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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-changelog] [xen master] x86emul: make write and cmpxchg hooks optional
commit 36a808eeb2b9d365ab7ab13a8659e66e49d049bf
Author: Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Wed Dec 14 09:53:09 2016 +0100
Commit: Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Dec 14 09:53:09 2016 +0100
x86emul: make write and cmpxchg hooks optional
While the read and fetch hooks are basically unavoidable, write and
cmpxchg aren't really needed by that many insns.
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
xen/arch/x86/x86_emulate/x86_emulate.c | 49 +++++++++++++++++++++++++++++-----
1 file changed, 42 insertions(+), 7 deletions(-)
diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c
b/xen/arch/x86/x86_emulate/x86_emulate.c
index c1f512b..9da5311 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -1520,6 +1520,7 @@ protmode_load_seg(
{
uint32_t new_desc_b = desc.b | a_flag;
+ fail_if(!ops->cmpxchg);
switch ( (rc = ops->cmpxchg(sel_seg, (sel & 0xfff8) + 4, &desc.b,
&new_desc_b, sizeof(desc.b), ctxt)) )
{
@@ -2017,6 +2018,8 @@ x86_decode(
bool pc_rel = false;
int rc = X86EMUL_OKAY;
+ ASSERT(ops->insn_fetch);
+
memset(state, 0, sizeof(*state));
ea.type = OP_NONE;
ea.mem.seg = x86_seg_ds;
@@ -2494,6 +2497,8 @@ x86_emulate(
struct x86_emulate_stub stub = {};
DECLARE_ALIGNED(mmval_t, mmval);
+ ASSERT(ops->read);
+
rc = x86_decode(&state, ctxt, ops);
if ( rc != X86EMUL_OKAY )
return rc;
@@ -2658,13 +2663,18 @@ x86_emulate(
}
else if ( !(d & Mov) ) /* optimisation - avoid slow emulated read */
{
+ fail_if(lock_prefix ? !ops->cmpxchg : !ops->write);
if ( (rc = read_ulong(dst.mem.seg, dst.mem.off,
&dst.val, dst.bytes, ctxt, ops)) )
goto done;
dst.orig_val = dst.val;
}
- else /* Lock prefix is allowed only on RMW instructions. */
+ else
+ {
+ /* Lock prefix is allowed only on RMW instructions. */
generate_exception_if(lock_prefix, EXC_UD);
+ fail_if(!ops->write);
+ }
break;
}
@@ -2813,7 +2823,9 @@ x86_emulate(
unsigned long regs[] = {
_regs.eax, _regs.ecx, _regs.edx, _regs.ebx,
_regs.esp, _regs.ebp, _regs.esi, _regs.edi };
+
generate_exception_if(mode_64bit(), EXC_UD);
+ fail_if(!ops->write);
for ( i = 0; i < 8; i++ )
if ( (rc = ops->write(x86_seg_ss, sp_pre_dec(op_bytes),
®s[i], op_bytes, ctxt)) != 0 )
@@ -3112,7 +3124,7 @@ x86_emulate(
case 0x9a: /* call (far, absolute) */
ASSERT(!mode_64bit());
far_call:
- fail_if(ops->read_segment == NULL);
+ fail_if(!ops->read_segment || !ops->write);
if ( (rc = ops->read_segment(x86_seg_cs, &sreg, ctxt)) ||
(rc = load_seg(x86_seg_cs, imm2, 0, &cs, ctxt, ops)) ||
@@ -3351,6 +3363,7 @@ x86_emulate(
dst.type = OP_REG;
dst.bytes = (mode_64bit() && (op_bytes == 4)) ? 8 : op_bytes;
dst.reg = (unsigned long *)&_regs.ebp;
+ fail_if(!ops->write);
if ( (rc = ops->write(x86_seg_ss, sp_pre_dec(dst.bytes),
&_regs.ebp, dst.bytes, ctxt)) )
goto done;
@@ -4448,6 +4461,7 @@ x86_emulate(
