Patchwork [v2] x86: make DR*_RESERVED unsigned long

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Submitter Oleg Nesterov
Date April 28, 2013, 5:27 p.m.
Message ID <20130428172731.GA26169@redhat.com>
Download mbox | patch
Permalink /patch/240266/
State Not Applicable
Headers show

Comments

Oleg Nesterov - April 28, 2013, 5:27 p.m.
On 04/28, Frederic Weisbecker wrote:
>
> On Sat, Apr 27, 2013 at 04:45:37PM +0200, Oleg Nesterov wrote:
> >
> > -/* Define reserved bits in DR6 which are always set to 1 */
> > -#define DR6_RESERVED	(0xFFFF0FF0)
> > +#define DR6_MASK	(0xF00FU)	/* Everything else is reserved */
>
> I'm personally fine either with that or with Peter's suggestion to do:
>
> -#define DR6_RESERVED (0xFFFF0FF0)
> +#define DR6_RESERVED (~0xF00FUL)

I missed this suggestion...

Yes, and this allows to kill ifdef too.

> If this should stay stable UAPI,

I do not know, but I guess it would be safer to keep the old define's.

> I really don't mind.

Oh, I do not mind too ;)

OK, please see v3.

------------------------------------------------------------------------------
Subject: [PATCH v3] x86: make DR*_RESERVED unsigned long

DR6_RESERVED and DR_CONTROL_RESERVED are used to clear the unwanted
bits in the "unsigned long" data, but "ulong &= ~int" also clears the
upper bits that are not specified in mask.

This is actually fine, dr6[32:63] are reserved, but this is not clear
so it would be better to make them "unsigned long" to cleanup the code.

However, depending on sizeof(long), DR6_RESERVED should be either
0xFFFF0FF0 or 0xFFFFFFFF_FFFF0FF0, so this patch redefines them as
(~ 32_bit_mask UL) to avoid ifdef's.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Suggested-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
 arch/x86/include/uapi/asm/debugreg.h |    8 ++------
 1 files changed, 2 insertions(+), 6 deletions(-)
H. Peter Anvin - April 28, 2013, 5:32 p.m.
On 04/28/2013 10:27 AM, Oleg Nesterov wrote:
> On 04/28, Frederic Weisbecker wrote:
>>
>> On Sat, Apr 27, 2013 at 04:45:37PM +0200, Oleg Nesterov wrote:
>>>
>>> -/* Define reserved bits in DR6 which are always set to 1 */
>>> -#define DR6_RESERVED	(0xFFFF0FF0)
>>> +#define DR6_MASK	(0xF00FU)	/* Everything else is reserved */
>>
>> I'm personally fine either with that or with Peter's suggestion to do:
>>
>> -#define DR6_RESERVED (0xFFFF0FF0)
>> +#define DR6_RESERVED (~0xF00FUL)
> 
> I missed this suggestion...
> 
> Yes, and this allows to kill ifdef too.
> 
>> If this should stay stable UAPI,
> 
> I do not know, but I guess it would be safer to keep the old define's.
> 
>> I really don't mind.
> 
> Oh, I do not mind too ;)
> 
> OK, please see v3.
> 

Looks good.  However, given the timing, I would think this is 3.11
material unless we have a manifest bug at this point.

I have several bits like this that I'm going to queue up in a separate
tip branch.

	-hpa


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Oleg Nesterov - April 28, 2013, 5:39 p.m.
On 04/28, H. Peter Anvin wrote:
>
> On 04/28/2013 10:27 AM, Oleg Nesterov wrote:
>
> Looks good.  However, given the timing, I would think this is 3.11
> material unless we have a manifest bug at this point.

Yes, yes, this is only cleanup.

> I have several bits like this that I'm going to queue up in a separate
> tip branch.

Great, thanks.

Oleg.

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H. Peter Anvin - April 28, 2013, 5:43 p.m.
On 04/28/2013 10:39 AM, Oleg Nesterov wrote:
> On 04/28, H. Peter Anvin wrote:
>>
>> On 04/28/2013 10:27 AM, Oleg Nesterov wrote:
>>
>> Looks good.  However, given the timing, I would think this is 3.11
>> material unless we have a manifest bug at this point.
> 
> Yes, yes, this is only cleanup.
> 

Thanks for tackling it.  I just wanted to make sure you didn't wonder
why I didn't want to push it for 3.10.

	-hpa

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Patch

diff --git a/arch/x86/include/uapi/asm/debugreg.h b/arch/x86/include/uapi/asm/debugreg.h
index 3c0874d..4ff5d05 100644
--- a/arch/x86/include/uapi/asm/debugreg.h
+++ b/arch/x86/include/uapi/asm/debugreg.h
@@ -15,7 +15,7 @@ 
    are either reserved or not of interest to us. */
 
 /* Define reserved bits in DR6 which are always set to 1 */
-#define DR6_RESERVED	(0xFFFF0FF0)
+#define DR6_RESERVED	(~0xF00FUL)
 
 #define DR_TRAP0	(0x1)		/* db0 */
 #define DR_TRAP1	(0x2)		/* db1 */
@@ -64,11 +64,7 @@ 
    We can slow the instruction pipeline for instructions coming via the
    gdt or the ldt if we want to.  I am not sure why this is an advantage */
 
-#ifdef __i386__
-#define DR_CONTROL_RESERVED (0xFC00) /* Reserved by Intel */
-#else
-#define DR_CONTROL_RESERVED (0xFFFFFFFF0000FC00UL) /* Reserved */
-#endif
+#define DR_CONTROL_RESERVED (~0xFFFF03FFUL) /* Reserved by Intel */
 
 #define DR_LOCAL_SLOWDOWN (0x100)   /* Local slow the pipeline */
 #define DR_GLOBAL_SLOWDOWN (0x200)  /* Global slow the pipeline */