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
24 static 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 */
save_guest_debug_regs(struct kvm_vcpu * vcpu)36 static 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
restore_guest_debug_regs(struct kvm_vcpu * vcpu)46 static 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
kvm_arm_init_debug(void)66 void 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_setup_mdcr_el2 - configure vcpu mdcr_el2 value
73 *
74 * @vcpu: the vcpu pointer
75 *
76 * This ensures we will trap access to:
77 * - Performance monitors (MDCR_EL2_TPM/MDCR_EL2_TPMCR)
78 * - Debug ROM Address (MDCR_EL2_TDRA)
79 * - OS related registers (MDCR_EL2_TDOSA)
80 * - Statistical profiler (MDCR_EL2_TPMS/MDCR_EL2_E2PB)
81 * - Self-hosted Trace Filter controls (MDCR_EL2_TTRF)
82 */
kvm_arm_setup_mdcr_el2(struct kvm_vcpu * vcpu)83 static void kvm_arm_setup_mdcr_el2(struct kvm_vcpu *vcpu)
84 {
85 /*
86 * This also clears MDCR_EL2_E2PB_MASK to disable guest access
87 * to the profiling buffer.
88 */
89 vcpu->arch.mdcr_el2 = __this_cpu_read(mdcr_el2) & MDCR_EL2_HPMN_MASK;
90 vcpu->arch.mdcr_el2 |= (MDCR_EL2_TPM |
91 MDCR_EL2_TPMS |
92 MDCR_EL2_TTRF |
93 MDCR_EL2_TPMCR |
94 MDCR_EL2_TDRA |
95 MDCR_EL2_TDOSA);
96
97 /* Is the VM being debugged by userspace? */
98 if (vcpu->guest_debug)
99 /* Route all software debug exceptions to EL2 */
100 vcpu->arch.mdcr_el2 |= MDCR_EL2_TDE;
101
102 /*
103 * Trap debug register access when one of the following is true:
104 * - Userspace is using the hardware to debug the guest
105 * (KVM_GUESTDBG_USE_HW is set).
106 * - The guest is not using debug (KVM_ARM64_DEBUG_DIRTY is clear).
107 */
108 if ((vcpu->guest_debug & KVM_GUESTDBG_USE_HW) ||
109 !(vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY))
110 vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA;
111
112 trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.mdcr_el2);
113 }
114
115 /**
116 * kvm_arm_vcpu_init_debug - setup vcpu debug traps
117 *
118 * @vcpu: the vcpu pointer
119 *
120 * Set vcpu initial mdcr_el2 value.
121 */
kvm_arm_vcpu_init_debug(struct kvm_vcpu * vcpu)122 void kvm_arm_vcpu_init_debug(struct kvm_vcpu *vcpu)
123 {
124 preempt_disable();
125 kvm_arm_setup_mdcr_el2(vcpu);
126 preempt_enable();
127 }
128
129 /**
130 * kvm_arm_reset_debug_ptr - reset the debug ptr to point to the vcpu state
131 */
132
kvm_arm_reset_debug_ptr(struct kvm_vcpu * vcpu)133 void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu)
134 {
135 vcpu->arch.debug_ptr = &vcpu->arch.vcpu_debug_state;
136 }
137
138 /**
139 * kvm_arm_setup_debug - set up debug related stuff
140 *
141 * @vcpu: the vcpu pointer
142 *
143 * This is called before each entry into the hypervisor to setup any
144 * debug related registers. Currently this just ensures we will trap
145 * access to:
146 * - Performance monitors (MDCR_EL2_TPM/MDCR_EL2_TPMCR)
147 * - Debug ROM Address (MDCR_EL2_TDRA)
148 * - OS related registers (MDCR_EL2_TDOSA)
149 * - Statistical profiler (MDCR_EL2_TPMS/MDCR_EL2_E2PB)
150 * - Self-hosted Trace (MDCR_EL2_TTRF/MDCR_EL2_E2TB)
151 *
152 * Additionally, KVM only traps guest accesses to the debug registers if
153 * the guest is not actively using them (see the KVM_ARM64_DEBUG_DIRTY
154 * flag on vcpu->arch.flags). Since the guest must not interfere
155 * with the hardware state when debugging the guest, we must ensure that
156 * trapping is enabled whenever we are debugging the guest using the
157 * debug registers.
158 */
159
kvm_arm_setup_debug(struct kvm_vcpu * vcpu)160 void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
161 {
162 unsigned long mdscr, orig_mdcr_el2 = vcpu->arch.mdcr_el2;
163
164 trace_kvm_arm_setup_debug(vcpu, vcpu->guest_debug);
165
166 kvm_arm_setup_mdcr_el2(vcpu);
167
168 /* Is Guest debugging in effect? */
169 if (vcpu->guest_debug) {
170 /* Save guest debug state */
171 save_guest_debug_regs(vcpu);
172
173 /*
174 * Single Step (ARM ARM D2.12.3 The software step state
175 * machine)
176 *
177 * If we are doing Single Step we need to manipulate
178 * the guest's MDSCR_EL1.SS and PSTATE.SS. Once the
179 * step has occurred the hypervisor will trap the
180 * debug exception and we return to userspace.
181 *
182 * If the guest attempts to single step its userspace
183 * we would have to deal with a trapped exception
184 * while in the guest kernel. Because this would be
185 * hard to unwind we suppress the guest's ability to
186 * do so by masking MDSCR_EL.SS.
