[mirror_ubuntu-artful-kernel.git] / arch / arm64 / kvm / debug.c

/*
 * Debug and Guest Debug support
 *
 * Copyright (C) 2015 - Linaro Ltd
 * Author: Alex Bennée <alex.bennee@linaro.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#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(u32, 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.
 */
static void save_guest_debug_regs(struct kvm_vcpu *vcpu)
{
	vcpu->arch.guest_debug_preserved.mdscr_el1 = vcpu_sys_reg(vcpu, MDSCR_EL1);

	trace_kvm_arm_set_dreg32("Saved MDSCR_EL1",
				vcpu->arch.guest_debug_preserved.mdscr_el1);
}

static void restore_guest_debug_regs(struct kvm_vcpu *vcpu)
{
	vcpu_sys_reg(vcpu, MDSCR_EL1) = vcpu->arch.guest_debug_preserved.mdscr_el1;

	trace_kvm_arm_set_dreg32("Restored MDSCR_EL1",
				vcpu_sys_reg(vcpu, MDSCR_EL1));
}

/**
 * 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(__kvm_get_mdcr_el2));
}

/**
 * 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. Currently this just 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)
 *
 * Additionally, KVM only traps guest accesses to the debug registers if
 * the guest is not actively using them (see the KVM_ARM64_DEBUG_DIRTY
 * flag on vcpu->arch.debug_flags).  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)
{
	bool trap_debug = !(vcpu->arch.debug_flags & KVM_ARM64_DEBUG_DIRTY);

	trace_kvm_arm_setup_debug(vcpu, vcpu->guest_debug);

	/*
	 * This also clears MDCR_EL2_E2PB_MASK to disable guest access
	 * to the profiling buffer.
	 */
	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_TPMCR |
				MDCR_EL2_TDRA |
				MDCR_EL2_TDOSA);

	/* Is Guest debugging in effect? */
	if (vcpu->guest_debug) {
		/* Route all software debug exceptions to EL2 */
		vcpu->arch.mdcr_el2 |= MDCR_EL2_TDE;

		/* 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) {
			*vcpu_cpsr(vcpu) |=  DBG_SPSR_SS;
			vcpu_sys_reg(vcpu, MDSCR_EL1) |= DBG_MDSCR_SS;
		} else {
			vcpu_sys_reg(vcpu, MDSCR_EL1) &= ~DBG_MDSCR_SS;
		}

		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 KVM_ARM64_DEBUG_DIRTY
		 * mechanism ensures the registers are updated on the
		 * world switch.
		 */
		if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) {
			/* Enable breakpoints/watchpoints */
			vcpu_sys_reg(vcpu, MDSCR_EL1) |= DBG_MDSCR_MDE;

			vcpu->arch.debug_ptr = &vcpu->arch.external_debug_state;
			vcpu->arch.debug_flags |= KVM_ARM64_DEBUG_DIRTY;
			trap_debug = true;

			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]);
		}
	}

	BUG_ON(!vcpu->guest_debug &&
		vcpu->arch.debug_ptr != &vcpu->arch.vcpu_debug_state);

	/* Trap debug register access */
	if (trap_debug)
		vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA;

	trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.mdcr_el2);
	trace_kvm_arm_set_dreg32("MDSCR_EL1", vcpu_sys_reg(vcpu, MDSCR_EL1));
}

void kvm_arm_clear_debug(struct kvm_vcpu *vcpu)
{
	trace_kvm_arm_clear_debug(vcpu->guest_debug);

