| // SPDX-License-Identifier: GPL-2.0-only |
| /* |
| * Debug and Guest Debug support |
| * |
| * Copyright (C) 2015 - Linaro Ltd |
| * Author: Alex Bennée <alex.bennee@linaro.org> |
| */ |
| |
| #include <linux/kvm_host.h> |
| #include <linux/hw_breakpoint.h> |
| |
| #include <asm/debug-monitors.h> |
| #include <asm/kvm_asm.h> |
| #include <asm/kvm_arm.h> |
| #include <asm/kvm_emulate.h> |
| |
| #include "trace.h" |
| |
| /* These are the bits of MDSCR_EL1 we may manipulate */ |
| #define MDSCR_EL1_DEBUG_MASK (DBG_MDSCR_SS | \ |
| DBG_MDSCR_KDE | \ |
| DBG_MDSCR_MDE) |
| |
| static DEFINE_PER_CPU(u32, mdcr_el2); |
| |
| /** |
| * save/restore_guest_debug_regs |
| * |
| * For some debug operations we need to tweak some guest registers. As |
| * a result we need to save the state of those registers before we |
| * make those modifications. |
| * |
| * Guest access to MDSCR_EL1 is trapped by the hypervisor and handled |
| * after we have restored the preserved value to the main context. |
| */ |
| static void save_guest_debug_regs(struct kvm_vcpu *vcpu) |
| { |
| u64 val = vcpu_read_sys_reg(vcpu, MDSCR_EL1); |
| |
| vcpu->arch.guest_debug_preserved.mdscr_el1 = val; |
| |
| trace_kvm_arm_set_dreg32("Saved MDSCR_EL1", |
| vcpu->arch.guest_debug_preserved.mdscr_el1); |
| } |
| |
| static void restore_guest_debug_regs(struct kvm_vcpu *vcpu) |
| { |
| u64 val = vcpu->arch.guest_debug_preserved.mdscr_el1; |
| |
| vcpu_write_sys_reg(vcpu, val, MDSCR_EL1); |
| |
| trace_kvm_arm_set_dreg32("Restored MDSCR_EL1", |
| vcpu_read_sys_reg(vcpu, MDSCR_EL1)); |
| } |
| |
| /** |
| * kvm_arm_init_debug - grab what we need for debug |
| * |
| * Currently the sole task of this function is to retrieve the initial |
| * value of mdcr_el2 so we can preserve MDCR_EL2.HPMN which has |
| * presumably been set-up by some knowledgeable bootcode. |
| * |
| * It is called once per-cpu during CPU hyp initialisation. |
| */ |
| |
| void kvm_arm_init_debug(void) |
| { |
| __this_cpu_write(mdcr_el2, kvm_call_hyp_ret(__kvm_get_mdcr_el2)); |
| } |
| |
| /** |
| * kvm_arm_reset_debug_ptr - reset the debug ptr to point to the vcpu state |
| */ |
| |
| void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu) |
| { |
| vcpu->arch.debug_ptr = &vcpu->arch.vcpu_debug_state; |
| } |
| |
| /** |
| * kvm_arm_setup_debug - set up debug related stuff |
| * |
| * @vcpu: the vcpu pointer |
| * |
| * This is called before each entry into the hypervisor to setup any |
| * debug related registers. Currently this just ensures we will trap |
| * access to: |
| * - Performance monitors (MDCR_EL2_TPM/MDCR_EL2_TPMCR) |
| * - Debug ROM Address (MDCR_EL2_TDRA) |
| * - OS related registers (MDCR_EL2_TDOSA) |
| * - Statistical profiler (MDCR_EL2_TPMS/MDCR_EL2_E2PB) |
| * - Self-hosted Trace Filter controls (MDCR_EL2_TTRF) |
| * |
| * Additionally, KVM only traps guest accesses to the debug registers if |
| * the guest is not actively using them (see the KVM_ARM64_DEBUG_DIRTY |
| * flag on vcpu->arch.flags). Since the guest must not interfere |
| * with the hardware state when debugging the guest, we must ensure that |
| * trapping is enabled whenever we are debugging the guest using the |
| * debug registers. |
| */ |
| |
| void kvm_arm_setup_debug(struct kvm_vcpu *vcpu) |
| { |
| bool trap_debug = !(vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY); |
| unsigned long mdscr, orig_mdcr_el2 = vcpu->arch.mdcr_el2; |
| |
| trace_kvm_arm_setup_debug(vcpu, vcpu->guest_debug); |
| |
| /* |
| * This also clears MDCR_EL2_E2PB_MASK to disable guest access |
| * to the profiling buffer. |
| */ |
| vcpu->arch.mdcr_el2 = __this_cpu_read(mdcr_el2) & MDCR_EL2_HPMN_MASK; |
| vcpu->arch.mdcr_el2 |= (MDCR_EL2_TPM | |
| MDCR_EL2_TPMS | |
| MDCR_EL2_TTRF | |
| MDCR_EL2_TPMCR | |
| MDCR_EL2_TDRA | |
| MDCR_EL2_TDOSA); |
| |
| /* Is Guest debugging in effect? */ |
