1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _ASM_FSGSBASE_H
3 #define _ASM_FSGSBASE_H
4 
5 #ifndef __ASSEMBLY__
6 
7 #ifdef CONFIG_X86_64
8 
9 #include <asm/msr-index.h>
10 
11 /*
12  * Read/write a task's FSBASE or GSBASE. This returns the value that
13  * the FS/GS base would have (if the task were to be resumed). These
14  * work on the current task or on a non-running (typically stopped
15  * ptrace child) task.
16  */
17 extern unsigned long x86_fsbase_read_task(struct task_struct *task);
18 extern unsigned long x86_gsbase_read_task(struct task_struct *task);
19 extern void x86_fsbase_write_task(struct task_struct *task, unsigned long fsbase);
20 extern void x86_gsbase_write_task(struct task_struct *task, unsigned long gsbase);
21 
22 /* Must be protected by X86_FEATURE_FSGSBASE check. */
23 
rdfsbase(void)24 static __always_inline unsigned long rdfsbase(void)
25 {
26 	unsigned long fsbase;
27 
28 	asm volatile("rdfsbase %0" : "=r" (fsbase) :: "memory");
29 
30 	return fsbase;
31 }
32 
rdgsbase(void)33 static __always_inline unsigned long rdgsbase(void)
34 {
35 	unsigned long gsbase;
36 
37 	asm volatile("rdgsbase %0" : "=r" (gsbase) :: "memory");
38 
39 	return gsbase;
40 }
41 
wrfsbase(unsigned long fsbase)42 static __always_inline void wrfsbase(unsigned long fsbase)
43 {
44 	asm volatile("wrfsbase %0" :: "r" (fsbase) : "memory");
45 }
46 
wrgsbase(unsigned long gsbase)47 static __always_inline void wrgsbase(unsigned long gsbase)
48 {
49 	asm volatile("wrgsbase %0" :: "r" (gsbase) : "memory");
50 }
51 
52 #include <asm/cpufeature.h>
53 
54 /* Helper functions for reading/writing FS/GS base */
55 
x86_fsbase_read_cpu(void)56 static inline unsigned long x86_fsbase_read_cpu(void)
57 {
58 	unsigned long fsbase;
59 
60 	if (boot_cpu_has(X86_FEATURE_FSGSBASE))
61 		fsbase = rdfsbase();
62 	else
63 		rdmsrl(MSR_FS_BASE, fsbase);
64 
65 	return fsbase;
66 }
67 
x86_fsbase_write_cpu(unsigned long fsbase)68 static inline void x86_fsbase_write_cpu(unsigned long fsbase)
69 {
70 	if (boot_cpu_has(X86_FEATURE_FSGSBASE))
71 		wrfsbase(fsbase);
72 	else
73 		wrmsrl(MSR_FS_BASE, fsbase);
74 }
75 
76 extern unsigned long x86_gsbase_read_cpu_inactive(void);
77 extern void x86_gsbase_write_cpu_inactive(unsigned long gsbase);
78 extern unsigned long x86_fsgsbase_read_task(struct task_struct *task,
79 					    unsigned short selector);
80 
81 #endif /* CONFIG_X86_64 */
82 
83 #endif /* __ASSEMBLY__ */
84 
85 #endif /* _ASM_FSGSBASE_H */
86