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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 u64 val = vcpu_read_sys_reg(vcpu, MDSCR_EL1);
50
51 vcpu->arch.guest_debug_preserved.mdscr_el1 = val;
52
53 trace_kvm_arm_set_dreg32("Saved MDSCR_EL1",
54 vcpu->arch.guest_debug_preserved.mdscr_el1);
55}
56
57static void restore_guest_debug_regs(struct kvm_vcpu *vcpu)
58{
59 u64 val = vcpu->arch.guest_debug_preserved.mdscr_el1;
60
61 vcpu_write_sys_reg(vcpu, val, MDSCR_EL1);
62
63 trace_kvm_arm_set_dreg32("Restored MDSCR_EL1",
64 vcpu_read_sys_reg(vcpu, MDSCR_EL1));
65}
66
67/**
68 * kvm_arm_init_debug - grab what we need for debug
69 *
70 * Currently the sole task of this function is to retrieve the initial
71 * value of mdcr_el2 so we can preserve MDCR_EL2.HPMN which has
72 * presumably been set-up by some knowledgeable bootcode.
73 *
74 * It is called once per-cpu during CPU hyp initialisation.
75 */
76
77void kvm_arm_init_debug(void)
78{
79 __this_cpu_write(mdcr_el2, kvm_call_hyp(__kvm_get_mdcr_el2));
80}
81
82/**
83 * kvm_arm_reset_debug_ptr - reset the debug ptr to point to the vcpu state
84 */
85
86void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu)
87{
88 vcpu->arch.debug_ptr = &vcpu->arch.vcpu_debug_state;
89}
90
91/**
92 * kvm_arm_setup_debug - set up debug related stuff
93 *
94 * @vcpu: the vcpu pointer
95 *
96 * This is called before each entry into the hypervisor to setup any
97 * debug related registers. Currently this just ensures we will trap
98 * access to:
99 * - Performance monitors (MDCR_EL2_TPM/MDCR_EL2_TPMCR)
100 * - Debug ROM Address (MDCR_EL2_TDRA)
101 * - OS related registers (MDCR_EL2_TDOSA)
102 * - Statistical profiler (MDCR_EL2_TPMS/MDCR_EL2_E2PB)
103 *
104 * Additionally, KVM only traps guest accesses to the debug registers if
105 * the guest is not actively using them (see the KVM_ARM64_DEBUG_DIRTY
106 * flag on vcpu->arch.debug_flags). Since the guest must not interfere
107 * with the hardware state when debugging the guest, we must ensure that
108 * trapping is enabled whenever we are debugging the guest using the
109 * debug registers.
110 */
111
112void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
113{
114 bool trap_debug = !(vcpu->arch.debug_flags & KVM_ARM64_DEBUG_DIRTY);
115 unsigned long mdscr;
116
117 trace_kvm_arm_setup_debug(vcpu, vcpu->guest_debug);
118
119 /*
120 * This also clears MDCR_EL2_E2PB_MASK to disable guest access
121 * to the profiling buffer.
122 */
123 vcpu->arch.mdcr_el2 = __this_cpu_read(mdcr_el2) & MDCR_EL2_HPMN_MASK;
124 vcpu->arch.mdcr_el2 |= (MDCR_EL2_TPM |
125 MDCR_EL2_TPMS |
126 MDCR_EL2_TPMCR |
127 MDCR_EL2_TDRA |
128 MDCR_EL2_TDOSA);
129
130 /* Is Guest debugging in effect? */
131 if (vcpu->guest_debug) {
132 /* Route all software debug exceptions to EL2 */
133 vcpu->arch.mdcr_el2 |= MDCR_EL2_TDE;
134
135 /* Save guest debug state */
136 save_guest_debug_regs(vcpu);
137
138 /*
139 * Single Step (ARM ARM D2.12.3 The software step state
140 * machine)
141 *
142 * If we are doing Single Step we need to manipulate
143 * the guest's MDSCR_EL1.SS and PSTATE.SS. Once the
144 * step has occurred the hypervisor will trap the
145 * debug exception and we return to userspace.
146 *
147 * If the guest attempts to single step its userspace
148 * we would have to deal with a trapped exception
149 * while in the guest kernel. Because this would be
150 * hard to unwind we suppress the guest's ability to
151 * do so by masking MDSCR_EL.SS.
