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(u64, 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_setup_mdcr_el2 - configure vcpu mdcr_el2 value 73 * 74 * @vcpu: the vcpu pointer 75 * 76 * This ensures we will trap access to: 77 * - Performance monitors (MDCR_EL2_TPM/MDCR_EL2_TPMCR) 78 * - Debug ROM Address (MDCR_EL2_TDRA) 79 * - OS related registers (MDCR_EL2_TDOSA) 80 * - Statistical profiler (MDCR_EL2_TPMS/MDCR_EL2_E2PB) 81 * - Self-hosted Trace Filter controls (MDCR_EL2_TTRF) 82 * - Self-hosted Trace (MDCR_EL2_TTRF/MDCR_EL2_E2TB) 83 */ 84 static void kvm_arm_setup_mdcr_el2(struct kvm_vcpu *vcpu) 85 { 86 /* 87 * This also clears MDCR_EL2_E2PB_MASK and MDCR_EL2_E2TB_MASK 88 * to disable guest access to the profiling and trace buffers 89 */ 90 vcpu->arch.mdcr_el2 = __this_cpu_read(mdcr_el2) & MDCR_EL2_HPMN_MASK; 91 vcpu->arch.mdcr_el2 |= (MDCR_EL2_TPM | 92 MDCR_EL2_TPMS | 93 MDCR_EL2_TTRF | 94 MDCR_EL2_TPMCR | 95 MDCR_EL2_TDRA | 96 MDCR_EL2_TDOSA); 97 98 /* Is the VM being debugged by userspace? */ 99 if (vcpu->guest_debug) 100 /* Route all software debug exceptions to EL2 */ 101 vcpu->arch.mdcr_el2 |= MDCR_EL2_TDE; 102 103 /* 104 * Trap debug register access when one of the following is true: 105 * - Userspace is using the hardware to debug the guest 106 * (KVM_GUESTDBG_USE_HW is set). 107 * - The guest is not using debug (KVM_ARM64_DEBUG_DIRTY is clear). 108 */ 109 if ((vcpu->guest_debug & KVM_GUESTDBG_USE_HW) || 110 !(vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY)) 111 vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA; 112 113 trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.mdcr_el2); 114 } 115 116 /** 117 * kvm_arm_vcpu_init_debug - setup vcpu debug traps 118 * 119 * @vcpu: the vcpu pointer 120 * 121 * Set vcpu initial mdcr_el2 value. 122 */ 123 void kvm_arm_vcpu_init_debug(struct kvm_vcpu *vcpu) 124 { 125 preempt_disable(); 126 kvm_arm_setup_mdcr_el2(vcpu); 127 preempt_enable(); 128 } 129 130 /** 131 * kvm_arm_reset_debug_ptr - reset the debug ptr to point to the vcpu state 132 */ 133 134 void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu) 135 { 136 vcpu->arch.debug_ptr = &vcpu->arch.vcpu_debug_state; 137 } 138 139 /** 140 * kvm_arm_setup_debug - set up debug related stuff 141 * 142 * @vcpu: the vcpu pointer 143 * 144 * This is called before each entry into the hypervisor to setup any 145 * debug related registers. 146 * 147 * Additionally, KVM only traps guest accesses to the debug registers if 148 * the guest is not actively using them (see the KVM_ARM64_DEBUG_DIRTY 149 * flag on vcpu->arch.flags). Since the guest must not interfere 150 * with the hardware state when debugging the guest, we must ensure that 151 * trapping is enabled whenever we are debugging the guest using the 152 * debug registers. 153 */ 154 155 void kvm_arm_setup_debug(struct kvm_vcpu *vcpu) 156 { 157 unsigned long mdscr, orig_mdcr_el2 = vcpu->arch.mdcr_el2; 158 159 trace_kvm_arm_setup_debug(vcpu, vcpu->guest_debug); 160 161 kvm_arm_setup_mdcr_el2(vcpu); 162 163 /* Is Guest debugging in effect? */ 164 if (vcpu->guest_debug) { 165 /* Save guest debug state */ 166 save_guest_debug_regs(vcpu); 167 168 /* 169 * Single Step (ARM ARM D2.12.3 The software step state 170 * machine) 171 * 172 * If we are doing Single Step we need to manipulate 173 * the guest's MDSCR_EL1.SS and PSTATE.SS. Once the 174 * step has occurred the hypervisor will trap the 175 * debug exception and we return to userspace. 176 * 177 * If the guest attempts to single step its userspace 178 * we would have to deal with a trapped exception 179 * while in the guest kernel. Because this would be 180 * hard to unwind we suppress the guest's ability to 181 * do so by masking MDSCR_EL.SS. 182 * 183 * This confuses guest debuggers which use 184 * single-step behind the scenes but everything 185 * returns to normal once the host is no longer 186 * debugging the system. 