svn commit: r267651 - in head: share/man/man4 sys/dev/cpuctl sys/sys usr.sbin/cpucontrol

[Julian Elischer]

On 6/20/14, 2:12 PM, Attilio Rao wrote:
> On Fri, Jun 20, 2014 at 6:08 AM, Konstantin Belousov
> <kostikbel at gmail.com> wrote:
>> On Thu, Jun 19, 2014 at 09:54:41PM +0000, Attilio Rao wrote:
>>> Author: attilio
>>> Date: Thu Jun 19 21:54:41 2014
>>> New Revision: 267651
>>> URL: http://svnweb.freebsd.org/changeset/base/267651
>>>
>>> Log:
>>>    Following comments in r242565 add the possibility to specify ecx when
>>>    performing cpuid calls.
>>>    Add also a new way to specify the level type to cpucontrol(8) as
>>>    reported in the manpage.
>>>
>>>    Sponsored by:       EMC / Isilon storage division
>>>    Reviewed by:        bdrewery, gcooper
>>>    Testerd by: bdrewery
>>> Modified: head/sys/sys/cpuctl.h
>>> ==============================================================================
>>> --- head/sys/sys/cpuctl.h     Thu Jun 19 21:05:07 2014        (r267650)
>>> +++ head/sys/sys/cpuctl.h     Thu Jun 19 21:54:41 2014        (r267651)
>>> @@ -35,7 +35,8 @@ typedef struct {
>>>   } cpuctl_msr_args_t;
>>>
>>>   typedef struct {
>>> -     int             level;  /* CPUID level */
>>> +     int             level;          /* CPUID level */
>>> +     int             level_type;     /* CPUID level type */
>>>        uint32_t        data[4];
>>>   } cpuctl_cpuid_args_t;
>>>
>>> @@ -50,5 +51,6 @@ typedef struct {
>>>   #define      CPUCTL_UPDATE   _IOWR('c', 4, cpuctl_update_args_t)
>>>   #define      CPUCTL_MSRSBIT  _IOWR('c', 5, cpuctl_msr_args_t)
>>>   #define      CPUCTL_MSRCBIT  _IOWR('c', 6, cpuctl_msr_args_t)
>>> +#define      CPUCTL_CPUID_COUNT _IOWR('c', 7, cpuctl_cpuid_args_t)
>>>
>>>   #endif /* _CPUCTL_H_ */
>> The cpuctl(4) is used by third-party code, and this change breaks its
>> ABI. The numeric value for CPUCTL_CPUID is changed, which means that
>> old binaries call non-existing ioctl now. This is at least a visible
>> breakage, since the argument for the ioctl changed the layout as well.
>>
>> The following patch restored the CPUCTL_CPUID for me.  I considered
>> naming its argument differently, instead of renaming the argument
>> of CPUCTL_CPUID_COUNT (which you tried to do ?), but decided not,
>> to preserve the API as well.
> No, breaking the ABI is fine for -CURRENT so I don't see why we need the bloat.
> I don't plan on MFC this patch. If I need to (or any user requests
> that) I will do with the appropriate ABI-compliant way (ie. adding a
> new argument like this one).
breaking the ABI is not  fine.
we have backwards compatibility. If you break a user facing ABI you 
need to have a compatibility plan.  A newer kernel should always do 
its best to run old binaries.


>
> Attilio
>
>