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, void *val,
  63                         unsigned int bytes, struct kvm_vcpu *vcpu);
  64
  65         /*
  66          * write_std: Write bytes of standard (non-emulated/special) memory.
  67          *            Used for stack operations, and others.
  68          *  @addr:  [IN ] Linear address to which to write.
  69          *  @val:   [IN ] Value to write to memory (low-order bytes used as
  70          *                required).
  71          *  @bytes: [IN ] Number of bytes to write to memory.
  72          */
  73         int (*write_std)(unsigned long addr, const void *val,
  74                          unsigned int bytes, struct kvm_vcpu *vcpu);
  75
  76         /*
  77          * read_emulated: Read bytes from emulated/special memory area.
  78          *  @addr:  [IN ] Linear address from which to read.
  79          *  @val:   [OUT] Value read from memory, zero-extended to 'u_long'.
  80          *  @bytes: [IN ] Number of bytes to read from memory.
  81          */
  82         int (*read_emulated) (unsigned long addr,
  83                               void *val,
  84                               unsigned int bytes,
  85                               struct kvm_vcpu *vcpu);
  86
  87         /*
  88          * write_emulated: Read bytes from emulated/special memory area.
  89          *  @addr:  [IN ] Linear address to which to write.
  90          *  @val:   [IN ] Value to write to memory (low-order bytes used as
  91          *                required).
  92          *  @bytes: [IN ] Number of bytes to write to memory.
  93          */
  94         int (*write_emulated) (unsigned long addr,
  95                                const void *val,
  96                                unsigned int bytes,
  97                                struct kvm_vcpu *vcpu);
  98
  99         /*
 100          * cmpxchg_emulated: Emulate an atomic (LOCKed) CMPXCHG operation on an
 101          *                   emulated/special memory area.
 102          *  @addr:  [IN ] Linear address to access.
 103          *  @old:   [IN ] Value expected to be current at @addr.
 104          *  @new:   [IN ] Value to write to @addr.
 105          *  @bytes: [IN ] Number of bytes to access using CMPXCHG.
 106          */
 107         int (*cmpxchg_emulated) (unsigned long addr,
 108                                  const void *old,
 109                                  const void *new,
 110                                  unsigned int bytes,
 111                                  struct kvm_vcpu *vcpu);
 112
 113 };
 114
 115 struct x86_emulate_ctxt {
 116         /* Register state before/after emulation. */
 117         struct kvm_vcpu *vcpu;
 118
 119         /* Linear faulting address (if emulating a page-faulting instruction). */
 120         unsigned long eflags;
 121         unsigned long cr2;
 122
 123         /* Emulated execution mode, represented by an X86EMUL_MODE value. */
 124         int mode;
 125
 126         unsigned long cs_base;
 127         unsigned long ds_base;
 128         unsigned long es_base;
 129         unsigned long ss_base;
 130         unsigned long gs_base;
 131         unsigned long fs_base;
 132 };
 133
 134 /* Execution mode, passed to the emulator. */
 135 #define X86EMUL_MODE_REAL     0 /* Real mode.             */
 136 #define X86EMUL_MODE_PROT16   2 /* 16-bit protected mode. */
 137 #define X86EMUL_MODE_PROT32   4 /* 32-bit protected mode. */
 138 #define X86EMUL_MODE_PROT64   8 /* 64-bit (long) mode.    */
 139
 140 /* Host execution mode. */
 141 #if defined(__i386__)
 142 #define X86EMUL_MODE_HOST X86EMUL_MODE_PROT32
 143 #elif defined(CONFIG_X86_64)
 144 #define X86EMUL_MODE_HOST X86EMUL_MODE_PROT64
 145 #endif
 146
 147 /*
 148  * x86_emulate_memop: Emulate an instruction that faulted attempting to
 149  *                    read/write a 'special' memory area.
 150  * Returns -1 on failure, 0 on success.
 151  */
 152 int x86_emulate_memop(struct x86_emulate_ctxt *ctxt,
 153                       struct x86_emulate_ops *ops);
 154
 155 #endif                          /* __X86_EMULATE_H__ */