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x86/emul: Improvements to internal users of decode_register()
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Most users of decode_register() can be replaced with decode_gpr() right away.

For the few sites which do care about possibly using the legacy byteop
encoding, rename decode_register() to _decode_gpr() (to match its non-legacy
counterpart), and adjust its 'int highbyte_regs' parameter to the more correct
'bool legacy'.

Signed-off-by: Andrew Cooper <[email protected]>
Reviewed-by: Jan Beulich <[email protected]>
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@andyhhp
andyhhp committed Jan 31, 2018
1 parent 8e67c41 commit 9885e4d
Showing 1 changed file with 30 additions and 39 deletions.
69 changes: 30 additions & 39 deletions xen/arch/x86/x86_emulate/x86_emulate.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1957,9 +1957,8 @@ const uint8_t cpu_user_regs_gpr_offsets[] = {
#endif
};

void *
decode_register(
uint8_t modrm_reg, struct cpu_user_regs *regs, int highbyte_regs)
static void *_decode_gpr(
struct cpu_user_regs *regs, unsigned int modrm_reg, bool legacy)
{
static const uint8_t byte_reg_offsets[] = {
offsetof(struct cpu_user_regs, al),
Expand All @@ -1972,7 +1971,7 @@ decode_register(
offsetof(struct cpu_user_regs, bh),
};

if ( !highbyte_regs )
if ( !legacy )
return decode_gpr(regs, modrm_reg);

/* Check that the array is a power of two. */
Expand All @@ -1987,10 +1986,11 @@ decode_register(
return (void *)regs + byte_reg_offsets[modrm_reg];
}

static void *decode_vex_gpr(unsigned int vex_reg, struct cpu_user_regs *regs,
const struct x86_emulate_ctxt *ctxt)
static unsigned long *decode_vex_gpr(
unsigned int vex_reg, struct cpu_user_regs *regs,
const struct x86_emulate_ctxt *ctxt)
{
return decode_register(~vex_reg & (mode_64bit() ? 0xf : 7), regs, 0);
return decode_gpr(regs, ~vex_reg & (mode_64bit() ? 0xf : 7));
}

static bool is_aligned(enum x86_segment seg, unsigned long offs,
Expand Down Expand Up @@ -2799,8 +2799,7 @@ x86_decode(
sib_index = ((sib >> 3) & 7) | ((rex_prefix << 2) & 8);
sib_base = (sib & 7) | ((rex_prefix << 3) & 8);
if ( sib_index != 4 && !(d & vSIB) )
ea.mem.off = *(long *)decode_register(sib_index,
state->regs, 0);
ea.mem.off = *decode_gpr(state->regs, sib_index);
ea.mem.off <<= (sib >> 6) & 3;
if ( (modrm_mod == 0) && ((sib_base & 7) == 5) )
ea.mem.off += insn_fetch_type(int32_t);
Expand All @@ -2819,15 +2818,13 @@ x86_decode(
ea.mem.off += state->regs->r(bp);
}
else
ea.mem.off += *(long *)decode_register(sib_base,
state->regs, 0);
ea.mem.off += *decode_gpr(state->regs, sib_base);
}
else
{
generate_exception_if(d & vSIB, EXC_UD);
modrm_rm |= (rex_prefix & 1) << 3;
ea.mem.off = *(long *)decode_register(modrm_rm,
state->regs, 0);
ea.mem.off = *decode_gpr(state->regs, modrm_rm);
if ( (modrm_rm == 5) && (modrm_mod != 0) )
ea.mem.seg = x86_seg_ss;
}
Expand Down Expand Up @@ -3052,8 +3049,7 @@ x86_emulate(
generate_exception_if(state->not_64bit && mode_64bit(), EXC_UD);

if ( ea.type == OP_REG )
ea.reg = decode_register(modrm_rm, &_regs,
(d & ByteOp) && !rex_prefix);
ea.reg = _decode_gpr(&_regs, modrm_rm, (d & ByteOp) && !rex_prefix);

memset(mmvalp, 0xaa /* arbitrary */, sizeof(*mmvalp));

Expand All @@ -3067,13 +3063,13 @@ x86_emulate(
src.type = OP_REG;
if ( d & ByteOp )
{
src.reg = decode_register(modrm_reg, &_regs, (rex_prefix == 0));
src.reg = _decode_gpr(&_regs, modrm_reg, !rex_prefix);
src.val = *(uint8_t *)src.reg;
src.bytes = 1;
}
else
{
src.reg = decode_register(modrm_reg, &_regs, 0);
src.reg = decode_gpr(&_regs, modrm_reg);
switch ( (src.bytes = op_bytes) )
{
case 2: src.val = *(uint16_t *)src.reg; break;
Expand Down Expand Up @@ -3143,13 +3139,13 @@ x86_emulate(
dst.type = OP_REG;
if ( d & ByteOp )
{
dst.reg = decode_register(modrm_reg, &_regs, (rex_prefix == 0));
dst.reg = _decode_gpr(&_regs, modrm_reg, !rex_prefix);
dst.val = *(uint8_t *)dst.reg;
dst.bytes = 1;
}
else
{
dst.reg = decode_register(modrm_reg, &_regs, 0);
dst.reg = decode_gpr(&_regs, modrm_reg);
switch ( (dst.bytes = op_bytes) )
{
case 2: dst.val = *(uint16_t *)dst.reg; break;
Expand Down Expand Up @@ -3339,7 +3335,7 @@ x86_emulate(

case 0x40 ... 0x4f: /* inc/dec reg */
dst.type = OP_REG;
dst.reg = decode_register(b & 7, &_regs, 0);
dst.reg = decode_gpr(&_regs, b & 7);
dst.bytes = op_bytes;
dst.val = *dst.reg;
if ( b & 8 )
Expand All @@ -3349,14 +3345,12 @@ x86_emulate(
break;

