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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>
21#include <linux/hw_breakpoint.h>
22
23#include <asm/debug-monitors.h>
24#include <asm/kvm_asm.h>
25#include <asm/kvm_arm.h>
26#include <asm/kvm_emulate.h>
27
28#include "trace.h"
29
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)
34
35static DEFINE_PER_CPU(u32, mdcr_el2);
36
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 */
47static void save_guest_debug_regs(struct kvm_vcpu *vcpu)
48{
49 vcpu->arch.guest_debug_preserved.mdscr_el1 = vcpu_sys_reg(vcpu, MDSCR_EL1);
50
51 trace_kvm_arm_set_dreg32("Saved MDSCR_EL1",
52 vcpu->arch.guest_debug_preserved.mdscr_el1);
53}
54
55static void restore_guest_debug_regs(struct kvm_vcpu *vcpu)
56{
57 vcpu_sys_reg(vcpu, MDSCR_EL1) = vcpu->arch.guest_debug_preserved.mdscr_el1;
58
59 trace_kvm_arm_set_dreg32("Restored MDSCR_EL1",
60 vcpu_sys_reg(vcpu, MDSCR_EL1));
61}
62
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
73void kvm_arm_init_debug(void)
74{
75 __this_cpu_write(mdcr_el2, kvm_call_hyp(__kvm_get_mdcr_el2));
76}
77
78/**
79 * kvm_arm_reset_debug_ptr - reset the debug ptr to point to the vcpu state
80 */
81
82void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu)
83{
84 vcpu->arch.debug_ptr = &vcpu->arch.vcpu_debug_state;
85}
86
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)
98 *
99 * Additionally, KVM only traps guest accesses to the debug registers if
100 * the guest is not actively using them (see the KVM_ARM64_DEBUG_DIRTY
101 * flag on vcpu->arch.debug_flags). Since the guest must not interfere
102 * with the hardware state when debugging the guest, we must ensure that
103 * trapping is enabled whenever we are debugging the guest using the
104 * debug registers.
105 */
106
107void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
108{
109 bool trap_debug = !(vcpu->arch.debug_flags & KVM_ARM64_DEBUG_DIRTY);
110
111 trace_kvm_arm_setup_debug(vcpu, vcpu->guest_debug);
112
113 vcpu->arch.mdcr_el2 = __this_cpu_read(mdcr_el2) & MDCR_EL2_HPMN_MASK;
114 vcpu->arch.mdcr_el2 |= (MDCR_EL2_TPM |
115 MDCR_EL2_TPMCR |
116 MDCR_EL2_TDRA |
117 MDCR_EL2_TDOSA);
118
119 /* Is Guest debugging in effect? */
120 if (vcpu->guest_debug) {
121 /* Route all software debug exceptions to EL2 */
122 vcpu->arch.mdcr_el2 |= MDCR_EL2_TDE;
123
124 /* Save guest debug state */
125 save_guest_debug_regs(vcpu);
126
127 /*
128 * Single Step (ARM ARM D2.12.3 The software step state
129 * machine)
130 *
131 * If we are doing Single Step we need to manipulate
132 * the guest's MDSCR_EL1.SS and PSTATE.SS. Once the
133 * step has occurred the hypervisor will trap the
134 * debug exception and we return to userspace.
135 *
136 * If the guest attempts to single step its userspace
137 * we would have to deal with a trapped exception
138 * while in the guest kernel. Because this would be
139 * hard to unwind we suppress the guest's ability to
140 * do so by masking MDSCR_EL.SS.
141 *
142 * This confuses guest debuggers which use
143 * single-step behind the scenes but everything
144 * returns to normal once the host is no longer
145 * debugging the system.
146 */
147 if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
148 *vcpu_cpsr(vcpu) |= DBG_SPSR_SS;
149 vcpu_sys_reg(vcpu, MDSCR_EL1) |= DBG_MDSCR_SS;
150 } else {
151 vcpu_sys_reg(vcpu, MDSCR_EL1) &= ~DBG_MDSCR_SS;
152 }
153
154 trace_kvm_arm_set_dreg32("SPSR_EL2", *vcpu_cpsr(vcpu));
155
156 /*
157 * HW Breakpoints and watchpoints
158 *
159 * We simply switch the debug_ptr to point to our new
160 * external_debug_state which has been populated by the
161 * debug ioctl. The existing KVM_ARM64_DEBUG_DIRTY
162 * mechanism ensures the registers are updated on the
163 * world switch.