152 *
153 * This confuses guest debuggers which use
154 * single-step behind the scenes but everything
155 * returns to normal once the host is no longer
156 * debugging the system.
157 */
158 if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
159 *vcpu_cpsr(vcpu) |= DBG_SPSR_SS;
160 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1);
161 mdscr |= DBG_MDSCR_SS;
162 vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1);
163 } else {
164 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1);
165 mdscr &= ~DBG_MDSCR_SS;
166 vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1);
167 }
168
169 trace_kvm_arm_set_dreg32("SPSR_EL2", *vcpu_cpsr(vcpu));
170
171 /*
172 * HW Breakpoints and watchpoints
173 *
174 * We simply switch the debug_ptr to point to our new
175 * external_debug_state which has been populated by the
176 * debug ioctl. The existing KVM_ARM64_DEBUG_DIRTY
177 * mechanism ensures the registers are updated on the
178 * world switch.
179 */
180 if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) {
181 /* Enable breakpoints/watchpoints */
182 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1);
183 mdscr |= DBG_MDSCR_MDE;
184 vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1);
185
186 vcpu->arch.debug_ptr = &vcpu->arch.external_debug_state;
187 vcpu->arch.debug_flags |= KVM_ARM64_DEBUG_DIRTY;
188 trap_debug = true;
189
190 trace_kvm_arm_set_regset("BKPTS", get_num_brps(),
191 &vcpu->arch.debug_ptr->dbg_bcr[0],
192 &vcpu->arch.debug_ptr->dbg_bvr[0]);
193
194 trace_kvm_arm_set_regset("WAPTS", get_num_wrps(),
195 &vcpu->arch.debug_ptr->dbg_wcr[0],
196 &vcpu->arch.debug_ptr->dbg_wvr[0]);
197 }
198 }
199
200 BUG_ON(!vcpu->guest_debug &&
201 vcpu->arch.debug_ptr != &vcpu->arch.vcpu_debug_state);
202
203 /* Trap debug register access */
204 if (trap_debug)
205 vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA;
206
207 /* If KDE or MDE are set, perform a full save/restore cycle. */
208 if (vcpu_read_sys_reg(vcpu, MDSCR_EL1) & (DBG_MDSCR_KDE | DBG_MDSCR_MDE))
209 vcpu->arch.debug_flags |= KVM_ARM64_DEBUG_DIRTY;
210
211 trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.mdcr_el2);
212 trace_kvm_arm_set_dreg32("MDSCR_EL1", vcpu_read_sys_reg(vcpu, MDSCR_EL1));
213}
214
215void kvm_arm_clear_debug(struct kvm_vcpu *vcpu)
216{
217 trace_kvm_arm_clear_debug(vcpu->guest_debug);
218
219 if (vcpu->guest_debug) {
220 restore_guest_debug_regs(vcpu);
221
222 /*
223 * If we were using HW debug we need to restore the
224 * debug_ptr to the guest debug state.
225 */
226 if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) {
227 kvm_arm_reset_debug_ptr(vcpu);
228
229 trace_kvm_arm_set_regset("BKPTS", get_num_brps(),
230 &vcpu->arch.debug_ptr->dbg_bcr[0],
231 &vcpu->arch.debug_ptr->dbg_bvr[0]);
232
233 trace_kvm_arm_set_regset("WAPTS", get_num_wrps(),
234 &vcpu->arch.debug_ptr->dbg_wcr[0],
235 &vcpu->arch.debug_ptr->dbg_wvr[0]);
236 }
237 }
238}
239
240
241/*
242 * After successfully emulating an instruction, we might want to
243 * return to user space with a KVM_EXIT_DEBUG. We can only do this
244 * once the emulation is complete, though, so for userspace emulations
245 * we have to wait until we have re-entered KVM before calling this
246 * helper.
247 *
248 * Return true (and set exit_reason) to return to userspace or false
249 * if no further action is required.
