2 * Debug and Guest Debug support
4 * Copyright (C) 2015 - Linaro Ltd
5 * Author: Alex Bennée <alex.bennee@linaro.org>
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.
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.
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/>.
20 #include <linux/kvm_host.h>
21 #include <linux/hw_breakpoint.h>
23 #include <asm/debug-monitors.h>
24 #include <asm/kvm_asm.h>
25 #include <asm/kvm_arm.h>
26 #include <asm/kvm_emulate.h>
30 /* These are the bits of MDSCR_EL1 we may manipulate */
31 #define MDSCR_EL1_DEBUG_MASK (DBG_MDSCR_SS | \
35 static DEFINE_PER_CPU(u32, mdcr_el2);
38 * save/restore_guest_debug_regs
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.
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.
47 static void save_guest_debug_regs(struct kvm_vcpu *vcpu)
49 u64 val = vcpu_read_sys_reg(vcpu, MDSCR_EL1);
51 vcpu->arch.guest_debug_preserved.mdscr_el1 = val;
53 trace_kvm_arm_set_dreg32("Saved MDSCR_EL1",
54 vcpu->arch.guest_debug_preserved.mdscr_el1);
57 static void restore_guest_debug_regs(struct kvm_vcpu *vcpu)
59 u64 val = vcpu->arch.guest_debug_preserved.mdscr_el1;
61 vcpu_write_sys_reg(vcpu, val, MDSCR_EL1);
63 trace_kvm_arm_set_dreg32("Restored MDSCR_EL1",
64 vcpu_read_sys_reg(vcpu, MDSCR_EL1));
68 * kvm_arm_init_debug - grab what we need for debug
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.
74 * It is called once per-cpu during CPU hyp initialisation.
77 void kvm_arm_init_debug(void)
79 __this_cpu_write(mdcr_el2, kvm_call_hyp(__kvm_get_mdcr_el2));
83 * kvm_arm_setup_mdcr_el2 - configure vcpu mdcr_el2 value
85 * @vcpu: the vcpu pointer
87 * This ensures we will trap 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 * - Self-hosted Trace Filter controls (MDCR_EL2_TTRF)
94 static void kvm_arm_setup_mdcr_el2(struct kvm_vcpu *vcpu)
97 * This also clears MDCR_EL2_E2PB_MASK to disable guest access
98 * to the profiling buffer.
100 vcpu->arch.mdcr_el2 = __this_cpu_read(mdcr_el2) & MDCR_EL2_HPMN_MASK;
101 vcpu->arch.mdcr_el2 |= (MDCR_EL2_TPM |
108 /* Is the VM being debugged by userspace? */
109 if (vcpu->guest_debug)
110 /* Route all software debug exceptions to EL2 */
111 vcpu->arch.mdcr_el2 |= MDCR_EL2_TDE;
114 * Trap debug register access when one of the following is true:
115 * - Userspace is using the hardware to debug the guest
116 * (KVM_GUESTDBG_USE_HW is set).
117 * - The guest is not using debug (KVM_ARM64_DEBUG_DIRTY is clear).
119 if ((vcpu->guest_debug & KVM_GUESTDBG_USE_HW) ||
120 !(vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY))
121 vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA;
123 trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.mdcr_el2);
127 * kvm_arm_vcpu_init_debug - setup vcpu debug traps
129 * @vcpu: the vcpu pointer
131 * Set vcpu initial mdcr_el2 value.
133 void kvm_arm_vcpu_init_debug(struct kvm_vcpu *vcpu)
136 kvm_arm_setup_mdcr_el2(vcpu);
141 * kvm_arm_reset_debug_ptr - reset the debug ptr to point to the vcpu state
144 void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu)
146 vcpu->arch.debug_ptr = &vcpu->arch.vcpu_debug_state;
150 * kvm_arm_setup_debug - set up debug related stuff
152 * @vcpu: the vcpu pointer
154 * This is called before each entry into the hypervisor to setup any
155 * debug related registers.
