4bd611ca60
This adds support for SW breakpoints inserted by userspace. We do this by trapping all guest software debug exceptions to the hypervisor (MDCR_EL2.TDE). The exit handler sets an exit reason of KVM_EXIT_DEBUG with the kvm_debug_exit_arch structure holding the exception syndrome information. It will be up to userspace to extract the PC (via GET_ONE_REG) and determine if the debug event was for a breakpoint it inserted. If not userspace will need to re-inject the correct exception restart the hypervisor to deliver the debug exception to the guest. Any other guest software debug exception (e.g. single step or HW assisted breakpoints) will cause an error and the VM to be killed. This is addressed by later patches which add support for the other debug types. Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
84 lines
2.5 KiB
C
84 lines
2.5 KiB
C
/*
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* Debug and Guest Debug support
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*
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* Copyright (C) 2015 - Linaro Ltd
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* Author: Alex Bennée <alex.bennee@linaro.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <linux/kvm_host.h>
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#include <asm/kvm_arm.h>
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static DEFINE_PER_CPU(u32, mdcr_el2);
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/**
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* kvm_arm_init_debug - grab what we need for debug
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*
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* Currently the sole task of this function is to retrieve the initial
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* value of mdcr_el2 so we can preserve MDCR_EL2.HPMN which has
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* presumably been set-up by some knowledgeable bootcode.
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*
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* It is called once per-cpu during CPU hyp initialisation.
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*/
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void kvm_arm_init_debug(void)
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{
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__this_cpu_write(mdcr_el2, kvm_call_hyp(__kvm_get_mdcr_el2));
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}
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/**
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* kvm_arm_setup_debug - set up debug related stuff
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*
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* @vcpu: the vcpu pointer
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*
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* This is called before each entry into the hypervisor to setup any
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* debug related registers. Currently this just ensures we will trap
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* access to:
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* - Performance monitors (MDCR_EL2_TPM/MDCR_EL2_TPMCR)
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* - Debug ROM Address (MDCR_EL2_TDRA)
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* - OS related registers (MDCR_EL2_TDOSA)
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*
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* Additionally, KVM only traps guest accesses to the debug registers if
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* the guest is not actively using them (see the KVM_ARM64_DEBUG_DIRTY
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* flag on vcpu->arch.debug_flags). Since the guest must not interfere
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* with the hardware state when debugging the guest, we must ensure that
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* trapping is enabled whenever we are debugging the guest using the
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* debug registers.
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*/
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void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
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{
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bool trap_debug = !(vcpu->arch.debug_flags & KVM_ARM64_DEBUG_DIRTY);
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vcpu->arch.mdcr_el2 = __this_cpu_read(mdcr_el2) & MDCR_EL2_HPMN_MASK;
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vcpu->arch.mdcr_el2 |= (MDCR_EL2_TPM |
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MDCR_EL2_TPMCR |
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MDCR_EL2_TDRA |
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MDCR_EL2_TDOSA);
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/* Trap on access to debug registers? */
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if (trap_debug)
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vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA;
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/* Trap breakpoints? */
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if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP)
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vcpu->arch.mdcr_el2 |= MDCR_EL2_TDE;
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}
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void kvm_arm_clear_debug(struct kvm_vcpu *vcpu)
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{
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/* Nothing to do yet */
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}
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