| if (vcpu->guest_debug) { |
| /* Route all software debug exceptions to EL2 */ |
| vcpu->arch.mdcr_el2 |= MDCR_EL2_TDE; |
| |
| /* Save guest debug state */ |
| save_guest_debug_regs(vcpu); |
| |
| /* |
| * Single Step (ARM ARM D2.12.3 The software step state |
| * machine) |
| * |
| * If we are doing Single Step we need to manipulate |
| * the guest's MDSCR_EL1.SS and PSTATE.SS. Once the |
| * step has occurred the hypervisor will trap the |
| * debug exception and we return to userspace. |
| * |
| * If the guest attempts to single step its userspace |
| * we would have to deal with a trapped exception |
| * while in the guest kernel. Because this would be |
| * hard to unwind we suppress the guest's ability to |
| * do so by masking MDSCR_EL.SS. |
| * |
| * This confuses guest debuggers which use |
| * single-step behind the scenes but everything |
| * returns to normal once the host is no longer |
| * debugging the system. |
| */ |
| if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) { |
| *vcpu_cpsr(vcpu) |= DBG_SPSR_SS; |
| mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1); |
| mdscr |= DBG_MDSCR_SS; |
| vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1); |
| } else { |
| mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1); |
| mdscr &= ~DBG_MDSCR_SS; |
| vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1); |
| } |
| |
| trace_kvm_arm_set_dreg32("SPSR_EL2", *vcpu_cpsr(vcpu)); |
| |
| /* |
| * HW Breakpoints and watchpoints |
| * |
| * We simply switch the debug_ptr to point to our new |
| * external_debug_state which has been populated by the |
| * debug ioctl. The existing KVM_ARM64_DEBUG_DIRTY |
| * mechanism ensures the registers are updated on the |
| * world switch. |
| */ |
| if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) { |
| /* Enable breakpoints/watchpoints */ |
| mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1); |
| mdscr |= DBG_MDSCR_MDE; |
| vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1); |
| |
| vcpu->arch.debug_ptr = &vcpu->arch.external_debug_state; |
| vcpu->arch.flags |= KVM_ARM64_DEBUG_DIRTY; |
| trap_debug = true; |
| |
| trace_kvm_arm_set_regset("BKPTS", get_num_brps(), |
| &vcpu->arch.debug_ptr->dbg_bcr[0], |
| &vcpu->arch.debug_ptr->dbg_bvr[0]); |
| |
| trace_kvm_arm_set_regset("WAPTS", get_num_wrps(), |
| &vcpu->arch.debug_ptr->dbg_wcr[0], |
| &vcpu->arch.debug_ptr->dbg_wvr[0]); |
| } |
| } |
| |
| BUG_ON(!vcpu->guest_debug && |
| vcpu->arch.debug_ptr != &vcpu->arch.vcpu_debug_state); |
| |
| /* Trap debug register access */ |
| if (trap_debug) |
| vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA; |
| |
| /* If KDE or MDE are set, perform a full save/restore cycle. */ |
| if (vcpu_read_sys_reg(vcpu, MDSCR_EL1) & (DBG_MDSCR_KDE | DBG_MDSCR_MDE)) |
| vcpu->arch.flags |= KVM_ARM64_DEBUG_DIRTY; |
| |
| /* Write mdcr_el2 changes since vcpu_load on VHE systems */ |
| if (has_vhe() && orig_mdcr_el2 != vcpu->arch.mdcr_el2) |
| write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2); |
| |
| trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.mdcr_el2); |
| trace_kvm_arm_set_dreg32("MDSCR_EL1", vcpu_read_sys_reg(vcpu, MDSCR_EL1)); |
| } |
| |
| void kvm_arm_clear_debug(struct kvm_vcpu *vcpu) |
| { |
| trace_kvm_arm_clear_debug(vcpu->guest_debug); |
| |
| if (vcpu->guest_debug) { |
| restore_guest_debug_regs(vcpu); |
| |
| /* |
| * If we were using HW debug we need to restore the |
| * debug_ptr to the guest debug state. |
| */ |
| if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) { |
| kvm_arm_reset_debug_ptr(vcpu); |
| |
| trace_kvm_arm_set_regset("BKPTS", get_num_brps(), |
| &vcpu->arch.debug_ptr->dbg_bcr[0], |
| &vcpu->arch.debug_ptr->dbg_bvr[0]); |
| |
| trace_kvm_arm_set_regset("WAPTS", get_num_wrps(), |
| &vcpu->arch.debug_ptr->dbg_wcr[0], |
| &vcpu->arch.debug_ptr->dbg_wvr[0]); |
| } |
| } |
| } |