linux-kernel - Re: [PATCH] x86: fux duplicated X86

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Date:	Fri, 17 Jun 2016 21:29:07 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Dave Hansen <dave@...1.net>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	X86 ML <x86@...nel.org>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	stable <stable@...r.kernel.org>
Subject: Re: [PATCH] x86: fux duplicated X86_BUG(9) macro

On Fri, Jun 17, 2016 at 5:15 PM, Dave Hansen <dave@...1.net> wrote:
>
> Now sending with actual stable@ address...
>
> --
>
> From: Dave Hansen <dave.hansen@...ux.intel.com>
>
> cpufeatures.h currently defines X86_BUG(9) twice on 32-bit:

Acked-by: Andy Lutomirski <luto@...nel.org> # who is suitably embarrassed

That being said, you or Ingo should consider fixing the typo in $SUBJECT.

>
>         #define X86_BUG_NULL_SEG        X86_BUG(9) /* Nulling a selector preserves the base */
>         ...
>         #ifdef CONFIG_X86_32
>         #define X86_BUG_ESPFIX          X86_BUG(9) /* "" IRET to 16-bit SS corrupts ESP/RSP high bits */
>         #endif
>
> I think what happened was that this added the X86_BUG_ESPFIX, but
> in an #ifdef below most of the bugs:
>
>         [58a5aac5] x86/entry/32: Introduce and use X86_BUG_ESPFIX instead of paravirt_enabled
>
> Then this came along and added X86_BUG_NULL_SEG, but collided
> with the earlier one that did the bug below the main block
> defining all the X86_BUG()s.
>
>         [7a5d6704] x86/cpu: Probe the behavior of nulling out a segment at boot time
>
> Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
> Cc: Andy Lutomirski <luto@...capital.net>
> Cc: stable@...r.kernel.org
> ---
>
>  b/arch/x86/include/asm/cpufeatures.h |    6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff -puN arch/x86/include/asm/cpufeatures.h~fix-x86-bugs-macros arch/x86/include/asm/cpufeatures.h
> --- a/arch/x86/include/asm/cpufeatures.h~fix-x86-bugs-macros    2016-06-17 17:10:30.978602807 -0700
> +++ b/arch/x86/include/asm/cpufeatures.h        2016-06-17 17:10:30.982602989 -0700
> @@ -301,10 +301,6 @@
>  #define X86_BUG_FXSAVE_LEAK    X86_BUG(6) /* FXSAVE leaks FOP/FIP/FOP */
>  #define X86_BUG_CLFLUSH_MONITOR        X86_BUG(7) /* AAI65, CLFLUSH required before MONITOR */
>  #define X86_BUG_SYSRET_SS_ATTRS        X86_BUG(8) /* SYSRET doesn't fix up SS attrs */
> -#define X86_BUG_NULL_SEG       X86_BUG(9) /* Nulling a selector preserves the base */
> -#define X86_BUG_SWAPGS_FENCE   X86_BUG(10) /* SWAPGS without input dep on GS */
> -
> -
>  #ifdef CONFIG_X86_32
>  /*
>   * 64-bit kernels don't use X86_BUG_ESPFIX.  Make the define conditional
> @@ -312,5 +308,7 @@
>   */
>  #define X86_BUG_ESPFIX         X86_BUG(9) /* "" IRET to 16-bit SS corrupts ESP/RSP high bits */
>  #endif
> +#define X86_BUG_NULL_SEG       X86_BUG(10) /* Nulling a selector preserves the base */
> +#define X86_BUG_SWAPGS_FENCE   X86_BUG(11) /* SWAPGS without input dep on GS */
>
>  #endif /* _ASM_X86_CPUFEATURES_H */
> _



-- 
Andy Lutomirski
AMA Capital Management, LLC