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KVM: x86: JMP/CALL using call- or task-gate causes exception

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The KVM emulator does not emulate JMP and CALL that target a call gate or a
task gate.  This patch does not try to implement these scenario as they are
presumably rare; yet it returns X86EMUL_UNHANDLEABLE error in such cases
instead of generating an exception.

Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Nadav Amit 2014-12-25 02:52:19 +02:00 committed by Paolo Bonzini
parent 16bebefe29
commit 3dc4bc4f6b
1 changed files with 34 additions and 20 deletions
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54
arch/x86/kvm/emulate.c
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@ -263,6 +263,13 @@ struct instr_dual {
#define EFLG_RESERVED_ZEROS_MASK 0xffc0802a
#define EFLG_RESERVED_ONE_MASK 2
enum x86_transfer_type {
X86_TRANSFER_NONE,
X86_TRANSFER_CALL_JMP,
X86_TRANSFER_RET,
X86_TRANSFER_TASK_SWITCH,
};
static ulong reg_read(struct x86_emulate_ctxt *ctxt, unsigned nr)
{
if (!(ctxt->regs_valid & (1 << nr))) {
@ -1472,7 +1479,7 @@ static int write_segment_descriptor(struct x86_emulate_ctxt *ctxt,
/* Does not support long mode */
static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt,
u16 selector, int seg, u8 cpl,
bool in_task_switch,
enum x86_transfer_type transfer,
struct desc_struct *desc)
{
struct desc_struct seg_desc, old_desc;
@ -1526,11 +1533,15 @@ static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt,
return ret;
err_code = selector & 0xfffc;
err_vec = in_task_switch ? TS_VECTOR : GP_VECTOR;
err_vec = (transfer == X86_TRANSFER_TASK_SWITCH) ? TS_VECTOR :
GP_VECTOR;
/* can't load system descriptor into segment selector */
if (seg <= VCPU_SREG_GS && !seg_desc.s)
if (seg <= VCPU_SREG_GS && !seg_desc.s) {
if (transfer == X86_TRANSFER_CALL_JMP)
return X86EMUL_UNHANDLEABLE;
goto exception;
}
if (!seg_desc.p) {
err_vec = (seg == VCPU_SREG_SS) ? SS_VECTOR : NP_VECTOR;
@ -1628,7 +1639,8 @@ static int load_segment_descriptor(struct x86_emulate_ctxt *ctxt,
u16 selector, int seg)
{
u8 cpl = ctxt->ops->cpl(ctxt);
return __load_segment_descriptor(ctxt, selector, seg, cpl, false, NULL);
return __load_segment_descriptor(ctxt, selector, seg, cpl,
X86_TRANSFER_NONE, NULL);
}
static void write_register_operand(struct operand *op)
@ -2040,7 +2052,8 @@ static int em_jmp_far(struct x86_emulate_ctxt *ctxt)
memcpy(&sel, ctxt->src.valptr + ctxt->op_bytes, 2);
rc = __load_segment_descriptor(ctxt, sel, VCPU_SREG_CS, cpl, false,
rc = __load_segment_descriptor(ctxt, sel, VCPU_SREG_CS, cpl,
X86_TRANSFER_CALL_JMP,
&new_desc);
if (rc != X86EMUL_CONTINUE)
return rc;
@ -2129,7 +2142,8 @@ static int em_ret_far(struct x86_emulate_ctxt *ctxt)
/* Outer-privilege level return is not implemented */
