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 * - The guest has enabled the OS Lock (debug exceptions are blocked). 109 */ 110 if ((vcpu->guest_debug & KVM_GUESTDBG_USE_HW) || 111 !(vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY) || 112 kvm_vcpu_os_lock_enabled(vcpu)) 113 vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA; 114 115 trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.mdcr_el2); 116 } 117 118 /** 119 * kvm_arm_vcpu_init_debug - setup vcpu debug traps 120 * 121 * @vcpu: the vcpu pointer 122 * 123 * Set vcpu initial mdcr_el2 value. 124 */ 125 void kvm_arm_vcpu_init_debug(struct kvm_vcpu *vcpu) 126 { 127 preempt_disable(); 128 kvm_arm_setup_mdcr_el2(vcpu); 129 preempt_enable(); 130 } 131 132 /** 133 * kvm_arm_reset_debug_ptr - reset the debug ptr to point to the vcpu state 134 */ 135 136 void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu) 137 { 138 vcpu->arch.debug_ptr = &vcpu->arch.vcpu_debug_state; 139 } 140 141 /** 142 * kvm_arm_setup_debug - set up debug related stuff 143 * 144 * @vcpu: the vcpu pointer 145 * 146 * This is called before each entry into the hypervisor to setup any 147 * debug related registers. 148 * 149 * Additionally, KVM only traps guest accesses to the debug registers if 150 * the guest is not actively using them (see the KVM_ARM64_DEBUG_DIRTY 151 * flag on vcpu->arch.flags). Since the guest must not interfere 152 * with the hardware state when debugging the guest, we must ensure that 153 * trapping is enabled whenever we are debugging the guest using the 154 * debug registers. 155 */ 156 157 void kvm_arm_setup_debug(struct kvm_vcpu *vcpu) 158 { 159 unsigned long mdscr, orig_mdcr_el2 = vcpu->arch.mdcr_el2; 160 161 trace_kvm_arm_setup_debug(vcpu, vcpu->guest_debug); 162 163 kvm_arm_setup_mdcr_el2(vcpu); 164 165 /* Check if we need to use the debug registers. */ 166 if (vcpu->guest_debug || kvm_vcpu_os_lock_enabled(vcpu)) { 167 /* Save guest debug state */ 168 save_guest_debug_regs(vcpu); 169 170 /* 171 * Single Step (ARM ARM D2.12.3 The software step state 172 * machine) 173 * 174 * If we are doing Single Step we need to manipulate 175 * the guest's MDSCR_EL1.SS and PSTATE.SS. Once the 176 * step has occurred the hypervisor will trap the 177 * debug exception and we return to userspace. 178 * 179 * If the guest attempts to single step its userspace 180 * we would have to deal with a trapped exception 181 * while in the guest kernel. Because this would be 182 * hard to unwind we suppress the guest's ability to 183 * do so by masking MDSCR_EL.SS. 184 * 185 * This confuses guest debuggers which use 186 * single-step behind the scenes but everything 187 * returns to normal once the host is no longer 188 * debugging the system. 189 */ 190 if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) { 191 *vcpu_cpsr(vcpu) |= DBG_SPSR_SS; 192 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1); 193 mdscr |= DBG_MDSCR_SS; 194 vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1); 195 } else { 196 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1); 197 mdscr &= ~DBG_MDSCR_SS; 198 vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1); 199 } 200 201 trace_kvm_arm_set_dreg32("SPSR_EL2", *vcpu_cpsr(vcpu)); 202 203 /* 204 * HW Breakpoints and watchpoints 205 * 206 * We simply switch the debug_ptr to point to our new 207 * external_debug_state which has been populated by the 208 * debug ioctl. The existing KVM_ARM64_DEBUG_DIRTY 209 * mechanism ensures the registers are updated on the 210 * world switch. 