1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Debug and Guest Debug support 4 * 5 * Copyright (C) 2015 - Linaro Ltd 6 * Author: Alex Bennée <alex.bennee@linaro.org> 7 */ 8 9 #include <linux/kvm_host.h> 10 #include <linux/hw_breakpoint.h> 11 12 #include <asm/debug-monitors.h> 13 #include <asm/kvm_asm.h> 14 #include <asm/kvm_arm.h> 15 #include <asm/kvm_emulate.h> 16 17 #include "trace.h" 18 19 /* These are the bits of MDSCR_EL1 we may manipulate */ 20 #define MDSCR_EL1_DEBUG_MASK (DBG_MDSCR_SS | \ 21 DBG_MDSCR_KDE | \ 22 DBG_MDSCR_MDE) 23 24 static DEFINE_PER_CPU(u32, mdcr_el2); 25 26 /** 27 * save/restore_guest_debug_regs 28 * 29 * For some debug operations we need to tweak some guest registers. As 30 * a result we need to save the state of those registers before we 31 * make those modifications. 32 * 33 * Guest access to MDSCR_EL1 is trapped by the hypervisor and handled 34 * after we have restored the preserved value to the main context. 35 */ 36 static void save_guest_debug_regs(struct kvm_vcpu *vcpu) 37 { 38 u64 val = vcpu_read_sys_reg(vcpu, MDSCR_EL1); 39 40 vcpu->arch.guest_debug_preserved.mdscr_el1 = val; 41 42 trace_kvm_arm_set_dreg32("Saved MDSCR_EL1", 43 vcpu->arch.guest_debug_preserved.mdscr_el1); 44 } 45 46 static void restore_guest_debug_regs(struct kvm_vcpu *vcpu) 47 { 48 u64 val = vcpu->arch.guest_debug_preserved.mdscr_el1; 49 50 vcpu_write_sys_reg(vcpu, val, MDSCR_EL1); 51 52 trace_kvm_arm_set_dreg32("Restored MDSCR_EL1", 53 vcpu_read_sys_reg(vcpu, MDSCR_EL1)); 54 } 55 56 /** 57 * kvm_arm_init_debug - grab what we need for debug 58 * 59 * Currently the sole task of this function is to retrieve the initial 60 * value of mdcr_el2 so we can preserve MDCR_EL2.HPMN which has 61 * presumably been set-up by some knowledgeable bootcode. 62 * 63 * It is called once per-cpu during CPU hyp initialisation. 64 */ 65 66 void kvm_arm_init_debug(void) 67 { 68 __this_cpu_write(mdcr_el2, kvm_call_hyp_ret(__kvm_get_mdcr_el2)); 69 } 70 71 /** 72 * kvm_arm_reset_debug_ptr - reset the debug ptr to point to the vcpu state 73 */ 74 75 void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu) 76 { 77 vcpu->arch.debug_ptr = &vcpu->arch.vcpu_debug_state; 78 } 79 80 /** 81 * kvm_arm_setup_debug - set up debug related stuff 82 * 83 * @vcpu: the vcpu pointer 84 * 85 * This is called before each entry into the hypervisor to setup any 86 * debug related registers. Currently this just ensures we will trap 87 * access to: 88 * - Performance monitors (MDCR_EL2_TPM/MDCR_EL2_TPMCR) 89 * - Debug ROM Address (MDCR_EL2_TDRA) 90 * - OS related registers (MDCR_EL2_TDOSA) 91 * - Statistical profiler (MDCR_EL2_TPMS/MDCR_EL2_E2PB) 92 * 93 * Additionally, KVM only traps guest accesses to the debug registers if 94 * the guest is not actively using them (see the KVM_ARM64_DEBUG_DIRTY 95 * flag on vcpu->arch.flags). Since the guest must not interfere 96 * with the hardware state when debugging the guest, we must ensure that 97 * trapping is enabled whenever we are debugging the guest using the 98 * debug registers. 99 */ 100 101 void kvm_arm_setup_debug(struct kvm_vcpu *vcpu) 102 { 103 bool trap_debug = !(vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY); 104 unsigned long mdscr, orig_mdcr_el2 = vcpu->arch.mdcr_el2; 105 106 trace_kvm_arm_setup_debug(vcpu, vcpu->guest_debug); 107 108 /* 109 * This also clears MDCR_EL2_E2PB_MASK to disable guest access 110 * to the profiling buffer. 