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x86emul: New return code for unimplemented instruction

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Enforce the distinction between an instruction not implemented by the
emulator and the failure to emulate that instruction by defining a new
return code, X86EMUL_UNIMPLEMENTED.

This value should only be returned by the core emulator when a valid
opcode is found but the execution logic for that instruction is missing.
It should NOT be returned by any of the x86_emulate_ops callbacks.

e.g. hvm_process_io_intercept should not return X86EMUL_UNIMPLEMENTED.
The return value of this function depends on either the return code of
one of the hvm_io_ops handlers (read/write) or the value returned by
hvm_copy_guest_from_phys / hvm_copy_to_guest_phys.

Similary, none of this functions should return X86EMUL_UNIMPLEMENTED.
 - hvm_io_intercept
 - hvmemul_do_io
 - hvm_send_buffered_ioreq
 - hvm_send_ioreq
 - hvm_broadcast_ioreq
 - hvmemul_do_io_buffer
 - hvmemul_validate

Also the behavior of hvm_emulate_one_insn and vmx_realmode_emulate_one
was modified to generate an Invalid Opcode trap when X86EMUL_UNRECOGNIZED
is returned by the emulator instead of just crash the domain.

Signed-off-by: Petre Pircalabu <ppircalabu@bitdefender.com>
Reviewed-by: Paul Durrant <paul.durrant@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: George Dunlap <george.dunlap@citrix.com>
This commit is contained in:
Petre Pircalabu authored and George Dunlap committed 2017-10-02 16:04:54 +01:00
1 parent 3164f2f9db
commit 63e49e966f
7 files changed
+74 -23
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xen/arch/x86/hvm/emulate.c
+12
View File
@@ -284,10 +284,15 @@ static int hvmemul_do_io(
}
break;
}
case X86EMUL_UNIMPLEMENTED:
ASSERT_UNREACHABLE();
/* Fall-through */
default:
BUG();
}
ASSERT(rc != X86EMUL_UNIMPLEMENTED);
if ( rc != X86EMUL_OKAY )
return rc;
@@ -313,6 +318,9 @@ static int hvmemul_do_io_buffer(
rc = hvmemul_do_io(is_mmio, addr, reps, size, dir, df, 0,
(uintptr_t)buffer);
ASSERT(rc != X86EMUL_UNIMPLEMENTED);
if ( rc == X86EMUL_UNHANDLEABLE && dir == IOREQ_READ )
memset(buffer, 0xff, size);
@@ -405,6 +413,8 @@ static int hvmemul_do_io_addr(
rc = hvmemul_do_io(is_mmio, addr, &count, size, dir, df, 1,
ram_gpa);
ASSERT(rc != X86EMUL_UNIMPLEMENTED);
if ( rc == X86EMUL_OKAY )
v->arch.hvm_vcpu.hvm_io.mmio_retry = (count < *reps);
@@ -2045,6 +2055,7 @@ int hvm_emulate_one_mmio(unsigned long mfn, unsigned long gla)
switch ( rc )
{
case X86EMUL_UNHANDLEABLE:
case X86EMUL_UNIMPLEMENTED:
hvm_dump_emulation_state(XENLOG_G_WARNING, "MMCFG", &ctxt);
break;
case X86EMUL_EXCEPTION:
@@ -2102,6 +2113,7 @@ void hvm_emulate_one_vm_event(enum emul_kind kind, unsigned int trapnr,
* consistent with X86EMUL_RETRY.
*/
return;
case X86EMUL_UNIMPLEMENTED:
case X86EMUL_UNHANDLEABLE:
hvm_dump_emulation_state(XENLOG_G_DEBUG, "Mem event", &ctx);
hvm_inject_hw_exception(trapnr, errcode);
xen/arch/x86/hvm/hvm.c
+1
View File
@@ -3735,6 +3735,7 @@ void hvm_ud_intercept(struct cpu_user_regs *regs)
switch ( hvm_emulate_one(&ctxt) )
{
case X86EMUL_UNHANDLEABLE:
case X86EMUL_UNIMPLEMENTED:
hvm_inject_hw_exception(TRAP_invalid_op, X86_EVENT_NO_EC);
