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    Subject[PATCH 39/54] KVM: x86 emulator: Fix stack instructions on 64-bit mode
    Date
    Stack instructions are always 64-bit on 64-bit mode; many of the
    emulated stack instructions did not take that into account. Fix by
    adding a 'Stack' bitflag and setting the operand size appropriately
    during the decode stage (except for 'push r/m', which is in a group
    with a few other instructions, so it gets its own treatment).

    This fixes random crashes on Vista x64.

    Signed-off-by: Avi Kivity <avi@qumranet.com>
    ---
    drivers/kvm/x86_emulate.c | 27 +++++++++++++++------------
    1 files changed, 15 insertions(+), 12 deletions(-)

    diff --git a/drivers/kvm/x86_emulate.c b/drivers/kvm/x86_emulate.c
    index f423b0e..0a6ab06 100644
    --- a/drivers/kvm/x86_emulate.c
    +++ b/drivers/kvm/x86_emulate.c
    @@ -65,6 +65,7 @@
    #define BitOp (1<<8)
    #define MemAbs (1<<9) /* Memory operand is absolute displacement */
    #define String (1<<10) /* String instruction (rep capable) */
    +#define Stack (1<<11) /* Stack instruction (push/pop) */

    static u16 opcode_table[256] = {
    /* 0x00 - 0x07 */
    @@ -104,14 +105,16 @@ static u16 opcode_table[256] = {
    /* 0x48 - 0x4F */
    DstReg, DstReg, DstReg, DstReg, DstReg, DstReg, DstReg, DstReg,
    /* 0x50 - 0x57 */
    - SrcReg, SrcReg, SrcReg, SrcReg, SrcReg, SrcReg, SrcReg, SrcReg,
    + SrcReg | Stack, SrcReg | Stack, SrcReg | Stack, SrcReg | Stack,
    + SrcReg | Stack, SrcReg | Stack, SrcReg | Stack, SrcReg | Stack,
    /* 0x58 - 0x5F */
    - DstReg, DstReg, DstReg, DstReg, DstReg, DstReg, DstReg, DstReg,
    + DstReg | Stack, DstReg | Stack, DstReg | Stack, DstReg | Stack,
    + DstReg | Stack, DstReg | Stack, DstReg | Stack, DstReg | Stack,
    /* 0x60 - 0x67 */
    0, 0, 0, DstReg | SrcMem32 | ModRM | Mov /* movsxd (x86/64) */ ,
    0, 0, 0, 0,
    /* 0x68 - 0x6F */
    - 0, 0, ImplicitOps|Mov, 0,
    + 0, 0, ImplicitOps | Mov | Stack, 0,
    SrcNone | ByteOp | ImplicitOps, SrcNone | ImplicitOps, /* insb, insw/insd */
    SrcNone | ByteOp | ImplicitOps, SrcNone | ImplicitOps, /* outsb, outsw/outsd */
    /* 0x70 - 0x77 */
    @@ -128,9 +131,10 @@ static u16 opcode_table[256] = {
    /* 0x88 - 0x8F */
    ByteOp | DstMem | SrcReg | ModRM | Mov, DstMem | SrcReg | ModRM | Mov,
    ByteOp | DstReg | SrcMem | ModRM | Mov, DstReg | SrcMem | ModRM | Mov,
    - 0, ModRM | DstReg, 0, DstMem | SrcNone | ModRM | Mov,
    + 0, ModRM | DstReg, 0, DstMem | SrcNone | ModRM | Mov | Stack,
    /* 0x90 - 0x9F */
    - 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, ImplicitOps, ImplicitOps, 0, 0,
    + 0, 0, 0, 0, 0, 0, 0, 0,
    + 0, 0, 0, 0, ImplicitOps | Stack, ImplicitOps | Stack, 0, 0,
    /* 0xA0 - 0xA7 */
    ByteOp | DstReg | SrcMem | Mov | MemAbs, DstReg | SrcMem | Mov | MemAbs,
    ByteOp | DstMem | SrcReg | Mov | MemAbs, DstMem | SrcReg | Mov | MemAbs,
    @@ -144,7 +148,7 @@ static u16 opcode_table[256] = {
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    /* 0xC0 - 0xC7 */
    ByteOp | DstMem | SrcImm | ModRM, DstMem | SrcImmByte | ModRM,
    - 0, ImplicitOps, 0, 0,
    + 0, ImplicitOps | Stack, 0, 0,
    ByteOp | DstMem | SrcImm | ModRM | Mov, DstMem | SrcImm | ModRM | Mov,
    /* 0xC8 - 0xCF */
    0, 0, 0, 0, 0, 0, 0, 0,
    @@ -157,7 +161,8 @@ static u16 opcode_table[256] = {
    /* 0xE0 - 0xE7 */
    0, 0, 0, 0, 0, 0, 0, 0,
    /* 0xE8 - 0xEF */
    - ImplicitOps, SrcImm|ImplicitOps, 0, SrcImmByte|ImplicitOps, 0, 0, 0, 0,
    + ImplicitOps | Stack, SrcImm|ImplicitOps, 0, SrcImmByte|ImplicitOps,
    + 0, 0, 0, 0,
    /* 0xF0 - 0xF7 */
    0, 0, 0, 0,
    ImplicitOps, ImplicitOps,
    @@ -868,6 +873,9 @@ done_prefixes:
    }
    }

    + if (mode == X86EMUL_MODE_PROT64 && (c->d & Stack))
    + c->op_bytes = 8;
    +
    /* ModRM and SIB bytes. */
    if (c->d & ModRM)
    rc = decode_modrm(ctxt, ops);
    @@ -988,11 +996,6 @@ static inline int emulate_grp1a(struct x86_emulate_ctxt *ctxt,
    struct decode_cache *c = &ctxt->decode;
    int rc;

    - /* 64-bit mode: POP always pops a 64-bit operand. */
    -
    - if (ctxt->mode == X86EMUL_MODE_PROT64)
    - c->dst.bytes = 8;
    -
    rc = ops->read_std(register_address(ctxt->ss_base,
    c->regs[VCPU_REGS_RSP]),
    &c->dst.val, c->dst.bytes, ctxt->vcpu);
    --
    1.5.3.7


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