linux-kernel - Re: [x86 setup] Fix assembly constraints

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Message-ID: <4697FAC8.1010109@redhat.com>
Date:	Fri, 13 Jul 2007 18:20:56 -0400
From:	Chuck Ebbert <cebbert@...hat.com>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
	Etienne Lorrain <etienne_lorrain@...oo.fr>
Subject: Re: [x86 setup] Fix assembly constraints

On 07/13/2007 06:09 PM, H. Peter Anvin wrote:
> Fix incorrect assembly constraints.  In particular, fix memory
> constraints used inside push..pop, which can cause invalid operation
> since gcc may generate %esp-relative references.
> 
> Additionally:
> 
> outl() should have "dN" not "dn".
> 
> query_mca() shouldn't listen 16/32-bit registers in an 8-bit only
> context.
> 
> has_eflag(): the "mask" is only used well after both the stack pointer
> and the output registers have been touched; this requires the output
> registers to be earlyclobbers (=&) and the input to exclude memory (so
> "ri", not "g").
> 
> Thanks to Chuck Ebbert for prompting this review.
> 

That was Etienne Lorrain (cc'd), not me. All I did was reply
to Etienne's post and add cc:'s because the original only went
to linux-kernel.

> Cc: Chuck Ebbert <cebbert@...hat.com>
> Signed-off-by: H. Peter Anvin <hpa@...or.com>
> 
> diff --git a/arch/i386/boot/boot.h b/arch/i386/boot/boot.h
> index 0329c4f..dec70c9 100644
> --- a/arch/i386/boot/boot.h
> +++ b/arch/i386/boot/boot.h
> @@ -56,7 +56,7 @@ static inline u16 inw(u16 port)
>  
>  static inline void outl(u32 v, u16 port)
>  {
> -	asm volatile("outl %0,%1" : : "a" (v), "dn" (port));
> +	asm volatile("outl %0,%1" : : "a" (v), "dN" (port));
>  }
>  static inline u32 inl(u32 port)
>  {
> diff --git a/arch/i386/boot/cpucheck.c b/arch/i386/boot/cpucheck.c
> index 8b0f447..991e8ce 100644
> --- a/arch/i386/boot/cpucheck.c
> +++ b/arch/i386/boot/cpucheck.c
> @@ -115,8 +115,8 @@ static int has_eflag(u32 mask)
>  	    "pushfl ; "
>  	    "popl %1 ; "
>  	    "popfl"
> -	    : "=r" (f0), "=r" (f1)
> -	    : "g" (mask));
> +	    : "=&r" (f0), "=&r" (f1)
> +	    : "ri" (mask));
>  
>  	return !!((f0^f1) & mask);
>  }
> diff --git a/arch/i386/boot/mca.c b/arch/i386/boot/mca.c
> index 9b68bd1..68222f2 100644
> --- a/arch/i386/boot/mca.c
> +++ b/arch/i386/boot/mca.c
> @@ -26,7 +26,7 @@ int query_mca(void)
>  	    "setc %0 ; "
>  	    "movw %%es, %1 ; "
>  	    "popw %%es"
> -	    : "=acdSDm" (err), "=acdSDm" (es), "=b" (bx)
> +	    : "=acd" (err), "=acdSD" (es), "=b" (bx)
>  	    : "a" (0xc000));
>  
>  	if (err)
> diff --git a/arch/i386/boot/pm.c b/arch/i386/boot/pm.c
> index 3fa53e1..1df025c 100644
> --- a/arch/i386/boot/pm.c
> +++ b/arch/i386/boot/pm.c
> @@ -65,7 +65,7 @@ static void move_kernel_around(void)
>  			     "popw %%ds ; "
>  			     "popw %%es"
>  			     : "+c" (dwords)
> -			     : "rm" (dst_seg), "rm" (src_seg)
> +			     : "r" (dst_seg), "r" (src_seg)
>  			     : "esi", "edi");
>  
>  		syssize -= paras;
> diff --git a/arch/i386/boot/video.c b/arch/i386/boot/video.c
> index 3bb3573..027a2c9 100644
> --- a/arch/i386/boot/video.c
> +++ b/arch/i386/boot/video.c
> @@ -411,7 +411,7 @@ static void restore_screen(void)
>  			     "1: rep;stosl ; "
>  			     "popw %%es"
>  			     : "+D" (dst), "+c" (npad)
> -			     : "bdSm" (video_segment),
> +			     : "bdS" (video_segment),
>  			       "a" (0x07200720));
>  	}
>  
> diff --git a/arch/i386/boot/voyager.c b/arch/i386/boot/voyager.c
> index 9221614..61c8fe0 100644
> --- a/arch/i386/boot/voyager.c
> +++ b/arch/i386/boot/voyager.c
> @@ -32,7 +32,7 @@ int query_voyager(void)
>  	    "setc %0 ; "
>  	    "movw %%es, %1 ; "
>  	    "popw %%es"
> -	    : "=qm" (err), "=rm" (es), "=D" (di)
> +	    : "=q" (err), "=r" (es), "=D" (di)
>  	    : "a" (0xffc0));
>  
>  	if (err)
> 

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