text: /* SPDX-License-Identifier: GPL-2.0 */
  #ifndef _ASM_FSGSBASE_H
  #define _ASM_FSGSBASE_H
  
  #ifndef __ASSEMBLY__
  
  #ifdef CONFIG_X86_64
  
  #include <asm/msr-index.h>
  
  /*
   * Read/write a task's FSBASE or GSBASE. This returns the value that
   * the FS/GS base would have (if the task were to be resumed). These
   * work on the current task or on a non-running (typically stopped
   * ptrace child) task.
   */
  extern unsigned long x86_fsbase_read_task(struct task_struct *task);
  extern unsigned long x86_gsbase_read_task(struct task_struct *task);
  extern void x86_fsbase_write_task(struct task_struct *task, unsigned long fsbase);
  extern void x86_gsbase_write_task(struct task_struct *task, unsigned long gsbase);
  
  /* Must be protected by X86_FEATURE_FSGSBASE check. */
  
  static __always_inline unsigned long rdfsbase(void)
  {
  	unsigned long fsbase;
  
  	asm volatile("rdfsbase %0" : "=r" (fsbase) :: "memory");
  
  	return fsbase;
  }
  
  static __always_inline unsigned long rdgsbase(void)
  {
  	unsigned long gsbase;
  
  	asm volatile("rdgsbase %0" : "=r" (gsbase) :: "memory");
  
  	return gsbase;
  }
  
  static __always_inline void wrfsbase(unsigned long fsbase)
  {
  	asm volatile("wrfsbase %0" :: "r" (fsbase) : "memory");
  }
  
  static __always_inline void wrgsbase(unsigned long gsbase)
  {
  	asm volatile("wrgsbase %0" :: "r" (gsbase) : "memory");
  }
  
  #include <asm/cpufeature.h>
  
  /* Helper functions for reading/writing FS/GS base */
  
  static inline unsigned long x86_fsbase_read_cpu(void)
  {
  	unsigned long fsbase;
  
  	if (boot_cpu_has(X86_FEATURE_FSGSBASE))
  		fsbase = rdfsbase();
  	else
  		rdmsrl(MSR_FS_BASE, fsbase);
  
  	return fsbase;
  }
  
  static inline void x86_fsbase_write_cpu(unsigned long fsbase)
  {
  	if (boot_cpu_has(X86_FEATURE_FSGSBASE))
  		wrfsbase(fsbase);
  	else
  		wrmsrl(MSR_FS_BASE, fsbase);
  }
  
  extern unsigned long x86_gsbase_read_cpu_inactive(void);
  extern void x86_gsbase_write_cpu_inactive(unsigned long gsbase);
  extern unsigned long x86_fsgsbase_read_task(struct task_struct *task,
  					    unsigned short selector);
  
  #endif /* CONFIG_X86_64 */
  
  #endif /* __ASSEMBLY__ */
  
  #endif /* _ASM_FSGSBASE_H */
  