Merge tag 'v4.4.63' into linux-linaro-lsk-v4.4
[firefly-linux-kernel-4.4.55.git] / arch / arm64 / kvm / debug.c
1 /*
2  * Debug and Guest Debug support
3  *
4  * Copyright (C) 2015 - Linaro Ltd
5  * Author: Alex BennĂ©e <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
35 static 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  */
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);
50
51         trace_kvm_arm_set_dreg32("Saved MDSCR_EL1",
52                                 vcpu->arch.guest_debug_preserved.mdscr_el1);
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;
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
73 void 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
82 void 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
107 void 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
194 void 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 }