164 */
165 if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) {
166 /* Enable breakpoints/watchpoints */
167 vcpu_sys_reg(vcpu, MDSCR_EL1) |= DBG_MDSCR_MDE;
168
169 vcpu->arch.debug_ptr = &vcpu->arch.external_debug_state;
170 vcpu->arch.debug_flags |= KVM_ARM64_DEBUG_DIRTY;
171 trap_debug = true;
172
173 trace_kvm_arm_set_regset("BKPTS", get_num_brps(),
174 &vcpu->arch.debug_ptr->dbg_bcr[0],
175 &vcpu->arch.debug_ptr->dbg_bvr[0]);
176
177 trace_kvm_arm_set_regset("WAPTS", get_num_wrps(),
178 &vcpu->arch.debug_ptr->dbg_wcr[0],
179 &vcpu->arch.debug_ptr->dbg_wvr[0]);
180 }
181 }
182
183 BUG_ON(!vcpu->guest_debug &&
184 vcpu->arch.debug_ptr != &vcpu->arch.vcpu_debug_state);
185
186 /* Trap debug register access */
187 if (trap_debug)
188 vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA;
189
190 trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.mdcr_el2);
191 trace_kvm_arm_set_dreg32("MDSCR_EL1", vcpu_sys_reg(vcpu, MDSCR_EL1));
192}
193
194void kvm_arm_clear_debug(struct kvm_vcpu *vcpu)
195{
196 trace_kvm_arm_clear_debug(vcpu->guest_debug);
197
198 if (vcpu->guest_debug) {
199 restore_guest_debug_regs(vcpu);
200
201 /*
202 * If we were using HW debug we need to restore the
203 * debug_ptr to the guest debug state.
204 */
205 if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) {
206 kvm_arm_reset_debug_ptr(vcpu);
207
208 trace_kvm_arm_set_regset("BKPTS", get_num_brps(),
209 &vcpu->arch.debug_ptr->dbg_bcr[0],
210 &vcpu->arch.debug_ptr->dbg_bvr[0]);
211
212 trace_kvm_arm_set_regset("WAPTS", get_num_wrps(),
213 &vcpu->arch.debug_ptr->dbg_wcr[0],
214 &vcpu->arch.debug_ptr->dbg_wvr[0]);
215 }
216 }
217}
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>
21#include <linux/hw_breakpoint.h>
22
23#include <asm/debug-monitors.h>
24#include <asm/kvm_asm.h>
25#include <asm/kvm_arm.h>
26#include <asm/kvm_emulate.h>
27
28#include "trace.h"
29
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)
34
35static DEFINE_PER_CPU(u32, mdcr_el2);
36
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 */
47static void save_guest_debug_regs(struct kvm_vcpu *vcpu)
48{
49 vcpu->arch.guest_debug_preserved.mdscr_el1 = vcpu_sys_reg(vcpu, MDSCR_EL1);
50
51 trace_kvm_arm_set_dreg32("Saved MDSCR_EL1",
52 vcpu->arch.guest_debug_preserved.mdscr_el1);
53}
54
55static void restore_guest_debug_regs(struct kvm_vcpu *vcpu)
56{
57 vcpu_sys_reg(vcpu, MDSCR_EL1) = vcpu->arch.guest_debug_preserved.mdscr_el1;
58
59 trace_kvm_arm_set_dreg32("Restored MDSCR_EL1",
60 vcpu_sys_reg(vcpu, MDSCR_EL1));
61}
62
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
73void kvm_arm_init_debug(void)
74{
75 __this_cpu_write(mdcr_el2, kvm_call_hyp(__kvm_get_mdcr_el2));
76}
77
78/**
79 * kvm_arm_reset_debug_ptr - reset the debug ptr to point to the vcpu state
80 */
81
82void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu)
83{
84 vcpu->arch.debug_ptr = &vcpu->arch.vcpu_debug_state;
85}
86
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)
98 *
99 * Additionally, KVM only traps guest accesses to the debug registers if
100 * the guest is not actively using them (see the KVM_ARM64_DEBUG_DIRTY
101 * flag on vcpu->arch.debug_flags). Since the guest must not interfere
102 * with the hardware state when debugging the guest, we must ensure that
103 * trapping is enabled whenever we are debugging the guest using the
104 * debug registers.
