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Commit 82b32774 authored by Nadav Amit's avatar Nadav Amit Committed by Paolo Bonzini
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KVM: x86: Breakpoints do not consider CS.base 



x86 debug registers hold a linear address. Therefore, breakpoints detection
should consider CS.base, and check whether instruction linear address equals
(CS.base + RIP). This patch introduces a function to evaluate RIP linear
address and uses it for breakpoints detection.

Signed-off-by: default avatarNadav Amit <namit@cs.technion.ac.il>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 7305eb5d

arch/x86/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -1067,6 +1067,7 @@ void kvm_arch_mmu_notifier_invalidate_page(struct kvm *kvm, 
void kvm_define_shared_msr(unsigned index, u32 msr);

int kvm_set_shared_msr(unsigned index, u64 val, u64 mask);



unsigned long kvm_get_linear_rip(struct kvm_vcpu *vcpu);

bool kvm_is_linear_rip(struct kvm_vcpu *vcpu, unsigned long linear_rip);



void kvm_arch_async_page_not_present(struct kvm_vcpu *vcpu,

arch/x86/kvm/vmx.c

+1 −3
Original line number Diff line number Diff line
@@ -5118,9 +5118,7 @@ static int handle_dr(struct kvm_vcpu *vcpu) 
		if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP) {

			vcpu->run->debug.arch.dr6 = vcpu->arch.dr6;

			vcpu->run->debug.arch.dr7 = dr7;

			vcpu->run->debug.arch.pc =

				vmcs_readl(GUEST_CS_BASE) +

				vmcs_readl(GUEST_RIP);

			vcpu->run->debug.arch.pc = kvm_get_linear_rip(vcpu);

			vcpu->run->debug.arch.exception = DB_VECTOR;

			vcpu->run->exit_reason = KVM_EXIT_DEBUG;

			return 0;

arch/x86/kvm/x86.c

+16 −13
Original line number Diff line number Diff line
@@ -5207,21 +5207,17 @@ static void kvm_vcpu_check_singlestep(struct kvm_vcpu *vcpu, unsigned long rflag 


static bool kvm_vcpu_check_breakpoint(struct kvm_vcpu *vcpu, int *r)

{

	struct kvm_run *kvm_run = vcpu->run;

	unsigned long eip = vcpu->arch.emulate_ctxt.eip;

	u32 dr6 = 0;



	if (unlikely(vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP) &&

	    (vcpu->arch.guest_debug_dr7 & DR7_BP_EN_MASK)) {

		dr6 = kvm_vcpu_check_hw_bp(eip, 0,

		struct kvm_run *kvm_run = vcpu->run;

		unsigned long eip = kvm_get_linear_rip(vcpu);

		u32 dr6 = kvm_vcpu_check_hw_bp(eip, 0,

					   vcpu->arch.guest_debug_dr7,

					   vcpu->arch.eff_db);



		if (dr6 != 0) {

			kvm_run->debug.arch.dr6 = dr6 | DR6_FIXED_1 | DR6_RTM;

			kvm_run->debug.arch.pc = kvm_rip_read(vcpu) +

				get_segment_base(vcpu, VCPU_SREG_CS);



			kvm_run->debug.arch.pc = eip;

			kvm_run->debug.arch.exception = DB_VECTOR;

			kvm_run->exit_reason = KVM_EXIT_DEBUG;

			*r = EMULATE_USER_EXIT;
@@ -5231,7 +5227,8 @@ static bool kvm_vcpu_check_breakpoint(struct kvm_vcpu *vcpu, int *r) 


	if (unlikely(vcpu->arch.dr7 & DR7_BP_EN_MASK) &&

	    !(kvm_get_rflags(vcpu) & X86_EFLAGS_RF)) {

		dr6 = kvm_vcpu_check_hw_bp(eip, 0,

		unsigned long eip = kvm_get_linear_rip(vcpu);

		u32 dr6 = kvm_vcpu_check_hw_bp(eip, 0,

					   vcpu->arch.dr7,

					   vcpu->arch.db);
@@ -7538,12 +7535,18 @@ int kvm_arch_interrupt_allowed(struct kvm_vcpu *vcpu) 
	return kvm_x86_ops->interrupt_allowed(vcpu);

}



bool kvm_is_linear_rip(struct kvm_vcpu *vcpu, unsigned long linear_rip)

unsigned long kvm_get_linear_rip(struct kvm_vcpu *vcpu)

{

	unsigned long current_rip = kvm_rip_read(vcpu) +

		get_segment_base(vcpu, VCPU_SREG_CS);

	if (is_64_bit_mode(vcpu))

		return kvm_rip_read(vcpu);

	return (u32)(get_segment_base(vcpu, VCPU_SREG_CS) +

		     kvm_rip_read(vcpu));

}

EXPORT_SYMBOL_GPL(kvm_get_linear_rip);



	return current_rip == linear_rip;

bool kvm_is_linear_rip(struct kvm_vcpu *vcpu, unsigned long linear_rip)

{

	return kvm_get_linear_rip(vcpu) == linear_rip;

}

EXPORT_SYMBOL_GPL(kvm_is_linear_rip);