insn_get_prefixes(struct insn *insn);
extern void insn_get_opcode(struct insn *insn);
extern void insn_get_modrm(struct insn *insn);
extern void insn_get_sib(struct insn *insn);
extern void insn_get_displacement(struct insn *insn);
extern void insn_get_immediate(struct insn *insn);
extern void insn_get_length(struct insn *insn);
/* Attribute will be determined after getting ModRM (for opcode groups) */
static inline void insn_get_attribute(struct insn *insn)
{
insn_get_modrm(insn);
}
/* Instruction uses RIP-relative addressing */
extern int insn_rip_relative(struct insn *insn);
/* Init insn for kernel text */
static inline void kernel_insn_init(struct insn *insn,
const void *kaddr, int buf_len)
{
#ifdef CONFIG_X86_64
insn_init(insn, kaddr, buf_len, 1);
#else /* CONFIG_X86_32 */
insn_init(insn, kaddr, buf_len, 0);
#endif
}
static inline int insn_is_avx(struct insn *insn)
{
if (!insn->prefixes.got)
insn_get_prefixes(insn);
return (insn->vex_prefix.value != 0);
}
static inline int insn_is_evex(struct insn *insn)
{
if (!insn->prefixes.got)
insn_get_prefixes(insn);
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)
{
return insn->opcode.got && insn->modrm.got && insn->sib.got &&
insn->displacement.got && insn->immediate.got;
}
static inline insn_byte_t insn_vex_m_bits(struct insn *insn)
{
if (insn->vex_prefix.nbytes == 2) /* 2 bytes VEX */
return X86_VEX2_M;
else if (insn->vex_prefix.nbytes == 3) /* 3 bytes VEX */
return X86_VEX3_M(insn->vex_prefix.bytes[1]);
else /* EVEX */
return X86_EVEX_M(insn->vex_prefix.bytes[1]);
}
static inline insn_byte_t insn_vex_p_bits(struct insn *insn)
{
if (insn->vex_prefix.nbytes == 2) /* 2 bytes VEX */
return X86_VEX_P(insn->vex_prefix.bytes[1]);
else
return X86_VEX_P(insn->vex_prefix.bytes[2]);
}
/* Get the last prefix id from last prefix or VEX prefix */
static inline int insn_last_prefix_id(struct insn *insn)
{
if (insn_is_avx(insn))
return insn_vex_p_bits(insn); /* VEX_p is a SIMD prefix id */
if (insn->prefixes.bytes[3])
return inat_get_last_prefix_id(insn->prefixes.bytes[3]);
return 0;
}
/* Offset of each field from kaddr */
static inline int insn_offset_rex_prefix(struct insn *insn)
{
return insn->prefixes.nbytes;
}
static inline int insn_offset_vex_prefix(struct insn *insn)
{
return insn_offset_rex_prefix(insn) + insn->rex_prefix.nbytes;
}
static inline int insn_offset_opcode(struct insn *insn)
{
return insn_offset_vex_prefix(insn) + insn->vex_prefix.nbytes;
}
static inline int insn_offset_modrm(struct insn *insn)
{
return insn_offset_opcode(insn) + insn->opcode.nbytes;
}
static inline int insn_offset_sib(struct insn *insn)
{
return insn_offset_modrm(insn) + insn->modrm.nbytes;
}
static inline int insn_offset_displacement(struct insn *insn)
{
return insn_offset_sib(insn) + insn->sib.nbytes;
}
static inline int insn_offset_immediate(struct insn *insn)
{
return insn_offset_displacement(insn) + insn->displacement.nbytes;
}
#define POP_SS_OPCODE 0x1f
#define MOV_SREG_OPCODE 0x8e
/*
* Intel SDM Vol.3A 6.8.3 states;
* "Any single-step trap that would be delivered following the MOV to SS
* instruction or POP to SS instruction (because EFLAGS.TF is 1) is
* suppressed."
* This function returns true if @insn is MOV SS or POP SS. On these
* instructions, single stepping is suppressed.
*/
static inline int insn_masking_exception(struct insn *insn)
{
return insn->opcode.bytes[0] == POP_SS_OPCODE ||
(insn->opcode.bytes[0] == MOV_SREG_OPCODE &&
X86_MODRM_REG(insn->modrm.bytes[0]) == 2);
}
#endif /* _ASM_X86_INSN_H */
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