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/******************************************************************************
* arch/x86/hvm/vmx/realmode.c
*
* Real-mode emulation for VMX.
*
* Copyright (c) 2007-2008 Citrix Systems, Inc.
*
* Authors:
* Keir Fraser <keir@xen.org>
*/
#include <xen/config.h>
#include <xen/init.h>
#include <xen/lib.h>
#include <xen/sched.h>
#include <xen/paging.h>
#include <xen/softirq.h>
#include <asm/event.h>
#include <asm/hvm/emulate.h>
#include <asm/hvm/hvm.h>
#include <asm/hvm/support.h>
#include <asm/hvm/vmx/vmx.h>
#include <asm/hvm/vmx/vmcs.h>
static void realmode_deliver_exception(
unsigned int vector,
unsigned int insn_len,
struct hvm_emulate_ctxt *hvmemul_ctxt)
{
struct segment_register *idtr, *csr;
struct cpu_user_regs *regs = hvmemul_ctxt->ctxt.regs;
uint32_t cs_eip, pstk;
uint16_t frame[3];
unsigned int last_byte;
idtr = hvmemul_get_seg_reg(x86_seg_idtr, hvmemul_ctxt);
csr = hvmemul_get_seg_reg(x86_seg_cs, hvmemul_ctxt);
__set_bit(x86_seg_cs, &hvmemul_ctxt->seg_reg_dirty);
again:
last_byte = (vector * 4) + 3;
if ( idtr->limit < last_byte )
{
/* Software interrupt? */
if ( insn_len != 0 )
{
insn_len = 0;
vector = TRAP_gp_fault;
goto again;
}
/* Exception or hardware interrupt. */
switch ( vector )
{
case TRAP_double_fault:
hvm_triple_fault();
return;
case TRAP_gp_fault:
vector = TRAP_double_fault;
goto again;
default:
vector = TRAP_gp_fault;
goto again;
}
}
(void)hvm_copy_from_guest_phys(&cs_eip, idtr->base + vector * 4, 4);
frame[0] = regs->eip + insn_len;
frame[1] = csr->sel;
frame[2] = regs->eflags & ~X86_EFLAGS_RF;
/* We can't test hvmemul_ctxt->ctxt.sp_size: it may not be initialised. */
if ( hvmemul_ctxt->seg_reg[x86_seg_ss].attr.fields.db )
{
regs->esp -= 6;
pstk = regs->esp;
}
else
{
pstk = (uint16_t)(regs->esp - 6);
regs->esp &= ~0xffff;
regs->esp |= pstk;
}
pstk += hvmemul_get_seg_reg(x86_seg_ss, hvmemul_ctxt)->base;
(void)hvm_copy_to_guest_phys(pstk, frame, sizeof(frame));
csr->sel = cs_eip >> 16;
csr->base = (uint32_t)csr->sel << 4;
regs->eip = (uint16_t)cs_eip;
regs->eflags &= ~(X86_EFLAGS_TF | X86_EFLAGS_IF | X86_EFLAGS_RF);
/* Exception delivery clears STI and MOV-SS blocking. */
if ( hvmemul_ctxt->intr_shadow &
(VMX_INTR_SHADOW_STI|VMX_INTR_SHADOW_MOV_SS) )
{
hvmemul_ctxt->intr_shadow &=
~(VMX_INTR_SHADOW_STI|VMX_INTR_SHADOW_MOV_SS);
__vmwrite(GUEST_INTERRUPTIBILITY_INFO, hvmemul_ctxt->intr_shadow);
}
}
static void realmode_emulate_one(struct hvm_emulate_ctxt *hvmemul_ctxt)
{
struct vcpu *curr = current;
int rc;
perfc_incr(realmode_emulations);
rc = hvm_emulate_one(hvmemul_ctxt);
if ( rc == X86EMUL_UNHANDLEABLE )
{
gdprintk(XENLOG_ERR, "Failed to emulate insn.\n");
goto fail;
}
if ( rc == X86EMUL_EXCEPTION )
{
if ( !hvmemul_ctxt->exn_pending )
{
unsigned long intr_info;
__vmread(VM_ENTRY_INTR_INFO, &intr_info);
__vmwrite(VM_ENTRY_INTR_INFO, 0);
if ( !(intr_info & INTR_INFO_VALID_MASK) )
{
gdprintk(XENLOG_ERR, "Exception pending but no info.\n");
goto fail;
}
hvmemul_ctxt->exn_vector = (uint8_t)intr_info;
hvmemul_ctxt->exn_insn_len = 0;
}
if ( unlikely(curr->domain->debugger_attached) &&
((hvmemul_ctxt->exn_vector == TRAP_debug) ||
(hvmemul_ctxt->exn_vector == TRAP_int3)) )
{
domain_pause_for_debugger();
}
else if ( curr->arch.hvm_vcpu.guest_cr[0] & X86_CR0_PE )
{