	if (vcpu->guest_debug) {
		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]);
		}
	}
}
Commit	Line	Data
56c7f5e7 AB	1	/*
	2	* Debug and Guest Debug support
	3	*
	4	* Copyright (C) 2015 - Linaro Ltd
	5	* Author: Alex Bennée <alex.bennee@linaro.org>
	6	*
	7	* This program is free software; you can redistribute it and/or modify
	8	* it under the terms of the GNU General Public License version 2 as
	9	* published by the Free Software Foundation.
	10	*
	11	* This program is distributed in the hope that it will be useful,
	12	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	13	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	14	* GNU General Public License for more details.
	15	*
	16	* You should have received a copy of the GNU General Public License
	17	* along with this program. If not, see <http://www.gnu.org/licenses/>.
	18	*/
	19
	20	#include <linux/kvm_host.h>
eef8c85a	21	#include <linux/hw_breakpoint.h>
56c7f5e7	22
337b99bf AB	23	#include <asm/debug-monitors.h>
337b99bf AB	24	#include <asm/kvm_asm.h>
56c7f5e7	25	#include <asm/kvm_arm.h>
337b99bf AB	26	#include <asm/kvm_emulate.h>
337b99bf AB	27
eef8c85a AB	28	#include "trace.h"
eef8c85a AB	29
337b99bf AB	30	/* These are the bits of MDSCR_EL1 we may manipulate */
	31	#define MDSCR_EL1_DEBUG_MASK (DBG_MDSCR_SS \| \
	32	DBG_MDSCR_KDE \| \
	33	DBG_MDSCR_MDE)
56c7f5e7 AB	34
	35	static DEFINE_PER_CPU(u32, mdcr_el2);
	36
337b99bf AB	37	/**
	38	* save/restore_guest_debug_regs
	39	*
	40	* For some debug operations we need to tweak some guest registers. As
	41	* a result we need to save the state of those registers before we
	42	* make those modifications.
	43	*
	44	* Guest access to MDSCR_EL1 is trapped by the hypervisor and handled
	45	* after we have restored the preserved value to the main context.
	46	*/
	47	static void save_guest_debug_regs(struct kvm_vcpu *vcpu)
	48	{
	49	vcpu->arch.guest_debug_preserved.mdscr_el1 = vcpu_sys_reg(vcpu, MDSCR_EL1);
eef8c85a AB	50
	51	trace_kvm_arm_set_dreg32("Saved MDSCR_EL1",
	52	vcpu->arch.guest_debug_preserved.mdscr_el1);
337b99bf AB	53	}
	54
	55	static void restore_guest_debug_regs(struct kvm_vcpu *vcpu)
	56	{
	57	vcpu_sys_reg(vcpu, MDSCR_EL1) = vcpu->arch.guest_debug_preserved.mdscr_el1;
eef8c85a AB	58
	59	trace_kvm_arm_set_dreg32("Restored MDSCR_EL1",
	60	vcpu_sys_reg(vcpu, MDSCR_EL1));
337b99bf AB	61	}
337b99bf AB	62
56c7f5e7 AB	63	/**
	64	* kvm_arm_init_debug - grab what we need for debug
	65	*
	66	* Currently the sole task of this function is to retrieve the initial
	67	* value of mdcr_el2 so we can preserve MDCR_EL2.HPMN which has
	68	* presumably been set-up by some knowledgeable bootcode.
	69	*
	70	* It is called once per-cpu during CPU hyp initialisation.
	71	*/
	72
	73	void kvm_arm_init_debug(void)
	74	{
	75	__this_cpu_write(mdcr_el2, kvm_call_hyp(__kvm_get_mdcr_el2));
	76	}
	77
84e690bf AB	78	/**
	79	* kvm_arm_reset_debug_ptr - reset the debug ptr to point to the vcpu state
	80	*/
	81
	82	void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu)
	83	{
	84	vcpu->arch.debug_ptr = &vcpu->arch.vcpu_debug_state;
	85	}
	86
56c7f5e7 AB	87	/**
	88	* kvm_arm_setup_debug - set up debug related stuff
	89	*
	90	* @vcpu: the vcpu pointer
	91	*
	92	* This is called before each entry into the hypervisor to setup any
	93	* debug related registers. Currently this just ensures we will trap
	94	* access to:
	95	* - Performance monitors (MDCR_EL2_TPM/MDCR_EL2_TPMCR)
	96	* - Debug ROM Address (MDCR_EL2_TDRA)
	97	* - OS related registers (MDCR_EL2_TDOSA)
f85279b4	98	* - Statistical profiler (MDCR_EL2_TPMS/MDCR_EL2_E2PB)
56c7f5e7 AB	99	*
	100	* Additionally, KVM only traps guest accesses to the debug registers if
	101	* the guest is not actively using them (see the KVM_ARM64_DEBUG_DIRTY
	102	* flag on vcpu->arch.debug_flags). Since the guest must not interfere
	103	* with the hardware state when debugging the guest, we must ensure that