else if ( rc != X86EMUL_UNHANDLEABLE )
goto done;
}
+ fail_if(limit && !ops->write);
while ( limit )
{
rc = ops->write(ea.mem.seg, base, &zero, sizeof(zero), ctxt);
@@ -4468,7 +4482,7 @@ x86_emulate(
case 1: /* sidt */
generate_exception_if(ea.type != OP_MEM, EXC_UD);
generate_exception_if(umip_active(ctxt, ops), EXC_GP, 0);
- fail_if(ops->read_segment == NULL);
+ fail_if(!ops->read_segment || !ops->write);
if ( (rc = ops->read_segment(seg, &sreg, ctxt)) )
goto done;
if ( mode_64bit() )
@@ -4505,12 +4519,18 @@ x86_emulate(
break;
case 4: /* smsw */
generate_exception_if(umip_active(ctxt, ops), EXC_GP, 0);
- ea.bytes = (ea.type == OP_MEM) ? 2 : op_bytes;
+ if ( ea.type == OP_MEM )
+ {
+ fail_if(!ops->write);
+ d |= Mov; /* force writeback */
+ ea.bytes = 2;
+ }
+ else
+ ea.bytes = op_bytes;
dst = ea;
fail_if(ops->read_cr == NULL);
if ( (rc = ops->read_cr(0, &dst.val, ctxt)) )
goto done;
- d |= Mov; /* force writeback */
break;
case 6: /* lmsw */
fail_if(ops->read_cr == NULL);
@@ -4712,6 +4732,8 @@ x86_emulate(
if ( !(b & 1) )
rc = ops->read(ea.mem.seg, ea.mem.off+0, mmvalp,
ea.bytes, ctxt);
+ else
+ fail_if(!ops->write); /* Check before running the stub. */
/* convert memory operand to (%rAX) */
rex_prefix &= ~REX_B;
vex.b = 1;
@@ -4726,8 +4748,11 @@ x86_emulate(
put_fpu(&fic);
put_stub(stub);
if ( !rc && (b & 1) && (ea.type == OP_MEM) )
+ {
+ ASSERT(ops->write); /* See the fail_if() above. */
rc = ops->write(ea.mem.seg, ea.mem.off, mmvalp,
ea.bytes, ctxt);
+ }
if ( rc )
goto done;
dst.type = OP_NONE;
@@ -4996,6 +5021,8 @@ x86_emulate(
if ( b == 0x6f )
rc = ops->read(ea.mem.seg, ea.mem.off+0, mmvalp,
ea.bytes, ctxt);
+ else
+ fail_if(!ops->write); /* Check before running the stub. */
}
if ( ea.type == OP_MEM || b == 0x7e )
{
@@ -5017,8 +5044,11 @@ x86_emulate(
put_fpu(&fic);
put_stub(stub);
if ( !rc && (b != 0x6f) && (ea.type == OP_MEM) )
+ {
+ ASSERT(ops->write); /* See the fail_if() above. */
rc = ops->write(ea.mem.seg, ea.mem.off, mmvalp,
ea.bytes, ctxt);
+ }
if ( rc )
goto done;
dst.type = OP_NONE;
@@ -5266,6 +5296,7 @@ x86_emulate(
generate_exception_if((modrm_reg & 7) != 1, EXC_UD);
generate_exception_if(ea.type != OP_MEM, EXC_UD);
+ fail_if(!ops->cmpxchg);
if ( op_bytes == 8 )
host_and_vcpu_must_have(cx16);
op_bytes *= 2;
@@ -5398,12 +5429,18 @@ x86_emulate(
!ctxt->force_writeback )
/* nothing to do */;
else if ( lock_prefix )
+ {
+ fail_if(!ops->cmpxchg);
rc = ops->cmpxchg(
dst.mem.seg, dst.mem.off, &dst.orig_val,
&dst.val, dst.bytes, ctxt);
+ }
else
+ {
+ fail_if(!ops->write);
rc = ops->write(
dst.mem.seg, dst.mem.off, &dst.val, dst.bytes, ctxt);
+ }
if ( rc != 0 )
goto done;
default:
@@ -5487,8 +5524,6 @@ x86_decode_insn(
const struct x86_emulate_ops ops = {
.insn_fetch = insn_fetch,
.read = x86emul_unhandleable_rw,
- .write = PTR_POISON,
- .cmpxchg = PTR_POISON,
};
int rc = x86_decode(state, ctxt, &ops);
--
generated by git-patchbot for /home/xen/git/xen.git#master
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