if (ctxt->mode >= X86EMUL_MODE_PROT16 && (cs & 3) > cpl)
return X86EMUL_UNHANDLEABLE;
rc = __load_segment_descriptor(ctxt, (u16)cs, VCPU_SREG_CS, cpl, false,
rc = __load_segment_descriptor(ctxt, (u16)cs, VCPU_SREG_CS, cpl,
X86_TRANSFER_RET,
&new_desc);
if (rc != X86EMUL_CONTINUE)
return rc;
@ -2566,23 +2580,23 @@ static int load_state_from_tss16(struct x86_emulate_ctxt *ctxt,
* it is handled in a context of new task
*/
ret = __load_segment_descriptor(ctxt, tss->ldt, VCPU_SREG_LDTR, cpl,
true, NULL);
X86_TRANSFER_TASK_SWITCH, NULL);
if (ret != X86EMUL_CONTINUE)
return ret;
ret = __load_segment_descriptor(ctxt, tss->es, VCPU_SREG_ES, cpl,
true, NULL);
X86_TRANSFER_TASK_SWITCH, NULL);
if (ret != X86EMUL_CONTINUE)
return ret;
ret = __load_segment_descriptor(ctxt, tss->cs, VCPU_SREG_CS, cpl,
true, NULL);
X86_TRANSFER_TASK_SWITCH, NULL);
if (ret != X86EMUL_CONTINUE)
return ret;
ret = __load_segment_descriptor(ctxt, tss->ss, VCPU_SREG_SS, cpl,
true, NULL);
X86_TRANSFER_TASK_SWITCH, NULL);
if (ret != X86EMUL_CONTINUE)
return ret;
ret = __load_segment_descriptor(ctxt, tss->ds, VCPU_SREG_DS, cpl,
true, NULL);
X86_TRANSFER_TASK_SWITCH, NULL);
if (ret != X86EMUL_CONTINUE)
return ret;
@ -2704,31 +2718,31 @@ static int load_state_from_tss32(struct x86_emulate_ctxt *ctxt,
* it is handled in a context of new task
*/
ret = __load_segment_descriptor(ctxt, tss->ldt_selector, VCPU_SREG_LDTR,
cpl, true, NULL);
cpl, X86_TRANSFER_TASK_SWITCH, NULL);
if (ret != X86EMUL_CONTINUE)
return ret;
ret = __load_segment_descriptor(ctxt, tss->es, VCPU_SREG_ES, cpl,
true, NULL);
X86_TRANSFER_TASK_SWITCH, NULL);
if (ret != X86EMUL_CONTINUE)
return ret;
ret = __load_segment_descriptor(ctxt, tss->cs, VCPU_SREG_CS, cpl,
true, NULL);
X86_TRANSFER_TASK_SWITCH, NULL);
if (ret != X86EMUL_CONTINUE)
return ret;
ret = __load_segment_descriptor(ctxt, tss->ss, VCPU_SREG_SS, cpl,
true, NULL);
X86_TRANSFER_TASK_SWITCH, NULL);
if (ret != X86EMUL_CONTINUE)
return ret;
ret = __load_segment_descriptor(ctxt, tss->ds, VCPU_SREG_DS, cpl,
true, NULL);
X86_TRANSFER_TASK_SWITCH, NULL);
if (ret != X86EMUL_CONTINUE)
return ret;
ret = __load_segment_descriptor(ctxt, tss->fs, VCPU_SREG_FS, cpl,
true, NULL);
X86_TRANSFER_TASK_SWITCH, NULL);
if (ret != X86EMUL_CONTINUE)
return ret;
ret = __load_segment_descriptor(ctxt, tss->gs, VCPU_SREG_GS, cpl,
true, NULL);
X86_TRANSFER_TASK_SWITCH, NULL);
if (ret != X86EMUL_CONTINUE)
return ret;
@ -3010,8 +3024,8 @@ static int em_call_far(struct x86_emulate_ctxt *ctxt)
ops->get_segment(ctxt, &old_cs, &old_desc, NULL, VCPU_SREG_CS);
memcpy(&sel, ctxt->src.valptr + ctxt->op_bytes, 2);
rc = __load_segment_descriptor(ctxt, sel, VCPU_SREG_CS, cpl, false,
&new_desc);
rc = __load_segment_descriptor(ctxt, sel, VCPU_SREG_CS, cpl,
X86_TRANSFER_CALL_JMP, &new_desc);
if (rc != X86EMUL_CONTINUE)
return X86EMUL_CONTINUE;