157 * Additionally, KVM only traps guest accesses to the debug registers if
158 * the guest is not actively using them (see the KVM_ARM64_DEBUG_DIRTY
159 * flag on vcpu->arch.flags). Since the guest must not interfere
160 * with the hardware state when debugging the guest, we must ensure that
161 * trapping is enabled whenever we are debugging the guest using the
165 void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
167 unsigned long mdscr, orig_mdcr_el2 = vcpu->arch.mdcr_el2;
169 trace_kvm_arm_setup_debug(vcpu, vcpu->guest_debug);
171 kvm_arm_setup_mdcr_el2(vcpu);
173 /* Is Guest debugging in effect? */
174 if (vcpu->guest_debug) {
175 /* Save guest debug state */
176 save_guest_debug_regs(vcpu);
179 * Single Step (ARM ARM D2.12.3 The software step state
182 * If we are doing Single Step we need to manipulate
183 * the guest's MDSCR_EL1.SS and PSTATE.SS. Once the
184 * step has occurred the hypervisor will trap the
185 * debug exception and we return to userspace.
187 * If the guest attempts to single step its userspace
188 * we would have to deal with a trapped exception
189 * while in the guest kernel. Because this would be
190 * hard to unwind we suppress the guest's ability to
191 * do so by masking MDSCR_EL.SS.
193 * This confuses guest debuggers which use
194 * single-step behind the scenes but everything
195 * returns to normal once the host is no longer
196 * debugging the system.
198 if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
199 *vcpu_cpsr(vcpu) |= DBG_SPSR_SS;
200 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1);
201 mdscr |= DBG_MDSCR_SS;
202 vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1);
204 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1);
205 mdscr &= ~DBG_MDSCR_SS;
206 vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1);
209 trace_kvm_arm_set_dreg32("SPSR_EL2", *vcpu_cpsr(vcpu));
212 * HW Breakpoints and watchpoints
214 * We simply switch the debug_ptr to point to our new
215 * external_debug_state which has been populated by the
216 * debug ioctl. The existing KVM_ARM64_DEBUG_DIRTY
217 * mechanism ensures the registers are updated on the
220 if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) {
221 /* Enable breakpoints/watchpoints */
222 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1);
223 mdscr |= DBG_MDSCR_MDE;
224 vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1);
226 vcpu->arch.debug_ptr = &vcpu->arch.external_debug_state;
227 vcpu->arch.flags |= KVM_ARM64_DEBUG_DIRTY;
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]);
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]);
239 BUG_ON(!vcpu->guest_debug &&
240 vcpu->arch.debug_ptr != &vcpu->arch.vcpu_debug_state);
242 /* If KDE or MDE are set, perform a full save/restore cycle. */
243 if (vcpu_read_sys_reg(vcpu, MDSCR_EL1) & (DBG_MDSCR_KDE | DBG_MDSCR_MDE))
244 vcpu->arch.flags |= KVM_ARM64_DEBUG_DIRTY;
246 /* Write mdcr_el2 changes since vcpu_load on VHE systems */
247 if (has_vhe() && orig_mdcr_el2 != vcpu->arch.mdcr_el2)
248 write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2);
250 trace_kvm_arm_set_dreg32("MDSCR_EL1", vcpu_read_sys_reg(vcpu, MDSCR_EL1));
253 void kvm_arm_clear_debug(struct kvm_vcpu *vcpu)
255 trace_kvm_arm_clear_debug(vcpu->guest_debug);
257 if (vcpu->guest_debug) {
258 restore_guest_debug_regs(vcpu);
261 * If we were using HW debug we need to restore the
262 * debug_ptr to the guest debug state.
264 if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) {
265 kvm_arm_reset_debug_ptr(vcpu);
267 trace_kvm_arm_set_regset("BKPTS", get_num_brps(),
268 &vcpu->arch.debug_ptr->dbg_bcr[0],
269 &vcpu->arch.debug_ptr->dbg_bvr[0]);
271 trace_kvm_arm_set_regset("WAPTS", get_num_wrps(),
272 &vcpu->arch.debug_ptr->dbg_wcr[0],
273 &vcpu->arch.debug_ptr->dbg_wvr[0]);
280 * After successfully emulating an instruction, we might want to
281 * return to user space with a KVM_EXIT_DEBUG. We can only do this
282 * once the emulation is complete, though, so for userspace emulations
283 * we have to wait until we have re-entered KVM before calling this
286 * Return true (and set exit_reason) to return to userspace or false
287 * if no further action is required.
289 bool kvm_arm_handle_step_debug(struct kvm_vcpu *vcpu, struct kvm_run *run)
291 if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
292 run->exit_reason = KVM_EXIT_DEBUG;
293 run->debug.arch.hsr = ESR_ELx_EC_SOFTSTP_LOW << ESR_ELx_EC_SHIFT;