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 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 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 42 static __always_inline void wrfsbase(unsigned long fsbase) 43 { 44 asm volatile("wrfsbase %0" :: "r" (fsbase) : "memory"); 45 } 46 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 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 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