arch/x86/include/asm/fsgsbase.h

   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 */