RE: [Xen-ia64-devel] RE: [PATCH]: disable handling of legacyprivified insns

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

>From: Magenheimer, Dan (HP Labs Fort Collins)
>Sent: 2006年3月21日 0:09
>
>> The Linux kernel doesn't use the break instructions for
>> itself, does it ?
>
>I don't know about current kernels, but certainly in past
>Linux/ia64 kernels, Linux uses break instructions.  If I
>recall correctly, launching a kernel thread required a
>pl0 system call via a break instruction.

Latest code has no that 'break' for kernel thread creation.

>
>> So, if I am correct the linux kernel could use break insns
>> without ic=0/ic=1
>> for hyperprivops.
>>
>> I really think this could work for linux.
>> What about other OS ?  I don't see why they would use break
>> in kernel mode.
>> The only exception may be debugger/single stepping.
>
>I agree a kernel debugger might use break instructions
>with pl=0.

Yes current linux kernel definitely uses 'break', like kdb, kprobe, jprobe, 
etc. See include/asm-ia64/break.h.

Thanks,
Kevin

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