	104	* trapping is enabled whenever we are debugging the guest using the
	105	* debug registers.
	106	*/
	107
	108	void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
	109	{
	110	bool trap_debug = !(vcpu->arch.debug_flags & KVM_ARM64_DEBUG_DIRTY);
	111
eef8c85a AB	112	trace_kvm_arm_setup_debug(vcpu, vcpu->guest_debug);
eef8c85a AB	113
f85279b4 WD	114	/*
	115	* This also clears MDCR_EL2_E2PB_MASK to disable guest access
	116	* to the profiling buffer.
	117	*/
56c7f5e7 AB	118	vcpu->arch.mdcr_el2 = __this_cpu_read(mdcr_el2) & MDCR_EL2_HPMN_MASK;
56c7f5e7 AB	119	vcpu->arch.mdcr_el2 \|= (MDCR_EL2_TPM \|
f85279b4	120	MDCR_EL2_TPMS \|
56c7f5e7 AB	121	MDCR_EL2_TPMCR \|
	122	MDCR_EL2_TDRA \|
	123	MDCR_EL2_TDOSA);
	124
337b99bf AB	125	/* Is Guest debugging in effect? */
	126	if (vcpu->guest_debug) {
	127	/* Route all software debug exceptions to EL2 */
4bd611ca	128	vcpu->arch.mdcr_el2 \|= MDCR_EL2_TDE;
337b99bf AB	129
	130	/* Save guest debug state */
	131	save_guest_debug_regs(vcpu);
	132
	133	/*
	134	* Single Step (ARM ARM D2.12.3 The software step state
	135	* machine)
	136	*
	137	* If we are doing Single Step we need to manipulate
	138	* the guest's MDSCR_EL1.SS and PSTATE.SS. Once the
	139	* step has occurred the hypervisor will trap the
	140	* debug exception and we return to userspace.
	141	*
	142	* If the guest attempts to single step its userspace
	143	* we would have to deal with a trapped exception
	144	* while in the guest kernel. Because this would be
	145	* hard to unwind we suppress the guest's ability to
	146	* do so by masking MDSCR_EL.SS.
	147	*
	148	* This confuses guest debuggers which use
	149	* single-step behind the scenes but everything
	150	* returns to normal once the host is no longer
	151	* debugging the system.
	152	*/
	153	if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
	154	*vcpu_cpsr(vcpu) \|= DBG_SPSR_SS;
	155	vcpu_sys_reg(vcpu, MDSCR_EL1) \|= DBG_MDSCR_SS;
	156	} else {
	157	vcpu_sys_reg(vcpu, MDSCR_EL1) &= ~DBG_MDSCR_SS;
	158	}
834bf887	159
eef8c85a AB	160	trace_kvm_arm_set_dreg32("SPSR_EL2", *vcpu_cpsr(vcpu));
eef8c85a AB	161
834bf887 AB	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	vcpu_sys_reg(vcpu, MDSCR_EL1) \|= DBG_MDSCR_MDE;
	174
	175	vcpu->arch.debug_ptr = &vcpu->arch.external_debug_state;
	176	vcpu->arch.debug_flags \|= KVM_ARM64_DEBUG_DIRTY;
	177	trap_debug = true;
eef8c85a AB	178
	179	trace_kvm_arm_set_regset("BKPTS", get_num_brps(),
	180	&vcpu->arch.debug_ptr->dbg_bcr[0],
	181	&vcpu->arch.debug_ptr->dbg_bvr[0]);
	182
	183	trace_kvm_arm_set_regset("WAPTS", get_num_wrps(),
	184	&vcpu->arch.debug_ptr->dbg_wcr[0],
	185	&vcpu->arch.debug_ptr->dbg_wvr[0]);
834bf887	186	}
337b99bf	187	}
834bf887 AB	188
	189	BUG_ON(!vcpu->guest_debug &&
	190	vcpu->arch.debug_ptr != &vcpu->arch.vcpu_debug_state);
	191
	192	/* Trap debug register access */
	193	if (trap_debug)
	194	vcpu->arch.mdcr_el2 \|= MDCR_EL2_TDA;
eef8c85a AB	195
	196	trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.mdcr_el2);
	197	trace_kvm_arm_set_dreg32("MDSCR_EL1", vcpu_sys_reg(vcpu, MDSCR_EL1));
56c7f5e7 AB	198	}
	199
	200	void kvm_arm_clear_debug(struct kvm_vcpu *vcpu)
	201	{
eef8c85a AB	202	trace_kvm_arm_clear_debug(vcpu->guest_debug);
eef8c85a AB	203
834bf887	204	if (vcpu->guest_debug) {
337b99bf	205	restore_guest_debug_regs(vcpu);
834bf887 AB	206
	207	/*
	208	* If we were using HW debug we need to restore the
	209	* debug_ptr to the guest debug state.
	210	*/
eef8c85a	211	if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) {
834bf887 AB	212	kvm_arm_reset_debug_ptr(vcpu);
834bf887 AB	213
eef8c85a AB	214	trace_kvm_arm_set_regset("BKPTS", get_num_brps(),
	215	&vcpu->arch.debug_ptr->dbg_bcr[0],
	216	&vcpu->arch.debug_ptr->dbg_bvr[0]);
	217
	218	trace_kvm_arm_set_regset("WAPTS", get_num_wrps(),
	219	&vcpu->arch.debug_ptr->dbg_wcr[0],
	220	&vcpu->arch.debug_ptr->dbg_wvr[0]);
	221	}
834bf887	222	}
56c7f5e7	223	}