187 */ 188 if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) { 189 *vcpu_cpsr(vcpu) |= DBG_SPSR_SS; 190 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1); 191 mdscr |= DBG_MDSCR_SS; 192 vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1); 193 } else { 194 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1); 195 mdscr &= ~DBG_MDSCR_SS; 196 vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1); 197 } 198 199 trace_kvm_arm_set_dreg32("SPSR_EL2", *vcpu_cpsr(vcpu)); 200 201 /* 202 * HW Breakpoints and watchpoints 203 * 204 * We simply switch the debug_ptr to point to our new 205 * external_debug_state which has been populated by the 206 * debug ioctl. The existing KVM_ARM64_DEBUG_DIRTY 207 * mechanism ensures the registers are updated on the 208 * world switch. 209 */ 210 if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) { 211 /* Enable breakpoints/watchpoints */ 212 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1); 213 mdscr |= DBG_MDSCR_MDE; 214 vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1); 215 216 vcpu->arch.debug_ptr = &vcpu->arch.external_debug_state; 217 vcpu->arch.flags |= KVM_ARM64_DEBUG_DIRTY; 218 219 trace_kvm_arm_set_regset("BKPTS", get_num_brps(), 220 &vcpu->arch.debug_ptr->dbg_bcr[0], 221 &vcpu->arch.debug_ptr->dbg_bvr[0]); 222 223 trace_kvm_arm_set_regset("WAPTS", get_num_wrps(), 224 &vcpu->arch.debug_ptr->dbg_wcr[0], 225 &vcpu->arch.debug_ptr->dbg_wvr[0]); 226 } 227 } 228 229 BUG_ON(!vcpu->guest_debug && 230 vcpu->arch.debug_ptr != &vcpu->arch.vcpu_debug_state); 231 232 /* If KDE or MDE are set, perform a full save/restore cycle. */ 233 if (vcpu_read_sys_reg(vcpu, MDSCR_EL1) & (DBG_MDSCR_KDE | DBG_MDSCR_MDE)) 234 vcpu->arch.flags |= KVM_ARM64_DEBUG_DIRTY; 235 236 /* Write mdcr_el2 changes since vcpu_load on VHE systems */ 237 if (has_vhe() && orig_mdcr_el2 != vcpu->arch.mdcr_el2) 238 write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2); 239 240 trace_kvm_arm_set_dreg32("MDSCR_EL1", vcpu_read_sys_reg(vcpu, MDSCR_EL1)); 241 } 242 243 void kvm_arm_clear_debug(struct kvm_vcpu *vcpu) 244 { 245 trace_kvm_arm_clear_debug(vcpu->guest_debug); 246 247 if (vcpu->guest_debug) { 248 restore_guest_debug_regs(vcpu); 249 250 /* 251 * If we were using HW debug we need to restore the 252 * debug_ptr to the guest debug state. 253 */ 254 if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) { 255 kvm_arm_reset_debug_ptr(vcpu); 256 257 trace_kvm_arm_set_regset("BKPTS", get_num_brps(), 258 &vcpu->arch.debug_ptr->dbg_bcr[0], 259 &vcpu->arch.debug_ptr->dbg_bvr[0]); 260 261 trace_kvm_arm_set_regset("WAPTS", get_num_wrps(), 262 &vcpu->arch.debug_ptr->dbg_wcr[0], 263 &vcpu->arch.debug_ptr->dbg_wvr[0]); 264 } 265 } 266 } 267 268 void kvm_arch_vcpu_load_debug_state_flags(struct kvm_vcpu *vcpu) 269 { 270 u64 dfr0; 271 272 /* For VHE, there is nothing to do */ 273 if (has_vhe()) 274 return; 275 276 dfr0 = read_sysreg(id_aa64dfr0_el1); 277 /* 278 * If SPE is present on this CPU and is available at current EL, 279 * we may need to check if the host state needs to be saved. 280 */ 281 if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_PMSVER_SHIFT) && 282 !(read_sysreg_s(SYS_PMBIDR_EL1) & BIT(SYS_PMBIDR_EL1_P_SHIFT))) 283 vcpu->arch.flags |= KVM_ARM64_DEBUG_STATE_SAVE_SPE; 284 285 /* Check if we have TRBE implemented and available at the host */ 286 if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_TRBE_SHIFT) && 287 !(read_sysreg_s(SYS_TRBIDR_EL1) & TRBIDR_PROG)) 288 vcpu->arch.flags |= KVM_ARM64_DEBUG_STATE_SAVE_TRBE; 289 } 290 291 void kvm_arch_vcpu_put_debug_state_flags(struct kvm_vcpu *vcpu) 292 { 293 vcpu->arch.flags &= ~(KVM_ARM64_DEBUG_STATE_SAVE_SPE | 294 KVM_ARM64_DEBUG_STATE_SAVE_TRBE); 295 } 296