break;
case X86EMUL_EXCEPTION:
xen/arch/x86/hvm/io.c
+5
View File
@@ -99,6 +99,11 @@ bool hvm_emulate_one_insn(hvm_emulate_validate_t *validate, const char *descr)
hvm_dump_emulation_state(XENLOG_G_WARNING, descr, &ctxt);
return false;
case X86EMUL_UNRECOGNIZED:
hvm_dump_emulation_state(XENLOG_G_WARNING, descr, &ctxt);
hvm_inject_hw_exception(TRAP_invalid_op, X86_EVENT_NO_EC);
break;
case X86EMUL_EXCEPTION:
hvm_inject_event(&ctxt.ctxt.event);
break;
xen/arch/x86/hvm/vmx/realmode.c
+9
View File
@@ -112,6 +112,15 @@ void vmx_realmode_emulate_one(struct hvm_emulate_ctxt *hvmemul_ctxt)
goto fail;
}
if ( rc == X86EMUL_UNRECOGNIZED )
{
gdprintk(XENLOG_ERR, "Unrecognized insn.\n");
if ( curr->arch.hvm_vcpu.guest_cr[0] & X86_CR0_PE )
goto fail;
realmode_deliver_exception(TRAP_invalid_op, 0, hvmemul_ctxt);
}
if ( rc == X86EMUL_EXCEPTION )
{
if ( unlikely(curr->domain->debugger_attached) &&
xen/arch/x86/mm/shadow/multi.c
+1 -1
View File
@@ -3488,7 +3488,7 @@ static int sh_page_fault(struct vcpu *v,
* would be a good unshadow hint. If we *do* decide to unshadow-on-fault
* then it must be 'failable': we cannot require the unshadow to succeed.
*/
if ( r == X86EMUL_UNHANDLEABLE )
if ( r == X86EMUL_UNHANDLEABLE || r == X86EMUL_UNIMPLEMENTED )
{
perfc_incr(shadow_fault_emulate_failed);
#if SHADOW_OPTIMIZATIONS & SHOPT_FAST_EMULATION
xen/arch/x86/x86_emulate/x86_emulate.c
+29 -22
View File
@@ -848,7 +848,8 @@ do{ asm volatile ( \
stub.func); \
generate_exception_if(res_.fields.trapnr == EXC_UD, EXC_UD); \
domain_crash(current->domain); \
goto cannot_emulate; \
rc = X86EMUL_UNHANDLEABLE; \
goto done; \
} \
} while (0)
#else
@@ -2585,7 +2586,7 @@ x86_decode(
d = twobyte_table[0x3a].desc;
break;
default:
rc = X86EMUL_UNHANDLEABLE;
rc = X86EMUL_UNRECOGNIZED;
goto done;
}
}
@@ -2599,7 +2600,7 @@ x86_decode(
}
else
{
rc = X86EMUL_UNHANDLEABLE;
rc = X86EMUL_UNRECOGNIZED;
goto done;
}
@@ -2879,7 +2880,7 @@ x86_decode(
default:
ASSERT_UNREACHABLE();
return X86EMUL_UNHANDLEABLE;
return X86EMUL_UNIMPLEMENTED;
}
if ( ea.type == OP_MEM )
@@ -4193,7 +4194,7 @@ x86_emulate(
break;
case 4: /* fldenv - TODO */
state->fpu_ctrl = true;
goto cannot_emulate;
goto unimplemented_insn;
case 5: /* fldcw m2byte */
state->fpu_ctrl = true;
if ( (rc = ops->read(ea.mem.seg, ea.mem.off, &src.val,
@@ -4204,7 +4205,7 @@ x86_emulate(
break;
case 6: /* fnstenv - TODO */
state->fpu_ctrl = true;
goto cannot_emulate;
goto unimplemented_insn;
case 7: /* fnstcw m2byte */
state->fpu_ctrl = true;
emulate_fpu_insn_memdst("fnstcw", dst.val);
@@ -4440,7 +4441,7 @@ x86_emulate(
case 4: /* frstor - TODO */
case 6: /* fnsave - TODO */
state->fpu_ctrl = true;
goto cannot_emulate;
goto unimplemented_insn;
case 7: /* fnstsw m2byte */
state->fpu_ctrl = true;
emulate_fpu_insn_memdst("fnstsw", dst.val);
@@ -5199,7 +5200,7 @@ x86_emulate(
#undef _GRP7
default:
goto cannot_emulate;
goto unimplemented_insn;
}
break;
}
@@ -6197,7 +6198,7 @@ x86_emulate(
/* vpsll{w,d} $imm8,{x,y}mm,{x,y}mm */
break;
default:
goto cannot_emulate;
goto unrecognized_insn;
}
simd_0f_shift_imm:
generate_exception_if(ea.type != OP_REG, EXC_UD);
@@ -6245,7 +6246,7 @@ x86_emulate(
case 6: /* psllq $imm8,mm */
