From: Andi Kleen <a...@linux.intel.com> Add C intrinsics and assembler macros for the new FSBASE and GSBASE instructions.
Very straight forward. Used in followon patches. [ luto: Rename the variables from FS and GS to FSBASE and GSBASE and make <asm/fsgsbase.h> safe to include on 32-bit kernels. ] v2: Use __always_inline [ chang: Revise the changelog. Place them in <asm/fsgsbase.h>. Replace the macros with GAS-compatible ones. ] If GCC supports it, we can add -mfsgsbase to CFLAGS and use the builtins here for extra performance. [ chang: Use FSGSBASE instructions directly instead of .byte ] Signed-off-by: Andi Kleen <a...@linux.intel.com> Signed-off-by: Andy Lutomirski <l...@kernel.org> Signed-off-by: Chang S. Bae <chang.seok....@intel.com> Reviewed-by: Andy Lutomirski <l...@kernel.org> # C parts only Cc: H. Peter Anvin <h...@zytor.com> Cc: Thomas Gleixner <t...@linutronix.de> Cc: Ingo Molnar <mi...@kernel.org> Cc: Dave Hansen <dave.han...@linux.intel.com> --- arch/x86/include/asm/fsgsbase.h | 64 +++++++++++++++++++++++++++++++++ 1 file changed, 64 insertions(+) diff --git a/arch/x86/include/asm/fsgsbase.h b/arch/x86/include/asm/fsgsbase.h index bca4c743de77..09b34ee0cfd4 100644 --- a/arch/x86/include/asm/fsgsbase.h +++ b/arch/x86/include/asm/fsgsbase.h @@ -19,6 +19,36 @@ 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"); +} + /* Helper functions for reading/writing FS/GS base */ static inline unsigned long x86_fsbase_read_cpu(void) @@ -51,6 +81,40 @@ static inline void x86_gsbase_write_cpu_inactive(unsigned long gsbase) #endif /* CONFIG_X86_64 */ +#else /* __ASSEMBLY__ */ + +#ifdef CONFIG_X86_64 + +#include <asm/inst.h> + +.macro RDGSBASE opd + REG_TYPE rdgsbase_opd_type \opd + .if rdgsbase_opd_type == REG_TYPE_R64 + R64_NUM rdgsbase_opd \opd + .byte 0xf3 + PFX_REX rdgsbase_opd 0 W = 1 + .else + .error "RDGSBASE: only for 64-bit value" + .endif + .byte 0xf, 0xae + MODRM 0xc0 rdgsbase_opd 1 +.endm + +.macro WRGSBASE opd + REG_TYPE wrgsbase_opd_type \opd + .if wrgsbase_opd_type == REG_TYPE_R64 + R64_NUM wrgsbase_opd \opd + .byte 0xf3 + PFX_REX wrgsbase_opd 0 W = 1 + .else + .error "WRGSBASE: only for 64-bit value" + .endif + .byte 0xf, 0xae + MODRM 0xd0 wrgsbase_opd 1 +.endm + +#endif /* CONFIG_X86_64 */ + #endif /* __ASSEMBLY__ */ #endif /* _ASM_FSGSBASE_H */ -- 2.19.1