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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v2 03/16] x86emul: track only rIP in emulator state
Now that all decoding happens in x86_decode() there's no need to keep
the local registers copy in struct x86_emulate_state. Only rIP gets
updated in the decode phase, so only that register needs tracking
there. All other (read-only) registers can be read from the original
structure (but sadly, due to it getting passed to decode_register(),
the pointer can't be made point to "const" to make the compiler help
ensure no modification happens).
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
v2: Defer decoding register of the ModRM mod 3 case until the
execution phase.
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -590,9 +590,9 @@ do{ asm volatile (
/* Fetch next part of the instruction being emulated. */
#define insn_fetch_bytes(_size) \
-({ unsigned long _x = 0, _eip = _regs.eip; \
- _regs.eip += (_size); /* real hardware doesn't truncate */ \
- generate_exception_if((uint8_t)(_regs.eip - \
+({ unsigned long _x = 0, _eip = state->eip; \
+ state->eip += (_size); /* real hardware doesn't truncate */ \
+ generate_exception_if((uint8_t)(state->eip - \
ctxt->regs->eip) > MAX_INST_LEN, \
EXC_GP, 0); \
rc = ops->insn_fetch(x86_seg_cs, _eip, &_x, (_size), ctxt); \
@@ -1593,8 +1593,8 @@ struct x86_emulate_state {
#define imm1 ea.val
#define imm2 ea.orig_val
- /* Shadow copy of register state. Committed on successful emulation. */
- struct cpu_user_regs regs;
+ unsigned long eip;
+ struct cpu_user_regs *regs;
};
/* Helper definitions. */
@@ -1610,7 +1610,6 @@ struct x86_emulate_state {
#define vex (state->vex)
#define override_seg (state->override_seg)
#define ea (state->ea)
-#define _regs (state->regs)
static int
x86_decode_onebyte(
@@ -1666,7 +1665,8 @@ x86_decode(
ea.type = OP_MEM;
ea.mem.seg = x86_seg_ds;
ea.reg = REG_POISON;
- _regs = *ctxt->regs;
+ state->regs = ctxt->regs;
+ state->eip = ctxt->regs->eip;
ctxt->retire.byte = 0;
@@ -1770,7 +1770,7 @@ x86_decode(
default:
BUG();
case 2:
- if ( in_realmode(ctxt, ops) || (_regs.eflags & EFLG_VM) )
+ if ( in_realmode(ctxt, ops) || (state->regs->eflags & EFLG_VM)
)
break;
/* fall through */
case 4:
@@ -1895,8 +1895,6 @@ x86_decode(
{
modrm_rm |= (rex_prefix & 1) << 3;
ea.type = OP_REG;
- ea.reg = decode_register(
- modrm_rm, &_regs, (d & ByteOp) && (rex_prefix == 0));
}
else if ( ad_bytes == 2 )
{
@@ -1904,33 +1902,33 @@ x86_decode(
switch ( modrm_rm )
{
case 0:
- ea.mem.off = _regs.ebx + _regs.esi;
+ ea.mem.off = state->regs->ebx + state->regs->esi;
break;
case 1:
- ea.mem.off = _regs.ebx + _regs.edi;
+ ea.mem.off = state->regs->ebx + state->regs->edi;
break;
case 2:
ea.mem.seg = x86_seg_ss;
- ea.mem.off = _regs.ebp + _regs.esi;
+ ea.mem.off = state->regs->ebp + state->regs->esi;
break;
case 3:
ea.mem.seg = x86_seg_ss;
- ea.mem.off = _regs.ebp + _regs.edi;
+ ea.mem.off = state->regs->ebp + state->regs->edi;
break;
case 4:
- ea.mem.off = _regs.esi;
+ ea.mem.off = state->regs->esi;
break;
case 5:
- ea.mem.off = _regs.edi;
+ ea.mem.off = state->regs->edi;
break;
case 6:
if ( modrm_mod == 0 )
break;
ea.mem.seg = x86_seg_ss;
- ea.mem.off = _regs.ebp;
+ ea.mem.off = state->regs->ebp;
break;
case 7:
- ea.mem.off = _regs.ebx;
+ ea.mem.off = state->regs->ebx;
break;
}
switch ( modrm_mod )
@@ -1957,14 +1955,15 @@ x86_decode(
sib_index = ((sib >> 3) & 7) | ((rex_prefix << 2) & 8);
sib_base = (sib & 7) | ((rex_prefix << 3) & 8);
if ( sib_index != 4 )
- ea.mem.off = *(long*)decode_register(sib_index, &_regs, 0);
+ ea.mem.off = *(long *)decode_register(sib_index,
+ state->regs, 0);
ea.mem.off <<= (sib >> 6) & 3;
if ( (modrm_mod == 0) && ((sib_base & 7) == 5) )
ea.mem.off += insn_fetch_type(int32_t);
else if ( sib_base == 4 )
{
ea.mem.seg = x86_seg_ss;
- ea.mem.off += _regs.esp;
+ ea.mem.off += state->regs->esp;
if ( !ext && (b == 0x8f) )
/* POP <rm> computes its EA post increment. */
ea.mem.off += ((mode_64bit() && (op_bytes == 4))
@@ -1973,15 +1972,17 @@ x86_decode(
else if ( sib_base == 5 )
{
ea.mem.seg = x86_seg_ss;
- ea.mem.off += _regs.ebp;
+ ea.mem.off += state->regs->ebp;
}
else
- ea.mem.off += *(long*)decode_register(sib_base, &_regs, 0);
+ ea.mem.off += *(long *)decode_register(sib_base,
+ state->regs, 0);
}
else
{
modrm_rm |= (rex_prefix & 1) << 3;
- ea.mem.off = *(long *)decode_register(modrm_rm, &_regs, 0);
+ ea.mem.off = *(long *)decode_register(modrm_rm,
+ state->regs, 0);
if ( (modrm_rm == 5) && (modrm_mod != 0) )
ea.mem.seg = x86_seg_ss;
}
@@ -1994,7 +1995,7 @@ x86_decode(
if ( !mode_64bit() )
break;
/* Relative to RIP of next instruction. Argh! */
- ea.mem.off += _regs.eip;
+ ea.mem.off += state->eip;
if ( (d & SrcMask) == SrcImm )
ea.mem.off += (d & ByteOp) ? 1 :
((op_bytes == 8) ? 4 : op_bytes);
@@ -2072,6 +2073,8 @@ x86_emulate(
struct x86_emulate_ctxt *ctxt,
const struct x86_emulate_ops *ops)
{
+ /* Shadow copy of register state. Committed on successful emulation. */
+ struct cpu_user_regs _regs = *ctxt->regs;
struct x86_emulate_state state;
int rc;
uint8_t b, d;
@@ -2085,10 +2088,17 @@ x86_emulate(
if ( rc != X86EMUL_OKAY )
return rc;
+ /* Sync rIP to post decode value. */
+ _regs.eip = state.eip;
+
b = state.opcode;
d = state.desc;
#define state (&state)
+ if ( ea.type == OP_REG )
+ ea.reg = decode_register(modrm_rm, &_regs,
+ (d & ByteOp) && !rex_prefix);
+
/* Decode and fetch the source operand: register, memory or immediate. */
switch ( d & SrcMask )
{
@@ -5005,4 +5015,3 @@ x86_emulate(
#undef vex
#undef override_seg
#undef ea
-#undef _regs
Attachment:
x86emul-decode-regs-pointer.patch _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx https://lists.xen.org/xen-devel
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