Messages in this thread |  | | From | Andy Lutomirski <> | Date | Fri, 10 Apr 2015 12:07:52 -0700 | Subject | Re: [PATCH 3/8] x86: Add intrinsics/macros for new rd/wr fs/gs base instructions |
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On Fri, Apr 10, 2015 at 8:50 AM, Andi Kleen <andi@firstfloor.org> wrote: > From: Andi Kleen <ak@linux.intel.com> > > Add C intrinsics and assembler macros for the new rd/wr fs/gs base > instructions and for swapgs. > > Very straight forward. Used in followon patch. > > For assembler only a few standard registers used by entry_64.S > are defined. > > Signed-off-by: Andi Kleen <ak@linux.intel.com> > --- > arch/x86/include/asm/fsgs.h | 54 +++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 54 insertions(+) > create mode 100644 arch/x86/include/asm/fsgs.h > > diff --git a/arch/x86/include/asm/fsgs.h b/arch/x86/include/asm/fsgs.h > new file mode 100644 > index 0000000..1df5085 > --- /dev/null > +++ b/arch/x86/include/asm/fsgs.h > @@ -0,0 +1,54 @@ > +#ifndef _ASM_FSGS_H > +#define _ASM_FSGS_H 1 > + > +#ifndef __ASSEMBLY__ > + > +static inline void swapgs(void) > +{ > + asm volatile("swapgs" ::: "memory"); > +} > + > +/* Must be protected by X86_FEATURE_FSGSBASE check. */ > + > +static inline unsigned long rdgsbase(void) > +{ > + unsigned long gs; > + asm volatile(".byte 0xf3,0x48,0x0f,0xae,0xc8 # rdgsbaseq %%rax" > + : "=a" (gs) > + :: "memory"); > + return gs; > +} > + > +static inline unsigned long rdfsbase(void) > +{ > + unsigned long fs; > + asm volatile(".byte 0xf3,0x48,0x0f,0xae,0xc0 # rdfsbaseq %%rax" > + : "=a" (fs) > + :: "memory"); > + return fs; > +} > + > +static inline void wrgsbase(unsigned long gs) > +{ > + asm volatile(".byte 0xf3,0x48,0x0f,0xae,0xd8 # wrgsbaseq %%rax" > + :: "a" (gs) > + : "memory"); > +} > + > +static inline void wrfsbase(unsigned long fs) > +{ > + asm volatile(".byte 0xf3,0x48,0x0f,0xae,0xd0 # wrfsbaseq %%rax" > + :: "a" (fs) > + : "memory"); > +}
I think these should be always_inline. If they somehow fail to get inlined and then get kprobed or traced, bad things will happen.
--Andy
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