From: Andi Kleen <[email protected]> Add C intrinsics and assembler macros for the new RD/WR FS/GS BASE instructions.
Very straight forward. Used in followon patch. [luto: rename the variables from fs and gs to fsbase and gsbase and make fsgs.h safe to include on 32-bit kernels.] v2: Use __always_inline Signed-off-by: Andi Kleen <[email protected]> Signed-off-by: Andy Lutomirski <[email protected]> [chang: Replace new instruction macros with GAS-compatible and renaming. Note: if GCC supports it, we can add -mfsgsbase to CFLAGS and use the builtins here for extra performance.] Signed-off-by: Chang S. Bae <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Ingo Molnar <[email protected]> --- arch/x86/include/asm/fsgsbase.h | 70 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 70 insertions(+) diff --git a/arch/x86/include/asm/fsgsbase.h b/arch/x86/include/asm/fsgsbase.h index 0d4fbef..ed42015 100644 --- a/arch/x86/include/asm/fsgsbase.h +++ b/arch/x86/include/asm/fsgsbase.h @@ -18,6 +18,42 @@ unsigned long read_task_gsbase(struct task_struct *task); int write_task_fsbase(struct task_struct *task, unsigned long fsbase); int write_task_gsbase(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(".byte 0xf3, 0x48, 0x0f, 0xae, 0xc0 # rdfsbaseq %%rax" + : "=a" (fsbase) + :: "memory"); + return fsbase; +} + +static __always_inline unsigned long rdgsbase(void) +{ + unsigned long gsbase; + + asm volatile(".byte 0xf3, 0x48, 0x0f, 0xae, 0xc8 # rdgsbaseq %%rax;" + : "=a" (gsbase) + :: "memory"); + return gsbase; +} + +static __always_inline void wrfsbase(unsigned long fsbase) +{ + asm volatile(".byte 0xf3, 0x48, 0x0f, 0xae, 0xd0 # wrfsbaseq %%rax" + :: "a" (fsbase) + : "memory"); +} + +static __always_inline void wrgsbase(unsigned long gsbase) +{ + asm volatile(".byte 0xf3, 0x48, 0x0f, 0xae, 0xd8 # wrgsbaseq %%rax;" + :: "a" (gsbase) + : "memory"); +} + /* Helper functions for reading/writing FS/GS base */ static inline unsigned long read_fsbase(void) @@ -42,6 +78,40 @@ void write_inactive_gsbase(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 */ -- 2.7.4