goto simd_0f_shift_imm;
}
goto cannot_emulate;
goto unrecognized_insn;
case X86EMUL_OPC_66(0x0f, 0x73):
case X86EMUL_OPC_VEX_66(0x0f, 0x73):
@@ -6261,7 +6262,7 @@ x86_emulate(
/* vpslldq $imm8,{x,y}mm,{x,y}mm */
goto simd_0f_shift_imm;
}
goto cannot_emulate;
goto unrecognized_insn;
case X86EMUL_OPC(0x0f, 0x77): /* emms */
case X86EMUL_OPC_VEX(0x0f, 0x77): /* vzero{all,upper} */
@@ -6325,7 +6326,7 @@ x86_emulate(
case 0: /* extrq $imm8,$imm8,xmm */
break;
default:
goto cannot_emulate;
goto unrecognized_insn;
}
/* fall through */
case X86EMUL_OPC_F2(0x0f, 0x78): /* insertq $imm8,$imm8,xmm,xmm */
@@ -6520,7 +6521,7 @@ x86_emulate(
goto done;
break;
default:
goto cannot_emulate;
goto unimplemented_insn;
}
break;
@@ -6536,7 +6537,7 @@ x86_emulate(
vcpu_must_have(avx);
goto stmxcsr;
}
goto cannot_emulate;
goto unrecognized_insn;
case X86EMUL_OPC_F3(0x0f, 0xae): /* Grp15 */
fail_if(modrm_mod != 3);
@@ -6779,10 +6780,10 @@ x86_emulate(
switch ( modrm_reg & 7 )
{
default:
goto cannot_emulate;
goto unrecognized_insn;
#ifdef HAVE_GAS_RDRAND
case 6: /* rdrand */
#ifdef HAVE_GAS_RDRAND
generate_exception_if(rep_prefix(), EXC_UD);
host_and_vcpu_must_have(rdrand);
dst = ea;
@@ -6807,6 +6808,8 @@ x86_emulate(
if ( carry )
_regs.eflags |= X86_EFLAGS_CF;
break;
#else
goto unimplemented_insn;
#endif
case 7: /* rdseed / rdpid */
@@ -7361,7 +7364,7 @@ x86_emulate(
host_and_vcpu_must_have(bmi1);
break;
default:
goto cannot_emulate;
goto unrecognized_insn;
}
generate_exception_if(vex.l, EXC_UD);
@@ -7672,7 +7675,7 @@ x86_emulate(
host_and_vcpu_must_have(tbm);
break;
default:
goto cannot_emulate;
goto unrecognized_insn;
}
xop_09_rm_rv:
@@ -7706,7 +7709,7 @@ x86_emulate(
host_and_vcpu_must_have(tbm);
goto xop_09_rm_rv;
}
goto cannot_emulate;
goto unrecognized_insn;
case X86EMUL_OPC_XOP(0a, 0x10): /* bextr imm,r/m,r */
{
@@ -7738,8 +7741,11 @@ x86_emulate(
}
default:
cannot_emulate:
rc = X86EMUL_UNHANDLEABLE;
unimplemented_insn:
rc = X86EMUL_UNIMPLEMENTED;
goto done;
unrecognized_insn:
rc = X86EMUL_UNRECOGNIZED;
goto done;
}
@@ -7791,7 +7797,8 @@ x86_emulate(
if ( (d & DstMask) != DstMem )
{
ASSERT_UNREACHABLE();
goto cannot_emulate;
rc = X86EMUL_UNHANDLEABLE;
goto done;
}
break;
}
xen/arch/x86/x86_emulate/x86_emulate.h
+17
View File
@@ -133,6 +133,23 @@ struct x86_emul_fpu_aux {
* Undefined behavior when used anywhere else.
*/
#define X86EMUL_DONE 4
/*
* Current instruction is not implemented by the emulator.
* This value should only be returned by the core emulator when a valid
* opcode is found but the execution logic for that instruction is missing.
* It should NOT be returned by any of the x86_emulate_ops callbacks.
*/
#define X86EMUL_UNIMPLEMENTED 5
/*
* The current instruction's opcode is not valid.
* If this error code is returned by a function, an #UD trap should be
* raised by the final consumer of it.
*
* TODO: For the moment X86EMUL_UNRECOGNIZED and X86EMUL_UNIMPLEMENTED
* can be used interchangeably therefore raising an #UD trap is not
* strictly expected for now.
*/
#define X86EMUL_UNRECOGNIZED X86EMUL_UNIMPLEMENTED
/* FPU sub-types which may be requested via ->get_fpu(). */
enum x86_emulate_fpu_type {
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