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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 | // 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(u64, 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. * * When single-step is enabled by userspace, we tweak PSTATE.SS on every * guest entry. Preserve PSTATE.SS so we can restore the original value * for the vcpu after the single-step is disabled. */ 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); vcpu->arch.guest_debug_preserved.pstate_ss = (*vcpu_cpsr(vcpu) & DBG_SPSR_SS); } 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)); if (vcpu->arch.guest_debug_preserved.pstate_ss) *vcpu_cpsr(vcpu) |= DBG_SPSR_SS; else *vcpu_cpsr(vcpu) &= ~DBG_SPSR_SS; } /** * 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_setup_mdcr_el2 - configure vcpu mdcr_el2 value * * @vcpu: the vcpu pointer * * This 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) * - Self-hosted Trace (MDCR_EL2_TTRF/MDCR_EL2_E2TB) */ static void kvm_arm_setup_mdcr_el2(struct kvm_vcpu *vcpu) { /* * This also clears MDCR_EL2_E2PB_MASK and MDCR_EL2_E2TB_MASK * to disable guest access to the profiling and trace buffers */ 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 the VM being debugged by userspace? */ if (vcpu->guest_debug) /* Route all software debug exceptions to EL2 */ vcpu->arch.mdcr_el2 |= MDCR_EL2_TDE; /* * Trap debug register access when one of the following is true: * - Userspace is using the hardware to debug the guest * (KVM_GUESTDBG_USE_HW is set). * - The guest is not using debug (DEBUG_DIRTY clear). * - The guest has enabled the OS Lock (debug exceptions are blocked). */ if ((vcpu->guest_debug & KVM_GUESTDBG_USE_HW) || !vcpu_get_flag(vcpu, DEBUG_DIRTY) || kvm_vcpu_os_lock_enabled(vcpu)) vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA; trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.mdcr_el2); } /** * kvm_arm_vcpu_init_debug - setup vcpu debug traps * * @vcpu: the vcpu pointer * * Set vcpu initial mdcr_el2 value. */ void kvm_arm_vcpu_init_debug(struct kvm_vcpu *vcpu) { preempt_disable(); kvm_arm_setup_mdcr_el2(vcpu); preempt_enable(); } /** * 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. * * Additionally, KVM only traps guest accesses to the debug registers if * the guest is not actively using them (see the DEBUG_DIRTY * flag on vcpu->arch.iflags). 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) { unsigned long mdscr, orig_mdcr_el2 = vcpu->arch.mdcr_el2; trace_kvm_arm_setup_debug(vcpu, vcpu->guest_debug); kvm_arm_setup_mdcr_el2(vcpu); /* Check if we need to use the debug registers. */ if (vcpu->guest_debug || kvm_vcpu_os_lock_enabled(vcpu)) { /* 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) { /* * If the software step state at the last guest exit * was Active-pending, we don't set DBG_SPSR_SS so * that the state is maintained (to not run another * single-step until the pending Software Step * exception is taken). */ if (!vcpu_get_flag(vcpu, DBG_SS_ACTIVE_PENDING)) *vcpu_cpsr(vcpu) |= DBG_SPSR_SS; else *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 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_set_flag(vcpu, DEBUG_DIRTY); 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]); /* * The OS Lock blocks debug exceptions in all ELs when it is * enabled. If the guest has enabled the OS Lock, constrain its * effects to the guest. Emulate the behavior by clearing * MDSCR_EL1.MDE. In so doing, we ensure that host debug * exceptions are unaffected by guest configuration of the OS * Lock. */ } else if (kvm_vcpu_os_lock_enabled(vcpu)) { mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1); mdscr &= ~DBG_MDSCR_MDE; vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1); } } BUG_ON(!vcpu->guest_debug && vcpu->arch.debug_ptr != &vcpu->arch.vcpu_debug_state); /* 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_set_flag(vcpu, 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("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); /* * Restore the guest's debug registers if we were using them. */ if (vcpu->guest_debug || kvm_vcpu_os_lock_enabled(vcpu)) { if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) { if (!(*vcpu_cpsr(vcpu) & DBG_SPSR_SS)) /* * Mark the vcpu as ACTIVE_PENDING * until Software Step exception is taken. */ vcpu_set_flag(vcpu, DBG_SS_ACTIVE_PENDING); } 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]); } } } void kvm_arch_vcpu_load_debug_state_flags(struct kvm_vcpu *vcpu) { u64 dfr0; /* For VHE, there is nothing to do */ if (has_vhe()) return; dfr0 = read_sysreg(id_aa64dfr0_el1); /* * If SPE is present on this CPU and is available at current EL, * we may need to check if the host state needs to be saved. */ if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_PMSVer_SHIFT) && !(read_sysreg_s(SYS_PMBIDR_EL1) & BIT(SYS_PMBIDR_EL1_P_SHIFT))) vcpu_set_flag(vcpu, DEBUG_STATE_SAVE_SPE); /* Check if we have TRBE implemented and available at the host */ if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_TraceBuffer_SHIFT) && !(read_sysreg_s(SYS_TRBIDR_EL1) & TRBIDR_PROG)) vcpu_set_flag(vcpu, DEBUG_STATE_SAVE_TRBE); } void kvm_arch_vcpu_put_debug_state_flags(struct kvm_vcpu *vcpu) { vcpu_clear_flag(vcpu, DEBUG_STATE_SAVE_SPE); vcpu_clear_flag(vcpu, DEBUG_STATE_SAVE_TRBE); } |