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1/******************************************************************************
2 * x86_emulate.h
3 *
4 * Generic x86 (32-bit and 64-bit) instruction decoder and emulator.
5 *
6 * Copyright (c) 2005 Keir Fraser
7 *
8 * From: xen-unstable 10676:af9809f51f81a3c43f276f00c81a52ef558afda4
9 */
10
11#ifndef __X86_EMULATE_H__
12#define __X86_EMULATE_H__
13
14struct x86_emulate_ctxt;
15
16/*
17 * x86_emulate_ops:
18 *
19 * These operations represent the instruction emulator's interface to memory.
20 * There are two categories of operation: those that act on ordinary memory
21 * regions (*_std), and those that act on memory regions known to require
22 * special treatment or emulation (*_emulated).
23 *
24 * The emulator assumes that an instruction accesses only one 'emulated memory'
25 * location, that this location is the given linear faulting address (cr2), and
26 * that this is one of the instruction's data operands. Instruction fetches and
27 * stack operations are assumed never to access emulated memory. The emulator
28 * automatically deduces which operand of a string-move operation is accessing
29 * emulated memory, and assumes that the other operand accesses normal memory.
30 *
31 * NOTES:
32 * 1. The emulator isn't very smart about emulated vs. standard memory.
33 * 'Emulated memory' access addresses should be checked for sanity.
34 * 'Normal memory' accesses may fault, and the caller must arrange to
35 * detect and handle reentrancy into the emulator via recursive faults.
36 * Accesses may be unaligned and may cross page boundaries.
37 * 2. If the access fails (cannot emulate, or a standard access faults) then
38 * it is up to the memop to propagate the fault to the guest VM via
39 * some out-of-band mechanism, unknown to the emulator. The memop signals
40 * failure by returning X86EMUL_PROPAGATE_FAULT to the emulator, which will
41 * then immediately bail.
42 * 3. Valid access sizes are 1, 2, 4 and 8 bytes. On x86/32 systems only
43 * cmpxchg8b_emulated need support 8-byte accesses.
44 * 4. The emulator cannot handle 64-bit mode emulation on an x86/32 system.
45 */
46/* Access completed successfully: continue emulation as normal. */
47#define X86EMUL_CONTINUE 0
48/* Access is unhandleable: bail from emulation and return error to caller. */
49#define X86EMUL_UNHANDLEABLE 1
50/* Terminate emulation but return success to the caller. */
51#define X86EMUL_PROPAGATE_FAULT 2 /* propagate a generated fault to guest */
52#define X86EMUL_RETRY_INSTR 2 /* retry the instruction for some reason */
53#define X86EMUL_CMPXCHG_FAILED 2 /* cmpxchg did not see expected value */
54struct x86_emulate_ops {
55 /*
56 * read_std: Read bytes of standard (non-emulated/special) memory.
57 * Used for instruction fetch, stack operations, and others.
58 * @addr: [IN ] Linear address from which to read.
59 * @val: [OUT] Value read from memory, zero-extended to 'u_long'.
60 * @bytes: [IN ] Number of bytes to read from memory.
61 */
62 int (*read_std)(unsigned long addr,
63 unsigned long *val,
64 unsigned int bytes, struct x86_emulate_ctxt * ctxt);
65
66 /*
67 * write_std: Write bytes of standard (non-emulated/special) memory.
68 * Used for stack operations, and others.
69 * @addr: [IN ] Linear address to which to write.
70 * @val: [IN ] Value to write to memory (low-order bytes used as
71 * required).
72 * @bytes: [IN ] Number of bytes to write to memory.
73 */
74 int (*write_std)(unsigned long addr,
75 unsigned long val,
76 unsigned int bytes, struct x86_emulate_ctxt * ctxt);
77
78 /*
79 * read_emulated: Read bytes from emulated/special memory area.
80 * @addr: [IN ] Linear address from which to read.
81 * @val: [OUT] Value read from memory, zero-extended to 'u_long'.
82 * @bytes: [IN ] Number of bytes to read from memory.
