1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _ASM_X86_DEBUGREG_H
3#define _ASM_X86_DEBUGREG_H
4
5#include <linux/bug.h>
6#include <linux/percpu.h>
7#include <uapi/asm/debugreg.h>
8
9#include <asm/cpufeature.h>
10#include <asm/msr.h>
11
12/*
13 * Define bits that are always set to 1 in DR7, only bit 10 is
14 * architecturally reserved to '1'.
15 *
16 * This is also the init/reset value for DR7.
17 */
18#define DR7_FIXED_1 0x00000400
19
20DECLARE_PER_CPU(unsigned long, cpu_dr7);
21
22#ifndef CONFIG_PARAVIRT_XXL
23/*
24 * These special macros can be used to get or set a debugging register
25 */
26#define get_debugreg(var, register) \
27 (var) = native_get_debugreg(register)
28#define set_debugreg(value, register) \
29 native_set_debugreg(register, value)
30#endif
31
32static __always_inline unsigned long native_get_debugreg(int regno)
33{
34 unsigned long val;
35
36 switch (regno) {
37 case 0:
38 asm("mov %%db0, %0" :"=r" (val));
39 break;
40 case 1:
41 asm("mov %%db1, %0" :"=r" (val));
42 break;
43 case 2:
44 asm("mov %%db2, %0" :"=r" (val));
45 break;
46 case 3:
47 asm("mov %%db3, %0" :"=r" (val));
48 break;
49 case 6:
50 asm("mov %%db6, %0" :"=r" (val));
51 break;
52 case 7:
53 /*
54 * Use "asm volatile" for DR7 reads to forbid re-ordering them
55 * with other code.
56 *
57 * This is needed because a DR7 access can cause a #VC exception
58 * when running under SEV-ES. Taking a #VC exception is not a
59 * safe thing to do just anywhere in the entry code and
60 * re-ordering might place the access into an unsafe location.
61 *
62 * This happened in the NMI handler, where the DR7 read was
63 * re-ordered to happen before the call to sev_es_ist_enter(),
64 * causing stack recursion.
65 */
66 asm volatile("mov %%db7, %0" : "=r" (val));
67 break;
68 default:
69 BUG();
70 }
71 return val;
72}
73
74static __always_inline void native_set_debugreg(int regno, unsigned long value)
75{
76 switch (regno) {
77 case 0:
78 asm("mov %0, %%db0" ::"r" (value));
79 break;
80 case 1:
81 asm("mov %0, %%db1" ::"r" (value));
82 break;
83 case 2:
84 asm("mov %0, %%db2" ::"r" (value));
85 break;
86 case 3:
87 asm("mov %0, %%db3" ::"r" (value));
88 break;
89 case 6:
90 asm("mov %0, %%db6" ::"r" (value));
91 break;
92 case 7:
93 /*
94 * Use "asm volatile" for DR7 writes to forbid re-ordering them
95 * with other code.
96 *
97 * While is didn't happen with a DR7 write (see the DR7 read
98 * comment above which explains where it happened), add the
99 * "asm volatile" here too to avoid similar problems in the
100 * future.
101 */
102 asm volatile("mov %0, %%db7" ::"r" (value));
103 break;
104 default:
105 BUG();
106 }
107}
108
109static inline void hw_breakpoint_disable(void)
110{
111 /* Reset the control register for HW Breakpoint */
112 set_debugreg(DR7_FIXED_1, reg: 7);
113
114 /* Zero-out the individual HW breakpoint address registers */
115 set_debugreg(val: 0UL, reg: 0);
116 set_debugreg(val: 0UL, reg: 1);
117 set_debugreg(val: 0UL, reg: 2);
118 set_debugreg(val: 0UL, reg: 3);
119}
120
121static __always_inline bool hw_breakpoint_active(void)
122{
123 return __this_cpu_read(cpu_dr7) & DR_GLOBAL_ENABLE_MASK;
124}
125
126extern void hw_breakpoint_restore(void);
127
128static __always_inline unsigned long local_db_save(void)
129{
130 unsigned long dr7;
131
132 if (static_cpu_has(X86_FEATURE_HYPERVISOR) && !hw_breakpoint_active())
133 return 0;
134
135 get_debugreg(dr7, 7);
136
137 /* Architecturally set bit */
138 dr7 &= ~DR7_FIXED_1;
139 if (dr7)
140 set_debugreg(DR7_FIXED_1, reg: 7);
141
142 /*
143 * Ensure the compiler doesn't lower the above statements into
144 * the critical section; disabling breakpoints late would not
145 * be good.
146 */
147 barrier();
148
149 return dr7;
150}
151
152static __always_inline void local_db_restore(unsigned long dr7)
153{
154 /*
155 * Ensure the compiler doesn't raise this statement into
156 * the critical section; enabling breakpoints early would
157 * not be good.
158 */
159 barrier();
160 if (dr7)
161 set_debugreg(val: dr7, reg: 7);
162}
163
164#ifdef CONFIG_CPU_SUP_AMD
165extern void amd_set_dr_addr_mask(unsigned long mask, unsigned int dr);
166extern unsigned long amd_get_dr_addr_mask(unsigned int dr);
167#else
168static inline void amd_set_dr_addr_mask(unsigned long mask, unsigned int dr) { }
169static inline unsigned long amd_get_dr_addr_mask(unsigned int dr)
170{
171 return 0;
172}
173#endif
174
175static inline unsigned long get_debugctlmsr(void)
176{
177 unsigned long debugctlmsr = 0;
178
179#ifndef CONFIG_X86_DEBUGCTLMSR
180 if (boot_cpu_data.x86 < 6)
181 return 0;
182#endif
183 rdmsrq(MSR_IA32_DEBUGCTLMSR, debugctlmsr);
184
185 return debugctlmsr;
186}
187
188static inline void update_debugctlmsr(unsigned long debugctlmsr)
189{
190#ifndef CONFIG_X86_DEBUGCTLMSR
191 if (boot_cpu_data.x86 < 6)
192 return;
193#endif
194 wrmsrq(MSR_IA32_DEBUGCTLMSR, val: debugctlmsr);
195}
196
197#endif /* _ASM_X86_DEBUGREG_H */
198

source code of linux/arch/x86/include/asm/debugreg.h