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Diffstat (limited to 'arch/x86/include/asm/fsgsbase.h')
-rw-r--r-- | arch/x86/include/asm/fsgsbase.h | 85 |
1 files changed, 85 insertions, 0 deletions
diff --git a/arch/x86/include/asm/fsgsbase.h b/arch/x86/include/asm/fsgsbase.h new file mode 100644 index 0000000000..35cff5f2be --- /dev/null +++ b/arch/x86/include/asm/fsgsbase.h @@ -0,0 +1,85 @@ +/* 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 */ |