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Diffstat (limited to 'arch/arm64/kvm/debug.c')
| -rw-r--r-- | arch/arm64/kvm/debug.c | 344 |
1 files changed, 344 insertions, 0 deletions
diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c new file mode 100644 index 000000000..fccf9ec01 --- /dev/null +++ b/arch/arm64/kvm/debug.c @@ -0,0 +1,344 @@ +// 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); +} |