187 *
188 * This confuses guest debuggers which use
189 * single-step behind the scenes but everything
190 * returns to normal once the host is no longer
191 * debugging the system.
192 */
193 if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
194 *vcpu_cpsr(vcpu) |= DBG_SPSR_SS;
195 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1);
196 mdscr |= DBG_MDSCR_SS;
197 vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1);
198 } else {
199 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1);
200 mdscr &= ~DBG_MDSCR_SS;
201 vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1);
202 }
203
204 trace_kvm_arm_set_dreg32("SPSR_EL2", *vcpu_cpsr(vcpu));
205
206 /*
207 * HW Breakpoints and watchpoints
208 *
209 * We simply switch the debug_ptr to point to our new
210 * external_debug_state which has been populated by the
211 * debug ioctl. The existing KVM_ARM64_DEBUG_DIRTY
212 * mechanism ensures the registers are updated on the
213 * world switch.
214 */
215 if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) {
216 /* Enable breakpoints/watchpoints */
217 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1);
218 mdscr |= DBG_MDSCR_MDE;
219 vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1);
220
221 vcpu->arch.debug_ptr = &vcpu->arch.external_debug_state;
222 vcpu->arch.flags |= KVM_ARM64_DEBUG_DIRTY;
223
224 trace_kvm_arm_set_regset("BKPTS", get_num_brps(),
225 &vcpu->arch.debug_ptr->dbg_bcr[0],
226 &vcpu->arch.debug_ptr->dbg_bvr[0]);
227
228 trace_kvm_arm_set_regset("WAPTS", get_num_wrps(),
229 &vcpu->arch.debug_ptr->dbg_wcr[0],
230 &vcpu->arch.debug_ptr->dbg_wvr[0]);
231 }
232 }
233
234 BUG_ON(!vcpu->guest_debug &&
235 vcpu->arch.debug_ptr != &vcpu->arch.vcpu_debug_state);
236
237 /* If KDE or MDE are set, perform a full save/restore cycle. */
238 if (vcpu_read_sys_reg(vcpu, MDSCR_EL1) & (DBG_MDSCR_KDE | DBG_MDSCR_MDE))
239 vcpu->arch.flags |= KVM_ARM64_DEBUG_DIRTY;
240
241 /* Write mdcr_el2 changes since vcpu_load on VHE systems */
242 if (has_vhe() && orig_mdcr_el2 != vcpu->arch.mdcr_el2)
243 write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2);
244
245 trace_kvm_arm_set_dreg32("MDSCR_EL1", vcpu_read_sys_reg(vcpu, MDSCR_EL1));
246 }
247
kvm_arm_clear_debug(struct kvm_vcpu * vcpu)248 void kvm_arm_clear_debug(struct kvm_vcpu *vcpu)
249 {
250 trace_kvm_arm_clear_debug(vcpu->guest_debug);
251
252 if (vcpu->guest_debug) {
253 restore_guest_debug_regs(vcpu);
254
255 /*
256 * If we were using HW debug we need to restore the
257 * debug_ptr to the guest debug state.
258 */
259 if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) {
260 kvm_arm_reset_debug_ptr(vcpu);
261
262 trace_kvm_arm_set_regset("BKPTS", get_num_brps(),
263 &vcpu->arch.debug_ptr->dbg_bcr[0],
264 &vcpu->arch.debug_ptr->dbg_bvr[0]);
265
266 trace_kvm_arm_set_regset("WAPTS", get_num_wrps(),
267 &vcpu->arch.debug_ptr->dbg_wcr[0],
268 &vcpu->arch.debug_ptr->dbg_wvr[0]);
269 }
270 }
271 }
272
kvm_arch_vcpu_load_debug_state_flags(struct kvm_vcpu * vcpu)273 void kvm_arch_vcpu_load_debug_state_flags(struct kvm_vcpu *vcpu)
274 {
275 u64 dfr0;
276
277 /* For VHE, there is nothing to do */
278 if (has_vhe())
279 return;
280
281 dfr0 = read_sysreg(id_aa64dfr0_el1);
282 /*
283 * If SPE is present on this CPU and is available at current EL,
284 * we may need to check if the host state needs to be saved.
285 */
286 if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_PMSVER_SHIFT) &&
287 !(read_sysreg_s(SYS_PMBIDR_EL1) & BIT(SYS_PMBIDR_EL1_P_SHIFT)))
288 vcpu->arch.flags |= KVM_ARM64_DEBUG_STATE_SAVE_SPE;
289
290 /* Check if we have TRBE implemented and available at the host */
291 if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_TRBE_SHIFT) &&
292 !(read_sysreg_s(SYS_TRBIDR_EL1) & TRBIDR_PROG))
293 vcpu->arch.flags |= KVM_ARM64_DEBUG_STATE_SAVE_TRBE;
294 }
295
kvm_arch_vcpu_put_debug_state_flags(struct kvm_vcpu * vcpu)296 void kvm_arch_vcpu_put_debug_state_flags(struct kvm_vcpu *vcpu)
297 {
298 vcpu->arch.flags &= ~(KVM_ARM64_DEBUG_STATE_SAVE_SPE |
299 KVM_ARM64_DEBUG_STATE_SAVE_TRBE);
300 }
301