111 */ 112 vcpu->arch.mdcr_el2 = __this_cpu_read(mdcr_el2) & MDCR_EL2_HPMN_MASK; 113 vcpu->arch.mdcr_el2 |= (MDCR_EL2_TPM | 114 MDCR_EL2_TPMS | 115 MDCR_EL2_TPMCR | 116 MDCR_EL2_TDRA | 117 MDCR_EL2_TDOSA); 118 119 /* Is Guest debugging in effect? */ 120 if (vcpu->guest_debug) { 121 /* Route all software debug exceptions to EL2 */ 122 vcpu->arch.mdcr_el2 |= MDCR_EL2_TDE; 123 124 /* Save guest debug state */ 125 save_guest_debug_regs(vcpu); 126 127 /* 128 * Single Step (ARM ARM D2.12.3 The software step state 129 * machine) 130 * 131 * If we are doing Single Step we need to manipulate 132 * the guest's MDSCR_EL1.SS and PSTATE.SS. Once the 133 * step has occurred the hypervisor will trap the 134 * debug exception and we return to userspace. 135 * 136 * If the guest attempts to single step its userspace 137 * we would have to deal with a trapped exception 138 * while in the guest kernel. Because this would be 139 * hard to unwind we suppress the guest's ability to 140 * do so by masking MDSCR_EL.SS. 141 * 142 * This confuses guest debuggers which use 143 * single-step behind the scenes but everything 144 * returns to normal once the host is no longer 145 * debugging the system. 146 */ 147 if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) { 148 *vcpu_cpsr(vcpu) |= DBG_SPSR_SS; 149 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1); 150 mdscr |= DBG_MDSCR_SS; 151 vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1); 152 } else { 153 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1); 154 mdscr &= ~DBG_MDSCR_SS; 155 vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1); 156 } 157 158 trace_kvm_arm_set_dreg32("SPSR_EL2", *vcpu_cpsr(vcpu)); 159 160 /* 161 * HW Breakpoints and watchpoints 162 * 163 * We simply switch the debug_ptr to point to our new 164 * external_debug_state which has been populated by the 165 * debug ioctl. The existing KVM_ARM64_DEBUG_DIRTY 166 * mechanism ensures the registers are updated on the 167 * world switch. 168 */ 169 if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) { 170 /* Enable breakpoints/watchpoints */ 171 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1); 172 mdscr |= DBG_MDSCR_MDE; 173 vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1); 174 175 vcpu->arch.debug_ptr = &vcpu->arch.external_debug_state; 176 vcpu->arch.flags |= KVM_ARM64_DEBUG_DIRTY; 177 trap_debug = true; 178 179 trace_kvm_arm_set_regset("BKPTS", get_num_brps(), 180 &vcpu->arch.debug_ptr->dbg_bcr[0], 181 &vcpu->arch.debug_ptr->dbg_bvr[0]); 182 183 trace_kvm_arm_set_regset("WAPTS", get_num_wrps(), 184 &vcpu->arch.debug_ptr->dbg_wcr[0], 185 &vcpu->arch.debug_ptr->dbg_wvr[0]); 186 } 187 } 188 189 BUG_ON(!vcpu->guest_debug && 190 vcpu->arch.debug_ptr != &vcpu->arch.vcpu_debug_state); 191 192 /* Trap debug register access */ 193 if (trap_debug) 194 vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA; 195 196 /* If KDE or MDE are set, perform a full save/restore cycle. */ 197 if (vcpu_read_sys_reg(vcpu, MDSCR_EL1) & (DBG_MDSCR_KDE | DBG_MDSCR_MDE)) 198 vcpu->arch.flags |= KVM_ARM64_DEBUG_DIRTY; 199 200 /* Write mdcr_el2 changes since vcpu_load on VHE systems */ 201 if (has_vhe() && orig_mdcr_el2 != vcpu->arch.mdcr_el2) 202 write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2); 203 204 trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.mdcr_el2); 205 trace_kvm_arm_set_dreg32("MDSCR_EL1", vcpu_read_sys_reg(vcpu, MDSCR_EL1)); 206 } 207 208 void kvm_arm_clear_debug(struct kvm_vcpu *vcpu) 209 { 210 trace_kvm_arm_clear_debug(vcpu->guest_debug); 211 212 if (vcpu->guest_debug) { 213 restore_guest_debug_regs(vcpu); 214 215 /* 216 * If we were using HW debug we need to restore the 217 * debug_ptr to the guest debug state. 218 */ 219 if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) { 220 kvm_arm_reset_debug_ptr(vcpu); 221 222 trace_kvm_arm_set_regset("BKPTS", get_num_brps(), 223 &vcpu->arch.debug_ptr->dbg_bcr[0], 224 &vcpu->arch.debug_ptr->dbg_bvr[0]); 225 226 trace_kvm_arm_set_regset("WAPTS", get_num_wrps(), 227 &vcpu->arch.debug_ptr->dbg_wcr[0], 228 &vcpu->arch.debug_ptr->dbg_wvr[0]); 229 } 230 } 231 } 232