245 lines
7.3 KiB
C
245 lines
7.3 KiB
C
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/*
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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 <linux/hw_breakpoint.h>
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#include <asm/debug-monitors.h>
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#include <asm/kvm_asm.h>
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#include <asm/kvm_arm.h>
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#include <asm/kvm_emulate.h>
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#include "trace.h"
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/* These are the bits of MDSCR_EL1 we may manipulate */
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#define MDSCR_EL1_DEBUG_MASK (DBG_MDSCR_SS | \
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DBG_MDSCR_KDE | \
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DBG_MDSCR_MDE)
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static DEFINE_PER_CPU(u32, mdcr_el2);
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/**
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* save/restore_guest_debug_regs
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*
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* For some debug operations we need to tweak some guest registers. As
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* a result we need to save the state of those registers before we
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* make those modifications.
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*
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* Guest access to MDSCR_EL1 is trapped by the hypervisor and handled
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* after we have restored the preserved value to the main context.
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*/
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static void save_guest_debug_regs(struct kvm_vcpu *vcpu)
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{
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vcpu->arch.guest_debug_preserved.mdscr_el1 = vcpu_sys_reg(vcpu, MDSCR_EL1);
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trace_kvm_arm_set_dreg32("Saved MDSCR_EL1",
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vcpu->arch.guest_debug_preserved.mdscr_el1);
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}
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static void restore_guest_debug_regs(struct kvm_vcpu *vcpu)
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{
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vcpu_sys_reg(vcpu, MDSCR_EL1) = vcpu->arch.guest_debug_preserved.mdscr_el1;
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trace_kvm_arm_set_dreg32("Restored MDSCR_EL1",
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vcpu_sys_reg(vcpu, MDSCR_EL1));
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}
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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_reset_debug_ptr - reset the debug ptr to point to the vcpu state
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*/
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void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu)
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{
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vcpu->arch.debug_ptr = &vcpu->arch.vcpu_debug_state;
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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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* - Statistical profiler (MDCR_EL2_TPMS/MDCR_EL2_E2PB)
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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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trace_kvm_arm_setup_debug(vcpu, vcpu->guest_debug);
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/*
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* This also clears MDCR_EL2_E2PB_MASK to disable guest access
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* to the profiling buffer.
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*/
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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_TPMS |
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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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/* Is Guest debugging in effect? */
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if (vcpu->guest_debug) {
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/* Route all software debug exceptions to EL2 */
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vcpu->arch.mdcr_el2 |= MDCR_EL2_TDE;
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/* Save guest debug state */
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save_guest_debug_regs(vcpu);
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/*
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* Single Step (ARM ARM D2.12.3 The software step state
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* machine)
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*
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* If we are doing Single Step we need to manipulate
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* the guest's MDSCR_EL1.SS and PSTATE.SS. Once the
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* step has occurred the hypervisor will trap the
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* debug exception and we return to userspace.
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*
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* If the guest attempts to single step its userspace
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* we would have to deal with a trapped exception
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* while in the guest kernel. Because this would be
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* hard to unwind we suppress the guest's ability to
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* do so by masking MDSCR_EL.SS.
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*
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* This confuses guest debuggers which use
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* single-step behind the scenes but everything
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* returns to normal once the host is no longer
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* debugging the system.
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*/
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if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
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*vcpu_cpsr(vcpu) |= DBG_SPSR_SS;
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vcpu_sys_reg(vcpu, MDSCR_EL1) |= DBG_MDSCR_SS;
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} else {
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vcpu_sys_reg(vcpu, MDSCR_EL1) &= ~DBG_MDSCR_SS;
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}
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trace_kvm_arm_set_dreg32("SPSR_EL2", *vcpu_cpsr(vcpu));
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/*
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* HW Breakpoints and watchpoints
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*
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* We simply switch the debug_ptr to point to our new
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* external_debug_state which has been populated by the
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* debug ioctl. The existing KVM_ARM64_DEBUG_DIRTY
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* mechanism ensures the registers are updated on the
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* world switch.
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*/
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if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) {
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/* Enable breakpoints/watchpoints */
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vcpu_sys_reg(vcpu, MDSCR_EL1) |= DBG_MDSCR_MDE;
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vcpu->arch.debug_ptr = &vcpu->arch.external_debug_state;
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vcpu->arch.debug_flags |= KVM_ARM64_DEBUG_DIRTY;
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trap_debug = true;
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trace_kvm_arm_set_regset("BKPTS", get_num_brps(),
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&vcpu->arch.debug_ptr->dbg_bcr[0],
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&vcpu->arch.debug_ptr->dbg_bvr[0]);
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trace_kvm_arm_set_regset("WAPTS", get_num_wrps(),
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&vcpu->arch.debug_ptr->dbg_wcr[0],
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&vcpu->arch.debug_ptr->dbg_wvr[0]);
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}
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}
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BUG_ON(!vcpu->guest_debug &&
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vcpu->arch.debug_ptr != &vcpu->arch.vcpu_debug_state);
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/* Trap debug register access */
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if (trap_debug)
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vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA;
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trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.mdcr_el2);
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trace_kvm_arm_set_dreg32("MDSCR_EL1", vcpu_sys_reg(vcpu, MDSCR_EL1));
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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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trace_kvm_arm_clear_debug(vcpu->guest_debug);
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if (vcpu->guest_debug) {
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restore_guest_debug_regs(vcpu);
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/*
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* If we were using HW debug we need to restore the
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* debug_ptr to the guest debug state.
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*/
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if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) {
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kvm_arm_reset_debug_ptr(vcpu);
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trace_kvm_arm_set_regset("BKPTS", get_num_brps(),
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&vcpu->arch.debug_ptr->dbg_bcr[0],
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&vcpu->arch.debug_ptr->dbg_bvr[0]);
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trace_kvm_arm_set_regset("WAPTS", get_num_wrps(),
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&vcpu->arch.debug_ptr->dbg_wcr[0],
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&vcpu->arch.debug_ptr->dbg_wvr[0]);
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}
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}
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}
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/*
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* After successfully emulating an instruction, we might want to
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* return to user space with a KVM_EXIT_DEBUG. We can only do this
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* once the emulation is complete, though, so for userspace emulations
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* we have to wait until we have re-entered KVM before calling this
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* helper.
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*
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* Return true (and set exit_reason) to return to userspace or false
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* if no further action is required.
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*/
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bool kvm_arm_handle_step_debug(struct kvm_vcpu *vcpu, struct kvm_run *run)
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{
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if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
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run->exit_reason = KVM_EXIT_DEBUG;
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run->debug.arch.hsr = ESR_ELx_EC_SOFTSTP_LOW << ESR_ELx_EC_SHIFT;
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return true;
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}
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return false;
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}
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