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KVM: x86 emulator: Add IRET instruction 

Ths patch adds IRET instruction (opcode 0xcf).
Currently, only IRET in real mode is emulated. Protected mode support is to be added later if needed.

Signed-off-by: Mohammed Gamal <m.gamal005@gmail.com>
Reviewed-by: Avi Kivity <avi@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Mohammed Gamal 2010-07-28 12:38:40 +03:00 committed by Avi Kivity
parent 7a190667bb
commit 62bd430e6d
1 changed files with 81 additions and 0 deletions
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81
arch/x86/kvm/emulate.c
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@ -341,6 +341,9 @@ static u32 group2_table[] = {
#define EFLG_PF (1<<2)
#define EFLG_CF (1<<0)
#define EFLG_RESERVED_ZEROS_MASK 0xffc0802a
#define EFLG_RESERVED_ONE_MASK 2
/*
* Instruction emulation:
* Most instructions are emulated directly via a fragment of inline assembly
@ -1729,6 +1732,78 @@ static int emulate_popa(struct x86_emulate_ctxt *ctxt,
return rc;
}
static int emulate_iret_real(struct x86_emulate_ctxt *ctxt,
struct x86_emulate_ops *ops)
{
struct decode_cache *c = &ctxt->decode;
int rc = X86EMUL_CONTINUE;
unsigned long temp_eip = 0;
unsigned long temp_eflags = 0;
unsigned long cs = 0;
unsigned long mask = EFLG_CF | EFLG_PF | EFLG_AF | EFLG_ZF | EFLG_SF | EFLG_TF |
EFLG_IF | EFLG_DF | EFLG_OF | EFLG_IOPL | EFLG_NT | EFLG_RF |
EFLG_AC | EFLG_ID | (1 << 1); /* Last one is the reserved bit */
unsigned long vm86_mask = EFLG_VM | EFLG_VIF | EFLG_VIP;
/* TODO: Add stack limit check */
rc = emulate_pop(ctxt, ops, &temp_eip, c->op_bytes);
if (rc != X86EMUL_CONTINUE)
return rc;
if (temp_eip & ~0xffff) {
emulate_gp(ctxt, 0);
return X86EMUL_PROPAGATE_FAULT;
}
rc = emulate_pop(ctxt, ops, &cs, c->op_bytes);
if (rc != X86EMUL_CONTINUE)
return rc;
rc = emulate_pop(ctxt, ops, &temp_eflags, c->op_bytes);
if (rc != X86EMUL_CONTINUE)
return rc;
rc = load_segment_descriptor(ctxt, ops, (u16)cs, VCPU_SREG_CS);
if (rc != X86EMUL_CONTINUE)
return rc;
c->eip = temp_eip;
if (c->op_bytes == 4)
ctxt->eflags = ((temp_eflags & mask) | (ctxt->eflags & vm86_mask));
else if (c->op_bytes == 2) {
ctxt->eflags &= ~0xffff;
ctxt->eflags |= temp_eflags;
}
ctxt->eflags &= ~EFLG_RESERVED_ZEROS_MASK; /* Clear reserved zeros */
ctxt->eflags |= EFLG_RESERVED_ONE_MASK;
return rc;
}
static inline int emulate_iret(struct x86_emulate_ctxt *ctxt,
struct x86_emulate_ops* ops)
{
switch(ctxt->mode) {
case X86EMUL_MODE_REAL:
return emulate_iret_real(ctxt, ops);
case X86EMUL_MODE_VM86:
case X86EMUL_MODE_PROT16:
case X86EMUL_MODE_PROT32:
case X86EMUL_MODE_PROT64:
default:
/* iret from protected mode unimplemented yet */
return X86EMUL_UNHANDLEABLE;
}
}
static inline int emulate_grp1a(struct x86_emulate_ctxt *ctxt,
struct x86_emulate_ops *ops)
{
@ -2857,6 +2932,12 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
break;
case 0xcb: /* ret far */
rc = emulate_ret_far(ctxt, ops);
if (rc != X86EMUL_CONTINUE)
goto done;
break;
case 0xcf: /* iret */
rc = emulate_iret(ctxt, ops);
if (rc != X86EMUL_CONTINUE)
goto done;
break;