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Re: X32 psABI status
On Sun, Feb 13, 2011 at 3:39 PM, Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
>> a. the int $0x80 instruction is much slower than syscall. ?An actual
>> ? ?i386 process can use the syscall instruction which is disambiguated
>> ? ?by the CPU based on mode, but an x32 process is in the same CPU mode
>> ? ?as a normal 64-bit process.
>
> So set a flag, whoopee
>
>> b. 64-bit arguments have to be split between two registers for the
>> ? ?i386 entry points, requiring user-space stubs.
>
> Diddums. Given you've yet to explain why everyone desperately needs this
> extra interface why do we care ?
>
>> All in all, the cost of an extra system call table is quite modest.
>
> And the cost of not doing it is a gloriously wonderful zero. Yo've still
> not explained the justification or what large number of apps are going to
> use it.
>
> It's a simple question - why do we care, why do we want the overhead and
> the hassle, what do users get in return ?
>
The real question is if we need to use ia32. If the answer is yes, then
x32 provides the benefit of ia32 with register extended to 64bit plus 8
more registers as well as IP relative address.
--
H.J.