Re: Differences between FreeBSD and Linux system call mechanism

Andrej Presern (andrejp@luz.fe.uni-lj.si)
Fri, 4 Sep 1998 12:30:18 +0200

On Thu, 03 Sep 1998, Alexander Kjeldaas wrote:
>On Thu, Sep 03, 1998 at 02:47:10PM +0100, Alan Cox wrote:
>>
>> > 1) Linux system calls are done using software interrupt 0x80 on ia32.
>> > Does this qualify as a "call-gate based kernel entry"?
>>
>> No. Call gates are a paticular intel mechanism for jumping between rings
>> (priviledge levels). You can see an example of this in the iBCS2 handlers
>> since iBCS uses call gates. An int based call is faster, and sysenter
>> is potentially faster still but sysenter is only on some later PII chips
>>
>
>Doesn't this mean that it would be a good idea to let the kernel
>implement system calls by mapping a page into user-space containing
>the appropriate assembly instructions to most efficiently do the
>system calls?

Finally some sense.

Andrej

--
Andrej Presern, andrejp@luz.fe.uni-lj.si


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