105 */
106
107void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
108{
109 bool trap_debug = !(vcpu->arch.debug_flags & KVM_ARM64_DEBUG_DIRTY);
110
111 trace_kvm_arm_setup_debug(vcpu, vcpu->guest_debug);
112
113 vcpu->arch.mdcr_el2 = __this_cpu_read(mdcr_el2) & MDCR_EL2_HPMN_MASK;
114 vcpu->arch.mdcr_el2 |= (MDCR_EL2_TPM |
115 MDCR_EL2_TPMCR |
116 MDCR_EL2_TDRA |
117 MDCR_EL2_TDOSA);
118
119 /* Is Guest debugging in effect? */
120 if (vcpu->guest_debug) {
121 /* Route all software debug exceptions to EL2 */
122 vcpu->arch.mdcr_el2 |= MDCR_EL2_TDE;
123
124 /* Save guest debug state */
125 save_guest_debug_regs(vcpu);
126
127 /*
128 * Single Step (ARM ARM D2.12.3 The software step state
129 * machine)
130 *
131 * If we are doing Single Step we need to manipulate
132 * the guest's MDSCR_EL1.SS and PSTATE.SS. Once the
133 * step has occurred the hypervisor will trap the
134 * debug exception and we return to userspace.
135 *
136 * If the guest attempts to single step its userspace
137 * we would have to deal with a trapped exception
138 * while in the guest kernel. Because this would be
139 * hard to unwind we suppress the guest's ability to
140 * do so by masking MDSCR_EL.SS.
141 *
142 * This confuses guest debuggers which use
143 * single-step behind the scenes but everything
144 * returns to normal once the host is no longer
145 * debugging the system.
146 */
147 if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
148 *vcpu_cpsr(vcpu) |= DBG_SPSR_SS;
149 vcpu_sys_reg(vcpu, MDSCR_EL1) |= DBG_MDSCR_SS;
150 } else {
151 vcpu_sys_reg(vcpu, MDSCR_EL1) &= ~DBG_MDSCR_SS;
152 }
153
154 trace_kvm_arm_set_dreg32("SPSR_EL2", *vcpu_cpsr(vcpu));
155
156 /*
157 * HW Breakpoints and watchpoints
158 *
159 * We simply switch the debug_ptr to point to our new
160 * external_debug_state which has been populated by the
161 * debug ioctl. The existing KVM_ARM64_DEBUG_DIRTY
162 * mechanism ensures the registers are updated on the
163 * world switch.
164 */
165 if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) {
166 /* Enable breakpoints/watchpoints */
167 vcpu_sys_reg(vcpu, MDSCR_EL1) |= DBG_MDSCR_MDE;
168
169 vcpu->arch.debug_ptr = &vcpu->arch.external_debug_state;
170 vcpu->arch.debug_flags |= KVM_ARM64_DEBUG_DIRTY;
171 trap_debug = true;
172
173 trace_kvm_arm_set_regset("BKPTS", get_num_brps(),
174 &vcpu->arch.debug_ptr->dbg_bcr[0],
175 &vcpu->arch.debug_ptr->dbg_bvr[0]);
176
177 trace_kvm_arm_set_regset("WAPTS", get_num_wrps(),
178 &vcpu->arch.debug_ptr->dbg_wcr[0],
179 &vcpu->arch.debug_ptr->dbg_wvr[0]);
180 }
181 }
182
183 BUG_ON(!vcpu->guest_debug &&
184 vcpu->arch.debug_ptr != &vcpu->arch.vcpu_debug_state);
185
186 /* Trap debug register access */
187 if (trap_debug)
188 vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA;
189
190 trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.mdcr_el2);
191 trace_kvm_arm_set_dreg32("MDSCR_EL1", vcpu_sys_reg(vcpu, MDSCR_EL1));
192}
193
194void kvm_arm_clear_debug(struct kvm_vcpu *vcpu)
195{
196 trace_kvm_arm_clear_debug(vcpu->guest_debug);
197
198 if (vcpu->guest_debug) {
199 restore_guest_debug_regs(vcpu);
200
201 /*
202 * If we were using HW debug we need to restore the
203 * debug_ptr to the guest debug state.
204 */
205 if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) {
206 kvm_arm_reset_debug_ptr(vcpu);
207
208 trace_kvm_arm_set_regset("BKPTS", get_num_brps(),
209 &vcpu->arch.debug_ptr->dbg_bcr[0],
210 &vcpu->arch.debug_ptr->dbg_bvr[0]);
211
212 trace_kvm_arm_set_regset("WAPTS", get_num_wrps(),
213 &vcpu->arch.debug_ptr->dbg_wcr[0],
214 &vcpu->arch.debug_ptr->dbg_wvr[0]);
215 }
216 }
217}