linux-kernel - Re: [PATCH 3/7] x86: Add C intrinsics for new rd/wr fs/gs base instructions

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Message-ID: <20140429141058.GC11349@phenom.dumpdata.com>
Date:	Tue, 29 Apr 2014 10:10:58 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	x86@...nel.org, linux-kernel@...r.kernel.org,
	Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 3/7] x86: Add C intrinsics for new rd/wr fs/gs base
 instructions

On Mon, Apr 28, 2014 at 03:12:37PM -0700, Andi Kleen wrote:
> From: Andi Kleen <ak@...ux.intel.com>
> 
> Plus for swapgs.
> 
> Very straight forward. Used in followon patch.

follow on
> 
> Signed-off-by: Andi Kleen <ak@...ux.intel.com>
> ---
>  arch/x86/include/asm/fsgs.h | 43 +++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 43 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..a3a5cd3
> --- /dev/null
> +++ b/arch/x86/include/asm/fsgs.h
> @@ -0,0 +1,43 @@
> +#ifndef _ASM_FSGS_H
> +#define _ASM_FSGS_H 1
> +
> +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");
> +}
> +
> +#endif
> -- 
> 1.9.0
> 
> --
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