linux-kernel - Re: [PATCH] x86: Use RDRAND and RDSEED mnemonics in archrandom.h

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Message-ID: <BACCC7C6-D456-4FAF-A11B-213995FE356A@zytor.com>
Date:   Fri, 08 May 2020 09:57:40 -0700
From:   hpa@...or.com
To:     Uros Bizjak <ubizjak@...il.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
CC:     Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] x86: Use RDRAND and RDSEED mnemonics in archrandom.h

On May 8, 2020 3:58:17 AM PDT, Uros Bizjak <ubizjak@...il.com> wrote:
>Current minimum required version of binutils is 2.23,
>which supports RDRAND and RDSEED instruction mnemonics.
>
>Replace the byte-wise specification of RDRAND and
>RDSEED with these proper mnemonics.
>
>Signed-off-by: Uros Bizjak <ubizjak@...il.com>
>CC: "H. Peter Anvin" <hpa@...or.com>
>CC: Ingo Molnar <mingo@...hat.com>
>CC: Thomas Gleixner <tglx@...utronix.de>
>---
> arch/x86/include/asm/archrandom.h | 26 ++++++++------------------
> 1 file changed, 8 insertions(+), 18 deletions(-)
>
>diff --git a/arch/x86/include/asm/archrandom.h
>b/arch/x86/include/asm/archrandom.h
>index 7a4bb1bd4bdb..ebc248e49549 100644
>--- a/arch/x86/include/asm/archrandom.h
>+++ b/arch/x86/include/asm/archrandom.h
>@@ -15,16 +15,6 @@
> 
> #define RDRAND_RETRY_LOOPS	10
> 
>-#define RDRAND_INT	".byte 0x0f,0xc7,0xf0"
>-#define RDSEED_INT	".byte 0x0f,0xc7,0xf8"
>-#ifdef CONFIG_X86_64
>-# define RDRAND_LONG	".byte 0x48,0x0f,0xc7,0xf0"
>-# define RDSEED_LONG	".byte 0x48,0x0f,0xc7,0xf8"
>-#else
>-# define RDRAND_LONG	RDRAND_INT
>-# define RDSEED_LONG	RDSEED_INT
>-#endif
>-
> /* Unconditional execution of RDRAND and RDSEED */
> 
> static inline bool __must_check rdrand_long(unsigned long *v)
>@@ -32,9 +22,9 @@ static inline bool __must_check rdrand_long(unsigned
>long *v)
> 	bool ok;
> 	unsigned int retry = RDRAND_RETRY_LOOPS;
> 	do {
>-		asm volatile(RDRAND_LONG
>+		asm volatile("rdrand %[out]"
> 			     CC_SET(c)
>-			     : CC_OUT(c) (ok), "=a" (*v));
>+			     : CC_OUT(c) (ok), [out] "=r" (*v));
> 		if (ok)
> 			return true;
> 	} while (--retry);
>@@ -46,9 +36,9 @@ static inline bool __must_check rdrand_int(unsigned
>int *v)
> 	bool ok;
> 	unsigned int retry = RDRAND_RETRY_LOOPS;
> 	do {
>-		asm volatile(RDRAND_INT
>+		asm volatile("rdrand %[out]"
> 			     CC_SET(c)
>-			     : CC_OUT(c) (ok), "=a" (*v));
>+			     : CC_OUT(c) (ok), [out] "=r" (*v));
> 		if (ok)
> 			return true;
> 	} while (--retry);
>@@ -58,18 +48,18 @@ static inline bool __must_check rdrand_int(unsigned
>int *v)
> static inline bool __must_check rdseed_long(unsigned long *v)
> {
> 	bool ok;
>-	asm volatile(RDSEED_LONG
>+	asm volatile("rdseed %[out]"
> 		     CC_SET(c)
>-		     : CC_OUT(c) (ok), "=a" (*v));
>+		     : CC_OUT(c) (ok), [out] "=r" (*v));
> 	return ok;
> }
> 
> static inline bool __must_check rdseed_int(unsigned int *v)
> {
> 	bool ok;
>-	asm volatile(RDSEED_INT
>+	asm volatile("rdseed %[out]"
> 		     CC_SET(c)
>-		     : CC_OUT(c) (ok), "=a" (*v));
>+		     : CC_OUT(c) (ok), [out] "=r" (*v));
> 	return ok;
> }
> 

Reviewed-by: H. Peter Anvin (Intel) <hpa@...or.com>
-- 
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