gdprintk(XENLOG_ERR, "Exception %02x in protected mode.\n",
hvmemul_ctxt->exn_vector);
goto fail;
}
else
{
realmode_deliver_exception(
hvmemul_ctxt->exn_vector,
hvmemul_ctxt->exn_insn_len,
hvmemul_ctxt);
}
}
return;
fail:
gdprintk(XENLOG_ERR,
"Real-mode emulation failed @ %04x:%08lx: "
"%02x %02x %02x %02x %02x %02x\n",
hvmemul_get_seg_reg(x86_seg_cs, hvmemul_ctxt)->sel,
hvmemul_ctxt->insn_buf_eip,
hvmemul_ctxt->insn_buf[0], hvmemul_ctxt->insn_buf[1],
hvmemul_ctxt->insn_buf[2], hvmemul_ctxt->insn_buf[3],
hvmemul_ctxt->insn_buf[4], hvmemul_ctxt->insn_buf[5]);
domain_crash(curr->domain);
}
void vmx_realmode(struct cpu_user_regs *regs)
{
struct vcpu *curr = current;
struct hvm_emulate_ctxt hvmemul_ctxt;
struct segment_register *sreg;
struct hvm_vcpu_io *vio = &curr->arch.hvm_vcpu.hvm_io;
unsigned long intr_info;
unsigned int emulations = 0;
/* Get-and-clear VM_ENTRY_INTR_INFO. */
__vmread(VM_ENTRY_INTR_INFO, &intr_info);
if ( intr_info & INTR_INFO_VALID_MASK )
__vmwrite(VM_ENTRY_INTR_INFO, 0);
hvm_emulate_prepare(&hvmemul_ctxt, regs);
if ( vio->io_state == HVMIO_completed )
realmode_emulate_one(&hvmemul_ctxt);
/* Only deliver interrupts into emulated real mode. */
if ( !(curr->arch.hvm_vcpu.guest_cr[0] & X86_CR0_PE) &&
(intr_info & INTR_INFO_VALID_MASK) )
{
realmode_deliver_exception((uint8_t)intr_info, 0, &hvmemul_ctxt);
intr_info = 0;
}
curr->arch.hvm_vmx.vmx_emulate = 1;
while ( curr->arch.hvm_vmx.vmx_emulate &&
!softirq_pending(smp_processor_id()) &&
(vio->io_state == HVMIO_none) )
{
/*
* Check for pending interrupts only every 16 instructions, because
* hvm_local_events_need_delivery() is moderately expensive, and only
* in real mode, because we don't emulate protected-mode IDT vectoring.
*/
if ( unlikely(!(++emulations & 15)) &&
curr->arch.hvm_vmx.vmx_realmode &&
hvm_local_events_need_delivery(curr) )
break;
realmode_emulate_one(&hvmemul_ctxt);
/* Stop emulating unless our segment state is not safe */
if ( curr->arch.hvm_vmx.vmx_realmode )
curr->arch.hvm_vmx.vmx_emulate =
(curr->arch.hvm_vmx.vm86_segment_mask != 0);
else
curr->arch.hvm_vmx.vmx_emulate =
((hvmemul_ctxt.seg_reg[x86_seg_cs].sel & 3)
|| (hvmemul_ctxt.seg_reg[x86_seg_ss].sel & 3));
}
/* Need to emulate next time if we've started an IO operation */
if ( vio->io_state != HVMIO_none )
curr->arch.hvm_vmx.vmx_emulate = 1;
if ( !curr->arch.hvm_vmx.vmx_emulate && !curr->arch.hvm_vmx.vmx_realmode )
{
/*
* Cannot enter protected mode with bogus selector RPLs and DPLs.
* At this point CS.RPL == SS.RPL == CS.DPL == SS.DPL == 0. For
* DS, ES, FS and GS the most uninvasive trick is to set DPL == RPL.
*/
sreg = hvmemul_get_seg_reg(x86_seg_ds, &hvmemul_ctxt);
sreg->attr.fields.dpl = sreg->sel & 3;
sreg = hvmemul_get_seg_reg(x86_seg_es, &hvmemul_ctxt);
sreg->attr.fields.dpl = sreg->sel & 3;
sreg = hvmemul_get_seg_reg(x86_seg_fs, &hvmemul_ctxt);
sreg->attr.fields.dpl = sreg->sel & 3;
sreg = hvmemul_get_seg_reg(x86_seg_gs, &hvmemul_ctxt);
sreg->attr.fields.dpl = sreg->sel & 3;
hvmemul_ctxt.seg_reg_dirty |=
(1ul << x86_seg_ds) | (1ul << x86_seg_es) |
(1ul << x86_seg_fs) | (1ul << x86_seg_gs);
}
hvm_emulate_writeback(&hvmemul_ctxt);
/* Re-instate VM_ENTRY_INTR_INFO if we did not discharge it. */
if ( intr_info & INTR_INFO_VALID_MASK )
__vmwrite(VM_ENTRY_INTR_INFO, intr_info);
}
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