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 * - Self-hosted Trace Filter controls (MDCR_EL2_TTRF) 93 * 94 * Additionally, KVM only traps guest accesses to the debug registers if 95 * the guest is not actively using them (see the KVM_ARM64_DEBUG_DIRTY 96 * flag on vcpu->arch.flags). Since the guest must not interfere 97 * with the hardware state when debugging the guest, we must ensure that 98 * trapping is enabled whenever we are debugging the guest using the 99 * debug registers. 100 */ 101 102 void kvm_arm_setup_debug(struct kvm_vcpu *vcpu) 103 { 104 bool trap_debug = !(vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY); 105 unsigned long mdscr, orig_mdcr_el2 = vcpu->arch.mdcr_el2; 106 107 trace_kvm_arm_setup_debug(vcpu, vcpu->guest_debug); 108 109 /* 110 * This also clears MDCR_EL2_E2PB_MASK to disable guest access 111 * to the profiling buffer. 112 */ 113 vcpu->arch.mdcr_el2 = __this_cpu_read(mdcr_el2) & MDCR_EL2_HPMN_MASK; 114 vcpu->arch.mdcr_el2 |= (MDCR_EL2_TPM | 115 MDCR_EL2_TPMS | 116 MDCR_EL2_TTRF | 117 MDCR_EL2_TPMCR | 118 MDCR_EL2_TDRA | 119 MDCR_EL2_TDOSA); 120 121 /* Is Guest debugging in effect? */ 122 if (vcpu->guest_debug) { 123 /* Route all software debug exceptions to EL2 */ 124 vcpu->arch.mdcr_el2 |= MDCR_EL2_TDE; 125 126 /* Save guest debug state */ 127 save_guest_debug_regs(vcpu); 128 129 /* 130 * Single Step (ARM ARM D2.12.3 The software step state 131 * machine) 132 * 133 * If we are doing Single Step we need to manipulate 134 * the guest's MDSCR_EL1.SS and PSTATE.SS. Once the 135 * step has occurred the hypervisor will trap the 136 * debug exception and we return to userspace. 137 * 138 * If the guest attempts to single step its userspace 139 * we would have to deal with a trapped exception 140 * while in the guest kernel. Because this would be 141 * hard to unwind we suppress the guest's ability to 142 * do so by masking MDSCR_EL.SS. 143 * 144 * This confuses guest debuggers which use 145 * single-step behind the scenes but everything 146 * returns to normal once the host is no longer 147 * debugging the system. 148 */ 149 if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) { 150 *vcpu_cpsr(vcpu) |= DBG_SPSR_SS; 151 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1); 152 mdscr |= DBG_MDSCR_SS; 153 vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1); 154 } else { 155 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1); 156 mdscr &= ~DBG_MDSCR_SS; 157 vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1); 158 } 159 160 trace_kvm_arm_set_dreg32("SPSR_EL2", *vcpu_cpsr(vcpu)); 161 162 /* 163 * HW Breakpoints and watchpoints 164 * 165 * We simply switch the debug_ptr to point to our new 166 * external_debug_state which has been populated by the 167 * debug ioctl. The existing KVM_ARM64_DEBUG_DIRTY 168 * mechanism ensures the registers are updated on the 169 * world switch. 170 */ 171 if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) { 172 /* Enable breakpoints/watchpoints */ 173 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1); 174 mdscr |= DBG_MDSCR_MDE; 175 vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1); 176 177 vcpu->arch.debug_ptr = &vcpu->arch.external_debug_state; 178 vcpu->arch.flags |= KVM_ARM64_DEBUG_DIRTY; 179 trap_debug = true; 180 181 trace_kvm_arm_set_regset("BKPTS", get_num_brps(), 182 &vcpu->arch.debug_ptr->dbg_bcr[0], 183 &vcpu->arch.debug_ptr->dbg_bvr[0]); 184 185 trace_kvm_arm_set_regset("WAPTS", get_num_wrps(), 186 &vcpu->arch.debug_ptr->dbg_wcr[0], 187 &vcpu->arch.debug_ptr->dbg_wvr[0]); 188 } 189 } 190 191 BUG_ON(!vcpu->guest_debug && 192 vcpu->arch.debug_ptr != &vcpu->arch.vcpu_debug_state); 193 194 /* Trap debug register access */ 195 if (trap_debug) 196 vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA; 197 198 /* If KDE or MDE are set, perform a full save/restore cycle. */ 199 if (vcpu_read_sys_reg(vcpu, MDSCR_EL1) & (DBG_MDSCR_KDE | DBG_MDSCR_MDE)) 200 vcpu->arch.flags |= KVM_ARM64_DEBUG_DIRTY; 201 202 /* Write mdcr_el2 changes since vcpu_load on VHE systems */ 203 if (has_vhe() && orig_mdcr_el2 != vcpu->arch.mdcr_el2) 204 write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2); 205 206 trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.mdcr_el2); 207 trace_kvm_arm_set_dreg32("MDSCR_EL1", vcpu_read_sys_reg(vcpu, MDSCR_EL1)); 208 } 209 210 void kvm_arm_clear_debug(struct kvm_vcpu *vcpu) 211 { 212 trace_kvm_arm_clear_debug(vcpu->guest_debug); 213 214 if (vcpu->guest_debug) { 215 restore_guest_debug_regs(vcpu); 216 217 /* 218 * If we were using HW debug we need to restore the 219 * debug_ptr to the guest debug state. 220 */ 221 if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) { 222 kvm_arm_reset_debug_ptr(vcpu); 223 224 trace_kvm_arm_set_regset("BKPTS", get_num_brps(), 225 &vcpu->arch.debug_ptr->dbg_bcr[0], 226 &vcpu->arch.debug_ptr->dbg_bvr[0]); 227 228 trace_kvm_arm_set_regset("WAPTS", get_num_wrps(), 229 &vcpu->arch.debug_ptr->dbg_wcr[0], 230 &vcpu->arch.debug_ptr->dbg_wvr[0]); 231 } 232 } 233 } 234