From 3dc4bc4f6b9265bd05dda007b07eac5a17da0562 Mon Sep 17 00:00:00 2001 From: Nadav Amit Date: Thu, 25 Dec 2014 02:52:19 +0200 Subject: [PATCH] KVM: x86: JMP/CALL using call- or task-gate causes exception 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 Signed-off-by: Paolo Bonzini --- arch/x86/kvm/emulate.c | 54 +++++++++++++++++++++++++++++++------------------- 1 file changed, 34 insertions(+), 20 deletions(-) diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index fff1188..1fec3ed 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -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; -- 2.7.4