250 */
251bool kvm_arm_handle_step_debug(struct kvm_vcpu *vcpu, struct kvm_run *run)
252{
253 if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
254 run->exit_reason = KVM_EXIT_DEBUG;
255 run->debug.arch.hsr = ESR_ELx_EC_SOFTSTP_LOW << ESR_ELx_EC_SHIFT;
256 return true;
257 }
258 return false;
259}
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
24static DEFINE_PER_CPU(u32, 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 */
36static 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
46static 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
66void 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_reset_debug_ptr - reset the debug ptr to point to the vcpu state
73 */
74
75void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu)
76{
77 vcpu->arch.debug_ptr = &vcpu->arch.vcpu_debug_state;
78}
79
80/**
81 * kvm_arm_setup_debug - set up debug related stuff
82 *
83 * @vcpu: the vcpu pointer
84 *
85 * This is called before each entry into the hypervisor to setup any
86 * debug related registers. Currently this just ensures we will trap
87 * access to:
88 * - Performance monitors (MDCR_EL2_TPM/MDCR_EL2_TPMCR)
89 * - Debug ROM Address (MDCR_EL2_TDRA)
90 * - OS related registers (MDCR_EL2_TDOSA)
91 * - Statistical profiler (MDCR_EL2_TPMS/MDCR_EL2_E2PB)
92 *
93 * Additionally, KVM only traps guest accesses to the debug registers if
94 * the guest is not actively using them (see the KVM_ARM64_DEBUG_DIRTY
95 * flag on vcpu->arch.flags). Since the guest must not interfere
96 * with the hardware state when debugging the guest, we must ensure that
97 * trapping is enabled whenever we are debugging the guest using the
98 * debug registers.
99 */
100
101void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
102{
103 bool trap_debug = !(vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY);
104 unsigned long mdscr;
105
106 trace_kvm_arm_setup_debug(vcpu, vcpu->guest_debug);
107
108 /*
109 * This also clears MDCR_EL2_E2PB_MASK to disable guest access
110 * to the profiling buffer.
111 */
112 vcpu->arch.mdcr_el2 = __this_cpu_read(mdcr_el2) & MDCR_EL2_HPMN_MASK;
113 vcpu->arch.mdcr_el2 |= (MDCR_EL2_TPM |
114 MDCR_EL2_TPMS |
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 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1);
150 mdscr |= DBG_MDSCR_SS;
151 vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1);
152 } else {
153 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1);
154 mdscr &= ~DBG_MDSCR_SS;
155 vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1);
156 }
157
158 trace_kvm_arm_set_dreg32("SPSR_EL2", *vcpu_cpsr(vcpu));
159
160 /*
161 * HW Breakpoints and watchpoints
162 *
163 * We simply switch the debug_ptr to point to our new
164 * external_debug_state which has been populated by the
165 * debug ioctl. The existing KVM_ARM64_DEBUG_DIRTY
166 * mechanism ensures the registers are updated on the
167 * world switch.
168 */
169 if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) {
170 /* Enable breakpoints/watchpoints */
171 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1);
172 mdscr |= DBG_MDSCR_MDE;
173 vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1);
174
175 vcpu->arch.debug_ptr = &vcpu->arch.external_debug_state;
176 vcpu->arch.flags |= KVM_ARM64_DEBUG_DIRTY;
177 trap_debug = true;
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]);
186 }
187 }
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;
195
196 /* If KDE or MDE are set, perform a full save/restore cycle. */
197 if (vcpu_read_sys_reg(vcpu, MDSCR_EL1) & (DBG_MDSCR_KDE | DBG_MDSCR_MDE))
198 vcpu->arch.flags |= KVM_ARM64_DEBUG_DIRTY;
199
200 trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.mdcr_el2);
201 trace_kvm_arm_set_dreg32("MDSCR_EL1", vcpu_read_sys_reg(vcpu, MDSCR_EL1));
202}
203
204void kvm_arm_clear_debug(struct kvm_vcpu *vcpu)
205{
206 trace_kvm_arm_clear_debug(vcpu->guest_debug);
207
208 if (vcpu->guest_debug) {
209 restore_guest_debug_regs(vcpu);
210
211 /*
212 * If we were using HW debug we need to restore the
213 * debug_ptr to the guest debug state.
214 */
215 if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) {
216 kvm_arm_reset_debug_ptr(vcpu);
217
218 trace_kvm_arm_set_regset("BKPTS", get_num_brps(),
219 &vcpu->arch.debug_ptr->dbg_bcr[0],
220 &vcpu->arch.debug_ptr->dbg_bvr[0]);
221
222 trace_kvm_arm_set_regset("WAPTS", get_num_wrps(),
223 &vcpu->arch.debug_ptr->dbg_wcr[0],
224 &vcpu->arch.debug_ptr->dbg_wvr[0]);
225 }
226 }
227}