83 */
84 int (*read_emulated) (unsigned long addr,
85 unsigned long *val,
86 unsigned int bytes,
87 struct x86_emulate_ctxt * ctxt);
88
89 /*
90 * write_emulated: Read bytes from emulated/special memory area.
91 * @addr: [IN ] Linear address to which to write.
92 * @val: [IN ] Value to write to memory (low-order bytes used as
93 * required).
94 * @bytes: [IN ] Number of bytes to write to memory.
95 */
96 int (*write_emulated) (unsigned long addr,
97 unsigned long val,
98 unsigned int bytes,
99 struct x86_emulate_ctxt * ctxt);
100
101 /*
102 * cmpxchg_emulated: Emulate an atomic (LOCKed) CMPXCHG operation on an
103 * emulated/special memory area.
104 * @addr: [IN ] Linear address to access.
105 * @old: [IN ] Value expected to be current at @addr.
106 * @new: [IN ] Value to write to @addr.
107 * @bytes: [IN ] Number of bytes to access using CMPXCHG.
108 */
109 int (*cmpxchg_emulated) (unsigned long addr,
110 unsigned long old,
111 unsigned long new,
112 unsigned int bytes,
113 struct x86_emulate_ctxt * ctxt);
114
115 /*
116 * cmpxchg8b_emulated: Emulate an atomic (LOCKed) CMPXCHG8B operation on an
117 * emulated/special memory area.
118 * @addr: [IN ] Linear address to access.
119 * @old: [IN ] Value expected to be current at @addr.
120 * @new: [IN ] Value to write to @addr.
121 * NOTES:
122 * 1. This function is only ever called when emulating a real CMPXCHG8B.
123 * 2. This function is *never* called on x86/64 systems.
124 * 2. Not defining this function (i.e., specifying NULL) is equivalent
125 * to defining a function that always returns X86EMUL_UNHANDLEABLE.
126 */
127 int (*cmpxchg8b_emulated) (unsigned long addr,
128 unsigned long old_lo,
129 unsigned long old_hi,
130 unsigned long new_lo,
131 unsigned long new_hi,
132 struct x86_emulate_ctxt * ctxt);
133};
134
135struct cpu_user_regs;
136
137struct x86_emulate_ctxt {
138 /* Register state before/after emulation. */
139 struct kvm_vcpu *vcpu;
140
141 /* Linear faulting address (if emulating a page-faulting instruction). */
142 unsigned long eflags;
143 unsigned long cr2;
144
145 /* Emulated execution mode, represented by an X86EMUL_MODE value. */
146 int mode;
147
148 unsigned long cs_base;
149 unsigned long ds_base;
150 unsigned long es_base;
151 unsigned long ss_base;
152 unsigned long gs_base;
153 unsigned long fs_base;
154};
155
156/* Execution mode, passed to the emulator. */
157#define X86EMUL_MODE_REAL 0 /* Real mode. */
158#define X86EMUL_MODE_PROT16 2 /* 16-bit protected mode. */
159#define X86EMUL_MODE_PROT32 4 /* 32-bit protected mode. */
160#define X86EMUL_MODE_PROT64 8 /* 64-bit (long) mode. */
161
162/* Host execution mode. */
163#if defined(__i386__)
164#define X86EMUL_MODE_HOST X86EMUL_MODE_PROT32
165#elif defined(__x86_64__)
166#define X86EMUL_MODE_HOST X86EMUL_MODE_PROT64
167#endif
168
169/*
170 * x86_emulate_memop: Emulate an instruction that faulted attempting to
171 * read/write a 'special' memory area.
172 * Returns -1 on failure, 0 on success.
173 */
174int x86_emulate_memop(struct x86_emulate_ctxt *ctxt,
175 struct x86_emulate_ops *ops);
176
177/*
178 * Given the 'reg' portion of a ModRM byte, and a register block, return a
179 * pointer into the block that addresses the relevant register.
180 * @highbyte_regs specifies whether to decode AH,CH,DH,BH.
181 */
182void *decode_register(u8 modrm_reg, unsigned long *regs,
183 int highbyte_regs);
184
185#endif /* __X86_EMULATE_H__ */
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