211 */ 212 if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) { 213 /* Enable breakpoints/watchpoints */ 214 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1); 215 mdscr |= DBG_MDSCR_MDE; 216 vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1); 217 218 vcpu->arch.debug_ptr = &vcpu->arch.external_debug_state; 219 vcpu->arch.flags |= KVM_ARM64_DEBUG_DIRTY; 220 221 trace_kvm_arm_set_regset("BKPTS", get_num_brps(), 222 &vcpu->arch.debug_ptr->dbg_bcr[0], 223 &vcpu->arch.debug_ptr->dbg_bvr[0]); 224 225 trace_kvm_arm_set_regset("WAPTS", get_num_wrps(), 226 &vcpu->arch.debug_ptr->dbg_wcr[0], 227 &vcpu->arch.debug_ptr->dbg_wvr[0]); 228 229 /* 230 * The OS Lock blocks debug exceptions in all ELs when it is 231 * enabled. If the guest has enabled the OS Lock, constrain its 232 * effects to the guest. Emulate the behavior by clearing 233 * MDSCR_EL1.MDE. In so doing, we ensure that host debug 234 * exceptions are unaffected by guest configuration of the OS 235 * Lock. 236 */ 237 } else if (kvm_vcpu_os_lock_enabled(vcpu)) { 238 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1); 239 mdscr &= ~DBG_MDSCR_MDE; 240 vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1); 241 } 242 } 243 244 BUG_ON(!vcpu->guest_debug && 245 vcpu->arch.debug_ptr != &vcpu->arch.vcpu_debug_state); 246 247 /* If KDE or MDE are set, perform a full save/restore cycle. */ 248 if (vcpu_read_sys_reg(vcpu, MDSCR_EL1) & (DBG_MDSCR_KDE | DBG_MDSCR_MDE)) 249 vcpu->arch.flags |= KVM_ARM64_DEBUG_DIRTY; 250 251 /* Write mdcr_el2 changes since vcpu_load on VHE systems */ 252 if (has_vhe() && orig_mdcr_el2 != vcpu->arch.mdcr_el2) 253 write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2); 254 255 trace_kvm_arm_set_dreg32("MDSCR_EL1", vcpu_read_sys_reg(vcpu, MDSCR_EL1)); 256 } 257 258 void kvm_arm_clear_debug(struct kvm_vcpu *vcpu) 259 { 260 trace_kvm_arm_clear_debug(vcpu->guest_debug); 261 262 /* 263 * Restore the guest's debug registers if we were using them. 264 */ 265 if (vcpu->guest_debug || kvm_vcpu_os_lock_enabled(vcpu)) { 266 restore_guest_debug_regs(vcpu); 267 268 /* 269 * If we were using HW debug we need to restore the 270 * debug_ptr to the guest debug state. 271 */ 272 if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) { 273 kvm_arm_reset_debug_ptr(vcpu); 274 275 trace_kvm_arm_set_regset("BKPTS", get_num_brps(), 276 &vcpu->arch.debug_ptr->dbg_bcr[0], 277 &vcpu->arch.debug_ptr->dbg_bvr[0]); 278 279 trace_kvm_arm_set_regset("WAPTS", get_num_wrps(), 280 &vcpu->arch.debug_ptr->dbg_wcr[0], 281 &vcpu->arch.debug_ptr->dbg_wvr[0]); 282 } 283 } 284 } 285 286 void kvm_arch_vcpu_load_debug_state_flags(struct kvm_vcpu *vcpu) 287 { 288 u64 dfr0; 289 290 /* For VHE, there is nothing to do */ 291 if (has_vhe()) 292 return; 293 294 dfr0 = read_sysreg(id_aa64dfr0_el1); 295 /* 296 * If SPE is present on this CPU and is available at current EL, 297 * we may need to check if the host state needs to be saved. 298 */ 299 if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_PMSVER_SHIFT) && 300 !(read_sysreg_s(SYS_PMBIDR_EL1) & BIT(SYS_PMBIDR_EL1_P_SHIFT))) 301 vcpu->arch.flags |= KVM_ARM64_DEBUG_STATE_SAVE_SPE; 302 303 /* Check if we have TRBE implemented and available at the host */ 304 if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_TRBE_SHIFT) && 305 !(read_sysreg_s(SYS_TRBIDR_EL1) & TRBIDR_PROG)) 306 vcpu->arch.flags |= KVM_ARM64_DEBUG_STATE_SAVE_TRBE; 307 } 308 309 void kvm_arch_vcpu_put_debug_state_flags(struct kvm_vcpu *vcpu) 310 { 311 vcpu->arch.flags &= ~(KVM_ARM64_DEBUG_STATE_SAVE_SPE | 312 KVM_ARM64_DEBUG_STATE_SAVE_TRBE); 313 } 314