case 0x50 ... 0x57: /* push reg */
src.val = *(unsigned long *)decode_register(
(b & 7) | ((rex_prefix & 1) << 3), &_regs, 0);
src.val = *decode_gpr(&_regs, (b & 7) | ((rex_prefix & 1) << 3));
goto push;

case 0x58 ... 0x5f: /* pop reg */
dst.type = OP_REG;
dst.reg = decode_register(
(b & 7) | ((rex_prefix & 1) << 3), &_regs, 0);
dst.reg = decode_gpr(&_regs, (b & 7) | ((rex_prefix & 1) << 3));
dst.bytes = op_bytes;
if ( mode_64bit() && (dst.bytes == 4) )
dst.bytes = 8;
Expand All @@ -3370,7 +3364,7 @@ x86_emulate(
ea.val = _regs.esp;
for ( i = 0; i < 8; i++ )
{
void *reg = decode_register(i, &_regs, 0);
void *reg = decode_gpr(&_regs, i);

if ( (rc = ops->write(x86_seg_ss, sp_pre_dec(op_bytes),
reg != &_regs.esp ? reg : &ea.val,
Expand All @@ -3382,7 +3376,7 @@ x86_emulate(
case 0x61: /* popa */
for ( i = 0; i < 8; i++ )
{
void *reg = decode_register(7 - i, &_regs, 0);
void *reg = decode_gpr(&_regs, 7 - i);

if ( (rc = read_ulong(x86_seg_ss, sp_post_inc(op_bytes),
&dst.val, op_bytes, ctxt, ops)) != 0 )
Expand Down Expand Up @@ -3662,8 +3656,7 @@ x86_emulate(
case 0x91 ... 0x97: /* xchg reg,%%rax */
dst.type = OP_REG;
dst.bytes = op_bytes;
dst.reg = decode_register(
(b & 7) | ((rex_prefix & 1) << 3), &_regs, 0);
dst.reg = decode_gpr(&_regs, (b & 7) | ((rex_prefix & 1) << 3));
dst.val = *dst.reg;
goto xchg;

Expand Down Expand Up @@ -3895,14 +3888,13 @@ x86_emulate(
}

case 0xb0 ... 0xb7: /* mov imm8,r8 */
dst.reg = decode_register(
(b & 7) | ((rex_prefix & 1) << 3), &_regs, (rex_prefix == 0));
dst.reg = _decode_gpr(&_regs, (b & 7) | ((rex_prefix & 1) << 3),
!rex_prefix);
dst.val = src.val;
break;

case 0xb8 ... 0xbf: /* mov imm{16,32,64},r{16,32,64} */
dst.reg = decode_register(
(b & 7) | ((rex_prefix & 1) << 3), &_regs, 0);
dst.reg = decode_gpr(&_regs, (b & 7) | ((rex_prefix & 1) << 3));
dst.val = src.val;
break;

Expand Down Expand Up @@ -5684,7 +5676,7 @@ x86_emulate(
opc[2] = 0xc3;

copy_REX_VEX(opc, rex_prefix, vex);
ea.reg = decode_register(modrm_reg, &_regs, 0);
ea.reg = decode_gpr(&_regs, modrm_reg);
invoke_stub("", "", "=a" (*ea.reg), "+m" (fic.exn_raised)
: "c" (mmvalp), "m" (*mmvalp));

Expand Down Expand Up @@ -6461,7 +6453,7 @@ x86_emulate(
else
{
shift = src.val;
src.reg = decode_register(modrm_reg, &_regs, 0);
src.reg = decode_gpr(&_regs, modrm_reg);
src.val = truncate_word(*src.reg, dst.bytes);
}
if ( (shift &= width - 1) == 0 )
Expand Down Expand Up @@ -6580,7 +6572,7 @@ x86_emulate(
fail_if(!ops->read_segment);
if ( (rc = ops->read_segment(seg, &sreg, ctxt)) != X86EMUL_OKAY )
goto done;
dst.reg = decode_register(modrm_rm, &_regs, 0);
dst.reg = decode_gpr(&_regs, modrm_rm);
if ( !(modrm_reg & 2) )
{
/* rd{f,g}sbase */
Expand Down Expand Up @@ -6640,7 +6632,7 @@ x86_emulate(

case X86EMUL_OPC(0x0f, 0xb6): /* movzx rm8,r{16,32,64} */
/* Recompute DstReg as we may have decoded AH/BH/CH/DH. */
dst.reg = decode_register(modrm_reg, &_regs, 0);
dst.reg = decode_gpr(&_regs, modrm_reg);
dst.bytes = op_bytes;
dst.val = (uint8_t)src.val;
break;
Expand Down Expand Up @@ -6732,7 +6724,7 @@ x86_emulate(

case X86EMUL_OPC(0x0f, 0xbe): /* movsx rm8,r{16,32,64} */
/* Recompute DstReg as we may have decoded AH/BH/CH/DH. */
dst.reg = decode_register(modrm_reg, &_regs, 0);
dst.reg = decode_gpr(&_regs, modrm_reg);
dst.bytes = op_bytes;
dst.val = (int8_t)src.val;
break;
Expand Down Expand Up @@ -6957,8 +6949,7 @@ x86_emulate(

case X86EMUL_OPC(0x0f, 0xc8) ... X86EMUL_OPC(0x0f, 0xcf): /* bswap */
dst.type = OP_REG;
dst.reg = decode_register(
(b & 7) | ((rex_prefix & 1) << 3), &_regs, 0);
dst.reg = decode_gpr(&_regs, (b & 7) | ((rex_prefix & 1) << 3));
switch ( dst.bytes = op_bytes )
{
default: /* case 2: */
Expand Down

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