drivers/kvm/x86_emulate.h

   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
  14 struct 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 */
  54 struct 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
 135 struct cpu_user_regs;
 136
 137 struct 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(CONFIG_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  */
 174 int 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  */
 182 void *decode_register(u8 modrm_reg, unsigned long *regs,
 183                       int highbyte_regs);
 184
 185 #endif                          /* __X86_EMULATE_H__ */